Cranial Cavity
An infection begins in the loose areolar connective tissue layer of the scalp and later presents as meningitis. Which anatomical feature of this layer explains how the infection was able to spread intracranially?
A. This layer contains the middle meningeal artery, which carries the infection directly into the epidural space
B. This layer contains emissary veins, which are valveless and allow bidirectional flow between extracranial and intracranial venous systems
C. This layer is directly continuous with the subarachnoid space, with no intervening mem-brane
D. This layer contains lymphatic channels that drain directly into the cavernous sinus
E. This layer is the only scalp layer that lacks a blood supply, allowing pathogens to spread unimpeded
B. Correct. The loose areolar connective tissue layer is the scalp’s “danger area” because its emissary veins are valveless, permitting bidirectional flow that lets a superficial infection travel intracranially, potentially causing meningitis.
A 34-year-old man sustains a stab wound just superior to the clavicle. On exploration, a surgeon identifies a nerve running directly over the anterior scalene muscle before it continues inferiorly into the thorax. Injury to this nerve would most directly impair which of the following?
A. Sensation over the skin of the anterior neck
B. Abduction of the vocal folds
C. Tensing of the vocal folds
D. Elevation of the first rib
E. Contraction of the diaphragm
E. The nerve running over the anterior scalene muscle before descending into the thorax is the phrenic nerve (C3–C5), which supplies the diaphragm — its injury impairs diaphragmatic contraction.
The arytenoid and cricoid cartilages of the larynx, along with their associated connective tissue, are derived from which source of head mesenchyme?
A. Lateral plate mesoderm
B. Paraxial mesoderm
C. Neural crest cells
D. Intraembryonic endoderm
E. Intermediate mesoderm
B — Paraxial mesoderm (somites and somitomeres) forms the membranous and cartilaginous components of the skull, the dermis and connective tissue of the dorsal head, and the meninges caudal to the prosencephalon — exactly the structures described.
A 24-year-old is involved in a motor vehicle collision. On an isolated cervical vertebra recovered for anatomic study, you note a relatively large triangular vertebral foramen, foramina within the transverse processes, and a spinous process whose tip divides into two. Which of the following best describes this vertebra?
A. A typical cervical vertebra (C3–C6)
B. C1 (Atlas)
C. C2 (Axis)
D. C7
E. A typical thoracic vertebra
A — A relatively large triangular vertebral foramen, transverse foramina, and a bifid spinous process are the defining distinguishing features of a typical cervical vertebra (C3–C6).
Which of the following best describes the key mechanical difference between a conventional X-ray unit and a CT scanner?
A. A CT scanner uses a motorized X-ray source that rotates around the patient, with digital detectors positioned directly opposite the source, while a conventional X-ray uses a fixed tube sending X-rays in only one direction
B. A CT scanner uses a single fixed X-ray tube, while a conventional X-ray unit rotates around the patient
C. A CT scanner uses ultrasound waves reflected off tissue interfaces, while a conventional X-ray uses ionizing radiation
D. A CT scanner requires IV contrast for every acquisition, while a conventional X-ray never uses contrast
E. A CT scanner detects radiofrequency signals emitted by hydrogen nuclei, while a conventional X-ray detects transmitted photons
A. Correct. A CT scanner uses a motorized X-ray source that shoots narrow beams while rotating around the patient, with digital X-ray detectors positioned directly opposite the source; a conventional X-ray uses a fixed tube sending X-rays in only one direction.
A 24-year-old man is struck in the temporal region during a bar fight. He briefly loses consciousness, then wakes up and seems fine, talking normally with paramedics. Two hours later, in the emergency department, he becomes progressively more confused and then unresponsive. Which sequence of events best explains this presentation?
A. Skull fracture near the pterion tears the middle meningeal artery, causing arterial blood to
accumulate in the epidural space, with a lucid interval followed by hematoma expansion and rising intracranial pressure
B. A ruptured berry aneurysm bleeds into the subarachnoid space, producing a thunderclap headache followed by gradual improvement
C. Bridging veins are sheared by deceleration forces, producing a slowly enlarging subdural collection with no lucid interval
D. Impaired CSF reabsorption at the arachnoid granulations produces a gradually enlarging communicating hydrocephalus
E. A dural tear at the cribriform plate allows CSF to leak into the nasal cavity, producing a salty postnasal drip
A. Correct. This is the classic epidural hematoma sequence: temporal trauma near the pterion tears the middle meningeal artery, arterial blood accumulates in the (normally potential) epidural space, producing a lucid interval followed by rapid deterioration as the hematoma expands and intracranial pressure rises.
