Deep Structures of the Neck, Root of the Neck, Cervical Viscera, Thyroid and
Parathyroid Glands, Moore 4th ed pp. 1025-1038
A. Deep Structures of the Neck
1st. Prevertebral Muscles - these are the muscles in the floor of the triangles of the neck, which
are posterior to the prevertebral layer of deep cervical fascia. (In front of the spine and
behind the deep fascia, and of course behind things like the esophagus and trachea.) They
are divided into two groups: the anterior vertebral muscles and the lateral vertebral
muscles. They are summarized on a chart on page 1026.
1. Anterior Vertebral Muscles
One. Longus Colli attaches to the anterior side of the vertebral column
down to T3 on the body, and fans out to the transverse processes of
C3 to C6. (This means that in the middle it runs straight up and
down, but part of it toward the bottom spreads out to the sides.) If
it acts unilaterally, it bends the neck down and to the side.
Two. Longus Capitis runs up from the transverse processes of C3 to C6 to
the bottom of the basilar part of the occipital bone. It sits above
longus colli and flexes the head.
Three. Rectus capitis anterior is just behind the top of longus capitis. It
goes from the front of C1 to the base of the skull right in front of
the occipital condyle and helps bend the head.
Four. Rectus capitis lateralis is right next to the anterior rectus muscle of
the head and attaches from the transverse process of C1 to the
jugular process of the occipital bone (fans outward). It helps flex
the head and steady it.
2. Lateral Vertebral Muscles
One. Splenius capitis - is an extensio of splenius cervicus to the occipital
bone - part of the floor of the posterior triangle of the neck. It runs
from the spinous processes of T1 to T6 up to the outside of the
superior nuchal line and the lateral part of the mastoid process.
Moves head to the side and helps in rotation of the head.
Two. Levator scapulae runs somewhat parallel to splenius capitis ,
attaching to the posterior tubercles of the transverse processes of
C1 to C4, and running to the upper medial edge of the shoulder
blade. It helps raise the shoulder blade.
Three. Anterior scalene - transverse processes of C4 to C6 to the 1st rib.
Four. Middle scalene runs from the transverse processes of C4 to C6 to
the top of the first rib.
Five. Posterior scalene is the farthest back of the three scalenes, and runs
from the transverse processes of C4-C6, then drop to attach to the
outside of the second rib.
The scalenes attach from C4 to C6, while above them levator scalpula attaches to C1 to
C4. The three run in a line parallel to each other. They all bend the neck to the side and
are accessory muscles of respiration, helping to raise the ribs they attach to in difficult
breathing.
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2nd. Root of the Neck - the junction between the neck and thorax. On the side it is bounded by
the first ribs, in the front by the manubrium, and in the back by T1.
1. Arteries in the Root of the Neck
One. Brachiocephalic trunk is behind the sternohyoid and sternothyroid
muscles and runs from the aoritc arch behind the manubrium, then
curves to the right to become the right common carotid and the
right subclavian arteries (behind the sternoclavicular joint).
Two. Subclavian Arteries supply the upper limbs but also the neck and
brain. Each one arches up and back, to make grooves in the lung.
They continue behind the anterior scalene muscles then curve
down behind the midpoints of the clavicles.
(1) Right Subclavian - from brachiocephalic trunk, in front of
cervical pleura and sympathetic trunk.
(2) Left Subclavian - from arch of aorta after left common
carotid artery, runs parallel to left vagus.
Three. Branches of the Subclavian
(1) Vertebral Artery - the one that ends up supplying the
brain like we learned in neuro.
(a) Cervical part ascends between longus and
scalene muscles, and passes deep to go
through the foramina of C6 (or a little
higher) to C1.
(b) Suboccipital Part runs on the back of the atlas
and enters the head through the foramen
magnum.
(2) Internal Thoracic Artery comes from the bottom of the
subclavian and distributes to the ribs.
