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Musculoskeletal System Parts of the Long Bone Bones of the Body Shoulder Girdle There are 7 true ribs, 5 false ribs, and 2 floating ribs. Upper Extremeties Pelvis Carpals- 8 Metacarpals- 5 Phalanges- 14 (Proximal, 5, Middle, 4, Distal, 5) Lower Extremeties Tarsals- 7 Metatarsals- 5 Phalanges- 14 (proximal, 5, middle, 4, distal, 5) Vertebral Column Cervical- 7 Thoracic- 12 Lumbar- 5 Sacral- 5 (Fuse to form the sacrum (1)) Coccygeal (2-4): fuse to form coccyx (1) Congenital and Hereditary Diseases of the Bone Achondroplasia AD Impairment of long bone formation, resulting in shorter bones. Most common cause of dwarfism (50%) Osteogenesis Imperfecta Brittle Bone Disease Improper bone formation o Defect in Type I collagen Genetic Fairly common Blue sclera Multiple fractures Osteoporosis This is accelerated bone loss. Faster than normal o Normal loss is about 1% per year after 35 years. o Normal vertebral bone is square and dense. o 1:2 females over 70 will have an osteoporotic fracture 1 in 40 males Pathogenesis o Microarchitectural deterioration of bone tissue leading to decreased bone mass and bone fragility Classification o Primary Simple, standard o Secondary Due to other conditions (hyperparathyroidism, neoplasms, tumors, malnutrition, iatrogenic, steroids) Risk Factors o Females o Age >70 years o Caucasian or Asian races o Early onset of menopause Estrogen protective o Longer menopausal interval o Inactivitiy, especially lack of weight bearing exercise o Decreased calcium o Smoking, alcohol o Decreased exposure to sun, because of decreased levels of vitamin D. Consequences o Fracture Hip (femoral neck)- most common Wrist Vertebrae Prevention Strategies o Behavior modification o Diet Calcium- 1,000 mg/day Vitamin D o Exercise Weight bearing o Decrease smoking and excessive alcohol o Inhaled vs. injested steroids Treatment o Calcium, Vitamin D (increase amounts) o (Probably not) Estrogen More risk than a benefit o Bisphonsphonates (Actonel, Fosamax) Inhibit osteoclasts that break bones o Raloxifene (SERM, Evista) SERM- selective estrogen receptor modulators Increased side effects o Calcitonin (Miacalin Nasal Spray) Hormone that decreases bone reabsorption Injection/nasal spray Bone diseases Associated with Hyperparathyroidism Effects of parathyroid hormone o Osteoclast activation with increased bone reabsorption and calcium activation. o Increased reabsorption of calcium by renal tubules o Increased synthesis of active vitamin D by kidneys, which enhances calcium absorption by the gut. Result is hypercalcemia Osteomyelitis Bone infections Pyogenic o Bacterial. Hematogenous spread or from direct surrounding. o Most common Tuberculosus o Rarer o Usually just confined to the lungs. o Pus forming (Gram + Staph/Strep) o Treatment: surgical debridement o Problem due to increased pressure. o Pox Disease- Tuberculosis in the spine Diagnosis of Acute Osteomyelitis o Pus on aspiration o Positive bacterial culture from bone or blood o Presence of classic signs and symptoms of acute osteomyelitis o Radiographic changes typical of osteomyelitis. Two of the listed findings must be present for establishment of the diagnosis Brodie’s Abcess o Pus caught in the bone. o May need surgery if bad. Most do not. Treatment o Acute hematogenous osteomyelitis 4-6 week course of appropriate antimicrobial therapy (via IV) o Chronic osteomyelitis Treated with antibiotics and surgical debridement. Paget’s Disease Aka Osteitis deformans Metabolic bone disease Elderly (3%) Subclinical In 1 or more bones Increased metabolism causes deformation Responds well to inhaled calcitonin Bone tumors Nomenclature Bone forming tumors o Benign Osteoma Slow-growing Asymptomatic Harmless if they do not obstruct anything Osteoid osteoma Tender, painful In long bones (children and young adults) See a “nidus” (<2cm) surrounded by reactive bone (causing pain). Treatment: antiinflammatories or surgery Osteoblastoma “Giant Osteoid Osteomas” Typically found in vertebrae or pelvis and larger. o Malignant Osteosarcoma Aka Osteogenic Sarcome Most common type of primary bone cancer This is a cancer of the osteoblasts The pathologist must see malignant cells making their own osteoid. Associated with retinoblastoma (on same chromosome) Arise in the shaft of long bones