Anatomy
MBBS Anatomy question bank: general anatomy and osteology, regional gross anatomy (upper limb, lower limb, thorax, abdomen, pelvis, head and neck), neuroanatomy, histology and embryology.
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Definition
The anterior abdominal wall is a musculo-aponeurotic wall protecting the viscera; the inguinal canal is an oblique passage in its lower part transmitting the spermatic cord / round ligament.
Muscles
- External oblique
- Internal oblique
- Transversus abdominis
- Rectus abdominis (in the rectus sheath)
Inguinal Canal — Walls
- Anterior — external oblique aponeurosis
- Posterior — transversalis fascia + conjoint tendon
- Roof — arching fibres of internal oblique/transversus
- Floor — inguinal ligament
Rings & Contents
- Deep ring — in transversalis fascia
- Superficial ring — in external oblique
- Contents: spermatic cord (M) / round ligament (F)
The canal runs obliquely from the deep to the superficial ring. Wall Formed by Anterior External oblique Posterior Transversalis fascia, conjoint tendon Floor Inguinal ligament Applied
- Inguinal hernia
- Site of surgical repair
🔑KEY POINTS TO REMEMBER- Wall: external/internal oblique, transversus, rectus.
- Canal walls: ext. oblique (ant), transversalis fascia (post), inguinal ligament (floor).
- Transmits spermatic cord / round ligament.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The peritoneum is a serous membrane lining the abdominal cavity (parietal) and covering the viscera (visceral); between them is the peritoneal cavity.
Types
- Parietal — lines the wall (somatic, well-localised pain)
- Visceral — covers organs (poorly localised pain)
Peritoneal Folds
- Mesentery — suspends the small intestine
- Omenta (greater, lesser)
- Peritoneal ligaments
Organ Relations
- Intraperitoneal — stomach, spleen, jejunum
- Retroperitoneal — kidneys, pancreas, aorta
Two layers enclose a potential cavity holding a little fluid. Position Organs Intraperitoneal Stomach, spleen, jejunum Retroperitoneal Kidney, pancreas, aorta Applied
- Peritonitis
- Ascites; peritoneal dialysis
🔑KEY POINTS TO REMEMBER- Peritoneum: parietal (wall) + visceral (organs).
- Folds: mesentery, omenta, ligaments.
- Intra- vs retroperitoneal organs.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The gastrointestinal viscera (stomach to rectum) are supplied by three unpaired branches of the abdominal aorta, matching the embryological gut divisions.
Blood Supply (by gut region)
- Foregut — coeliac trunk (stomach to mid-duodenum)
- Midgut — superior mesenteric artery (to 2/3 transverse colon)
- Hindgut — inferior mesenteric artery (to rectum)
Key Organs
- Stomach; small intestine (duodenum, jejunum, ileum)
- Large intestine (caecum, colon, rectum)
Three unpaired aortic branches supply the fore-, mid- and hindgut. Gut Artery Extent Foregut Coeliac Stomach–mid duodenum Midgut SMA Duodenum–2/3 transverse colon Hindgut IMA Left colon–rectum Applied
- Ischaemia at watershed areas (splenic flexure)
- Venous drainage into the portal system
🔑KEY POINTS TO REMEMBER- Foregut = coeliac; midgut = SMA; hindgut = IMA.
- Venous drainage → portal vein → liver.
- Watershed ischaemia at the splenic flexure.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The liver, biliary system, pancreas and spleen are the major abdominal organs associated with digestion and blood.
Liver
- Largest gland; 4 lobes (right, left, caudate, quadrate)
- Functional segments (portal/hepatic veins)
- Dual supply: hepatic artery + portal vein
Biliary System
- Liver → hepatic ducts → common bile duct
- Gallbladder — stores and concentrates bile
Pancreas & Spleen
- Pancreas: head, neck, body, tail; retroperitoneal; exo + endocrine
- Spleen: largest lymphoid organ (left hypochondrium, ribs 9–11)
These upper-abdominal organs handle digestion, bile and blood. Organ Feature Liver Dual blood supply Gallbladder Stores bile Pancreas Exo + endocrine Spleen Lymphoid Applied
- Gallstones, jaundice
- Splenic rupture (rib fracture)
🔑KEY POINTS TO REMEMBER- Liver: 4 lobes, dual supply (hepatic artery + portal vein).
- Biliary: hepatic ducts → CBD → duodenum; gallbladder stores bile.
- Spleen: largest lymphoid organ, ribs 9–11.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The kidneys and suprarenal (adrenal) glands are retroperitoneal organs on the posterior abdominal wall.
Kidneys
- Retroperitoneal (T12–L3)
- Right kidney lower than left (liver above)
- Hilum: renal vein, artery, pelvis (front → back)
Suprarenal Glands
- On the upper pole of each kidney
- Cortex (steroids) + medulla (catecholamines)
Posterior Abdominal Wall Muscles
- Psoas major, quadratus lumborum, iliacus
The kidneys and adrenals lie retroperitoneally on the posterior wall muscles. Hilum (front→back) Structure Anterior Renal vein Middle Renal artery Posterior Renal pelvis Applied
- Renal angle tenderness
- Psoas abscess / psoas sign
🔑KEY POINTS TO REMEMBER- Kidneys retroperitoneal T12–L3; right lower than left.
- Hilum (front→back): vein, artery, pelvis.
- Suprarenal on upper pole; posterior wall: psoas, QL, iliacus.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The inguinal canal is an oblique passage (~4 cm) in the lower anterior abdominal wall, transmitting the spermatic cord (male) or round ligament (female).