A 45-year-old woman notices a midline anterior neck mass that moves upward when she swallows. Ultrasound shows a fluid-filled tract extending from the region of the hyoid bone to the mass. This presentation is most consistent with a persistent remnant of which embryologic structure?
A. Buccopharyngeal membrane
B. Thyroid ima artery
C. Cricothyroid ligament
D. Pharyngotympanic tube
E. Thyroglossal duct
E. A midline neck mass that moves with swallowing and tracks to a duct near the hyoid bone is the classic presentation of a thyroglossal duct cyst, resulting from persistence of the embryologic tract along which the thyroid gland migrates from the tongue base to its final pretracheal position.
A 6-year-old is found to have a midline anterior neck mass that rises when she swallows and when she protrudes her tongue. Which diagnosis is most likely, and what is its embryologic basis?
A. Thyroglossal duct cyst, from a persistent thyroglossal duct
B. Branchial cleft cyst, from incomplete cervical sinus obliteration
C. Cystic hygroma, from a dilated jugular lymphatic sac
D. Ranula, from a blocked sublingual gland duct
E. Ectopic thymic tissue, from failure of thymic descent
A — A midline neck mass that rises with swallowing and tongue protrusion is the classic presentation of a thyroglossal duct cyst, arising from a persistent (non-regressed) thyroglossal duct.
Which cervical vertebra is identified by its long, prominent, non-bifid spinous process, and typically lacks vertebral artery passage through its transverse foramen?
A. C7
B. C1
C. C2
D. C5
E. C6
A — C7 (the “vertebra prominens”) has a long, prominent spinous process that is typically not bifid, and a relatively small transverse foramen through which the vertebral artery typically does not pass (it usually enters at C6).
Which of the following correctly describes how contrast is used when imaging the brain by CT?
A. Oral contrast alone is used, since it best opacifies intracranial vessels
B. Rectal contrast alone is used for all acute intracranial pathology
C. Oral and rectal contrast are combined for all brain studies
D. A combination of oral, rectal, and IV contrast is required for every brain CT
E. Only IV contrast is used to image the brain; oral and rectal contrast are used to image the GI tract, not the brain
E. Correct. Neither oral nor rectal contrast is used to image the brain — only IV contrast is used; oral and rectal routes are reserved for imaging the GI tract.
Unlike the epidural and subdural spaces, the subarachnoid space is best described as which of the following?
A. A potential space that only opens when a bridging vein tears
B. A potential space that only opens when the middle meningeal artery is lacerated
C. An actual, normally present space containing CSF, trabeculae, and cerebral arteries and veins
D. A space located between the periosteal and meningeal layers of the dura
E. A space that exists only in the posterior cranial fossa
C. Correct. Unlike the epidural and subdural spaces (both potential spaces), the subarachnoid space is an actual, normally present space containing CSF, arachnoid trabeculae, and cerebral arteries and veins.
Which prevertebral neck muscle has three distinct parts (superior oblique, vertical, and inferior oblique) whose differing fiber orientations allow it to produce both flexion and rotation of the neck?
A. Longus colli
B. Longus capitis
C. Rectus capitis anterior
D. Rectus capitis lateralis
E. Anterior scalene
A. Longus colli has three parts — superior oblique, vertical, and inferior oblique — and this varied fiber orientation lets it both flex and rotate the neck, unlike the single-direction prevertebral flexors.
An infant presents with recurrent infections, seizures due to hypocalcemia, and a ventricular septal defect. Genetic testing reveals a 22q11.2 deletion. Defective development of which structures underlies this presentation?
A. Third and fourth pharyngeal pouches
B. First and second pharyngeal arches
C. First and second pharyngeal clefts
D. Thyroglossal duct
E. Occipital somites
A — This presentation (recurrent infections from thymic hypoplasia, hypocalcemic seizures from hypoparathyroidism, and a congenital heart defect) with a 22q11.2 deletion is DiGeorge syndrome, caused by defective development of the third and fourth pharyngeal pouch system.
