Anatomy of the Scalp and Skull

Comprehensive vocabulary flashcards covering the anatomical layers, vasculature, nerve supply, clinical correlates, and osteology of the scalp and skull base.

Scalp

The soft tissue covering the cranial vault, extending anteriorly from the supraorbital margin to the external occipital protuberance and superior nuchal line posteriorly, and laterally to the superior temporal line on each side.

Surgical Layers of the Scalp

The first three layers of the scalp—Skin, Connective tissue, and Aponeurotic layer—which are steadfastly bound to each other and function together as the scalp proper.

Epicranial Aponeurosis

The fibrous sheet under tension in the anteroposterior direction that connects the frontal belly and occipital belly of the occipitofrontalis muscle.

Loose Areolar Tissue Layer

The fourth layer of the scalp beneath the aponeurosis that accounts for scalp mobility and contains valveless emissary veins; termed the dangerous area of the scalp because infections can travel into intracranial venous sinuses.

Subgaleal Haemorrhage

An accumulation of blood between the galea aponeurotica and periosteum caused by the rupture of emissary veins during a difficult delivery.

Pericranium

The periosteum of the skull that is loosely attached to the surface of calvarial bones but firmly adherent to suture lines.

Cephalohematoma

A collection of blood between a neonate's pericranium and calvaria caused by rupture of periosteal arteries; it takes the shape of the individual skull bone because periosteal adherence at sutures prevents cross-suture spread.

Caput Succedaneum

Edematous swelling of the scalp in a newborn that occurs superficial to the periosteum and freely crosses cranial suture lines.

Angular Vein

A facial vein formed at the medial angle of the eye by the union of the supratrochlear and supraorbital veins, continuing downward as the facial vein.

Retromandibular Vein

A vein formed inside the parotid gland by the union of the superficial temporal vein and maxillary vein, dividing into anterior and posterior branches.

Orbitomeatal Plane

The standard craniometric reference plane (Frankfort horizontal plane) in which the inferior margin of the orbit and the superior margin of the external acoustic meatus lie in the same horizontal plane.

Calvaria

The upper domelike roof or skullcap of the neurocranium that encloses and protects the brain, formed by flat bones that develop through intramembranous ossification.

Neurocranium

The bony case of the brain and cranial meninges comprising $8$ bones: four single midline bones (frontal, ethmoid, sphenoid, occipital) and two paired lateral bones (parietal, temporal).

Viscerocranium

The facial skeleton comprising $15$ irregular bones: three singular midline bones (mandible, ethmoid, vomer) and six paired bilateral bones (maxilla, inferior nasal concha, zygomatic, palatine, nasal, lacrimal).

Diploë

The central layer of cancellous bone containing red bone marrow and diploic veins located between the inner and outer compact bone tables of the cranial vault.

Emissary Veins

Valveless venous channels passing through emissary foramina that establish communication between extracranial veins of the scalp and intracranial venous sinuses.

Synarthrosis

A type of immovable joint connected mainly by fibrous collagen connective tissue with no joint cavity, characteristic of adult cranial sutures.

Coronal Suture

The cranial suture running in the coronal plane that joins the frontal bone with the two parietal bones.

Sagittal Suture

The cranial suture running in the sagittal plane between the paired parietal bones.

Squamous Suture

The cranial suture joining the parietal bone with the squamous part of the temporal bone.

Lambdoid Suture

The cranial suture joining the paired parietal bones with the occipital bone.

Vertex

The most superior anatomical point of the cranium, located near the midpoint of the sagittal suture.

Metopic Suture

A persistent midline suture between the two frontal bones present in approximately $8\%$ of individuals, which normally fuses by the $5\text{th}$ year of life.

Pterion

An H-shaped craniometric junction of the frontal, parietal, temporal, and greater wing of sphenoid bones; vulnerable to fractures that can rupture the underlying anterior branch of the middle meningeal artery.

Asterion

A craniometric point at the junction of the parietal, occipital, and mastoid parts of the temporal bone.

Nasion

A craniometric landmark located in the middle of the nasofrontal suture at the intersection of the frontal and two nasal bones.

Inion

The most prominent external point of the external occipital protuberance used as a fixed craniometric reference.

Epidural Hematoma

An arterial blood collection between the skull inner table and dura mater—often due to middle meningeal artery rupture at the pterion—appearing on CT as a biconvex/lens-shaped hyperdensity that does not cross suture lines.

Subdural Hematoma

A venous blood collection between the dura and arachnoid mater caused by torn bridging veins, presenting on CT as a crescent-shaped concave hyperdensity that can cross cranial suture lines.

Anterior Fontanelle

The largest, diamond-shaped membranous soft spot located at the junction of coronal and sagittal sutures, which normally closes at approximately $18$ months of age.

Posterior Fontanelle

The triangular membranous soft spot at the junction of sagittal and lambdoid sutures, which normally fuses at approximately $3$ months of age.