Results in starburst fractures Starts at the metaphysis and goes to the cortex. Usually around the knee Not too common Can extend to the soft tissue Most often seen in male adolescents. Cartilaginous Tumors o Benign Osteochondroma Aka “Exostosis” Outer branches growing off a bone Cartilage on end. Incidental finding Genetic No problem Chondroma (Enchondroma) Malignant more with genetics (Oiler’s Syndrome) Inside the bone Popcorn shaped cartilage in the bone In fingers, etc. Can occur with stress fractures Usually harmless o Malignant Chondrosarcoma After osteosarcoma, this is the 2nd most common bone tumor. Rare In pelvis of middle-aged men. Slow growing Painful See bone destruction, calcification, and tumor Other tumors and tumor-like conditions o Giant cell tumor Myeloma 4th most common Aggressive Multibucleated giant cells Tumor of the osteoclasts (destructive cells) More lytic Also found near the knee o Ewing’s Tumor 3rd most common In cortex In diaphysis Younger population Aggressive Fast/ painful Almost only Caucasians Can metastasize With early detection, 5 year survival rate is 80%. Less with metastasis Onion skinning- diagnostic “Moth eaten” Fibrous Dysplasia Bone replaced with fibrous tissue Abnormally decreased strength Diseases of the Joints Anatomy o These are between the bones o Joint capsule Lined with synovium (has vasculature) Secretes hyaluronic acid (lube) and used as nutrition Fluid comes and goes very easily Osteoarthritis o Most common joint disorder o Clinical features Symptoms Joint pain Morning stiffness lasting less than 30 minutes Joint instability or buckling Loss of function Signs Bony enlargement at affected joints Limitation of range of motion Crepitus on motions- joints make noises Pain with motion and morning stiffness Malalignment and/or joint deformity. Heberdan’s Nodes o On distal fingers Osteophyte formation restricts movement Pattern of Joint involvement Axial: cervical and lumbar spine Peripheral: distal interphalangeal joint, proximal interphalangeal joint, first carpometacarpal joints, knees, hips Avascular necrosis A cuase of secondary arthritis due to decreased blood supply Death of tissue Gout o o o o o o o From trauma or steroids Because it is avascular, it is hard to repair. Slowly progressive Noninflammatory (just due to wear and tear) Seen in weight-bearing joints and small joints of hands and feet. Seen in an x-ray as a narrowing of the articular space (covers bones/not seen on x-ray) Treatment Nonpharmacologic management o Patient education o Exercise (stimulate synovium) o Assistive devices (cane) o Weight management o Supplements (glucosamine) Surgery Pharmacologic Treatments o Simple analgesics Tylenol o NSAIDs Ibuprofen o Local analgesics Menthol Intra-articular corticolsteroid injections o Intra-articular injections of hyaluronic acid like products Increased lubrication for 6 months Deposition of uric acid crystals in joints Increased serum uric acid levels, or can precipitate Pain, redness, inflammation Kidney stones Classic location- the big toes Monoarticular- involves 1 joint Increased risk Males, overweight, follows alcohol intake, foods with nitrates o Clinical presentation Acute gouty arthritis Red, hot, uncomfortable Interval gout (subacute) Tophaceous gout (uric acid globs in soft tissue, called tophi) Tophi seen on ligaments, tendons, and around joints. Renal manifestations o Diagnose with fluid extraction Aspirated synovial fluid looks like crystals. No bacteria is seen. o Treatment Acute gouty arthritis NSAIDs Colchicines Corticosteroids Prevention of recurrent attacks Uricosuric Drugs (Probenicid) o Makes you pee out all of the uric acid. Decrease uric acid production o Allopurinol Colchicine The goal is to decrease serum uric acid levels. This prevents kidney problems, tophi, and bone destruction. Infective arthritis o Septic/suppurative o Due to trauma, gonorrhea, hematogenous spread, etc. o Bacteria changes the cartilage quickly, so aspiration and diagnosis should be done fast. Rheumatoid Arthritis Autoimmune, inflammatory arthritis Abrupt onset Associated with Sjogren’s Syndrome, episcleritis, carditis, pleuritis, hepatitis, and vasculitis Swan deformity with RA Boutonniere’s Deformity- opposite of swan neck Diagnostic criteria (Need 4) o Morning stiffness lasting longer than 1 hour before