Chapter: Embryology; Topic: Development of Endocrine System; Subtopic: Development of Pituitary Gland (Rathke’s Pouch Derivatives)
Keyword Definitions:
• Rathke’s pouch: Ectodermal upward growth from stomodeum that forms anterior pituitary components.
• Adenohypophysis: Anterior pituitary part derived from Rathke’s pouch producing trophic hormones.
• Pars distalis: Largest part of anterior pituitary developed from Rathke’s pouch.
• Pars tuberalis: Pituitary segment derived from Rathke’s pouch surrounding infundibular stalk.
• Neurohypophysis: Posterior pituitary derived from infundibulum of diencephalon.
• Pineal gland: Neuroectodermal gland producing melatonin located in epithalamus.
Lead Question - 2015
Which of the following is a derivative of Rathke's pouch?
a) Pars tuberalis
b) Neurohypophysis
c) Posterior pituitary
d) Pineal gland
Explanation (Answer: a) Pars tuberalis)
Rathke’s pouch, a stomodeal ectodermal diverticulum, gives rise to the pars distalis, pars intermedia, and pars tuberalis of the anterior pituitary. The posterior pituitary (neurohypophysis) derives from neuroectoderm of the infundibulum, while the pineal gland originates from the roof of the diencephalon. The pars tuberalis surrounds the infundibular stalk and plays regulatory roles in endocrine function.
1. Which part of the pituitary develops from the infundibulum?
a) Pars distalis
b) Pars intermedia
c) Neurohypophysis
d) Pars tuberalis
Explanation (Answer: c) Neurohypophysis)
The neurohypophysis (posterior pituitary) develops from a downward extension of the diencephalon known as the infundibulum. It consists of axonal terminals of hypothalamic neurons storing ADH and oxytocin. In contrast, Rathke’s pouch gives rise to pars distalis, pars intermedia, and pars tuberalis of the anterior pituitary, all of ectodermal origin.
2. Pars distalis primarily secretes which hormone?
a) ADH
b) Oxytocin
c) Growth hormone
d) Melatonin
Explanation (Answer: c) Growth hormone)
The pars distalis, derived from Rathke’s pouch, is the largest functional portion of the anterior pituitary. It secretes several hormones including GH, ACTH, TSH, FSH, LH, and prolactin. GH stimulates growth and protein synthesis. ADH and oxytocin originate from hypothalamus and are stored in the posterior pituitary, while melatonin is secreted by the pineal gland.
3. Craniopharyngioma originates from remnants of:
a) Infundibulum
b) Rathke’s pouch
c) Pineal gland
d) Neurohypophysis
Explanation (Answer: b) Rathke’s pouch)
Craniopharyngioma is a benign but invasive tumor originating from epithelial remnants of Rathke’s pouch. It commonly presents in children with headaches, visual impairment, and growth disturbances due to compression of the optic chiasma and pituitary gland. Calcifications are characteristic on imaging. It is embryologically linked to anterior pituitary development.
4. Which pituitary lobe stores oxytocin and ADH?
a) Pars distalis
b) Pars intermedia
c) Pars tuberalis
d) Posterior pituitary
Explanation (Answer: d) Posterior pituitary)
The posterior pituitary stores and releases ADH and oxytocin, although these hormones are synthesized in the hypothalamus. It derives from neuroectoderm of the infundibulum, unlike anterior pituitary components derived from Rathke’s pouch. Damage to the posterior pituitary causes diabetes insipidus due to lack of ADH regulation.
5. A 12-year-old presents with delayed growth and calcified suprasellar mass. Likely diagnosis?
a) Prolactinoma
b) Craniopharyngioma
c) Pinealoma
d) Pituitary apoplexy
Explanation (Answer: b) Craniopharyngioma)
A calcified suprasellar mass in a child suggests craniopharyngioma, a tumor derived from Rathke’s pouch remnants. Symptoms include visual field defects, growth failure due to pituitary compression, and hormonal imbalance. MRI shows cystic and solid components with calcification. Treatment involves surgical removal and hormone replacement therapy.
6. Pars intermedia is responsible for secretion of:
a) ACTH
b) MSH
c) TSH
d) Prolactin
Explanation (Answer: b) MSH)
The pars intermedia, originating from Rathke’s pouch, secretes melanocyte-stimulating hormone (MSH). This part is prominent in lower vertebrates but rudimentary in humans. It regulates melanogenesis. Other anterior pituitary hormones such as ACTH, TSH, and prolactin are secreted by pars distalis, not pars intermedia.
7. Posterior pituitary is derived from which embryonic layer?
a) Surface ectoderm
b) Neural ectoderm
c) Mesoderm
d) Endoderm
Explanation (Answer: b) Neural ectoderm)
The posterior pituitary (neurohypophysis) develops from the neural ectoderm of the diencephalon. It remains connected to hypothalamus through the infundibular stalk and releases stored oxytocin and ADH. This contrasts with anterior pituitary derivatives from surface ectoderm via Rathke’s pouch.
8. A lesion affecting pars tuberalis disrupts regulation of:
a) Thyroid function
b) Pineal secretion
c) Hypothalamic–pituitary signaling
d) ADH storage
Explanation (Answer: c) Hypothalamic–pituitary signaling)
The pars tuberalis surrounds the pituitary stalk and is involved in transport of hypothalamic releasing hormones to anterior pituitary. Damage to this region affects endocrine regulation, leading to hormonal imbalances. Since it derives from Rathke’s pouch, its dysfunction affects anterior rather than posterior pituitary function.
9. Which structure forms due to fusion between Rathke’s pouch and infundibulum?
a) Hypophyseal stalk
b) Complete pituitary gland
c) Optic cup
d) Pineal body
Explanation (Answer: b) Complete pituitary gland)
The pituitary gland forms by union of Rathke’s pouch (anterior pituitary origin) and infundibulum (posterior pituitary origin). This dual embryologic origin explains distinct hormonal functions. Failure of proper fusion may cause pituitary hypoplasia or ectopic pituitary tissue along the stalk pathway.
10. A tumor compressing only the posterior pituitary will most likely cause:
a) Hyperprolactinemia
b) Panhypopituitarism
c) Diabetes insipidus
d) Acromegaly
Explanation (Answer: c) Diabetes insipidus)
Compression of the posterior pituitary disrupts ADH release, resulting in central diabetes insipidus characterized by polyuria and polydipsia. Anterior pituitary functions, derived from Rathke’s pouch, remain intact, so no hyperprolactinemia or growth hormone excess occurs unless broader pituitary compression develops.
Chapter: Embryology; Topic: Development of Nervous System; Subtopic: Origin of Glial Cells
Keyword Definitions:
• Microglial cells: Phagocytic glial cells of the CNS derived from mesodermal mesenchyme.
• Macroglial cells: Glial cells including astrocytes and oligodendrocytes derived from neuroectoderm.
• Oligodendrocytes: Myelin-forming glial cells in CNS derived from neuroectoderm.
• Ependymal cells: Neuroectodermal cells lining ventricles and central canal of spinal cord.
• Mesoderm: Middle germ layer giving rise to microglia, blood cells, and connective tissues.
• Neuroectoderm: Embryonic tissue forming neurons, macroglia, retina, and CNS structures.
Lead Question - 2015
Which of glial cell is mesodermal in origin -
a) Macroglial cells
b) Microglial cells
c) Oligodendrocytes
d) Ependymal cells
Explanation (Answer: b) Microglial cells)
Microglial cells are the only glial cells derived from the mesoderm. They originate from mesenchymal cells of embryonic yolk sac and migrate into the CNS. They act as resident macrophages and participate in immune surveillance, phagocytosis, debris removal, and inflammatory response. All other glial cells—astrocytes, oligodendrocytes, and ependymal cells—are derived from neuroectoderm.
