Download דיסקציות עשרים ועשרים ואחת – הצוואר

‫דיסקציות עשרים ועשרים ואחת – הצוואר‬
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Cervical bones
The hyoid bone (Moore 8.3, Sobotta 198, 199):
- Named for being shaped like the letter 
- Has a body, greater and lesser horns
- Located at the level of C3
- Attaches (this is a summary, so don't panic. The details are below):
o to the styloid process by the stylohyoid ligament and muscle
o to the mandible by the mylohyoid muscles and the geniohyoid
muscles
o to the mandible and mastoid process by the digastric muscle
o to the sternum by the sternohyoid muscle
o to the thyroid cartilage by the thyrohyoid muscle
o to the clavicle and scapula by the omohyoid muscle
o to the tongue by the hyoglossus muscle
Large cervical muscles (Netter 22, 23)
Platysma:
- Subcutaneous, within the superficial cervical fascia
- From the deltoid and pectoral fascia to the facial muscles above chin
- Acts as a muscle of facial expression on skin of neck and chin
- Innervated by the cervical branch of C.N. VII.
Sternocleidomastoid (SCM):
- Within investing layer of deep cervical fascia
- From the manubrium and medial third of clavicle to mastoid process
- The external jugular vein is external to it. The internal jugular vein is
internal to it (Netter 57, Sobotta 272).
- Acts to bend the neck (uni- or bi-laterally); acts as an accessory respiration
muscle (watch it in the physiology labs as people breathe really deeply).
- Innervated by C.N. XI.
Trapezius:
- Within investing layer of deep cervical fascia
- From superior nuchal line, external occipital protuberance, nuchal
ligament to lateral third of clavicle, scapula.
- Functionally belongs to muscles of the upper limb, as acts on scapula.
- Innervated by C.N. XI.
To describe the neck better we will define the anterior and posterior triangles, then the
divisions of each triangle, and then the contents of each triangle separately.
Anterior triangle (Netter 24)
Anterior border
neck midline
Posterior border
anterior border of SCM
Superior border
Apex
Roof
Floor
-
inferior border of mandible
jugular notch
skin and subcutaneous fascia with platysma
pharynx, larynx, thyroid gland
It is divided into four smaller triangles - two above the hyoid, two below the hyoid, in
the following way:
- The submandibular triangle is the superolateral triangle, its sides being
the inferior border of the mandible and the two bellies of the digastric
muscle.
- The submental triangle is the superomedial triangle above the hyoid, its
sides being the hyoid bone and the anterior bellies of the left and right
digastrics. (Note that this triangle is unpaired because it crosses the
midline).
- The carotid triangle is the inferolateral area below the submandibular
triangle, its sides being the superior belly of the omohyoid in front, the
posterior belly of the digastric above and the SCM behind.
- The muscular triangle is the inferomedial area, its sides being the neck
midline, the superior belly of the omohyoid and the anterior border of the
SCM.
* Note that these small triangles are NOT called the superolateral triangle, the
inferomedial triangle, etc. This is just my way of explaining their location within the
anterior triangle.
Posterior triangle (Netter 23)
Anterior border
posterior border of SCM
Posterior border
trapezius
Inferior border
clavicle
Roof
skin and subcutaneous fascia with platysma
Floor
prevertebral fascia covering the muscles splenius
capitis, levator scapulae, scalene muscles.
The posterior triangle is also subdivided into smaller triangles, this time by the
posterior belly of the omohyoid muscle:
- The occipital triangle is above the posterior belly of the omohyoid.
- The supraclavicular triangle (subclavian) is below it.
