Download 1. Vertebral Column and Spinal Cord

LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 1. Vertebral Column and Spinal Cord 1. Recognize and name the following parts of a typical vertebra in oesteological spcimens or in suitable imagine: body, pedicle, lamina, transverse process, spinous process, articular surfaces Spinous Process
Lamina
Superior Articular Facet
Transverse Processes
Pedicle
Spinal Canal
Vertebral Body
2. Recognize the distinctive features of cervical, thoracic and lumbar vertebrae Type of Distinctive features vertebrae Cervical (7) A triangular vertebral foramen Vertebral body is short in height and square shaped A foramen in each transverse process for arteries and veins A bifid (two-­‐pronged) spinous process, except C1 and C7 The atlas and axis (C1 and C2) are specialised for movement Thoracic (12) Larger and stronger Facets for rib articulation (inferior and superior costal facets, and transverse costal facet) A spinous process orientated in a marked inferior fashion Vertebral foramen circular Vertebral body is somewhat heart-­‐shaped from above Lumbar (5) Identifiable by their large size, particular of the body Have rounded upper and lower facets to prevent rotation Thin, long transverse processes (except LV) Vertebral body is cylindrical Vertebral foramen is triangular in shape Sacral (5 Sacral vertebrae are fused to form the sacrum fused) Triangular in shape Concave anterior surface L shaped facets – articulation with pelvic bones Coccyx (3-­‐4 Absence of vertebral arches and canal fused) LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 3. Explain the roles of intervertebral discs, ligaments and muscles in load bearing in the vertebral column Joints • The 2 major types of joints between vertebrae are: o Symphyses between vertebral bodies o Synovial joints between articular processes • A typical vertebrae has a total of 6 joints with adjacent vertebrae: 4 synovial (2 above, 2 below), and 2 symphyses (1 above, 1 below) • In between each vertebrae (C2-­‐S1) are intervertebral discs which consist of: o Annulus fibrosis – outer ring of collagen surrounded by fibrocartilage arranged in a lamellar configuration; role is to limit rotation o Nucleus pulposus – soft gelatinous core (probably derived from remnants of notochord); role is to absorb compressive forces between vertebrae • Degenerative changes in the annulus fibrosis can lead to herniation of the nucleus pulposus o Posterolateral herniation can impinge on the roots of the spinal nerves in the intervertebral foramen > sensory deficits or pain • There is no intervertebral discs between the base of the skull and C1, or between C1 and C2, due to specialized movements which occur here • The synovial joints between superior and inferior articular processes on adjacent vertebrae are known as zygapophysial joints o In cervical region, these slope inferiorly from anterior to posterior; this facilitates flexion and extension o In thoracic region, these are orientated vertically which limits flexion and extension, facilitating rotation o In the lumbar regions, the joint surfaces are curved and adjacent processes interlock; this limits movement • The summated movements between all vertebrae results in a large range of movements by the vertebral column, including flexion, extension, lateral flexion, and circumduction Ligaments Joints between vertebrae are reinforced and supported by numerous ligaments, which pass between vertebral bodies and interconnect components of the vertebral arches • Anterior longitudinal ligament – attached superiorly to base of skull and extends along the anterior surface of the vertebral bodies and intervertebral discs to the anterior surface of the sacrum o This is commonly damaged in whiplash • Posterior longitudinal ligament – attached superiorly to base of skull and extends along the posterior surface of the vertebral bodies and intervertebral discs to the posterior surface of the sacrum (lining the anterior surface of the vertebral canal o The upper part that connects C2 to the base of the skull is termed the tectorial membrane • Ligamentum flava – pass between the laminae of adjacent vertebrae; running superiorly from posterior to anterior, forming part of the posterior surface of the vertebral canal o Predominantly elastic tissue o Resists separation of the laminae in flexion + assist in extension that returns to anatomical position o Pierced during lumbar puncture • Ligamentum nuchae – triangular, sheet-­‐like structure that forms the upper part of the supraspinous ligament, attaching from vertebrae C7 to the skull o Supports the heard o Resists flexion and facilitates returning head to anatomical position o Broad lateral surfaces provide muscle attachment sites • Supraspinous ligaments passes along and connects the tips of the spinous processes from vertebrae CVII to the sacrum LCRS Anatomy of the Head, Neck & Spine •
Alexandra Burke-­‐Smith Interspinous ligaments pass between adjacent vertebral spinous processes; attach from the base to the apex of each spinous process o blend with the supraspinous ligament posteriorly o blend with the ligament flava anteriorly on each side Muscles of the back are organized into superficial, intermediate and deep groups: • The superficial group consists of muscles related to and involved in movements of upper limb • The intermediate group consists of muscles attached to the ribs (may serve as a respiratory function) • The deep group consists of muscles innervated by the posterior spinal rami and are directly related to movements of the vertebral column and head Superficial muscles Include the trapezius, lattisimus dorsi, rhomboid major, rhomboid minor, and levator scapulae Muscle Origin Insertion Function Trapezius Cervical + thoracic spine Clavicle + scapula Elevate + rotate scapula during abduction of humerus (when raising arm above head) Latissimus dorsi T7 – sacrum + iliac crest Intertubercular sulcus Extends, adducts and of humerus medially rotates humerus Levator scapulae Transverse processes of Upper medial scapula Elevates scapula C1-­‐C4 Rhomboid major Spinous processes of Medial border of Adducts (retracts) + T2-­‐T5 scapula elevates scapula Rhomboid minor Cervical spine Medial border of Adducts (retracts) + scapula elevates scapula LCRS Anatomy of the Head, Neck & Spine Intermediate muscles Muscle Origin Serratus posterior C1 – T3 superior Serratus posterior T11-­‐L3 inferior Alexandra Burke-­‐Smith Insertion Function Upper border of ribs 2-­‐5 Elevates ribs 2-­‐5 Anterior rami of lower thoracic nerves (T9-­‐12) Depresses ribs 9-­‐12 Prevents lower limbs from elevating when the diaphragm contracts Deep muscles The deep or intrinsic muscles of the back extend from the pelvis to the skull and are innervated by segmental branches of the posterior rami of spinal nerves. They include: • Extensors and rotators of the head and neck – the spinotransversales o The 2 spinotransversales muscles run from the spinous process and ligamentum nuchae from T6, running superiorly and laterally • Extensors and rotators of the vertebral column – the erector spinae and traversospinales o The erector spinae is the largest group of intrinsic back muscles; they lie posterolaterally to the vertebral column between the spinous processes medially and the angles of the ribs laterally o The transversospinales muscles run obliquely upward and medially from transverse process to spinous process (filling groove between) • Short segmental muscles = the stabilisers of the vertebral column – the interspinales + intertransversarii o The interspnales pass between adjacent spinous processes o The intertransversarri pass between adjacent tranverse processes 4. Describe the relative extensors of antero-­‐posterior flexion, lateral flexion, axial rotation and extension in the major regions of the vertebral column and explain this in terms of skeletal anatomy C1-­‐C7 T1-­‐T6 T7-­‐T12 L1-­‐sacrum Flexion/extension ++ 0 + ++ Lateral flexion ++ + ++ + Rotation ++ + ++ 0 •
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The cervical spine is the most flexible part of the spine. The reasons for this are: o The articular surfaces between the vertebrae are almost horizontal, therefore rotation is possible o The neck has less surrounding tissue than the rest of the back, therefore there is less resistance to flexion and extension The thoracic spine movement is determined by the intervertebral joints: o These are almost vertical, therefore this reduces AP flexion/extension, but allows for lateral flexion and rotation The lumbar spine has large intervertebral discs which lie directly behind the intervertebral foramen (arranges sagitally). Their articular surfaces are curled around the articular surfaces of the adjacent superior vertebrae, ensuring no rotation 5. Identify “atlas” and “axis” and explain their functions in head movement Atlas = C1 • Lacks a vertebral body • Ring-­‐shaped, 2 lateral masses interconnected by an anterior + posterior arch LCRS Anatomy of the Head, Neck & Spine •
Alexandra Burke-­‐Smith Each lateral mass articulates superiorly with an occipital condyle of the skull, and inferiorly wit the superior articular surfaces of C2 (atlas) The atlanto-­‐occipital joint (lies behind the mouth) allows the head to nod •
Axis = C2 • This is a typical cervical vertebrae with the body extended upwards to form the dens (tooth) process • The posterior surface of the anterior arch has an articular facet for the dens, which projects superiorly from axis. o This is held in position by the transverse ligament of atlas o This acts as a pivot that allows atlas (and attached head) to rotate on axis • The two superolateral surfaces of the dens possess articular impressions that serve as attachment sites for strong alar ligaments, which connect to the medial occipital condyles and check excessive rotation of the head 6. Demonstrate on each other the location of C7, T3, T7, L2 and L4 vertebrae •
