Summary terms-head and neck



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SUMMARY TERMS-HEAD AND NECK
ARTERIES:
Arch of the Aorta- branches from right to left:

Brachiocephalic artery:

Right common carotid artery

Right subclavian artery

Left common carotid artery

Left subclavian artery
Subclavian artery:

Location- divided into 3 parts by the anterior scalene muscle that crosses anterior to the artery. The 3 parts are defined by their relationship to the anterior scalene:

Medial (first) part- gives off 3 branches:

Vertebral- arises from first part of subclavian artery; ascends through the transverse foramina in the upper 6 cervical vertebrae; enters the head via the foramen magnum and joins the vertebral artery from the other side to form the basilar artery; contributes to cerebral arterial circle

*Thyrocervical trunk- arises from the first part of the subclavian artery; gives off branches to the upper limb musculature as well as the inferior thyroid gland. Branches are:

*Suprascalpular artery- passes anterior to the scalenus anterior muscle in front of the phrenic nerve

*Transverse cervical artery- passes anterior to the scalenus anterior muscle in front of the phrenic nerve

*Inferior thyroid artery: supplies the inferior part of the thyroid gland and is important because its course crosses the recurrent laryngeal nerve which is located in the tracheoesophageal groove and may be injured when the inferior thyroid artery is ligated during thyroidectomy

*Ascending cervical artery- arises from the thyrocervical trunk or the inferior thyroid artery sometimes and courses along the anterior surface of the scalenus anterior muscle with the phrenic nerve

Internal thoracic artery- arises from the first part of the subclavian artery and descends inferiomedially into the thorax. It runs parallel to the sternum and gives of anterior intercostal branches to the first 6 ribs



Deep or posterior (second) part- gives off the costocervical trunk. The costocervical trunk gives off the deep cervical artery, which supplies deep neck muscles and fascia.

Lateral (third) part- gives off the dorsal scapular artery
*Common Carotid artery- arises from the brachiocephalic trunk on the right and from the aortic arch on the left. Gives off no branches in the neck but ascends the neck in the carotid sheath and divides into the internal and external carotid arteries at the level of the hyoid bone at C3. The common carotid artery lies medial to the internal jugular vein. Important structures at the bifurcation:

The carotid body- contains chemoreceptors

The carotid sinus- contains pressoreceptors

The chemo- and pressoreceptors are important in reflex control of cardiac output. The branches of the common carotid are:



*External carotid artery- has approximately 8 branches which supply external structures of the skull and neck from the upper border of the thyroid cartilage to the neck of the mandible; branches within the carotid triangle are:

*Superior thyroid artery:

Location: usually the most inferior branch; arises from the anterior border of the external carotid artery and passes inferiorly; gives off superior laryngeal nerve

Supplies: superior part of thyroid gland

*Lingual artery:

Location: arises from the external carotid artery near the tip of the greater horn of the hyoid bone, and passes along the inferior border of the posterior belly of the digastric muscle medial to the hypoglossal nerve (CN XII); disappears under the hypoglossus muscle on its way to the tongue

Supplies: the tongue

*Facial artery:

Location: arises just superior to the origin of the lingual artery or it may arise from a common origin with the lingual artery; passes deep to the posterior belly of the digastric and stylohyoid muscles and then curves over the mandible at the anterior edge of the masseter

Supplies: facial structures

*Occipital artery:

Location: arises from the posterior aspect of the external carotid artery and runs superiorly and medially into the occipital region

Supplies: neck and scalp, gives a muscular branch to the sternocleidomastoid muscle

*Ascending pharyngeal artery:

Location: small, slender branch; arises from the medial aspect of the external carotid artery

Supplies: pharynx and meninges

Other branches of the external carotid are:

Posterior auricular artery- ascends posteriorly to supply the parotid gland, adjacent muscles and scalp

*Maxillary artery- one of the terminal branches of the external carotid; passes posterior to the neck of the mandible to enter the infratemporal fossa

Superficial temporal artery- one of the terminal branches of the external carotid; ascends anterior to the ear into the scalp

Internal carotid artery- has no branches in the neck and is larger and posterior to the external carotid artery. Enters the carotid canal (temporal bone) and continues into the middle cranial fossa. The internal carotid plexus, composed of postganglionic sympathetic fibers, surrounds this vessel. Branches of the internal carotid carry these fibers to effector structures in the head. It contributes to the cerebral arterial circle.
Cerebral arterial circle (of Willis)-p. 698-Moore:

Location: around the base of the brain within the cranium. The brain is a highly metabolic organ and receives 20-25% of the blood supply. The cerebral arterial circle is anatomically complete in 90% of people but is probably functionally competent in less than 25%.