Contents of the posterior triangle
Muscles:
- Splenius capitis (Netter 23, 167):
o Most superior muscle in the floor of the posterior triangle
o The "bandage" of the head (SPLeNium = ‫)אספלנית‬
o From the mastoid process to the inferior part of the nuchal
ligament, connecting to the splenius cervicis
- Levator scapulae (Netter 23):
o Inferior to the splenius capitis
o From the posterior tubercles of the lateral processes of C1-C4 to
the medial border of the scapula
o Helps rotate and elevate the scapula
- Posterior scalene (Netter 23, 26):
-
-
o Inferior to the levator scapulae
o From the posterior tubercles of C4-C6 to the second rib
Middle scalene (Netter 26, 26):
o Inferoanterior to the posterior scalene
o From the transverse processes of C2-C7 to the first rib
o Brachial plexus lies anterior to it
Anterior scalene (Netter 26, 26):
o At the very medial edge of the triangle, almost entirely behind
SCM
o From transverse processes of C3-C6 to scalene tubercle on first rib
o Phrenic nerve emerges and lies anterior to it
o Brachial plexus and subclavian artery are posterior to it, lying on
the first rib
Arteries (Netter 29):
- Subclavian artery:
o Runs across the floor of the subclavian triangle of the posterior
triangle.
o Its branches include the vertebral artery, the internal thoracic
artery, the thyrocervical and the costocervical trunks.
o Anterior scalene is anterior to it
o First rib is inferior to it
o Brachial plexus is posterior to it
- Suprascapular artery:
o First branch of the thyrocervical trunk
o Passes in the lower part of the subclavian triangle across (anterior
to) the phrenic nerve and the anterior scalene
o Passes posteriorly through the brachial plexus to supply scapular
muscles
- Transverse cervical artery:
o Second branch of the thyrocervical trunk
o Located superior to the suprascapular artery
o Passes anterior to the phrenic nerve
o Crosses anterior to or through the brachial plexus
o Divides into a superficial branch that supplies the trapezius muscle
and a deep branch that supplies the rhomboides
- Occipital artery (Netter 65):
o From the external carotid (NOT the subclavian)
o Originates superior to the origin of the facial artery, from the
posterior aspect of the external carotid. Passes deep to the
hypoglossal nerve (C.N. XII) but superficial to C.N.'s IX, X, XI,
the sympathetic trunk and the internal carotid.
o Enters occipital triangle at the very apex and branches out on
posterior part of scalp
Veins (Netter 27):
- Subclavian vein (Netter 29):
o Drains upper limb
o Located anterior to its artery
-
o Located anterior to the anterior scalene, so from superficial to deep
it's subclavian vein, then anterior scalene and phrenic nerve, then
subclavian artery
o Receives EJV
o Receives IJV to form the brachiocephalic vein
External jugular vein:
o Formed by the union of the posterior division of the
retromandibular and the posterior auricular veins.
o Lies in a plane superficial to the investing layer of the deep cervical
fascia until it pierces it at the anteroinferior part of the triangle.
Thus, it is superficial to the SCM (but deep to the platysma)
o Drains into subclavian vein after receiving the transverse cervical
and the suprascapular veins (which travel with arteries), as well
as the anterior jugular vein.
Nerves
- Brachial plexus (Netter 28):
o Comprised of C5-T1
o Supplies upper limb
o Located on the floor of the subclavian triangle
o More on it when we get to the upper limb
- Suprascapular nerve (Netter 412):
o Emerges from the brachial plexus on the floor of the subclavian
triangle
o Runs laterally to supply muscles on the back of the scapula
- Accessory nerve (C.N. XI) (Netter 28):
o Emerges from underneath the SCM 1/3 the way down from its top
after supplying it. Before emerging it lies superficial to the IJV
under the SCM.
o Disappears below the anterior border of the trapezius
o Supplies the SCM, trapezius
- Greater auricular nerve (Netter 28, Sobotta 259):
o C2-C3
o Supplies skin over parotid, posterior auricle
o Wraps around SCM to climb to area of distribution
- Lesser occipital nerve (Sobotta 259):
o C2
o Supplies neck and scalp posterosuperior to auricle
o Wraps around SCM to climb to area of distribution
- Transverse cervical nerve (Netter 27, Sobotta 259):
o C2-C3
o As this nerve supplies skin over the anterior triangle it wraps
around the SCM and crosses to the anterior triangle under the EJV
- Supraclavicular nerves (Sobotta 259):
o C3-C4
o As their name implies, they travel inferiorly on the roof of the
triangle to supply skin on, lateral to, and somewhat beneath the
clavicle.
