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Anatomy Lecture Notes

Anatomy of the Digestive System

  • The digestive system is crucial for:
    • Nutrient intake
    • Food digestion
    • Nutrient absorption into body tissues
    • Waste elimination
  • Structures include:
    • Mouth (oral cavity)
    • Pharynx (throat)
    • Esophagus
    • Stomach
    • Liver
    • Gallbladder
    • Pancreas
    • Small intestine
    • Large intestine

Digestion Process

Mouth

  • First site of digestion.
  • Teeth break down food via chewing (mastication).
  • Saliva contains amylase, a digestive enzyme that breaks down carbohydrates.
  • The tongue aids mastication by pressing food against teeth.
  • Chewed food is then swallowed.

Pharynx

  • Also known as the throat.
  • Serves as a passageway for food, water, and air.
  • Food passes from the pharynx to the esophagus.

Esophagus

  • A long tube connecting the pharynx to the stomach.
  • Function: transports food.
  • Lined with smooth muscle.
  • Peristalsis (rhythmic smooth muscle contractions) propels food along.

Stomach

  • Both ends close off upon food entry.
  • Churns food to break it down manually.
  • Stomach acids (e.g., hydrochloric acid, pepsin) further digest food.
  • The pylorus (bottom of the stomach) opens to allow food to enter the small intestine.

Small Intestine

  • Major site of nutrient absorption.
  • Accessory organs (liver, gallbladder, pancreas) aid digestion.

Accessory Organs

Liver
  • The heaviest internal organ.
  • Mainly detoxifies blood by filtering harmful substances.
  • Aids digestion by producing bile, which emulsifies fats.
Gallbladder
  • Stores bile produced by the liver until needed.
  • Empties bile into the small intestine through the bile duct, connected to the duodenum.
Pancreas
  • Creates pancreatic juice to digest proteins, lipids, and carbohydrates.
  • Empties substances into the small intestine through the bile duct.

Duodenum

  • First section of the small intestine.
  • The last section where food digestion takes place.
  • Bile and pancreatic juice mix with food.
  • Peristalsis moves food into the jejunum.

Jejunum

  • Middle portion of the small intestine.
  • The major site of nutrient absorption.

Ileum

  • Final section of the small intestine.
  • Final absorption occurs here.
  • Food moves into the large intestine.

Large Intestine

  • Two primary functions:
    • Water absorption
    • Waste elimination
  • Water absorption occurs as feces move through; too much absorption leads to constipation, too little leads to diarrhea.
  • Sections: ascending colon, transverse colon, descending colon, and sigmoid colon.
  • Feces enter the rectum from the sigmoid colon, ready for elimination.