Week 2-Neck anatomy 1 Flashcards
What three regions does the neck connect?
What is it a collection of?
The neck connects the head upper thorax and upper limb
The neck is a collection of spaces and compartments separated by fascia.
Describe the superior boundary of the neck
Describe the inferior boundary of the neck
Superior boundary of the neck formed by the inferior mandible and base of the skill, along the pericranial line.
Inferior boundary of the neck: Extends down to the manubrium, the clavicle and acromion to the spinous process of C7. (Most prominent process in cervical spine)
What does the neck communicate freely with?
Why is this important?
The neck communicates freely with the thorax and mediastinum.
This is important when considering infection spread from the neck.
What divides the neck into two anatomical regions?
What are these regions called?
What do the muscles do?
Hyoid bone divides the neck into two regions.
Above hyoid = suprahyoid and muscle action here elevates the hyoid
Below hyoid = Infrahyoid, muscle action here depresses the hyoid
Label and decribe the muscle shown
What is the innervation of the muscle?
Muscle shown = Digastric, with anterior and posterior belly attached by central tendon. Central tendon is attached to the hyoid bone by a loop of tissue meaning it can elevate the hyoid.
Innervation: Different nerves innervate different muscle bellies due to embryological development from different pharyngeal arches.
Digastric anterior belly -> CN V3/c
Digastric posterior belly –> CN VII
Label and describe innervation of muscles shown
Large sheet of muscle = Mylohyoid, innervation CN V3/c
Muscle superior to the posterior belly of digastric = Stylohyoid, innervation CNVII
What is the naming convention of the muscles in the neck?
Many neck structures are named according to their attachments from inferior to superior
E.g: Thyrohyoid muscle (from thyroid cartilage to hyoid bone)
Sternothyroid (from sternum to the thryoid cartilage)
Sternohyoid (from sternum to hyoid bone)
Label the grey boxes: What are the muscles?
Omohyoid forms some of the boundaries of the triangles of the neck
Has both a superior belly and inferior belly.
Scalene muscles: anterior, middle and posterior scalenes.
What is the main nerve supply to many of the infrahyoid muscles?
What is the exception?
Main nerve supply to infrahyoid muscles is from the ansa (leather loop straps on sandal) cervicalis (C1-C3).
It is a fine loop of nerves that are part of the cervical plexus. Lies superficial to internal jugular vein in the carotid triangle.
Innervates most infrahyoid muscles: sternothyroid, sternohyoid, omohyoid.
Note thyrohyoid muscle is innervated by C1 spinal nerve via hypoglossal nerve.
What can be damaged during a carotid endartectomy?
What is the consequence?
The ansa cervicalis is often cut during carotid endarterectomy.
(carotid endarterectomy –> removal of atheromatous plaque in common carotid/ internal carotid to reduce risk of stroke and corrects stenosis).
Consequence of cutting ansa cervicalis is relatively minimal, may have dysphagia and dysphonia.
What do posterior neck muscles do?
Why are they quite commonly injured?
Posteriorly located muscles extend or laterally flex the neck, also supports the head against gravity.
As they are under tension most of the time they are quite commonly injured.
Muscular strain/ tears are a cause of posterior neck pain.
Label this structure
- Ligamentum nuchae –> part of supraspinous ligament
- Surgically useful –> provides avascular and aneural plane that can be cut to access the cervical spine
Label the image
Where does the suboccipital triangle sit?
What artery is located here?
What nerves are located here?
Suboccipital triangle sits under the occipital bone in the upper cervical region.
The vertebral artery sits here and is vulnerable to rupture during forced extension of head and neck –> potentially fatal.
C1-C3 nerves here. C1 has no sensory innervation but C2/C3 can.
Entrapment of C2 and C3 dorsal rami can produce a posterior headache / occipital neuralgia.
Occipital neuralgia = consistent and persistent very painful headaches, Tx surgically by releasing muscle entrapment.
What are the two main triangles of the neck?
What are there boundaries?
Neck is divided into 2 main triangles –> anterior and posterior
Anterior triangle boundaries:
Medial border = midline/ medial sagittal plane
Lateral border = Sternocleidomastoid
Superior border = inferior margin of mandible
Posterior triangle boundaries:
Medial = sternocleidomastoid (posterior border)
Lateral= Trapezius
Base = Clavicle (middle 1/3rd)
Apex = mastoid process
What forms the border of the anterior triangle?
What is it further divided into?