The maxillary nerve (CN V2), the mandibular nerve (CN V3), and the middle meningeal artery pass through three adjacent foramina in the greater wing of the sphenoid bone, from medial to lateral. Which sequence is correct?
A. Foramen ovale, foramen rotundum, foramen spinosum
B. Foramen spinosum, foramen ovale, foramen rotundum
C. Foramen rotundum, foramen ovale, foramen spinosum
D. Foramen rotundum, foramen spinosum, foramen ovale
E. Foramen ovale, foramen spinosum, foramen rotundum
C — From medial to lateral in the greater wing of the sphenoid: foramen rotundum (CN V2), foramen ovale (CN V3), foramen spinosum (middle meningeal artery). This is the order given directly in lecture. All other answer choices scramble this sequence.
A 19-year-old male sustains blunt head trauma with an associated skull fracture and is found to have an epidural hematoma. Which vessel is most likely torn, and how should this be managed?
A. Bridging veins — managed with close observation only
B. Superior sagittal sinus — managed with close observation only
C. Middle meningeal artery — managed as a neurologic emergency requiring fast surgical treatment
D. Anterior cerebral artery — managed with anticoagulation
E. Posterior communicating artery — managed with endovascular coiling
C. Correct. About 85% of epidural hematomas are caused by tearing of the middle meningeal artery secondary to skull fracture, and this is a neurologic emergency requiring fast surgical treatment.
Epidural and subdural hematomas are sometimes remembered using a “lemon vs. banana” shape mnemonic on CT. Which statement correctly explains the anatomical basis for this shape difference?
A. Epidural hematomas are under venous pressure and are therefore concave, while subdural hematomas are under arterial pressure and are therefore convex
B. Epidural hematomas are under arterial pressure and are convex, but their spread is limited by the dura’s tight attachment to the skull at sutures; subdural hematomas are under venous pressure and, without that same restriction, can spread more broadly, producing a concave/crescent shape
C. Both hematoma types have an identical shape on CT and cannot be distinguished by imaging alone
D. The shape difference reflects the volume of blood only, not the vessel type or pressure system involved
E. Subdural hematomas are always smaller than epidural hematomas, which is why they appear concave
B. Correct. Epidural hematomas are under arterial pressure and are convex, but the dura’s tight attachment to the skull at sutures limits their spread; subdural hematomas are under venous pressure and, lacking that same restriction, spread more broadly across the brain’s surface, producing a concave/crescent shape.
A 6-year-old child presents to the emergency department after aspirating a small toy piece. On endoscopy, the object is lodged in a mucosal recess located lateral to the aryepiglottic fold, just outside the larynx proper. Which structure is this?
A. Vallecula
B. Infraglottic cavity
C. Laryngeal ventricle
D. Rima glottidis
E. Piriform recess
E. The piriform recess sits lateral to the aryepiglottic fold, outside the larynx proper, and is the classic site where an aspirated or swallowed foreign body can lodge.
How many pairs of pharyngeal arches are present in mammalian embryos, and which number is absent?
A. 5 pairs, numbered 1, 2, 3, 4, and 6 — there is no arch 5
B. 6 pairs, numbered 1 through 6
C. 4 pairs, numbered 1 through 4
D. 5 pairs, numbered 1 through 5
E. 5 pairs, numbered 2 through 6 — there is no arch 1
A — There are 5 pairs of pharyngeal arches, numbered 1, 2, 3, 4, and 6; there is no 5th arch in mammals (it persists in some non-mammalian species but either fails to form or fully regresses in mammals).
Cranial nerves IX, X, and XI, along with the continuation of the sigmoid sinus into the internal jugular vein, pass through which structure, located at the junction of the temporal and occipital bones?
A. Jugular foramen
B. Foramen magnum
C. Foramen lacerum
D. Internal acoustic meatus
E. Foramen spinosum
A — The jugular foramen, at the junction of the temporal and occipital bones, transmits CN IX, X, and XI along with the sigmoid sinus’s continuation as the internal jugular vein.
A child’s head CT shows ventriculomegaly resulting from a structural blockage within the ventricular system. Which type of hydrocephalus is this, and is intracranial pressure typically elevated?