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C7 – only cervical vertebrae with a prominent spinous process (First palpable vertebra) T3 – at level of the medial end of the scapular spine T7 – at level of the inferior angle of the scapula L2 – level of lowest rib L4 – Level of the iliac crest 7. State the number of vertebrae in each region of the spine, and how the pairs of spinal nerves are related to them Part of spine Number of vertebrae Number of spinal Relationship of nerve nerves to vertebra Cervical 7 8 Above and below Thoracic 12 12 Below Lumbar 5 5 Below Sacral 5 (fused) 5 Below LCRS Anatomy of the Head, Neck & Spine Coccyx 1-­‐4 (fused) Alexandra Burke-­‐Smith 1 Below (or between if unfused) Total 30-­‐33 31 8. Explain the arrangement of the meninges around the spinal cord and roots The spinal cord is surrounded by the meninges; these are continuous with the meninges of the brain. • The spinal dura mater is the tough and fibrous outermost meningeal is the outermost meningeal membrane and is separated from the bones forming a vertebral canal by epi/extradural space. This contains connective tissue, fat and the internal vertebral venous plexus o Superiorly it is continuous with the inner meningeal layer of the cranial dura mater at the foramen magnum o Inferiorly, the dural sac dramatically narrows at the level of the lower border of S2 and forms an investing sheath for the final pat of the filum terminale of the spinal cord § This attaches to the posterior surface of the vertebral bodies of the coccyx o As spinal nerves and their roots pass laterally, they are surrounded by tubular sleeves of dura mater, which merge with the epineurium • The arachnoid mater is a thin, delicate membrane against, but not adherent to, the deep surface of the dura mater. o It is separated from the pia mater by the subarachnoid space, and ends at the vertebral level S2 • The subarachnoid space contains the CSF. o Arachnoid trabecular interconnect the arachnoid and pia mater, and suspend blood vessels within the subarachnoid space o The subarachnoid space extends further inferiorly than the spinal cord (Ends at approx. L1/2), ending at approximately S2 o The subarachnoid space is largest in the region inferior to the terminal end of the spinal cord where it surrounds the cauda equina. As a consewuence, CSF can be withdrawn here without endangering the spinal cord. • The spinal pia mater is a vascular membrane that firmly adheres to the surface of the spinal cord. o On each side of the spinal cord, a longitudinal oriented sheet of pia mater (denticulate ligament) externs laterally from the cord toward the arachnoid and dura mater § Medially, denticulate ligaments attach to the spinal cord § Laterally, each denticulate ligament forms a series of triangular extensions that anchor through the arachnoid mater to the dura mater § They generally occur between the exit points of adjacent posterior and anterior rootlets and position • The difference between spinal and cranial meninges is that there is no epidural (extradural) space in the cranium as the cranial dura mater is firmly adherent to the skull except at certain sites where they part to form the venous sinuses 9. Identify two major regions for carrying out lumbar puncture, and explain the basis for the puncture site • Reasons for carrying out lumbar puncture: to obtain a sample of CSF for examination (e.g. suspected meningitis) and for spinal anaesthesia (agent injected into subarachnoid space) o Epidural anaesthesia – a liquid agent can be injected into the epidural space to anaesthetise the spinal nerve roots • Below vertebral level L2/L4, and up to S2, the canal is only occupied by CSF and the cauda equine. This means the needles can be inserted without risk of damage to spinal cord LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith •
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A needle passes through the skin, slightly off centre → through the ligamentum flavum (a give is felt) between the adjacent vertebral laminae → the tip of the needle is in the epidural space → pierces the dura and arachnoid together (another pop/give) into the subarachnoid space→ CSF should pass out Carried out between L3/L4 (adult), which is the level with the iliac crest. In a child it is performed one or two vertebral spaces lower Procedure: needle passed through skin just lateral to midline, through the ligamentum flavum (this is when a “give” is felt), between of the adjacent vertebral lamina to the epidural space. The needle then pierces the dura and arachnoid mater together (another pop/give is felt), and enters the subarachnoid space. CSF can then be obtained. 10. Explain the danger of carrying out a lumbar puncture without excluding the presence of raised intracranial pressure If there is raised intracranial pressure, and a lumbar puncture is carried out, the sudden release of CSF could cause the brainstem to herniate through the foramen magnum into the vertebral. This is potentially fatal 11. Outline the steps taken to avoid neurological complication in casualties with a possibility of cervical spine injury. Signs of cervical spine injury: • Low BP with bradycardia – loss of sympathetic tone, vasodilation • Large erection – Custer’s last stand • Flaccid paralysis • Large bladder with inability to micturate On scene management • Assume unstable fracture • Assume neck pain if patient cannot express feeling of neck pain • Use cervical collar + blocks to immobilize neck – only remove when C-­‐spine is clear In hospital management Aim is to reduce further damage • Take lateral and AP C Spine – if fracture image with CT/MRI • Give steroids – probably prevent the death of around 1cm of spinal cord – could be the difference between being independent or not in the cervical region • Treat any other symptoms e.g. low BP 12. Explain in anatomical terms the most common causes of back pain The lower spine is subject to increased stresses of weight-­‐bearing and so the lumbar region is most commonly affected • We tend to abuse our backs, particularly when lifting heavy objects. • Extending the spine from the fully flexed position under a heavy load can inflame intervertebral joints or place unequal pressure on the intervertebral disks, leading to local joint pain and referred neurological pain, if there is also pressure on the spinal nerve • Additional attempts to rotate the spine at the same time creates extra stress on the lumbar joints. 13. Describe the most common abnormalities of spinal curvature • Scoliosis – lateral deviation of the vertebral column • Kyphosis – excess thoracic curvature, “hump back” • Lordosis – excess lumbar curvature, e.g. due to obesity LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 2. Cranium and Brain 1. Demonstrate on a skull and in radiographs the following bones: frontal, parietal, temporal (squamous, petrous and mastoid process), ethmoid, sphenoid (body and wings) and occipital The bones of the skull can be divided into those of the cranium, and the facial skeleton. Cranium Frontal, parietal (x2), occipital, temporal (x2), sphenoid, ethmoid Facial skeleton Maxilla (x2), zygoma (x2), nasal (x2), lacrimal (x2), vomer, inferior conchae (x2), palatine (x2), mandible Frontal Bone
Parietal Bone
Sphenoid Bone
(wing)
Occipital Bone
Nasal Bone
Zygoma
Temporal Bone
Mastoid Process
Maxilla
Styloid Process
Mandible
Anterior Cranial Fossa
Ethmoid bone (cribriform plate)
Lesser wing of sphenoid
Greater wing of sphenoid
Middle Cranial Fossa
Petrous of Temporal Bone
Foramen Magnum
Posterior Cranial Fossa
LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 2. Identify both on the brain an in x-­‐ray, CT, and MRI images the following: ventricles, cerebral hemispheres, thalamus, hypothalamus, internal capsule, basal ganglia, brainstem, optic chiasm and pituitary gland Axial Plane (looking from above) Coronal Plane (posterior view) LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith Mid-­‐saggital plane (lateral view: anterior – posterior) 1 Lateral ventricle [may be cut through twice in horizontal or coronal plane] 2 Third ventricle [may look like a hole or a slit in coronal and horizontal plane, depending on angle of section] 3 Fourth ventricle 4 Aqueduct 5 Corpus callosum [may be cut through twice in horizontal plane] 6 Frontal lobe 7 Occipital lobe 8 Parietal lobe 9 Temporal lobe 10 Basal ganglia [may be more than one part] 11 Thalamus 12 Internal capsule [both anterior and posterior limbs seen in horizontal plane] 13 Optic chiasma 14 Midbrain 15 Pons 16 Medulla 17 Cerebellum 3. Identify the different tissue components of the scalp S = skin: most superficial, highly vascular; contains many sweat glands, sebaceous glands and hair follicles C = connective tissue : supplied by cutaneous nerves; highly vascular A = aponeurosis (epicranial aponeurosis); membranous sheet/tendon of the epicranius muscles L = loose connective tissue: not continuous with pericranium, allow movement of the scalp P = pericranium: dense layer of connective tissue continuous with the endocranium NB: emissary vessels go through the skull from the scalp to the cranial cavity, therefore it is important not to get infections of the scalp (caused by injury) as this may spread to the brain LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 4. Demonstrate the relationship between the brain and different cranial fossa •
