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.
12chapters144questions84High-Yield
Definition
The gastrointestinal tract wall has four basic layers throughout, with regional modifications suited to each part’s function.
Four Layers (inner → outer)
- Mucosa — epithelium, lamina propria, muscularis mucosae
- Submucosa — connective tissue, vessels, Meissner’s plexus
- Muscularis externa — circular + longitudinal (Auerbach’s plexus)
- Serosa / adventitia
Regional Variations
- Oesophagus — stratified squamous epithelium
- Stomach — gastric glands, rugae
- Small intestine — villi, microvilli
- Large intestine — no villi, many goblet cells
Four concentric layers, modified region by region along the gut. Region Feature Oesophagus Stratified squamous Small intestine Villi + microvilli Large intestine Goblet cells, no villi Applied
- Barrett’s oesophagus (metaplasia)
- Coeliac disease (villous atrophy)
🔑KEY POINTS TO REMEMBER- Four layers: mucosa, submucosa, muscularis externa, serosa.
- Plexuses: Meissner’s (submucosa), Auerbach’s (muscularis).
- Villi in small intestine; goblet cells in large.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
The respiratory tract conducts and conditions air; the lung is the site of gas exchange in the alveoli.
Conducting Portion
- Trachea/bronchi — pseudostratified ciliated columnar + goblet cells
- C-shaped cartilage (trachea)
- Bronchioles — no cartilage, smooth muscle
Respiratory Portion
- Respiratory bronchioles → alveolar ducts → alveoli
- Site of gas exchange
Alveolar Cells
- Type I pneumocytes — gas exchange
- Type II pneumocytes — surfactant
- Alveolar macrophages
Air is conducted and conditioned, then exchanged across alveoli. Cell Function Type I Gas exchange Type II Surfactant Macrophage Defence Applied
- Surfactant deficiency (respiratory distress syndrome)
- Mucociliary clearance
🔑KEY POINTS TO REMEMBER- Conducting (ciliated, cartilage) vs respiratory (alveoli) portions.
- Type I = gas exchange; type II = surfactant.
- Surfactant deficiency → RDS.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
Blood vessels and the heart share a three-layered wall structure adapted to their functions.
Three Layers
- Tunica intima — endothelium
- Tunica media — smooth muscle / elastic
- Tunica adventitia — connective tissue
Vessel Types
- Elastic arteries (aorta) — elastic media
- Muscular arteries — muscular media
- Capillaries — endothelium only
- Veins — thin wall, valves
Heart Wall
- Endocardium, myocardium, epicardium
- (= intima, media, adventitia equivalents)
The same three-layer plan underlies vessels and the heart wall. Vessel Media Elastic artery Elastic laminae Muscular artery Smooth muscle Capillary None Applied
- Atherosclerosis (intima)
- Aneurysm (media)
🔑KEY POINTS TO REMEMBER- Three layers: intima, media, adventitia.
- Elastic vs muscular arteries differ in the media.
- Heart: endo-, myo-, epicardium.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
The kidney filters blood via its functional unit, the nephron.
Nephron Parts
- Renal corpuscle — glomerulus + Bowman’s capsule
- Proximal convoluted tubule (brush border)
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
Filtration Barrier
- Fenestrated endothelium
- Glomerular basement membrane
- Podocyte foot processes
Filtrate forms at the glomerulus and is processed along the tubule. Segment Function Glomerulus Filtration PCT Bulk reabsorption Loop of Henle Concentration Collecting duct Final urine Applied
- Nephrotic syndrome (podocyte damage)
- Glomerulonephritis
🔑KEY POINTS TO REMEMBER- Nephron: corpuscle, PCT, loop, DCT, collecting duct.
- Barrier: endothelium, basement membrane, podocytes.
- Podocyte damage → nephrotic syndrome.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
The skin consists of epidermis and dermis, with appendages (hair, nails, glands) derived from the epidermis.
Epidermis (layers)
- Basale, spinosum, granulosum, lucidum, corneum
- Keratinocytes + melanocytes
- Stratified squamous keratinised
Dermis
- Connective tissue
- Vessels, nerves, sensory receptors
Appendages
- Hair follicles
- Sebaceous glands (holocrine)
- Sweat glands (eccrine, apocrine)
- Nails
Epidermis, dermis and epidermal appendages together form the skin. Appendage Type Sebaceous Holocrine Eccrine sweat Merocrine Hair Epidermal Applied
- Psoriasis (↑ turnover)
- Acne (sebaceous glands)
🔑KEY POINTS TO REMEMBER- Skin = epidermis + dermis + appendages.
- Epidermis: 5 layers, keratinocytes + melanocytes.
- Appendages: hair, sebaceous, sweat glands, nails.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
The GI tract wall has four concentric layers from the lumen outward.
Layers (inner → outer)
- Mucosa — epithelium + lamina propria + muscularis mucosae
- Submucosa — vessels + Meissner’s plexus
- Muscularis externa — circular + longitudinal + Auerbach’s plexus
- Serosa / adventitia
Four layers, each with its own components and nerve plexus. Layer Key feature Mucosa Epithelium Submucosa Meissner’s plexus Muscularis Auerbach’s plexus Applied
- Hirschsprung disease (absent myenteric plexus)
🔑KEY POINTS TO REMEMBER- Four layers: mucosa, submucosa, muscularis externa, serosa.
