Digestive System: Key Structures and Terms for Lab Exam

Digestive System Overview

The digestive system is responsible for the breakdown of food, absorption of nutrients, and elimination of waste. It consists of a series of organs and accessory structures that work together to process food from ingestion to excretion.

Main Structures of the Digestive System

• Mouth: The entry point for food; contains teeth, tongue, and salivary glands for mechanical and chemical digestion.

• Tongue: Muscular organ aiding in food manipulation, taste, and swallowing.

• Hard palate: Bony anterior portion of the roof of the mouth, separating oral and nasal cavities.

• Uvula: Small projection hanging from the soft palate, helps prevent food from entering the nasopharynx.

• Nasopharynx, Oropharynx, Laryngopharynx: Regions of the pharynx involved in swallowing and directing food toward the esophagus.

• Epiglottis: Flap of cartilage that covers the trachea during swallowing, preventing aspiration.

• Esophagus: Muscular tube transporting food from the pharynx to the stomach via peristalsis.

Stomach

The stomach is a muscular organ that continues the process of digestion by mixing food with gastric juices.

• Cardiac sphincter (Lower esophageal sphincter): Prevents backflow of stomach contents into the esophagus.

• Cardia: Region where the esophagus connects to the stomach.

• Fundus: Dome-shaped upper portion of the stomach.

• Body: Main central region of the stomach.

• Pylorus: Lower section of the stomach leading to the duodenum.

• Pyloric sphincter: Controls passage of chyme from the stomach to the duodenum.

• Greater curvature: Long, convex lateral border of the stomach.

• Lesser curvature: Short, concave medial border of the stomach.

• Gastric folds (Rugae): Folds in the stomach lining that allow expansion as the stomach fills.

Accessory Organs

• Pancreas: Produces digestive enzymes and hormones (insulin, glucagon).

• Pancreatic duct: Transports pancreatic juices to the duodenum.

• Liver: Produces bile, processes nutrients, detoxifies substances.

• Falciform ligament: Connects the liver to the anterior abdominal wall.

• Gallbladder: Stores and concentrates bile produced by the liver.

• Common hepatic duct: Drains bile from the liver.

• Cystic duct: Connects the gallbladder to the common bile duct.

• Common bile duct: Carries bile from the liver and gallbladder to the duodenum.

• Hepatopancreatic sphincter (Sphincter of Oddi): Controls flow of bile and pancreatic juice into the duodenum.

Small Intestine

The small intestine is the primary site for nutrient absorption and consists of three regions.

• Duodenum: First section; receives chyme from the stomach and digestive secretions from the pancreas and liver.

• Jejunum: Middle section; major site of nutrient absorption.

• Ileum: Final section; absorbs remaining nutrients and connects to the large intestine.

• Ileocecal sphincter: Regulates passage of material from the ileum to the cecum.

Large Intestine

The large intestine absorbs water and electrolytes, forming and storing feces.

• Cecum: First part of the large intestine; receives material from the ileum.

• Appendix: Small, finger-like projection attached to the cecum; contains lymphatic tissue.

• Ascending colon: Travels upward on the right side of the abdomen.

• Transverse colon: Crosses the abdomen from right to left.

• Descending colon: Travels downward on the left side of the abdomen.

• Sigmoid colon: S-shaped segment leading to the rectum.

Summary Table: Digestive System Structures and Functions

Structure	Location	Main Function
Mouth	Oral cavity	Ingestion, mechanical and chemical digestion
Esophagus	Neck and thorax	Transport of food to stomach
Stomach	Upper abdomen	Mixing and breakdown of food
Small intestine	Central abdomen	Digestion and absorption of nutrients
Large intestine	Peripheral abdomen	Absorption of water, formation of feces
Liver	Right upper abdomen	Bile production, metabolism
Pancreas	Behind stomach	Enzyme and hormone secretion
Gallbladder	Under liver	Bile storage and concentration

Additional info:

• The digestive system is covered in detail in Chapter 23: The Digestive System of Anatomy & Physiology textbooks.

• Understanding the location and function of each structure is essential for lab exams and clinical applications.