lecture 10

• What are the learning objectives of the digestive system lecture?

  Know anatomy, structure, and roles in digestion
• What are the fundamentals of the digestive system?

  • Take in food
  • Break food into nutrient molecules
  • Absorb nutrient molecules
  • Rid body of indigestible remains
• What are the main components of the GI tract?

  Mouth, pharynx, oesophagus, stomach, intestines
• What are the accessory organs of the digestive system?

  • Teeth
  • Tongue
  • Gallbladder
  • Salivary glands
  • Liver
  • Pancreas
• What are the 6 activities of the digestive system?

  1. Ingestion
  2. Mechanical breakdown
  3. Propulsion
  4. Digestion
  5. Absorption
  6. Defecation
• What is the innermost layer of the GI tract called?

  Mucosa
• What is the function of the mucosa in the GI tract?

  Secretes enzymes, absorbs nutrients, protects
• What type of cells primarily make up the epithelium of the mucosa?

  Simple columnar epithelial cells
• What is the role of the muscularis mucosae?

  Allows local contractions in the GI tract
• What is the function of the submucosa layer?

  Contains nerve fibers, blood, and lymph vessels
• What is the primary function of the muscularis externa?

  Responsible for peristalsis and segmentation
• What is the outermost layer of the GI tract called?

  Serosa
• What is peristalsis?

  Wave-like muscle contractions moving food
• What is segmentation in the digestive system?

  Mixing of food in the small intestine
• What type of epithelium lines the walls of the mouth?

  Stratified squamous epithelium
• What is the role of saliva in digestion?

  Moistens food and begins chemical digestion
• Which glands produce most of the saliva?

  Extrinsic glands
• What are the key digestive enzymes found in saliva?

  Amylase and lingual lipase
• What is the function of the pharynx in digestion?

  Moves food from mouth to oesophagus
• What are the two phases of swallowing?

  Buccal phase and pharyngeal-oesophageal phase
• How long is the oesophagus?

  About 25 cm long
• What prevents food from moving backwards in the oesophagus?

  Cardiac sphincter
• What is chyme?

  Slurry of mixed food, saliva, and gastric juice
• What does the stomach secrete to aid digestion?

  Gastric juice containing HCl and pepsin
• What is the primary function of the small intestine?

  Major site for digestion and absorption
• What are the three parts of the small intestine?

  Duodenum, jejunum, ileum
• What is the role of bile in digestion?

  Emulsifies fats for digestion
• What is the total surface area of the small intestine?

  Approximately 200 m²
• What are the structural modifications of the small intestine that increase surface area?

  • Circular folds
  • Villi
  • Microvilli
• What is the function of the large intestine?

  Absorbs water and stores residues
• What type of epithelium is found in the large intestine?

  Simple columnar epithelium
• What is the peritoneum?

  Largest serous membrane in the body
• What is the role of the enteric nervous system?

  Regulates digestive processes autonomously
• How many enteric neurons are in the enteric nervous system?

  More than 100 million
• What are the two intrinsic nerve plexuses of the enteric nervous system?

  • Submucosal nerve plexus
  • Myenteric nerve plexus
• What are short reflex arcs in the enteric nervous system?

  Local integration of sensory input and motor output
• What do long reflex arcs involve?

  CNS integration and extrinsic autonomic nerves
• What are the key enzymes secreted by the pancreas?

  • Proteases: Breakdown proteins
  • Amylase: Breakdown starch
  • Lipases: Breakdown fats
  • Nucleases: Breakdown nucleic acids
• What are the mechanisms of digestion and absorption?

  • Digestion: Catabolic process breaking food into monomers
  • Absorption: Moving substances from GI tract into the body
• What is hydrolysis in digestion?

  • Enzymatic degradation of food using water