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Anterior & Posterior Triangle of the Neck
LECOM Yr 1
48
Anatomy
10/05/2011

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Term
at what vertebral level is the hyoid bone?
Definition
C3
Term
at what vertebral level is the thyroid cartilage?
Definition
C4-C5
Term
at what vertebral level is the cricoid cartilage?
Definition
C6
Term
at what level is the ishthmus of the thyroid gland?
Definition
level of the 2nd through 4th tracheal rings
Term
what are the boundaries of the anterior neck triangle?
Definition
Boundaries are as follows:
Posteriorly - Anterior border sternocleidomastoid muscle
Superiorly - Inferior border of the mandible
Median plane from the hyoid bone to the top of suprasternal notch
The roof is formed by superficial fascia & the platysma muscle
The floor is formed by fascia covering the pharynx, larynx & thyroid gland
Term
what are the boundaries of the submandibular triangle?
Definition
Superiorly – inferior border of mandible
Posteriorly – posterior belly of the digastric muscle – innervated by CN VII
Anteriorly – anterior belly of the digastric muscle – innervated by a twig from the mylohyoid nerve
Floor – mylohyoid & hyoglossus muscles
Mylohyoid muscle innervated by the mylohyoid nerve
Hyoglossus muscle innervated by the hypoglossal nerve
Term
which nerve lies on the superficial surface of the hypoglossus muscle and then continues anteriorly to the mylohyoid muscle?
Definition
the hypoglossal nerve (XII)
Term
the mylohyoid and anterior belly of the digastric muscles are innervated by which nerve? this nerve is a branch of which nerve?
Definition
the mylohyoid nerve

a branch of the inferior alveolar nerve (branch of V3)
Term
the posterior belly of the digastric muscle is innervated by which nerve?
Definition
the facial nerve (CN VII)
Term
the hypoglossal nerve innervates all the intrinsic and extrinsic muscles of the tongue except?
Definition
the palatoglossus

innervated by the pharyngeal plexus
Term
what lies deep to the stylohyoid and posterior belly of the digastric muscles?
Definition
the lingual nerve and the submandibular ganglion
Term
what are the boundaries of the superior carotid triangle?
Definition
Boundaries are the posterior belly of the digastric muscle, the superior belly of the omohyoid muscle & the anterior border of the sternocleidomastoid muscle
Floor is formed by parts of the thyrohyoid, hyoglossus &, inferior & middle constrictor muscles
Contents are the carotid sheath that contains the common carotid artery & its branches, internal jugular vein & its tributaries, vagus nerve, external carotid artery & some of its branches, hypoglossal nerve (CN XII) & roots of ansa cervicalis
Term
what is the ansa cervicalis?
Definition
In general the superior root of the ansa cervicalis is from branches of the 1st & 2nd cervical nerves that travel with the hypoglossal nerve for a short distance & then form the superior root

The inferior root is from branches of the 2nd & 3rd cervical nerves

hitchhikes with hypoglossus nerve, not a part of it/branch of it, gives innervation to the strap muscles
Term
what is the carotid sinus?
Definition
The carotid sinus is a baroreceptor that reacts to changes in arterial blood pressure – it is primarily innervated by the glossopharyngeal nerve (CN IX) via the carotid sinus nerve & also receives innervation from the vagus nerve (CN X)
Term
what is the carotid body?
Definition
The carotid body is a mass located on the deep side of the bifurcation near the carotid sinus that is a chemoreceptor that monitors the level of oxygen in the blood - it is stimulated by low levels of oxygen – it too is innervated by the glossopharyngeal nerve (CN IX) via the carotid sinus nerve & also the vagus (CN X)
Term
what are the boundaries and contents of the submental triangle?
Definition
This a small unpaired triangle
Boundaries are:
Apex – symphysis menti
Base – hyoid bone
Side – anterior belly of digastric muscle
Floor – one half of the mylohyoid muscle – the 2 halves of the muscles unite in the midline by a fibrous raphe

Contents – submental lymph nodes & small veins that unite to form the anterior jugular vein
Term
what are the boundaries and contents of the muscular (inferior carotid) triangle?
Definition
Boundaries are as follows:
Superior belly of omohyoid muscle
Anterior border of sternocleidomastoid muscle
Median plane from the hyoid bone to the top of suprasternal notch

Contents are as follows:
Viscera of the neck
Thyroid
Parathyroid

Infrahyoid muscles
Sternohyoid
Sternothyroid
These are often referred to as “strap muscles”
Term
describe the external jugular veins, what forms them and what they receive
Definition
Formed by the posterior auricular and retromandibular veins
Receives many tributaries in the neck as it descends to join the subclavian vein
Term
describe the anterior jugular veins, where they connect and where they empty
Definition
Variable & inconsistent
Drain the anterior aspect of the neck
Sometimes connected by a jugular venous arch just superior to the suprasternal notch
Empties into the subclavian vein or sometimes into the external jugular vein
Term
what are the strap muscles and what are they innervated by?
Definition
Infrahyoid Muscles
Sternohyoid
Omohyoid
Inferior belly
Superior belly
Thyrohyoid
Sternothyroid

