The parietal and occipital bones in particular are common regions for accessory sutures because of their multiple ossification centres.
The occipital bone has complex development, ossifying from six centres. The foramen magnum is surrounded by four ossification centres. On each side are the exo...
Accessory parotid glands are a normal variant and represent ectopic salivary tissue present away and separate from the main parotid gland 1.
Accessory parotid glands are not rare and are seen in ~20% of the general population 2.
Located on the masseter muscle, ante...
Agger nasi air cells are the most anterior ethmoidal air cells lying anterolateral and inferior to the frontoethmoidal recess and anterior and above the attachment of the middle turbinate. They are located within the lacrimal bone and therefore have as lateral relations the orbit, the lacrimal s...
The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge.
Head and neck anatomy
Abdominal and pelvic anatomy
Lower limb anatomy
Upper limb anato...
The ansa cervicalis is a component of the cervical plexus which gives muscular branches to the geniohyoid muscle of the suprahyoid group and all 4 of the infrahyoid muscles.
superior root: derived from the anterior primary rami of C1
inferior root: derived from the anter...
The anterior cervical space is a small infrahyoid compartment of the head and neck. It is a fat containing space and is not enclosed by fascia 1.
posterior: carotid space
medial: visceral space
superior: submandibular space
The anterior cranial fossa constitutes the floor of cranial vault which houses the frontal lobes of the brain.
Structures present in the midline of anterior cranial fossa from anterior to posterior are:
groove for superior sagittal sinus
groove for anterior meningeal vessels
The anterior jugular vein is a paired tributary of the external jugular vein.
Origin and course
The anterior jugular vein has its origin in the region of the hyoid bone or suprahyoid neck, as the confluence of several small superficial veins. It descends near the midline, medial...
The anterior lacrimal crest is a bony projection on the frontal process of the maxilla continuous with the orbital rim which creates the lateral margin of the lacrimal sac fossa. The medial palpebral ligament is attached to anterior lacrimal crest.
Immediately anterior to the anterior lacrimal ...
The anterior superior alveolar canal courses through the anterior wall of the maxillary sinus, and contains the anterior superior artery, vein and nerve. Usually, it shares a common channel with the infraorbital canal but when seen separately should not be confused for a fracture.
The arteries of the head and neck are branches of the common carotid and and subclavian arteries.
(1st part) mandibular...
The arytenoid cartilages are paired cartilages that articulate with the sloping upper border of the lamina of the cricoid cartilage by the cricoarytenoid joint. This joint allows movement of the arytenoid cartilages, which is vital in approximating, tensing and relaxing the vocal folds.
The ascending cervical artery is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery).
It is a small artery that ascends medial to the phrenic nerve on the prevertebral fascia. It contributes many small spinal branches into the intervertebral foramina of ...
The ascending pharyngeal artery, the smallest branch of the external carotid, is a long, slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and under the stylopharyngeus.
origin: a branch of the external carotid artery
course: vertically with...
The asterion is the the star shaped junction on the side of the calvarium where 3 sutures meet:
It is located at the the posterior end of the parietomastoid suture, where as the pterion is located at the anterior end.
It is one of...
The base of skull (or skull base) forms the floor of the cranial cavity and separates the brain from the structures of neck and face.
The base of skull is a bony diaphragm composed of number of bones including (from anterior to posterior):
The basion is the median (midline) point of the anterior margin of the foramen magnum.
It is one of the skull landmarks, craniometric points for radiological or anthropological skull measurement.
Various lines and measurements using the basion are made in the diagnosis of ...
Bill's bar is a landmark that divides the superior compartment of the internal acoustic meatus into an anterior and posterior compartment. Anterior to Bill bar, in the anterior superior quadrant, are the facial nerve (CN VII) and nervus intermedius, and posterior to it in the posterior superior ...
The body of the sphenoid bone is a cubical portion, hollowed by the sphenoid air sinuses.
The body has superior, inferior, anterior, posterior, and lateral surfaces.
The superior surface features:
ethmoidal spine: prominent spine that articulates with the cribiform plate and g...
Bouthillier et al described (in 1996) 1 a seven segment internal carotid artery (ICA) classification system. It remains the most widely used system for describing ICA segments at the time of writing (mid 2016).
