Human Digestive System Overview

Human Digestive System

• The digestive system comprises organs that process food, extract nutrients, and eliminate waste.
• Structures involved include the mouth, esophagus, stomach, small intestine, large intestine, and accessory organs like liver, pancreas, and gallbladder.

Sphincters

• Pyloric sphincter: Controls food passage from the stomach to the small intestine.
• Cardiac sphincter: Separates the esophagus from the stomach, preventing backflow.
• Anal sphincter: Regulates the release of waste from the rectum.

Peristalsis

• Peristalsis is wave-like muscle contractions that move food through the digestive tract.
• Circular and longitudinal muscles in the digestive tract walls contract and relax to propel food.

Digestion Stages

• Ingestion: Taking food into the body through the mouth.
• Physical Breakdown: Mechanical processes like chewing and stomach churning break down food into smaller pieces.
• Chemical Breakdown: Enzymes break down complex molecules (carbohydrates, proteins, fats) into simpler absorbable units.
• Absorption: Nutrients are absorbed into the bloodstream through the walls of the small intestine.
• Egestion: Undigested materials are eliminated from the body.

Accessory Organs

• Liver: Produces bile, crucial for fat digestion.
• Pancreas: Secretes enzymes and bicarbonate to aid digestion.
• Gallbladder: Stores and concentrates bile, releasing it into the small intestine.

Small Intestine Sections

• Duodenum: Site where most chemical digestion occurs, receiving secretions from the pancreas and liver.
• Jejunum: Primary site for nutrient absorption, with abundant villi for increased surface area.
• Ileum: Absorbs remaining nutrients and moves digested material to the large intestine.

Digestive Enzymes

• Various enzymes facilitate chemical breakdown in different parts of the digestive system.
• Examples include amylase, pepsin, lipase, and trypsin.

Absorption in Small Intestine

• Villi and microvilli in the small intestine significantly increase the surface area for absorption of nutrients.
• Nutrients diffuse across the cell membrane and into capillaries for transport throughout the body.