1. Astrocytes are derived from:
a) Mesoderm
b) Neuroectoderm
c) Endoderm
d) Neural crest
Explanation (Answer: b) Neuroectoderm)
Astrocytes develop from the neuroectoderm and perform essential supportive functions such as maintaining blood–brain barrier, neurotransmitter uptake, and ionic balance. They are macroglial cells, unlike microglia, which originate from mesoderm. Astrocytic dysfunction may contribute to neurological conditions like gliosis, epilepsy, and neuroinflammation.
2. Which glial cell is responsible for myelinating CNS axons?
a) Schwann cells
b) Oligodendrocytes
c) Microglial cells
d) Astrocytes
Explanation (Answer: b) Oligodendrocytes)
Oligodendrocytes originate from the neuroectoderm and myelinate multiple CNS axons. Each oligodendrocyte may supply myelin to several neurons. Schwann cells perform similar functions in the PNS but are derived from neural crest. Microglia, although glial in name, are immune cells from mesodermal origin and do not participate in myelination.
3. Which glial cell proliferates most actively after CNS injury?
a) Ependymal cells
b) Microglial cells
c) Oligodendrocytes
d) Astrocytes
Explanation (Answer: b) Microglial cells)
Microglial cells, derived from mesoderm, proliferate rapidly after CNS injury and act as phagocytes removing damaged tissue. They secrete cytokines, initiate inflammatory responses, and contribute to neurodegeneration in severe injuries. Their activation is an indicator of CNS pathology, seen in stroke, infections, trauma, and neurodegenerative diseases.
4. Ependymal cells line which structure?
a) Blood–brain barrier
b) Ventricles of the brain
c) Optic nerve
d) Peripheral nerves
Explanation (Answer: b) Ventricles of the brain)
Ependymal cells are derived from neuroectoderm and line the brain ventricles and central canal of the spinal cord. They form the epithelial component of the choroid plexus and help circulate cerebrospinal fluid. They are not mesodermal like microglia and do not form myelin or participate in immune surveillance.
5. A patient with brain infection shows increased activation of phagocytic glial cells. Which cells are these?
a) Astrocytes
b) Microglial cells
c) Oligodendrocytes
d) Ependymal cells
Explanation (Answer: b) Microglial cells)
Microglial cells, the CNS macrophages, are mesodermal in origin and increase during infection or inflammation. They remove pathogens and debris, present antigens, and release inflammatory mediators. Astrocytes and oligodendrocytes do not exhibit phagocytic properties. Ependymal cells maintain ventricular lining but do not participate in immune responses.
6. Schwann cells are derived from which embryonic structure?
a) Neuroectoderm
b) Surface ectoderm
c) Neural crest
d) Mesoderm
Explanation (Answer: c) Neural crest)
Schwann cells, responsible for myelinating peripheral nerves, originate from neural crest cells. Unlike CNS oligodendrocytes, Schwann cells myelinate only one axon segment each. Neural crest derivatives include melanocytes, adrenal medulla, and craniofacial structures. They are not mesodermal like microglia.
7. Which glial cell participates in forming the blood–brain barrier (BBB)?
a) Oligodendrocytes
b) Astrocytes
c) Microglial cells
d) Ependymal cells
Explanation (Answer: b) Astrocytes)
Astrocytes extend foot processes that envelope capillaries and help maintain the blood–brain barrier. They regulate extracellular ion concentration, uptake neurotransmitters, and support neuronal metabolism. They are neuroectodermal and structurally distinct from mesoderm-derived microglia that function as CNS macrophages.
8. A brain biopsy reveals proliferative cells of mesodermal origin. These are most likely:
a) Astrocytes
b) Microglial cells
c) Ependymal cells
d) Oligodendrocytes
Explanation (Answer: b) Microglial cells)
Microglial cells proliferate in response to CNS injury or infection. They are mesodermal in origin and are related to monocyte–macrophage lineage. Their presence indicates inflammation or tissue degeneration. Other glial cells like astrocytes and ependymal cells are derived from neuroectoderm and do not show similar macrophage-like activity.
9. Which glial cell is involved in myelinating peripheral axons?
a) Astrocytes
b) Oligodendrocytes
c) Microglial cells
d) Schwann cells
Explanation (Answer: d) Schwann cells)
Schwann cells, derived from neural crest, are involved in myelinating PNS axons. Each cell covers a single axon segment. In contrast, oligodendrocytes myelinate CNS axons. Microglia, the mesodermal phagocytes, do not participate in myelination. Damage to Schwann cells results in demyelinating neuropathies such as Guillain–Barré syndrome.
10. A newborn presents with enlarged ventricles due to impaired CSF flow. Which glial cell malfunction is likely responsible?
a) Microglial cells
b) Ependymal cells
c) Astrocytes
d) Oligodendrocytes
Explanation (Answer: b) Ependymal cells)
Ependymal cells line ventricles and participate in CSF flow regulation through ciliary action. Their dysfunction leads to obstructed CSF movement, resulting in hydrocephalus. Microglia, although mesodermal, are not involved in CSF circulation. Astrocytes and oligodendrocytes have other supportive roles but do not regulate ventricular fluid flow.
Chapter: Embryology; Topic: Development of Urinary System; Subtopic: Formation of Trigone and Derivatives of Mesonephric Duct
Keyword Definitions:
• Trigone of bladder: Smooth triangular area inside urinary bladder derived from incorporated mesonephric ducts.
• Mesonephric duct (Wolffian duct): Embryonic structure forming male genital ducts and contributing to trigone formation.
• Müllerian duct: Embryonic paramesonephric duct forming female reproductive tract; regresses in males.
• Urothelium: Transitional epithelium lining urinary bladder from endoderm.
• Cloaca: Primitive chamber dividing into urogenital sinus and anorectal canal.
• Urogenital sinus: Endodermal structure forming bladder except trigone region.
Lead Question - 2015
Trigone of bladder is derived from?
a) Mesonephric duct
b) Paramesonephric duct
c) Absorbed anal membrane
d) Müllerian duct
Explanation (Answer: a) Mesonephric duct)
The trigone of the urinary bladder develops from the mesonephric (Wolffian) ducts, which are absorbed into the posterior wall of the developing bladder. Although the trigone initially has mesodermal origin, its epithelium later becomes overgrown by endodermal urothelium, giving it the same epithelial lining as the rest of the bladder. It forms a smooth triangular area between ureteric openings and the internal urethral orifice.
1. Urothelium of the urinary bladder develops from:
a) Endoderm
b) Mesoderm
c) Ectoderm
d) Neural crest
Explanation (Answer: a) Endoderm)
The urothelium lining the bladder and urethra develops from the endoderm of the urogenital sinus. Although the trigone initially forms from mesodermal mesonephric ducts, it is secondarily covered by endodermal epithelium. Thus, the entire bladder ultimately has an endodermal epithelial lining, ensuring uniform urothelial characteristics.
2. Ureteric bud gives rise to all except:
a) Renal pelvis
b) Ureter
c) Collecting ducts
d) Detrusor muscle
Explanation (Answer: d) Detrusor muscle)
The ureteric bud forms the ureter, renal pelvis, calyces, and collecting ducts. The detrusor muscle arises from the splanchnic mesoderm surrounding the urogenital sinus, not the ureteric bud. The bud interacts with metanephric mesenchyme to initiate kidney development but does not contribute to bladder musculature formation.
