[Biology][Practical-5] Digestive System Physiology Questions

General Discussion
1

DIGESTIVE SYSTEM

  • Salivary glands secrete saliva which contains amylase

  • Exocrine glands are composed of a cluster of secretory cells that collectively form an acinus (plural = acini)

  • Acinus refers to any cluster of cells that resembles a “berry”

  • What causes the conduction stimulantus stimulant to the exocrine cells?

  1. sight and smell
  2. mechanical expansion of the stomach
  • Cite at least 4 digestive hormones
  1. gastrin
  2. ghrelin
  3. cholecystokinin
    glucose dependant insulinotropic polypeptide
  4. secretin
  5. polypeptide YY
  6. somatostatin

  • Gastrin is secreted into the bloodstream to locally activate the release of more stomach acid

  • There is a balance between gastrin and other gut hormones such as secreting and somatostatin, which cause the inhibition of gastrin if the pH is too low

  • Where the digested food moves from the stomach to the duodenum, there is a secretion of more hormones to control this process

  • Gastrin is secreted by G-cells of the gastric antrum and duodenum

  • Gastrin stimulates acid (HCl) secretion from parietal cells and histamine from enterochromaffin-like cells + promotes proliferation of gastric mucosa

  • Pancreatic glands secrete panceratic juice = lipase + protease + amylase

  • Polypeptide YY is secreted by L-cells of the distal small and large intestine

  • PYY inhibits food intake

  • Pancreatic juice digests proteins and fats

  • Bile digests fat globules and forms fat droplets

  • Somatostatin is produced by D cells of the GI tract and pancreas + hypothalamus

  • Gastric cells secrete gastic juices which include HCl and proteases

  • Cholecystokinin (CCK) is secreted by I-cells of duodenum and jejunum and the central nervous system

  • Intestinal glands secrete intestinal juices via crypts of Liberkuhn in the intestinal wall

  • Secretin and cholecystokinin (CCK) will trigger the pancreas and liver to release digestive juices

  • Pancreatic juices contain bicarbonate ions, neutralizing the stomach acids, while the liver produces Bile to emulsify fats.

  • Gastric juice digests proteins

  • Intestinal enzymes digest peptides, glucose, lactose, and maltose

  • GIP is secreted by K-cells of the duodenum and jejunum

  • GIP promotes insulin secretion from β-cells of the pancreas (incretin effect) and stimulates fatty acid synthesis in adipose tissue

  • Secretin is secreted by S-cells of the upper portions of the small intestine

  • The pH of the human stomach is usually 1.5 - 2.0

  • Saliva digests starch and produces maltose

  • Secretin stimulates the secretion of bicarbonate-rich fluids from the duct cells and biliary tract and augments the action of CCK and decreases gastric acid secretion

  • Ghrelin is secreted by:

the A-cells of the gastric fundus
2. other segments of the GI tract
3. hypothalamus

  • CCK stimulates gall bladder and pancreatic enzyme secretions and decreases appetite

  • Ghrelin promotes food intake; promotes gastric motility and stimulates growth hormone secretion

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