Superficial and Lateral Muscles of the Neck, Moore 4 th ed 1000-1002
I.
A.
Platysma
Is a broad sheet of muscle in the subcutaneous tissue of the neck. It is
extremely thin. Just beneath it are the External jugular vein and the cutaneous
nerves.
A. Attaches below in the deltoid and pectoralis major muscles and passes over
the clavicle and the jaw.
A. Blends with the facial muscles of the chin
A. May be discontinuous (strips instead of a sheet)
A. Above, when it tenses it does like a guy does when shaving. Below, it helps
open the jaw, grimace, or make the tense face.
A. Is supplied by the cervical branch of the facial nerve
I. Sternocleidomastoid
A.
Makes a triangle from each side
A. At the bottom part, has two attachments. They are the sternal head and
the clavicular head. The sternal head attaches to the manubrium (hence the
name sternal) and the clavicular attaches to the top of the middle 1/3 of the
clavicle. The two parts from each attachment join as the muscle courses up to
attach to the mastoid process of the temporal bone and the lateral half
of the superior nuchal line. (Essentially attaches to the base of the skull
behind the ear.)
A. Lies within the deep cervical fascia, which forms a sheath around it.
A.
Motions:
1. When they both tense, they bring the chin toward the neck. If they do
this while the deep cervical muscles of the neck (extensors), they can help
the chin poke forward.
2. If only one side tenses, it pulls the head diagonally down - the chin to
the side and down (toward the shoulder).
I. Trapezius
A.
Covers the back of the neck and thorax sides, forming a diamond shape
from neck to shoulders to spine
B. Is considered superficial muscle of the back, pectoral girdle muscle, and
cervical muscle.
C. Attachments:
1. Starts at the neck and head: Medial third of superior nuchal line,
the external occipital protuberance, ligamentum nuchae.
2. Fans out to the shoulders: Lateral third of clavicle, acromion, and
part of scalpula
3. Then runs down and inward to close the diamond: to the spine
at C7 to T12, and lumbar and sacral spinous processes as well.
D. Function - all the movements of the shoulder blades - upper part raises,
horizontal fibers between them pull them in, downward part of the diamond
depresses them.
Triangles of the Neck, Moore 4 th 1003-1024
I. Overview - the two triangles of each side of the neck - Definition
A.
Posterior triangle
1. Boundaries:
a. Posterior edge of sternocleidomastoid
b. Anterior edge of trapezius
c. Middle part of clavicle that lies between SCM and trapezius
2. Corners and Walls
a. Apex - where SCM and trapezius both join the skull
b. Roof - deep cervical fascia (lies over it)
c. Floor - muscles covered by prevertebral deep cervical fascia
3. Divisions are two smaller triangles within it
a. Supraclavicular or subclavian - above the clavicle yet below the
omohyoid muscle
b. Occipital - above the omohyoid muscle to the apex
A.
Anterior Triangle
1. Boundaries
a. Midline of the neck
b. Front edge of SCM
c. Mandible
2. Landmarks
a. Apex is at the jugular notch of manubrium (so the triangle is
upside down)
b. Roof - platysma and the subcutaneous tissue that is with it
c. Floor - pharynx, larynx, thyroid gland
3. Divisions
a. Submentalr triangle - the underside of the chin in the
center,
b. Submandibular triangle - Under the jawline, bound in front
by the anterior belly of the digastric muscle, behind by the posterior
belly. Contains lymph nodes, submandibular gland, hypoglossal
nerve, mylohyoid nerve, parts of facial artery and vein.
c. Carotid triangle bound by posterior belly of digastric muscle,
superior belly of omohyoid, and SCM to the back. Contains
common carotid artery and branches, internal jugular vein,
vagus nerve, external carotid artery, hypoglossal nerve,
accessory nerve, thyroid, larynx, pharynx.
4. Muscular triangle - a small piece that is bound by superior belly of
omohyoid above, anterior part of SCM, midline of neck. Contains thyroid
and parathyroid glands.
All of these will be discussed in more detail later, once again Moore goes out of order.
I. Posterior Cervical Triangle
A.
Muscles in the Posterior Triangle
1. The floor is a fascia overlying 4 muscles: splenius capitis, levator
scalpulae, middle scalene, and posterior scalene. These are essentially
four muscles running from back to front in the order listed that run from
the head downward. The anterior scalene is also in the row with them, but
is hidden by SCM.
2. The occipital triangle contains the occipital artery in the apex and also
the accessory nerve.
3. The supraclavicular triangle is marked by the supraclavicular fossa in
a live person (the space above the collarbone that you can stick your finger
in when you shrug your shoulders), and is important because the
suprascalpular artery and the external jugular cross it superficially. The
subclavian artery is in it, but deeper.
A.
