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Face: Anterior aspect of head; contains facial muscles responsible for expression.
Scalp: Covers lateral, posterior, and superior parts of skull.
Compartments of Neck
Posterior/Vertebral compartment → 7 cervical vertebrae and associated muscles.
Anterior/Visceral compartment → thyroid, parathyroid, thymus, parts of respiratory and digestive tracts.
Two lateral vascular compartments → major arteries, veins, lymphatics, and nodes.
Pharynx: Musculofascial tube divided into naso-, oro-, and laryngopharynx.
Larynx: Between hyoid and trachea; made of cartilages and membranes; functions in phonation and respiration.
Protects brain, endocrine glands, and special sense organs.
Provides passage for food and air.
Enables voice and speech.
Evolutionary adaptations:
Enlarged cranial cavity → accommodates evolved brain.
Retracted mandible, anterior eyes, prominent nose, smaller external ear.
Tongue specialized for articulation; speech as human hallmark.
Frontal region – front of skull.
Parietal region – top of skull.
Occipital region – back of skull.
Temporal region – above ears (hearing & balance center).
Ocular region – around orbit; contains eyeball & accessory structures.
Auricular region – around external ear & meatus.
Nasal region – external nose & cavity (smell).
Oral region – lips, angles of mouth; emotional expression.
Oral cavity – contains tongue (taste & speech).
Parotid region – lateral face, houses parotid gland.
Posterior triangle: Between sternocleidomastoid, trapezius, and clavicle.
Contains subclavian vessels, branches, and brachial plexus roots.
Anterior triangle: Between midline and sternocleidomastoid.
Contains carotid artery, thyroid isthmus, and related structures.
Includes: Skull (cranium + mandible), 7 cervical vertebrae, hyoid, and 6 ear ossicles.
Skull cap (calvaria): Frontal, parietal, squamous temporal, and occipital parts — ossify intramembranously.
Skull base: Ossifies endochondrally (cartilaginous).
Functions:
Lodges brain, meninges, teeth, and sense organs (eye, ear, olfactory, taste).
Brain weight supported by cerebrospinal fluid (CSF).
Definition: Skeleton of head comprising cranium and mandible.
Parts:
Neurocranium (calvaria): Brain box – vault + base.
Viscerocranium: Facial skeleton including mandible.
Neurocranium (8 bones)
Paired: Parietal (2), Temporal (2)
Unpaired: Frontal (1), Occipital (1), Sphenoid (1), Ethmoid (1)
Facial skeleton (14 bones)
Paired: Maxilla, Zygomatic, Nasal, Lacrimal, Palatine, Inferior nasal concha (each 2)
Unpaired: Mandible, Vomer
Ear Ossicles (6): Malleus, Incus, Stapes (each pair).
Joints of Skull
Mostly sutures (fibrous joints).
Some primary cartilaginous joints.
Synovial joints:
Ossicular joints (malleus–incus–stapes).
Temporomandibular joint (mobile).
Types of sutures:
Plane → internasal
Serrate → coronal
Denticulate → lambdoid
Squamous → parietotemporal
Reid’s baseline: From infraorbital margin → center of external acoustic meatus.
Frankfurt’s horizontal plane: From infraorbital margin → upper border of external acoustic meatus.
External views (normae):
Superior → Norma verticalis
Posterior → Norma occipitalis
Anterior → Norma frontalis
Lateral → Norma lateralis
Inferior → Norma basalis
Internal views:
Cranial vault (roof)
Cranial base (anterior, middle, posterior fossae)
Base ossifies in cartilage; vault in membrane.
Diploë (between outer & inner tables) → red marrow for hematopoiesis.
Fontanelles → membranous gaps at parietal angles for growth and parturition.
Pneumatic bones: Frontal, Maxilla – lighten skull, humidify air, resonate voice, may get infected (sinusitis).
Sutures unite most bones.
Emissary veins connect intracranial sinuses with extracranial veins → spread of infection possible.
Petrous temporal bone = densest bone; lodges ear structures.
Skull protects brain, meninges, CSF, sinuses, and special sense organs.
Emissary Veins (examples):
Parietal (to superior sagittal sinus)
Mastoid (to sigmoid sinus)
Condylar (to sigmoid sinus)
Foramen ovale emissary (to cavernous sinus)
Shape: Oval, wider posteriorly.
Bones: Frontal (anterior), Parietals (sides), Occipital (posterior).
Sutures: Coronal, Sagittal, Lambdoid, occasional Metopic.
Key landmarks:
Bregma – coronal + sagittal intersection (anterior fontanelle).
Lambda – sagittal + lambdoid intersection (posterior fontanelle).
Vertex – highest point on sagittal suture.
Parietal tuber – maximal convexity.
Temporal lines – muscular attachments.
Clinical Anatomy:
Fontanelle tension indicates intracranial pressure.
Early closure → microcephaly; delayed closure → hydrocephalus.
Caput succedaneum → birth-related swelling due to venous rupture.
Bones: Parietal (upper), Occipital (below), Mastoid part of temporal (sides).
Sutures: Lambdoid, Occipitomastoid, Parietomastoid, posterior Sagittal.
Features:
External occipital protuberance → palpable midline bump.
Inion – tip of protuberance.
Superior & highest nuchal lines – muscular attachment ridges.
Occipital point – farthest from glabella.
Mastoid foramen – emissary vein & meningeal artery.
Interparietal bone (inca bone) occasionally present.
Attachments:
Trapezius, ligamentum nuchae, sternocleidomastoid, splenius capitis, occipitalis.
Bones: Frontal, Maxilla, Nasal, Zygomatic, Mandible.
Regions:
Frontal region: Superciliary arches, glabella, nasion, frontal tuber.
Orbital openings:
Margins → supraorbital (frontal), infraorbital (maxilla + zygomatic).
Supraorbital notch → supraorbital nerves/vessels.
Nasal aperture: Pear-shaped, bounded by nasal bones & maxillae.
Anterior nasal spine at lower border.
Lower face: Infraorbital foramen (infraorbital nerve), canine & incisive fossae, alveolar process with teeth sockets.
Zygomatic bones: Cheek prominence, zygomaticofacial foramen.
Mandible: Mental protuberance, tubercles, and foramen.
Attachments: Corrugator supercilii, procerus, orbicularis oculi, levator labii muscles, nasalis, zygomaticus, buccinator, etc.
Clinical Anatomy:
Nasal bone → most frequently fractured facial bone.
Parietal eminence & mandible next in frequency.
Bones: Frontal, Parietal, Occipital, Temporal, Sphenoid, Zygomatic, Maxilla, Nasal, Mandible.
Temporal lines: Superior & inferior – temporalis attachment.
Zygomatic arch: Temporal + zygomatic bones; attachment for masseter (below) and temporalis (above).
External acoustic meatus: Bony canal for sound conduction.
Temporal fossa: Above zygoma; temporalis muscle.
Infratemporal fossa: Below arch; pterygoid muscles and maxillary artery.
Pterion: Junction of frontal, parietal, temporal, sphenoid bones — thin area where middle meningeal artery lies.
Clinical Anatomy:
Fracture at pterion may rupture middle meningeal artery, causing extradural hematoma — a neurosurgical emergency.
