Anatomy : Head and Neck

Triangles of the Neck

Anatomists use the term triangles of the neck to describe the divisions created by the major muscles in the region. The side of the neck presents a somewhat quadrilateral outline, limited, above, by the lower border of the body of the mandible, and an imaginary line extending from the angle of the mandible to the mastoid process; below, by the upper border of the clavicle; in front, by the middle line of the neck; behind, by the anterior margin of the trapezius. This space is subdivided into two large triangles by sternocleidomastoid, which passes obliquely across the neck, from the sternum and clavicle below, to the mastoid process and occipital bone above. The triangular space in front of this muscle is called the anterior triangle of the neck; and that behind it, the posterior triangle of the neck.


  • The front, as opposed to the posterior. The anterior surface of the heart is toward the breast bone (the sternum).
  • nearer the front, especially situated in the front of the body or nearer to the head.
  • “the veins anterior to the heart”


Submandibular triangle contains the following:

  • Submandibular glands
  • Lymph nodes
  • Facial artery and vein

Carotid Triangle contains the following:

  • Common carotid artery
  • Internal and external carotid arteries
  • Internal jugular vein
  • Vagus nerve
  • Hypoglossal nerve

Anterior Triangle

  • A triangular region that is a landmark in the neck, has its apex at the sternum pointing downward, and is bounded in front by the anterior midline of the neck, behind by the anterior margin of the sternocleidomastoid muscle, and above by the inferior margin of the lower jaw — compare posterior triangle.
  • Conventional carotid endarterectomy surgically exposes the common and internal carotid arteries to remove atherosclerotic lesions

Internal Jugular Vein

  • The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck.
  • A site for insertion of a central line instead of subclavian vein

Muscular Triangle

  • The muscular triangle contains some muscles and organs – the infrahyoid muscles, the pharynx, and the thyroid, parathyroid glands. The boundaries of the muscular triangle are: Superiorly – hyoid bone. Medially – imaginary midline of the neck. Supero-laterally – superior belly of the omohyoid muscle.

It contains the following:

  • Infrahyoid muscles
  • Pharynx
  • Thyroid gland
  • Parathyroid glands


  • It contains the following: external jugular vein, subclavian vein, transverse cervical and suprascapular veins, subclavian artery, accessory nerve, cervical plexus, phrenic nerve, trunks of brachial plexus

External Jugular Vein

  • Superficial location makes it vulnerable to being severed
  • Lumen is held open by investing fascia resulting in an air embolism

Subclavian Vein

  • A site of access for a cental line
  • Puncture of subclavian artery and pneumothorax are two potential complications

Cervical Plexus

  • Cervical plexus nerve block used to anesthetize neck region
  • Anesthetic is injected over the posterior border of stercleidomastoid muscle at the junction of its superior and middle thirds

Compartments and Cervical Fascia

The 4Vs

  • Visceral – Referring to the viscera, the internal organs of the body, specifically those within the chest (as the heart or lungs) or abdomen (as the liver, pancreas or intestines).
  • Vascular (CCA and IJV) – In anatomy, the left and right common carotid arteries (carotids) are arteries that supply the head and neck with oxygenated blood; they divide in the neck to form the external and internal carotid arteries.
  • Vascular (CCA and IJV) –other side
  • Vertebral – The large opening between the vertebral arch and body is the vertebral foramen, which contains the spinal cord. In the intact vertebral column, the vertebral foramina of all of the vertebrae align to form the vertebral (spinal) canal, which serves as the bony protection and passageway for the spinal cord down the back.
  • irregular bone with a complex structure composed of bone and some hyaline cartilage, the proportions of which vary according to the segment of the backbone and the species of vertebrate.

Cervical Fasciae

  • The deep cervical fascia (or fascia colli in older texts) lies under cover of the platysma, and invests the muscles of the neck; it also forms sheaths for the carotid vessels, and for the structures situated in front of the vertebral column.
  • Superficial fascia contains the platysma muscle that runs over the sternocleidomastoid muscle
  • Deep fascia is divided into several distinct layers
  • Investing deep fascial layer contains sternocleidomastoid and trapezius muscles.
  • Pretracheal contains visceral neck region

Carotid sheath contains vascular neck region and 4 major structures:

  1. Common carotid artery and internal carotid artery
  2. Internal jugular vein
  3. CNX- vagus nerve
  4. Deep cervical lymph nodes

Prevertebral encloses the vertebral neck region (including the vertebra, spinal cord and associated muscles).