Formed by: anterior part of circle receives contributions from the internal carotids; posterior part of the circle receives contributions from the vertebral arteries. The actual circle consists of:

*Posterior cerebral arteries

*Posterior communicating arteries- joins posterior cerebral arteries with internal carotid arteries

*Internal carotid arteries

*Anterior cerebral arteries-join internal carotid arteries with anterior communicating artery

*Anterior communicating artery

Components of the cerebral arterial circle are prone to formation of berry aneurysm, which may rupture and produce a subarachnoid hemorrhage.

Contributors:

*Vertebral artery- the 2 vertebral arteries give off *posterior inferior cerebellar arteries (PICA) before fusing together to form the basilar artery

*Basilar artery- gives off:

*Anterior inferior cerebellar arteries (AICA)- which gives off labyrinthine artery that enters internal auditory meatus

*Superior cerebellar arteries- joins AICA

*Posterior cerebral arteries-

*Internal carotid artery- after leaving the carotid canal, the vessel traverses the foramen lacerum, ascends through the cavernous sinus and gives off the ophthalmic artery. Subsequently, it gives off the anterior cerebral artery and at this point the internal carotid artery continues as the middle cerebral artery.
Clinical notes:

A head injury can rupture cranial vessels. Types of hemorrhages:

Epidural hemorrhage- blood is confined between dura and bone

Subdural hemorrhage- blood is between dura and arachnoid

Subarachnoid hemorrhage- blood is between arachnoid and pia
Injury to the middle meningeal artery is a frequent cause of cranial epidural hemorrhage

Superficial Arteries of the Face:

*Facial artery:

Location: found within the submandibular triangle; crosses the inferior border of the mandible and passes in a groove on the deep surface of the submandibular gland onto the superficial face; the facial vein accompanies it



*Transverse facial artery:

Location: superior and parallel to the parotid duct (difficult to identify)



*Superior and inferior labial arteries:

Location: superior and inferior to the lips



*Angular artery- terminal branch of the facial artery

Location: passes lateral to the nose



*Superior laryngeal artery:

Arises from: superior thyroid artery

Location: accompanies the superior laryngeal vein and internal laryngeal nerve to pierce the thyrohyoid membrane
*Internal thoracic artery:

Location: originates from the inferior aspect of the subclavian artery, opposite the origin of the subclavian trunk, and passes into the superior thoracic aperture to the anterior aspect of the thoracic wall
*Vertebral artery:

Location: medial and deep to the thyrocervical trunk. It passes superiorly in the triangular-shaped region between the longus colli muscle medially and the scalenus anterior muscle laterally. The transverse process of the C6 vertebra is at the apex of this triangle. The vertebral artery enters the foramen transversarium of the C6 vertebra and is accompanied by the vertebral vein
*Deep temporal vessels and nerve- supply the temporalis muscle from its deep surface; these are cut in lab
*Maxillary artery:

Location: enters the infratemporal fossa by passing posterior to the neck of the mandible; terminal branch of external carotid artery.

First part (most lateral)- gives off branches which pass through foramina:

Deep auricular artery- supplies the TM joint and external auditory meatus

Anterior tympanic artery- supplies tympanic membrane

*Middle meningeal artery- located between the two roots of the auriculotemporal nerve; it passes into the foramen spinosum to supply the dura

*Inferior alveolar artery- runs with the inferior alveolar nerve deep to the angle of the jaw and passes through the mandibular foramen to supply the lower jaw and teeth

Second part (medial to the 1st part)- branches supply blood to the muscles of mastication derived from the first branchial arch and the buccinator muscle:

Temporal artery- supplies temporalis muscle

*Masseteric artery- vessels and nerve pass through the mandibular notch and enter the deep surface of the masseter muscle; these are cut in lab

Pterygoid arteries- supplies medial and lateral pterygoid muscles



*Buccal artery- nerve and artery usually pass between the 2 heads of the lateral pterygoid muscle and supplies the buccinator muscle and cheek mucosa

Third part (deepest and most medial)- gives off arteries that pass through bone usually in company with branches of the maxillary (V2) division of the trigeminal nerve:

*Posterior superior alveolar artery- supplies the upper jaw and teeth

Infraorbital artery- passes through the infraorbital fissure and canal onto the face



Descending palatine artery- descends through the greater palatine canal to supply the hard and soft palate and gives off a branch to the pterygoid canal

Sphenopalatine artery- supplies the lateral nasal wall and nasal septum
CARTILAGES:
*Alar- paired, u-shaped cartilages that determine the shape of the nose and are the principal elements in the formation of the nares
*Septal- unpaired, midline cartilage
*Lateral nasal-paired cartilages located at the superior border of the septal cartilage
CRANIAL FOSSA:
*Dura mater- the outer of the 3 coverings of the brain; composes of 2 layers:

Outer (periosteal) layer- continuous with the periosteum and adheres intimately to the cranial bones; also called endocranium

Inner (meningeal) layer- in contact with the thin underlying arachnoid mater
*Epidural space- space between inner surface of calveria and the periosteal layer
*Middle meningeal arteries- right and left supply blood to the dura mater and cranial bones
*Arachnoid granulations- located on surface of dura mater
*Sharpey's fibers- located on surface of dura mater; secures the dura to the calvaria
*Arachnoid mater- located deep to the dura mater
*Subdural space- space between the arachnoid mater and the dura mater
*Pia mater- deep to the arachnoid mater; lies directly on the surface of the brain and follows all its contours
*Subarachnoid space- space between the arachnoid and pia mater; contains CSF
*Falx cerebri- extends between right left and right cerebral hemispheres
*Tentorium cerebelli- a projection of dura mater which lies between the cerebral hemispheres and the cerebellum; its free edge forms the tentorial notch
*Falx cerebelli-
Brain and brain stem regions:
*Cerebral hemispheres
*Cerebellum
*Medulla oblongata
*Pons

*Midbrain
*Mammillary bodies
*Pituitary stalk
Cranial Nerves on inferior surface of brain and in cranial cavity:

*Olfactory bulb and olfactory tract (CN I)-
*Optic nerve (CN II) and optic chiasm
*Oculomotor nerve (CN III)
*Trochlear nerve (CN IV)
*Trigeminal nerve (CN V)

*Abducens nerve (CN VI)
*Facial nerve (CN VII)- facial nerve proper (motor root) and nervous intermedius (sensory root)
*Vestibulocochlear nerve (CN VIII)
*Glossopharyngeal nerve (CN IX)
*Vagus nerve (CN X)
*Spinal accessory nerve (CN XI)- cranial root and spinal root
*Hypoglossal nerve (CN XII)
Arteries on the inferior surface of the brain:
*Vertebral artery- right and left; also locate in the cranial cavity
*Basilar artery- also locate in the cranial cavity
*Posterior cerebral artery

*Posterior communicating artery
*Internal carotid artery- also located in the cranial cavity
*Middle cerebral artery
*Anterior cerebral artery
*Anterior communicating artery
*Superior cerebellar artery
*Anterior inferior cerebellar artery
*Posterior inferior cerebellar artery
*Cranial fossa- anterior, middle, and posterior. Find within middle cranial fossa:

*Trigeminal ganglion (Gasserian)

*Ophthalmic division of the trigeminal nerve (V1)- before it enters the orbit via the superior orbital fissure

*Maxillary division of trigeminal nerve (V2)- before it enters the foremen rotundum

*Mandibular division of trigeminal nerve (V3) - before it enters the foreman ovale
*Diaphragm sellae- circular dural fold which covers the hypophyseal fossa
*Pituitary gland
DUCTS:
*Parotid duct:

Location: 2 cm inferior and parallel to the zygomatic arch; it crosses the superficial surface of the masseter muscle; at the anterior border of the masseter muscle, it pierces the buccinator muscle and enters the vestibule of the oral cavity opposite the second premolar tooth
*Thoracic duct:

Location: lies adjacent to the left side of the esophagus, as it emerges from the mediastinum through the superior thoracic aperture. It then passes superiorly and anteriorly to the subclavian artery to join the left subclavian or internal jugular vein
FASCIA:
Superficial fascia of the neck:

Contents: loose areolar tissue that contains cutaneous nerves and superficial veins. Most of the nerves are branches of the cervical plexus. The platysma muscle is also located in this layer.
Deep cervical fascia- consists of several cylindrical coverings. These connective tissue sheets have continuities and bony attachments that form fascial planes and compartments in the neck. The coverings of deep fascia are:

Investing fascia- encloses and covers structures in the neck. This tough, dense fascia is attached superiorly to the *superior nuchal line of the occipital bone, *mastoid process, and inferior border of the mandible. Inferiorly it attaches to the manubrium, clavicle, and spine of the scapula. The investing fascia exists primarily as a single sheet of connective tissue but splits to enclose the sternocleidomastoid and trapezius muscles. This layer also forms sheaths for the parotid and submandibular glands.