The anterior triangle borders are formed by the hyoid bone, the mandible and sternocleidomastoid. It is further divided into subtriangles: The submental triangle and submandibular triangle.
What are the boundaries of the submandibular triangle?
What are the boundaries of the submental triangle?
What is associated with both of these triangles?
Submandibular triangle boundaries are formed by the mandible and the two bellies of the diagastric muscle.
Submental triangle is formed by the hyoid bone, the anterior belly of digastric and the midline. OR can be defined as having two anterior bellies of digastric and the hyoid bone.
Associated with both are lymph nodes: Submandibular lymph nodes in submandibular triangle and submental lymph nodes in submental triangle.
Label the triangles of the neck
Anterior triangle subdivisions: Carotid triangle
What are the boundaries?
Carotid triangle:
Anterior boundary –> Omohyoid (superior belly)
Superior boundary = Digastric (Posterior belly)
Posterior boundary –> Sternocleidomastoid
Which landmarks are used to locate and examine the carotid artery?
What major structures pass through the carotid triangle?
Clinical relevance of carotid triangle?
Lateral to the trachea/ larynx, sits between larynx, trachea and mastoid.
Structures: common carotid, bifurcates around C3/4/ at the upper border of the thyroid cartilage into the internal and external carotid arteries.
Plus internal jugular vein, hypoglossal and vagus nerves.
Clinical relevance:
- many of vessels nerves are superficial and are accessed for surgery
- carotid triangle also contains carotid sinus (dilated portion of internal/ common carotid), contains baroreceptors that detect BP. CN IX feeds this info to the brain and regulates BP.
- In some patients baroreceptors are hypersenstive to stretch, external pressure can cause slowing of HR and decreased BP, underperfusion of the brain and syncope.
Anterior triangle subdivisions: Submandibular triangle
Borders?
What structures are located here?
Borders: Superior border = mandible
Inferior = two bellies of digastric (anterior and posterior)
Structures:
Submandibular lymph nodes, submandibular salivary glands, facial artery and vein also pass through here.
Anterior triangle subdivisions: Submental triangle
Borders?
Structures passing through?
Borders:
- Inferior –> Hyoid bone
- lateral –> Digastric anterior belly
- Medial –> Midline (if halved)
(Base of submental triangle bound by mylohyoid muscle, running from mandible to hyoid bone).
Structures:
- Submental lymph nodes (filter lymph draining from floor of the mouth/ tongue)
*
In which region does this mass sit?
What are some differentials?
Submental region mass
Differentials: Submental lymphadenopathy –> due to infection of mandibular teeth, floor of the mouth, gums, lips etc.
Diagnosis: Epidermoid cyst –> due to the fact its movable, squishy and moves with the skin
In which region/s are these neck lumps?
What is the likely cause of the lumps?
Submental, and submandibular triangle masses, plus deep lymph node group : jugulodigastric (where the jular vein is crossed by digastric muscle).
Cause: submental, submandibular and jugulodigastric lymphadenopathy
What divides the posterior triangle into two triangles?
Posterior triangle is subdivided into two smaller triangles by the inferior belly of omohyoid (Number 6 on the picture).
Divides into two triangles: 1) occipital 2) Omoclavicular/ supraclavicular triangle
What region sits between the two heads of the sternocleidomastoid muscle?
Which major vein sits deep to the sternocleidomastoid in this region?
The lesser supraclavicular fossa.
Inbetween the two heads of sternoclavicular muscle, sits the internal jugular vein.
Where are central venous cannulas in the neck classically inserted into?
What was the problem with inserting central cannula’s blind at one of these regions?
Classically central cannulas are inserted into the internal jugular vein using the lesser supraclavicular fossa as a guide.
Some were also inserted into the subclavian vein for central venous access. It used to be done blind, aiming under the clavicle at the midpoint of the upper manubrium.
Problem: Subclavian artery, apex of the lung and brachial plexus all sit here, high risk of injury.
Venous access: What vein can be used in an emergency?
External jugular vein can be cannulated in an emergency
What nerve plexus can be anaesthetised in the supraclavicular/ omoclavicular triangle?
The brachial plexus can be anaesthetised in the supraclavicular/ omoclavicular triangle.
What muscles form the floor of the posterior triangle?
Label the image
Floor of the posterior triangle is formed by prevertebral fascia overlying:
- Splenius capitis
- Levator scapulae
- Scalenes (anterior, middle and posterior)
- Omohyoid (inferior belly)
What are the boundaries of the posterior triangle?
What key neural structures pass through the posterior triangle? Where are they located?