  • The pretracheal fascia is a portion of the structure of the human neck. It extends medially in front of the carotid vessels and assists in forming the carotid sheath.

Carotid Sheath

  • The carotid sheath is an anatomical term for the fibrous connective tissue that surrounds the vascular compartment of the neck. It is part of the deep cervical fascia of the neck, below the superficial cervical fascia meaning the subcutaneous adipose tissue immediately beneath the skin.


  • The Investing layer of deep cervical fascia is the most superficial part of the deep cervical fascia, and it encloses the whole neck.


  • The prevertebral muscles are a group of deep cervical muscles inside the neck located laterally at the upper vertebral column. They are enveloped by the prevertebral layer of the cervical fascia. Their main task is the bending forward of the skull (ventral flexion).

Fascial Spaces and Surgical Access to Trachea

  • Fascial spaces (also termed fascial tissue spaces or tissue spaces) are potential spaces that exist between the fasciae and underlying organs and other tissues. In health, these spaces do not exist; they are only created by pathology, e.g. the spread of pus or cellulitis in an infection.
  • Pretracheal space is area anterior to the trachea
  • Retropharyngeal space is a potential space of the head and neck, bounded by the buccopharyngeal fascia anteriorly and the alar fascia posteriorly. It contains the retropharyngeal lymph nodes.


  1. Infections in the pretracheal space may extend inferiorly into the anterior mediastinum
  2. If invasion occurs, cancer can spread into these potential fascial spaces
  3. Retropharyngeal space can spread down and infect the posterior mediastinum. Abscesses can form in this space

Surgical Access to Trachea


  • Can also be called cricothyrotomy or simply crike
  • is an incision made through the skin and cricothyroid membrane to establish a patent airway during certain life-threatening situations, such as airway obstruction by a foreign body, angioedema, or massive facial trauma. Cricothyrotomy is nearly always performed as a last resort in cases where orotracheal and nasotracheal intubation are impossible or contraindicated. Cricothyrotomy is easier and quicker to perform than tracheotomy, does not require manipulation of the cervical spine, and is associated with fewer complications. However, while cricothyrotomy may be life-saving in extreme circumstances, this technique is only intended to be a temporizing measure until a definitive airway can be established.
  • Horizontal incision of cricothyroid membrane
  • Immediately inferior to vocal folds


  • Upper is above isthmus of thyroid gland
  • Lower is below isthmus of thyroid gland

Thyroid Gland (Neck)

  • The thyroid is a butterfly-shaped gland that sits low on the front of the neck. Your thyroid lies below your Adam’s apple, along the front of the windpipe. The thyroid has two side lobes, connected by a bridge (isthmus) in the middle. When the thyroid is its normal size, you can’t feel it.
  • It is consisting of Right Lobe, Left Lobe, Isthmus

Relationship of recurrent Laryngeal nerves:

  1. Each recurrent laryngeal nerve travel in its respective tracheoesophageal groove.
  2. In jeopardy of injury during thyroidectomy

Recurrent Laryngeal Nerves

  • is a branch of the vagus nerve, supplies all of the intrinsic laryngeal muscles
  • they are called recurrent as they come off the vagus nerve and travel back upwards to either side of the trachea and larynx
  • the left recurrent laryngeal loops under the aortic arch whereas the right recurrent laryngeal nerve loops under the R subclavian artery


  • A goiter (GOI-tur) is an abnormal enlargement of your thyroid gland. Your thyroid is a butterfly-shaped gland located at the base of your neck just below your Adam’s apple. Although goiters are usually painless, a large goiter can cause a cough and make it difficult for you to swallow or breathe.
  • Multinodular




– Dysphagia (Difficulty of swallowing)

-Difficulty Breathing

Cold Nodule

  • A cold nodule is a thyroid nodule that does not produce thyroid hormone. On a radioactive iodine uptake test a cold nodule takes up less radioactive material than the surrounding thyroid tissue. A cold nodule may be malignant or benign. On scintigraphy cold nodules do not show but are easily shown on ultrasound.
  • Usually benign
  • Non functional
  • Odds of being malignant are greater than hot nodules


  • A thyroidectomy is an operation that involves the surgical removal of all or part of the thyroid gland. General, Endocrine or Head and Neck Surgeons often perform a thyroidectomy when a patient has thyroid cancer or some other condition of the thyroid gland (such as hyperthyroidism) or goiter.