The base of skull (Norma Basalis) is studied by dividing it into three arbitrary parts:
Anterior, Middle, and Posterior parts.
Formed by hard palate and alveolar arches.
Alveolar Arch
Bears sockets (alveoli) for upper teeth.
Hard Palate
Formation:
Anterior 2/3 → Palatine processes of maxillae.
Posterior 1/3 → Horizontal plates of palatine bones.
Sutures:
Crossed by a cruciform suture (intermaxillary, interpalatine, palatomaxillary).
Features:
Incisive foramen → Median pit with right and left incisive canals.
Greater palatine foramina → Behind palatomaxillary suture, transmits greater palatine nerves and vessels.
Lesser palatine foramina → Behind greater, in pyramidal process of palatine.
Posterior nasal spine → Median posterior projection.
Palatine crest → Curved ridge behind greater palatine foramen.
Extends from posterior border of hard palate to anterior margin of foramen magnum.
Median Area
Posterior border of vomer.
Sphenoid rostrum → Overlaps vomer.
Basilar part of occipital bone anterior to foramen magnum.
Lateral Areas
Greater wing of sphenoid (infratemporal surface).
Pterygoid process → Medial & lateral plates with pterygoid fossa between them.
Foramina:
Foramen ovale → Mandibular nerve.
Foramen spinosum → Middle meningeal artery.
Foramen lacerum → Filled with fibrocartilage, transmits emissary veins and meningeal branch.
Extends behind the foramen magnum.
Key Features:
Foramen magnum → Spinal cord, meninges, vertebral arteries, and spinal roots of accessory nerves.
Occipital condyles → Articulate with atlas.
Condylar canal → Emissary vein connecting sigmoid sinus with suboccipital plexus.
Hypoglossal canal → Hypoglossal nerve.
Jugular foramen → Cranial nerves IX, X, XI, and internal jugular vein.
Styloid process → For muscle and ligament attachment.
Mastoid foramen → Emissary vein + meningeal branch of occipital artery.
Stylomastoid foramen → Facial nerve + stylomastoid artery.
General Features
Lined by endocranium (continuous with pericranium).
Thickness varies: Thinner in temporal and occipital areas, and in females/children.
Bone structure:
Outer table → Thick and resilient.
Inner table → Thin and brittle.
Diploë → Spongy bone with red marrow and diploic veins.
Diploic Veins
Frontal → Supraorbital vein.
Anterior temporal → Sphenoparietal sinus.
Posterior temporal → Transverse sinus.
Occipital → Confluence of sinuses.
Small unnamed → Venous lacunae.
Inner table: Thin and fragile.
Grooves: For meningeal vessels and venous sinuses.
Sagittal sulcus: For superior sagittal sinus.
Granular foveolae: For arachnoid granulations.
Parietal foramina: For emissary veins.
Impressions: From cerebral gyri and meningeal vessels.
Divided into three cranial fossae:
Bones: Frontal, ethmoid, lesser wing of sphenoid.
Holds frontal lobes.
Foramina: Cribriform plate (olfactory nerves), foramen cecum (emissary vein).
Bones: Greater wing & body of sphenoid, squamous & petrous temporal.
Holds temporal lobes.
Important Foramina:
Optic canal – Optic nerve, ophthalmic artery.
Superior orbital fissure – CN III, IV, V1, VI, ophthalmic veins.
Foramen rotundum – Maxillary nerve.
Foramen ovale – Mandibular nerve.
Foramen spinosum – Middle meningeal artery.
Carotid canal – Internal carotid artery.
Deepest; lodges cerebellum, pons, medulla.
Bones: Occipital + petrous temporal.
Foramina:
Foramen magnum – Medulla, vertebral arteries.
Jugular foramen – CN IX, X, XI.
Hypoglossal canal – CN XII.
Internal acoustic meatus – CN VII, VIII.
Fractures at pterion → Middle meningeal artery rupture → Extradural hematoma.
Basilar skull fractures → CSF leakage (nose/ear), cranial nerve palsies.
Depressed fractures → May tear dura and cause infection.
Infection routes: Via emissary veins to venous sinuses.
Foramen magnum herniation: Cerebellar tonsils compress medulla → fatal respiratory arrest.
Cranial fossae lesions:
Anterior → anosmia, rhinorrhea.
Middle → visual/oculomotor deficits.
Posterior → lower cranial nerve palsies.
Lodges: Frontal lobes of the brain.
Attachments: Falx cerebri along crista galli.
Relations: Cribriform plate transmits olfactory nerves; closely related to nasal cavity — prone to CSF rhinorrhea after fracture.
Lodges: Temporal lobes.
Attachments: Tentorium cerebelli along superior border of petrous temporal bone.
Grooves: For cavernous sinus and internal carotid artery.
Relations:
Trigeminal impression on petrous apex → lodges trigeminal ganglion.
Cavernous sinus lateral to sella turcica.
Hypophyseal fossa lodges pituitary gland.
Lodges: Cerebellum, pons, medulla.
Attachments:
Falx cerebelli → internal occipital crest.
Tentorium cerebelli → superior petrosal sinus groove.
Apical ligament, cruciate ligament, and membrana tectoria → lower clivus.
Relations: Jugular tubercle (IX, X, XI cranial nerves), subarcuate fossa (lodges flocculus of cerebellum).
Preventive Factors
Elasticity of skull.
Rounded shape.
Construction from multiple secondary elastic arches (each a bone).
Muscles overlying thin areas act as cushions.
Mechanism
The skull behaves like an elastic sphere filled with semi-fluid brain.
Impact → splitting effect radiating along lines of least resistance.
Sites
Base of skull more fragile → fractures common near foramina.
Vault fractures → typically parietal area.
Inner table more brittle than outer → sometimes fractured alone.
Common Facial Bone Fractures
Nasal bone.
Mandible.
Clinical Notes
Base fracture → CSF otorrhea/rhinorrhea, cranial nerve palsies.
Vault fracture → intracranial hemorrhage risk.
Pyramidal cavity on each side of nasal root — protects and allows movement of eyeball.
Shape: Four-sided pyramid with apex posteriorly at superior orbital fissure and base anteriorly on face.
Roof
Formed by: Orbital plate of frontal bone + lesser wing of sphenoid.
Relations: Separates orbit from anterior cranial fossa; may contain frontal sinus.
Landmarks:
Lacrimal fossa (anterolateral) → lacrimal gland.
Trochlear fossa (anteromedial) → pulley of superior oblique.
Optic canal (posteriorly) → optic nerve + ophthalmic artery.
Lateral Wall
Formed by: Greater wing of sphenoid + frontal process of zygomatic bone.
Strongest wall; separates orbit from middle cranial and temporal fossae.
Features: Superior orbital fissure posteriorly, zygomatic foramen, Whitnall’s tubercle (lateral check ligament).
Floor
Formed by: Maxilla (mainly), zygomatic, and palatine bones.
Inclined upward medially; separates orbit from maxillary sinus.
Contains: Infraorbital groove and canal → infraorbital nerve and vessels.
Medial Wall
Formed by: Ethmoid, lacrimal, body of sphenoid, frontal process of maxilla.
