Free NEET PG & INI-CET Anatomy MCQs

Explanation

The upper trunk is formed by C5 and C6, and traction that widens the head-to-shoulder angle stretches it at Erb point. Loss of the deltoid, supraspinatus, infraspinatus and biceps leaves the limb adducted, medially rotated, extended and pronated. C8 and T1 injury instead produces a claw hand from intrinsic muscle paralysis.

Explanation

The axillary nerve winds around the surgical neck, so a fracture there is its classic injury site. It supplies deltoid, the main abductor beyond the first 15 degrees, and gives the upper lateral cutaneous nerve of the arm to the regimental badge area. Supraspinatus, supplied by the suprascapular nerve, initiates abduction, which is why the first few degrees are preserved.

Explanation

The radial nerve lies directly against bone in the spiral groove of the humeral shaft, so mid-shaft fractures injure it. It supplies all the extensors of the wrist and fingers, and losing them gives wrist drop. Its cutaneous territory includes the dorsal skin of the first web space, which is the small area most reliably affected.

Explanation

The ulnar nerve passes in a groove behind the medial epicondyle, where it is subcutaneous and easily struck. It supplies most intrinsic hand muscles, and losing the lumbricals to the fourth and fifth digits leaves the metacarpophalangeal joints extended and the interphalangeal joints flexed. Sensation over the medial one and a half digits is also ulnar territory.

Explanation

The long thoracic nerve arises from the C5, C6 and C7 roots and runs superficially on serratus anterior along the chest wall, which puts it at risk during axillary surgery. Serratus anterior holds the medial border of the scapula against the thorax and protracts it. Without it the medial border lifts away, most obviously when the arm pushes forward against resistance.

Explanation

The three trigeminal divisions exit in order from front to back and top to bottom: V1 through the superior orbital fissure, V2 through foramen rotundum and V3 through foramen ovale. Foramen spinosum carries the middle meningeal artery, not a nerve division. Remembering the sequence rotundum then ovale for V2 then V3 covers most questions on the topic.

Explanation

Foramen ovale transmits the mandibular division, V3, along with the accessory meningeal artery and the lesser petrosal nerve. V3 is the only trigeminal division carrying motor fibres, which is why a lesion here weakens the muscles of mastication. The facial nerve leaves through the stylomastoid foramen instead.

Explanation

The jugular foramen transmits cranial nerves IX, X and XI along with the internal jugular vein. Glossopharyngeal loss removes the afferent limb of the gag reflex, vagal loss gives hoarseness through the recurrent laryngeal branch, and accessory loss weakens trapezius and sternocleidomastoid. The hypoglossal canal carries only CN XII, so tongue deviation without these features points there instead.

Explanation

The superior orbital fissure carries the three ocular motor nerves, III, IV and VI, the branches of V1 and the superior ophthalmic vein. The optic nerve takes a separate route through the optic canal, accompanied by the ophthalmic artery. That separation explains why an optic canal lesion can spare eye movements while abolishing vision.

Explanation

The trochlear nerve is unique in leaving the brainstem dorsally, just below the inferior colliculus, and it decussates before doing so. It therefore supplies the superior oblique of the opposite side and has the longest intracranial course, which makes it vulnerable in head injury. Superior oblique depresses and intorts the adducted eye, so patients complain of vertical diplopia going down stairs.

Explanation

Cranial nerves III, IV, V1 and V2 run within the lateral wall of the cavernous sinus, while the abducent nerve runs free in the sinus alongside the internal carotid artery. Being surrounded by blood rather than protected by dura, it is the first to suffer when pressure rises. The result is a lateral rectus palsy with failure of abduction.

Explanation

The femoral triangle is bounded above by the inguinal ligament, laterally by the medial border of sartorius and medially by the medial border of adductor longus. Its floor is formed by iliopsoas, pectineus and adductor longus. From lateral to medial its contents run nerve, artery, vein and lymphatics, which the mnemonic NAVEL preserves.