(*Note that the greater auricular, the lesser occipital, the transverse cervical and the
supraclavicular nerves all emerge at the nerve point of the neck – around the
midpoint of the posterior border of the SCM. These nerves are the posterior branches
of cervical plexus (C1-C4), located on the levator scapulae and middle scalene, deep
to the SCM. The anterior branches of the plexus form the ansa cervicalis, supplying
the infrahyoid muscles.)
- Phrenic nerve:
o C3-C5 (C3, 4 and 5 keep the diaphragm alive...)
o Emerges on the lateral border of the anterior scalene
o Descends on the anterior scalene, deep to the transverse cervical
and suprascapular arteries.
o Enters thorax on the medial side of the anterior scalene
Lymph
The superficial cervical lymph nodes lie along the EJV, communicating with
the deep cervical lymph nodes lying along the IJV.
Contents of the anterior triangle
The two muscles dividing the anterior triangle are the digastric muscle (so
called because it has two bellies) and the omohyoid muscle (so called because it
passes from the hyoid to the omos – shoulder). We will describe them here and then
discuss each triangle separately.
The anterior belly of the digastric originates on the digastric fossa on the
inside of the mandible (Netter 13). Is passes to the hyoid bone, where it becomes the
intermediate tendon, attached to the hyoid by a sling made of deep cervical fascia, a
sling which allows the muscle to move freely. The tendon then thickens to form the
posterior belly of the digastric, which inserts on the mastoid notch of the temporal
bone, deep to the SCM.
Note: - the posterior belly passes through the stylohyoid muscle, which
splits before attaching to the hyoid, to allow the digastric to pass through it.
- the anterior belly is supplied by C.N. V, while the posterior belly is
supplied by C.N. VII, due to different embryological origins.
The omohyoid muscle also has two bellies. Its superior belly originates on the
hyoid bone (between the thyrohyoid laterally and the sternohyoid medially) and
passes inferiorly and somewhat laterally, anterior to the external carotid and the IJV.
It becomes the intermediate tendon which attaches to the clavicle by a fascial sling,
then thickens to form the posterior belly which passes posteriorly superior to the
brachial plexus, the suprascapular vein and the subclavian vessels (but inferior to the
transverse cervical vein) to insert on the superior border of the scapula. Being an
infrahyoid muscle it is innervated by a branch of the ansa cervicalis.
Contents of triangles:
1. Submandibular triangle (Sobotta 262):
Muscles:
- mylohyoid – from the mylohyoid line of the mandible
to mylohyoid raphe and the body of the hyoid, this muscle lies on top
of the digastric, forming the floor of the mouth.
- hyoglossus – from the body of the hyoid, this muscle
rises up to insert on the side of the tongue.
- the middle pharyngeal constrictor, originating on the
lesser and greater horns of the hyoid, is the third muscle in the floor of
this triangle.
Vessels (Netter 27, 65, 66): - after the lingual artery branches off
the external carotid it passes deep to the hypoglossal nerve, the
stylohyoid, the posterior belly of the digastric and the hyoglossus.
After passing the hyoglossus it becomes the deep lingual and
sublingual arteries.
- the facial artery travels through the triangle before
ascending on the mandible. It arises after the lingual artery (or together
with it) and passes below the stylohyoid and the posterior belly of the
digastric, lying on the submandibular gland.
- the tonsillar artery, a branch of the facial artery
ascends superficial to the styloglossus muscle to pierce through the
superior pharyngeal constrictor to supply the tonsil.
- the ascending palatine artery, another branch of the
facial, passes deep to the styloglossus, also piercing the buccinator to
supply the palate.
- the facial vein takes a similar path, draining into the
anterior division of the retromandibular vein.
- the submental vessels branch from the facial vessels
at the level of the gland, traveling along the inferior border of the
mandible, anastomosing with the mental vessels (branches of the
inferior alveolar vessels) exiting at the mental foramen.
Nerves (Netter 67): - the hypoglossal nerve (C.N. XII) enters the
triangle deep to the digastric and stylohyoid and superficial to the
hyoglossus, to supply muscles of the tongue.