Thinnest wall (“lamina papyracea”); separates orbit from ethmoidal air cells.
Contains: Anterior and posterior ethmoidal canals.
Large cranial vault, small face.
Bones soft and incomplete ossification.
Sutures wide; fontanelles prominent.
Anterior fontanelle (bregma): Diamond-shaped; closes by 18 months.
Posterior fontanelle (lambda): Triangular; closes by 3 months.
Anterolateral (pterion) & posterolateral (asterion): Close by 1 year.
Vault proportionally large (cranial part > facial part).
Head length ≈ 1/4 of total body length at birth.
Thin and pliable; diploë absent.
Separated by membrane at sutures allowing skull molding during birth.
Membranous ossification: Vault bones (frontal, parietal, squamous temporal, occipital).
Cartilaginous ossification: Base bones (sphenoid, ethmoid, petrous temporal).
Rapid in first 2 years (brain growth).
Sutures allow expansion till late adolescence.
Face grows after tooth eruption and sinus development.
Delayed closure → hydrocephalus, rickets.
Early closure → microcephaly.
Moulding during birth allows passage through birth canal.
Depressed fractures in infants → “ping-pong ball” fracture (elastic rebound).
Before puberty: No sexual difference.
After puberty: Distinct male and female characteristics develop.
| Feature | Male Skull | Female Skull |
|---|---|---|
| Weight | Heavier | Lighter |
| Size | Larger | Smaller |
| Cranial capacity | Greater | ~10% less |
| Bone walls | Thicker | Thinner |
| Muscular ridges | Prominent | Less marked |
| Superciliary arches | More prominent | Slight |
| Forehead | Sloping | More vertical |
| Mastoid process | Large, projecting | Small, flat |
| Occipital region | More curved | Less curved |
| Frontal & parietal eminences | Less prominent | More prominent |
| Face | Longer and narrower | Shorter and wider |
| Orbit | Squarer | Rounder |
| Chin | Square | Rounded and smaller |
| Angle of mandible | Everted, 110° | Less everted, ~120°–125° |
Cephalic Index:
Cephalic Index=Maximum BreadthMaximum Length×100\text{Cephalic Index} = \frac{\text{Maximum Breadth}}{\text{Maximum Length}} \times 100Cephalic Index=Maximum LengthMaximum Breadth×100
Length: From glabella → occipital point.
Breadth: Between parietal tubera.
Types:
Dolichocephalic → < 75 (long-headed; primitive races).
Mesaticephalic → 75–80 (average; transitional).
Brachycephalic → > 80 (short-headed; advanced races).
Facial Angle:
Angle between:
Line from nasion → basion (base line).
Line from basion → prosthion (upper incisor point).
Smaller angle → more developed brain and smaller face (seen in evolved humans).
Abnormal Crania:
Oxycephaly (acrocephaly): Tower skull; premature closure of coronal and sphenoid sutures.
Scaphocephaly: Boat-shaped skull; premature closure of sagittal suture.
Largest and strongest facial bone.
Develops from first pharyngeal arch.
Consists of:
Body: Horseshoe-shaped, lodges lower teeth.
Rami (two): Project upward and backward from body.
Surfaces:
Outer surface: Mental protuberance, mental foramen, oblique line.
Inner surface: Mylohyoid line, sublingual and submandibular fossae.
Borders:
Upper border (alveolar) → contains sockets for teeth.
Lower border (base) → gives attachment to platysma.
Landmarks:
Symphysis menti: Midline fusion site.
Mental protuberance: Chin prominence.
Mental foramen: Below 2nd premolar; transmits mental nerve and vessels.
Surfaces:
Lateral: Masseter insertion.
Medial: Pterygoid tuberosity for medial pterygoid attachment.
Borders:
Anterior: Oblique ridge → temporal crest.
Posterior: Thick, rounded, parotid gland behind it.
Superior: Two processes — coronoid (anterior) and condylar (posterior).
Features:
Mandibular notch between the processes.
Lingula: Tongue-shaped projection guarding mandibular foramen.
Coronoid process: Temporalis insertion.
Condylar process: Pterygoid fovea → lateral pterygoid insertion.
Lower border: Platysma origin.
Inner surface: Mylohyoid line → mylohyoid muscle.
Inferior surface: Digastric and geniohyoid origins.
Mandibular foramen: Entry of inferior alveolar nerve and vessels.
Mental foramen: Exit of mental nerve and vessels.
Mandibular canal: Connects these two foramina; transmits same neurovascular bundle.
Primary center: Each half develops from Meckel’s cartilage (membranous ossification).
Secondary centers:
Condylar process – endochondral.
Coronoid process, mental protuberance, alveolar part – membranous.
Ossification starts at 6th week intrauterine life near future mental foramen.
At Birth: Angle ~140°; no teeth; mental foramen near lower border.
Adult: Angle ~110°; eruption of teeth enlarges alveolar part; mental foramen mid-level.
Old Age: Teeth lost; alveolar bone resorbed; angle widens (~140°–160°); chin projects forward.
Laterally: Masseter, buccinator, facial artery and vein.
Medially: Mylohyoid, hyoglossus, lingual nerve, and submandibular gland.
Posteriorly: Parotid gland, facial nerve branches.
Superiorly: Alveolar nerves and vessels.
Fractures:
Common at neck of condyle, angle, and symphysis menti.
Bilateral fracture → airway obstruction due to tongue fall-back.
Inferior alveolar nerve injury → numbness of lower lip and chin.
Tooth extraction → may injure mandibular canal.
Old age bone resorption → ill-fitting dentures due to alveolar loss.
Second largest facial bone (after mandible).
Forms:
Upper jaw.
Parts of face, nose, mouth, orbit, and pterygopalatine & infratemporal fossae.
Each maxilla has a body and four processes: frontal, zygomatic, alveolar, and palatine.
Anterior surface: Medial end has a deep nasal notch.
Posterior surface: Convex; faces infratemporal fossa.
Alveolar border: Downward with tooth sockets; convex outward.
Frontal process: Longest process directed upward.
Medial surface: Has large irregular opening — maxillary hiatus (for maxillary sinus).
Pyramidal shape with 4 surfaces:
Anterior (facial):
Contains infraorbital foramen (infraorbital vessels and nerve).
Canine fossa below foramen, canine eminence above canine socket.
Orbital surface (superior):
Forms large part of floor of orbit.
Infraorbital groove → canal.
Nasal surface (medial):
Forms lateral wall of nose; has maxillary hiatus for sinus opening.
Infratemporal surface (posterior):
Forms anterior wall of infratemporal fossa; marked by maxillary tuberosity with foramina for posterior superior alveolar vessels and nerves.
Frontal Process:
Forms lateral boundary of nose and medial wall of orbit.
Articulates with frontal bone and nasal bone.
Zygomatic Process:
Extends laterally; joins zygomatic bone forming cheek prominence.
Alveolar Process:
Bears 8 sockets for upper teeth; deepest → canine socket.
Buccinator originates posteriorly near first molar.
Palatine Process:
Horizontal plate forming anterior 3/4 of hard palate and floor of nasal cavity.
Medial border raised into nasal crest → receives vomer.
Anterior part forms incisor crest → anterior nasal spine.