improvement o Arthritis involving 3 or more joints (and other systems) o Arthritis of the hand, particularly involvement of the proximal interphalangeal (PIP) joints, metacarpophalangeal (MCP) joints, or wrist joints. o Bilateral involvement of joint areas (ie both wrists, symmetric PI P and MCP joints o Positive serum rheumatoid factor (RF) Not seen immediately o Rheumatoid nodules o Radiographic evidence of RA Destruction/deformation of bone Soft Tissue Tumors Very rare Tumors of Adipose Tissue o Lipoma Most common Benign Slow Mature fat cells in subcutaneous tissue Nonmobile (skin around it moves) Normally 1-2cm Treatment: removal. o Liposarcoma Rapid, fixed, painful Tumors of fibrous tissue o Nodular fascitis o Fibromatoses o Fibrosarcomas Fibrohistiocytic tumors o Fibrous histiocytoma o Dermatofibrosarcoma Protuberans o Malignant Fibrous Histiocytoma 2nd most common Neoplasms of skeletal muscle o Rhabdomyosarcoma Synovial sarcoma The Skull The skull consists essentially of 2 principal parts o The cranial portion which forms the brain case o The facial portion forming the framework for the eyes, nose, and mouth. Cranial Bones o Frontal- front and upper part of the forehead o Parietal- forms roof and sides of the cranium o Occipital- forms dorsal part of the cranium o Temporal- forms sides and part of floor of cranium o Sphenoid- forms anterior floor of cranium Body- sella turcica Greater wing Foramen rotundum Foramen ovale Foramen spinosum Lesser wing- anterior clinoid processes o Ethmoid- posterior to the lacrimal bone, medial. Facial Bones o Nasal- forms upper portion of nose o Lacrimal- anterior medial wall of orbit o Palatine- forms upper palate of the mouth o Zygomatic- forms cheekbone o Mandible- forms lower jaw o Maxillae- forms upper jaw o Inferior nasal conchae- forms part of lateral wall of nasal cavity o Vomer- forms lower posterior part of nasal septum Sutures o o o o o o Fossa Coronal- frontal and parietal Sagittal- parietal to parietal Squamousal- parietal to temporal Lambdoidal- parietal to occipital Bregma- junction of coronal and sagittal sutures Lambda- junction of sagittal and lambdoidal sutures o Temporal fossa Bound above and behind by the temporal bones, in front by frontal and zygomatic bones, and below by infratemporal crest. Houses the temporalis muscle. Communicates inferiorly with infratemporal fossa Pterion Sutural landmark Intersection of squamosal and parietosphenoid sutures. o Infratemporal fossa Bound in front by maxilla, above by great wing of the sphenoid, and below by the border of the maxilla. Inferior to temporal fossa and posterior to zygomatic arch. Communicates with orbit via inferior orbital foramen. Houses the mastication muscle. o Pterygopalatine fossa Bound above by body of the sphenoid, in front by maxilla, and behind by the greater wing of sphenoid. Located inferior and posterior to apex of orbit. Communicates directly with orbit via inferior orbital foramen. Communicates with the middle cranial fossa via the foramen rotundum and foramen lacerum. o Interior Skull Cranial Fossa Anterior Cranial Fossa Bound anteriorly and laterally by the frontal bone and posteriorly by the lesser wing of the sphenoid. Middle Cranial Fossa Bound anteriorly and laterally by the frontal bone and posteriorly by the greater wing of sphenoid. Posterior Cranial Fossa Bound anteriorly by the dorsum sellae and occipital bone laterally by the parietal bone. Jugular Fossa Anterior and temporal to the occipital condyle Foramina Foramen Anterior Ethmoid Cribiform Plate Posterior Ethmoid Optic Canal Pituitary Fossa (Hypophyseal Fossa) Within the pituitary gland. Cranial Fossa Anterior Anterior Anterior Middle Superior Orbital Fissure Middle Foramen Rotundum Foramen Ovale Middle Middle Foramen Spinosum Middle Foramen Lacerum Middle Carotid Canal Internal Acoutic Meatus Middle Posterior Jugular Foramen Posterior Hypoglossal Canal Foramen Magnum Posterior Posterior Stylomastoid Foramen Posterior Temporo-Mandibular Joint Contents Anterior ethmoidal A, V, N Olfactory nerve bundles Posterior ethmoidal A, V, N Optic Nerve (II) Ophthalmic A Ocularmotor N (III) Trochlear Nerve (IV) Lacrimal branch of V1 Frontal branch of V1 Nasociliary branch of V1 Abducens N (VI) Superior ophthalmic Maxillary N Mandibular N (V3) Accessory Meningeal A Lesser petrosal