Walls
- Anterior — external oblique aponeurosis
- Posterior — transversalis fascia + conjoint tendon
- Roof — arching internal oblique / transversus
- Floor — inguinal ligament
Rings & Contents
- Deep ring (transversalis fascia)
- Superficial ring (external oblique)
- Contents: cord / round ligament + ilioinguinal nerve
The canal transmits its contents from the deep to the superficial ring. Wall Formed by Anterior External oblique Posterior Transversalis fascia Floor Inguinal ligament Applied
- Site of inguinal hernia
🔑KEY POINTS TO REMEMBER- Canal walls: ext. oblique (ant), transversalis fascia (post), inguinal ligament (floor).
- Deep + superficial rings.
- Transmits cord / round ligament.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
An inguinal hernia is protrusion of abdominal contents through the inguinal region; it is indirect (through the deep ring) or direct (through the posterior wall).
Indirect
- Through the deep inguinal ring
- Lateral to the inferior epigastric artery
- Congenital (patent processus vaginalis)
- Commoner, younger, can enter the scrotum
Direct
- Through the posterior wall (Hesselbach’s triangle)
- Medial to the inferior epigastric artery
- Acquired, older, rarely enters the scrotum
The relation to the inferior epigastric artery separates direct from indirect. Feature Indirect Direct Ring Deep ring Posterior wall Epigastric a. Lateral Medial Age Young Old Scrotum Often Rarely Applied
- Reducible → obstructed → strangulated
🔑KEY POINTS TO REMEMBER- Indirect: deep ring, lateral to epigastric a., congenital, into scrotum.
- Direct: posterior wall, medial to epigastric a., acquired.
- Strangulation is the danger.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The coeliac trunk is the first ventral branch of the abdominal aorta (T12), supplying foregut structures.
Branches (3)
- Left gastric artery — stomach
- Splenic artery — spleen, pancreas
- Common hepatic — liver, gallbladder, duodenum
The coeliac trunk gives three branches to the foregut organs. Branch Supplies Left gastric Stomach Splenic Spleen, pancreas Common hepatic Liver, gallbladder Applied
- Supplies the foregut
- Median arcuate ligament compression
🔑KEY POINTS TO REMEMBER- Coeliac trunk (T12): foregut supply.
- Branches: left gastric, splenic, common hepatic.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The portal vein carries venous blood from the GI tract to the liver; portosystemic anastomoses connect it with systemic veins and dilate in portal hypertension.
Formation
- Splenic vein + superior mesenteric vein
- Behind the neck of the pancreas
- Carries nutrient-rich blood to the liver
Portosystemic Sites
- Lower oesophagus → oesophageal varices
- Rectum → haemorrhoids
- Umbilicus → caput medusae
- Retroperitoneal
When portal pressure rises, blood diverts through portosystemic connections. Site Result Oesophagus Varices Rectum Haemorrhoids Umbilicus Caput medusae Applied
- Portal hypertension (cirrhosis)
- Variceal bleeding
🔑KEY POINTS TO REMEMBER- Portal vein = splenic vein + SMV (behind pancreas neck).
- Portosystemic sites: oesophagus, rectum, umbilicus.
- Portal hypertension → varices.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The extrahepatic biliary apparatus conveys bile from the liver to the duodenum and includes the gallbladder.
Components
- Right + left hepatic ducts → common hepatic duct
- Cystic duct (from the gallbladder)
- Common bile duct → duodenum (with the pancreatic duct)
Gallbladder
- Stores and concentrates bile
- Fundus, body, neck
- Calot’s triangle contains the cystic artery
Bile flows from liver ducts, joins the pancreatic duct, and enters the duodenum. Duct Formed by Common hepatic R + L hepatic ducts Common bile duct Common hepatic + cystic Applied
- Gallstones → obstructive jaundice
- Cholecystectomy (Calot’s triangle)
🔑KEY POINTS TO REMEMBER- Hepatic ducts → CHD; + cystic duct → CBD → duodenum.
- Gallbladder stores/concentrates bile.
- Calot’s triangle = cystic artery.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The kidney is a bean-shaped retroperitoneal organ (T12–L3) with an outer cortex and inner medulla.
Structure
- Cortex (outer) + medulla (pyramids)
- Renal pelvis → ureter
- Hilum: vein, artery, pelvis (front → back)
Relations
- Right kidney lower (liver above)
- Anterior relations differ (liver, duodenum / spleen, stomach)
- Suprarenal gland on the upper pole
The kidney has a cortex and medulla, draining via the pelvis into the ureter. Hilum (front→back) Structure Anterior Renal vein Middle Renal artery Posterior Renal pelvis Applied
- Renal angle tenderness
- Nephrectomy relations
🔑KEY POINTS TO REMEMBER- Kidney: cortex + medulla (pyramids), retroperitoneal T12–L3.
- Hilum (front→back): vein, artery, pelvis.
- Right kidney lower than left.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The vermiform appendix is a narrow blind tube arising from the caecum; McBurney’s point marks its surface location.
Appendix
- Arises from the posteromedial caecum
- Base: convergence of the taeniae coli
- Positions: retrocaecal (commonest), pelvic
- Supplied by the appendicular artery (an end artery)
McBurney’s Point
- Junction of lateral 1/3 and medial 2/3
- On a line from umbilicus to the ASIS
- Point of maximum tenderness in appendicitis
The appendix hangs from the caecum; its tenderness localises to McBurney’s point. Feature Detail Base Convergence of taeniae Common position Retrocaecal Surface point McBurney’s Applied
- Appendicitis — common surgical emergency
- End artery → risk of gangrene
🔑KEY POINTS TO REMEMBER- Appendix from caecum; base at taeniae convergence.
- McBurney’s point: lateral 1/3 on umbilicus–ASIS line.
- End artery → gangrene risk in appendicitis.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.