Superiorly: Nasal, frontal, lacrimal bones.
Medially: Ethmoid, inferior nasal concha, vomer, palatine, opposite maxilla.
Laterally: Zygomatic bone.
Membranous ossification from three centres:
One for maxilla proper (above canine fossa; appears at 6th week IUL).
Two for premaxilla (os incisivum):
Main centre above incisive fossa (7th week).
Paraseptal/prevomerine centre at ventral nasal septum margin (10th week).
Premaxilla fuses early with alveolar process, but trace may remain till midlife.
At Birth:
Transverse and anteroposterior diameters > vertical.
Frontal process prominent.
Body mainly alveolar; tooth sockets reach orbital floor.
Maxillary sinus shallow furrow.
Adult:
Vertical diameter greatest; sinus enlarged; alveolar process developed.
Old Age:
Alveolar process resorbed; bone height reduced; returns to infantile form.
Two parietal bones form roof and sides of skull vault.
Each bone is quadrilateral with outward convexity.
Outer surface: Convex and smooth.
Inner surface: Concave with meningeal grooves.
Anteroinferior angle: Pointed; has groove for anterior division of middle meningeal artery.
Two surfaces, four borders, four angles.
Surfaces
Outer (convex): Smooth, shows parietal eminence.
Inner (concave): Grooves for meningeal vessels and sagittal sinus impressions.
Borders
Superior (sagittal): Articulates with opposite parietal at sagittal suture.
Inferior (squamosal): Articulates with squamous temporal.
Anterior (frontal): Articulates with frontal bone at coronal suture.
Posterior (occipital): Articulates with occipital bone at lambdoid suture.
Angles
Anterosuperior (frontal) – anterior fontanelle (closes 18 months).
Anteroinferior (sphenoidal) – sphenoidal fontanelle (closes 3 months).
Posterosuperior (occipital) – posterior fontanelle (closes 3 months).
Posteroinferior (mastoid) – mastoid fontanelle (closes ~12 months).
Concave forwards.
Encloses foramen magnum, the largest skull foramen — communication between cranial cavity and vertebral canal.
Each side bears an occipital condyle articulating with the atlas vertebra.
Occipital bone divided into:
Squamous part – above, below, and behind foramen magnum.
Basilar part – in front of foramen magnum (basi-occiput).
Condylar (lateral) part – on each side of foramen magnum.
Squamous Part
Two surfaces (external convex, internal concave).
Four borders (two lambdoid upper, two mastoid lower).
Angles: one superior and two lateral.
Basilar Part
Articulates anteriorly with basisphenoid.
Quadrilateral; has superior and inferior surfaces and four borders.
Condylar Part
Inferior surface: Occipital condyles + hypoglossal canal.
Superior surface: Related to posterior cranial fossa.
Squamous part: Vertical, convex forwards (forehead).
Orbital plates: Thin, horizontal; project backwards forming orbital roof.
Nasal part: Directed forwards and downwards.
Outer surface:
Frontal tuberosity, superciliary arches, glabella.
Frontal sinuses between outer and inner tables.
Metopic suture (may persist).
Supraorbital notch/foramen for supraorbital nerve and vessels.
Zygomatic process, temporal line.
Inner surface: Sagittal sulcus & frontal crest for falx cerebri.
Orbital plates: Separated by ethmoidal notch (occupied by cribriform plate of ethmoid).
Present lacrimal fossa (anterolateral) and trochlear spine (anteromedial).
Nasal part: Between supraorbital margins; articulates with nasal bone, frontal process of maxilla, and lacrimal bone.
Squamous part – plate-like, directed upwards and laterally.
Zygomatic process – strong, projects forwards.
Petrous part – triangular, directed medially.
External acoustic meatus – directed laterally.
Temporal bone has four parts:
Squamous part – outer temporal surface forms part of temporal fossa; has groove for middle temporal artery; supramastoid crest and suprameatal triangle.
Petromastoid part – includes petrous (pyramid-shaped) and mastoid regions.
Houses structures of middle and internal ear.
Superior border grooved by superior petrosal sinus (attachment of tentorium cerebelli).
Posterior border helps form jugular foramen.
Tympanic part – curved plate forming floor and walls of external acoustic meatus; upper and lower margins enclose root of styloid process.
Styloid process – slender projection downward, forward and medially; gives attachment to 3 muscles (styloglossus, stylohyoid, stylopharyngeus) and 2 ligaments (stylohyoid, stylomandibular).
Wedge-shaped (“spheno” = wedge); resembles a bat with outstretched wings.
Parts: Body, two greater wings, two lesser wings, two pterygoid processes.
Six surfaces; contains paired sphenoidal air sinuses.
Superior (cerebral) surface:
Articulates with ethmoid (anteriorly) and basiocciput (posteriorly).
Landmarks: Jugum sphenoidale, Sulcus chiasmaticus, Tuberculum sellae, Sella turcica (with pituitary fossa), Dorsum sellae, and Clivus.
Inferior surface: Rostrum of sphenoid, sphenoidal conchae, vaginal processes of medial pterygoid plate.
Anterior surface: Sphenoidal crest articulates with perpendicular plate of ethmoid to form part of nasal septum; openings of sphenoidal sinuses present.
Project laterally from body; form part of middle cranial fossa, lateral skull wall, and orbit.
Surfaces:
Cerebral (upper) – temporal lobe impressions.
Lateral – forms temporal and infratemporal fossae.
Orbital – forms posterior part of lateral orbital wall.
Openings: Foramen rotundum, foramen ovale, foramen spinosum.
Thin, triangular plates projecting laterally from upper body; form posterior part of orbital roof.
Superior surface: Forms part of anterior cranial fossa.
Inferior surface: Forms roof of orbit.
Posterior edge gives anterior clinoid process for tentorium cerebelli attachment.
Two perpendicular plates descending from junction of body and greater wings.
Each process has medial and lateral pterygoid plates enclosing pterygoid fossa.
Medial plate: Ends in pterygoid hamulus (acts as pulley for tensor veli palatini).
Lateral plate: Provides attachment for medial and lateral pterygoid muscles.
A light, cuboidal bone situated at the anterior base of skull, between the two orbits.
Forms:
Part of medial orbital wall
Part of nasal septum
Lateral walls of nasal cavity
Parts:
Cribriform Plate
Perpendicular Plate
Two Labyrinths
Horizontal perforated lamina in ethmoidal notch of frontal bone.
Foramina transmit olfactory nerve rootlets.
Crista galli – median tooth-like projection for falx cerebri attachment; lateral to it lies the foramen for the anterior ethmoidal nerve.
Thin lamina descending from the underside of cribriform plate.
Forms upper part of nasal septum.
Anteriorly articulates with septal cartilage, posteriorly with vomer.
Paired cubical masses on either side of perpendicular plate, suspended from cribriform plate.
Contain ethmoidal air cells — anterior, middle, and posterior groups.
Surfaces:
Anterior → articulates with frontal process of maxilla.
Posterior → with sphenoidal concha.
Superior → with orbital plate of frontal bone.
Inferior → with nasal surface of maxilla.
Lateral → forms medial orbital wall.
Medial → gives superior & middle nasal conchae, with corresponding meatuses beneath each.
