Digestive System Anatomy and Function

Muscularis

  • The muscularis layer of the digestive tract is responsible for contracting and relaxing, which moves food forward.
  • It is composed of smooth muscle.

Layers of the Digestive Tract

  • The main layers are:
    • Mucosa
    • Submucosa
    • Muscularis
  • The muscularis layer is responsible for moving food through the digestive tract.
  • Serosa is the outermost layer.

Enteric Nervous System (ENS)

  • Controls and regulates the digestive system.
  • Extends from the esophagus to the anus.
  • Two components:
    • Myenteric nerve plexus: Involved in gut motility (movement).
    • Submucosal plexus: Involved in the regulation of blood flow.

Peritoneum and Mesenteries

  • Peritoneal cavity: Houses abdominal organs like the stomach, small intestine, and large intestine.
  • Mesenteries: Layers of the peritoneum that suspend and hold digestive organs within the abdominal cavity.
    • Anchor the organs to the abdominal wall.
    • Consist of vessels, nerves, and lymphatic nodes.

Greater Omentum

  • A portion of the mesentery.
  • Extends from the greater curvature of the stomach.
  • Hangs down over the small intestine like an apron.

Mesocolon

  • Fixes the colon to the posterior abdominal wall.

Lesser Omentum

  • Extends from the lesser curvature of the stomach to the liver.

Digestive System Organs

  • Stomach: Has a greater and lesser curvature.
  • Liver: Dark brown organ.
  • Gallbladder: Green organ.
  • Esophagus: Leads down to the stomach.

Mouth and Salivary Glands

  • Salivary glands secrete enzymes to begin breaking down macromolecules (carbs, lipids, proteins).
  • The digestion of carbohydrates starts in the mouth with the enzyme amylase.
  • Amylase breaks down carbohydrates into smaller pieces for effective digestion and absorption.
  • Catabolism: Breaking down complex molecules into simpler ones.
  • Anabolism: Building up from simple to complex.

Saliva

  • Mostly water, but also contains mucus and enzymes.
  • Enzyme: Amylase, which breaks down starch (a complex carbohydrate).
  • Lipase is present but less active in the mouth.

Salivary Glands

  • Sublingual glands with sublingual ducts.
  • Submandibular glands.
  • Parotid glands.
  • Secrete amylase to break down starch (complex carbohydrates).

Digestive System Responsibility

  • The respiratory, digestive, urinary, and the reproductive system.