Digestive System Overview

Introduction

• Digestive System: Study of digestive tract, liver, and pancreas.
• Also known as the gastrointestinal tract.
• Pathway: From mouth to anus.
• Specialist: Gastroenterologist.

Organs of the Digestive System

• Primary Organs:
  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small Intestine
  • Large Intestine
• Accessory Organs:
  • Salivary Glands
  • Teeth
  • Liver
  • Gallbladder
  • Pancreas
  • Appendix

Functional Anatomy

Mouth

• First organ of digestion.
• Mastication: Teeth break down food into small particles.

Salivary Glands

• 3 pairs surround the oral cavity.
• Produce saliva (~1.5 liters/day).
• Saliva aids in the beginning of digestion.

Pharynx

• Also known as the throat.
• Muscular tube (~5 inches long).
• Passage for air and food.
• Epiglottis: Prevents food from entering the trachea.

Esophagus

• Muscular tube (~9 inches long).
• Connects pharynx to stomach.
• Uses rhythmic contractions (peristalsis) to move food.

Stomach

• Sections: Fundus (upper), Body (middle), Pylorus (lower).
• Sphincters:
  • Cardiac: Moves food into the stomach.
  • Pyloric: Allows digested food to exit.
• Rugae: Folds containing glands for enzymes and HCl secretion.
• Produces ~2.5 liters of acidic fluid/day.

Small Intestine

• Length: ~20 feet.
• Parts:
  • Duodenum: Receives food, bile, and pancreatic juices.
  • Jejunum: ~8 feet.
  • Ileum: ~11 feet, connects to the large intestine.
• Lined with villi for nutrient absorption.

Large Intestine

• Extends from ileum to anus.
• Parts:
  • Cecum: Attaches to ileum by ileocecal valve.
  • Colon: Ascending, transverse, descending, sigmoid.
  • Rectum: Ends at the anus.
• Absorbs water, forms solid waste.

Additional Organs

Liver

• Location: Right upper quadrant of abdomen.
• Produces bile (contains cholesterol, bile acids, bilirubin).
• Functions:
  • Produces bile for fat emulsification.
  • Glucose regulation (storage and release).
  • Protein synthesis for blood clotting.
  • Erythrocyte destruction, bilirubin release.
  • Detoxification.
• Blood supply: Hepatic portal system.

Gallbladder

• Stores and concentrates bile.
• Releases bile in response to food presence.

Pancreas

• Exocrine and endocrine functions.
• Produces pancreatic juices (digestive enzymes).
• Secretes insulin for blood sugar regulation.

Digestive Process

• Flowchart:
  • Oral Cavity → Pharynx → Esophagus → Stomach → Duodenum
  • Liver & Gallbladder release bile, Pancreas releases juices
  • Jejunum → Ileum → Large Intestine → Cecum → Colon → Sigmoid → Rectum → Anus
  • Waste (feces) exits the body.

These notes cover the structure, function, and process of the human digestive system. They are designed to help in understanding the key components and their roles in digestion.