There are few others classifications systems including proposed by Fisher (1938), Gi...
Useful mnemonics to remember the four branches of the thoracoacromial artery are:
CAlifornia Police Department
Cadavers Are Dead People
B: breast (pectoral)
CAlifornia Police Department
The bregma is the midline bony landmark where the coronal and sagittal sutures meet, between the frontal and two parietal bones.
It is the anterior fontanelle in the neonate and closes in the second 2 (typically around 18 months after birth).
It is one of the skull landmarks, craniometric poin...
The buccal space (or buccinator space) is one of the seven suprahyoid deep compartments of the head and neck.
The buccal spaces are paired fat contained spaces on each side of the face forming cheeks. Each space is enveloped by the superficial (investing) layer of the deep cervi...
The buccinator artery is a small branch from the second part of the maxillary artery. It runs obliquely forward, between the medial pterygoid and the insertion of the temporalis, to the outer surface of the buccinator, to which it is distributed, anastomosing with branches of the facial artery a...
The carina is part of the trachea and is an important reference point in chest imaging.
The carina is found at the base of the trachea and it is formed as the main bronchi divide into right and left branches.
The carina usually sits in the T4/T5 plane and is at the level of the ...
The caroticotympanic branch (tympanic branch) is a small branch from the C2 segment of the internal carotid artery. It is a vestigial remnant of the hyoid artery.
It passes posterolaterally into the middle ear cavity and anastomoses with the inferior tympanic artery (a branch of the external ca...
The carotid bifurcation is the point at which the common carotid artery terminates. As it does so, it forms the internal and external carotid arteries which go on to supply the head and neck.
It is closely related anatomically to the carotid body, a small group of chemoreceptors and supporting ...
The carotid body is located within the neck, and in close proximity to the carotid bifurcation. It is composed of a number of chemoreceptor cells and supporting matrix and detects changes in the composition of blood in the common carotid as it forms the internal and external carotid arteries.
The carotid canal is a passage within the petrous temporal bone and transmits the internal carotid artery and sympathetic plexus. Its inferior opening is called the carotid foramen and is situated anteriorly to the jugular fossa and medially to the tympanic plate. The carotid canal is initially ...
The carotid space is one of the seven deep compartments of the head and neck.
The carotid space is a roughly cylindrical space that extends from the skull base through to the aortic arch. It is circumscribed by all three layers of the deep cervical fascia, forming the carotid sh...
Cervical lymph node groups describe the anatomic position of the nodes. It differs from cervical lymph node levels, covering all lymph nodes not just those relevant to head and neck surgery.
Groups described in the literature include but are not limited to:
The cervical plexus is formed by the ventral (anterior) rami of the C1 to C5 nerve roots and innervates the diaphragm, provides motor supply to some neck muscles and cutaneous sensation to the skin of the head, neck and chest.
anterior rami of C1 to C5 nerves
Chorda tympani is a nerve that arises from the mastoid segment of the facial nerve carrying afferent special sensation from the anterior two-thirds of tongue via the lingual nerve as well as efferent parasympathetic secretomotor innervation to the submandibular and sublingual glands.
Cloquet's canal, also known as the hyaloid canal or Stilling's canal, is a transparent canal that runs from the optic nerve disc to the lens traversing the vitreous body. It serves as a perivascular sheath surrounding the hyaloid artery in the embryonic eye.
The cochlea is part of the inner ear osseous labyrinth found in the petrous temporal bone.
The cochlea is a shell-shaped spiral that turns between two-and-a-half and two-and-three-quarters times around the modiolus (a central column of bone).
The cochlear promontory is the name given to the bone that overlies the basal turn of the cochlea protruding into the middle ear cavity.
glomus tympanicum paragangliomas typically arise in the region of the cochlear promonotory
The colliscalene triangle is an important anatomical region of the neck, situated medial to the scalenus anterior muscle.
medial: lateral border of longus colli
lateral: medial border of scalenus anterior
inferior: first part of the subclavian artery
apex: carotid ...
The common carotid artery is a paired structure that supplies blood to the head and neck.
origin: branch of the aorta (left) and brachiocephalic trunk (right)
course: posterior to sternoclavicular joint, lateral to thyroid and trachea
supply: head and neck
main branches: none (usua...