N (occasionally) Middle meningeal A and V Meningeal branch of V3 Internal Carotid A Internal carotid N plexus Internal Carotid Facial N (VII) Vestibulocochlear N (VIII) Int. auditory A Inf. Petrosal sinus Glossopharyngeal N (IX) Vagus N (X) Accessory N (XI) Sigmoid sinus Post. Meningeal A Hypoglosal N (XII) Medulla oblongata Meninges Vertebral As Meningeal branch of vertebrals Spinal roots of accessory N Facial N o Joint by which the mandible is connected to the skull. o Only synovial joint in the skull. o Enclosed in an articular capsule. Has an articular disc that divides the joint into two cavities. A synovial membrane surrounds each cavity. o Support to the joint is via special ligaments. Surface of the Cranium o The bones which form the roof and walls of the cranium are marked off by well-defined sutures. o The frontal bone forms the forehead, and the part forming the eyebrows is known as the supraorbital margin. The bone contains a hollow, air-filled space, the frontal sinus, which communicates with the cavity of the nose. o The parietal bones (considered to be bilaterally paired) form the principal part of the roof and sides of the brain case. They are divided from the frontal bone by the coronal suture. o The occipital bone forms the posterior wall. On its inferior aspect it contains a large opening, the foramen magnum, through which the spinal cord passes. On either side of this opening is a pair of smooth articulating surfaces, the occipital condyles, which rest on the vertebral column. o On the sides of the skull, inferior to the parietals, and between the frontal and occipital bones, lie the paired temporal bones. The inner and middle ear are imbedded in this bone, which presents a prominent opening, the external auditory meatus for the passage of the ear canal. Posterior to this opening, is a prominent projection, the mastoid process, whose spongy interior is sometimes the site of infection. The concavity into which the lower jaw articulates is the mandibular fossa. The slender arch which passes from this articulation to the orbit is the zygomatic arch, whose posterior portion is formed by the zygomatic process of the temporal bone. On the floor of the cranium, between the anteriorly directed extensions of the occipital and temporal bones, lies an elongated irregularly shaped opening, the jugular foramen, through which pass the sinuses draining into the jugular vein, and the 9th and 10th cranial nerves as well. Just lateral to this is a projection, the base of the long slender styloid process which is usually broken off. Just anterolateral to the jugular foramen, at the base of the styloid process, is a large foramen directed anteriorly, the aperture of the carotid canal, through which the internal carotid passes on its way to the brain. This canal turns medially and courses through the petrous portion of the temporal bone emerging above the foramen lacerum in the interior. Just posterior to the styloid process and just medial to the mastoid process, is the small stylomastoid foramen which transmits the facial nerve as it emerges from the cranium. Anterior and medial to the styloid process is the small foramen spinosum. A straight line can be drawn through the stylomastoid foramen, styloid process and foramen spinosum. o The central portion of the floor of the crainium is formed by the rather complicated sphenoid (wedge-shaped) bone. It has a pair of “greater wings” (alisphenoid) which may be seen on the lateral surface extending superiorly up to the border of the parietal bone, and thus separating the temporal bone from the frontal bone. Its central “body” lies on the floor of the cranium in the mid-line, where processes from the temporal and occipital bones extend forward to meet it. Its pterygoid processes (lateral and medial) are a pair of prominent, inferiorly directed projections, extending from the root of the “wings” down to the roof of the mouth (palate). Between these lies the posterior choanae through which the nasal passages pass to communicate with the pharynx. o The septum dividing these opening s (nasal septum) is comprised largely of the vomer (plowshare) bone, whose base extends back between the pterygoid processes, thus compressing the body of the sphenoid into a relatively narrow strip at its interior surface. o The vomer conceals