3. Which embryonic structure forms the lower part of the vagina?
a) Müllerian duct
b) Urogenital sinus
c) Mesonephric duct
d) Cloacal membrane
Explanation (Answer: b) Urogenital sinus)
The lower vagina develops from the urogenital sinus through formation of the sinovaginal bulbs. The Müllerian ducts contribute to the upper vagina, uterus, and fallopian tubes. The distinction between upper Müllerian origin and lower sinus origin explains clinical presentations such as vaginal atresia or septal anomalies.
4. Which structure develops from mesonephric duct in males?
a) Uterus
b) Epididymis
c) Labia majora
d) Vagina
Explanation (Answer: b) Epididymis)
The mesonephric duct, under the influence of testosterone, forms the epididymis, vas deferens, seminal vesicle, and ejaculatory ducts in males. In females, this duct largely regresses, leaving remnants such as Gartner’s duct. It also contributes to trigone development but not to female reproductive structures.
5. A newborn presents with smooth bladder floor and abnormal ureteric openings. Developmental defect lies in:
a) Metanephric blastema
b) Mesonephric duct absorption
c) Urogenital sinus fusion
d) Cloacal membrane rupture
Explanation (Answer: b) Mesonephric duct absorption)
The trigone of the bladder forms when the mesonephric ducts are absorbed into the posterior bladder wall. Failure results in abnormal ureteric openings, vesicoureteral reflux, or duplicated ureters. The smooth trigone area becomes distorted, affecting proper urinary flow patterns and increasing infection risk.
6. The ureteric bud develops from which structure?
a) Müllerian duct
b) Mesonephric duct
c) Allantois
d) Pronephric duct
Explanation (Answer: b) Mesonephric duct)
The ureteric bud arises from the mesonephric duct near its attachment to the cloaca. It invades the metanephric mesenchyme and induces kidney formation. The ureteric bud forms collecting ducts, renal pelvis, calyces, and ureters. Defects in bud development lead to renal agenesis, duplex systems, or pelvic kidney formation.
7. The bladder (except trigone) originates from:
a) Mesonephric duct
b) Urogenital sinus
c) Allantois
d) Mesenchyme of cloaca
Explanation (Answer: b) Urogenital sinus)
The bladder, excluding the trigone, originates from the endodermal urogenital sinus. Although mesonephric ducts contribute mesoderm to the trigone region initially, the endodermal lining of the bladder eventually overgrows this region. The body, apex, and neck of the bladder are all sinus-derived, ensuring uniform epithelium.
8. Which of the following is a remnant of the allantois?
a) Ovarian ligament
b) Urachus
c) Gartner’s duct
d) Appendix epididymis
Explanation (Answer: b) Urachus)
The allantois, a vestigial embryonic structure, becomes the urachus, connecting bladder apex to umbilicus. Postnatally, it becomes the median umbilical ligament. Failure of closure leads to urachal cysts, fistulae, or sinuses, causing urinary discharge from the umbilicus or infection in infants.
9. Vesicoureteral reflux is due to abnormal development of:
a) Müllerian duct
b) Ureterovesical junction
c) Allantois
d) Cloacal membrane
Explanation (Answer: b) Ureterovesical junction)
Vesicoureteral reflux arises due to improper formation of the ureterovesical junction. Defective insertion of ureters into the bladder wall (derived from mesonephric duct incorporation) results in retrograde urine flow. This leads to recurrent infections, hydronephrosis, and renal scarring in pediatric patients.
10. A child has duplicated ureter. This results from abnormal division of:
a) Mesonephric duct
b) Pronephric tubule
c) Ureteric bud
d) Urogenital sinus
Explanation (Answer: c) Ureteric bud)
Duplicated ureters occur when the ureteric bud prematurely divides into two buds, each inducing its own collecting system. This may cause ureteral ectopia or reflux. The primary origin of the bud is the mesonephric duct, but duplication occurs after budding, not from mesonephric branching itself.
Chapter: Anatomy; Topic: Upper Limb – Hand Bones; Subtopic: Carpal Bone Articulations
Keyword Definitions:
• Pisiform: A sesamoid carpal bone that lies within the tendon of flexor carpi ulnaris.
• Triquetral: A proximal row carpal bone articulating with pisiform and hamate.
• Sesamoid bone: A bone embedded within a tendon that increases mechanical advantage.
• Flexor carpi ulnaris: A forearm muscle inserting on the pisiform, controlling wrist flexion.
• Carpal bones: Eight small bones forming wrist articulation and hand stability.
• Wrist joint: Complex joint involving radius and carpal bones enabling multi-directional wrist movement.
Lead Question - 2015
Pisiform articulates with -
a) Scaphoid
b) Trapezium
c) Triquetral
d) Lunate
Explanation (Answer: c) Triquetral)
The pisiform is a sesamoid bone located within the tendon of the flexor carpi ulnaris. It articulates only with the triquetral, making this its single articulation. Although situated superficially, it acts as a pulley to enhance FCU function. It plays no role in radiocarpal articulation and does not articulate with scaphoid, trapezium, or lunate.
1. Which carpal bone articulates with radius?
a) Pisiform
b) Hamate
c) Scaphoid
d) Triquetral
Explanation (Answer: c) Scaphoid)
The scaphoid articulates directly with the radius to form part of the radiocarpal joint. It plays a key role in wrist stability. Fractures of the scaphoid may compromise blood supply due to retrograde circulation, leading to avascular necrosis. The pisiform is not involved in radiocarpal articulation and lies anteriorly embedded in tendon.
2. Which carpal bone is most commonly fractured?
a) Lunate
b) Triquetral
c) Scaphoid
d) Pisiform
Explanation (Answer: c) Scaphoid)
The scaphoid is the most frequently fractured carpal bone, usually due to a fall on an outstretched hand. Tenderness in the anatomical snuffbox is the hallmark. Poor vascular supply makes the proximal segment prone to avascular necrosis. Pisiform rarely fractures because it is embedded within the FCU tendon and shielded.
3. A patient presents with carpal tunnel syndrome. Which bone forms the floor of the tunnel?
a) Pisiform
b) Scaphoid
c) Hamate
d) Lunate
Explanation (Answer: c) Hamate)
The hamate, along with the pisiform, hook of hamate, scaphoid, and trapezium, contributes to carpal tunnel boundaries. The floor is formed by concave arrangement of carpal bones including hamate and triquetral. Median nerve compression in this tunnel results in paresthesia in lateral digits, sparing the pisiform which lies outside the tunnel.
4. Which bone is located most medially in proximal carpal row?
a) Scaphoid
b) Lunate
c) Triquetral
d) Pisiform
Explanation (Answer: d) Pisiform)
The pisiform is the most medial carpal bone of the proximal row. Although situated anteriorly due to its sesamoid nature, it is anatomically aligned medially. It sits over the triquetral and provides leverage to FCU tendon. Its medial position is clinically significant in identifying ulnar nerve pathway through the Guyon canal.
5. Which ligament attaches to pisiform?
a) Flexor retinaculum
b) Pisohamate ligament
c) Intercarpal ligament
d) Scapholunate ligament
Explanation (Answer: b) Pisohamate ligament)
The pisohamate ligament extends from the pisiform to the hook of hamate and forms part of the roof of Guyon’s canal. This canal transmits the ulnar nerve and artery. Ligament injury may cause ulnar nerve irritation. Pisiform also serves as tendon attachment for FCU and gives origin to hypothenar muscles.
6. Which bone articulates with both scaphoid and triquetral?
a) Lunate
b) Pisiform
c) Hamate
d) Capitate
Explanation (Answer: a) Lunate)
The lunate articulates proximally with the radius and laterally with the scaphoid and medially with the triquetral. Its central position in proximal carpal row makes it vulnerable to dislocation. Lunate dislocation compresses median nerve. Pisiform does not articulate with scaphoid or lunate, only with triquetral.