Concha bullosa (also known as a middle turbinate pneumatisation) is a common finding and although associated with deviation of the nasal septum, it is usually of little clinical importance.
Concha bullosa is a normal variant and is one of the most common variations of sinonasal an...
The condylar canal (canalis condylaris) is located in the condylar fossa, posterior to the occipital condyles. It transmits the emissary veins which originate at the sigmoid sinus and drain into the occipital vein.
The condylar canaI has a variable presence and seen only in ~55% (range 50-60%) ...
Congenital absence of the internal carotid artery (ICA) is a rare anomaly that occurs in less than 0.01% of the population. It encompasses agenesis, aplasia, and hypoplasia 1.
The most common type of collateral flow is through the circle of Willis, through the anterior communicating artery (ACO...
The coronal suture is the cranial suture formed between the two parietal bones and the frontal bone. At the junction of coronal, sagittal and frontal sutures is the anterior fontanelle which is open at birth and usually fuses at around 18-24 months after birth.
Fusion of the coronal suture occu...
The corrugator supercilii are two small, triangular muscles that allow facial expression through movement of the eyebrows, including frowning. They originate from the medial end of the supraorbital margins and insert deep to and can cause traction on the skin over the middle of the supraorbital...
The costocervical trunk is one of the branches of the second part of the subclavian artery. It arises from the posterior wall of the subclavian artery, posterior or medial to the anterior scalene muscle and courses posterosuperiorly across the suprapleural membrane where it divides into 2 branc...
The cribriform plate is a sieve-like structure between the anterior cranial fossa and the nasal cavity. It is a part of ethmoid bone and supports the olfactory bulb. It is perforated by foramina for the passage of the olfactory nerves and the nerves to the upper part of the nasal septum, the lat...
The cricoid cartilage is a ring shaped structure that sits just below the thyroid cartilage. It is the only complete cartilaginous ring of the whole airway.
The anterior portion is called the arch and the posterior quadrangular shaped portion is the lamina. It articulates with th...
The crista galli is a thick, midline, smooth triangular process arising from the superior surface of the ethmoid bone, projecting into the anterior cranial fossa. It separates the olfactory bulbs, which lie either side of it in the olfactory fossae of the cribriform plate. It serves as an anteri...
The danger space is a potential space located behind the true retropharyngeal space, which connects the deep cervical spaces to the mediastinum.
anteriorly: alar fascia
posteriorly: prevertebral layer of the deep cervical fascia
The deep cervical fascia consists of 3 separate but related fascial layers that encircle structures in the neck and allow anatomic compartmentalisation. All 3 layers meet to form the carotid sheath. From superficial to deep, the 3 layers are:
1. Investing layer of the deep cervical fascia is th...
Head and neck anatomy is described in slightly different terms in the radiology literature reflecting the importance of fascia lined spaces in confining various pathologies. As such the neck has been divided into a number of 'deep spaces' which overlap with traditional anatomical description.
The deep temporal arteries (anterior and posterior) are branches from the second part of the maxillary artery. They
ascend between the temporalis muscle and the pericranium supplying the overlying
branch communicates with the lacrimal artery by means of smal...
The Delphian node (prelaryngeal) along with paratracheal nodes, pretracheal nodes, perithyroidal nodes make up level VI cervical lymph nodes, and is not routinely excised in radical neck dissections. It receives lymph from the thyroid and larynx.
History and etymology
The Delphian node gains ...
The digastric muscle is composed of two bellies, anterior and posterior, connected by an intermediate round tendon. The two bellies of the muscle have different embryonic origins and hence are supplied by different cranial nerves.
anterior belly: mandible
posterior belly: mast...
Disc herniation refers to displacement of intervertebral disc material beyond the normal confines of the disc, but involving less than 25% of the circumference (to distinguish it from a disc bulge. A herniation may contain nucleus pulposus, vertebral endplate cartilage, apophyseal bone/osteophyt...
Dorello canal channels the abducens nerve (CN VI) from the pontine cistern to the cavernous sinus.
Dorello canal is found at the medial most end of the petrous ridge at the confluence of the inferior petrosal sinus, basal sinus and cavernous sinus.