Vessels in the Posterior Triangle
1. Veins
a. External Jugular - drains the scalp and side of head. Starts at
the meeting of the retromandibular and posterior auricular veins. It
runs over SCM (but internal to platysma), and down into the front
bottom of the triangle. It enters the deep cervical fascia that is the
roof of the triangle at the back of SCM and keeps going down to the
subclavian vein.
b. Subclavian vein - drains the upper limb. It curves through the
posterior triangle in front of the anterior scalene and phrenic nerve
and joins the internal jugular to get the brachiocephalic vein.
2. Arteries
a. The subclavian artery gives off as its second branch (after the
vertebral artery) the thyrocervical trunk. This gives off several
branches.
(1) Suprascapular Artery comes off first and runs outward
and downward across the anterior scalene and the phrenic
nerve. It turns at first sharply downward then back up,
making a U link that lies in front of the subclavian. The
upswing part runs back to supply muscles on the back of the
scapula.
(2) Transverse Cervical Artery (transverse artery of the
neck) runs superficially and laterally across the phrenic
nerve and anterior scalene muscle. (It runs around the neck
like a choker necklace, but then instead of turning around
the back curve, turns down and runs over the shoulder
blade.) It passes through the trunks of the brachial plexus
(supplying their vasa nervosa) and then deep to trapezius.
b. The common carotid splits into the interior and exterior
carotid arteries. The external carotid artery supplies the
neck area. It gives off:
(1) Occipital artery which enters the triangle at the apex
and goes into the head to the back half of the scalp. (We saw
this guy when learning about the head vessels.)
(2) Posterior Auricular artery
(3) Ends in the superficial temporal artery
(4) Gives off arteries to the face
c. The third part of the subclavian artery runs to the upper
limb. It loops over the collarbone and is hidden in the inferior part
of the posterior triangle. It sits both behind and above the
subclavian vein. Behind the anterior scalene muscle, it is by the
first rib - you can press it against the rib to stop limb bleeding.
A.
Nerves of the posterior triangle
1. Accessory Nerve (CN 11) shoots out from below the digastric and
stylohyoid muscles about 1/3 of the way down the SCM, running posterior
and down through the triangle just above the investing layer of the deep
cervical fascia. Its final third goes under trapezius, so you don’t see it if
you do just a superficial dissection. It has a spinal and a cranial root.
a. The spinal root passes down and back, supplying SCM, then
crosses the triangle then runs deep to SCM and supplies trapezius.
1. Cervical Plexus is formed by the ventral roots of C1 to C4. They go
out and then make loops to rejoin the spinal nerves. The loops are the
cervical plexus. The loops are: primary ventral rami of C1 to C4 joining
gray communicating rami from the superior cervical sympathetic
ganglion.
a. The posterior branches supply the skin of the front of the neck
and thorax, while the anterior ones make the ansa cervicalis
which is a loop supplying the infrahyoid muscles (anterior triangle).
b. The cutaneous branches come out at the middle of the back of
SCM. The nerve point of the neck is this, supplying the skin of the
neck, side part of the top of the chest, and the bump behind the ear.
Again, they receive the gray rami communicantes from the sup.
cervical ganglion.
c. There are specific branches, especially from C2-C3 that come
from the loops:
(1) Lesser occipital nerve (C2) - to the skin of the neck and
above and behind the ear
(2) Great auricular nerve (C2 and C3) runs across SCM over
the parotid. It supplies the skin there, part of the ear, and
skin from the corner of the jaw to the mastoid process (this is
a few branches)
(3) Transverse cervical nerve (C2 and C3) supplies the skin
of the anterior triangle and crosses SCM. (Note - it does not
run with the transverse cervical artery. The artery is lower
and runs front to back, while the nerve runs back to front.)
d. There are specific branches from C3 to C4 from the loops: they
are the Supraclavicular nerves (C3 C4) which come from one
trunk under SCM and go to the kin of the neck. They run over the
clavicle and innervate the skin over the shoulder and front.
e. The long thoracic nerve comes from C5-C7.
f. The phrenic nerve comes from C3, C4, C5 (three four and
five keep the diaphragm alive),
(1) is motor, sensory, and sympathetic, and supplies the
diaphragm, mediastinal pleura, and pericardium. It uses the
communicating fibers from the sympathetic ganglia in the
neck to help with its many functions.
(2) It is considered to “start” at the side of the anterior
scalene muscle at the superior edge of the thyroid cartilage.
(3) Runs with IJV down the anterior scalene and deep to the
transverse cervical and suprascapular arteries. It is behind
the subclavian vein and in front of the internal thoracic
artery. (Runs between the subclavian artery and vein)
(a)
On the left, it crosses anterior to the first part of
the subclavian artery
(b)
On the right, it crosses anterior to the second
part of the subclavian artery. This pretty much
means it is just further to the side on the right.
