Digestive System Anatomy

1. Overview of the Digestive System

• The digestive system is responsible for the ingestion, digestion, absorption, and elimination of food and waste.

• It is divided into the gastrointestinal (GI) tract and accessory organs.

• GI tract: Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus.

• Accessory organs: Salivary glands, liver, gallbladder, and pancreas.

2. Mouth (Oral Cavity)

• The starting point of digestion.

• Includes the teeth, tongue, salivary glands.

• Saliva contains amylase to begin the breakdown of carbohydrates.

3. Pharynx

• A muscular tube that connects the mouth to the esophagus.

• Responsible for moving food from the mouth to the esophagus during swallowing.

4. Esophagus

• A muscular tube that extends from the pharynx to the stomach.

• Food is propelled through the esophagus via peristalsis.

• The lower esophageal sphincter (LES) prevents acid reflux from the stomach into the esophagus.

5. Stomach

• A J-shaped organ located on the left side of the abdominal cavity.

• Divisions: Fundus, body, and pylorus.

• Function: The stomach secretes gastric juices containing hydrochloric acid (HCl) and enzymes, such as pepsin, which digest proteins.

• The pyloric sphincter controls the release of chyme into the small intestine.

6. Small Intestine

• The primary site of nutrient absorption.

• Consists of three parts:

• Duodenum: First part, where bile and pancreatic enzymes help digest food.

• Jejunum: Middle part, where most nutrient absorption occurs.

• Ileum: Last part, responsible for absorbing bile acids and vitamin B12.

• The inner lining has villi, small finger-like projections that increase surface area for absorption.

7. Large Intestine (Colon)

• Absorbs water and electrolytes from the remaining indigestible food matter.

• Composed of four parts:

• Cecum: The first part, connected to the ileum and the appendix.

• Ascending colon: Moves upwards on the right side of the abdomen.

• Transverse colon: Runs across the abdomen.

• Descending colon: Moves downward on the left side.

• The rectum stores waste until it is eliminated through the anus.

8. Liver

• Located in the upper right quadrant of the abdomen.

• Functions:

• Produces bile, which helps emulsify fats.

• Metabolizes nutrients and detoxifies harmful substances.

• Stores glycogen, vitamins, and minerals.

9. Gallbladder

• Located beneath the liver.

• Stores and concentrates bile produced by the liver.

• Releases bile into the duodenum to aid in fat digestion.

10. Pancreas

• Located behind the stomach.

• Functions:

• Endocrine: Secretes insulin and glucagon to regulate blood sugar.

• Exocrine: Produces pancreatic enzymes (e.g., amylase, lipase, proteases) to digest carbohydrates, fats, and proteins.