Overview of the Digestive System

Overview of the Digestive System

• The digestive system is a complex biological process that breaks down food into usable nutrients.
• It involves mechanical and chemical processes.
• Key organs include the mouth, esophagus, stomach, small intestine, large intestine, and anus.

Mouth

• Mechanical digestion begins with chewing (mastication).
• Salivary glands produce saliva containing enzymes, initiating chemical digestion.
• Saliva moistens food for easier swallowing.
• Teeth mechanically break down food particles.

Esophagus

• A muscular tube connecting the mouth to the stomach.
• Peristalsis, wave-like muscle contractions, moves food toward the stomach.
• A sphincter muscle at the top of the esophagus prevents air from entering.
• A sphincter muscle at the bottom, the lower esophageal sphincter (LES), prevents stomach acid reflux into the esophagus.

Stomach

• A muscular sac that stores and mixes food.
• Gastric glands secrete gastric juice, containing pepsin (protein digestion) and hydrochloric acid (HCl).
• HCl kills bacteria and activates pepsin.
• The stomach mechanically mixes food into chyme.
• The pyloric sphincter regulates the release of chyme into the small intestine.

Small Intestine

• The primary site of nutrient absorption.
• Divided into three sections: duodenum, jejunum, ileum.
• Duodenum receives pancreatic juice and bile.
• Pancreatic juice contains enzymes for carbohydrate, protein, and fat digestion.
• Bile emulsifies fats, making them more accessible to enzymes.
• The small intestine's lining has villi and microvilli, increasing surface area for absorption.
• Nutrients are absorbed into the bloodstream.

Large Intestine

• Absorbs water and electrolytes from the remaining undigested material.
• Houses beneficial bacteria.
• Forms and stores feces.
• Divided into cecum, colon (ascending, transverse, descending, sigmoid), rectum, and anal canal.
• The rectum stores feces until elimination.

Accessory Organs

• Pancreas: Produces pancreatic juice containing digestive enzymes.
• Liver: Produces bile for fat emulsification.
• Gallbladder: Stores and concentrates bile.

Digestive System Function

• The system breaks down complex food molecules into smaller components.
• These smaller molecules are absorbed into the bloodstream.
• Absorbed nutrients fuel cellular activities and build body tissues.
• Waste products are eliminated as feces.

Digestive Processes

• Ingestion: Taking food into the digestive system
• Propulsion: Movement of food through the digestive system
• Mechanical digestion: Physical breakdown of food
• Chemical digestion: Breakdown of food molecules using enzymes
• Absorption: Movement of nutrients into the bloodstream

Disorders of the Digestive System

• Heartburn: Acid reflux
• Peptic ulcers: Sores in the lining of the stomach or duodenum
• Irritable bowel syndrome (IBS): Chronic abdominal pain and changes in bowel habits
• Inflammatory bowel disease (IBD): Chronic inflammation of the digestive tract
• Celiac disease: Autoimmune disorder responding to gluten.