(4) There may be an accessory phrenic nerve from C5 - a
small thing with lots of the same fibers. It joins the main one
in the neck or chest. This is important to know when
anesthetizing the diaphragm for lung surgery.
1. Brachial Plexus
a. Ventral roots slide between anterior and middle sclene muscles.
They come from C5 through T1 and then form three trunks that go
outwards through the posterior triangle. They pass through the
cervicoaxillary canal (between the collarbone and first rib) to run
into the armpit and down through the arm (this is important
because we need to remember what innervates the arm: C5 to T1).
b. The suprascapular nerve runs across the posterior triangle side
to side.
A. Lymph Nodes in the posterior triangle enter the superficial cervical lymph
nodes along the EJV. Then they drain to the deep cervical lymph nodes that are
in the fascia of the carotid sheath along the IJV.
I. Anterior Cervical Triangle
A.
Sub-triangles - a little more detail than above (why oh why can’t fucking
moore put everything in one place?)
1. Sub-mandibular triangle
a. Gland- the submandibular gland is along the bottom of the
jawline and between the anterior and posterior bellies of the
digastric muscle. This is most of the triangle. The duct of the gland
is about 5 cm and runs parallel to the tongue to open into the
mouth at the sublingual papilla
b. There are lymph nodes along the gland
c. Floor is the mylohyoid muscle, hyoglossus muscle, and middle
constrictor of the pharynx
d. The hypoglossal nerve (motor innervation of the tongue) passes
through the triangle, as do the nerve to the mylohyoid, parts of the
facial artery and vein, and submental branch of the facial artery.
2. Submental triangle sits under the chin and is central and unpaired.
Its bottom boundary is the hyoid bone (the base) and the sides are the
anterior bellies of the two digastric muscles. The floor is the two
mylohyoid muscles which meet in a raphe in the middle. It has lymph
nodes and small veins that form the anterior jugular vein.
3. Carotid triangle is mostly vascular.
a. Boundaries - superior belly of omohyoid, posterior belly of
digastric, anterior border of SCM.
b. Contains the common carotid artery and the place you can feel it
pulsing. It divides at the level of the top of the thyroid cartilage,
where there is:
(1) Carotid sinus dilation of the proximal part of the
internal carotid. CN IX and vagus give its baroreceptor
properties.
(2) Carotid body - small mass of tissue lying medially.
Again, CN IX and X monitor chemoreceptors sensitive to
oxygen in the blood.
c. Carotid sheath is a tube of fascia from the base of the skull to
the root of the neck. It is a union of the three layers of deep cervical
fascia. Low, it contains:
(1) Common carotid artery (medial)
(2) Internal Jugular (lateral)
(3) Vagus (posterior)
Higher up it contains the internal carotid artery (after the split)
and the ansa cervicalis on the side and front part.
1. Muscular Triangle is bound by the superior belly of the omohyoid,
the anterior border of SCM, and the median plane of the neck. It has the
infrahyoid muscles and the thyroid and parathyroid glands.
A.
Muscles of the anterior triangle - see chart p. 1016
1. Suprahyoid Muscles - above the bone and connect it to skull. They are
essentially the bottom of the mouth
a. Mylohyoid - floor of the mouth and sling under the tongue raise tongue in swallowing or sticking out tongue. From mandible
to body of hyoid bone
b. Geniohyoid muscles - above the mylohyoid. Widens pharynx
c. Stylohyoid form a slip on each side which runs parallel to the
posterior digastric
d. Digastric - has two bellies that swing toward hyoid bone. Joined
by intermediate tendon. Slide anteriorly and posteriorly as it
connects the tendon to the body an greater horn of hyoid bone. CN
V supplies anterior belly, CN VII posterior. Lowers jaw, steadies
hyoid bone
2. Infrahyoid Muscles - below hyoid bone, anchor it and pull it down while
swallowing/speaking.
a. Sternohyoid - most medial, manubrium and tip of clavicle
b. Omohyoid - lateral to sternohyoid, two bellies with tendon in
middle, connected to clavicles
c. Sternothyroid - wide and medial, covering the side of the
thyroid, attaching to thyroid cartilage.
d. Thryohyoid - thyroid cartilage to hyoid bone (short)
Sternohyoid and omohyoid are superficial, Sternothyroid and Thyrohyoid
are deep.
I. Vessels in the Anterior Triangle
A.
Arteries - the carotid system
1. The common carotid is in the carotid triangle. It goes upward in the
carotid sheath with the IJV and vagus until reaching the superior edge of
the thyroid cartilage where it divides into the external and internal
carotid arteries.
a. The right common carotid comes from a split from the
brachiocephalic trunk. (The other side of the split is the
subclavian.)
b. The left common carotid comes directly off of the aortic arch.