- the nerve to mylohyoid, a branch of the inferior
alveolar nerve (a branch of V3) is in the triangle, to supply the
mylohyoid and the anterior belly of the digastric.
Others (Netter 56, 57):
- the submandibular gland occupies
most of the triangle, "hugging" the mylohyoid. The submandibular
duct exits on it superior surface, passes under the tongue and opens at
the sublingual papilla, near the frenulum of the tongue.
- submandibular lymph nodes are found around the
gland and along the inferior border of the mandible.
2. Submental triangle (Netter 27):
Muscles:
- the two mylohyoid muscles meet here at the median
fibrous raphe. Deeper to it are the geniohyoid and the genioglossus
muscles (we will meet them later when discussing the tongue).
Vessels:
- small are found here, forming the anterior jugular vein
in the muscular triangle.
Others:
- submental lymph nodes.
3. Carotid triangle:
Muscles:
- the anterior scalene is found in the depths of the
triangle
Vessels (Moore 8.12, Netter 65): - the common carotid artery
ascends into this triangle, dividing at the level of the superior border of
the thyroid cartilage to the internal and external carotids. The
carotid body, a chemoreceptor monitoring oxygen levels in the body,
is found at the bifurcation site. The internal, and perhaps the common,
carotid enlarges to form the carotid sinus, a baroreceptor monitoring
blood pressure. The common (and later – the external) carotid, the
internal jugular vein and the vagus nerve are bound together in the
fascial carotid sheath. The external carotid has branches in the neck
and is the more anterior of the two. The internal carotid branches only
in the head and brain and is more posterior.
- the superior thyroid artery, a branch of the external
carotid, originates in the triangle, passing anteroinferomedially to
supply the thyroid gland. It also gives off the superior laryngeal artery.
The superior thyroid vein follows a similar course, draining to the
IJV.
- the ascending pharyngeal artery branches off the
posterior aspect of the external carotid at the level of the superior
thyroid artery. It ascends to supply the pharynx, prevertebral muscles,
middle ear, meninges.
- the inferior thyroid artery (Moore 8.19), the largest
(and terminal) branch of the thyrocervical trunk, ascends posterior to
the carotid sheath, then crosses medially to reach the thyroid.
- the ascending cervical artery is the other terminal
branch of the thyrocervical trunk. It branches off along with the
inferior thyroid, lies posterior to the carotid sheath and supplies deep
lateral neck muscles.
- the IJV (Netter 66) is found lateral to the internal and
then to the common carotid, wrapped together with it in the carotid
sheath. The IJV drains most of the blood from the brain, face and
cervical viscera, terminating between the two heads of the SCM by
draining into the subclavian vein, which thus changes its name to
brachiocephalic vein.
Nerves:
- the vagus nerve (C.N. X), also contained within the
carotid sheath, lies posterior to both the carotid artery and the IJV.
- the ansa cervicalis is embedded on the carotid sheath.
- the sympathetic trunk is posterior to the sheath.
Others:
- the deep cervical lymph nodes line the IJV.
4. Muscular triangle (Netter 25:
Muscles:
- the sternohyoid muscle, from the manubrium and
clavicle, is the most medial muscle.
- the sternothyroid muscle, just deep to the
sternohyoid, is between the manubrium and the oblique line of the
thyroid cartilage.
- the thyrohyoid is a continuation of the sternothyroid,
running from the oblique line of the cartilage to the hyoid bone.
* Note that collectively the sternohyoid, the sternothyroid, the thyrohyoid and the
omohyoid (discussed earlier) are called the strap muscles, for their narrow
appearance. The thyrohyoid is innervated by C1 via the hypoglossal. The rest are
supplied by branches of the ansa cervicalis.
Vessels:
- the inferior thyroid veins (Netter 70) lye in the floor
of the triangle, draining the inferior parts of the thyroid directly into the
brachiocephalic veins posterior to the manubrium. The thyroid arteries ascend more
laterally, within the carotid triangle, as branches of the external carotid and the
thyrocervical trunk.