What would occur if they were damaged?
Borders: posterior triangle
Anterior border = posterior edge of sternocleidomastoid
Inferior border = middle 1/3rd of clavicle
posterior border = anterior border of trapezius muscle
Neural structures:
-
Within interscalene groove: Brachial plexus
- Groove between scalenus anterior and medius can be palpated and used to locate brachial plexus, sits level with cricoid cartilage
- Superior trunk of brachial plexus is most superficial, root values of C5/C6, most likely part to be in lower neck damage
- Damage to the upper trunk causes: Arm hangs by side, Elbow cannot flex, Arm medially rotated, Forearm pronated, ‘waiter’s tip’ or more commonly known as ‘policeman position ‘ Loss of sensation over deltoid (C5) and lateral upper limb (C6).
- Phrenic nerve (C3/4/5) –> if damaged on one side of the neck present with hemidiaphragmatic palsy.
- Accessory nerve (CN XI) –> commonly damaged during neck dissection, consquence is loss of innervation of trapezius. Large muscle meaning loss of balance of shoulder region, risk of developing scoliosis and back pain.
Label the image
Large muscle anteriorly –> sternocleidomastoid
Large muscle posteriorly = trapezius
AS = anterior scalene
MS = middle scalene
PS = posterior scalene
Large structure between AS/MS is the emerging brachial plexus.
Neural structure superior to MS and PS = accessory nerve
What is the most superificial muscle in the neck? what is its innervation?
Most superficial muscle in the neck = platysma (enclosed in superficial fascia)
Innervated by facial nerve.
Label the image and describe the fascial layers after platysma and superficial fascia.
What is enclosed within the fascial compartments?
Immediately inwards from platysma and superficial fascia:
Investing fascia –> strong fascia around sternocleidomastoid, infrahyoid/ strap muscles and trapezius
Pretracheal fascia (orange) –> sits in front of trachea, houses thyroid gland and encopasses oesophagus. Pretracheal encloses oesophagus but also ascends to the base of the skull, therefore surrounds pharynx and extends to the mouth.
Here the fascia becomes the buccopharyngeal fascia (posterior portion of the pretracheal fascia).
Alar fascia —> fascial layer separating oesophagus/ pharynx/ larynx and vertebral column and muscles, separating it into two.
Carotid sheath (purple)–> wraps around the common carotid artery and internal jugular vein, and vagus nerve.
Prevertebral fascia (pink)–> surrounds the vertebral column and its muscles
Sympathetic chain (green) sits just outside of the carotid sheath inbetween the prevertebral fascia and alar fascia.
Compartments and spaces of the neck:
What compartment is enclosed by pretracheal and buccopharyngeal fascia?
What could be the consequence of a bleed in this compartment?
Pretracheal and buccopharyngeal fascia enclose the Visceral compartment (houses organs)
Consquence of bleed in visceral compartment: e.g. thyroid surgery with compartment closed but bleed occurs –> Compartment syndrome in compartment that houses trachea.
In thyroid surgery often do not fully close visceral compartment/ stitches can be released externally to release pressure in the case of a bleed.
Label the compartments
What is the arrow pointing to?
What muscles sit anterior and posterior to this structure?
What is this structure surrounded by and what is it continuous with?
Why is this important when considering infection spread?
Brachial plexus sits between anterior scalene (anterior to it) and middle scalene (posterior to it).
When brachial plexus enters the upper limb it pulls down with it a sheath of prevertebral fascia.
Brachial plexus is surrounded by the axillary sheath which is continuous with the prevertebral sheath. This means infections in the axilla can track up the plexus into the neck or vice versa, infection in the neck can track down into the limb.
What is the space in front of the trachea called?
What is the space posterior to the pharynx called?
What do these spaces communicate with?
Pretracheal space sits immediately anterior to the trachea. Communicates with the superior mediastinum, which is important to consider in infection spread.
The retropharyngeal space sits immediately posterior to the pharynx and also communicates with the superior mediastinum.
What is the Danger space?
Danger space = region posterior to the retropharyngeal space, sits between the alar fascia and the prevertebral fascia.
Runs from the skull base through the superior and posterior mediastinum to the diaphragm and offers little resistance against infection. Infection can track directly into the thorax and between L and R sides.
Infection here causes huge mediastinitus, unlikely to survive this.
Label the image
Label the image
What pathology is shown?
Retropharyngeal abscess:
Alignment of the pharynx is not right, less dense areas with air pockets behind the pharynx.
