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ANSWERS: Abdomen & Pelvis - Anatomy (I MBBS)

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PAPER 1 (2026) ANSWERS

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Q1. Describe the Uterus

a. Position and Presenting Parts (2 marks)

• Fundus - rounded superior part above the uterine tubes
• Body - main part; flattened anteroposteriorly; has anterior (vesical) and posterior (intestinal) surfaces
• Isthmus - narrow constriction between body and cervix (~1 cm); becomes the lower uterine segment during pregnancy
• Cervix - cylindrical lower part, partly in pelvis (supravaginal) and partly in vagina (vaginal part); has an external os and internal os

b. Relations (3 marks)

• Vesicouterine pouch separates the body from the bladder
• Supravaginal cervix is related to the base of the bladder
• Ureter runs close to the lateral fornix of vagina (~2 cm from cervix)

• Rectouterine pouch (Pouch of Douglas) - deepest part of peritoneal cavity; contains small intestine and sigmoid colon
• Rectum

• Broad ligaments containing uterine vessels
• Ureters pass below uterine arteries ("water under the bridge")
• Uterine vessels and ovarian vessels

c. Supports (3 marks)

d. Development (2 marks)

• At ~6th week, paramesonephric ducts form lateral to mesonephric ducts
• They descend, cross the mesonephric ducts, and fuse in the midline
• The fused caudal portions form the uterovaginal canal (becomes uterus + upper vagina)
• The unfused cranial portions become the uterine tubes
• The proliferating epithelium from the fused ducts forms the sinovaginal bulbs, which produce the vaginal plate; this canalizes to form the lower vagina
• The muscular wall (myometrium) and peritoneal covering develop from surrounding mesenchyme

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Q2. Undescended Testis vs. Ectopic Testis; Descent Timeline

Embryological Basis (1 mark)

• The testis develops retroperitoneally from the genital ridge at ~L1 vertebral level
• It is guided by the gubernaculum, a ligament connecting the testis to the scrotal swelling
• Undescended testis (cryptorchidism): The testis has failed to complete its normal path along the inguinal canal into the scrotum. It is arrested somewhere along the normal path (abdominal, inguinal canal, or at the superficial inguinal ring)
• Ectopic testis: The testis has completed descent through the inguinal canal but has deviated from the normal path and lies in an abnormal location (perineal, femoral triangle, superficial inguinal pouch, root of penis, or contralateral scrotum)

Difference (2 marks)

Timeline and Factors for Testicular Descent (2 marks)

• 7th-8th month intrauterine: Testis descends from abdomen through inguinal canal
• At term: Most testes are in scrotum
• 3 months postnatal: Remaining cases may descend spontaneously

1. Gubernaculum testis - primary guide; undergoes swelling and regression
2. Androgens (testosterone, DHT) - essential for inguinoscrotal phase
3. INSL3 (insulin-like factor 3) from Leydig cells - controls transabdominal phase
4. Genitofemoral nerve - releases CGRP which guides gubernacular swelling
5. Intra-abdominal pressure - helps push testis through inguinal canal
6. Growth differential - backbone grows faster than gubernaculum, pulling testis down

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Q3. Anterior and Posterior Relations of the Right Kidney

Anterior Relations (3 marks)

• Right lobe of liver (peritoneum present) - hepatorenal pouch (Rutherford Morison's pouch) separates them
• Second part of duodenum (no peritoneum) - medially

• Right colic flexure (hepatic flexure) - inferolaterally
• Small intestine / loops of jejunum (with peritoneum)

Posterior Relations (2 marks)

• Diaphragm - upper pole (12th rib lies posterior)
• Quadratus lumborum muscle - the main posterior relation; the kidney lies on its anterior surface
• Psoas major muscle - medially
• Transversus abdominis muscle - lateral edge
• Subcostal nerve (T12), iliohypogastric nerve (L1), and ilioinguinal nerve (L1) - pass posterior to the kidney on quadratus lumborum
• 12th rib crosses the posterior surface

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Q4. Boundaries and Contents of the Ischiorectal (Ischioanal) Fossa

Boundaries

Contents

1. Pudendal nerve (S2, S3, S4) and its branches (inferior rectal nerve, perineal nerve, dorsal nerve of penis/clitoris) - run in pudendal canal on lateral wall
2. Internal pudendal artery and vein - in pudendal canal
3. Inferior rectal nerve and vessels - cross the fossa to supply anal canal and external sphincter
4. Perineal branch of S4
5. Fat - large amount fills the fossa; allows distension of anal canal during defecation
6. Lymphatics