Thin, flat bone forming posteroinferior part of nasal septum.
Features:
Right and left surfaces grooved by nasopalatine nerves.
Superior border → bifid (alae) enclosing groove for rostrum of sphenoid.
Inferior border → articulates with nasal crests of maxillae and palatine bones.
Anterior border → joins perpendicular plate (above) and septal cartilage (below).
Posterior border → free, separating posterior nasal apertures.
Two independent curved laminae, forming lower part of lateral nasal wall.
Surfaces:
Medial convex → vascular grooves.
Lateral concave → forms medial wall of inferior meatus.
Borders:
Superior → articulates with lacrimal, maxilla, ethmoid, palatine.
Inferior → free and spongy.
Ends: Posterior sharper than anterior.
Two small quadrilateral bones forming cheek prominence.
Contribute to floor and lateral wall of orbit and walls of temporal and infraorbital fossae.
Surfaces:
Lateral – has zygomaticofacial foramen.
Temporal – concave, with zygomaticotemporal foramen.
Orbital – smooth, may have zygomatico-orbital foramen.
Borders: Orbital, maxillary, temporal, posteroinferior, posteromedial.
Processes:
Frontal process (upward).
Temporal process (backward; forms zygomatic arch with temporal bone).
Two small oblong bones forming bridge of nose.
Surfaces:
Outer: Convex.
Inner: Concave; vertical groove for anterior ethmoidal nerve.
Borders:
Superior: Articulates with frontal bone.
Inferior: With lateral nasal cartilage.
Medial: With opposite nasal bone.
Lateral: With frontal process of maxilla.
Smallest and most delicate skull bones; form anterior part of medial orbital wall.
Surfaces:
Lateral (orbital): Divided by posterior lacrimal crest → anterior lacrimal fossa (for lacrimal sac).
Medial (nasal): Forms part of middle meatus of nose.
Borders:
Anterior: With frontal process of maxilla.
Posterior: With orbital plate of ethmoid.
Superior: With frontal bone.
Inferior: With orbital surface of maxilla.
Two L-shaped bones forming posterior part of nasal cavity.
Contribute to lateral nasal wall, roof of mouth, floor of orbit, and pterygopalatine fossa.
Parts:
Horizontal plate – posterior ¼ of hard palate; pierced by greater palatine foramen.
Perpendicular plate – forms part of nasal wall.
Processes:
Pyramidal – downward; has lesser palatine foramina.
Orbital – upward; forms posterior orbital floor.
Sphenoidal – upward/medial; articulates with medial pterygoid plate.
U-shaped bone in anterior midline of neck between mandible and thyroid cartilage.
Level: Opposite C3 vertebra.
Suspended by muscles and ligaments.
Function: Provides attachment for tongue, floor of mouth, pharynx, and larynx muscles.
Parts:
Body – central, convex anteriorly, concave posteriorly.
Greater Cornua – long posterior projections ending in tubercles.
Lesser Cornua – small conical eminences at junction of body and greater horns.
Above (Suprahyoid): Geniohyoid, Mylohyoid, Stylohyoid, Digastric.
Below (Infrahyoid): Sternohyoid, Omohyoid, Thyrohyoid.
Posteriorly: Middle pharyngeal constrictor.
Ligaments: Stylohyoid ligament (from styloid process to lesser cornu).
Derived from 2nd (Reichert’s cartilage) and 3rd branchial arches.
Ossification centers appear in body and cornua; fusion complete in adulthood.
Fracture of hyoid → common in strangulation.
Displacement → impairs speech and swallowing.
Infections → may spread through fascial spaces connected to its muscle attachments.
Total: 7 cervical vertebrae.
Typical: 3rd to 6th.
Atypical: 1st (atlas), 2nd (axis), and 7th (vertebra prominens).
Characteristic feature: Presence of foramina transversaria in transverse processes — transmit vertebral artery, veins, and sympathetic nerve.
Small, broader side-to-side than anteroposteriorly.
Superior surface: Concave transversely, with raised uncinate processes.
Inferior surface: Saddle-shaped — convex transversely, concave anteroposteriorly.
Anterior border projects downward and may hide the disc.
Large and triangular, accommodating cervical enlargement of spinal cord.
Pedicles: Directed backward and laterally; notches equal in size.
Laminae: Long and narrow; thinner above than below.
Articular processes:
Superior → directed upward and backward.
Inferior → directed downward and forward.
Together form articular pillars.
Spine: Short and bifid; notch filled by ligamentum nuchae.
Each has anterior and posterior roots ending in tubercles, joined by costotransverse bar.
Anterior root: Represents costal element; gives origin to scalenus anterior, longus capitis, and longus colli.
Posterior tubercle: Gives origin to scalenus medius, scalenus posterior, and levator scapulae; insertion to splenius cervicis and longissimus cervicis.
Foramen transversarium: Transmits vertebral artery, veins, and sympathetic branch.
C6 anterior tubercle → carotid tubercle, landmark for compressing common carotid artery.
Anterior longitudinal ligament: Upper/lower margins of body (front).
Posterior longitudinal ligament: Back of body.
Basivertebral veins: Perforate posterior surface.
Muscles: Deep neck muscles attach to spinous processes.
Primary centers (3):
One for centrum (appears at 3–4 months IUL).
One for each neural arch (9–10 weeks IUL).
Fusion:
Neural arches fuse posteriorly by 1 year.
Neurocentral synchondrosis fuses by 3 years.
Secondary centers (6):
2 annular epiphyses (upper and lower body surfaces).
2 tips of transverse processes.
2 tips of bifid spine.
Appear at puberty; fuse by 25 years.
Named after Titan Atlas, who supported the heavens.
Ring-shaped, with no body and no spine.
Consists of:
Anterior arch
Posterior arch
Two lateral masses
Two transverse processes
Anterior Arch:
Has anterior tubercle (for longus colli insertion).
Posterior surface bears facet for dens of axis.
Posterior Arch:
Forms two-fifths of ring.
Has posterior tubercle instead of spine.
Groove on superior surface behind lateral mass → vertebral artery and first cervical nerve.
Lateral Masses:
Superior articular facet: Concave, directed upward and medially; articulates with occipital condyles → atlanto-occipital joint.
Inferior articular facet: Circular, flat, directed downward and medially; articulates with axis → atlantoaxial joint.
Transverse processes: Large, perforated by foramen transversarium.
Primary centers:
One for each neural arch (7th week IUL).
One for anterior arch (appears 1st year postnatal).
Fusion:
Arches fuse posteriorly by 3–4 years.
Anterior arch unites with lateral masses by 6 years.
Sometimes body of atlas fuses with dens of axis.
Also called epistropheus.
Most distinctive feature: Odontoid process (dens) — represents body of atlas fused to axis.
Body: Small; bears dens projecting upward.
Dens: Conical; has anterior facet for atlas; posterior groove for transverse ligament.
Vertebral Foramen: Large and triangular.
Laminae: Thick and strong; spine large and bifid.
Superior articular facets: Face upward and laterally.
Inferior facets: Face downward and forward — typical cervical orientation.
Transverse processes: Small with foramina transversaria; no anterior tubercles.