7. Wrist drop occurs due to injury of which nerve?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation (Answer: c) Radial nerve)
Wrist drop results from radial nerve injury impairing extensor muscles. The pisiform’s articulation with triquetral remains unrelated. Radial nerve palsy leads to inability to extend wrist and MCP joints. Common causes include humeral shaft fractures and compression in axilla. Sensory loss occurs on dorsum of hand excluding fingertips.
8. Guyon's canal syndrome affects which nerve?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Axillary nerve
Explanation (Answer: b) Ulnar nerve)
Guyon’s canal, bounded by pisiform medially and hook of hamate laterally, transmits the ulnar nerve. Compression causes numbness in medial digits and intrinsic hand weakness. Pisiform’s anatomical location is clinically significant. Cyclists may develop “handlebar palsy” due to prolonged ulnar nerve compression here.
9. A boxer suffers fracture of hook of hamate. Which structure is endangered?
a) Radial artery
b) Ulnar nerve
c) Median nerve
d) Posterior interosseous nerve
Explanation (Answer: b) Ulnar nerve)
The hook of hamate, lateral boundary of Guyon’s canal, protects the ulnar nerve and artery. Fracture jeopardizes both, leading to sensory loss in medial hand and weakness of interossei. Although pisiform articulates with triquetral, its ligamentous connections involve the hamate, explaining biomechanical linkage in injury.
10. Pain over pisiform with wrist flexion indicates irritation of which muscle?
a) FCU
b) FCR
c) ECRL
d) ECRB
Explanation (Answer: a) FCU)
The flexor carpi ulnaris (FCU) tendon inserts onto the pisiform. Pain over pisiform during wrist flexion suggests FCU tendinopathy. Since pisiform acts as sesamoid bone enhancing FCU mechanics, inflammation or overuse directly causes localized tenderness. The pain is distinct from ulnar nerve neuropathy in Guyon’s canal.
Chapter: Anatomy; Topic: Abdomen – Spleen; Subtopic: Accessory Spleen (Spleniculi)
Keyword Definitions:
• Spleniculi (Accessory spleen): Congenital nodules of splenic tissue located outside the main spleen.
• Hilum of spleen: Site where splenic vessels enter/leave; common area for accessory spleens.
• Spleen: Lymphoid organ involved in filtration of blood and immune response.
• Gastrosplenic ligament: Ligament containing short gastric and left gastroepiploic vessels attached to spleen.
• Splenic hilum nodules: Localized accessory spleens near hilar region.
• Congenital anomaly: A developmental variation present from birth, such as accessory spleen.
Lead Question - 2015
Spleniculi are seen most commonly in:
a) Colon
b) Hilum
c) Liver
d) Lungs
Explanation (Answer: b) Hilum)
Spleniculi, also called accessory spleens, are most commonly found at the hilum of the spleen. They arise due to failure of fusion of splenic nodules during embryological development. They are functionally active and may hypertrophy after splenectomy. They are rarely seen near liver or colon and are never found in lungs. Their presence is important clinically when splenectomy is performed for hematologic disorders.
1. Accessory spleens are commonly found in which ligament?
a) Gastrosplenic ligament
b) Hepatoduodenal ligament
c) Omental bursa
d) Broad ligament
Explanation (Answer: a) Gastrosplenic ligament)
Accessory spleens frequently occur in the gastrosplenic ligament, second only to the splenic hilum. The ligament develops from dorsal mesogastrium and contains short gastric vessels. Spleniculi found here retain normal splenic tissue, immune function, and vascular supply. Identification during splenectomy is crucial to avoid recurrence of hematologic diseases.
2. An accessory spleen is usually:
a) Non-functional
b) Functional splenic tissue
c) Degenerated mass
d) Calcified organ
Explanation (Answer: b) Functional splenic tissue)
Accessory spleens are fully functional splenic tissues capable of normal immune and hematologic activity. They may enlarge when the main spleen is removed (splenectomy). Radiologically, they show uptake on Tc-99 scans. Their functionality is vital in understanding persistent disease after splenectomy for conditions like ITP or hereditary spherocytosis.
3. Which investigation is best to identify accessory spleen post-splenectomy?
a) Ultrasound
b) CT scan
c) Tc-99m sulfur colloid scan
d) MRI brain
Explanation (Answer: c) Tc-99m sulfur colloid scan)
Tc-99m sulfur colloid scan specifically highlights functional splenic tissue, making it ideal for locating accessory spleens. Accessory spleens may enlarge post-splenectomy, leading to recurrence of splenic disorders. CT and ultrasound may show nodules but cannot determine functional activity as accurately as radionuclide imaging.
4. Spleniculi are commonly associated with which condition?
a) Thoracic outlet syndrome
b) Splenectomy
c) Renal agenesis
d) Bronchiectasis
Explanation (Answer: b) Splenectomy)
Following splenectomy, accessory spleens often enlarge because they maintain residual splenic function. This may result in persistent symptoms in hematologic diseases. Knowledge of their presence helps surgeons perform complete removal when treating immune thrombocytopenia (ITP) or hemolytic disorders where splenic activity must be eliminated.
5. Where else besides hilum can accessory spleens be found?
a) In the scrotum
b) Within pancreatic tail
c) In the lungs
d) Inside gall bladder
Explanation (Answer: b) Within pancreatic tail)
Accessory spleens can occasionally be present in the pancreatic tail. They may mimic pancreatic masses radiologically. They demonstrate contrast enhancement similar to splenic tissue, helping radiologists differentiate them from tumors. Clinically, they may enlarge after splenectomy and continue disease progression if not recognized.
6. A surgeon finds a 1 cm mass near splenic hilum during splenectomy. What is it likely?
a) Splenic artery aneurysm
b) Lymph node
c) Accessory spleen
d) Pancreatic cyst
Explanation (Answer: c) Accessory spleen)
Small round nodules near the splenic hilum are most likely accessory spleens. They are congenital remnants containing normal splenic tissue. Failure to remove them in splenectomy may lead to persistence/recurrence of hematologic disorders. Their vascular supply branches from splenic artery, and they appear similar to main spleen histologically.
7. Accessory spleens originate from:
a) Endoderm
b) Mesoderm
c) Neural crest
d) Ectoderm
Explanation (Answer: b) Mesoderm)
The spleen and accessory spleens originate from mesoderm in dorsal mesogastrium. During development, splenic nodules fail to fuse, forming spleniculi. Their mesodermal origin explains their lymphoid function, reticular framework, and vascular pattern. They share structural and functional similarities with spleen proper.
8. Pain in left hypochondrium with persistent splenic tissue after splenectomy suggests presence of:
a) Liver cyst
b) Accessory spleen
c) Gastric diverticulum
d) Pancreatitis
Explanation (Answer: b) Accessory spleen)
Persistent splenic function after splenectomy indicates the presence of an accessory spleen. These spleniculi are normally asymptomatic but may present with abdominal discomfort when enlarged. They maintain immune function yielding ongoing sequestration of blood cells. Tc-99m scan confirms active splenic tissue postoperatively.
9. Which of the following is an ectopic accessory spleen site?
a) Pelvic cavity
b) Left iliac crest
c) Kidney cortex
d) Right lung apex
Explanation (Answer: a) Pelvic cavity)
Rarely, accessory spleens may migrate and be discovered in the pelvic cavity. They develop from mesoderm and are sometimes located along descending pathways of splenic tissue. These ectopic positions can complicate diagnosis of pelvic masses and influence surgical planning in persistent splenic diseases.