the bone forming the floor of the cranium along the anterior mid-line. This is the ethmoid bone which forms the roof and most of the walls of the nasal cavity. o On the roof of the orbit, on either side of the ethmoids along their posterior border, may be seen another pair of anterior extensions from the sphenoid bone, the lesser “wings,” which make up the remainder of the floor of the crainium. The optic foramen passes through these processes. It carries the ophthalmic artery as well as the optic nerve, into the orbit. The large space between the greater and lesser wings of the sphenoids constitute the supra-orbital fissure, which extends inferiorly into the infraorbital fissure. Interior of the Cranium o The composition of the walls of the cranium should be further clarified by studying its surface from the interior. On the superior surface will be seen a prominent shallow mid-line groove between the parietals which marks the position of the superior sagittal venous sinus of the dura mater. On the posterior surface of the cranium the superior saggital venous sinus leads to a straight groove, the transverse sinus which leads to an s-shaped groove, the sigmoid sinus and the to the jugular foramen. Other grooves indicate the position of arteries supplying the membranous covering of the brain. Prominent ridges on the floor of the cranium make it divisible into three principal fossae. The anterior cranial fossa contains the frontal lobes of the brain. Its posterior boundary is marked by the posterior edge of the lesser wings of the sphenoids, which form the prominent sphenoidal ridge. The large sphenoid sinus is contained within the body of this portion of the sphenoid bone. In the mid-line, anterior to the phenoid, lies the superior surface of the ethmoid bone. The numerous perforations for the filaments to the olfactory nerve (passing from the nasal membranes to the olfactory bulbs), have given this surface the name of cribiform plates, separated in the mid-line by a projection known as the crista galli (Cock’s comb). Directly anterior to this process is an opening which usually ends blindly, the foramen caecum. The middle cranial fossa contains the temporal lobes and the anterior portion of the brain stem. The central raised portion in the mid-line is the sella turcica containing the fossa hypophysea which is the repository for the pituitary gland. Anterior to the ridge of this saddle-shaped structure is a flat, smooth surface, the jugum of the sphenoid, which extends laterally on either side as the slender anterior clinoid processes, tapering out along the inferior surface of the lesser wings of the sphenoid. The optic foramina lie between these two processes of the sphenoid. A groove is seen on the anterior surface of the sella turcica. This is the chiasmatic groove. The superior orbital fissure may be easily identified between the wings of the sphenoid. The posterior boundary of the middle cranial fossa is marked by the enlarged petrous portion of the temporal bone, which houses the inner ear. At the inferior edge of the anterior surface of this prominence is an obliquely situated irregularly shaped opening, the foramen lacerum, over which passes the internal carotid artery, after it emerges from the carotid canal. In life the foramen lacerum is filled with cartilage. The internal carotid passes along either side of the sella turcica in the carotid grooves and then turns superiorly within a groove on the posterior surface of the anterior clinoid process (this groove is occasionally completely closed over to surround the artery), and thereupon enters into the foramen of the circle of Willis around the stalk of the pituitary The large foramen passing directly through the floor of the fossa is the foramen ovale, and transmits the mandibular branch of the trigeminal nerve. Anterior and medial to the foramen ovale, and just inferior to the supra-orbital fissure, is the anteriorly directed foramen rotundum, which carries the maxillary branch of the trigeminal nerve. The posterior cranial fossa contains the cerebellum and the medulla. The position of the pons is indicated by the portion of the occipital bone lying anterior to the foramen magnum. Note again the foramen magnum and the jugular foramen. In addition, note the prominent internal auditory meatus on the