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Anterior cranial fossa – frontal lobe Middle cranial fossa – temporal lobes Posterior cranial fossa – cerebellum (+ brainstem) 5. Describe the structure and function of the meninges There are 3 layers of meninges which surround the brain within the cranial cavity. These include: • Dura mater (outer layer) – this adheres to the inside of the cranial cavity • Arachnoid mater (middle layer) • Pie mater (inner layer) – this adheres to the surface of the brain The dura mater in fact can be considered to have two layers, the outer layer adheres to the inside of the cranium, and the inner layer forms double folds which divide the cranial cavity into compartments; this stabilizes the brain within the cranium • The falx cerebri separates the 2 cerebral hemispheres o This is attached anteriorly to the ethmoid bone and frontal bone, and posteriorly it blends with the tentorium cerebelli • The tentorium cerebelli separates the cerebellum from the cerebrum (occipital, parietal + frontal lobes) o This is a horizontal projection attached posteriorly to the occipital bone, laterally to the superior border of the temporal bone and ending anteriorly at the clinoid processes o The anterior and medial borders of the tentorium cerebelli are free; they form an oval opening in the midline = the tentorial notch (through which midbrain passes) 6. Draw a simple diagram to explain the flow of cerebrospinal fluid in and around the brain The subarachnoid space (between pia + arachnoid mater) surrounds the brain and spinal cord, and in certain locations it enlarges into expanded areas called subarachnoid cisterns. • It contains cerebrospinal fluid and blood vessels. • CSF is produced by the choroid plexus (formed where the vessels of pia mater come into contact with the ependymal lining of the central canal) • CSF then flows through the ventricles: lateral ventricles > third ventricle > aqueduct > fourth ventricle > central canal (very little actually flows into the central canal, most enters the subarachnoid space) • From the subarachnoid space, CSF flows around the brain and then returns to the venous system through arachnoid villi (which project as arachnoid granulations into the superior saggital sinus = dural venous sinus) into the venous system NB: hydrocephalus is a dilatation of the cerebral ventricular system, which is due to either an obstruction to the flow of CSF, overproduction of CSF or a failure of reabsorption of CSF. LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 7. Explain the term herniation with respect to the brain and give examples of its neurological consequences A space occupying lesion (for example blood, tumour, oedema, cyst) in any compartment may raise intracranial pressure and lead to herniation of part of the brain. This is when the brain shifts across structures within the skull. Examples of herniation include: • Subfalcine herniation = most common type; occurs when the innermost part of the frontal lobe shifts under part of the falx cerebri. This does not put much pressure on the brainstem, but may interfere with blood vessels in the frontal lobe • Uncal herniation: the innermost part of the temporal lobe shifts the tentorium and puts pressure on the brainstem, squeezing the midbrain. This usually presents with unconsciousness • Tonsillar herniation: the cerebellar tonsils move downward through the foramen magnum possible causing compression of the lower brainstem and upper cervical spine cord. This may present with cardiorespiratory failure 8. Draw a simple diagram of the Circle of Willis (See NMH lecture 4 for more detail) The brain receives its arterial supply from two pairs of vessels; the vertebral and internal carotid arteries, which are interconnected in the cranial cavity to produce a cerebral arterial circle of Willis • The two vertebral arteries enter the cranial cavity through the foramen magnum and just inferior to the pons fuse to form the basilar artery • The two internal carotid arteries enter the cranial cavity through the carotid canals on either side LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 9. Demonstrate the main venous sinuses Venous drainage of the brain begins internally as networks of small venous channels leading to larger cerebral veins, cerebellar veins, and veins drainage the brain stem, which eventually drain into dural venous sinuses • The dural venous sinuses are endothelial-­‐lined spaces between the outer periosteal and inner meningeal layers of the dura mater, and eventually these lead to the internal jugular veins • The superior saggital sinus is in the superior border of the falx cerebri. It receives cerebral veins from the superior surface of the cerebral hemispheres, diploic and emissary veins, and veins from the falx cerebri o Blood in the SSS drains posteriorly, and at the internal occipital protuberance turns fight, forming the right transverse sinus. o As the right transverse sinus passes the petrous temporal bone, it turns into the sigmoid sinus •
The inferior saggital sinus is in the inferior margin of the falx cerebri. o At the anterior edge of the edge of the tentorium cerebelli, it is joined by the great cerebral vein to form the straight sinus o The straight sinus drains posteriorly, turning left at the internal occipital protuberance becoming the left transverse sinus § The left transverse sinus is not always present o The straight sinus receives blood from the inferior saggital sinus, cerebral veins (from posterior part of the cerebral hemispheres_, the great cerebral vein (draining the deep cerebral hemispheres), superior cerebellar veins and veins from the falx cerebri •
The superior saggital, straight sinuses, and the occipital sinus (in falx cerebelli) empty into the confluence of sinuses, which is a dilated space at the internal occipital protuberance o This is drained by the right and left transverse sinuses •
The paired transverse sinuses extend in horizontal directions from the confluence of sinuses. As they leave the surface of the occipital bone, they become the sigmoid sinuses which turn inferiorly, grooving the parietal, temporal and occipital bones o The sigmoid sinuses end at the beginning of the internal jugular veins •
The paired cavernosus sinuses are against the lateral aspect of the body of the sphenoid bone. They receive blood not only from the cerebral veins, but also from ophthalmic veins and emissary veins o The right and left cavernosus sinus lie either side of the pituitary fossa, and communicate with the transverse sinuses and internal jugulars via petrosal sinuses LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 10. Outline how venous anatomy presents opportunities for intracranial infections Also emptying into the dural venous sinuses are diploic veins, which run between the internal and external tables of compact bone in the roof of the cranial cavity, and emissary veins, which pass from outside the cranial cavity to dural venous sinuses •
The emissary veins are important clinically because they can be a conduit through which infections can enter the cranial cavity because they have no valves The connections of the cavernosus sinuses (see above) provide pathways for infections to pass from extracranial to intracranial locations •
The facial vein makes a connection with the cavernosus sinus, therefore providing a pathway for infection from the face to the brain •
Patients with thrombophlebitis of the facial vein (inflammation of the facial vein with secondary thrombus formation) -­‐ pieces of an infected clot may extend into the intracranial venous system; producing thrombophlebitis of the cavernous sinus 11. Identify the pterion and explain the clinical importance of its relationship to the middle meningeal artery The pterion is the point at which the frontal, parietal, temporal and sphenoid bones meet on the lateral aspect of the skull •
This is the thinnest and weakest part of the skull •
This can be surface marked about 4cm above the point that lies between 1/3 of the way from the ear to the eye •
The anterior division of the middle meningeal artery runs deep the pterion, therefore injury at this site can easily tear the artery causing an extradural haemorrhage •
Severe injury can also affect the deeper branches of the MCA, causing a subarachnoid haemorrhage LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 12. Identify on a skull the main exit/entry routes for the cranial nerves and the major blood vessels Cribiform Plate
Optic Canal
Olfactory (I) Nerve Fibres
Optic Nerve (II) including (central artery of
retina)
Opthlamic Artery
Oculomotor Nerve (III)
Trochlear Nerve (IV)
Superior Orbital
Opthalmic division of Trigeminal (V)
Fissure
Abducens Nerve (VI)
Superior Opthalmic Vein
Foramen Rotundum
Foramen Ovale
Maxillary Division of Trigeminal Nerve (V)
Mandibular Division of Trigeminal Nerve (V)
Foramen Spinosum
Foramen Lacerum
Middle Meningeal Artery and Vein
Internal Carotid Artery
Carotid Canal
Facial Nerve (VII) (including intermediate nerve
Internal Acoustic
Vestibulocochlear Nerve (VIII)
Meatus
Labyrinthine Artery
Glossopharyngeal Nerve (IX)
Hypoglossal Canal
Hypoglossal Nerve (XII)
Jugular
Foramen
Vagus Nerve (X)
Accessory Nerve (XI)
Sigmoid Sinus → Internal Jugular Vein
Foramen Magnum
Vertebral Arteries, Medulla of Brain
Spinal roots of Accessory (XI) Nerve
LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 3. The Neck The neck extends anteriorly from the lower border of the mandible to the upper surface of the manubrium, and posteriorly from the superior nuchal line (occipital bone) to the intervertebral disc between C7 and T1. Within the tube there is longitudinal organization into functional compartments: • Anterior visceral compartment – contains parts of the digestive and respiratory systems, as well as several endocrine glands = visceral function • Posterior vertebral compartment – contains the cervical vertebrae, spinal cord, cervical nerves and muscles associated with the vertebral column = structural/support function • Two lateral neurovascular compartments – contain the major blood vessels and the vagus nerve (X) = conduit function The superficial fascia in the neck contains a thin sheet of muscle that blends with the muscles on the face. Deep to this, the deep cervical fascia is organized into several distinct layers: • An investing layer, which surrounds all structures • Prevertebral layer, which surrounds the posterior compartment • Pretracheal layer, which surrounds the anterior compartment • Carotid sheaths, which surround the two lateral compartments Vertebral Levels of the neck C1 – open mouth C2 – superior cervical ganglion C3 – body of hyoid C4 – upper border of thyroid cartilage, bifurcation of the common carotid artery C6 – cricoid cartilage, middle cervical ganglion C7 – inferior cervical ganglion LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 1. Sketch the thoracic inlet to show the relations of the following structures at the neck-­‐chest interface: 1st thoracic vertebra, 1st ribs + cartilages, manubrium, pleura + lungs, oesophagus, trachea, brachiocephalic veins, vagus nerves, brachiocephalic artery, left common carotid and subclavian arteries, sympathetic trunks, left recurrent laryngeal nerve, phrenic nerves The superior thoracic aperture, or thoracic inlet, refers to the superior opening of the thoracic cavity, through which many structures enter the neck from the thorax. • Boundaries: T1 posteriorly, 1st ribs laterally, and the superior border of the manubrium anteriorly • Immediately superior to the thoracic inlet is the root of the neck • The brachial plexus is also a superolateral relation of the thoracic inlet 2. Define the boundaries of the anterior and posterior triangles of the neck Anterior Triangle Posterior Triangle Boundaries •
