Digestive System Overview

Digestive System

• The digestive system performs six basic activities: ingestion, mechanical digestion, chemical digestion, absorption, and elimination
• Mechanical digestion involves physical breakdown of food into smaller particles, while chemical digestion involves enzymatic breakdown of nutrients into absorbable forms
• The digestive system consists of the mouth, esophagus, stomach, small intestine, and large intestine

Mouth

• The mouth contains four types of teeth: incisors (cutting), canines (piercing), premolars (crushing), and molars (grinding)
• Teeth are responsible for mechanical digestion of food

Esophagus

• The esophagus uses peristalsis (muscular contractions) to transport food to the stomach

Stomach

• The stomach is a muscular, elastic sac that mixes food with stomach acid and digestive enzymes
• The mucosa wall of the stomach consists of epithelial cells, lamina propria, and muscularis mucosae
• The stomach churns and mixes food for about an hour, breaking it down into a liquid mixture called chyme

Small Intestine

• The small intestine is responsible for most of our nutrient absorption
• Finger-like projections called villi increase the surface area for absorption
• Nutrients absorbed through villi include carbohydrates, proteins, and fats
• The lacteal, a lymphatic vessel, absorbs fats and fat-soluble vitamins

Pancreas and Bile

• The pancreas produces digestive enzymes, including amylase (carbohydrates), lipase (fats), and trypsin (proteins)
• Bile is produced in the liver, stored in the gallbladder, and released into the small intestine to emulsify fats

Large Intestine

• The large intestine, or colon, is responsible for water absorption, electrolyte absorption, and storage of indigestible waste
• The large intestine consists of the cecum, colon, rectum, and anus

Excretion and Elimination

• Excretion is the process of removing wastes and excess substances from the body
• Elimination is the process of removing waste from the body
• Excretory organs include the kidneys, liver, skin, and lungs

Kidneys

• The kidneys filter waste and excess substances from the blood through glomerular filtration
• The nephron is the functional unit of the kidney, consisting of the glomerulus, Bowman's capsule, and renal tubules
• Selective reabsorption and tubular secretion occur in the nephron
• Urine composition includes water, urea, salts, and other waste products

Liver and Deamination

• The liver breaks down proteins through deamination, producing ammonia and alpha-ketoglutarate
• The liver also converts ammonia into urea through the urea cycle

Disorders and Treatment

• Disorders of the digestive system include gastroesophageal reflux disease (GERD), peptic ulcers, and malabsorption
• Treatment options include peritoneal dialysis and hemodialysis for kidney failure

Learn about the digestive system, including chemical and mechanical digestion, its 6 basic activities, and the structure and function of each part. Identify the 4 types of teeth and explain the process of peristalsis. Explore the type of digestion occurring at each stage in the digestive system.