- Meissner’s (submucosa) & Auerbach’s (muscularis) plexuses.
- Absent plexus → Hirschsprung.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
The alveolus is the site of gas exchange; the blood-air barrier is the thin membrane separating alveolar air from blood.
Alveolar Wall
- Type I pneumocytes (gas exchange)
- Type II pneumocytes (surfactant)
- Alveolar macrophages
Blood-Air Barrier (3 layers)
- Type I pneumocyte + its basement membrane
- Fused basement membrane
- Capillary endothelium
Three thin layers separate air from blood for efficient gas exchange. Layer Component 1 Type I pneumocyte 2 Basement membrane 3 Endothelium Applied
- Thickened in fibrosis / oedema → impaired exchange
🔑KEY POINTS TO REMEMBER- Alveolar cells: type I (exchange), type II (surfactant), macrophage.
- Blood-air barrier: pneumocyte, basement membrane, endothelium.
- Thickening impairs gas exchange.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
Elastic and muscular arteries differ in the composition of their tunica media, matching their function.
Elastic Arteries
- Large (aorta, pulmonary)
- Media — many elastic laminae
- Conduct + dampen pulsatile flow
Muscular Arteries
- Medium-sized (named arteries)
- Media — smooth muscle
- Distribute + regulate flow
Large arteries recoil elastically; medium ones regulate by muscle. Feature Elastic Muscular Media Elastic laminae Smooth muscle Example Aorta Radial artery Role Conduct Distribute Applied
- Elastic recoil maintains diastolic flow
🔑KEY POINTS TO REMEMBER- Elastic arteries: elastic media, conduct (aorta).
- Muscular arteries: smooth-muscle media, distribute.
- Elastic recoil = diastolic flow.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
The renal corpuscle is the filtering unit of the nephron, consisting of the glomerulus and Bowman’s capsule.
Components
- Glomerulus — tuft of capillaries
- Bowman’s capsule (parietal + visceral layers)
- Podocytes (visceral layer)
- Mesangial cells
Filtration Barrier
- Fenestrated endothelium
- Glomerular basement membrane
- Podocyte foot processes (filtration slits)
Blood is filtered across three layers into Bowman’s space. Barrier Layer 1 Fenestrated endothelium 2 Basement membrane 3 Podocytes Applied
- Nephrotic syndrome (podocyte damage)
🔑KEY POINTS TO REMEMBER- Renal corpuscle = glomerulus + Bowman’s capsule.
- Barrier: endothelium, basement membrane, podocytes.
- Podocyte damage → proteinuria.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
The juxtaglomerular apparatus (JGA) is a specialised structure at the vascular pole of the glomerulus that regulates blood pressure and filtration.
Components
- JG cells — modified smooth muscle (afferent arteriole) → secrete renin
- Macula densa — sensing cells (DCT)
- Extraglomerular mesangial cells
Function
- Senses Na⁺ and blood pressure
- Secretes renin → renin-angiotensin system
The JGA senses sodium and pressure and releases renin to correct them. Cell Role JG cells Secrete renin Macula densa Sense Na⁺ Applied
- Renin → hypertension
- RAAS regulation
🔑KEY POINTS TO REMEMBER- JGA: JG cells (renin), macula densa (Na⁺ sensing), mesangial cells.
- Controls BP via renin-angiotensin system.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
The epidermis is stratified squamous keratinised epithelium with five layers (in thick skin).
Layers (deep → superficial)
- Stratum basale — dividing cells
- Stratum spinosum — desmosomes
- Stratum granulosum — keratohyalin
- Stratum lucidum — thick skin only
- Stratum corneum — dead keratinised cells
Cells form at the base and keratinise as they rise to the surface. Layer Feature Basale Stem cells Granulosum Keratohyalin Corneum Keratin, dead cells Applied
- ‘Come, Let’s Get Sun Burnt’ mnemonic
- Psoriasis — increased turnover
🔑KEY POINTS TO REMEMBER- Epidermis (deep→superficial): basale, spinosum, granulosum, lucidum, corneum.
- Basale divides; corneum is dead keratin.
- Lucidum only in thick skin.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.Definition
The liver lobule is the classic structural unit of the liver — a hexagonal arrangement of hepatocytes around a central vein.
Structure
- Central vein at the centre
- Hepatocytes in radiating plates
- Sinusoids between the plates
- Portal triads at the corners
Portal Triad
- Hepatic artery branch
- Portal vein branch
- Bile duct
Blood flows from portal triads through sinusoids to the central vein. Structure Location Central vein Centre Portal triad Corners Sinusoids Between plates Applied
- Zone 3 (centrilobular) — ischaemia-prone
- Cirrhosis (architecture lost)
🔑KEY POINTS TO REMEMBER- Liver lobule: hexagonal, central vein + portal triads at corners.
- Portal triad = hepatic artery, portal vein, bile duct.
- Zone 3 vulnerable to ischaemia.
📚SOURCES: Inderbir Singh’s Textbook of Human Histology; di Fiore’s Atlas of Histology; Gray’s Anatomy.