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the anterior border of the sternocleidomastoid muscle the inferior border of the mandible the midline of the neck •
Muscles – platysma (superficial facial muscle), digastric muscle, strap muscles (infrahyoid), mylohyoid Common carotid arteries Internal jugular vein Larynx and trachea •
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the posterior border of the sternocleidomastoid muscle the anterior border of the trapezius muscle the middle 1/3 of the clavicle External jugular vein Spinal accessory nerve Trunks of the brachial plexus Subclavian artery Subclavian vein Phrenic nerve LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 3. Identify the infrahyoid (strap) muscles, mylohyoid and the digastric muscle The muscles in the anterior triangle of the neck can be grouped according to their location relative to the hyoid bone: • The muscles superior to the hyoid are classified as suprahyoid, and include the stylohyoid, digastric, myolohyoid and geniohyloid • The muscles inferior to the hyoid are classified as infrahyoid and include the omohyoid, sternohyoid, thyrohyoid and sternothyroid Muscle Group Muscle Origin Insertion Innervation Function Suprahyoid Infrahyoid (strap) Stylohyoid Anterior belly of Digastric Body of hyoid Posterior belly Mastoid notch on of Digastric temporal bone Mandibular branch of trigeminal (V) Mylohyoid Myohyloid line on Body of mandible hyoid Mandibular branch of trigeminal (V) Support + elevation of floor of mouth Posterior aspect of sternoclavicular joint Body of hyoid Anterior rami of C1–C3 Depresses hyoid bone after swallowing Omohyoid Superior border of scapula Anterior rami of C1– C3 Depresses and fixes hyoid bone Thyrohyoid Thyroid cartilage Lower border of hyoid Greater horn of hyoid C1 fibres by hypoglossal nerve (XII) sternothyroid Posterior surface of Thyroid manubrium cartilage Depresses hyoid bone When hyoid is fixed, raises larynx Draws laryns downwards Geniohyloid Sternohyoid Digastric fossa on lower inner mandible Facial nerve (VII) Anterior rami of C1–C3 When mandible is fixed, raises hyoid When hyoid is fixed, opens mouth by lowering the mandible LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 4. Demonstrate, using prosections, the position and key relations of the subclavian vein, and brachial plexus (as well as the roots and trunks of the brachial plexus) The brachial plexus is a superolateral relation of the thoracic inlet; it emerges between the anterior and middle scalene muscles (lateral neck muscles), superior to the first rib, and passes obliquely and inferiorly underneath the clavicle and into the shoulder. •
The 5 roots of the brachial plexus are the 5 anterior rami of spinal nerves C5-­‐T1 (after they have given off their segmental supply to the muscles of the neck) As the roots emerge from between the scalene muscles, they merge to form 3 trunks: •
Upper trunk = C5-­‐C5 •
Middle trunk = C7 •
Lower trunk = C8-­‐T1 The trunks cross the base of the posterior triangle of the neck, and several branches may be visible in this triangle. (detailed brachial plexus lecture in anatomy of the limbs notes) The external jugular and anterior jugular veins are the primary venous channels for the superficial venous drainage of the neck. •
The external jugular vein is formed posterior to the angle of mandible. Once formed, it passes straight down the neck in the superficial fascia, and is superficial to the sternocleidomastoid muscle and scalene anterior throughout its course, crossing diagonally as it descends. o The external jugular vein then pierces the investing layer of cervical fascia just superior to the clavicle and immediately posterior to the sternocleidomastoid o Having pierced the investing fascia, it passes deep to the clavicle and enters the subclavian vein •
The anterior jugular veins are paired venous channels that come together just superior to the hyoid bone. Once formed, they descend on either side of the midline. o Inferiorly, near the medial attachment of the sternocledimastoid, each will pierce the investing layer to enter the subclavian vein LCRS Anatomy of the Head, Neck & Spine •
Alexandra Burke-­‐Smith The subclavian vein ends by joining with the internal jugular vein to form the brachiocephalic vein near the sternoclavicular joint o NB: in the posterior triangle, the subclavian lies anterior, and slightly inferior, to the subclavian artery, and passes anterior to the anterior scalene 5. Explain the uses of central venous lines and indicate the landmarks for insertion of a central line into the internal jugular vein. In certain circumstances, it is necessary to place a larger-­‐bore catheter into the central vein, for example for dialysis, parenteral nutrition, haemodynamic monitoring, or the administration of drugs that have a tendency to produce phlebitis. •
“blind puncture” of the subclavian and jugular veins to obtain central venous access used to be a standard procedure o however, subclavian vein puncture is not without complications. As the subclavian vein passes inferiorly and posterior to the clavicle, it passes over the apex of the lung. Any misplacement of a needle into or through this structure may puncture the apical pleura, producing a pneumothorax, or inadvertent arterial puncture (> haemothorax) o a puncture of the internal jugular vein carries fewer risks, but local haemotoma and damage to the carotid artery are again important complications •
Current practice is to identify major vessels using ultrasound and to obtain access under direct vision •
the IJV puncture site is found be palpating the common carotid artery and inserting the needle into the IJV just lateral to it (at a 30 degree angle, aiming at the apex of the sternal and clavicular heads of the sternocleidomastoid) o the needle is then directed inferolaterally towards the ipsilateral nipple 6. List the possible complications of insertion of central venous lines •
Arterial puncture leading to haematoma and potential airway obstruction •
Pneumothorax •
Nerve damage •
Air embolism •
Thrombosis •
Misplacement •
Perforation of the great vessels and heart •
Infection 7. Demonstrate the position, key relations and courses of the internal thoracic and vertebral branches of the subclavian artery The subclavian arteries on both sides arch upward out of the thorax to enter the root of the neck. •
The right subclavian artery begins posterior to the sternoclavicular joint as a terminal branch of the brachiocephalic trunk. It arches superiorly and laterally to cross the anterior scalene posteriorly in the root of the neck. As it crosses rib I, it then forms the axillary artery •
The left subclavian begins as a direct branch of the aortic arch. Lying posterior to the left common carotid, and lateral to the trachea, it ascends and arches laterally The course from the origin to the scalene muscle is considered to be the first part of the subclavian arteries, and nearly all branches arise from here. These include: •
The vertebral artery •
The internal thoracic artery •
Thyrocervical trunk LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith The vertebral artery is the first branch of the subclavian. Medial to the anterior scalene, it ascends and enters the foramen in the transverse process of C6 and then continues superiorly. At the superior border of C1, the artery turns medially and passes through the foramen magnum to enter the posterior cranial fossa The thyrocervical trunk is the second branch of the subclavian. It arises medial to the anterior scalene and divides into 3 branches: •
The inferior thyroid artery (superior continuation supplying the posterior thyroid gland) •
The transverse cervical artery (lateral branch supplying the trapezius + rhomboid muscles) •
The suprascapular arteries (lowest, lateral branch that traverses into the supraspinatus fossa) NB: blood supply to the thyroid •
Superior thyroid artery – branch of the external carotid •
Inferior thyroid artery – branch of the thyrocervical trunk •
Superior thyroid vein – drains into the internal jugular •
Middle thyroid vein – drains into the internal jugular •
Inferior thyroid vein – drains into the brachiocephalic vein The internal thoracic artery is the third branch of the subclavian; it branches from the inferior edge and descends. •
It passes posterior to the clavicle and the large veins in the region, and anterior to the pleural cavity. •
It enters the thoracic cavity posterior to the ribs and anterior to the transversus thoracis muscle, and continues to descend giving off numerous branches 8. Locate the carotid pulse and explain the main uses of this central pulse The carotid system Common carotid arteries are the beginning of the carotid system. •
The right common carotid originates from the brachiocephalic •
The left common carotid originates from the aortic arch, entering the neck near the left sternoclavicular joint Both common carotids ascend through the neck just lateral to the trachea. Near the superior edge of the thyroid they divide into the external and internal carotid arteries. At this bifurcation there is a dilation of the internal carotid = carotid sinus. •
The internal carotid then ascends and enters the cranial cavity through the carotid canal, supplying the cerebral hemispheres, eyes, contents of the orbits and forehead •
The external carotid immediately begin to branch, and have numerous branches supplying the face, neck and scalp The carotid pulse is easy to feel by palpating the common carotid arteries on either side of the neck, which lies in a groove between the trachea and infrahyoid muscles. The main uses are: •
Assessment of pulse rhythm, rate, character •
Timing of murmurs •
To locate the jugular vein o Jugular venous pulse is an important clinical sign that enables the physician to asses the venous pressure and waveform and is a reflection of the functioning of the right side of the heart LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 9. Demonstrate the technique for palpation of the cervical lymph nodes and define their field of drainage The basic pattern of lymphatic drainage is for superficial lymphatic vessels to drain to the superficial lymph nodes, which drain into deep nodes and eventually drain into the deep nodes of the jugular vein. 5 groups of superficial nodes form a ring around the head, draining the face and scalp. Beginning posteriorly, there are: •