(3) Thyrocervical Trunk - its branches were described in a
previous chapter. It comes off the top/front of the
subclavian just before it crosses the scalene muscle. It
gives three branches, which are described in another
chapter, from top to bottom:
(a) Inferior thyroid artery (which is formed at a
split with the ascending cervical artery)
(b) Transverse Cervical artery
(c) Suprascapular artery
(4) Costocervical Trunk arises from the posterior side of the
subclavian behind the ant. scalene muscle. It runs over
and back and divides into the superior intercostals (first
two intercostal spaces), and deep cervical artery
(posterior deep cervical muscles).
(5) Dorsal Scalpular Artery may be a branch of the transverse
cervical, but more often is straight off the subclavian. It
runs through the brachial plexus in front of the middle
scalene, and deep to levator scapulae in the back. It
supplies the rhomboid muscles.
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2. Veins in the Root of the Neck
One. External Jugular Veins drain blood from the face and scalp.
Two. Anterior Jugular Vein is highly variable and usually arises near the
hyoid bone from the superficial submandibular veins. It descends
medial to SCM and finally turns to the side behind SCM and
empties into the EJV or subclavian. Sometimes, the two sides may
unite and form a jugular venous arch in the suprasternal space.
This is really important for tracheotomies.
Three. Subclavian Vein is a continuation of the axillary vein, starting at
the side of the first rib and uniting with IJV to form the
brachiocephalic vein. It runs over the first rib in frnt of the scalene
tubercle - therefore it is parallel to the subclavian artery, but
separated from it by the anterior scalene muscle!
Four. Internal Jugular Vein ends behind the inner edge of the collarbone
where it meets the subclavian and becomes the brachiocephalic.
This site is often called the venous angle and the thoracic duct
spills in here. It is inside the carotid sheath.
3. Nerves in the Root of the Neck
One. Vagus Nerves come out of the jugular foramen and run in the back
of the carotid sheath between IJV and the common carotid artery.
Some cardiac branches of the vagus arise in the neck.
(1) The right vagus nerve runs in front of the subclavian
artery and behind the brachiocephalic vein to enter the
chest (right - goes cradled between them)
(2) The left vagus nerve runs between the common carotid
and subclavian and enters the thorax.
(3) The Recurrent Laryngeal Nerves come from the vagus at
the bottom of the neck. After they loop, they ascened to
the back of the thyroid and then continue in the
tracheoesophageal groove to supply the larynx except
for the cricothyroid muscle.
(a) The right recurrent laryngeal nerve loopsbelow
the right subclavian artery at T1/T2.
(b) The left recurrent laryngeal nerve loops under
the arch of the aorta at T4/T5.
Two. Phrenic Nerves start at the outside of the anterior scalene muscles.
They descend in front of the ant. scalenes under the IJV and SCM.
They pass under the deep cervical fascia, between the subclavian
artery and vein, and down the thorax.
Three. Sympathetic Trunks start from the side and slightly to the front of
the vertebral column. They have no white rami communicantes
(there never are with cervical spinal nerves). They do, however,
attach through gray rami communicantes to the superior, middle,
and inferior cervical ganglia. The ganglia get presynaptic fibers
from the superior thoracic spinal nerves and white rami
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communicantes from the sympathetic trunk (look this up, this
fucking moore can’t explain, are there or aren’t there white rc?
From where?) These ganglia pass fibers to splanchnic nerves
through direct visceral branches, and to the cervical spinal nerves
through the gray rami communicantes.
Four. The Inferior Cervical Ganglion usually fuses with the first thoracic
ganglion to make the stellate ganglion (cervicothoracic ganglion),
which lies in front of the side of C7 just above the first rib, and
behind the vertebral artery. It passes postsynaptic fibers through
gray rami communicantes to the ventral rami of C7 and C8 spinal
nerves (brachial plexus) and some to the heart through the inferior
cervical cardiac nerve, that runs down the trachea deep to the
cardiac plexus.