Pivot joint between dens and atlas → rotation of head.
Forms atlantoaxial joint (median and lateral components).
Largest cervical vertebra with long, thick, non-bifid spine—prominent and palpable at the root of the neck.
Transverse processes: Large; posterior root larger than anterior; anterior tubercle absent.
Foramen transversarium: Small or double, often does not transmit the vertebral artery, only an accessory vein.
Spine tip: Ligamentum nuchae, trapezius, rhomboid minor, serratus posterior superior, splenius capitis, semispinalis thoracis, spinalis cervicis, interspinales, multifidus.
Transverse process:
Posterior tubercle → suprapleural membrane.
Lower border → levator costarum.
Note: Sometimes, the anterior root of the transverse process remains separate, forming a cervical rib of variable size.
Similar to typical cervical vertebrae.
Additionally, separate centers for each costal process appear at the 6th month of intrauterine life and fuse with the body and transverse process by 5–6 years
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.Cervical rib arises from the C7 vertebra and attaches to the first rib near scalenus anterior insertion.
May compress the brachial plexus and subclavian artery → Tingling pain along medial forearm and hand, weakness/paralysis of palm muscles.
Osteophytes at cervical joints (Luschka’s joints) → press cervical spinal nerves → pain, numbness, vertigo (vertebrobasilar insufficiency).
Prolapsed cervical disc common near C6–C7 → pain in lateral forearm, hand, and thenar wasting.
Hangman’s fracture – pedicle fracture of axis; spinal canal widens without cord injury.
Occipitalization of atlas → fusion with occipital bone; may compress spinal cord.
Judicial hanging → odontoid process fractures, injuring medulla and causing death
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.Intramembranous ossification:
Quicker process; occurs directly in vascular mesenchyme.
Bones forming the calvaria (skull cap) — frontal, parietal, squamous temporal, and upper occipital — ossify in membrane.
Functionally designed to protect the brain, allowing rapid growth and flexibility at sutures and fontanelles
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.Derived from mesenchyme around the developing brain.
Sources of mesenchyme:
Neural crest cells → roof and sides of cranial vault.
Para-axial mesoderm → small part of occipital region.
Ossification type: Membranous ossification.
Frontal Bone:
Ossifies in membrane.
Two centers (8th week) near frontal eminences; separated at birth by a suture that usually fuses early.
Metopic suture may persist in 3–8% adults.
Parietal Bone:
Two centers (7th week) near parietal eminence; fuse soon.
Occipital Bone:
Ossifies partly in membrane, partly in cartilage.
Above highest nuchal line → membranous; below → cartilaginous.
Interparietal bone may persist if separation occurs.
Temporal Bone:
Squamous and tympanic parts → membrane; petromastoid and styloid → cartilage.
Styloid process from 2nd branchial arch; tympanohyal before birth, stylohyal after.
Sphenoid Bone:
Presphenoidal part: Anterior body + lesser wings (6 centers).
Postsphenoidal part: Posterior body + greater wings + pterygoid processes (8 centers)
The foramina of the skull transmit cranial nerves, arteries, veins, and emissary veins. They are grouped according to the cranial fossae in which they are located.
| Foramen / Aperture | Transmits / Contents |
|---|---|
| Foramen caecum | Emissary vein to superior sagittal sinus from upper part of nose |
| Cribriform plate of ethmoid | Olfactory nerve rootlets |
| Anterior ethmoidal foramen | Anterior ethmoidal nerve and vessels |
| Posterior ethmoidal foramen | Posterior ethmoidal vessels |
| Groove for superior sagittal sinus | Superior sagittal sinus |
| Foramen / Aperture | Contents |
|---|---|
| Optic canal | Optic nerve and ophthalmic artery |
| Superior orbital fissure | Oculomotor (III), Trochlear (IV), Ophthalmic (V₁), Abducent (VI) nerves, Ophthalmic veins, Sympathetic fibers |
| Foramen rotundum | Maxillary nerve (V₂) |
| Foramen ovale | Mandibular nerve (V₃), accessory meningeal artery, emissary vein |
| Foramen spinosum | Middle meningeal artery and vein, meningeal branch of V₃ |
| Foramen lacerum | Filled with fibrocartilage; transmits emissary veins and meningeal branch from ascending pharyngeal artery |
| Carotid canal | Internal carotid artery and sympathetic plexus |
| Hiatus for greater petrosal nerve | Greater petrosal nerve |
| Hiatus for lesser petrosal nerve | Lesser petrosal nerve |
| Foramen / Aperture | Contents |
|---|---|
| Internal acoustic meatus | Facial (VII) and Vestibulocochlear (VIII) nerves, labyrinthine vessels |
| Jugular foramen | Glossopharyngeal (IX), Vagus (X), Accessory (XI) nerves, internal jugular vein, inferior petrosal and sigmoid sinuses |
| Hypoglossal canal | Hypoglossal nerve (XII) |
| Foramen magnum | Medulla oblongata, meninges, vertebral arteries, spinal roots of accessory nerve, tectorial membrane, apical ligament of dens |
| Condylar canal | Emissary vein connecting sigmoid sinus with suboccipital plexus |
| Mastoid foramen | Emissary vein to sigmoid sinus, meningeal branch of occipital artery |
| Foramen / Aperture | Contents |
|---|---|
| Stylomastoid foramen | Facial nerve (VII), stylomastoid artery |
| Infraorbital foramen (maxilla) | Infraorbital nerve and vessels |
| Mental foramen (mandible) | Mental nerve and vessels |
| Incisive foramen (maxilla) | Nasopalatine nerves |
| Greater palatine foramen | Greater palatine nerve and vessels |
| Lesser palatine foramina | Lesser palatine nerves and vessels |
| Zygomaticofacial foramen | Zygomaticofacial nerve |
| Zygomaticotemporal foramen | Zygomaticotemporal nerve |
| Parietal foramen | Emissary vein to superior sagittal sinus |
| Mastoid foramen | Emissary vein and meningeal branch of occipital artery |
Emissary veins serve as potential pathways for infection from scalp to intracranial sinuses.
Jugular foramen syndrome (Vernet’s) → paralysis of IX, X, XI nerves.
Fracture involving foramen lacerum or carotid canal → injury to internal carotid artery or sympathetic plexus → Horner’s syndrome.
Superior orbital fissure syndrome → ophthalmoplegia with sensory loss in forehead.
Mnemonic — “Some Friendly Zebras Play Easy Music”
S → Sphenoid
F → Frontal
Z → Zygomatic
P → Palatine
E → Ethmoid
M → Maxilla
Mnemonic — “ROSpy’s Hole”
R → Foramen Rotundum
O → Foramen Ovale
S → Foramen Spinosum
p → (sometimes) Petrosal canal
Mnemonic — “FEMS”
F → Frontal
E → Ethmoid
M → Maxilla
S → Sphenoid
Mnemonic — “Save Boys Carefully”
S → Squamous part
B → Basilar part
C → Condylar parts (lateral)
Mnemonic — “JIM FM”
J → Jugular foramen
I → Internal acoustic meatus
M → Mastoid foramen
F → Foramen magnum
M → Hypoglossal canal (Medial to jugular)
Mnemonic — “Live Free And Happy”
L → Lacrimal nerve
F → Frontal nerve
A → Abducent nerve
H → branches of Oculomotor and Trochlear nerves
The skull is composed of 22 bones — 8 cranial and 14 facial.