  1. Goiter
  2. Cancer
  3. Persistent hyperthyroidism


  1. Bleeding
  2. Infection
  3. Hoarseness of the voice due to RLN damage
  4. Hypoparathyroidism because sometimes the parathyroid glands cannot be preserved during thyroidectomy

Stellate Ganglion Block

  • A stellate ganglion block (sympathetic block) is an injection of local anesthetic into the front of the neck. A stellate ganglion block is done to: Diagnose the cause of pain in the face and head, arms and chest.
  • Forms form the fusion of inferior cervical and first thoracic sympathetic ganglia
  • Located anterior to transverse process of vertebra CVII
  • Carotid tubercle-anterior tubercle of CVI transverse process
  • Important anatomic relationships in the area of the neck

Thoracic Outlet

  • The thoracic outlet is the ring formed by the top ribs, just below the collarbone. Thoracic outlet syndrome (TOS) occurs when nerves or blood vessels are compressed by the rib, collarbone or neck muscles at the top of the outlet.
  • It has the following boundaries: Manubrium, First ribs and First Thoracic vertebrae

Subclavian Vein

  • Passes through outlet
  • Lies anterior to anterior scalene muscle
  • Not with interscalene triangle

Thoracic Outlet Syndrome

  • Thoracic outlet syndrome is a group of disorders that occur when blood vessels or nerves in the space between your collarbone and your first rib (thoracic outlet) are compressed. This can cause pain in your shoulders and neck and numbness in your fingers.


  1. Cervical ribs
  2. Fibrous brands
  3. Hypertrophy of scalene muscles
  4. Anomalous muscle
  5. Pancoast tumor


  1. Numbness and pain along the medial arm, forearm and fourth and fifth digits
  2. Muscle weakness in the hand
  3. Swelling of an arm
  4. Pallor and coldness

Carotid Arterial System

  • It has eight branches which includes the following:
  • Superior thyroid artery
  • The superior thyroid artery is the first branch of the external carotid artery, arising just below the level of the greater horn of the hyoid bone. Then it descends along the lateral border of the thyroid, where it divides into many branches to supply the thyroid gland.
  • Ascending pharyngeal artery
  • The ascending pharyngeal artery is an artery in the neck that supplies the pharynx, developing from the proximal part of the embryonic second aortic arch. It is the smallest branch of the external carotid and is a long, slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and under the stylopharyngeus muscle. It lies just superior to the bifurcation of the common carotid arteries.
  • Lingual artery
  • The lingual artery (latin: arteria lingualis) is a branch of the external carotid artery that supplies the tongue and floor of the mouth. The lingual artery arises medially from the external carotid at the level of the greater cornu of the hyoid bone.
  • Facial artery
  • The facial artery (external maxillary artery in older texts) is a branch of the external carotid artery that supplies structures of the superficial face.
  • Occipital artery
  • The occipital artery arises from the external carotid artery opposite the facial artery. Its path is below the posterior belly of digastric to the occipital region. This artery supplies blood to the back of the scalp and sterno-mastoid muscles, and deep muscles in the back and neck.
  • Posterior auricular artery
  • The posterior auricular artery is a small artery that arises from the external carotid artery, above the digastric muscle and stylohyoid muscle, opposite the apex of the styloid process. It ascends posteriorly beneath the parotid gland, along the styloid process of the temporal bone, between the cartilage of the ear and the mastoid process of the temporal bone along the lateral side of the head. The posterior auricular artery gives off the stylomastoid artery, small branches to the auricle, and supplies blood to the scalp posterior to the auricle.
  • Maxillary Artery
  • The maxillary artery supplies deep structures of the face. It branches from the external carotid artery just deep to the neck of the mandible.
  • Superficial Temporal Artery
  • In human anatomy, the superficial temporal artery is a major artery of the head. It arises from the external carotid artery when it splits into the superficial temporal artery and maxillary artery. Its pulse can be felt above the zygomatic arch, above and in front of the tragus of the ear.

Superficial Temporal Arteries

  • In human anatomy, the superficial temporal artery is a major artery of the head. It arises from the external carotid artery when it splits into the superficial temporal artery and maxillary artery. Its pulse can be felt above the zygomatic arch, above and in front of the tragus of the ear.