10. Accessory spleen may be confused radiologically with:
a) Pancreatic tail tumor
b) Hepatic hemangioma
c) Colon polyp
d) Lung nodule
Explanation (Answer: a) Pancreatic tail tumor)
An accessory spleen located in the pancreatic tail may mimic a pancreatic mass. Contrast-enhanced scans reveal enhancement patterns identical to splenic tissue. Recognizing this prevents unnecessary surgery. Functional imaging using Tc-99m confirms diagnosis, differentiating it from malignant pancreatic lesions or pseudocysts.
Chapter: Anatomy; Topic: Hepatobiliary System; Subtopic: Calot’s Triangle and Surgical Anatomy
Keyword Definitions:
• Calot’s triangle: Anatomical triangle bordered by cystic duct, common hepatic duct, and inferior liver surface.
• Cystic artery: Artery supplying the gallbladder usually found within Calot’s triangle.
• Lymph node of Lund: Node located within Calot’s triangle at the cystic duct–hepatic duct junction.
• Right hepatic artery: May course near or within Calot's triangle; variable anatomy.
• Portal vein: Major venous channel behind bile duct not entering Calot’s triangle.
• Cystic duct: Duct draining bile from gallbladder, forming a boundary of Calot’s triangle.
Lead Question - 2015
Structures passing through Calot's triangle are all EXCEPT:
a) Portal vein
b) Cystic artery
c) Right hepatic artery
d) Lymph node of Lund
Explanation (Answer: a) Portal vein)
The portal vein does not pass through Calot’s triangle. It lies posterior to the bile duct and hepatic artery within the hepatoduodenal ligament. Inside Calot’s triangle, the structures commonly found include the cystic artery, lymph node of Lund, and sometimes an aberrant right hepatic artery. Knowledge of this anatomy is crucial during cholecystectomy to prevent vascular injury.
1. The borders of Calot’s triangle include all EXCEPT:
a) Cystic duct
b) Common hepatic duct
c) Inferior surface of liver
d) Portal vein
Explanation (Answer: d) Portal vein)
The portal vein is not a boundary of Calot’s triangle. Its classical borders are the cystic duct, common hepatic duct, and inferior surface of liver. Understanding these borders helps in identifying surgical landmarks during cholecystectomy and avoiding vascular or ductal injury.
2. The cystic artery most commonly arises from:
a) Gastroduodenal artery
b) Right hepatic artery
c) Left hepatic artery
d) Portal vein
Explanation (Answer: b) Right hepatic artery)
The cystic artery typically originates from the right hepatic artery and travels within Calot’s triangle. Variations occur but this origin is most typical. Knowledge of its pathway is important during gallbladder removal to avoid hemorrhage and ensure proper ligation.
3. Which structure is typically NOT encountered during cholecystectomy dissection?
a) Portal vein
b) Cystic artery
c) Cystic duct
d) Lymph node of Lund
Explanation (Answer: a) Portal vein)
During cholecystectomy, portal vein is never directly dissected inside Calot’s triangle. Instead, surgeons usually identify cystic artery, cystic duct, and the lymph node of Lund. Portal vein lies posterior to the bile duct and hepatic artery within the hepatoduodenal ligament and is at risk only with deep dissection errors.
4. Which artery may show anatomical variation near Calot’s triangle?
a) Inferior phrenic artery
b) Right hepatic artery
c) Splenic artery
d) Left gastric artery
Explanation (Answer: b) Right hepatic artery)
The right hepatic artery often traverses Calot’s triangle or passes posterior to the common hepatic duct. Variant courses may complicate surgery. Injury leads to right hepatic lobe ischemia. Awareness of such variations helps prevent unintended ligation during gallbladder removal.
5. A surgeon notices enlarged lymph node at cystic duct–hepatic duct junction. This is:
a) Node of Rouviere
b) Lymph node of Lund
c) Parapancreatic node
d) Periportal node
Explanation (Answer: b) Lymph node of Lund)
The Lymph node of Lund, located within Calot’s triangle, may enlarge due to gallbladder inflammation or biliary diseases. It serves as a key anatomical landmark during cholecystectomy. Identification ensures safe dissection and correct clipping of cystic structures.
6. Which structure forms anterior wall of Calot’s triangle?
a) Cystic duct
b) Portal vein
c) Right hepatic duct
d) Gallbladder fundus
Explanation (Answer: a) Cystic duct)
The cystic duct forms the anterior boundary of Calot’s triangle. Identifying the cystic duct is crucial to achieve the "critical view of safety" during surgery. Misidentification may lead to clipping the common bile duct, causing serious postoperative complications.
7. Which structure lies posterior to Calot’s triangle?
a) Cystic artery
b) Portal vein
c) Left hepatic duct
d) Cystic node
Explanation (Answer: b) Portal vein)
The portal vein lies posterior to the bile duct and hepatic artery, outside Calot’s triangle. Visualization of its posterior position helps avoid deep dissection errors during cholecystectomy. Portal vein injury can cause catastrophic bleeding and must be protected during surgery.
8. Inflammation of structures in Calot’s triangle most likely occurs in:
a) Acute cholecystitis
b) Appendicitis
c) Pancreatitis
d) Renal colic
Explanation (Answer: a) Acute cholecystitis)
Acute cholecystitis causes inflammation around the gallbladder and cystic duct, affecting Calot’s triangle. Edema and fibrosis obscure the anatomy. This increases risk of bile duct injury during surgery. Accurate identification of cystic structures remains essential during acute cases.
9. Which structure is part of hepatoduodenal ligament along with bile duct and hepatic artery?
a) Portal vein
b) Cystic artery
c) Cystic duct
d) Lymph node of Lund
Explanation (Answer: a) Portal vein)
The portal vein is a key structure within the hepatoduodenal ligament, along with hepatic artery and bile duct. Although closely related, it lies posterior to Calot’s triangle and does not enter it. Its anatomy is essential for performing Pringle’s maneuver during trauma or bleeding control.
10. During laparoscopic cholecystectomy, which structure must be isolated within Calot’s triangle before clipping?
a) Right hepatic duct
b) Cystic duct
c) Portal vein
d) Left hepatic artery
Explanation (Answer: b) Cystic duct)
To achieve the critical view of safety, the cystic duct must be clearly identified and isolated within Calot’s triangle before clipping. Misidentification may result in clipping the common bile duct, leading to bile leak, strictures, or severe postoperative morbidity. Accurate dissection ensures safe surgery.
Chapter: Anatomy; Topic: Upper Limb – Axilla & Spaces; Subtopic: Quadrangular Space and Neurovascular Contents
Keyword Definitions:
• Quadrangular space: Anatomical space bordered by teres major, teres minor, long head of triceps, and humerus.
• Axillary nerve: Nerve supplying deltoid and teres minor passing through quadrangular space.
• Posterior circumflex humeral artery: Artery passing through quadrangular space supplying shoulder region.
• Teres minor: Superior boundary of quadrangular space, part of rotator cuff.
• Teres major: Inferior boundary of quadrangular space involved in arm adduction.
• Long head of triceps: Medial boundary of quadrangular space forming landmark for nerve passage.
Lead Question - 2015
What structure passes through the quadrangular space?
a) Axillary nerve
b) Radial nerve
c) Median nerve
d) Brachial artery
Explanation (Answer: a) Axillary nerve)
The axillary nerve passes through the quadrangular space along with the posterior circumflex humeral artery. It innervates the deltoid and teres minor muscles. The boundaries—teres minor above, teres major below, long head of triceps medially, and humerus laterally—define this space. Radial nerve and brachial artery do not pass through this region; they travel in different anatomical compartments.