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Q5. Three Sites of Portocaval Anastomosis

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Q6. Pain in Appendicitis - Periumbilical then Right Iliac Fossa (1+2=3)

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Q7. Boundaries of the Epiploic Foramen (Foramen of Winslow)

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Q8. Structures in Posterior Wall of Stomach (Posterior to Lesser Sac) - 6 structures

1. Pancreas (body and tail) - most commonly injured
2. Left kidney and suprarenal gland
3. Splenic artery (running along upper border of pancreas)
4. Aorta / coeliac trunk and its branches
5. Transverse colon / transverse mesocolon
6. Spleen (via gastrosplenic ligament)
7. Diaphragm (left crus - upper part of stomach bed)

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Q9. Histology of the Duodenum (Labelled Diagram)

• Brunner's glands (submucosal glands) - ONLY in duodenum; secrete alkaline mucus to neutralize acid chyme
• Villi - broad and leaf-shaped (compared to finger-shaped in jejunum)
• Crypts of Lieberkuhn (intestinal glands)
• Goblet cells
• Paneth cells (at base of crypts)
• Plica circulares (kerckring's folds) - absent in 1st part, present from 2nd part onwards

1. Mucosa: Epithelium (simple columnar + goblet cells) → Lamina propria → Muscularis mucosae
2. Submucosa: Contains Brunner's glands and Meissner's (submucosal) plexus
3. Muscularis externa: Inner circular + outer longitudinal layers + Auerbach's (myenteric) plexus between them
4. Serosa (adventitia in 2nd-4th parts as they are retroperitoneal)

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PAPER 2 (2025) ANSWERS

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Q1. Portal Circulation and Portocaval Anastomosis (1+3+3+3=10)

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Q2. Anatomical Supports Preventing Uterine Prolapse

• Transverse cervical (cardinal / Mackenrodt's) ligament - most important; runs from cervix and upper vagina to lateral pelvic walls; prevents descent
• Uterosacral ligaments - from cervix to sacrum (S2-S4); prevent anterior displacement and maintain anteflexion

• Pubocervical ligament - from cervix to pubis; prevents posterior descent

• Levator ani muscle (pelvic diaphragm) - the primary muscular platform; especially puborectalis; weakened by childbirth
• Perineal body - fibromuscular node in perineum; damage in delivery weakens pelvic floor

• Broad ligament (bilateral peritoneal folds)
• Round ligament (maintains anteversion; weak)

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Q3. Turner Syndrome (45, X) - Chromosomal Aberration (0.5+0.5+4=5)

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Q4. Internal Features of the Anal Canal

1. Anal columns (columns of Morgagni): 6-10 longitudinal folds in upper half; contain branches of superior rectal vessels; merge inferiorly at the pectinate line
2. Anal sinuses: Depressions between anal columns; contain anal glands that open here; can become infected (perianal abscess)
3. Anal valves: Crescentic mucosal folds connecting bases of adjacent anal columns
4. Pectinate (dentate) line: Formed by anal valves; marks cloacal membrane position; key landmark separating upper and lower anal canal:

1. Anal pecten: Zone between pectinate line and white line; lined by nonkeratinized stratified squamous epithelium; contains internal hemorrhoidal plexus
2. Anocutaneous line (White line of Hilton): Junction between anal canal skin and perianal skin; marks lower border of internal sphincter

• Internal anal sphincter: Thickening of circular smooth muscle; involuntary; controlled by ANS; tone maintained by sympathetics (hypogastric nerve)
• External anal sphincter: Skeletal muscle; voluntary; innervated by inferior rectal branch of pudendal nerve (S2,3,4)

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Q5. Parts and Peritoneal/Visceral Relations of Stomach (1+2+2=5)

Parts:

1. Cardia - surrounds cardiac orifice (gastroesophageal junction)
2. Fundus - dome-shaped part above cardiac notch; related to left dome of diaphragm
3. Body - main part between fundus and pyloric antrum
4. Pyloric part - includes pyloric antrum and pyloric canal; ends at pylorus (gastroduodenal junction, L1 vertebra)