Clinical Correlation

  1. Inflammation of the superficial temporal artery


  • Throbbing headache on involved
  • Scalp tenderness on involved side
  • Atheroscleorotic buildup


  • Sudden numbness or weakness
  • Difficulty Speaking
  • Visual Disturbances
  • Sudden Dizziness
  • Sudden Severe Headache

Four Branches of Subclavian Artery

  1. Costocervical Trunk – The costocervical trunk is a short artery that is one of three branches of the first part of the subclavian artery. It arises from the back of the subclavian near the medial margin of the scalenus anterior.
  2. Vertebral Artery – The vertebral arteries are major arteries of the neck. Typically, the vertebral arteries originate from the subclavian arteries. Each vessel courses superiorly along each side of the neck, merging within the skull to form the single, midline basilar artery.
  3. Thyrocervical trunk – The thyrocervical trunk is a branch of the subclavian artery arising from the first portion of this vessel, i.e. between the origin of the subclavian artery and the inner border of the scalenus anterior muscle. It is located distally to the vertebral artery and proximally to the costocervical trunk.
  4. Internal thoracic Artery– The internal thoracic artery (ITA), previously known as the internal mammary artery (a name still common among surgeons), is an artery that supplies the anterior chest wall and the breasts.

Vertebral Artery Syndrome

  • The vertebral artery is one of the main arteries located at the base of the neck. Vertebral artery compression syndrome is the decreased blood flow to the brain with certain head positions. The movement of the head may occlude the vertebral artery and cause dizziness, vertigo, or fainting.
  • Atherosclerotic lesions of the proximal vertebral artery
  • Dissection of vertebral artery proximal to it entering the transverse foramen

It may cause the following:

  • Dizziness
  • Diplopia
  • Bilateral Leg weakness
  • Hemiparesis
  • Numbness

Arterial Supply of the Brain

Circle of Willis

  • the brain that supplies blood to the brain and surrounding structures. It is a component of the cerebral circulation and is comprised of five arteries.
  • The two main pairs of arteries are the Internal carotid arteries (supply the anterior brain) and vertebral arteries (supplying the brainstem and posterior brain).

Cranial Fossae and Foramina

  • The cribriform foramina refer to numerous perforations in the cribriform plate of the ethmoid bone. They connect the anterior cranial fossa with the nasal cavity.
  • Cranial fossa is formed by the floor of the cranial cavity.
  • Cranial fossa is divided into three distinct part and can be referred to:
  • Anterior cranial fossa (fossa cranii anterior), houses the projecting frontal lobes of the brain
  • Middle cranial fossa (fossa cranii media), separated from the posterior fossa by the clivus and the petrous crest
  • Posterior cranial fossa (fossa cranii posterior), between the foramen magnum and tentorium cerebelli, contains the brainstem and cerebellum
  • In anatomy, a foramen (/fəˈreɪmən/; plural foramina, /fəˈræmɪnə/ or foramens /fəˈreɪmənz/) is any opening. Foramina inside the body of humans and other animals typically allow muscles, nerves, arteries, veins, or other structures to connect one part of the body with another.

Inferior View:

  1. Foramen Ovale– The foramen ovale is a hole in the wall between the left and right atria of every human fetus. This hole allows blood to bypass the fetal lungs, which cannot work until they are exposed to air.
  2. Foramen Spinosum– The foramen spinosum is a small circular foramen present posterolateral to the foramen ovale in the greater wing of sphenoid. The greater wing of sphenoid is a bony projection arising from both sides of the sphenoid body forming a part of the floor of the middle cranial fossa
  3. Foramen Lacerum – The foramen lacerum (Latin: lacerated piercing) is a triangular hole in the base of skull, located between the sphenoid, the apex of the petrous temporal and the basilar part of the occipital.
  4. Carotid Canal – The carotid canal is the passageway in the temporal bone through which the internal carotid artery enters the middle cranial fossa from the neck. The canal starts on the inferior surface of the temporal bone at the external opening of the carotid canal (also referred to as the carotid foramen).
  5. Stylomastoid Foramen – Stylomastoid Foramen is an opening located between the styloid and mastoid processes of the temporal bone, and it has some clinical significance in patients suffering from Bell’s Palsy which is the inflammation of the facial nerve at the point where it leaves the stylomastoid foramen.
  6. Jugular Foramen – The jugular foramen is a large foramen (aperture) in the base of the skull. It is located behind the carotid canal and is formed in front by the petrous portion of the temporal bone, and behind by the occipital bone; it is generally larger on the right than on the left side.
  7. Foramen Magnum – The foramen magnum (Latin: great hole) is a large oval opening (foramen) in the occipital bone of the skull in humans and various other animals. It is one of the several oval or circular openings (foramina) in the base of the skull.

