Anterior triangle of the Neck Flashcards
There are 4 subdivisions of the anterior triangle- name these and what each contains
submandibular - submandibular glands, lymph nodes, CN XII, facial artery and veins
submental - submental lymph nodes, small veins forming anterior jugular
carotid - thyroid gland, larynx, pharynx, carotid sheath, cervical plexus, ansa cervicalis, parts of CN XI and XII
muscular - supra and infrahyoid muscles, hyoid bone
Outline the borders of the anterior triangle
inferior border of mandible, anterior border of SCM and midline of neck
Describe each of the 4 suprahyoid muscles and their function
Mylohyoid - from mylohyoid ridge on mandible to hyoid, mylohyoid raphe joins muscles in midline, reinforces floor of mouth, lifts hyoid
Digastric - 2 bellys - anterior belly originates at digastric fossa on lower medial aspect of mandible and posterior belly originates from mastoid notch on medial side of mastoid process, attached to hyoid by fascial sling, elevates hyoid, lowers mandible
Stylohyoid - originates at styloid process, elevates hyoid
Geniohyoid - originates from mandible (mental spine), elevates and pulls hyoid forward
Outline the innervation of each of the suprahyoid muscles
Mylohyoid - CN V3 (nerve to mylohyoid)
Digastric - anterior= nerve to mylohyoid, posterior= digastric branch of CN VII
Stylohyoid- CN VII
Geniohyoid - anterior ramus of C1 (travels with CN XII)
Describe each of the 4 infrahyoid muscles and their function
Sternohyoid (superficial) - sternum to hyoid, depression of hyoid
Omohyoid (superficial) - 2 bellies - superior originates at intermediate tendon, inferior originates at superior border of scapula to intermediate tendon - tendon attaches to clavicle via fascial sling. depresses and fixes hyoid
Thyrohyoid (deep) - originates at oblique line on thyroid cartilage, depresses hyoid
Sternothyroid (deep) - originates at posterior surface of manubrium and inserts into oblique line on thyroid cartilage, draws larynx downward
Outline the innervation of the infrahyoid muscles
Sternohyoid - anterior rami C1 to C3 (through ansa cervicalis)
Omohyoid - anterior rami C1 to C3 (through ansa cervicalis)
Thyrohyoid - anterior rami C1 (fibres run with CN XII)
Sternothyroid - anterior rami C1 to C3 (through ansa cervicalis)
The supra and infrahyoid muscles sit in the muscular compartment of the neck.
Which compartment of the neck does the thyroid gland sit in?
Visceral
Outline the form and location of the thyroid gland
Made up of left and right lateral lobes- joined in the middle by isthmus (where a pyramidal lobe may be present- 50%)
Sits in the neck from the thyroid cartilage to the 5th tracheal ring
Outline the blood supply and drainage of the thyroid gland
ECA branches to give superior thyroid artery
Subclavian artery branches to give inferior thyroid artery
Superior and middle thyroid veins drain into IJV
Inferior thyroid vein drains into brachiocephalic vein
10% people have small thyroid ima artery over midline arising from brachiocephalic trunk
Describe the form of parathyroid gland and its location in the neck
2 pairs (superior and inferior) of small glands on posterior surface of thyroid gland
Which blood vessels supply the parathyroid
Inferior thyroid artery
drainage the same as thyroid gland
Describe the neurovascular control of the thyroid and parathyroid glands
Innervated by the thyroid branches from the cervical ganglia (sympathetic)
Which procedure would be carried out in an emergency airway blockage?
Cricothyrotomy
A large bore needle is passed through cricothyroid ligament which is later replaced by small tracheostomy tube
In a hospital setting, which procedure is often carried out in the case of airway obstruction?
Retraction of infrahyoid muscles and incision of thyroid isthmus to insert tube between 1-2 / 2-4 tracheal rings
In terms of neck surgery, which vascular, neurovascular and other structures should be considered?
Possible presence of thyroid ima artery
Recurrent and external laryngeal nerves
Possible age variations - soft trachea in children and neonates etc)
What is the recurrent laryngeal nerve?
Branch of the Vagus nerve (CN X)
Supplies intrinsic muscles and sensation of larynx and vocal cords
left loops around arch of aorta and right loops around subclavian artery
Where does the carotid sheath being and end?
Runs from foramen of carotid canal to arotic arch
Which structures are contained in carotid sheath?
CCA, IJV, CN X
Where is the carotid sinus located?
level of C3/4 (at superior border of thyroid cartilage)
dilation at the bifurcation of CCA, in wall of ICA
What is the function of the carotid sinus?
The function of the carotid sinus is to react to changes in blood pressure (contains baroreceptors which are sensitive to stretch)
Which nerves innervate the carotid sinus and body?
The carotid sinus and body are innervated by the carotid sinus nerve (branch of CN IX) and CN X
Where is the carotid body located?
The carotid body is located at the bifurcation of CCA, near the carotid sinus
What is the function of the carotid body?
