Topic 12: Gastrointestinal / Digestive System 1

• What is the primary function of the digestive system?

  Breakdown and absorption of food
• Why is the small intestine considered essential in digestion?

  It breaks down food components for absorption
• What is the gastrointestinal (GI) tract also known as?

  Alimentary canal
• What does the GI tract contain from ingestion to elimination?

  Food until it is digested or eliminated
• What are the organs included in the GI tract?

  Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum
• How long is the GI tract in a living person?

  About 16.5–23 ft.
• What role do accessory digestive organs play?

  Assist in digestion but are not part of the GI tract
• What are the six basic processes of the digestive system?

  1. Ingestion
  2. Secretion
  3. Mixing and propulsion
  4. Digestion
  5. Absorption
  6. Excretion
• What is the process of ingestion?

  Entry of materials into the digestive tract
• What does secretion involve in the digestive system?

  Release of water, acids, enzymes, buffers, and salts
• What is the purpose of mixing and propulsion in digestion?

  Makes materials easier to move along the tract
• What is digestion in the context of the digestive system?

  Chemical breakdown of food into small fragments
• What does absorption refer to in digestion?

  Movement of nutrients across digestive epithelium
• What is excretion in the digestive system?

  Removal of waste products through defecation
• What are the four layers of the gastrointestinal tract wall?

  1. Mucosa
  2. Submucosa
  3. Muscularis
  4. Serosa
• What is the function of the mucosa layer in the GI tract?

  Lines the digestive tract and absorbs nutrients
• What does the submucosa layer contain?

  Connective tissue with blood and lymph vessels
• What is the role of the muscularis layer?

  Facilitates movement through muscular contractions
• What does the serosa layer do?

  Covers the outer surface of the GI tract
• What are the layers of the small intestine wall?

  1. Serosa
  2. Muscle layer
  3. Sub-mucosa
  4. Mucosa
• What is the function of the peritoneum?

  Supports viscera and provides pathways for vessels
• What are the two layers of the peritoneum?

  Parietal peritoneum and visceral peritoneum
• What does the parietal peritoneum line?

  Internal surface of the abdominopelvic wall
• How does the visceral peritoneum differ from the parietal peritoneum?

  It covers abdominal viscera and is poorly localized
• What are peristaltic waves?

  Muscular contractions that move nutrients and waste
• What is the role of peristalsis in digestion?

  Moves a bolus along the digestive tract
• What are the steps of peristaltic motion?

  1. Circular muscles contract behind bolus
  2. Circular muscles relax ahead of bolus
  3. Longitudinal muscles contract ahead of bolus
  4. Wave of contraction forces bolus forward
• What forms the oral cavity?

  Cheeks, palates, lips, and tongue
• What is the composition of the tongue?

  Skeletal muscle covered with mucous membrane
• What are papillae on the tongue?

  Structures that may contain taste buds
• What does lingual lipase do?

  Digests triglycerides in the stomach
• What is the primary function of saliva?

  Lubricates food and starts carbohydrate digestion
• What is the role of mastication in digestion?

  Mixes food with saliva and forms a bolus
• What happens when food is swallowed?

  It passes from the mouth into the pharynx
• What is the structure of the pharynx?

  A funnel-shaped tube composed of skeletal muscle
• What connects the pharynx to the stomach?

  The esophagus
• How does peristalsis function in the esophagus?

  Contracts and relaxes to push food down
• How long does it take for food to travel from mouth to stomach?

  Between 4 and 8 seconds
• What connects the esophagus to the duodenum?

  The stomach
• What are the four main regions of the stomach?

  Cardia, fundus, body, pylorus