Chapter 7: The Digestive System Overview

Mucosa

Innermost G.I. tract lining with epithelial layer.

Epithelium

Stratified squamous in mouth; simple columnar in stomach.

Submucosa

Areolar connective tissue, highly vascular for nutrition.

Muscularis externa

Thick double layer of smooth muscle for motility.

Peristalsis

Movement of food along G.I. tract.

Segmentation

Churning of food in one location.

Serosa

Thick fibrous tissue providing structure and protection.

Autonomic Nervous System

Controls G.I. tract function via intrinsic and extrinsic pathways.

Intrinsic Nervous System

Nerve plexus regulating G.I. tract functions locally.

Extrinsic Nervous System

Long pathways from brainstem regulating digestion.

Parasympathetic Nervous System

Stimulates digestion and salivary secretion.

Sympathetic Nervous System

Suppresses digestion and salivary secretion.

Peritoneum

Double-walled serous membrane surrounding G.I. tract.

Salivary Glands

Three pairs producing saliva for digestion.

Saliva

99.5% water; contains ions and digestive enzymes.

Deglutition

Swallowing process, initially voluntary then involuntary.

Rugae

Interior stomach folds increasing surface area.

Parietal Cells

Secrete HCl and intrinsic factor for vitamin B12.

Chief Cells

Secrete pepsinogen and gastric lipases for digestion.

Enteroendocrine Cells

Secrete hormones, including gastrin for digestion.

Chyme

Liquid food mixture entering the duodenum.

HCl Formation

Stimulated by acetylcholine, gastrin, and histamine receptors.

Pancreas

Endocrine and exocrine functions; secretes digestive enzymes.

Hepatocytes

Liver cells that synthesize bile and regenerate.

Bile

Fluid that emulsifies fats, secreted into duodenum.

Liver Functions

Includes metabolism, bile synthesis, and vitamin storage.