The dorsum sellae is the square shaped process of the sphenoid bone. It ascends superiorly from the posterior part of the sphenoid body to form the posterior wall of the sella turcica.
The dorsum sellae forms the posterior wall of the sella turcica, which houses the pi...
The duct of Rivinus connects the sublingual gland to the floor of the mouth.
Despite its name, it is not a single duct, but numerous small ducts all of which open into the floor of the mouth and are collectively termed the duct of Rivinus.
The largest of these little ductules is the major duct...
The ducts of the salivary glands allow the passage of salivary juice from the glands to the oral cavity:
parotid duct (Stenson duct): connects the parotid gland to the buccal mucosa, adjacent to maxillary second molar
submandibular duct (Wharton duct): connects the submandibular gland to the f...
An ectopic thyroid gland is one which is located in a location other than the normal position anterior to the laryngeal cartilages.
The during embryological development, the thyroid gland migrates down from the foramen caecum at the posterior aspect of the tongue, to its permanent location. Thi...
The epiglottis is a leaf-shaped fibrocartilaginous structure that forms part of the supraglottic larynx and defines the division of the hypopharynx from the larynx.
The epiglottis projects posterosuperiorly from its stem-like base, which is attached to the thyroid cartilage. It ...
The ethmoid bone is a single midline facial bone that separates the nasal cavity from the brain and is located at the roof of the nose and between the two orbits. It is a cubical shape and is relatively lightweight because of its spongy construction. It contributes to the anterior cranial fossa....
The ethmoidal sinuses (or ethmoidal air cells) are one of the four paranasal sinuses. They are located within the ethmoid bone. They are present at birth and they develop rapidly from 0-to-4 year-old; they further mature from 8-to-12 year-old during puberty.
Some of the ethmoidal air cells have...
The Eustachian tube is the channel through which the tympanic cavity communicates with the nasopharynx. It is approximately 36 mm in length and is directed downward, forward, and medially, forming an angle of about 45 degrees with the sagittal plane and one of 30 to 40 degrees with the horizonta...
The external auditory canal (EAC) extends from from the tympanic membrane medially to the external auditory meatus (EAM) laterally. It is typically 2.5 cm in overall length. The lateral 1.5 cm are bounded by a fibrocartilaginous tube continuous with the auricle. The medial 1 cm is formed by the ...
The external carotid artery (ECA) is one of the two terminal branches of the common carotid artery. The other terminal branch is the internal carotid (ICA), which is somewhat larger than the ECA.
origin: bifurcation of the common carotid artery
course: under the submandibular gland an...
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The external jugular vein (EJV) drains the head, face and part of the pectoral region.
Origin and course
The posterior division of the retromandibular vein and posterior auricular vein unite to form the EJV at the angle of the mandible. It courses inferiorly in the subcutaneous ...
The extraocular muscles are the six muscles that control eye movements:
superior rectus: elevation
superior oblique: intorsion
medial rectus: adduction
lateral rectus: abduction
inferior oblique: extorsion
inferior rectus: depression
An extramural air cell is one that is not contained within its named parent bone. So, the infraorbital ethmoidal air cells that lie within the maxilla and not the ethmoidal bone are examples of extramural air cells.
Eye movements are a complex set of movements that are performed by the extra-ocular muscles that are grouped by the muscles that perform particular movements:
ocular internal rotators
ocular external rotators
The facial artery is one of the branches of the external carotid artery and supplies blood to the structures of the face.
origin - branch of the external carotid artery a little above the level of the lingual
course - ascends anteriorly through the cheek with a tortuous route towards ...
The facial bones comprise a set of bones that make up the face:
inferior nasal concha
zygoma (zygomatic bone)
Where these bones join each other, sutures occur.
The facial muscles enable facial expression and serve as sphincters and dilators of the orifices of the face. These muscles differ from those of other regions in the body as there is no deep fascia deep to the skin of the face; many of the facial muscles insert directly into the skin of the face...
The facial nerve is one of the key cranial nerves with a complex range of functions.
Although at first glance it is a motor nerve to facial expression, which begins as a trunk and emerges from the parotid gland as five branches (see facial nerve branches mnemonic here), it has taste and parasy...