posterior surface of the petrous temporal. Both the 7th and 8th nerves leave the cranium by way of this opening. After passing laterally for a short distance, the 7th turns abruptly posteriorly into the facial canal (imbedded in the bone and therefore not visible from the surface) which emerges through the stylomastoid foramen. Facial Portion of the Cranium o The facial portion of the skull consists of the bones which surround four principal cavities, the two orbits, the nose, and the mouth. o The orbit is formed by parts of the seven different bones. Its roof and superior margin is formed by the frontal bone. The supraorbital margin present a notch or foramen of the same name (for the passage of vessels and nerves of the same name). Sometimes a second less marked notch is present, medial to the supraorbital, the frontal notch. The medial portion of the supraorbital margin is smoothly rounded along the nasal part of the frontal bone. This portion of the supraorbital margin may present on its inner surface, the small fovea trochlearis (occasionally a small spine), marking the site of the cartilaginous pulley for the tendon of the superior oblique muscle. Laterally, the supraorbital margin is sharp and extends along the strong prominent zygomatic process of the frontal bone. Under o o o o the lateral edge of this margin, within the orbit, is the shallow lacrimal fossa for the lacrimal gland. It may be best identified by touch. The roof of the orbit is formed by the thin orbital plates of the frontal bones (which also form the floor of the anterior cranial fossa). Hold the skull up to the light to see the thinness of the roof. Posteriorly, the roof of the orbit is formed by the lesser wing of the sphenoid, through which the optic foramen passes. The lateral wall of the orbit is formed anteriorly by the zygomatic bone (cheek bone), and posteriorly by the greater wing of the sphenoid. The zygomatic bone, together with the zygomatic process of the temporal bone, forms the zygomatic arch through which passes the temporal muscle. The zygomatic bone articulates superiorly with the zygomatic process of the frontal bone, forming a strong protective bulwark on the most exposed area of the orbit. Slightly below the fissure of articulation, within the orbit, is the variable lateral orbital tubercule, for the attachment of muscle and ligaments. In the middle of its orbital surface is the zygomatico-facial foramen, and on the surface within the arch is the zygomatico-temporal foramen. Posteriorly the zygomatic bone articulates with the greater wing of the sphenoid which forms the remainder of the lateral wall of the orbit, separating the orbit from the middle cranial fossa. Medially, the zygomatic bone contributes to the floor of the orbit and articulates with the maxillary bone, the fissure between the two bones running laterally at a sharp angle. The medial wall of the orbit is made up of the paper thin lamina papyracea of the ethmoid bone and the lacrimal bones. The lamina papyracea separates the orbit from the sinusoidal air cells of the ethmoid bone. Along the fissure between the lamina papyracea and the orbital plates of the frontal bone may be a series of openings, the most prominent of which are the anterior and posterior ethmoid canals. The lamina papyracea articulates posteriorly with the body of the sphenoid, inferiorly with the maxilla, and anteriorly with the lacrimal bone. The latter is the smallest and most fragile bone of the skull. The posterior part of the lacrimal bone forms the lacrimal groove, bounded posteriorly by the posterior lacrimal crest of the lacrimal bone. The lacrimal groove is continuous anteriorly with the lacrimal notch of the maxillary, bounded anteriorly by the anterior lacrimal crest. Together, the lacrimal groove and the lacrimal notch form the lacrimal fossa which contains the lacrimal sac and deepens as it passes inferiorly into the nasolacrimal duct. superiorly, the lacrimal bone articulates with the frontal bone, anteriorly with the frontal process of ther maxilla, and inferiorly with the orbital plate of the maxilla and with the lacrimal process of the inferior nasal conchae. There may be a small lacrimal tubercle on the infra-orbital margin just below the lacrimal fossa. The floor of the orbit is mostly made up of the orbital plate