Prevertebral fascia- defines a smaller cylinder within the larger one formed by the investing fascia. It encloses the vertebral column and associated musculature. It is also drawn into the axilla on the brachial plexus and subclavian artery as the axillary sheath. Inflammation in the prevertebral fascia may spread through the retropharyngeal space to reach the thoracic cavity

Visceral fascia- lies in the central part of the neck and consists of 2 continuous fasciae:

Pretracheal fascia- anterior; surrounds thyroid gland, trachea, and esophagus

Buccopharyngeal fascia- posterior; covers pharynx and buccinator muscle

Retropharyngeal space- potential space that accommodates the movements of the pharynx during swallowing; located posterior to the buccopharyngeal fascia and anterior to the prevertebral fascia

Carotid sheath- Tubular, fascial condensation that extends from the base of the skull to the root of the neck. It invests and separates the common and internal carotid arteries, the internal jugular vein, and the vagus nerve (CN X) as they course through the neck. Often, the superior root of the ansa cervicalis complex lies in the sheath anterior to the carotid artery. The cervical sympathetic trunk is located posterior to the sheath but is NOT included within it.
FORAMEN:
*Supraorbital foramen-passageway for the supraorbital nerve [sensory branch of the ophthalmic nerve (V1)]
*Infraorbital foramen- passageway for the infraorbital nerve [sensory branch of the maxillary nerve (V2)]
*Mental foramen- passageway for the mental nerve [sensory branch of the mandibular nerve (V3)]
*Stylomastoid foramen- the main trunk of the facial nerve (CN VII) passes through here before it gives branches to the superficial face
*Foramen transversarium of cervical vertebra-the vertebral artery passes through C1-C6 on its way to the skull
*Superior orbital fissure- The frontal, lacrimal, and nasociliary branches of the ophthalmic nerve (V1), oculomotor nerve (CN III), trochlear nerve (CN IV), abducens nerve (CN VI), and the superior opthalmic vein pass through it into the orbit.
*Foramen rotundum- the maxillary nerve (V2) passes through it
*Foramen ovale- the mandibular nerve (V3), the lesser petrosal nerve (branch of glossopharyngeal nerve- CN IX), accessory meningeal artery, and emissary veins pass through it
*Foramen spinosum- the spinous branch of mandibular nerve (V3) and the middle meningeal artery and vein pass through it
*Mandibular foramen- the inferior alveolar branch of mandibular nerve (V3) passes through it
*Internal auditory meatus- the facial nerve (CN VII), the vestibulocochlear nerve (CN VIII), and the labyrinthine artery pass through it
*Stylomastoid foramen- the facial nerve (CN VII) passes through it
*Foramen lacerum- the greater petrosal nerve (branch of facial nerve-CN 7) passes over but not through it
*Jugular foramen- the glossopharyngeal nerve (CN IX), the vagus nerve (CN X), the recurrent meningeal branch of the vagus, the spinal accessory nerve (CN XI), inferior petrosal sinus, sigmoid sinus, and posterior meningeal artery pass through it
*Foramen magnum- the vertebral arteries and medulla oblongata pass through it
*Carotid canal- the internal carotid artery with its sympathetic-postganglionic internal carotid plexus passes through it
Infratemporal fossa- irregular cube-like space:

Boundaries: Lateral- ramus of the mandible

Medial- lateral plate of pterygoid process (sphenoid bone)

Anterior- posterior wall of the maxilla

Posterior- condyler process of the mandible

Roof- greater wing (infratemporal crest) of the spenoid bone and the adjacent foramen ovale and foramen spinosum

Floor- attachment of the medial pterygoid muscle to the ramus of the mandible



Contents:

Muscles- inferior part of temporalis muscle and medial and lateral pterygoid muscles

Maxillary artery and branches

Pterygoid plexus of veins

Otic ganglion

Sensory and motor branches of mandibular nerve (V3)


Pterygopalatine fossa:

Location: it is a recess located medial to the infratemporal fossa and lateral to the nasal cavity

Connections:

Sphenopalatine foramen (located on the medial wall of the pterygopalatine fossa)- joins the nasal cavity to the pterygopalatine fossa



The pterygomaxillary fissure- joins the infratemporal fossa to the pterygopalatine fossa

Importance: the important parasympathetic pterygopalatine ganglion is suspended from maxillary nerve (V2) in the pterygopalatine fossa

GLANDS:
Parotid
*Thyroid gland:

Lobes- left, right, and sometimes a pyramidal lobe (embryological remnant of thyroglossal duct) extending superiorly from the isthmus

Isthmus- connects the left and right lobe of the thyroid; usually lies over the 2nd and 3rd tracheal rings

Note: In thyroidectomy, the infrahyoid muscles are highly transected and retracted inferiorly to retain their nerve supply. The recurrent laryngeal nerve is identified before any structures are clamped, transected, or ligated.
Parathyroid glands- small, brownish glands located on the posterior aspect of the thyroid lobes. There is usually a superior and an inferior parathyroid gland associated with each lobe but they are difficult to identify
LARYNX:
Location- lies in the neck between the 4th and 6th cervical vertebrae
Functions- regulating the airway and voice production. The larynx has a cartilaginous skeleton to maintain its patency for airflow, but the airflow may be decreased or completely cut off voluntarily by muscles controlling the vocal cords.



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