Cranial bones: Frontal, Parietal (2), Temporal (2), Occipital, Sphenoid, Ethmoid.
Facial bones: Maxilla (2), Zygomatic (2), Nasal (2), Lacrimal (2), Palatine (2), Inferior nasal conchae (2), Vomer, Mandible.
The largest paranasal sinus → Maxillary sinus.
The strongest facial bone → Mandible.
Frontal air sinuses open into the middle meatus of nose.
Vomer forms the lower and posterior part of nasal septum.
Hyoid bone lies opposite C3 vertebra and does not articulate with any other bone.
Styloid process arises from the petrous part of the temporal bone.
Atlas (C1) has no body or spine, and Axis (C2) bears the dens for rotation.
C7 spine is the most palpable in the neck — the vertebra prominens.
Emissary veins form dangerous routes for intracranial infection spread.
Foramen magnum transmits the medulla, meninges, vertebral arteries, and spinal roots of accessory nerves.
Fontanelles:
Anterior → closes by 18 months.
Posterior → closes by 3 months.
Sutures of skull: Coronal, Sagittal, Lambdoid, Squamous.
Cranial capacity:
Male ~1500 cc
Female ~1300 cc
Cephalic index: 75–80 = mesaticephalic (normal range).
Occipital bone articulates with atlas at atlanto-occipital joint allowing nodding movement.
Parietal bones form the major part of cranial vault.
Ethmoid bone contains olfactory foramina for smell transmission.
Temporal bone houses organ of hearing and balance.
Cause:
A blunt force directed to the eyeball (e.g., by a ball or fist).
Anatomy involved:
The floor of orbit (formed by the maxilla) is the weakest part and gives way.
Result:
Displacement of orbital fat and inferior rectus into the maxillary sinus.
Diplopia (double vision) due to entrapment of inferior rectus.
Infraorbital nerve injury → anesthesia of cheek and upper lip.
Radiograph: Fluid level in maxillary sinus.
Cause:
High-velocity head trauma.
Anatomy involved:
Fracture lines run through petrous temporal bone and sphenoid.
Clinical features:
Otorrhea (CSF from ear) if tympanic membrane ruptures.
Battle’s sign: Bruising over mastoid due to blood extravasation.
Facial paralysis if facial canal injured.
Hearing loss due to involvement of inner ear structures.
Diagnosis: CSF–blood mixture “halo sign” on gauze.
Definition:
Fracture at the junction of frontal, parietal, sphenoid, and temporal bones.
Importance:
Lies over the anterior division of middle meningeal artery.
Consequence:
Tear of the artery → epidural hematoma.
Rapid intracranial pressure rise → brain compression, herniation, death if untreated.
Treatment:
Emergency burr hole (above zygoma, posterior to pterion) for clot evacuation.
Common sites:
Neck of condyle.
Angle of mandible.
Symphysis menti.
Clinical features:
Malocclusion of teeth.
Pain and crepitus on movement.
Bilateral fracture → tongue falls backward, causing airway obstruction.
Treatment: Intermaxillary fixation or surgical plating.
Clinical features:
CSF rhinorrhea (clear nasal discharge).
Panda eyes / raccoon eyes due to periorbital ecchymosis.
Anosmia due to olfactory nerve injury.
Structures involved: Cribriform plate of ethmoid, frontal bone, nasal roof.
Anatomy:
Cervical rib arises from the 7th cervical vertebra.
Structures compressed:
Lower trunk of brachial plexus.
Subclavian artery.
Symptoms:
Tingling, pain, numbness along medial forearm.
Weakness of intrinsic hand muscles.
Occasionally cold, pale upper limb (arterial compression).
Treatment: Surgical removal of cervical rib if severe.
Definition:
Fusion of the atlas (C1) with the occipital bone.
Effects:
Limitation of head movements.
Compression of spinal cord or vertebral artery → neurological symptoms.
Definition:
Premature fusion of cranial sutures.
Types:
Scaphocephaly: Early closure of sagittal suture → long, narrow skull.
Oxycephaly: Closure of coronal and sphenoid sutures → high tower skull.
Effect: Abnormal skull shape, increased intracranial pressure.
Cause: Manual strangulation or hanging.
Clinical Significance:
Fracture indicates homicidal strangulation (forensic importance).
Leads to pain, dysphagia, and speech difficulty.
Mechanism: Hyperextension of head (judicial hanging or road accident).
Anatomy: Bilateral fracture of pars interarticularis of C2.
Effect:
Spinal canal widens; cord usually spared.
May cause death if medulla affected.
The skull is formed by 22 bones.
Cranial bones: 8
Facial bones: 14
Unpaired cranial bones: Frontal, Occipital, Sphenoid, Ethmoid.
Unpaired facial bones: Vomer, Mandible.
Frontal, Ethmoid, Maxilla, Zygomatic, Sphenoid, Lacrimal, Palatine.
Frontal sinus → Middle meatus of nose.
Ethmoidal sinuses:
Anterior → Middle meatus.
Middle → Ethmoidal bulla.
Posterior → Superior meatus.
Sphenoidal sinus → Sphenoethmoidal recess.
Maxillary sinus → Middle meatus (via semilunar hiatus).
Four parts around foramen magnum:
Squamous (behind)
Basilar (in front)
Two condylar parts (lateral)
Pterion is the H-shaped junction of frontal, parietal, sphenoid (greater wing), and temporal bones.
It overlies the anterior branch of the middle meningeal artery.
Fracture causes epidural hemorrhage → neurosurgical emergency.
Frontal, Ethmoid, Maxilla, Sphenoid.
Fontanelles are membranous gaps between developing cranial bones in infants.
Anterior fontanelle → closes by 18 months.
Posterior fontanelle → closes by 3 months.
Anterolateral (sphenoidal) → closes by 3 months.
Posterolateral (mastoid) → closes by 1 year.
The seventh cervical vertebra (C7), because of its long, non-bifid, palpable spine.
Upward projection from body of the axis (C2).
Represents the body of atlas (C1) that has fused with the axis.
Acts as a pivot for rotation of the head.
Lies opposite C3 vertebra.
Suspended by muscles; does not articulate with any other bone.
Supports tongue, floor of mouth, and larynx.
Fracture → sign of strangulation in forensic medicine.
Connect extracranial and intracranial venous systems.
Serve as routes of infection spread from scalp → dural venous sinuses.
Coronal suture – between frontal and parietals.
Sagittal suture – between two parietals.
Lambdoid suture – between parietal and occipital.
Squamous suture – between parietal and temporal bones.
Largest paranasal sinus, prone to infection due to poor drainage (opening high on medial wall).
In maxillary sinusitis, pain referred to upper molar teeth because of common innervation (infraorbital nerve).
Presence of foramen transversarium in each transverse process (for vertebral vessels).
Bifid spinous process (except C1 & C7).
Triangular vertebral foramen.
Premature closure of cranial sutures → abnormal skull shape.
Scaphocephaly: Sagittal suture closes early.
