7.12 Regions of the Neck Flashcards
The neck is composed of a series of tubes passing between head above and thorax below. These tubes have spaces in between them. What is the clinical significance of this?
These spaces between the compartments of the neck t are in direct communication with the mediastinum. Thus any collection of infection in the neck will tract down causing mediastinitus
What are the anterior borders of the neck?
From the lower border of mandible down to the manubrium
What are the posterior borders/extreminities of the neck?
From the superior nucal line down to the C7-T1 disc
The superficial fascia of the neck is unique to the body. Why is this?
It contains a thin sheet of subcutaneous muscle called platysma. It comes up and blends with the muscle of the face (and thus shares facial muscle nerve supply)
This muscle is thus considered a muscle of facial expression
There is vasculature running through the superficial fascia making up the superficial vaculature of the neck.
Describe the superficial veins [2]
- External jugular vein descending laterally down the neck from the angle of the mandible veritcally on SCM
- The anterior jugular vein descends vertically on either side of the midline
What are the layers/compartments of the neck? Label a cross sectional diagram
- Superficial fascia with platysma
- Investing fascia
- Visceral (pre-tracheal) fascia
- Carotid sheath/vascular fascia
- Pre-vertebral fascia
What structures are in each of the layers of fascia?
Superficial:
Platysma
Investing layer:
Just under skin and sup. fascia which completely surrounds the neck: splits and encloses trapezius posteriorly and SCM anteriorly.
Visceral/pre-tracheal layer:
Thyroid, parathyroid, thymus (preadolescence), trachea and oesophagus and recurrent laryngeal nerve (note: only the thyroid/parathyroid are enclosed by the fascia)
Carotid:
Contains the common carotid arteries, the internal jugular veins and the vagus nerve
Pre-vertebral:
Surrounds the cervical vertebra and postural muscles
Draw the layers of fascia onto a saggital section of the neck
The visceral compartment is surrounded by the pre-tracheal fascia. Describe the vertical borders of this fascia
It extends right up to the hyoid bone and runs down encompassing the visceral structures within it (thyroid and parathyroid glands mainly) to blend with the fascia of the arch of the aorta
What is the significance of the pre-vertebral fascia attaching to the hyoid bone?
Anything that pretracheal envelops will move up and down with swallowing
this is an important clinical sign when diagnosing lumps in the neck
Describe the buccopharyngeal fascia
The pre-tracheal fascia envelops the thyroid gland only. Surrounding the posterior part of the visceral part of the neck there is an extra layer of fascia.
Together they enclose the visceral compartment such that it contains the oesophagus, trachea and recurrent laryngeal nerve.
The BP fascia deliniates pretracheal with prevertebral
Name and Describe the regions of the neck
Anterior triangle
- In front sternocleinomastoid muscle, below the inferior border of the mandible and behind of the midline of the neck
Posterior triangle
- Behind SCM, in front of trapezius muscle and and above middle third of clavicle
How are the muscles of the anterior triangle of the neck groups?
According to their relationship to the hyoid bone:
- Above the hyoid bone: Suprahyoid muscles
- Below the hyoid bone: Infrahyoid muscles
Between what fascial layers do the muscles of the anterior triangle of the neck sit in?
Between the investing fascia & pretracheal fascia
Describe the connections of the suprahyoid muscles
What is their function?
- Connecting the hyoid bone to the scalp (floor of the mouth)
- Funtion to elevate the hyoid and the larynx (swallowing and phonation)
What is a common anatomical term to describe the infrahyoid muscles of the anterior triangle of the neck? Why is this so?
Strap muscles
They all are characteristically long and thin
What are the connections of the infrahyoid muscles?
What are their functions?
Connect hyoid bone (anchoring it) to the sternum, clavicle and scapula (essentially to the pectoral girdle).
They depress the hyoid and the larynx
Describe the path of the common carotid artery and its bifurcation site
Common carotid-passes in carotid sheath, on the lateral sides of the neck. It ascends to level of C3/4 (upper border thyroid cartilage) where it bifurcates into the internal carotid artery and external carotid artery
What is an important feature of the internal carotid artery in terms of its course through the neck?
It has no branches in neck
It contains the carotid sinus (baroreceptors) & carotid body (chemoreceptors)
What are the three branches coming off the anterior aspect of the external carotid artery in the neck?
In order from first to last as the external carotid artery ascends:
- Superior thyroid artery that turns down and supplies thyroid from above.
- Lingual artery heads towards the tongue.
