Digestive System: Anatomy, Functions, and Key Structures

Extrinsic

Control from outside the organ (e.g., autonomic nervous system).

Intrinsic

Control within the organ itself (e.g., enteric nervous system).

Peritoneum

Serous membrane lining the abdominal cavity.

Visceral peritoneum

Covers organs.

Parietal peritoneum

Lines body wall.

Mesentery

Double-layered peritoneum that holds intestines in place and carries blood vessels.

Retroperitoneal

Organs located behind the peritoneum (e.g., kidneys, pancreas).

Portal system

Blood flow from one capillary bed to another before returning to the heart.

Portal triad

Branch of hepatic artery, portal vein, and bile duct.

Bolus

Chewed food mixed with saliva.

Chyme

Semi-liquid mixture leaving stomach.

Rugae

Folds in stomach lining allowing expansion.

Bile

Fluid from liver that emulsifies fats.

Plicae circulares

Circular folds in small intestine that increase surface area.

Villi

Fingerlike projections for absorption.

Microvilli

Microscopic projections forming the brush border.

Peyer's patches

Lymphoid tissue in ileum (immune defense).

Ingestion

Taking in food.

Secretion

Release of enzymes, acid, mucus.

Mixing & propulsion

Movement (swallowing, peristalsis).

Digestion

Mechanical + chemical breakdown.

Absorption

Nutrients enter blood/lymph.

Defecation

Elimination of waste.

Alimentary Canal (GI tract)

Mouth, Pharynx, Esophagus, Stomach, Small intestine, Large intestine, Anus.

Accessory Organs

Teeth, Tongue, Salivary glands, Liver, Gallbladder, Pancreas.