occipital •
mastoid •
parotid •
submandibular •
submental Drainage from the occipital and mastoid nodes pases to the superficial cervical nodes along the external jugular vein, and the other 3 groups drain into the deep cervical nodes. •
The superficial cervical nodes are a vertical line of nodes along the external jugular vein on the superficial surface of the sternocleidomastoid – receive mainly posterior and posterolateral drainage •
The deep cervical nodes form along the internal jugular vein, forming upper and lower groups. From the deep cervical nodes, lymphatic vessels form the right and left jugular trunks, which empty into the right lymphatic duct on the right side, or the thoracic duct on the left side. Cervical lymphadenopathy is a common manifestation of diseases that occur in the head and neck. •
Soft, tender, and inflamed lymph nodes suggest an acute inflammatory process, which is most likely to be infective •
Firm, multinodular large-­‐volume rubbery nodes often suggests a diagnosis of lymphoma 10. Describe the origin, course and function of the phrenic and spinal accessory nerves Phrenic nerve The phrenic nerves are branches of the cervical plexus and arise on each side as contributions from the anterior rami of C3-­‐C5 •
Passing around the upper lateral border of each anterior scalene muscle, the phrenic nerves continue inferiorly across the anterior surface of each anterior scalene muscle within the prevertebral fascia •
Leaving the lower edge of the anterior scalene, each phrenic nerve passes between the subclavian vein and enter the thorax and continue into the diaphragm o The right phrenic passes close to the IVC o The left phrenic pierces the diaphragm •
The function of the phrenic nerves is motor supply to the diaphragm, and sensory innervation of the diaphragmatic pleura and peritoneum (3,4,5 keeps the diaphragm alive) Spinal accessory nerves This is considered to be CNXI. •
It provides motor innervation to the sternocleidomastoid (head rotation) and trapezius (shoulder shrug) •
Originates in neuron cell bodies in cervical spinal cord, enters the skull via foramen magnum, then courses along inner wall of skull to jugular foramen where it exits the skull •
In the neck, the accessory nerve crosses the internal jugular vein (at level of posterior belly of digastric), then continues inferiorly, piercing the sternocleidomastoid and reaching the trapezius. LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 4. Biting, Chewing and Swallowing 1. Outline the main neuromuscular systems involved in biting, chewing, salivation and swallowing. Demonstrate how the temporo-­‐mandibular joint and muscles of mastication produce chewing movements. SWALLOWING The Pharynx The pharynx is a musculofascial half-­‐cylinder that links the oral and nasal cavityes in the head to the larynx and oesophagus in the neck. The pharyngeal cavity is a common pathway for air and food, extending from the base of the skull to the inferior border of the cricoid cartilage (C7), where it becomes continuous with the oesophagus •
Posteriorly, the pharynx is associated with prevertebral fasica •
Anteriorly, the walls of the pharynx are attached to the margins of the nasal cavities, oral cavity + larynx. Based on these anterior relationships the pharynx is subdivided into 3 regions: o The nasopharynx -­‐ o The oropharynx o The laryngopharynx LCRS Anatomy of the Head, Neck & Spine •
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Alexandra Burke-­‐Smith The nasopharynx communicates with the oropharynx through the pharyngeal isthmus, which is bounded by the soft palate (this can be elevated or depressed to either seal off the nasopharynx/oral cavity from the oropharynx). o The nasopharyngeal tonsil (adenoid) is embedded in the mucous membrane of the posterior wall of the nasopharynx, and may be enlarged during infection > respiratory obstruction The oropharynx extends from the soft palate to the superior border of the epiglottis. o This communicates anteriorly with the oral cavity by the oropharyngeal isthmus, o This area is characterised by a lymphatic ring of lingual, pharyngeal and palatine tonsils o the epiglottis retroflexes to cover the trachea during swallowing The laryngopharynx extends from the superior border of the epiglottis to the inferior border of the cricoid cartilage, where it becomes continuous with the oesophagus. o Its anterior aspect has the inlet of the larynx, and the posterior aspects of the arytenois + cricoid cartilage. On each side of the inlet of the larynx is a piriform recess, in which foreign bodies may become lodged The pharyngeal wall is formed by skeletal muscles. The muscles of the pharynx are organized into two groups based on the orientation of muscle fibres: •
Constrictor muscles – circularly arranged muscle fibres •
Longitudinal muscles – vertically arranged muscle fibres The 3 constrictor muscles on each side are the major contributors to the structure of the pharyngeal wall. •
The superior, middle and inferior constrictors have their fixed attachment anteriorly, where they attach to the bones and ligaments related to the lateral margins of the nasal and oral cavities and the larynx •
Posteriorly, the muscles from each side are joined together by the pharyngeal raphe •
Collectively these muscles act to narrow the pharyngeal cavity. When they contract sequentially from top to bottom, as in swallowing, they move a bolus of food through the pharynx and into the oesophagus •
All of the constrictors are innervated by the pharyngeal branch of the vagus nerve (X) The 2 longitudinal muscles elevate the pharyngeal wall, or during swallowing, pull the pharyngeal wall up and over a bolus of food being moved through the pharynx and into the oesophagus. The Tongue The tongue is a muscular structure that forms part of the floor of the oral cavity, and part of the anterior wall of the oropharynx. The bulk of the tongue is composed of muscles, divided into a left and right half by a median saggital septum (therefore all the muscles are paired) •
There are both intrinsic muscles and extrinsic muscles. Except for the palatoglottus, which is innervated by the vagus nerve (X), all the muscles of the tongue are innervated by the hypoglossal nerve (XII) •
The intrinsic muscles of the tongue originate and insert within the substance of the tongue, and are involved in altering the shape of the tongue •
The extrinsic muscles originate from structures outside of the tongue, and insert into the tongue: o Genioglossus – protrudes + depresses tongue o Hyoglossus – depresses tongue o Styloglossus – elevates + retracts tongue o Palatoglossus – depresses palate + elevates back of tongue •
The anterior 2/3 of the tongue o Sensation = mandibular division of trigeminal (V) o Taste = facial (VII) •
The posterior 2/3 of the tongue o Sensation + taste = glossopharyngeal (IX) LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith Swallowing Following biting/chewing, the bolus of food has been propelled to the posterior 1/3 of the oral cavity. The swallowing process is complex and involves a series of steps: 1) Lift + retract tongue (uses styloglossus + intrinsic muscles) 2) Move bolus into oropharynx (palatoglossus) 3) Close off nasopharynx by raising soft palate 4) Raise larynx + close off by epiglottis 5) Peristaltic wave of constrictor muscles 6) Relax cricopharyngeus + open oesophagus (so bolus moves into oesophagus) SALIVATION Salivary Glands These are glands that open or secrete into the oral cavity. In addition to the small glands in the mucosa/submucosa of the oral epithelium, there are larger paired glands including: •
parotid gland •
submandibular gland •
sublingual gland The parotid gland is entirely outside the boundaries of the oral cavity, extending anteriorly over the masseter muscle, and inferiorly over the posterior belly of the digastric •
The parotid duct penetrates the buccinators muscle and opens into the oral cavity adjacent to the crown of the 2nd upper molar tooth •
It is responsible for mainly serous secretions •
It encloses the external carotid artery, retromandibular vein + extracranial part of the facial nerve (VII) •
It is innervated by glossopharyngeal nerve (IX) The submandibular gland lies along the body of the mandible, partly superior and partly inferior. •
It is partly superficial and partly deep to the mylohyoid muscle •
The submandibular duct passes forward to open out either side of the frenulum of the tongue; mainly serous secretions •
Innervated by facial nerve (VII) The sublingual salivary glands are scattered along the submandibular duct into which some of the open •
Others open directly into the oral cavity •
Innervated by the facial nerve (VII) •
Mainly mucous secretions Salivation Secretomotor impulses to both glands originate in the superior salivary nucles and pass through the VII (facial), the chorda tympani, lingual nerve and the submandibular ganglion BITING + CHEWING Biting + Chewing •
Biting involves opening and closing the mouth and jaw. •
In addition to biting, chewing requires the protrusion and retrusion of the chin, as well as lateral movements of the jaw LCRS Anatomy of the Head, Neck & Spine •
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Alexandra Burke-­‐Smith The movements of the jaw that occur during mastication can be summarized as elevation, depression, grinding, protraction and retraction Mastication is also aided by the buccinators muscles of the face, which push the cheeks against the molar teeth when chewing The Muscles of Mastication Muscle Origin Masseter Zygomatic arch Temporalis Temporal fossa Medial Pterygoid Medial side of lateral pterygoid plate, palatine bone and maxillary tuberosity Sphenoid + pterygoid plate Lateral Pterygoid Insertion lateral surface of ramus and angle of mandible coronoid process of mandible Medial angle of the mandible Neck of mandible Innervation Mandibular branch of trigeminal (V) Function Elevates mandible for forced closure of mouth Elevates and retracts mandible Elevates, protracts and lateral movement of mandible Depresses and protracts mandible to open mouth (mainly gravity) Other muscles include: •
Buccinator – check muscle that aids mastication by pressing the cheeks against molars when chewing (supplied by facial nerve [VII]) •