Explanation

The femoral sheath is a downward prolongation of the abdominal fascia and contains three compartments: lateral for the artery, intermediate for the vein and medial for the femoral canal with its lymph node. The femoral nerve lies lateral to the sheath, outside it, deep to the fascia iliaca. This is why a femoral hernia through the canal presents medial to the vessels.

Explanation

The adductor canal transmits the femoral artery, the femoral vein, the saphenous nerve and the nerve to vastus medialis. The saphenous nerve is purely sensory, the terminal cutaneous branch of the femoral nerve, and it leaves the canal without piercing the adductor hiatus. It then supplies skin along the medial leg down to the medial malleolus.

Explanation

The common peroneal nerve winds around the neck of the fibula where it is subcutaneous and lies against bone, making it the most commonly injured nerve in the lower limb. It supplies the dorsiflexors and evertors through its deep and superficial branches, so injury gives foot drop with a high-stepping gait. Sensation over most of the dorsum of the foot is lost as well.

Explanation

The sciatic nerve leaves the pelvis through the greater sciatic foramen, and in roughly 85 per cent of people it passes below piriformis as a single trunk. Variants where a division pierces the muscle are the anatomical basis proposed for piriformis syndrome. The lesser sciatic foramen transmits the tendon of obturator internus and the pudendal neurovascular bundle re-entering the perineum.

Explanation

The thoracic duct ascends from the cisterna chyli, crosses to the left at about the level of T5, and empties at the junction of the left internal jugular and left subclavian veins. It therefore drains the whole body except the right upper limb and the right side of the head, neck and thorax. That remaining territory drains through the right lymphatic duct on the opposite side.

Explanation

The right lymphatic duct drains only the right upper limb and the right half of the head, neck and thorax. Everything below the diaphragm, including both lower limbs, drains into the cisterna chyli and then the thoracic duct. The common error is to assume that a right-sided structure must use the right duct, which holds only above the diaphragm.

Explanation

The left anterior descending artery runs in the anterior interventricular groove and gives septal perforators to the anterior two thirds of the septum. It also supplies the anterior wall of the left ventricle and the apex, which is why its occlusion is the most consequential coronary lesion. The posterior third of the septum comes from the posterior interventricular artery.

Explanation

The sinuatrial nodal artery arises from the right coronary artery in about 60 per cent of hearts and from the circumflex in the remainder. The atrioventricular node is likewise usually right coronary territory, supplied at the crux of the heart. This is why an inferior infarct from right coronary occlusion so often produces bradycardia and heart block.

Explanation

Roughly 85 per cent of hearts are right dominant, meaning the posterior interventricular artery arises from the right coronary artery. About 8 per cent are left dominant, with the branch coming from the circumflex, and the remainder are codominant. Dominance matters because it determines which vessel supplies the inferior wall and the atrioventricular node.

Explanation

The azygos vein arches forward over the right lung root at about the level of the sternal angle, which corresponds to the T4 and T5 disc. The same plane marks the start and end of the aortic arch, the bifurcation of the trachea and the division between superior and inferior mediastinum. Grouping these landmarks at one level is far more efficient than memorising them separately.

Explanation

The deep ring is a defect in the transversalis fascia, lying about midway between the anterior superior iliac spine and the pubic symphysis, just lateral to the inferior epigastric vessels. The superficial ring by contrast is a triangular gap in the external oblique aponeurosis above the pubic tubercle. The internal spermatic fascia the cord picks up at the deep ring is derived from transversalis fascia.

Explanation

The inferior epigastric vessels are the landmark that separates the two inguinal hernias: indirect sacs come through the deep ring lateral to them, direct sacs push through the weak posterior wall medial to them. Direct hernias are acquired and rarely enter the scrotum, whereas indirect ones follow the cord and often do. A femoral hernia lies below the inguinal ligament and lateral to the pubic tubercle.

Explanation

At the lower oesophagus the left gastric vein of the portal system anastomoses with oesophageal veins draining into the azygos system, which is systemic. When portal pressure rises, flow reverses through this channel and the submucosal veins distend into varices. The other classic sites are the anorectal junction, the periumbilical region giving caput medusae, and the retroperitoneum.