- Facial artery: winds around the inferior border of the mandible and has tortuous course to the face towards middle inner angle of the eye
What are the two branches of the external carotid artery as it ascends in the neck?
- Occipital artery arranged around the posterior belly of trigastric muscle
- Posterior auricular artery that heads towards the back of the ear
What is the deep branch given off the external carotid artery in the neck?
The ascending pharyngeal artery that runs up to supply the centrally placed structures of the neck (and head)
What is the major vein running down the neck? Describe its position
Internal Jugular Vein
It descends lateral to the common carotid artery in the carotid sheath
The internal jugular vein exits the skull out of the internal jugular foramen and then descends out through the neck.
What other structures leave this foramen and into the anterior triangle??
- CN IX
- CN X
- CN XI
- And CNXII also comes out in the anterior triangle
Describe the path of the glossopharyngeal nerve in the neck
It exits the jugular foramen, goes forwards into the oropharynx (after giving its branch to the carotid sinus) to supply the muscles of the neck, and posterior third of the tongue
Describe the path of the vagus nerve in the neck
What are its major nerve fibre types to the neck?
It has a straight vertical descent within the carotid sheath (behind and between the vessels)
- somatic sensory-> mucous membrane of larynx
- branchial motor-> muscles of pharynx, larynx & soft palate
Describe the path of the spinal accessory nerve through the neck
What does the nerve supply?
It exits the jugular foramen and then immediately turns backwards and exits the anterior triangle of the neck by passing beneath SCM and enters the posterior triangle towards the trapezius muscle
It supplies SCM and trapezius as it passes through/to them
Describe the path of the hypoglossal nerve through the neck
What does the nerve supply?
It exits the hypoglossal canal at the top of the anterior triangle.
The nerve comes forward towards the oral cavity. It passes between the external carotid artery and internal jugular vein towards the tongue.
It supplies motor innervation to the tongue (Except the palatoglossus muscle)
Describe the gross anatomy of the thyroid gland
- 2 lobes between upper border of thyroid cartilage above & 6th tracheal ring below
- Isthmus, between 2nd & 3rd tracheal rings
- Enclosed by pretracheal fascia
What is present on the thyroid gland in 50% of individuals?
An extrapyramindal lobe ascending from the isthmus on the left
Describe the position of the thyroid gland in terms of the major structures around it
- It lies deep to the strap muscles
- Lateral to the tracheal and overlaps/adjacent to the carotid sheath
- Anterior to the oesophagus and trachea
Where are the parathyroid glands?
4 small glands (size of a pea) located on the posterior aspect of the lobes. The positions are variable especially for the 2 inferior parathyroids
The thyroid gland is the most vascular gland of the body
Describe the blood supply to the thyroid gland
- Paired superior thyroid arteries (the 1st branch of external carotid artery)
- Paired inferior thyroid arteries (branch of subclavian a.)
These branches have a rich anastomoses vertically & across midline
10% of people have an additional blood supply to the thyroid. What and where is this and what is a clinical consideration?
A single thyroid ima artery that arises from the arch of the aorta (or from a branch off it) and ascends straight up to the isthmus (important to surgical tracheostomy)
Describe the development of the thyroid gland, what embryological remnant is left behind as a landmark of this?
The thyroid develops as an outgrowth of the floor of the embryonic pharynx.
It descends down and divides into 2 lobes.
Site of development is perminantly marked by the foramen caecum on the tongue and the thyroglossal duct (usually disappears) marks the pathway down.
What is an abnormality of the thyroid gland (in terms of development)
Abberant tissue can appear along the path of development (it was meant to regress but didnt) these can function as thyroid tissue
Describe the “floor” of the posterior triangle of the neck
The floor looks into the vertebral compartment containing the vertebral muscles.
The muscles appear as a series of obliquely orientated muscles in particular levator scapulae and scalenus muscles
How do the deep muscles of the neck descend?
Pre- & post-vertebral muscles - pass almost vertically across 5-7 spinal segments
Describe the importance of the scalenus anterior and scalenus media as landmarks?
- Scalenus anterior separates the subclavian vein (in front) and artery (between it and scalenus media)
- Between the two muscles is the emergence of the bracheal plexus
Describe the deep lymph drainage in the neck
Deep cervical lymph drainage is along internal jugular vein
- Upper group (includes jugulo- digastric or tonsillar node – drains palatine tonsil)
- Lower group (includes supraclavicular – ‘final sentinel’ node - clinical significance)