Suprahyoid + infrahyoid muscles (see previous lecture) – can help to depress the mandible when opening the mouth suddenly/against resistance LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith The Temporo-­‐mandibular joint Here, two synovial cavities are separated by a fibrocartillagenous disc •
The lower part = depression + elevation of mandible •
The upper part – protrusion (onto articular tubercle) + retraction (into mandibular fossa) Opening of the mouth involves depression + protrusion. Closing of the mouth involves elevation + retraction. •
By protruding the mandible, greater depression is allowed. •
Side to side movements are enabled by contralateral heads rotating on the inferior surface of the articular disc 2. Identify the major branches of the external carotid artery See previous lecture for notes on the routes of the common carotids + their bifurcation. In order of ascending branch, the external carotid artery branches into: •
Superior thyroid •
Ascending pharyngeal •
Lingual •
Facial •
Occipital •
Posterior auricular •
Superficial temporal •
Maxillary 3. Demonstrate the routes by which the maxillary, mandibular, facial, glossopharyngeal, vagus, and hypoglossal nerves leave the skull, and indicate the courses of the lingual and inferior alveolar nerves (used Jack Roberts notes here) •
The mandibular nerve (V3) is the largest and most inferior branch of the trigeminal nerve and it exits through the foramen ovale o The lingual nerve arises from the mandibular nerve (including chorda tympani VII component). The lingual nerve lies anterior to the inferior alveolar nerve. It is sensory to the anterior two-­‐thirds of the tongue, the floor of the mouth, and the lingual gingivae o The inferior alveolar nerve enters the mandibular foramen and passes through the mandibular canal forming the inferior dental plexus, which sends dental branches to all mandibular teeth on its side LCRS Anatomy of the Head, Neck & Spine •
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Alexandra Burke-­‐Smith The maxillary nerve (V2) leaves through the foramen rotundum The facial nerve (VII) leaves through the internal acoustic meatus The glossopharyngeal nerve (IX) leaves through the jugular foramen The vagus (X) leaves through the jugular foramen The hypoglossal (XII) leaves through the hypoglossal canal 4. Assess those functions of the trigeminal (V), facial (VII), glossopharyngeal (IX), vagus (X) and hypoglossal (XII) nerves which relate to biting, chewing and swallowing Cranial Nerve Function Test Trigeminal (V) Ophthalmic division (V1) – supplies skin of forehead, upper eyelids, nose midline, anterior surface of eye, nasal mucosa and frontal sinus Maxillary division (V2) – supplies the skin of the temple and face and inferior as the corners of the mouth, as well as upper teeth, lips, gums and palate Mandibular division (V3) – supplies a strip of skin from the temple to the chin, the lower teeth, gums, lips, floor of the mouth, and the anterior 2/3rds of the tongue Facial (VII) Proprioception of the muscles of the face, taste of anterior 2/3rds of tongue Somatic motor to muscles of face, scalp and neck Parasympathetic to glands of face Glossopharyngeal Sensation + taste of posterior 1.3rd of tongue + (IX) oropharynx Proprioception of swallowing Motor to stylopharyngeal muscle Parasympathetic to parotid gland Vagus (X) Somatic sensation from larynx Motor to muscles of throat and neck Parasympathetic to smooth muscle of trachea + oesophagus Hypoglossal (XII) Motor nerve of tongue; causing movement during speech and swallowing Test sensations (fine + crude touch) Test taste Ask to change expression Ask to salivate/cry Test taste + sensation at back of tongue Encourage gag reflex Test swallowing, coughing + voice production Stick out tongue; deviation suggests lesion on ipsilateral side 5. Describe the relationship between the facial nerve and the parotid gland The parotid duct emerges from the anterior border and passes forwards on the masseter, then turns medially and penetrates the buccinator and opens into the mouth opposite the second upper molar tooth • The facial nerve emerges from the skull through the stylomastoid foramen (via internal acoustic meatus) in the temporal bone. The extracranial part then enters the parotid gland (does not innervate it), continues superficially, and forms a complex and variable plexus • Branches of VII emerge from the anterior margin in five groups: o Temporal – to frontal belly of occipitofrontalis o Zygomatic – to orbicularis oculi and upper face o Buccal – to buccinatorm orbicularis oris and mid face o Marginal mandibular – to orbicularis oris and the corner of the mouth o Cervical – to platysma • As the nerve is superficial, it is easy to damage leading to facial palsy. The mandibular branch is particulary in danger as it passes just below the lower margin of the mandible • Bell’s palsy = a lower motor lesion of the facial nerve – lesion of cell bodies or the nerve itself causing the muscles of the face to sag on the affected side LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 6. Identify the positions of the parotid and submandibular glands and the lymph nodes draining the oral and oropharangeal structures See notes above on salivary glands Lymphatic drainage of the salivary glands is either directly via the submandibular, submental or parotid nodes (see lecture 3) 7. Identify the teeth in the living mouth and record them accurately; recognize characteristic dental patterns for children and adults A full set of adult teeth is 32 teeth (including wisdom teeth) or 28 without. In each quadrant of the mouth, there are: •
2 incisors •
1 canine •
2 premolars •
3 molars In a complete deciduous (baby) set, there are 20 teeth (no premolars or wisdom teeth) •
The first deciduous come at 6-­‐8 months and are complete by 20-­‐24 months •
Permanent adult teeth start at 6 years and are complete by the early 20s •
These ages can be used as development milestones 8. Be able to identify the following structures in the living mouth: hard and soft palate uvula, faucil pillars, palatine tonsils, lingual papillae, parotid and submandibular papillae, sublingual glands, frenulum, genioglossal ridge • Faucil pillars -­‐ a pair of curved ridges Palatopharangeal fold
running down the soft palate • Parotid papillae – small raised patch near the 2nd upper molar – opening Palatine
of parotid duct tonsil
• Submandibular papillae – fleshy tag with a forked tip found as you run down the lower gums and mandibular Uvula
symphysis – where the Palatoglossal
fold
submandicular salivary ducts open • Sublingual glands – bumpy bit on the lower lateral buccal floor (the lingual papillae) Posterior wall of
• Frenulum -­‐ small fold of tissue that oropharynx
secures or restricts the motion of a mobile organ in the body o Oral tissue: Frenula of the mouth include the frenulum linguae under the tongue, the frenulum labii superioris inside the upper lip, the frenulum labii inferioris inside the lower lip, and the buccal frena which connect the cheeks to the gum • Genioglossal ridge – a smooth, firm rounded ridge running along the midline of the floor of the mouth to the tongue formed by the genioglossus muscle LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 9. Discuss the physiology of swallowing, as well as discussing normal and abnormal swallowing Swallow physiology Oral preparatory phase (voluntary) •
Food/liquid chewed > bolus formation •
Bolus held on centre of tongue Oral transit phase (voluntary; airway open) •
Bolus propelled to back of mouth •
Palate seals entry to nasal cavity Pharyngeal phase I (reflex) •
Triggered when bolus reaches faucial arch •
Palate stays elevated •
Tongue retracts to push bolus to pharynx Pharyngeal phase II (reflex; airway closed) •
Bolus propelled through pharynx Oesophageal phase (reflex control) •
Oesophagus opens, airway closed, breath held •
Bolus propelled through oesophagus Normal vs Abnormal Swallowing Swallowing can be visualized by Barium swallow imaging Type of swallow Features Normal Swallow Oral transit 1 sec Pharyngeal transit 1-­‐2 sec No residue No spillage in airway Ataxic swallow Uncoordinated tongue retraction (cause: Delayed airway closure + cerebellar delayed/ineffective cough > food in haematoma) airways Lower motor Imsilateral paresis of phanyx, larynx, neurone tongue > weak bolus propulsion > swallow (cause: residue excised acoustic Failure of airway closure > aspiration neuroma) Impaired Decreased movement of pharynx + swallow (severe tongue head injury) Residue in pharynx Aspiration of saliva Ineffective cough Management Flexed neck during swallow prevents aspiration exercises to increase swallow speed/strength Head rotation to direct bolus to strong side Exercises to improve tongue + laryngeal muscle strength Long term nil-­‐by-­‐mouth + tracheostomy LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 5. Breathing, Voice and Hearing NOTES The Upper Respiratory Tract refers to parts of the respiratory tract lying above the sternal angle. This includes the nose, nasal cavities, paranasal sinuses, pharynx and larynx. THE NASAL CAVITIES The 2 nasal cavities are the uppermost parts of the respiratory tract and contain the olfactory receptors. They are elongated wedge-­‐shaped spaces with a large inferior base and superior apex and are held open by a skeletal framework consisting of mainly bone and cartilage. •
The anterior apertures of the nasal cavities are the nares (nostrils), which open onto the inferior surface of the external nose. •
The posterior apertures are the choanae, which open into the nasopharynx The nasal cavities are separated: •
From each other by a midline nasal septum •
From the oral cavity below by the hard palate •
From the cranial cavity above by parts of the frontal, ethmoid and sphenoid bones Each nasal cavity therefore has a roof, floor, medial and lateral wall •
The lateral wall is characterized by 3 curved shelves of bone = conchae; these divide the nasal cavity into 4 air chambers, thus increasing the surface area of contact with respired air •
The openings of the paranasal sinuses, which are extensions of the nasal cavity that erode into the surrounding bones during childhood and early adulthood, are on the lateral wall and roof Each nasal cavity consists of 3 general regions: •
The nasal vestibule – small dilated space just internal to the naris that is lined by skin and contains hair follicles o Important in particle removal •