1. Which artery accompanies the axillary nerve through the quadrangular space?
a) Anterior humeral circumflex artery
b) Radial artery
c) Posterior circumflex humeral artery
d) Deep brachial artery
Explanation (Answer: c) Posterior circumflex humeral artery)
The posterior circumflex humeral artery travels through the quadrangular space with the axillary nerve. It supplies the deltoid and shoulder joint. Its close relationship to the nerve explains why fractures of surgical neck of humerus can injure both the artery and axillary nerve. Radial and deep brachial arteries course elsewhere in the arm.
2. Injury to axillary nerve results in weakness of:
a) Elbow flexion
b) Shoulder abduction
c) Wrist extension
d) Finger adduction
Explanation (Answer: b) Shoulder abduction)
The axillary nerve innervates the deltoid muscle, which is responsible for shoulder abduction beyond 15 degrees. Injury leads to weakness in abduction, loss of deltoid contour, and numbness over lateral shoulder. It commonly occurs due to surgical neck fracture or dislocation. Other movements remain intact as their muscles are supplied by different nerves.
3. Which structure forms the medial border of quadrangular space?
a) Humerus
b) Long head of triceps
c) Teres major
d) Coracobrachialis
Explanation (Answer: b) Long head of triceps)
The long head of triceps forms the medial border of the quadrangular space. Laterally lies the humerus, superiorly teres minor, and inferiorly teres major. These boundaries are crucial during surgical exposure of axillary nerve. Understanding borders avoids iatrogenic nerve injury during deltoid or shoulder surgeries.
4. A patient with fracture of surgical neck of humerus most likely has injury to:
a) Radial nerve
b) Axillary nerve
c) Ulnar nerve
d) Musculocutaneous nerve
Explanation (Answer: b) Axillary nerve)
The axillary nerve winds around the surgical neck of humerus after passing through the quadrangular space. A fracture here easily injures the nerve and its accompanying posterior circumflex humeral artery. Symptoms include deltoid paralysis and sensory loss over shoulder. Radial nerve is more affected in mid-shaft humeral fractures.
5. Which muscle is NOT involved in forming the quadrangular space?
a) Teres major
b) Teres minor
c) Long head of triceps
d) Short head of biceps
Explanation (Answer: d) Short head of biceps)
The quadrangular space is formed by teres minor (superior), teres major (inferior), long head of triceps (medial), and humerus (lateral). Short head of biceps is located anteriorly in the arm and does not contribute to boundaries of this interval. Thus, it is not a structural component of the space.
6. A person with loss of cutaneous sensation over lateral shoulder likely has damage to:
a) Medial cutaneous nerve of arm
b) Axillary nerve
c) Radial nerve
d) Median nerve
Explanation (Answer: b) Axillary nerve)
The axillary nerve supplies the upper lateral cutaneous nerve of arm that provides sensation over the lateral shoulder. Injury produces numbness and deltoid weakness. This sensory deficit is clinically used to identify axillary nerve compression or injury. Median, radial, and ulnar nerves supply different regions of arm and forearm.
7. Axillary nerve damage may follow which type of shoulder dislocation?
a) Superior
b) Inferior
c) Posterior
d) Anterior
Explanation (Answer: d) Anterior)
Anterior shoulder dislocation is common and stretches or compresses the axillary nerve as it passes through the quadrangular space. This leads to deltoid muscle weakness and sensory loss. Posterior dislocations are less common. Inferior dislocations mostly affect brachial plexus roots rather than axillary nerve alone.
8. A tumor compressing structures in quadrangular space may affect:
a) Wrist extension
b) Forearm supination
c) Shoulder abduction
d) Finger extension
Explanation (Answer: c) Shoulder abduction)
Compression of quadrangular space affects the axillary nerve, impairing deltoid and teres minor function. This causes reduced shoulder abduction and difficulty lifting the arm. Wrist or finger functions remain intact because they are controlled by distal nerves such as radial and median nerves unaffected by compression in this region.
9. Which of the following can be palpated to assess axillary nerve function?
a) Deltoid contraction
b) Biceps tendon
c) Triceps tendon
d) Coracobrachialis contraction
Explanation (Answer: a) Deltoid contraction)
The deltoid muscle, supplied by the axillary nerve, can be palpated for contraction while the patient attempts shoulder abduction. Absence of contraction indicates nerve injury. This simple bedside assessment helps evaluate nerve integrity following humeral fractures or shoulder dislocations.
10. Which nerve passes through the triangular interval instead of quadrangular space?
a) Axillary nerve
b) Radial nerve
c) Median nerve
d) Ulnar nerve
Explanation (Answer: b) Radial nerve)
The radial nerve passes through the triangular interval along with deep brachial artery, not through quadrangular space. The triangular interval is bordered by long head of triceps, lateral head of triceps, and teres major. This anatomical separation explains why radial nerve injuries are associated with mid-shaft humerus fractures rather than shoulder injuries.
Chapter: Anatomy; Topic: Male Reproductive System; Subtopic: Structures of Prostatic Urethra
Keyword Definitions:
• Seminal colliculus: Elevation on posterior wall of prostatic urethra where ejaculatory ducts open.
• Prostatic urethra: Portion of urethra passing through prostate containing urethral crest.
• Ejaculatory ducts: Ducts opening into prostatic urethra formed by union of vas deferens and seminal vesicle duct.
• Prostate gland: Gland surrounding prostatic urethra producing seminal fluid.
• Urethral crest: Ridge containing seminal colliculus in prostatic urethra.
• Prostatic sinuses: Lateral depressions where prostatic ducts open into urethra.
Lead Question - 2015
Seminal colliculus is present in?
a) Testis
b) Prostate
c) Urethra
d) Scrotum
Explanation (Answer: c) Urethra)
The seminal colliculus is a prominent elevation located in the prostatic urethra along the urethral crest. It is the site where the ejaculatory ducts open, marking a key anatomical landmark during endoscopic urological procedures. Though situated within the prostate, it specifically belongs to the urethra. It contains the prostatic utricle opening as well and plays an essential role in the male reproductive tract.
1. Ejaculatory ducts open into which structure?
a) Membranous urethra
b) Prostatic urethra
c) Spongy urethra
d) Bladder neck
Explanation (Answer: b) Prostatic urethra)
The ejaculatory ducts open into the prostatic urethra at the seminal colliculus. This region also contains prostatic utricle opening. The prostatic urethra serves as a pathway for semen to join urinary flow. Any obstruction here can affect ejaculation or cause retention. Its anatomy is essential during TURP procedures and cystoscopies.
2. Prostatic utricle is associated with:
a) Seminal colliculus
b) Bladder trigone
c) Epididymis
d) Seminal vesicle
Explanation (Answer: a) Seminal colliculus)
The prostatic utricle is a small pouch opening into the seminal colliculus. It represents a remnant of the Müllerian duct. Though small, it may become enlarged in persistent Müllerian duct syndrome. Its opening lies between entrances of ejaculatory ducts and is visible during cystoscopy as part of urethral crest structures.
3. Which part of urethra passes through prostate?
a) Membranous urethra
b) Prostatic urethra
c) Spongy urethra
d) Penile urethra
Explanation (Answer: b) Prostatic urethra)
The prostatic urethra runs through the prostate gland and contains key landmarks like the urethral crest, seminal colliculus, and prostatic sinuses. It receives ejaculatory ducts and prostatic secretions. If enlarged prostate compresses this region, urinary obstruction and retention may occur, commonly seen in elderly males with BPH.
4. Enlargement of which gland leads to compression of prostatic urethra?
a) Seminal vesicle
b) Prostate
c) Bulbourethral gland
d) Parotid
Explanation (Answer: b) Prostate)
The prostatic urethra is enclosed by the prostate. In benign prostatic hyperplasia (BPH), enlargement of prostate compresses urethra causing urinary obstruction, hesitancy, and weak stream. Since seminal colliculus lies here, it may be distorted during adenoma expansion. TURP surgery targets this region for symptomatic relief.