of the maxilla, also receiving a contribution laterally from the zygomatic bone. The orbital plate of the maxilla is relatively thin, and separates the orbit from the large maxillary sinus (antrum of Highmore). Below the infraorbital margin, the prominent infraorbital foramen is located. Its posterior continuation may reappear in the floor of the orbit as the infraorbital groove. The posterior corner of the floor of the orbit is formed by the orbital process of the palatine bone, which extends superiorly between the maxilla and the pterygoid processes of the sphenoid to reach to the orbit. The lateral part of the infraorbital margin is formed by the zygomatic bone. Its medial part is formed by the maxilla, principally by its superiorly directed frontal process. Most of the structures mentioned in the margins and inner rim of the orbit can be palpated with the finger tip. o Posteriorly, the orbit receives blood vessels and nerves through two large slits. The supraorbital fissue, roughly comma-shaped, lies vertically between the greater and lesser wings of the sphenoid, and contains structures passing from the middle cranial fossa to the orbit (the branches of the ophthalmic division of the 5th nerve, the nerves to the eye muscles, the ophthalmic vein, and some small arteries). About midway along its lateral margin may be found the small spine of the lateral rectus. o The infraorbital fissure, lying horizontally between the greater wing of the sphenoid, the orbital plate of the maxilla, its expanded anterior portion being bounded by the zygomatic. It contains structures passing to the orbit from the infratemporal fossa (just below the wing of sphenoid) and the pterygo-palatine fossa (between the pterygoid process of the sphenoid and the orbital process of the palate). These include the infra-orbital artery and vein, the infraorbital and zygomatic branches of the maxillary nerve, and branches from the inferior ophthalmic vein. o The mouth cavity is formed by the upper and lower jaws and the palate. The lower jaw consists of the mandible, which has a horizontal body which bears the teeth, and a posterior ramus for muscle attachment and articulation with the skull. A noticeable process, the coronoid process extends superiorly from the ramus. On the inner surface of the angle where body and ramus join is the mandibular foramen which receives the inferior alveolar branch of the mandibular nerve. This nerve emerges at the front of the chin through the mental foramen. o The upper jaw is formed by the maxilla. The maxilla has an alveolar process which bears the teeth, and the anterior facial surface, zygomatic and frontal processes, an orbital surface, a palatine process, and a nasal surface. The palatine processes of the maxillary and palatine bones form the roof of the mouth and the floor of the nasal cavities. o The anterior part of the roof of the nasal cavity slanting downward, consists of the two small flat nasal bones, situated on either side of the midline between the frontal processes of the maxillary bone. They articulate superiorly with the frontal bone, which sends a sharp spine between them on the inner surface of the nasal cavity. o The middle horizontal portion of the roof of the nasal cavity is formed by the cribiform plate of the ethmoid. Posteriorly, the roof again slants downward, being formed by the body of the sphenoid principally and small parts of the adjacent bones (vomer, palatine). The lateral walls are formed anteriorly by the maxilla and lacrimal bones, in the middle by the ethmoid superiorly, and the maxilla inferiorly, and posteriorly by the vertical part of the palatine bones and the pterygoid processes of the sphenoid. The medial septum is formed superiorly by the vertical plate of the ethmoid, and inferiorly by the vomer. The lateral walls give rise to the three conchae or turbinates, the superior and middle arising from the ethmoid and fusing anteriorly, the inferior deriving from the maxilla and becoming a separate bone. Beneath each turbinate lies an air passage, the superior, middle, and inferior meatus respectively, and it is into the latter that the nasolacrimal duct opens, after passing through the maxillary bone. The nasal cavity communicates with the paranasal air sinuses of the sphenoid, maxillary, ethmoid, and frontal bones.