Peritoneal Relations:

• Stomach is entirely intraperitoneal
• Lesser omentum (hepatogastric ligament) connects lesser curvature to liver
• Greater omentum hangs from greater curvature
• Gastrosplenic ligament connects greater curvature to spleen (contains short gastric and left gastroepiploic vessels)
• Gastrophrenic ligament connects fundus to diaphragm

Visceral (Anatomical) Relations:

• Left lobe of liver and gallbladder (contact)
• Anterior abdominal wall (when stomach is full)
• Left costal margin and ribs 7-9 (body)
• Left dome of diaphragm (fundus)

• Left kidney and suprarenal gland
• Splenic artery
• Body and tail of pancreas
• Spleen
• Transverse colon and transverse mesocolon
• Left dome of diaphragm (fundus)

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Q6. McBurney's Point and Appendix Positions (1+1+3=5)

1. Retrocaecal / retroileal (most common, ~65-75%) - behind caecum; may give atypical presentation (psoas sign)
2. Pelvic / descending - hangs into true pelvis; may mimic pelvic pathology
3. Postileal - behind terminal ileum
4. Preileal (subcaecal) - in front of terminal ileum
5. Paracaecal - medial to caecum
6. Subhepatic - near liver (rare; occurs if caecum fails to descend)

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Q7. Boundaries and Contents of Ischiorectal Fossa

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Q8. Coverings of Kidney and Renal Fascia (2+3=5)

Coverings (from inside out):

1. True capsule (fibrous capsule) - thin, fibrous; strips easily from healthy kidney; adherent in chronic disease (e.g., pyelonephritis)
2. Perinephric fat (adipose capsule) - abundant fat surrounding kidney; provides cushioning
3. Renal fascia (Gerota's fascia) - dense connective tissue investing kidney and suprarenal gland
4. Paranephric fat (pararenal fat) - external to renal fascia; more on posterior aspect

Renal Fascia in Detail:

• The renal fascia is a condensation of the extraperitoneal (retroperitoneal) connective tissue
• It encloses the kidney, suprarenal gland, and perirenal fat
• Has anterior layer (Toldt's fascia - continuous with posterior peritoneum) and posterior layer (Zuckerkandl's fascia)
• Superiorly: Two layers fuse above the suprarenal gland, attached to diaphragm
• Inferiorly: The layers do NOT fuse below (open inferiorly); this is clinically important - a perinephric abscess can track downward into the pelvis; a pelvic kidney can "herniate" upward in pregnancy
• Medially: Anterior layer blends with connective tissue around aorta/IVC; posterior layer attaches to vertebral fascia
• Laterally: Two layers fuse to form the lateroconal fascia (continuous with peritoneum laterally)
• Clinical significance: Perirenal collections are limited by this fascia; also important in renal transplantation and retroperitoneal surgery

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Q9. 10 Differences Between Male and Female Bony Pelvis

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Q10. Karyotyping (4+1=5)

1. Sample collection - blood (peripheral lymphocytes), amniotic fluid (amniocentesis), chorionic villi (CVS), bone marrow
2. Cell culture - cells grown in tissue culture medium; PHA (phytohemagglutinin) added to stimulate lymphocyte division
3. Arrest at metaphase - colchicine (colcemid) added to arrest mitosis at metaphase (chromosomes maximally condensed)
4. Hypotonic treatment - cells placed in hypotonic solution (0.075M KCl) to swell cells and spread chromosomes
5. Fixation - Carnoy's fixative (methanol:acetic acid 3:1) to fix chromosomes
6. Spreading - cells dropped onto slides; cells burst releasing chromosomes
7. Staining - G-banding (Giemsa stain after trypsin treatment); produces characteristic dark/light band pattern unique to each chromosome
8. Photography and analysis - photographs taken; chromosomes cut out and arranged in pairs (autosomes 1-22, then sex chromosomes) = karyogram
9. Computer-aided analysis - modern automated karyotyping using imaging software

1. Down syndrome - Trisomy 21 (47, +21) or Robertsonian translocation (46, der(14;21))
2. Turner syndrome - Monosomy X (45, X)

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Q11. Trigone of Urinary Bladder and Nerve Supply (3+2=5)

Trigone:

• A smooth, triangular area on the posterior internal surface of the bladder
• Bounded by the two ureteric orifices (posterosuperiorly) and the internal urethral orifice (anteroinferiorly)
• Unlike the rest of the bladder, the trigone is smooth (not rugose) because the mucosa is firmly adherent to the underlying muscle
• The interureteric ridge (Mercier's bar) connects the two ureteric orifices - a useful cystoscopic landmark
• Clinical significance: The trigone is most sensitive to pain and is the most common site of bladder pathology (infections, tumors, obstruction in BPH)

Nerve Supply of Bladder:

• Pelvic splanchnic nerves (nervi erigentes) - S2, S3, S4
• Promotes voiding (contraction of detrusor, relaxation of internal sphincter)

• Hypogastric nerve (L1, L2) from inferior hypogastric plexus
• Promotes storage (relaxation of detrusor, contraction of internal sphincter)

• Pudendal nerve (S2, S3, S4) - inferior rectal and perineal branches
• Voluntary control of micturition

• Pelvic splanchnic nerves carry pain and fullness sensation from bladder body
• Hypogastric nerves carry sensation from trigone and bladder neck

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Q12. Direct vs. Indirect Inguinal Hernia (3 differences)

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Q13. Three Intrinsic Coverings of Testis

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Q14. Enlarged Prostate - Per Rectal Examination (1+2=3)

• The prostate gland lies directly anterior to the rectum, separated only by the fascial layer (Denonvilliers' fascia / rectovesical septum) - approximately 2-3 mm of tissue
• On per rectal examination, the examiner inserts a gloved, lubricated index finger into the rectum and can palpate the posterior surface of the prostate anteriorly
• Normally the prostate feels like a firm, rubbery, bilobed structure with a median sulcus
• In BPH (benign prostatic hyperplasia): Enlarged, smooth, rubbery, median sulcus may be lost
• In carcinoma: Hard, craggy, irregular, median sulcus obliterated
• Normally only the posterior lobe (peripheral zone) is palpable; the median/lateral lobes causing urinary obstruction in BPH may not be directly palpable but the overall size can be estimated

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Q15. Boundaries of Urogenital Triangle

• Anteriorly (apex): Pubic symphysis
• Laterally: Ischiopubic rami (on each side)
• Base (posteriorly): An imaginary line between the two ischial tuberosities
• Floor: Perineal membrane (inferior fascia of urogenital diaphragm) and deep perineal pouch structures

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Q16. Autosomal Recessive Disorders Skip Generations (with Pedigree)

Generation I:   ○----□      (Both unaffected = Aa carriers)
                
Generation II:  □  ○  ■  ○    (1/4 affected, 2/4 carriers, 1/4 normal)
                         ↑
                      Affected (aa)

Generation III: If affected (aa) × normal (AA): All Aa (carriers, unaffected)
                                  → skips generation III clinically

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PAPER 3 (2024 REMEDIAL) ANSWERS

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Q1. Hip Joint

a. Type and Articulating Surfaces (2 marks)

• Type: Synovial joint - ball and socket (enarthrodial) joint
• Articulating surfaces:
  • Ball: Head of femur (2/3 of a sphere); covered with hyaline cartilage except at the fovea capitis (where ligamentum teres attaches)
  • Socket: Acetabulum of the hip bone (formed by ilium + ischium + pubis); deepened by the fibrocartilaginous acetabular labrum; the articular surface (lunate surface) is horseshoe-shaped; the acetabular notch is bridged by the transverse acetabular ligament; the non-articular floor (acetabular fossa) contains fibrofatty tissue and acetabular vessels

b. Ligaments (3 marks)

c. Movements and Muscles Responsible (4 marks)

d. Clinical Anatomy (1 mark)

• Avascular necrosis (AVN) of femoral head: The blood supply to the femoral head in adults comes mainly from the medial circumflex femoral artery via retinacular arteries; posterior femoral neck fractures disrupt these vessels, causing AVN
• Trendelenburg gait: Damage to the superior gluteal nerve (L4,5,S1) impairs gluteus medius/minimus; the pelvis drops to the opposite side when standing on the affected leg
• Anterior dislocation: Femur forced to rest in flexion, abduction, lateral rotation
• Posterior dislocation (most common): Leg in flexion, adduction, medial rotation; sciatic nerve may be damaged

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Q2. Gluteal Injection and Trendelenburg Sign