All are innervated by anterior rami of spinal nerves via the ansa cervicalis
Term
the inferior thyroid vein in the midline usually drains into which vein?
Definition
the brachiocephalic vein
Term
describe the thyroid gland, its blood supply and its structure
Definition
Ductless or endocrine gland

Largest endocrine gland in the body

Thyroid hormone secretions control metabolism

Two lobes connected by a isthmus

Sometimes, a pyramidal lobe exists

Blood supply is by superior and inferior thyroid artery

Parathyroids lie on the posterior aspect of the thyroid gland. There are usually 4 of them
Term
where are the parathyroid glands located and what are their function?
Definition
The parathyroid glands typically lie on the posterior thyroid gland

Their secretions help control blood calcium levels

Care is taken to retain these glands during thyroidectomy

Note the differences in the course of the recurrent laryngeal nerves

During thyroidectomy, these nerves could be damaged
Term
the left recurrent laryngeal nerve curves around which structure?
Definition
the aortic arch
Term
the right recurrent laryngeal nerve curves around which structure?
Definition
the right subclavian artery
Term
what is a goiter?
Definition
Goiter is a condition in which the thyroid gland becomes enlarged & is endemic in certain parts of the world deficient in iodine

There are various types of goiter – one type is exophthalmic goiter due to an excess of thyroid hormone that results in bulging eyeballs
Term
describe the investing layer of cervical fascia and where it is located
Definition
Most superficial of the deep layers
Anteriorly, it splits to enclose the sternocleidomastoid muscle. Posteriorly, it splits to enclose the trapezius m.
It also splits to enclose the submandibular and parotid glands
Superior attachment – ext. occipital protuberance, ligamentum nuchae, sup. nuchal line, hyoid bone (also attaches to mandible).
Lateral attachment – mastoid processes and zygomatic arches
Inferior attachment – manubrium, clavicles, acromions and spines of the scapula
It splits at the manubrium to create the suprasternal space
Term
describe the pretracheal layer of cervical fascia and where it is located
Definition
Extends from the hyoid bone inferiorly to blend with the fibrous pericardium of the heart
Has a muscular layer enclosing the infrahyoid muscles
Has a visceral layer enclosing the thyroid gland, trachea, and esophagus
Visceral layer is continuous posteriorly with the buccopharyngeal fascia of the pharynx
Blends laterally with the carotid sheaths
The carotid sheath blends with all three fascial layers. It contains: common (inferiorly) and internal (superiorly) carotid arteries, internal jugular vein, vagus nerve
Forms ligaments that suspends the digastric and omohyoid muscles
Term
describe the prevertebral layer of cervical fascia and where it is located
Definition
Tubular sheath wrapping the vertebral column and associated structures
Extends from the base of the cranium to T3 vertebra – fuses with the anterior longitudinal ligament
Extends laterally surrounding the brachial plexus and axillary vessels
Term
describe the carotid sheath and what it contains
Definition
Tubular sheath extending from the cranial base to the root of the neck

It contains: common & int. carotid arteries, int. jugular vein, vagus nerve, deep cervical lymph nodes, sympathetic nerve fibers
Term
where is the "danger" space?
Definition
is the Prevertebral space – aka “danger space” between the alar and prevertebral fascial layers. Infection in this space can reach throughout the thorax
Term
where is the retropharyngeal space located?
Definition
The retropharyngeal space occurs between the alar and buccopharyngeal layers. Infection in this space can reach the superior mediastinum
Term
where is the platysma muscle located? what is it innervated by?
Definition
Lies in the superficial cervical fascia
Inferior attachment - fascia over deltoid and pectoralis major mm.
Superior attachment - blends with the muscles of facial expression
No important actions (could help depress the mandible) – cervical component of muscles of facial expression
Innervated by the cervical branch of the facial nerve
Supraclavicular nerves (from C3 & C4 cervical plexus) pierce it to innervate skin
Term
what are the boundaries of the posterior triangle?
Definition
Anteriorly - Posterior border of the sternocleidomastoid muscle
Posteriorly - Anterior border of the trapezius muscle
Inferiorly - Middle third (1/3) of the clavicle
Roof - Investing layer of cervical fascia
Floor - Prevertebral layer of deep cervical fascia covering deep neck muscles

The post. triangle can be further subdivided by the inferior belly of omohyoid m. into occipital and supraclavicular triangles. Your book calls this the omoclavicular or subclavian triangle
Term
what are the muscles in the floor of the posterior triangle?
Definition
Splenius capitis
Levator scapulae
Posterior scalene
Middle scalene
Anterior scalene
Term
where are the scalene muscles attached?
Definition
The anterior & middle scalene muscles are attached to the 1st rib, but the posterior is attached to the 2nd rib

The subclavian vein lies anterior to the anterior scalene muscle & the artery lies posterior to it

all attach to vertebrae and to the ribs (pump handle); if muscles contract it pulls the ribs up during inspiration
Term
describe the omohyoid muscle, its 2 bellies, and its innervation
Definition
The inferior belly of the omohyoid muscle crosses the inferior part of the post. triangle.

