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Score — click each question to reveal the answer
Q1
The skull consists of how many bones in total?
L2 — Skull Notes
L2 — Skull Notes
A. 22
B. 18
C. 20
D. 26
✅ Answer: A — 22 bones
The skull has 22 bones: 8 cranial bones (frontal, 2 parietal, 2 temporal, occipital, sphenoid, ethmoid) and 14 facial bones (2 nasal, 2 maxillae, 2 zygomatic, 2 lacrimal, 2 palatine, 2 inferior nasal conchae, 1 vomer, 1 mandible). All except the mandible are joined by fibrous sutures.
⚠ Trap: 26 is the vertebral column. 8 is only the cranial subset. Know both the total (22) and the cranial/facial split (8 + 14).
Q2
The pterion is the junction of how many skull bones?
L2 — Skull Notes
L2 — Skull Notes
A. 2
B. 4
C. 3
D. 5
✅ Answer: B — 4 bones
The pterion is the H-shaped junction of four skull bones: frontal, parietal, temporal, and sphenoid. Located ~4 cm above the zygomatic arch and ~3.5 cm behind the frontozygomatic suture. It is the thinnest part of the lateral skull wall.
⚠ Trap: Mnemonic FPTS — Frontal, Parietal, Temporal, Sphenoid. All four meet here. Options A and B are common wrong answers if students only recall "temporal and parietal."
Q3
A fracture at the pterion most commonly damages which artery?
L2 — Skull Notes
L2 — Skull Notes
A. Posterior meningeal artery
B. Anterior meningeal artery
C. Middle meningeal artery
D. Middle cerebral artery
✅ Answer: C — Middle meningeal artery
The anterior branch of the middle meningeal artery runs in a groove on the inner surface of the temporal bone directly beneath the pterion. A blow to the temple fractures the thin bone and tears this artery, causing an extradural (epidural) hematoma — biconvex on CT, with a classic lucid interval followed by rapid deterioration.
⚠ Trap: Middle cerebral artery (option D) is a brain artery in the subarachnoid space, not a meningeal vessel. Subdural hematomas arise from bridging veins, not arterial bleeds.
Q4
Which structures pass through the foramen magnum?
L2 — Skull Notes
L2 — Skull Notes
A. CN VII and CN VIII
B. Olfactory nerve filaments
C. CN IX, X, and XI only
D. Medulla oblongata and vertebral arteries
✅ Answer: D — Medulla oblongata and vertebral arteries
The foramen magnum (occipital bone) transmits: medulla oblongata, vertebral arteries, spinal accessory nerves (CN XI spinal roots), anterior and posterior spinal arteries, and meninges. It marks the transition between brainstem and spinal cord.
⚠ Trap: CN VII & VIII → IAM. Olfactory filaments → Cribriform plate. CN IX, X, XI → Jugular foramen. Each foramen has its own nerve set — keep a foramen table memorised.
Q5
The sella turcica is a depression in which bone, and contains what structure?
L2 — Skull Notes
L2 — Skull Notes
A. Sphenoid bone — pituitary gland
B. Occipital bone — cerebellum
C. Temporal bone — petrous apex
D. Ethmoid bone — olfactory bulb
✅ Answer: A — Sphenoid bone — pituitary gland
The sella turcica ("Turkish saddle") is a saddle-shaped depression in the body of the sphenoid bone. Its hypophyseal fossa holds the pituitary gland. Bounded anteriorly by the tuberculum sellae and posteriorly by the dorsum sellae. Pituitary tumours expanding here compress the optic chiasm → bitemporal hemianopia.
⚠ Trap: Ethmoid + olfactory bulbs sits on the cribriform plate — a common confusion. Rule: sella = sphenoid = pituitary.
Q6
The cribriform plate is part of which bone and transmits which nerve?
L2 — Skull Notes
L2 — Skull Notes
A. Sphenoid bone — CN II (optic)
B. Ethmoid bone — CN I (olfactory)
C. Temporal bone — CN VII (facial)
D. Occipital bone — CN XII (hypoglossal)
✅ Answer: B — Ethmoid bone — CN I (olfactory)
The cribriform plate is the perforated horizontal part of the ethmoid bone, forming the floor of the anterior cranial fossa. Its tiny foramina transmit CN I (olfactory nerve) filaments from the nasal mucosa to the olfactory bulbs. Fractures here → CSF rhinorrhea + anosmia.
⚠ Trap: CN II → optic canal (sphenoid). CN VII → IAM then stylomastoid foramen (temporal). CN XII → hypoglossal canal (occipital). Each cranial nerve has one exit point.