There are many mnemonics to recall the branches of the facial nerve (superior to inferior) as they exit the anterior border of the parotid gland. Examples include:
Tall Zulus Bear Many Children
Two Zulus Bit My Cat
Two Zebras Bit My Coccyx
Ten Zebras Buggered My Car
To Zanzibar By Motor Car...
The falciform crescent is a horizontal ridge that divides the internal acoustic meatus into superior and inferior portions.
The facial nerve and superior vestibular nerve (SVN) travel in the superior portion of the IAM with the facial nerve
anterior to the SVN and separated from ...
The Fallopian (facial) canal refers to a bony canal through which the facial nerve traverses the petrous temporal bone, from the internal acoustic meatus to the stylomastoid foramen.
It is, for those of you fond of trivia, the longest bony canal through which a nerve passes. It is also responsi...
The fissula ante fenestram is a small connective tissue-filled cleft located where the tendon of tensor tympani turns laterally toward the malleus. It is situated immediately anterior to the oval window, and posterior to the cochleariform process 1.
The fissula ante fenestrum is the most commo...
The floor of mouth is an oral cavity subsite, and is a common location of oral cavity squamous cell carcinoma.
The floor of mouth is a U-shaped space extends (and includes) from the oral cavity mucosa superiorly, and the mylohyoid muscle sling 2,3.
The foramen caecum is located in the anterior cranial fossa, anterior to cribriform plate of ethmoid bone and posterior to the frontal bone, within the frontoethmoidal suture. It lies at a variable distance from the crista galli.
The foramen caecum is frequently found in infant, uncommonly in c...
Foramen caecum can refer to a number of different anatomical structures:
foramen caecum (tongue)
foramen caecum (anterior cranial fossa)
Foramen ovale is an oval shaped opening in the middle cranial fossa located at the posterior base of the greater wing of the sphenoid bone, lateral to the lingula. It transmits the mandibular nerve branch (V3) of the trigeminal nerve, accessory meningeal artery, emissary veins between the cavern...
The foramen rotundum is located in the middle cranial fossa, inferomedial to the superior orbital fissure at the base of greater wing of sphenoid. Its medial border is formed by lateral wall of sphenoid sinus. It runs downwards and laterally in an oblique path and joins the middle cranial fossa ...
The foramen tympanicum (also known as foramen of Huschke) is an anatomical variation in the external acoustic canal (EAC), where a bony defect connects the EAC to the temporomandibular joint (TMJ).
Various studies have reported on the occurrence of a foramen tympanicum in the asym...
A foveola pharyngica recess is one of the variants of the inferior median clival canal, thought to represent a remnant of the notocord. It represents a blind ending recess in the anteroinferior surface (nasopharyngeal) surface of the clivus 1,2.
The frontal bone is a skull bone that contributes to the cranial vault. It contributes to form part of the anterior cranial fossa.
The frontal bone has two portions
vertical portion (squama): has external/internal surfaces
horizontal portion (orbital): has superior/inferior sur...
The frontal sinus develops from anterosuperior pneumatisation of the frontal recess into the frontal bone. Development begins late in intrauterine life or may start after birth (from one to twenty years and starts in the vertical segment). Pneumatisation develops from one to twelve years-old.
Frontoethmoidal suture is a short cranial suture located in the anterior cranial fossa, between the orbital process of frontal and orbital plate of ethmoid bones. It forms part of the medial wall of the orbit.
The anterior and posterior ethmoidal foramina are seen just superior to it, through w...
The frontolacimal suture is the cranial suture between the frontal and lacrimal bones.
The frontomaxillary suture is the site where nasal process of frontal bone meets the frontal process of maxilla.
The frontonasal suture is the cranial suture between the frontal bone and the two nasal bones. This suture meets the internasal suture at the nasion.
The frontozygomatic suture (or zygomaticofrontal suture) exists between the zygomatic process of the frontal bone and the frontal process of the zygomatic bone.
The geniohyoid muscle is a suprahyoid muscle of the neck that is innervated by the ventral ramus of C1. Geniohyoid draws the hyoid bone up and forward during mastication and assists the opening of the mandible.
origin: inferior mental spine of the mandible also known as the genial tube...