Ch. 14 PP

Chapter 14: Digestive System

• Overview of structures involved in the digestive system.

• Key components include:

  • Mouth

  • Teeth

  • Salivary Glands

  • Tongue

  • Pharynx

  • Epiglottis

  • Esophagus

  • Liver

  • Stomach

  • Gallbladder

  • Pancreas

  • Large Intestine

  • Small Intestine

  • Appendix

  • Rectum

  • Anus

The Digestive System: Basic Functions

• Ingestion: Taking in food.

• Digestion: Breaking food into nutrient molecules.

• Absorption: Movement of nutrients into the bloodstream.

• Defecation: Excretion of indigestible waste.

Functions of the Digestive System

1. Ingestion: Food enters via oral cavity with mastication (chewing).

2. Mechanical Digestion: Physical breakdown of food (occurs in oral cavity and stomach).

3. Chemical Digestion: Hydrolysis reactions aided by enzymes (mainly in stomach and small intestine).

4. Secretion: Enzymes and digestive fluids secreted from digestive tract and accessory organs.

5. Absorption: Nutrients pass to blood or lymph.

6. Elimination: Undigested food released through defecation.

Digestive Processes

• Propulsion Processes:

  • Swallowing (Pharynx)

  • Peristalsis (Esophagus, stomach, small and large intestine).

• Mechanical Digestion: chewed food (mouth), churning (stomach), segmentation (small intestine).

• Chemical Digestion & Absorption: Nutrients and water move to blood and lymph vessels.

Anatomy of the Digestive System

• Alimentary Canal (GI tract): Continuous hollow tube from mouth to anus.

  • Includes organs like mouth, pharynx, esophagus, stomach, intestines, anus.

• Accessory Digestive Organs: Teeth, tongue, salivary glands, liver, gallbladder, pancreas.

Digestive System Anatomy Overview

• Oral Cavity: Contains teeth, tongue, and salivary glands.

• Pharynx: Passageway for food and air (divided into oropharynx and laryngopharynx).

• Esophagus: 10 inches long, conducts food from pharynx to stomach.

Layers of Tissue in Alimentary Canal

• Mucosa: Innermost, moist membrane.

• Submucosa: Soft connective tissue with blood vessels.

• Muscularis Externa: Smooth muscle layers.

• Serosa: Outermost layer with visceral peritoneum.

Stomach Anatomy and Functions

• C-shaped organ, located in the left abdominal cavity.

• Holds up to 4 liters of food and processes it into chyme.

• Regions include Cardia, Fundus, Body, and Pylorus.

• Functions: Temporary food storage, breakdown of food, initiates protein digestion.

Structure of the Stomach Mucosa

• Composed of simple columnar epithelium; secretes gastric fluids.

• Contains various cell types (chief, parietal, mucous neck, and enteroendocrine cells).

Small Intestine Overview

• Major digestive organ; site of nutrient absorption.

• Divided into three regions: Duodenum, Jejunum, Ileum.

• It has structural modifications (villi, microvilli) to enhance absorption.

Large Intestine Overview

• Shorter but larger in diameter than small intestine (1.5 meters).

• Functions include absorption of water and minerals; formation of feces.

• Parts: Cecum, Appendix, Colon, Rectum, Anal Canal.

Accessory Digestive Organs

• Teeth: Assist in mastication; have various types according to function.

• Salivary Glands: Produce saliva to aid in digestion.

• Pancreas: Produces digestive enzymes and hormones.

• Liver: Produces bile for fat emulsification.

• Gallbladder: Stores and concentrates bile.

Hormones Involved in Digestion

• Secretin: Stimulates pancreatic juice and bile output.

• Cholecystokinin (CCK): Stimulates gallbladder contraction to release bile.

• Gastrin: Stimulates gastric secretion.