The carotid body houses chemoreceptors - monitors oxygen, carbon dioxide, pH and temperature
When is the carotid body stimulated?
The carotid body is stimulated in emergency situations to return the body back to homestatic conditions eg. increase respiration.
What structures does the external carotid artery supply?
the ECA supplies the majority of the face and scalp
In what region of the neck does the ECA split into branches?
The ECA splits into branches in the carotid triangle in the anterior neck (exception- the 2 terminal branches)
The ECA has 1 medial, 2 posterior and 3 anterior branches and 2 terminal branches, name these.
Superior thyroid - anterior
Ascending pharyngeal - medial
Occipital - posterior
Lingual - anterior
Facial - anterior
Posterior auricular - posterior
Terminal branches - superficial temporal, maxillary
The ECA supplies the internal capsule via the middle meningeal artery, which branch is this part of?
The middle meningeal artery is a branch of the maxillary artery.
How does the middle meningeal artery enter the cranium?
the middle meningeal artery enters the cranium via the foramen spinosum (pterion)
Which muscles does the ECA run deep to?
The ECA runs deep to the stylohyoid and mylohyoid
Which structures does the IJV drain?
The IJV drains blood from the brain, skull, face and parts of the neck
Which structures does the IJV run deep to?
The IJV runs deep to omohyoid and SCM and lateral to CCA
Describe the journey of the IJV from the skull to the brachiocephalic vein
The IJV is a continuation of the sigmoid sinus in posterior cranial fossa and exits the skull via the jugular foramen, enters the carotid sheath and joins subclavian vein to become brachiocephalic vein.
What is the inferior bulb of IJV?
This is a bicuspid valve that permits blood flow to the heart while preventing backflow
What is the superior bulb of IJV?
This is a dilation at the origin of IJV where the inferior petrsoal sinus enters after it has left the cranium, via jugular foramen
Which structures does the EJV drain?
The scalp, face and superficial neck
Describe the course of EJV
The EJV begins at the angle of the mandible (just below parotid gland), joining the retromandibular and posterior auricular veins.
Crosses over SCM and pierces into investing fascia where it joins the subclavian vein at mid clavicle
Which veins drain into EJV?
the posterior external jugular, transverse cervical, suprascapular, anterior jugular
What is the location and function of the anterior jugular vein?
The anterior jugular vein arises superior to hyoid bone and descends between the midline and anterior border of SCM.
The anterior jugular vein communicates across the midline via jugular venous arch.
It drains into EJV or sometimes directly into subclavian.
Briefly describe the course of the facial nerve (CN VII)?
The facial nerve (CN VII) exits the skull via internal acoustic meatus and forms a parotid plexus where it is engulfed by the parotid gland.
This gives rise to 5 branches - temporal, zygomatic, buccal, marginal mandibular and cervical.
The facial nerve also has a digastric branch which supplies the posterior belly of digastric and stylohyoid muscles.
Briefly describe the course of the glossopharyngeal nerve (CN IX)?
CN IX emerges through the jugular foramen and travels downwards between IJV and ICA, innervates the tongue, pharynx and (together with vagus nerve) the carotid body and sinus via carotid sinus nerve
Briefly describe the course of the vagus nerve (CN X)
CN X emerges through jugular foramen and travels within carotid sheath- gives rise to pharyngeal and laryngeal nerves (recurrent laryngeal nerves) and innervates the carotid body and sinus with CN IX
Briefly describe the course of the accessory nerve (CN XI)
CN XI emerges through the jugular foramen and travels downwards between IJV and ICA, crosses lateral surface of IJV to descend to posterior triangle of the neck. Innervates SCM and trapezius
Briefly describe the course of the hypoglossal nerve (CN XII)
CN XII exits the hypoglossal canal between IJV and ICA and crosses these arteries to enter the oral cavity.
this nerve has no branches in the anterior triangle of the neck.
Which nerve supplies cutaneous innervation over SCM and anterior triangle of the neck?
From where does this nerve arise?
The transverse cervical nerve supplies cutaneous innervation over the SCM and anterior triangle of the neck - this nerve arises from the anterior rami of C2 and C3
Which nerve innervates the infrahyoid muscles and where does this arise from?
Ansa cervicalis innervates the infrahyoid muscles- this is formed of the anterior rai of C1-C3 and loops around the carotid sheath at the second level loop of the cervical plexus
What is the cervical plexus?
The cervical plexus is formed by the anterior rami of C1, C2-4 and innervates the infrahyoid muscles, diaphragm (via phrenic nerve) and the skin of anterior / lateral neck and inferior head.
What is the brachial plexus?
The brachial plexus is a network of nerves which starts at C5-T1 and innervates the upper limbs.
Describe the course of the phrenic nerve
The phrenic nerve arises from the cervical plexus at C3-5 and travels down the anterior scalene and towards the thorax to provide motor innervation of the diaphragm.