Q7
The jugular foramen transmits:
L2 — Skull Notes
L2 — Skull Notes
A. CN VII, VIII and labyrinthine artery
B. CN II and ophthalmic artery
C. CN IX, X, XI and internal jugular vein
D. CN XII alone
✅ Answer: C — CN IX, X, XI and internal jugular vein
The jugular foramen (between temporal and occipital bones) transmits: CN IX (glossopharyngeal), CN X (vagus), CN XI (accessory), and the internal jugular vein — the largest venous outflow from the skull. A lesion here produces Vernet's syndrome.
⚠ Trap: Option A describes the IAM contents. CN XII exits via the hypoglossal canal. CN II exits via the optic canal. Option A is the most common distractor.
Q8
The internal acoustic meatus (IAM) transmits:
L2 — Skull Notes
L2 — Skull Notes
A. CN IX and X
B. CN V2 and V3
C. CN XI and CN XII
D. CN VII (facial) and CN VIII (vestibulocochlear)
✅ Answer: D — CN VII and CN VIII
The IAM is in the petrous temporal bone and transmits CN VII (facial) and CN VIII (vestibulocochlear), plus the labyrinthine artery (branch of AICA). Acoustic neuromas (vestibular schwannomas) arise here → sensorineural hearing loss + tinnitus, eventually facial palsy.
⚠ Trap: CN IX/X → jugular foramen. V2 → foramen rotundum; V3 → foramen ovale. IAM is strictly the CN VII + VIII pair — always tested together.
Q9
The sphenoid bone is called the 'keystone' of the skull because:
L2 — Skull Notes
L2 — Skull Notes
A. It articulates with all other cranial bones
B. It is the largest cranial bone
C. It forms the entire floor of the cranium
D. It contains the most foramina of any skull bone
✅ Answer: A — It articulates with all other cranial bones
The sphenoid is the keystone because its butterfly-shaped body and wings articulate with every other cranial bone (frontal, parietal, temporal, occipital, ethmoid) — like the central wedge stone in an arch. It also houses the sella turcica, optic canals, and sphenoid sinuses.
⚠ Trap: The frontal bone is the largest cranial bone. The sphenoid contributes substantially to the cranial floor but does not form it entirely — temporal and occipital bones also contribute.
Q10
Vernet's syndrome results from a lesion at the:
L2 — Skull Notes
L2 — Skull Notes
A. Foramen magnum
B. Jugular foramen
C. Cribriform plate
D. Internal acoustic meatus
✅ Answer: B — Jugular foramen
Vernet's syndrome (jugular foramen syndrome) — most commonly from glomus jugulare tumours, fractures, or infections — damages CN IX (dysphagia, absent gag), CN X (hoarseness, palatal weakness), and CN XI (weakness of SCM and trapezius). All three deficits together pinpoint the jugular foramen.
⚠ Trap: IAM lesion → CN VII (facial palsy) + CN VIII (hearing loss) — acoustic neuroma. Knowing foramen → syndrome mapping is high-yield for written papers.
Q11
Which condition typically results from a fracture at the pterion?
L2 — Skull Notes
L2 — Skull Notes
A. Subdural hematoma
B. Subarachnoid hemorrhage
C. Extradural (epidural) hematoma
D. Intracerebral hemorrhage
✅ Answer: C — Extradural (epidural) hematoma
Pterion fracture → middle meningeal artery tear → arterial bleeding into the extradural space. CT: biconvex (lens-shaped) hyperdense collection. Classic timeline: blow to temple → brief LOC → lucid interval → rapid neurological deterioration as haematoma expands and herniates the temporal lobe.
⚠ Trap: Subdural = bridging vein rupture (crescent-shaped, often elderly). Subarachnoid = berry aneurysm rupture ("thunderclap headache"). Extradural = arterial, biconvex — know all three radiological appearances.
Q12
The anterior cranial fossa accommodates which part of the brain?
L2 — Skull Notes
L2 — Skull Notes
A. Cerebellum
B. Temporal lobes
C. Pons and medulla
D. Frontal lobes
✅ Answer: D — Frontal lobes
The anterior cranial fossa (frontal bone orbital plates + cribriform plate + lesser wings of sphenoid) is the highest fossa and accommodates the frontal lobes and olfactory bulbs. Fractures here → CSF rhinorrhea (cribriform plate) + anosmia + raccoon eyes.
⚠ Trap: Cerebellum → posterior fossa. Temporal lobes → middle fossa. Pons and medulla → posterior fossa. All three fossa–brain region pairs are a guaranteed exam question.
1Skull (cranium)+
The bony framework of the head, consisting of 22 bones: 8 cranial bones (frontal, 2 parietal, 2 temporal, occipital, sphenoid, ethmoid) and 14 facial bones (2 nasal, 2 maxillae, 2 zygomatic, 2 lacrimal, 2 palatine, 2 inferior nasal conchae, 1 vomer, 1 mandible).