Le Fort Fractures

  • A Le Fort fracture of the skull is a classic transfacial fracture of the midface, involving the maxillary bone and surrounding structures in either a horizontal, pyramidal or transverse direction.

Types of Intracranial Hemorrhage

  1. Epidural hematoma– Epidural hematoma is when bleeding occurs between the tough outer membrane covering the brain (dura mater) and the skull. Often there is loss of consciousness following a head injury, a brief regaining of consciousness, and then loss of consciousness again
  2. The condition occurs in one to four percent of head injuries.
  3. Subdural hematoma– A subdural hematoma (SDH) is a type of hematoma—usually associated with traumatic brain injury—in which blood gathers between the inner layer of the dura mater and the arachnoid mater. It usually results from tears in bridging veins that cross the subdural space.
  4. Subarachnoid hemorrhage- Subarachnoid hemorrhage (SAH) is a life-threatening type of stroke caused by bleeding into the space surrounding the brain. SAH can be caused by a ruptured aneurysm, AVM, or head injury. One-third of patients will survive with good recovery; one-third will survive with a disability; and one-third will die.
  5. intracerebral hemorrhage- Intracerebral hemorrhage (ICH), also known as cerebral bleed, is a type of intracranial bleed that occurs within the brain tissue or ventricles. Symptoms can include headache, one-sided weakness, vomiting, seizures, decreased level of consciousness, and neck stiffness. Often symptoms get worse over time.

Overview of the 7 Extraocular Muscles

Muscles that move the eyeball

  1. Superior Oblique– The trochlea of superior oblique is a pulley-like structure in the eye. The tendon of the superior oblique muscle passes through it. Situated on the superior nasal aspect of the frontal bone, it is the only cartilage found in the normal orbit. The word trochlea comes from the Greek word for pulley.
  2. Inferior Oblique – The inferior oblique is an extraocular muscle, and is attached to the maxillary bone (origin) and the posterior, inferior, lateral surface of the eye (insertion). The inferior oblique is innervated by the inferior branch of the oculomotor nerve.
  3. Superior Rectus – The superior rectus muscle is a muscle in the orbit. It is one of the extraocular muscles. It is innervated by the superior division of the oculomotor nerve (Cranial Nerve III).
  4. Inferior Rectus– The inferior rectus is one of the seven extraocular muscles and is primarily responsible for depressing the eye (downgaze). The inferior rectus is one of the four rectus muscles, which also include the superior rectus, the medial rectus, and the lateral rectus.
  5. Medial Rectus – The medial rectus muscle is a muscle in the orbit. As with most of the muscles of the orbit, it is innervated by the inferior division of the oculomotor nerve (Cranial Nerve III).
  6. Lateral Rectus – The lateral rectus is on the right side of the image. Figure showing the mode of innervation of the Recti medialis and lateralis of the eye.
  7. It is one of six extraocular muscles that control the movements of the eye. The lateral rectus muscle is responsible for lateral movement of the eyeball, specifically abduction.

Muscle that move the superior eyelid

  • Levator palpebrae superioris – The levator palpebrae superioris (Latin for: elevating muscle of upper eyelid) is the muscle in the orbit that elevates the superior (upper) eyelid.

Innervation of Extraocular Muscles

Innervation- Mnemonic

Innervation of LPS

  • CN III
  • Smooth muscle fibers passing from its surface maintain eyelid elevation
  • Sympathetic fibers
  • Lesion of sympathetic and CN III

Function of Extraocular Muscles

Muscles elevate and move

  • IO- up and out
  • SR- up and In

Muscles depress and move

  • SO- down and out
  • IR- down and in

Muscles that adduct and abduct

  • MR- adduction
  • LR- abduction

Oculomotor nerve palsy

  • Oculomotor nerve palsy is an eye condition resulting from damage to the third cranial nerve or a branch thereof. As the name suggests, the oculomotor nerve supplies the majority of the muscles controlling eye movements.


  • Infarction of midbrain
  • Berry aneurysm at junction of posterior communicating artery and internal carotid
  • Lesions of the cavernous sinuses
    • Neoplasm
    • Inflammatory
    • Vascular

Trochlear nerve palsy 


  • Head Trauma
  • Tumor of skull base
  • Microvasculopathy
  • Idiopathic

Abducent nerve palsy

– Sixth nerve palsy, or abducens nerve palsy, is a disorder associated with dysfunction of cranial nerve VI (the abducens nerve), which is responsible for causing contraction of the lateral rectus muscle to abduct (i.e., turn out) the eye.


  • Involved eye is directed medially