The respiratory region – largest part of the nasal cavity; rich neurovascular supply, and is lined by respiratory epithelium composed mainly of ciliated and mucous cells LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith Large blood supply responsible for adjustment of temperature and humidity of respired air •
The olfactory region – at the apex of each nasal cavity; lined by olfactory epithelium, and contains the olfactory receptors. Ones that contribute to the skeletal framework of the nasal cavities include: •
Ethmoid – complex bones that lies between the two orbits; it contributes to the roof, lateral wall and medial wall of both nasal cavities, and contains the ethmoidal sinuses within the ethmoid labyrinths •
Other unpaired bones = sphenoid, frontal bone, vomer •
Paired nasal, maxillary, palatine and lacrimal bones, and inferior conchae PARANASAL SINUSES There are 4 paranasal air sinuses: the ethmoidal cells, and the sphenoidal, maxillary and frontal sinuses •
Each is named according to the bone in which it is found. •
The paranasal sinuses develop as outgrowths from the nasal cavities and erode into the surrounding bones. All are: o Lined by ciliated + mucous secreting respiratory mucosa o Open into the nasal cavities o Innervated by branches of the trigeminal nerve •
The functions of the paranasal sinuses are to reduce the weight of the facial skeleton and act as resonators for the coice •
The paranasal sinuses are connected to the pharynx by small holes and therefore are a route for infection (build of mucus in the sinuses > pain + possible infection) o
Frontal Sinus – located in the frontal bone under the forehead, and terminate laterally along the upper margin of the orbit •
Each drains via the frontonasal duct, which penetrates the ethmoidal labyrinth, continuing as the ethmoidal infundibulum at the front of the semilunar hiatus LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith Innervated by branches of the supraorbital nerve from ophthalmic branch of trigeminal (V) Ethmoidal cells – cluster of cells within the ethmoidal labyrinth •
The anterior ethmoidal cells open into the ethmoidal infundibulum or frontonasal duct •
The middle ethmoidal cells open onto the ethmoidal bulla •
The posterior ethmoidal cells open onto the superior nasal meatus •
Innervated by ethmoidal branches of nasociliary nerve from the ophthalmic branch of trigeminal, as well as maxillary branch of trigeminal (V) Maxillary sinuses – these are the largest; fill the maxilla (just behind cheecks) extending between inferior border of the orbit and the upper lip •
The opening of the maxillary sinus is near the top of the base, in the centre of the semilunar hiatus. This doesn't drain particularly well, so requires filling before emptying •
There is only a thin layer of bone between the sinus and the teeth so a tooth infection can infect the sinus as well •
Innervated by infra-­‐orbital and alveolar branches of the ophthalmic branch of trigeminal (V) Sphenoidal sinus – located just posterior to the ethmoidal air cells in the sphenoid bone •
Opens into the roof of the nasal cavity via the sphenoethmoidal recess •
Close proximity to the pituitary gland, therefore pituitary surgery can use transphenoidal entry •
Innervated by posterior ethmoidal branch of the ophthalmic branch, and the maxillary branch of the trigeminal nerve LARYNX The cavity of the larynx is continuous below with the trachea, and above opens into the pharynx immediately posterior and slightly inferior to the tongue and oropharyngeal isthmus (opening of the oral cavity) •
The larynx is both a valve to close the lower respiratory tract, and an instrument to produced sound. It is composed of o 3 large unpaired cartilages – cricoid, thyroid + epiglottis o 3 pairs of smaller cartilages (arytenoid, corniculate and cuneiform) o a fibro-­‐elastic membrane and numerous intrinsic muscles •
The larynx is suspended from the hyoid bone above and attached to the trachea below by membranes and ligaments. It is highly mobile in the neck, and during swallowing this movement facilitates the closing of the laryngeal inlet and opening of the oesophagus •
Motor and sensory innervation of the larynx is provided by the vagus nerve (laryngeal nerve branch) Structure •
The hyoid bone is located at the base of the mandible and serves as the point of attachment for some neck muscles. •
The thyroid cartilage is the largest of the laryngeal cartilages; formed by a right and left lamina which are widely separated posteriorly but converge and join anteriorly (superior anterior prominence = Adam’s apple) o The angle between the two lamina is 90 degrees in men, and 120 degrees in women (more apparent in men) o The posterior margin of each lamina is elongated to form a superior + inferior horn (which are associated with the cricoid cartilage and hyoid bone respectively) •
The epiglottis is a leaf-­‐shaped cartilage attached by its stem to the posterior aspect of the thyroid cartilage. o This acts as a flap which closes off the trachea during swallowing to direct food into the oesophagus. o If food or liquid does enter the trachea and contacts the vocal folds, it causes a cough reflex to expel the matter in order to prevent choking •
LCRS Anatomy of the Head, Neck & Spine •
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Alexandra Burke-­‐Smith The cricoid cartilage is the most inferior of the laryngeal cartilages and completely encircles the airway. The two arytenoid cartilages are pyramidal-­‐shaped cartilages postero-­‐inferior to the epiglottis; associated with the vocal folds + phonation. Lateral View Posterior View Mid-­‐Saggital View Function Phonation •
Vocal folds are located within the larynx at the top of the trachea. They are attached posteriorly to the arytenoid cartillages, and anteriorly to the thyroid cartilage •
Their outer edges are attached to muscle within the larynx, while their inner margins are free •
Above both sides of the vocal folds are the vestibular folds = false vocal folds. These have minimal role in normal phonation, but rather in screaming or deep growling. •
When phonating, the arytenoid cartilages and vocal folds are adducted and air is forced through between them o This action causes the vocal folds to vibrate against each other and produce sounds, which can be modified by the upper parts of the airway and oral cavity. o Tension in the vocal folds can be adjusted by laryngeal muscles •
Pitch depends on the relative position and tension in the vocal folds by the movement of arytenoid cartilages and cricothyroid joint •
Intensity of sound depends on the force with which air is pushed through the glottis •
Quality of sound depends on resonation in the pharynx, oral cavity and paranasal sinuses •
Words depend on the shaping of sound with the mouth, particularly the tongue and lips. LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith Respiration •
During quiet respiration, the arytenoid cartilages are abducted and the vocal folds are open •
During forced inspiration, the arytenoid cartilages are rotated laterally, and the rima glottides widens into a rhomboid shape, which effectively increases the diameter of the laryngeal airway Effort closure •
This occurs when air is retained in the thoracic cavity to stabilize the trunk, for example during heavy lifting, or as part of the mechanism to increase intra-­‐abdominal pressure. •
During this, the rima glottides is completer closed, and the airway is then completely shut Swallowing During swallowing, the vocal folds are closed, and the laryngeal inlet is narrowed. In addition the larynx moves up and forward •
This action causes he epiglottis to close the laryngeal inlet •
The up and forward movement also opens the oesophagus, which is attached to the posterior aspect of the lamina of the cricoid cartilage •
All these actions prevent solids and liquids from entry into the airway and facilitate their movement into the oesophagus THE EAR The anatomy of the ear is split up into 3 main sections: Outer ear Middle ear Inner ear •
Pinna/ Auricle •
3 Auditory ossicles •
Oval and round o Malleus windows •
External acoustic o Incus •
Utricle and saccule meatus o
Stapes •
Cochlea •
Typanic membrane •
Auditory nerve (VIII) •
Phanygotympanic tube •
Semicircular canals LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith FACIAL NERVE The facial nerve has 3 functional components: •
Motor – to the muscles of facial expression •
Sensory – branches to the cauda tympani where it joins the lingunal nerve (branch of mandibular trigeminal) just after the acoustic meatus to supply the anterior 2/3rds of tongue •
Parasympathetic secretor motor – to the salivary (not parotid) and lacrimal glands The route of the facial nerve is as follows: •
The facial nerve leaves the brain at the junction of the pons and medulla via the internal acoustic meatus •
It then passes through the stylomastoid foramen (hole between the mastoid and styloid process of the temporal bone), to supply the face via the parotid gland •
Bell’s Palsy = inflammation of the stylomastoid foramen (bony canal) can put pressure on the nerve which causes ipsilateral facial paralysis. o Depending on the site of inflammation will determine which branches affected o In 80% of cases the nerve regenerates LEARNING OBJECTIVES 1. List the mechanisms which protect the lungs and bronchi against aspiration of food and drink There are two main mechanisms which function when swallowing •
Levator veli palatine -­‐ muscle elevates the soft palate (mucous membrane that tapers to form uvula) during swallowing, pushing the soft palate against the wall of the pharynx, thereby preventing the passage of the food into the nasal cavity •
When swallowing, a peristaltic wave of activity of the constrictor muscles of the pharynx raises the larynx which becomes closed off by the epiglottis Other mechanisms that offer protection include: •
Gag reflex •
Sneezing – see below •
Coughing – see below LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 2. Explain (in terms of sensory and motor pathways and muscle groups) the sneeze and cough reflexes SNEEZING
COUGHING
Inspiration
Intrathoracic pressure raised
(glottis closed, abdominal muscles contracted)
Soft palate depressed against tongue
(palatopharyngeus/palatoglossus)
Soft palate raised and tensed against
posterior wall of pharynx. (Levator veli
palatini, tensor veli palatini, sup.