A. Obstructive (non-communicating) hydrocephalus; ICP typically elevated
B. Communicating hydrocephalus; ICP typically elevated
C. Normal pressure hydrocephalus; ICP typically normal
D. Obstructive (non-communicating) hydrocephalus; ICP typically normal
E. Communicating hydrocephalus; ICP typically normal
A. Correct. Obstructive (non-communicating) hydrocephalus results from structural blockage of CSF flow within the ventricular system, is the most common form seen in children, and is almost always associated with increased intracranial pressure.
A 67-year-old right-handed woman develops sudden right-sided face and arm weakness, greater than leg weakness, along with difficulty producing speech. Which vessel is most likely occluded, and why does the speech deficit occur?
A. Right anterior cerebral artery; speech is affected because the ACA supplies bilateral speech centers
B. Left posterior cerebral artery; the deficit reflects loss of the visual association cortex
C. Left middle cerebral artery; the MCA supplies the lateral cortex including the face/arm homunculus and, when the dominant (typically left) hemisphere is involved, the speech centers
D. Right vertebral artery; the deficit reflects a cerebellar infarct
E. Left anterior cerebral artery; the deficit reflects loss of the medial frontal lobe alone
C. Correct. The left middle cerebral artery supplies the lateral aspect of the brain, including 14 the motor/sensory homunculus regions for the face and arm, and — because this is the dominant (left) hemisphere in most people — the speech centers, explaining both the contralateral face/arm weakness and the speech deficit.
During a lateral neck dissection, a superior root and an inferior root are traced to a nerve loop lying superficial to the internal jugular vein. The superior root travels for a short distance alongside a cranial nerve before diverging from it. Which spinal levels contribute the superior and inferior roots of this loop, respectively?
A. C1; C2–C3
B. C2–C3; C1
C. C3–C5; C1–C2
D. C1; C3–C5
E. C2; C3–C4
A. The ansa cervicalis’s superior root is C1 (which travels briefly alongside the hypoglossal nerve before diverging — the loop that looks like it comes off CN XII is actually C1 fibers); its inferior root is C2–C3.
The intrinsic muscles of the tongue are innervated by the hypoglossal nerve (CN XII) rather than by any of the pharyngeal-arch-associated cranial nerves. What is the embryologic explanation for this?
A. The myoblasts forming the intrinsic tongue muscles originate from the occipital somites, not from pharyngeal arch mesenchyme
B. The tongue’s intrinsic muscles are actually 2nd arch derivatives, and CN VII was mislabeled historically
C. CN XII is itself a pharyngeal arch nerve, associated with the 6th arch
D. The intrinsic tongue muscles are neural crest–derived and therefore exempt from arch innervation rules
E. The tongue has no intrinsic muscles; all tongue muscles are extrinsic and pharyngeal arch–derived
A — The myoblasts that form the intrinsic muscles of the tongue originate from the occipital somites, not from pharyngeal arch mesenchyme, which is why these muscles are innervated by the hypoglossal nerve (CN XII) rather than one of the pharyngeal-arch-associated cranial nerves (V, VII, IX, X).
A patient reports painless clicking and popping of the jaw with intermittent locking during chewing. This is most likely related to dysfunction of the articular disc within which joint?
A. Atlanto-occipital joint
B. Atlanto-axial joint
C. Zygomaticotemporal suture
D. Temporomandibular joint (TMJ)
E. Squamous suture
D — The temporomandibular joint (TMJ) contains an articular disc between the mandibular condyle and the temporal bone; disc displacement or abnormal joint movement can cause clicking, popping, and locking — classic features of TMJ disorders.
A 70-year-old with poorly controlled hypertension presents with sudden-onset weakness. CT shows a hyper-dense lesion confined to the substance of the brain tissue itself, not within a ventricle or an extra-axial space. What is the most likely etiology of this hemorrhage?
A. Tearing of the middle meningeal artery
B. Tearing of the bridging veins
C. Hypertensive vasculitis
D. Rupture of a saccular aneurysm
E. An arteriovenous malformation
C. Correct. Hypertensive vasculitis is the most common etiology of intraparenchymal hemorrhage, which is the second most common cause of stroke after ischemia.