Originates on the sup. border of the scapula
Inserts on the inf. border of the hyoid bone

The omohyoid has two bellies connected by a tendon and separated by a sling made up of investing fascia

The sup. Belly is in the anterior triangle

The inf. Belly is in the post. Triangle

Innervated by the ansa cervicalis (anterior rami from C1 to C3)

Depresses and stabilizes the hyoid bone during swallowing, opens pharnyx
Term
what are the contents of the occipital part of the posterior triangle?
Definition
External jugular vein
Posterior branches of cervical plexus of nerves
Accessory nerve
Trunks of the brachial plexus
Transverse cervical artery
Cervical lymph nodes
Term
what are the contents of the supraclavicular part of the posterior triangle? (below the omohyoid)
Definition
Subclavian artery
Part of subclavian vein
Suprascapular artery
Supraclavicular lymph nodes
Term
where does the external jugular vein begin and where does it terminate?
Definition
Begins by union of the retromandibular and posterior auricular veins
It descends on the superficial surface of the sternocleidomastoid m.
It terminates in the subclavian vein after piercing the investing layer of fascia
Tributaries while traversing the post. triangle include: transverse cervical, suprascapular, and anterior jugular vv.
Term
describe the 3 parts of the subclavian artery and what branches each gives off
Definition
Subclavian (has three parts separated by the anterior scalene muscle)

1st part gives off vertebral artery, internal thoracic artery, & thyrocervical trunk, costocervical trunk (on the left only)
Thyrocervical trunk gives off transverse cervical, suprascapular, and inferior thyroid

2nd part is behind the anterior scalene muscle. Gives off costocervical trunk on the right most of the time. On the left, costocervical trunk typically branches from the 1st part.

3rd part gives off dorsal scapular a.
Term
what nerves are located in the posterior triangle?
Definition
The spinal accessory nerve (CN XI)
Passes deep to or through the sternocleidomastoid muscle to innervate it. Then, it crosses the triangle to innervate the trapezius muscle

Transverse cervical nerves (C2 - C3)
Supply skin over the anterior triangle

Great auricular nerves (C2 – C3)
Supplies skin over the parotid gland and around the auricle

Supraclavicular nerves (C3 & C4)
Pierce the platysma m. to supply skin over the anterior and lateral shoulder

All are superficial branches of the cervical plexus
Term
the spinal accessory nerve lies on the anterior surface of which muscle?
Definition
the levator scapulae
Term
the phrenic nerve lies on the anterior surface of which muscle?
Definition
anterior scalene muscle
Term
describe the branches of the cervical plexus in general
Definition
Cervical plexus is formed by anterior rami of C2 to C4, with possible contributions from C1 & C5. After forming in prevertebral fascia, it separates into:

Muscular (deep) branch
Phrenic nerve, supplies both motor and sensory to the diaphragm
Prevertebral muscular branches supplying the rectus capitis anterior, rectus capitis lateralis, longus colli, and longus capitis mm.

Ansa cervicalis (ansa = hypoglossal) has two roots
Superior, formed by C1 & C2. It loops down within the carotid sheath from the hypoglossal nerve
Inferior, formed by C2 & C3. It joins the superior root
Branches from the ansa cervicalis innervate the sternohyoid, sternothyroid, and inferior belly of the omohyoid mm. (strap muscles)
Term
where would one administer a cervical plexus nerve block?
Definition
at erb's point

Anesthetic agent is injected along the posterior border of the SCM, mainly near the inferior third – the nerve point of the neck

all nerves coming out of nerve point, can block all at once with one stick
Term
what is congenital torticollis?
Definition
The most common type is a result of a fibrous tissue tumor (fibromatosis colli) that develops in the sternocleidomastoid muscle prior to birth

During birth, when the infants head is pulled too much, this can result in tearing fibers of the sternocleidomastoid – a hematoma usually occurs that becomes a fibrotic mass that entraps a branch of the spinal accessory nerve & thereby denervates part of the muscle

fibrosis that shortens muscle, pulls head in that direction and pulls chin up other way, ipsilateral side

hematoma results in only pull on unaffected side, no pull on affected side (muscle cannot contract), contralateral side
Term
what is spasmodic torticollis?
Definition
Cervical dystonia (abnormal tonicity), is commonly known as spasmodic torticollis or wry neck, usually begins between ages 20 & 60 years
It may involve any bilateral combination of lateral neck muscles, especially the sternocleidomastoid & trapezius muscles
Symptoms are sustained turning, tilting, flexing or extension of the neck
Shifting the head laterally or anteriorly can occur involuntarily The shoulder is usually elevated & anteriorly displaced on the side to which the chin turns
Most patients with these symptoms suffer neck pain