2. The internal carotids do not branch in the neck. They go through
the carotid canals of the temporal bones into the head. Where they start,
they have the carotid sinus, the pressure receptors for blood pressure.
The carotid body in the same location is the chemoreceptor to changes
in oxygenation of the blood.
3. The external carotids supply the outside of the skull except for one
branch - the middle meningeal artery. They run up between the back of
the jaw and the ear, through the parotid gland, and has the following
branches, in order:
a. Superior thyroid artery - runs in front of and below the
infrahyoid muscles to the thyroid, also supplying the infrahyoids
and SCM. It gives off the superior laryngeal artery.
b. Ascending pharyngeal artery - which points backwards, and
ascends on the pharynx deep to the internal carotid (between the
external and the internal). It supplies the pharynx, middle ear,
prevertebral muscles, and cranial meninges.
c. Lingual artery - lies on the middle constrictor muscle of the
pharynx and arches over to run deep to CN XII and deep to
stylohyoid, and the posterior belly of the digastric muscle. It turns
up at the front of hypoglossus muscle to become the deep lingual
and sublingual arteries.
d. Facial artery - may come off as a joined branch with the
lingual artery. It gives off the tonsillar branch which is the major
supplier of the tonsil, and the palate branches and submandibular
gland. Then it goes upwards covered by digastric and stylohyoid
behind the corner of the mandible and enters the submandibular
gland, runs forward, and then over the jaw (where you can feel it)
and into the face.
e. Occipital Artery - also points backwards. It is deep to the
digastric muscle and goes through a groove in the base of the skull
and ends in the scalp. It lies on top of the internal carotid and CN
IX to XI.
f. Posterior auricular artery - also pointing backwards, runs
between the ear and the mastoid process to those muscles, parotid
gland, facial nerve, part of the temporal bone, and ear and scalp.
g. The maxillary artery which is the last major branch it gives
off, and seems more like a branch than a split
h. The superficial temporal artery which is essentially the end
of it.
Sara says: this spells SALFOPS MaST. The APOP (ascending pharyngeal, occipital,
and posterior auricular) are the ones pointing backwards.
A.
Veins - mostly the IJV system
1. The IJV starts at the jugular foramen as the end of the sigmoid sinus.
It runs down in the carotid sheath with the internal carotid which joins
later to become the common carotid. The artery is medial to the vein. The
cervical sympathetic trunk is behind the carotid sheath. The IJV leaves
the anterior triangle deep to SCM about at the point that it between the
two heads of the muscle. It joins the subclavian to form the
brachiocephalic. At the point where it joins, there is a bulge - the
inferior bulb of the IJV which has a valve that prevents backflow when
you bend over
2. There are also tributaries leading to the IJV. From top to bottom:
a. Sometimes: Occipital vein - from the back side, but more often
this drains into the suboccipital plexus, which goes to the deep
cervical vein.
b. Inferior petrosal sinus - leaves the skull through the jugular
foramen and enters the superior bulb of IJV.
c. Pharyngeal veins - at the level of the angle of the jaw
d.
Facial veins - about the level of the hyoid bone
and may receive the superior thyroid or lingual veins instead of
them going straight to IJV
e.
Lingual veins - from one vein of the tongue
f.
Superior and middle thyroid veins
A.
Nerves of the Anterior Triangle
1.
Transverse Cervical Nerve from C2 and C3 supplies
the skin over the triangle. It wraps around SCM just below the great
auricular nerve and crosses it to get to the anterior triangle. (Remember,
we saw it in more detail in the posterior triangle.)
2.
Hypoglossal Nerve (CN XII) is the motor nerve of the
tongue and runs deep to the posterior belly of the digastric. It runs
between the external carotid and the jugular (seems to be a pattern here,
the nerve between the vessels...the vagus does the same between the
carotid and jugular but vertically). It gives off part of ansa cervicalis and a
branch to the geniohyoid muscle, but these are only fibers from C1 which
joined it. (When you look at it, it looks like a branch of the hypoglossal
nerve, but it’s actually not, it’s fibers from C1.)
3.
Glossopharyngeal Nerve (CN IX) is in the
submandibular and carotid triangles because it is on its way to the tongue
and pharynx
4.
Vagus (CN X) gives off branches to the pharynx,
larynx, and cardiac branches.
Surface/Clinical Notes:
You see the platysma when doing the “taking a shit” face. The middle V in the front of the
neck is between the sternal heads of sternocleidomastoid. It is easier to see this muscle higher if you
turn your head to the side. You can stick a needle into the jugular by going between the two heads of
SCM. (As people who live in Berkeley will see drug dealers do after they have destroyed all
peripheral veins.) When you raise your shoulders you can see trapezius.