Explanation

The coeliac trunk supplies foregut structures from the lower oesophagus to the second part of the duodenum, as far as the entry of the bile duct. Beyond that point the midgut takes over with the superior mesenteric artery. The transition at the ampulla is also where the arterial, venous, lymphatic and autonomic supply all change, which makes it a favourite examination landmark.

Explanation

The superior mesenteric artery is the midgut vessel, supplying from just beyond the bile duct entry in the duodenum to about two thirds of the way along the transverse colon. The hindgut from that point to the upper rectum belongs to the inferior mesenteric artery. The junction near the splenic flexure is a watershed zone and a common site for ischaemic colitis.

Explanation

From front to back the hilum contains the renal vein, then the renal artery, then the renal pelvis continuing as the ureter. The vein lies most anterior because it drains forward into the inferior vena cava, which sits ahead of the aorta. The left renal vein is the longer of the two and crosses in front of the aorta beneath the superior mesenteric artery.

Explanation

Each pharyngeal arch keeps its own nerve however far its muscles migrate. Arch one takes V3 and gives the muscles of mastication, mylohyoid, the anterior belly of digastric, tensor tympani and tensor veli palatini. Arch two takes the facial nerve, arch three the glossopharyngeal, and arches four and six the vagus.

Explanation

Stapedius is a second arch muscle and is therefore supplied by the facial nerve, the nerve of that arch. This is why facial nerve palsy proximal to the nerve to stapedius produces hyperacusis, since the muscle can no longer damp stapes movement. Tensor tympani, by contrast, is a first arch muscle supplied by V3.

Explanation

Arch four is supplied by the superior laryngeal branch of the vagus and arch six by the recurrent laryngeal branch. All the intrinsic laryngeal muscles except cricothyroid derive from arch six and are therefore recurrent laryngeal territory. Cricothyroid is the arch four exception, supplied by the external branch of the superior laryngeal nerve.

Explanation

Meckel diverticulum is the persistent proximal part of the vitellointestinal duct, which normally obliterates in the seventh week. It is a true diverticulum containing all bowel layers, arises from the antimesenteric border of the ileum, and may contain ectopic gastric or pancreatic tissue. The ectopic gastric mucosa is what causes painless bleeding in children.

Explanation

The ductus arteriosus connects the pulmonary trunk to the aortic arch in fetal life and closes functionally within hours of birth, leaving the ligamentum arteriosum. The left recurrent laryngeal nerve hooks under this ligament, which explains its long course in the chest. The umbilical vein becomes the ligamentum teres and the ductus venosus becomes the ligamentum venosum.

Explanation

The notochord regresses in the vertebral bodies but persists between them as the nucleus pulposus, the only adult remnant of the structure. The surrounding anulus fibrosus and the vertebral bodies themselves come from sclerotome. Chordoma, a tumour of notochordal remnants, arises for the same reason at the sacrococcygeal and clival ends of the axis.

Explanation

The trachea is lined by pseudostratified ciliated columnar epithelium with goblet cells, the classic respiratory epithelium. Every nucleus sits at a different height, which makes it look layered, but all cells reach the basement membrane. The cilia and mucus together form the mucociliary escalator that clears particles upward.

Explanation

Transitional epithelium, or urothelium, lines the urinary tract from the renal calyces to the proximal urethra. Its umbrella cells flatten as the bladder fills, letting the lining stretch without breaking, and its tight junctions keep urine from leaking into tissue. The oesophagus by contrast is stratified squamous non-keratinised.

Explanation

Type II pneumocytes are cuboidal cells that make and secrete surfactant, and they also act as the progenitor for both alveolar cell types after injury. Type I pneumocytes are thin squamous cells that cover about 95 per cent of the alveolar surface and handle gas exchange. Surfactant lowers surface tension and prevents alveolar collapse at end expiration.

Explanation

Purkinje fibres are modified cardiac myocytes that are larger and paler than working muscle, packed with glycogen and relatively sparse in myofibrils. That structure suits conduction rather than contraction and gives them the fastest conduction velocity in the heart. They remain cardiac muscle, so they keep their intercalated discs and striations.