L2 — The Skull and Joints
2Frontal bone+
Forms the forehead, roof of the orbits, and anterior cranial fossa. Contains the frontal sinuses. Articulates with parietal bones at the coronal suture.
L2 — The Skull and Joints
3Parietal bone+
Two bones forming the sides and roof of the cranium. Articulate with each other at the sagittal suture, with the frontal at the coronal suture, and with the occipital at the lambdoid suture.
L2 — The Skull and Joints
4Temporal bone+
A complex bone with squamous, mastoid, petrous, and tympanic parts. Contains the middle and inner ear, carotid canal, jugular foramen, and styloid and mastoid processes.
L2 — The Skull and Joints
5Occipital bone+
Forms the posterior and inferior part of the cranium. Contains the foramen magnum, occipital condyles (articulate with the atlas, C1), and the external occipital protuberance.
L2 — The Skull and Joints
6Sphenoid bone+
The 'keystone' of the cranial floor, uniting all cranial bones. Has a body, greater and lesser wings, pterygoid processes, and multiple foramina (optic foramen, foramen rotundum, foramen ovale, foramen spinosum). Contains the sella turcica and sphenoid sinuses.
L2 — The Skull and Joints
7Ethmoid bone+
A light, spongy bone between the orbits, forming part of the medial orbital wall, nasal septum, anterior cranial fossa floor, and the superior and middle nasal conchae. Contains the ethmoid air cells and the cribriform plate.
L2 — The Skull and Joints
8Mandible+
The largest and strongest facial bone, forming the lower jaw. Consists of a horizontal body and two vertical rami. The body bears the lower teeth; each ramus has a condylar process (for the TMJ) and a coronoid process.
L2 — The Skull and Joints
9Maxilla+
The upper jaw bone, consisting of a body and four processes (frontal, zygomatic, palatine, alveolar). It contains the maxillary sinus (the largest paranasal sinus) and bears the upper teeth.
L2 — The Skull and Joints
10Zygomatic bone+
The cheekbone, articulating with the frontal, sphenoid, temporal, and maxillary bones. Forms the prominence of the cheek and part of the lateral wall and floor of the orbit.
L2 — The Skull and Joints
11Sutures of the skull+
Fibrous joints between skull bones: coronal (frontal/parietal), sagittal (parietal/parietal), lambdoid (parietal/occipital), squamosal (parietal/temporal). Allow slight movement in infancy and fuse by adulthood.
L2 — The Skull and Joints
12Pterion+
The H-shaped junction of frontal, parietal, temporal, and sphenoid bones. It is the thinnest part of the lateral skull (~4 cm above the zygomatic arch) and overlies the anterior branch of the middle meningeal artery. Fractures here cause extradural hematoma.
L2 — The Skull and Joints
13Foramen magnum+
The large opening in the occipital bone transmitting the medulla oblongata, meninges, vertebral arteries, spinal accessory nerves (CN XI spinal roots), and anterior and posterior spinal arteries.
L2 — The Skull and Joints
14Sella turcica+
A saddle-shaped depression in the body of the sphenoid bone containing the hypophyseal fossa (pituitary gland). Bounded anteriorly by the tuberculum sellae and posteriorly by the dorsum sellae.
L2 — The Skull and Joints
15Anterior cranial fossa+
The highest and most anterior cranial fossa, formed by the frontal bone orbital plates, cribriform plate of the ethmoid, and lesser wings of the sphenoid. Accommodates the frontal lobes and olfactory bulbs. Fractures → CSF rhinorrhea and anosmia.
L2 — The Skull and Joints
16Middle cranial fossa+
Butterfly-shaped fossa formed by the greater wings and body of the sphenoid, petrous temporal bones, and parietal bones. Contains the temporal lobes and numerous foramina (optic canal, SOF, foramen rotundum, ovale, spinosum, lacerum).
L2 — The Skull and Joints
17Posterior cranial fossa+
The largest and deepest cranial fossa, formed by the occipital bone, petrous temporal bones, and mastoid angles of the parietal bones. Contains the cerebellum, pons, and medulla oblongata. Houses the foramen magnum, IAM, and jugular foramen.
L2 — The Skull and Joints
18Cribriform plate+
A thin perforated sheet of ethmoid bone in the anterior cranial fossa. Its foramina allow passage of olfactory nerve filaments (CN I) from the nasal mucosa to the olfactory bulb. Fractures cause CSF rhinorrhea and anosmia.