- the anterior jugular vein (Netter 27) arises from the
combination of many superficial submental veins. The vein descends anywhere
between the midline and the anterior border of the SCM. At the root of the neck the
vein turns laterally, posterior to the SCM, to drain into the EJV or the subclavian vein.
The two anterior jugulars communicate through the jugular venous arch above the
manubrium in a space created by the splitting of the fascia around the two SCM's.
- a communicating jugular vein may be found
connecting the EJV and the anterior jugular.
- a thyroid ima artery may be present, climbing up on
the trachea from one the large arteries in the root of the neck.
Nerves:
- the transverse cervical nerve (see description above)
is found spreading all over the anterior triangle to supply sensory innervation to the
skin.
- the right and left recurrent laryngeal nerves (Netter
70) ascend on both side of the trachea on their way to supply muscles of the pharynx.
The root of the neck and cervical viscera
The following are important structures in the root of the neck:
1. The division of the right brachiocephalic trunk to the right common carotid
and the right subclavian is behind the sternoclavicular joint. It is also the
site where the IJV joins the subclavian vein to become the brachiocephalic
vein.
2. The subclavian artery passes posterior to the subclavian vein and the
anterior scalene, but anterior to the cervical pleura and the apex of the
lung.
3. The vertebral artery leaves the 1st part of the subclavian artery (=medial
to the anterior scalene), passing backwards between the scalenes and the
prevertebral muscles to ascend to the brain through the foramina
transversaria in the transverse processes of the cervical vertebrae.
4. The thyrocervical trunk is the second branch of the first part of the
subclavian artery. We already saw its branches: the inferior thyroid, the
ascending cervical, the transverse cervical and the suprascapular arteries.
5. The costocervical trunk is a branch of the second part of the subclavian
(=posterior to the anterior scalene). The costal branch is the superior
intercostal artery, while the cervical branch is the deep cervical artery,
which passes posteriorly and supplies posterior deep cerical muscles.
6. The dorsal scapular artery may branch out from the second or the third
(=lateral to the anterior scalene) part of the subclavian. It passes through
the brachial plexus, passing anterior to the middle scalene, descending
medial to the suprascapular artery (Netter 410).
7. The vagus nerves descend more medially into the thorax than the
phrenics. The right vagus descends anterior to the 1st part of the
subclavian artery (where it loops and sends the recurrent laryngeal), while
the left phrenic descends more laterally, on the anterior scalene. The left
vagus descends between the left common carotid and the left subclavian
artery, while the left phrenic is more lateral. Also, remember that the vagi
pass posteriorly, behind the root of the lung, while the phrenics run
anteriorly, on the pericardium.
8. The sympathetic trunk (Moore 8.19) takes its regular position, just
anterior to the transverse processes of the vertebrae. It features three
important ganglia:
a. The inferior cervical ganglion = stellate ganglion, at C7, posterior
to the origin of the vertebral artery.
b. The middle cervical ganglion = at C6, anterior to the inferior
thyroid artery, anterior to the vertebral artery.
c. The superior cervical ganglion = at C1-C2. It can be seen sending
fibers that run along the internal carotid artery to structures in the
skull such as the eye.
Thyroid gland
- Located at C5-T1
- Has two lobes, connected by an isthmus
- An occasional pyramidal lobe may be seen above the isthmus
- Produces thyroid hormones, regulating rate of metabolism, and calcitonin,
responsible for lowering high calcium levels
- Has a thin connective tissue capsule
- Attached by dense connective tissue to the cricoid cartilage and superior
tracheal rings.
-
-
The superior thyroid artery divides into anterior and posterior branches.
The left and right anterior branches anastomose across the isthmus. The
posterior branch anastomoses with the inferior thyroid artery.
The superior and middle thyroid veins drain into the IJV. The inferior
thyroid veins drain into the brachiocephalic veins.
Parathyroid glands
- Usually four – one at each "corner" of the thyroid, but may be more
numerous and may be high in the neck or low in the mediastinum.
- Produce parathyroid hormone, responsible for elevating low calcium
levels.
- Unless enlarged, it is often difficult to see them on dissection.
- Usually supplied by branches of the inferior thyroid artery.
.2005 ,‫© אלכס‬