Explanation

Adjacent Sertoli cells are joined by tight junctions that divide the seminiferous tubule into a basal and an adluminal compartment. This isolates developing germ cells from the immune system, which matters because meiotic cells express antigens the body has never seen. Leydig cells sit outside the tubule in the interstitium and secrete testosterone.

Explanation

Three structures pass through the parotid, and their depth is fixed: the facial nerve is most superficial, the retromandibular vein lies deep to it, and the external carotid artery is deepest. The nerve divides within the gland into its five terminal branches without supplying the gland itself. Its superficial position is why superficial parotidectomy carries a real risk of facial weakness.

Explanation

The recurrent laryngeal nerve runs in the tracheo-oesophageal groove and has a variable relationship to the branches of the inferior thyroid artery, passing in front, behind or between them. Ligating that artery close to the gland rather than on the main trunk keeps the dissection away from the nerve. The superior thyroid artery has the same problem with the external laryngeal nerve, which is why it is ligated close to the upper pole.

Explanation

The posterior triangle is bounded in front by the posterior border of sternocleidomastoid, behind by the anterior border of trapezius, and below by the middle third of the clavicle. The inferior belly of omohyoid crosses it and subdivides it into occipital and supraclavicular parts. The accessory nerve crosses the triangle superficially and is at risk during lymph node biopsy here.

Explanation

The carotid sheath contains the common and internal carotid arteries, the internal jugular vein and the vagus nerve, with the vein lateral, the artery medial and the nerve between and behind them. The sympathetic chain lies behind the sheath, embedded in prevertebral fascia, not inside it. That separation is why a sheath lesion need not cause Horner syndrome.

Explanation

The lingual nerve loops under the submandibular duct, passing from lateral to medial as it descends and then ascending on its medial side to reach the tongue. It is one of the few places where a nerve spirals around a duct rather than running alongside it. The relationship matters in surgery for submandibular calculi, where the nerve lies directly in the operative field.

Explanation

The lenticulostriate arteries are small perforating branches of the middle cerebral artery that supply much of the internal capsule and basal ganglia. They arise at right angles from a large vessel, which exposes them to high pressure and makes them the classic site of hypertensive haemorrhage and lacunar infarction. Because corticospinal fibres are densely packed there, a tiny lesion can cause a dense contralateral hemiplegia.

Explanation

About 85 per cent of corticospinal fibres cross in the pyramidal decussation at the lower medulla and descend as the lateral corticospinal tract. The uncrossed remainder forms the anterior corticospinal tract and decussates segmentally. Because the crossing is above the cord, a cortical or capsular lesion causes weakness on the opposite side of the body while a cord lesion causes it on the same side.

Explanation

The dorsal columns carry fine touch, vibration and proprioception without synapsing until the medulla. Fibres from below T6 travel in the medially placed fasciculus gracilis and relay in the nucleus gracilis, while those from above T6 use the laterally placed fasciculus cuneatus. Second order fibres then cross as the internal arcuate fibres to form the medial lemniscus.

Explanation

The oculomotor nerve runs beside the posterior communicating artery, so an aneurysm there compresses it. The parasympathetic pupilloconstrictor fibres travel on the outside of the nerve, which is why compression blows the pupil early while ischaemic third nerve palsies from diabetes typically spare it. Unopposed lateral rectus and superior oblique action leaves the eye down and out.

Explanation

The palmar cutaneous branch of the median nerve leaves the trunk about 5 cm proximal to the wrist and crosses superficial to the flexor retinaculum rather than through the tunnel. Compression under the retinaculum therefore spares the skin of the thenar eminence while affecting the lateral three and a half digits. Preserved thenar sensation with numb fingers is a useful sign that the lesion is at the tunnel rather than higher.

Explanation

The scaphoid forms the floor of the anatomical snuffbox, so tenderness there after a fall on the outstretched hand suggests its fracture. Its nutrient vessels enter near the distal pole and run backwards through the bone, so a waist fracture cuts off the proximal fragment. That retrograde supply is why avascular necrosis and non-union are common and why suspected fractures are immobilised even with normal initial films.