Five. The Middle Cervical Ganglion is small or absent. It is on the front
of the inferior thyroid artery at the level of the cricoid cartilage
(C6). It passes gray rami to the ventral rami of C5 and C6, rami to
the cardiopulmonary splanchnic nerves and eventually to the heart,
and through periarterial plexuses to the thyroid gland.
Six. The Superior Cervical Ganglion is at the level of C1 and C2. It is
large and easy to see. It gives off the arterial rami that form the
internal carotid sympathetic plexus. It also sends branches to the
external carotid and gray rami to C1 through C4. Also
cardiopulmonary splanchnic.
B. Viscera of the Neck
is split into three layers
1st. Endocrine Layer of the Cervical Viscera
1. Thyroid Gland lies deep to sternothyroid and sternohyoid from C5 to T1. It has
two lobes united by an isthmus over the second and third tracheal rings. It is in
a thin capsule that sends septa into the gland. It is attached to the cricoid
cartilage and superior tracheal rings by dense CT.
One. Arteries - the gland needs to be very vascular to secrete its
hormones into the system.
(1) Superior Thyroid Artery - comes off the external carotid
artery (high) enters the gland, and splits into anterior
and posterior branches, which descend along the two
surfaces and meet their counterparts in the middle.
(2) Inferior Thyroid Artery - comes off the thyrocervical
trunk (from subclav.), of which it is the largest most
noticeable branch runs up behind the carotid sheath
until it gets to the back of the thyroid gland. It pierces
the thyroid and supplies the bottom part.
(3) There can occasionally be a thryoid ima artery, running up
the middle from the aorta or subclavian - be careful
when cutting.
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Two. Veins - there are three pairs that anastomose a lot - the superior,
middle, and inferior. The inferior drains into the brachiocephalic
vein and is large, running kinda down the center. The superior and
middle thyroid veins drain into the IJV.
Three. Lymph - the vessels drain in the CT and into the capsule vessels,
which drain into the pretracheal and paratracheal lymph nodes.
They drain along the side to the inferior deep cervical lymph nodes.
Four. Nerves - sympathetic nerves from the three cervical sympathetic
trunk ganglia that get to the gland by the cardiac, and superior and
inferior thyroid periarterial plexuses. They are vasomotor.
Hormone secretion in the thyroid is regulated hormonally by the
pituitary, not by nerves.
Five. Variations:
(1) If it doesn’t descend, it can be as high as above the hyoid
bone or even behind the tongue.
(2) Thyroid tissue may get into the thymus below.
(3) Accessory tissue may develop an accessory thyroid gland
on the thyrohyoid.
(4) Pyramidal lobe - about ½ the thyroids have a weird lobe
that extends up and this is caused by remnants of the
thyroglossal duct.
(5) Absence of isthmus - split gland.
Six. Clinical Stuff
(1) Goiter
(2) Be careful of rec. laryn. nerves in surgeries. The right one
is really stuck to the inf. thyroid artery and damage will
screw up talking.
(3) External laryngeal nerve damage - a branch of the vagus will lead to a “flat, monotonous” voice due to paralysis
of the cricothyroid muscle.
2. Parathyroid Glands lie outside the thyroid capsule but inside its sheath, a little to
the side. The superior ones are just above the inf. thyroid artery entry points.
The inferior ones are highly variable in position. Occasionally they are even in
the chest.
One. Vessels
(1) Inferior thyroid artery gives them branches usually.
(2) Parathyroid veins drain into the venous plexus on the
anterior thyroid and trachea.
(3) Lymph drain (like the thyroid) into deep cervical and
paratracheal nodes.
Two. Nerves come from thyroid branches of the cervical symp. ganglia.
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Three. If they are removed totally during thyroid removal you get tetany, a
massive set of muscle spasms due to screwed up calcium levels.
This can lead to death as respiratory muscles are involved.
2nd. Respiratory Layer of Cervical Viscera
3rd. Alimentary Layer of Cervical Viscera
Apparently we will do later.
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