constrictor)
Sudden abduction of vocal folds to release
intrathoracic pressure through nose or mouth
Cough Reflex •
Irritation of receptors in the larynx and trachea is sensed by laryngeal branches of the vagus nerve (X) •
This causes the phrenic nerve (C3-­‐C5) + thoracic nerves (T1-­‐T12) to initiate a deep inhalation •
This results in a build up of pressure in the thorax against the closed glottis, followed by forced exhalation o During exhalation, the oropharyngeal isthmus is open so that the air escapes through the mouth Sneeze Reflex •
The ophthalmic + maxillary branches of the trigeminal (V) sense irritation of receptors in the nasal mucosa •
This causes the phrenic nerve (C3-­‐C5) + thoracic nerves (T1-­‐T12) to initiate a deep inhalation •
This results in a build up of pressure in the thorax against the closed glottis, followed by forced exhalation o During exhalation, the oropharyngeal isthmus is closed so that the air escapes through the nose 3. Demonstrate, using prosections, the landmarks of the nasal cavities, nasopharynx and soft palate 4. Demonstrate in living subjects the body of the hyoid, the thyroid and cricoid cartilages, the cervical part of the trachea, and the thyroid isthmus 5. Demonstrate in living subjects and imaging the positions of the paranasal sinuses; define their sensory nerve supply; explain the clinical significance of their drainage routes 6. Explain the importance of the relationship of the maxillary sinus to the roots of the upper teeth, and of the sphenoid sinus to the pituitary fossa See notes above LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 7. Explain pressure equalisation between the pharynx and the middle ear The pharyngotympanic (auditory) tube connects the tympanic cavity of the middle ear to the nasopharynx, where it opens posteriorly •
This tube is tonically closed by a sphincter, but during swallowing and yawning it opens so that air can leave or enter the middle ear and equalize pressure with the nasopharynx and hence the atmosphere •
It is also a possibly route of infection from the pharynx to the middle ear 8. Explain the clinical importance of the relationship of the mastoid antrum and the mastoid air cells to the middle ear cavity in the skull The posterior wall of the middle ear is the mastoid wall which contains the mastoid air cells. These continue through the temporal bone including the mastoid process. •
They are connected via mastoid antrum to the tempanic cavity of the middle ear, as well as only being separated from the middle cranial fossa by the thin tympanic membrane •
This means that infection can spread from pharynx to middle ear to mastoid process. This may result in temporal bone erosion and infection of the meninges 9. Identify the features of the external auditory meatus and eardrum that can be seen through an auroscope If the cone of light is visible through an auroscope, the ear is considered normal. Infection of the middle ear will result in a loss of this cone of light. LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 10. Outline the contributions of the structures and spaces of the airway and oral cavity to voice production See notes 11. List the actions that may be taken to restore patency of the airway in an emergency •
Chin lift/jaw thrust – this straightens + opens up the airway, making it easier for patient to breathe on their own •
Use of oropharyngeal or nasopharyngeal airway •
Endotracheal intubation – passing a tube into trachea through mouth •
Cricothyroidotomy •
Treacheotomy 12. Describe the anatomical basis of tracheotomy and cricothyroidotomy Cricothyroidotomy involves piercing the cricothyroid membrane in the midline, between the thyroid and cricoid cartilage •
Needle = large-­‐bore cannula use •
Surgical = surgical hole + cuffed tube (much better airway protection) Tracheostomy involves retracting the infrahyoid muscles, dividing the isthmus of the thyroid and piercing the trachea between the 1st and 2nd cartilaginous ring •
A tracheostomy tube is then inserted, and secured with neck straps •
This is a much more permanent procedure 13. Explain likely consequences of disease or injury of a recurrent laryngeal nerve and of the superior part of the cervical sympathetic chain Loss of voice LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 6. The Eye and Sight 1. Describe briefly the margin and walls of the bony orbit and name its important contents The orbits are bilateral structures in the upper half of the face below the anterior cranial fossa and anterior to the middle cranial fossa. It contains the eyeball, optic nerve, the extra-­‐ocular muscles, the lacrimal apparatus, adipose tissue, fascia, and the nerves and vessels that supply these structures •
7 bones contribute to the framework of each orbit. •
Together they give the bony orbit the shape of the pyramid, with its wide base opening anteriorly onto the face, and its apex extending in a posteromedial direction. •
Completing the pyramid configuration are medial, lateral, superior and inferior walls. Superior wall (roof) – separates contents from the brain •
Orbital plate of frontal bone •
Small contributions from the lesser wing of sphenoid bone Medial wall •
Frontal process of maxilla •
Lacrimal •
Ethmoid •
Small contributions from the lesser wing of the sphenoid Inferior wall (floor) •
Orbital surface of maxilla •
Small contribution from zygomatric and palatine bones Lateral wall •
Zygomatic (anteriorly) •
Greater wing of sphenoid (posteriorly) 2. Identify the rectus and oblique muscles, levator palpebrae superioris and orbicularis oculi in suitable specimens There are two groups of muscles within the orbit: •
The extrinsic (extra-­‐ocular) muscles – involves in movements of the eyeball or raising upper eyelids •
The intrinsic muscles – within the eyeball; control the shape of the lens and size of the pupil The extrinsic muscles of the eye are involved in movement of the eyeball in 3 dimensions: •
Elevation – moving the pupil superiorly •
Depression – moving the pupil inferiorly •
Abduction – moving the pupil laterally •
Adduction – moving the pupil medially LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith Functions of the extrinsic eye muscles (below) Levator plapebrae superioris – lies above the superior rectus below the frontal bone. This acts the elevate, adduct + medially rotate the eye as well as elevate the eyelid (when you look up far) NB: The Orbicularis oculi is NOT an extrinsic muscle of the eye, but is involved in the closing of the eye. It consists of two parts: •
Orbital part: this surrounds the orbit, and is involved when the eye is tightly closed •
The palpebral part: this is the eyelid, and is involved when the eye is gently closed LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 3. Test function of the following cranial nerve: occulomotor (I), trochlear (IV), ophthalmic division of trigeminal (V), abducens (VI), facial (VI – to orbicularis oculi) A series of eye movements can be used to isolate the function of and test the specific muscle/nerve supplying it. The nerves supplying the muscles of eye are: •
Superior rectus = superior branch of occulomotor (III) •
Inferior rectus = inferior branch of occulomotor (III) •
Medial rectus = inferior branch of occulomotor (III) •
Lateral rectus = abducens (VI) •
Superior oblique = trochlear (IV) •
Inferior oblique = inferior branch of occulomotor (III) •
Levator papebrae superioris = occulomotor (III) + sympathetic innervation o Sympathetic loss > partial ptosis (eyelid drooping) o Occulomotor loss > complete ptosis (eyelid closing) •
Orbicularis oculi = facial (VII) o Test by closing the patient’s eyes tightly, then open against resistance NB: The ophthalmic nerve (I) supplies sensory innervation to the cornea, ciliary body, iris, lacrimal gland, conjunctiva, skin of the eyelids, eyebrow, forehead and nose •
Tested by light/crude touch, and temperature sensation over eyelids etc 4. Describe briefly the arterial supply and venous drainage of the eye, including the retina Arterial supply to the structures in the orbit, including the eyeball, is by the ophthalmic artery. •
This is a branch of the internal carotid artery, given off immediately after the ICA leaves the cavernous sinus. •
The ophthalmic artery passes into the orbit through the optic canal with the optic nerve •
In the orbit, the ophthalmic artery initially lies infero-­‐laterally to the optic nerve (II) o As it passes forward, it crosses superior to the optic nerve and proceeds anteriorly on the medial side of the orbit In the orbit, the ophthalmic artery gives off numerous branches: •
Lacrimal •
Central retinal •
Posterior ciliary > eyeball •
Muscular arteries > intrinsic muscles •
Supra-­‐orbital > forehead + scalp •
Posterior ethmoidal > ethmoidal air cells •
Anterior ethmoidal > nasal cavity •
Medial palpebral > eyelids •
Dorsal nasal > nose •
Supratrochlear > forehead LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith Venous drainage There are two venous channels in the orbit: •
The superior ophthalmic vein – passes superiorly, exits through superior orbital fissure and enters the cavernous sinus •
The inferior ophthalmic vein – passes inferiorly, leaves posteriorly by: o Joining with superior o Passing through superior orbital fissure on its own o Passing through inferior orbital fissure to join with pterygoid plexus These serve as a route by which infection can spread through cavernous sinus to cranial cavity. 5. Identify on a skull the superior orbital fissure and the optic canal and name the nerves and vessels passing through them Optic canal: •
Optic nerve (II) •
Ophthalmic artery Superior orbital fissure: •
Occulomotor (III) •
Trochlear (IV) •
Ophthalmic branch of trigeminal (V1) •
Abducens (VI) •
Ophthalmic veins •
Sympathetic fibres Inferior orbital fissure: •
Maxillary branch of trigeminal (V2) •
Inferior ophthalmic vein •
Infraorbital vessels 6. Explain the clinical significance of the close relationship between the superior orbital fissure and the cavernous sinus The superior ophthalmic veins drain into the cavernous sinus through the superior orbital fissure, providing a potential route for the spread of infection from around the orbit, nasal sinuses and superior part of the face •
This can lead to a cavernous sinus thrombosis 7. Understand how to test corneal, light (direct and consensual) and accommodation reflexes and explain the afferent and efferent components of these The corneal or pupillary light reflex is consensual, ie light in one eye > both pupils constrict: 1) Retinal photoreceptors detect the light, and the optic nerve (CN II -­‐ sensory) transmits a signal to the pretectal nucleus 2) The pretectal nucleus then transmits impulses to the Edinger-­‐Westphal nucleus 3) At this stage, a motor signal is transmitted along the oculomotor nerves (CN III -­‐ motor) to the ciliary ganglia LCRS Anatomy of the Head, Neck & Spine Alexandra Burke-­‐Smith 4) This causes parasympathetic innervation of the pupillary sphincter which causes constriction of the pupil Procedure for testing reflex: The patient is asked to look at a distant object. A light is then shone into one eye, and the pupillary response of both eyes. •
In normal people, the pupil constricts in both eyes •
Constriction in the tested eye = good optic nerve function •
Constriction in other eye = good occulomotor nerve function Both eyes must be tested!! 8. Identify the optical and neural parts of the eye The structures of the eye can be divided into 3 main categories: muscles, optical structures and neural structures (nerves supplying the eye) The optical structures include: •
Cornea •
Iris + pupil •
Lens + ciliary muscles •
Optic retina •
Fovea/macula Nerves supplying the eye: In addition to the optic nerve (II), the nerves of the eye enter through the superior orbital fissue, and include: •
Occulomotor (III), trochlear (IV), abducens (VI) – supplying extraocular muscles (see above) •
Branches of the ophthalmic nerve (V1 = branch of trigeminal), including: o Frontal nerve o Nasociliary nerve, which divides again into: § Infratrochlear § Ethmoidal § Ciliary (long + short) 9. Outline the mechanisms of tear secretion, tear-­‐film maintenance and tear drainage The lacrimal gland is a small exocrine gland in the upper part of the orbit. It is arranged around the anterior part of the levator palpebrae superioris (divided into 2 parts) •
Parasympathetic stimulation by secretomotor fibres stimulate fluid secretion from the lacrimal gland •
The pterygo-­‐palatine ganglion contains parasympathetic post-­‐ganglionic secretomotor fibres, sending branches out from the maxillary division of the trigeminal nerve (V) •
These join with parasympathetic secretomotor fibres from the facial nerve (VII) to form the lacrimal nerve (via zygomaticotemporal nerves) •
The lacrimal nerve passes to the lacrimal gland •
Numerous ducts from the lacrimal gland open into the conjunctival sac, which empties over the eyeball o Tears pass medially over the surface to collect in the lacrimal sac (via the puncta and lacrimal canaliculi), which drains into the inferior meatus of the nasal cavity via the nasolacrimal duct