Wormian Bones

Small, naturally occurring irregular bones that develop from extra ossification centers within cranial sutures and fontanelles.

Craniosynostosis

A condition characterized by the premature closure of one or more cranial sutures in infants, restricting brain expansion and resulting in abnormal cranial geometry.

Anterior Cranial Fossa

The shallowest and most superior cranial fossa accommodating the frontal lobes of the brain, bounded by the frontal bone, ethmoid bone, and lesser wings/limbus of sphenoid.

Crista Galli

A thick, triangular median bony projection of the ethmoid bone extending superiorly from the cribriform plate to serve as an attachment point for the falx cerebri.

Cribriform Plate

The thinnest, perforated horizontal plate of the ethmoid bone that forms part of the anterior cranial fossa floor and transmits olfactory nerve ($CN\,I$) fibers.

Anosmia

The loss of sense of smell caused by traumatic shearing of olfactory nerve fibers traversing a fractured cribriform plate.

CSF Rhinorrhoea

Drainage of clear cerebrospinal fluid through the nasal cavity resulting from meningeal tears secondary to fractures of the anterior cranial fossa or cribriform plate.

Middle Cranial Fossa

A butterfly-shaped central cranial fossa formed by the body and greater wings of sphenoid and temporal bones, accommodating the pituitary gland and temporal lobes.

Sella Turcica

A saddle-shaped bony depression on the body of the sphenoid bone comprising the tuberculum sellae, hypophyseal fossa (pituitary housing), and dorsum sellae.

Superior Orbital Fissure

An opening between the greater and lesser wings of sphenoid connecting the middle cranial fossa to the orbit, transmitting $CN\,III$, $CN\,IV$, ophthalmic nerve ($CN\,V_1$) branches, $CN\,VI$, and ophthalmic veins.

Superior Orbital Fissure Syndrome

A clinical complex of impaired extraocular and sensory function affecting nerves $CN\,III$, $CN\,IV$, $CN\,V_1$, and $CN\,VI$ due to trauma, tumor, or inflammation at the superior orbital fissure.

Foramen Rotundum

An aperture in the greater wing of sphenoid that opens into the pterygopalatine fossa, transmitting the maxillary nerve ($CN\,V_2$).

Foramen Ovale

An aperture in the greater wing of sphenoid that opens into the infratemporal fossa, transmitting the mandibular nerve ($CN\,V_3$), accessory meningeal artery, lesser petrosal nerve, and emissary vein.

Foramen Spinosum

An aperture in the greater wing of sphenoid transmitting the middle meningeal artery, middle meningeal vein, and meningeal branch of the mandibular nerve ($CN\,V_3$) into the middle cranial fossa.

Foramen Lacerum

An irregular gap at the base of the skull situated between the petrous temporal apex and sphenoid body, filled in life with cartilage and traversed by minor vessels.

Carotid Canal

A canal in the petrous temporal bone traversed by the internal carotid artery and surrounding sympathetic nerve plexus.

Posterior Cranial Fossa

The deepest cranial fossa bounded by petrous temporal ridge, dorsum sellae, and occipital bone, lodging the hindbrain (cerebellum, pons, and medulla oblongata).

Internal Acoustic Meatus

A bony canal in the petrous temporal bone transmitting the facial nerve ($CN\,VII$), vestibulocochlear nerve ($CN\,VIII$), and labyrinthine artery.

Foramen Magnum

The largest opening in the occipital bone connecting the posterior cranial fossa with the vertebral canal, transmitting the medulla oblongata, vertebral arteries, spinal accessory nerve roots, spinal arteries, alar ligaments, tectorial membrane, and meninges.

Jugular Foramen

A large opening between the petrous temporal and occipital bones transmitting the inferior petrosal sinus, sigmoid sinus (forming internal jugular vein), and cranial nerves $CN\,IX$, $CN\,X$, and $CN\,XI$.

Vernet's Syndrome

Jugular foramen syndrome caused by tumor compression of cranial nerves $CN\,IX$, $CN\,X$, and $CN\,XI$, resulting in dysphagia, hoarseness, sensory loss of oropharynx/posterior tongue, and trapezius/sternocleidomastoid weakness.

Cerebellar Tonsillar Herniation

Downward displacement of the cerebellar tonsils through the foramen magnum (coning) caused by raised intracranial pressure, leading to brainstem compression and cardiorespiratory arrest.

Suprameatal Triangle

An anatomical landmark (MacEwen's triangle) posterosuperior to the external acoustic meatus bounded by the supramastoid crest and meatal tangents, forming the lateral wall of the mastoid antrum.

Mandible

The largest, strongest, and only mobile bone of the facial skeleton, comprising a U-shaped horizontal body and two vertical rami.

Maxilla

A paired bone of the viscerocranium that fuses at the midline to form the upper jaw, anterior three-quarters of the hard palate, floor of the orbits, and floor/lateral walls of the nasal cavity.