5. Which structure is NOT part of prostatic urethra?
a) Prostatic sinus
b) Seminal colliculus
c) Bulbourethral duct opening
d) Prostatic utricle
Explanation (Answer: c) Bulbourethral duct opening)
Bulbourethral ducts open into the spongy urethra, not into the prostatic urethra. The prostatic urethra contains prostatic sinuses, seminal colliculus, and prostatic utricle. These structures are important in urological evaluation and drainage of prostatic secretions into the urethral lumen.
6. Seminal colliculus is located on:
a) Anterior urethral wall
b) Posterior urethral wall
c) Lateral urethral wall
d) Floor of urethra
Explanation (Answer: b) Posterior urethral wall)
The seminal colliculus forms a raised elevation on the posterior wall of the prostatic urethra, part of the urethral crest. This location is essential for understanding cystoscopic landmarks. It also receives openings of ejaculatory ducts—one on each side of prostatic utricle, aiding semen entry into urethral passage.
7. Pain during ejaculation may result from obstruction at:
a) Membranous urethra
b) Seminal colliculus
c) External urethral meatus
d) Perineal urethra
Explanation (Answer: b) Seminal colliculus)
Obstruction or inflammation around the seminal colliculus may impede ejaculatory duct entry into urethra, causing painful ejaculation. Chronic prostatitis may lead to swelling of this region. Blockage affects emission pathway leading to discomfort. Cystoscopy may reveal mucosal elevation or stenosis around this anatomical landmark.
8. Prostatic urethra receives prostatic ducts into:
a) Seminal colliculus
b) Prostatic sinuses
c) Prostatic utricle
d) Ejaculatory ducts
Explanation (Answer: b) Prostatic sinuses)
Prostatic ducts drain into prostatic sinuses, which are depressions on either side of the urethral crest in the prostatic urethra. Seminal colliculus mainly receives ejaculatory ducts and prostatic utricle opening. Understanding duct openings aids in diagnosing reflux, infections, or obstruction-related disorders in male reproductive anatomy.
9. Seminal colliculus is also referred to as:
a) Adam’s ridge
b) Verumontanum
c) Prostatic fossa
d) Seminal pit
Explanation (Answer: b) Verumontanum)
Verumontanum is the alternate name for the seminal colliculus. It is an important cystoscopic landmark inside the prostatic urethra. The ejaculatory ducts open here, appearing as paired openings. It helps clinicians orient themselves during urological procedures such as TURP, preventing inadvertent damage to vital reproductive structures.
10. A boy with midline cystic swelling in prostatic urethra likely has dilation of:
a) Ejaculatory ducts
b) Prostatic utricle
c) Urethral glands
d) Bulbourethral duct
Explanation (Answer: b) Prostatic utricle)
A dilated prostatic utricle appears as a midline cystic structure during evaluation of prostatic urethra. It opens at the seminal colliculus. Congenital enlargement can cause urinary tract symptoms or infection. Utricular cysts are associated with hypospadias and persistent Müllerian duct syndrome, requiring follow-up imaging and possible intervention.
Chapter: Embryology; Topic: Development of Gastrointestinal Tract; Subtopic: Foregut Derivatives
Keyword Definitions:
• Foregut: Portion of primitive gut tube forming pharynx, esophagus, stomach, upper duodenum, liver, pancreas.
• Midgut: Part of primitive gut forming distal duodenum, jejunum, ileum, cecum, appendix, ascending colon, proximal transverse colon.
• Hindgut: Part of primitive gut forming distal transverse colon, descending colon, sigmoid colon, rectum, anal canal above pectinate line.
• Pancreas: Foregut derivative formed by dorsal and ventral buds.
• Liver: Foregut derivative forming hepatic diverticulum.
• Cecum: Dilatation of midgut loop forming cecum and appendix.
Lead Question - 2015
Which of the following is not a derivative of foregut?
a) Cecum
b) Duodenum
c) Liver
d) Pancreas
Explanation (Answer: a) Cecum)
The cecum is a midgut derivative, not a foregut derivative. The foregut gives rise to esophagus, stomach, liver, pancreas, and upper half of duodenum. The cecum originates from the midgut loop and forms the base for the appendix. The liver and pancreas arise from foregut endoderm and play chief roles in digestive enzyme regulation and metabolism.
1. Which of the following structures develops from midgut?
a) Stomach
b) Cecum
c) Gallbladder
d) Pancreatic duct
Explanation (Answer: b) Cecum)
The cecum is derived from the midgut as part of the midgut loop. It develops as an outpouching at the junction of ileum and colon. The stomach, gallbladder, and pancreatic ducts arise from foregut endoderm. Midgut structures include ileum, appendix, ascending colon, and proximal transverse colon. Rotation abnormalities affect cecum position clinically.
2. Which organ originates from hepatic diverticulum?
a) Spleen
b) Liver
c) Kidney
d) Appendix
Explanation (Answer: b) Liver)
The liver develops from the hepatic diverticulum, a foregut endodermal outgrowth. It invades septum transversum forming hepatocytes, bile ducts, and intrahepatic structures. The spleen arises from mesoderm of dorsal mesogastrium, not gut tube. Kidney develops from intermediate mesoderm while appendix originates from midgut-derived cecum.
3. The pancreas develops from:
a) Hindgut
b) Mesoderm
c) Foregut
d) Ectoderm
Explanation (Answer: c) Foregut)
The pancreas forms from dorsal and ventral pancreatic buds arising from the foregut endoderm. These buds fuse to form head, body, and tail. Pancreatic duct anomalies occur due to improper fusion producing pancreas divisum. Insulin-producing beta cells originate from endodermal lineage, not mesoderm or ectoderm, confirming foregut derivation.
4. Lower half of duodenum develops from:
a) Foregut
b) Midgut
c) Hindgut
d) Allantois
Explanation (Answer: b) Midgut)
The lower half of duodenum and proximal jejunum come from midgut. The upper half is from foregut, receiving bile and pancreatic ducts. Knowing the origin helps understand blood supply division—foregut supplied by celiac artery and midgut by superior mesenteric artery, explaining mixed vascular patterns in duodenum.
5. Which artery supplies foregut derivatives?
a) Inferior mesenteric artery
b) Superior mesenteric artery
c) Celiac artery
d) Renal artery
Explanation (Answer: c) Celiac artery)
Foregut organs, including stomach, liver, pancreas, spleen (via splenic branch), are supplied by the celiac artery. This arterial trunk branches into left gastric, splenic, and common hepatic arteries. Superior mesenteric supplies midgut while inferior mesenteric supplies hindgut. Knowledge of embryology guides vascular surgical approaches.
6. A newborn with annular pancreas has obstruction due to abnormal rotation of:
a) Dorsal pancreatic bud
b) Ventral pancreatic bud
c) Hepatic diverticulum
d) Midgut loop
Explanation (Answer: b) Ventral pancreatic bud)
Annular pancreas occurs due to abnormal migration of the ventral pancreatic bud encircling duodenum, causing obstruction. The bud encases the second part of duodenum. Symptoms include vomiting and gastric distension in neonates. It is a foregut developmental anomaly involving pancreatic rotation failure.
7. Failure of recanalization of duodenum leads to:
a) Duodenal atresia
b) Hirschsprung disease
c) Omphalocele
d) Pyloric stenosis
Explanation (Answer: a) Duodenal atresia)
Duodenal atresia results from failure of recanalization of duodenal lumen during development. Presents with bilious vomiting and “double bubble” sign on X-ray. It involves both foregut- and midgut-derived portions. Associated with Down syndrome. Treatment requires surgical correction to restore intestinal continuity.