Swallowing will be affected for the patient, infection should be contained within the abscess but it can track down to the superior mediastinum as retropharyngeal space terminates here.
May be evidence of stridor
Why are fascial compartments of the neck useful during surgery?
During surgery structures in the neck can be moved within their fascial compartments and simply pushed aside to reach required structure. E.g. cervical vertebrae can be accessed from anterior perspective.
Label the lymph nodes shown and describe which regions of lymph drainage they receive
Where do all head and neck lymphatics eventually drain to?
Label the lymph nodes shown and what lymph regions drain to them?
All head and neck lymphatics eventually drain via deep cervical lymph nodes into the thoracic duct/ right lymphatic trunk.
Deep nodes:
- Jugulo-diagastric –> Receives lymph from tonsil, pharynx, posterior tongue
- Deep cervical chain –> receives from superficial lymph node groups
- Jugulo-omohyoid –> superficial node groups and central tongue
What is the classical disposition of the head and neck lymph nodes?
Head and neck lymph nodes sit in classical Z shpaed disposition although do not miss the superficial cervical chain over the jugular vein or the preauricular group.
Describe the location of this lump?
Which vessel has been cannulated?
What is the lump likely caused by? What would it feel like?
Patient with a muscular region anterior triangle neck lump.
Common carotid has been cannulated and contrast added (see bifurcation above). Large aneurysm shown. Would feel soft and pulsatile.
What is this patient suffering with?
where is the lump?
Stab wound attained 22 yrs previously, clot formation within the common carotid that dislodged and travelled to clot the right middle cerebral artery. Sx shown on the left hand side –> motor and sensory sx
Condition called a pseudoaneurysm:
is a collection of blood that forms between the two outer layers of an artery, the tunica media and the tunica adventitia.
usually caused by a penetrating injury to the vessel, which then bleeds, but forms a space between the above two layers, rather than exiting the vessel
Lump presenting in the anterior triangle within muscular triangle
Where does the carotid bifurcation normally sit?
Carotid bifurcation normally sits above the thyroid cartilage lamina in 80-91.6% of people OR at C3 in 45-62% of cases (range between C1-C5)
Carotid arteries: Label the image
- External carotid supplies many facial structures and neck structures e.g. thyroid
- Internal carotid supplies the CNS
- Common carotid bifurcates into internal and external
- Pulsation of common carotid can be felt in the carotid triangle
- Comon carotid ascends neck lateral to the larynx and pharynx
Where does the carotid sinus/body sit?
Carotid sinus and body sit close to carotid bifurcation
Carotid sinus located on proximal internal carotid, and senses blood pressure. Carotid massage on hypersensitive carotid sinus can lead to syncope. Avoid taking the pulse here in pts with unexplained syncope/ vascular disease.
Carotid body senses PO2, but also senses H+ and PCO2
Label the image and describe the arterial supply to the head and neck
- Common carotids: Right common carotid arises from bifurcation of brachiocephalic trunk, left common carotid arises direct from arch of aorta.
- L and R common carotids ascend up neck lateral to trahcea/ oesophagus, do not give any branches in the neck
- At level of superior thyroid cartilage/ C4 they bifurcate into external and internal carotid arteries in carotid triangle
- At bifurcation sits the carotid sinus
- External carotid artery supplies areas of head and neck external to the cranium, travelling posterior to mandibular neck but anterior to lubule of ear.
- External carotid artery ends within parotid gland, dividing into superficial temporal artery and maxillary artery.
- Facial and superficial temporal arteries supply superficial areas of face.
- Maxillary artery supplies deep structures of the face
- External carotid gives off: 1) superior thyroid artery 2) lingual artery (supplies tongue/ roof of mouth) 3) facial artery 3) ascending pharyngeal artery 5) occipital artery 6) posterior auricular artery
- Internal carotid artery enters cranial cavity via carotid canal in petrous temporal bone.
- Internal carotid supplies: Brain, eyes, forehead
- Vertebral arteries R and L arise off subclavian arteries, travel via foramen transversarium in cervical vertebrae, then enter cranial cavity via foramen magnum, unite to form basilar artery.
What are the arteries shown?
How to they act to supply the neck?
- R and L subclavian give rise to the thyrocervical trunk which gives off:
- Inferior thyroid artery supplies thyroid gland
- Ascending cervical artery suppled posterior prevertebral muscles
- Transverse cervical supplies trapezius and rhomboid
- Suprascapular artery supplies posterior shoulder
Label the veins of the neck
- Retromandibular vein passes through the parotid gland