Oxycephaly: Coronal suture closes early.
Medulla oblongata, meninges, vertebral arteries, spinal roots of accessory nerve, tectorial membrane, apical ligament of dens.
Male: Heavier, larger, more muscular markings, sloping forehead, square chin.
Female: Lighter, smaller, rounded chin, vertical forehead, prominent frontal and parietal eminences.
Increase surface area of nasal cavity → warm, moisten, and filter air.
Create turbulence to improve olfaction and air conditioning.
Acts as a pulley for tensor veli palatini muscle during swallowing and speech.
1. The total number of bones forming the skull is:
a) 20
b) 21
✅ c) 22
d) 24
2. Which of the following bones is unpaired?
a) Parietal
b) Temporal
✅ c) Frontal
d) Nasal
3. The pterion is the junction of all the following bones, except:
a) Frontal
b) Parietal
✅ c) Occipital
d) Sphenoid
4. Which of the following structures passes through the foramen rotundum?
a) Ophthalmic nerve
✅ b) Maxillary nerve
c) Mandibular nerve
d) Middle meningeal artery
5. The foramen spinosum transmits:
✅ a) Middle meningeal artery
b) Mandibular nerve
c) Facial nerve
d) Internal carotid artery
6. The dens (odontoid process) represents:
✅ a) Body of atlas
b) Body of axis
c) Neural arch of atlas
d) Neural arch of axis
7. The hyoid bone is located opposite the level of:
a) C2 vertebra
✅ b) C3 vertebra
c) C4 vertebra
d) C5 vertebra
8. The largest paranasal sinus is:
a) Frontal
b) Sphenoidal
✅ c) Maxillary
d) Ethmoidal
9. The bone forming the posterior ¼ of the hard palate is:
a) Maxilla
✅ b) Palatine bone
c) Vomer
d) Sphenoid
10. The foramen magnum transmits all, except:
a) Vertebral arteries
b) Spinal roots of accessory nerve
✅ c) Internal carotid artery
d) Medulla oblongata
11. The characteristic feature of cervical vertebrae is the presence of:
✅ a) Foramen transversarium
b) Large body
c) Long spinous process
d) Costal facets
12. The middle meningeal artery is a branch of:
✅ a) Maxillary artery
b) Internal carotid artery
c) Ascending pharyngeal artery
d) Occipital artery
13. The bone forming the upper part of nasal septum is:
a) Vomer
✅ b) Perpendicular plate of ethmoid
c) Sphenoid
d) Maxilla
14. The nerve passing through the cribriform plate of ethmoid bone is:
✅ a) Olfactory nerve
b) Optic nerve
c) Oculomotor nerve
d) Trochlear nerve
15. The external acoustic meatus is present in the:
✅ a) Temporal bone
b) Sphenoid bone
c) Parietal bone
d) Frontal bone
16. The parietal bones articulate with each other at the:
✅ a) Sagittal suture
b) Coronal suture
c) Lambdoid suture
d) Squamous suture
17. The weakest part of orbit is its:
✅ a) Floor (maxillary part)
b) Roof
c) Lateral wall
d) Medial wall
18. The “dangerous area” for epidural hemorrhage in skull fracture is:
✅ a) Pterion region
b) Mastoid region
c) Occipital protuberance
d) Temporal fossa
19. The anterior fontanelle closes by:
a) 3 months
b) 6 months
✅ c) 18 months
d) 2 years
20. The hyoid bone gives attachment to all, except:
✅ a) Sternothyroid
b) Mylohyoid
c) Stylohyoid
d) Geniohyoid
21. The bone forming posterior nasal spine is:
✅ a) Palatine bone
b) Vomer
c) Maxilla
d) Nasal bone
22. The inferior nasal concha is:
✅ a) A separate bone
b) Part of ethmoid bone
c) Part of maxilla
d) Part of sphenoid bone
23. The skull bone containing internal ear is:
✅ a) Temporal bone
b) Sphenoid bone
c) Parietal bone
d) Occipital bone
24. The foramen lacerum transmits:
✅ a) Emissary vein and meningeal branch of ascending pharyngeal artery
b) Internal carotid artery
c) Facial nerve
d) Maxillary nerve
25. The ossification of cranial bones is mainly:
✅ a) Membranous
b) Endochondral
c) Mixed
d) None of the above
26. The vertebra without a body and spine is:
✅ a) Atlas (C1)
b) Axis (C2)
c) C7
d) C5
27. The nerve injured in fracture at pterion is branch of:
✅ a) Maxillary artery (middle meningeal artery injury)
b) Facial artery
c) Occipital artery
d) Superficial temporal artery
28. The cranial capacity is greater in:
✅ a) Males
b) Females
c) Children
d) Elderly
29. The bone articulating with all other cranial bones is:
✅ a) Sphenoid
b) Ethmoid
c) Frontal
d) Occipital
30. The function of nasal conchae is to:
✅ a) Increase surface area and warm inspired air
b) Allow smell
c) Filter air only
d) Act as resonators
Cranial part (neurocranium) – encloses the brain.
Facial part (viscerocranium) – forms the skeleton of the face.
Cranial cavity
Orbital cavities (2)
Nasal cavity
Oral cavity
Ear cavities (2)
Frontal bone, Ethmoid bone, and Lesser wings of sphenoid.
Foramen rotundum, Foramen ovale, and Foramen spinosum.
Horizontal plate of palatine bone.
Perpendicular plate of ethmoid bone.
Floor of orbit (formed by maxilla) → may fracture in blow-out injuries.
Zygomatic bone.
Vomer, Perpendicular plate of ethmoid, and Septal cartilage.
Maxilla, Ethmoid, Palatine, Lacrimal, and Inferior nasal concha.
Foramen transversarium, bifid spine, and triangular vertebral foramen.
Has no body or spine.
Has anterior and posterior arches.
Bears large lateral masses for occipital condyles.
Presence of odontoid process (dens) projecting upward from the body.
It has a long, thick, non-bifid spine that is easily palpable at the root of the neck.
It allows passage of medulla oblongata, meninges, vertebral arteries, and spinal roots of accessory nerve (XI).
To increase surface area of nasal mucosa for warming, humidifying, and filtering inspired air.
Opposite the C3 vertebra.
Membranous ossification.
Endochondral ossification.
Frontal, Ethmoidal, Maxillary, Sphenoidal – lighten the skull, warm inspired air, and add resonance to voice.
Membranous gaps at junctions of developing cranial bones in infants that allow skull growth.
Lies over the anterior branch of middle meningeal artery → fracture here causes epidural hematoma.
Maxilla.
Supraorbital, Infraorbital, and Mental foramina (transmit nerves and vessels of same name).
Palatine processes of maxillae (anterior ¾) and horizontal plates of palatine bones (posterior ¼).
Malleus, Incus, and Stapes – transmit sound vibrations to the inner ear.
Air-filled spaces in the mastoid part of temporal bone that communicate with middle ear and help in pressure regulation.
May cause CSF rhinorrhea or otorrhea, facial paralysis, or hearing loss, depending on the site.
Petrous part of the temporal bone.
Male: Heavy, large, muscular ridges prominent.
Female: Light, small, rounded features, smoother surface.
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