1. Gluteus medius - primary abductor of hip; prevents pelvic tilt
2. Gluteus minimus - assists abduction and medial rotation
3. Tensor fascia lata (also supplied by superior gluteal nerve)

Attachments:

• Gluteus medius: Origin - outer surface of ilium between anterior and posterior gluteal lines; Insertion - lateral surface of greater trochanter
• Gluteus minimus: Origin - outer surface of ilium between anterior and inferior gluteal lines; Insertion - anterior surface of greater trochanter

Innervation:

• Superior gluteal nerve (L4, L5, S1) - exits pelvis through greater sciatic foramen above piriformis; runs between gluteus medius and minimus

Actions:

• Abduction of hip
• Medial rotation of hip
• Most important: Stabilize the pelvis during walking (prevents Trendelenburg dip)

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Q3. Relations and Interior of the Second Part of Duodenum

Relations:

Interior Features of 2nd Part:

• Mucosa: Covered with circular folds (plicae circulares / valves of Kerckring) - begin in 2nd part, most prominent in upper jejunum
• Major duodenal papilla (papilla of Vater): On the posteromedial wall at the junction of the upper 2/3 and lower 1/3; the ampulla of Vater opens here; the hepatopancreatic sphincter (Sphincter of Oddi) controls bile and pancreatic secretions
• Minor duodenal papilla: ~2 cm proximal to major papilla; opening of accessory pancreatic duct (duct of Santorini)
• Brunner's glands in submucosa (alkaline mucus)

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Q4. Interior of the Anal Canal

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Q5. Hamstring Muscles (2+1=3)

1. Located in posterior compartment of thigh
2. All cross TWO joints (hip and knee) - except short head of biceps femoris which only crosses knee
3. All originate from ischial tuberosity (except short head of biceps)
4. All extend hip and flex knee
5. Innervated by tibial division of sciatic nerve (except short head of biceps - common peroneal division)
6. Supplied by perforating branches of profunda femoris artery
7. Liable to "hamstring strain" in athletes with sudden hip flexion with knee extended

1. Semitendinosus - long cord-like tendon; medial side; inserts into upper medial shaft of tibia (pes anserinus)
2. Semimembranosus - broad flat tendon; most medial; inserts into posterior medial condyle of tibia

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Q6. McBurney's Point (1+2=3)

1. Site of maximum tenderness in appendicitis - corresponds to the fixed base of the appendix at the confluence of the three taeniae coli on the posteromedial caecum
2. McBurney's incision - oblique muscle-splitting incision at this point used for open appendicectomy; splits external oblique, internal oblique, and transversus abdominis in the direction of their fibers (minimizes wound complications)
3. Rovsing's sign - pressure in left iliac fossa causes pain at McBurney's point (cross tenderness) in appendicitis
4. Rebound tenderness (Blumberg's sign) - sudden release of deep pressure at this point causes more pain than pressure, indicating peritoneal irritation

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Q7. Positions of Vermiform Appendix

1. Retrocaecal (~65%) - most common; behind caecum; atypical presentation; psoas sign positive
2. Pelvic (descending) (~30%) - hangs into pelvis; may mimic pelvic disease (PID, ovarian cyst in females); Rovsing's sign, obturator sign positive
3. Subcaecal (preileal) - below terminal ileum
4. Postileal - behind ileum
5. Paracaecal - beside caecum on medial side
6. Subhepatic - under the liver (failure of caecal descent)

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Q8. Leydig Cells (1+1+1=3)

• Large, polygonal cells with abundant eosinophilic cytoplasm
• Large central nucleus with prominent nucleolus
• Characteristic Reinke crystals (rod-shaped crystalloids) in cytoplasm of human Leydig cells
• Rich in smooth ER and lipid droplets (cholesterol for steroidogenesis)

• Primary source of testosterone (and small amounts of other androgens)
• Stimulated by LH (luteinizing hormone) from anterior pituitary
• Testosterone is essential for: spermatogenesis (via Sertoli cells), development of male secondary sexual characteristics, libido, anabolic effects on muscle and bone, maintenance of male reproductive tract

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Q9. Three Differences: Histology of Duodenum vs. Jejunum

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Index of All Answers

Paper 1 (2026 - 50 marks, 90 min)

Paper 2 (2025 - 100 marks, 180 min)

Paper 3 (2024 Remedial - 50 marks, 90 min)