L2 — The Skull and Joints
19Jugular foramen+
Located between the temporal and occipital bones, transmitting the internal jugular vein, glossopharyngeal (CN IX), vagus (CN X), and accessory (CN XI) nerves. Lesions here cause Vernet's syndrome (dysphagia + hoarseness + SCM/trapezius weakness).
L2 — The Skull and Joints
20Internal acoustic meatus (IAM)+
An opening in the petrous temporal bone transmitting the facial (CN VII) and vestibulocochlear (CN VIII) nerves and the labyrinthine artery. Acoustic neuromas (vestibular schwannomas) arise here, causing sensorineural hearing loss, tinnitus, and eventually facial palsy.
L2 — The Skull and Joints
Essay 1
Describe the bones forming the cranial vault and base of the skull. Explain the clinical significance of the pterion and fractures of the anterior cranial fossa.
10 marks
Cranial vault (calvaria)
The dome-shaped roof is formed by the frontal bone (anterior), two parietal bones (superior and lateral), and the squamous part of the occipital bone (posterior), bounded by the coronal, sagittal, and lambdoid sutures.
Three cranial fossae
- Anterior cranial fossa: Frontal bone orbital plates + cribriform plate of ethmoid + lesser wings of sphenoid. Accommodates frontal lobes and olfactory bulbs.
- Middle cranial fossa: Butterfly-shaped; greater wings and body of sphenoid + petrous and squamous temporal + parietal bones. Contains temporal lobes and important foramina.
- Posterior cranial fossa: Occipital bone + petrous temporal + mastoid angles of parietal. Contains cerebellum, pons, medulla.
Clinical significance of the pterion
The pterion is the H-shaped junction of the frontal, parietal, temporal, and sphenoid bones, located approximately 4 cm above the zygomatic arch and 3.5 cm behind the frontozygomatic suture. It is the thinnest part of the lateral skull. The anterior branch of the middle meningeal artery lies directly beneath it. A fracture here tears this artery, causing a life-threatening extradural (epidural) hematoma — biconvex on CT, with a lucid interval then rapid neurological deterioration.
Anterior cranial fossa fractures
- Usually from trauma to the forehead
- Cribriform plate damage → CSF rhinorrhea (CSF leak through nose)
- Olfactory bulb injury → anosmia (loss of smell)
- Raccoon eyes (periorbital bruising) and Battle's sign (bruising behind ear) indicate skull base fracture
Marking guide (10 marks): Calvaria bones and sutures (2) · Three fossa formation and contents (3) · Pterion: location, four bones, artery, extradural hematoma + CT appearance + lucid interval (3) · ACF fracture: CSF rhinorrhea + anosmia + raccoon eyes/Battle's sign (2)
Essay 2
Describe the foramina of the skull base and their transmitted structures. Explain the clinical significance of the foramen magnum and the jugular foramen.
10 marks
Anterior cranial fossa foramina
- Cribriform plate foramina: Olfactory nerve (CN I) filaments
Middle cranial fossa foramina
- Optic canal: Optic nerve (CN II), ophthalmic artery
- Superior orbital fissure: CN III, IV, VI, V1, ophthalmic veins
- Foramen rotundum: Maxillary nerve (V2)
- Foramen ovale: Mandibular nerve (V3), accessory meningeal artery
- Foramen spinosum: Middle meningeal artery and vein, meningeal branch of V3
- Foramen lacerum: Internal carotid artery passes over (not through) it
- Hiatus of facial canal: Greater petrosal nerve
Posterior cranial fossa foramina
- Internal acoustic meatus: CN VII, CN VIII, labyrinthine artery
- Jugular foramen: Internal jugular vein, CN IX, X, XI
- Hypoglossal canal: Hypoglossal nerve (CN XII)
- Foramen magnum: Medulla oblongata, meninges, vertebral arteries, CN XI spinal roots, spinal arteries
Clinical significance — foramen magnum
Tonsillar herniation: Raised intracranial pressure can herniate the cerebellar tonsils through the foramen magnum, compressing the medulla → cardiorespiratory arrest and death. The vertebral arteries entering here are vulnerable in basilar skull fractures.
Clinical significance — jugular foramen
Vernet's syndrome (jugular foramen syndrome): Glomus jugulare tumours, fractures, or infections compress CN IX, X, and XI simultaneously: dysphagia and absent gag reflex (CN IX), hoarseness and palatal weakness (CN X), weakness of sternocleidomastoid and trapezius (CN XI).
Marking guide (10 marks): ACF foramina (1) · MCF foramina with correct nerves/vessels (3) · PCF foramina — IAM, jugular, hypoglossal, foramen magnum (3) · Foramen magnum clinical: tonsillar herniation (1.5) · Jugular foramen clinical: Vernet's syndrome with all three CNs named (1.5)