8. Cecum is supplied by which artery?
a) Celiac trunk
b) Middle colic artery
c) Ileocolic artery
d) Inferior mesenteric artery
Explanation (Answer: c) Ileocolic artery)
The cecum, as a midgut derivative, is supplied by the ileocolic artery, a branch of superior mesenteric artery. Blood supply pattern reflects embryonic origin. Midgut ischemia or volvulus may compromise this region. The celiac trunk supplies foregut organs and not cecum, confirming its separate developmental lineage.
9. Which of the following is derived from midgut but supplied by celiac trunk?
a) Appendix
b) Duodenum (lower half)
c) Jejunum
d) None
Explanation (Answer: d) None)
Foregut derivatives are supplied by celiac trunk while midgut derivatives by superior mesenteric artery. No midgut structure receives major supply from celiac trunk. Duodenum transitions at papilla; proximal is foregut-supplied, distal is midgut-supplied. Appendix, jejunum, and transverse colon derive from midgut and are SMA-dependent.
10. A neonate with bilious vomiting and polyhydramnios likely has obstruction at:
a) Pylorus
b) Duodenum
c) Rectum
d) Cecum
Explanation (Answer: b) Duodenum)
Duodenal obstruction due to atresia or annular pancreas (both involving foregut structures) causes bilious vomiting and polyhydramnios. The “double bubble” sign on radiograph indicates dilation of stomach and proximal duodenum. Cecum obstruction typically causes distal bowel symptoms, not bilious vomiting. Early surgical repair is essential.
Chapter: Physiology; Topic: Cell Membrane Physiology; Subtopic: Mechanisms of Membrane Transport
Keyword Definitions:
• Concentration gradient: Difference in solute concentration across a membrane driving passive transport.
• Membrane permeability: Ability of membrane to allow specific substances to pass through.
• Passive transport: Movement of substances without ATP, dependent on gradient and membrane properties.
• Charge of particle: Determines how ions interact with membrane channels and electrochemical gradients.
• Membrane thickness: Affects diffusion rate inversely according to Fick’s law.
• Particle size: Influences diffusion speed; smaller particles cross faster in simple diffusion.
Lead Question - 2015
Most important factor in transport across a membrane?
a) Charge of particle
b) Membrane thickness
c) Size of particle
d) Concentration gradient
Explanation (Answer: d) Concentration gradient)
The concentration gradient is the primary factor influencing passive transport across a membrane. When the gradient is steep, movement of molecules occurs rapidly from high concentration to low concentration. While particle size, charge, and membrane thickness influence permeability, diffusion relies most strongly on gradient magnitude. Fick’s law mathematically supports this dominance in biological membrane transport.
1. Simple diffusion depends primarily on:
a) ATP energy
b) Concentration gradient
c) DNA content
d) tRNA availability
Explanation (Answer: b) Concentration gradient)
Simple diffusion requires no ATP and occurs when a concentration gradient drives molecules from high to low concentration. The steeper the gradient, the faster the diffusion. Temperature, membrane surface area, and particle size play secondary roles. DNA or tRNA have no direct involvement. Diffusion continues until equilibrium is reached in the cell.
2. Ions cross the cell membrane mainly through:
a) Lipid bilayer
b) Protein channels
c) Nucleus
d) Lysosomes
Explanation (Answer: b) Protein channels)
Charged ions cannot penetrate lipid bilayers easily; they require protein channels or transporters. Ion channels control movement according to electrochemical gradients. Sodium, potassium, calcium, and chloride flow through selective channels. The lipid bilayer blocks charged molecules, making channels vital in nerve conduction and muscle depolarization.
3. According to Fick’s law, rate of diffusion decreases if:
a) Surface area increases
b) Membrane thickness increases
c) Concentration gradient increases
d) Membrane permeability increases
Explanation (Answer: b) Membrane thickness increases)
Fick’s law states diffusion rate varies directly with surface area and concentration gradient and inversely with membrane thickness. Thicker membranes slow diffusion because molecules travel a longer distance. This principle explains delayed gas exchange in pulmonary fibrosis where thickened alveolar membranes impair oxygen diffusion.
4. Facilitated diffusion differs from simple diffusion in that it:
a) Requires ATP
b) Uses carrier proteins
c) Moves against gradient
d) Stops at equilibrium
Explanation (Answer: b) Uses carrier proteins)
Facilitated diffusion uses carrier proteins or channel proteins to transport large or charged molecules along concentration gradients. It does not require ATP, unlike active transport. It saturates when carrier proteins are fully occupied. The process halts at equilibrium just like simple diffusion, distinguishing it from pump-driven active transport.
5. The most important determinant of ion movement through membrane is the:
a) Proton gradient
b) Electrochemical gradient
c) Hydration status
d) Gene expression
Explanation (Answer: b) Electrochemical gradient)
Ions cross membranes based on electrochemical gradients, consisting of two components—concentration gradient and electrical potential difference. Both influence ion direction and speed. Sodium entry during depolarization, potassium efflux during repolarization, and calcium influx in muscle contraction are all driven by this combined force.
6. A patient with pulmonary fibrosis has reduced oxygen diffusion due to:
a) Increased membrane thickness
b) Lower oxygen solubility
c) Increased surface area
d) Increased gradient
Explanation (Answer: a) Increased membrane thickness)
Pulmonary fibrosis thickens alveolar-capillary membranes, thereby reducing diffusion rate according to Fick’s law. Even with high oxygen concentration gradient, transfer is impaired because diffusion distance increases. Resulting symptoms include hypoxia, dyspnea, and reduced oxygen saturation. Treatment aims to reduce inflammation and improve effective lung surface area.
7. Glucose enters muscle cells via:
a) Simple diffusion
b) Facilitated diffusion
c) Osmosis
d) Active transport pump
Explanation (Answer: b) Facilitated diffusion)
Glucose entry into muscle occurs through GLUT-4 transporters, which perform facilitated diffusion. Insulin stimulates transporter translocation to membrane. Once gradient exists, glucose moves down gradient without ATP. In insulin resistance, GLUT-4 fails to respond, impairing glucose uptake and causing hyperglycemia characteristic of type 2 diabetes.
8. Increasing membrane permeability will:
a) Increase rate of diffusion
b) Decrease concentration gradient
c) Stop particle movement
d) Block osmosis
Explanation (Answer: a) Increase rate of diffusion)
Higher membrane permeability increases diffusion because membrane offers less resistance. Permeability is influenced by lipid solubility, channel availability, and membrane composition. Lipophilic molecules diffuse rapidly while hydrophilic molecules require channels or carriers. Gradients still determine direction and magnitude of net flow.
9. Which process requires ATP to move molecules against gradient?
a) Osmosis
b) Simple diffusion
c) Facilitated diffusion
d) Active transport
Explanation (Answer: d) Active transport)
Active transport consumes ATP to move substances against their concentration gradient. The sodium-potassium pump is the classic example, exchanging 3 sodium ions out and 2 potassium ions in. This maintains membrane potential and cellular homeostasis. Other processes—osmosis, simple diffusion, and facilitated diffusion—do not use energy.
10. Water crosses the cell membrane mainly by:
a) Sodium channels
b) Aquaporins
c) Lysosomes
d) Mitochondria
Explanation (Answer: b) Aquaporins)
Water transport mostly occurs through specialized channels called aquaporins. These protein channels allow rapid water movement following osmotic gradients. Aquaporin defects cause disorders like nephrogenic diabetes insipidus. Passive osmotic movement continues until equilibrium is reached. Their function highlights importance of gradient-driven membrane transport.