Digestion

Question 1

Stomach

Answer 1

○ Surface is composted of columnar epithelial cells
○ Tight junctions prevent leakage across epithelium
○ Mucous neck cells secrete mucus
○ Parietal cells secrete HCL
○ Chief cells secrete the protease pepsin
○ Enteroendocrine cells secrete hormones into the blood
○ Sphincters at the top (aortic) and bottom (pyloric)
○ Very muscular
○ Ridges of muscles on inside called ruggae

Question 2

Small intestine

Answer 2

○ Most important site of digestion
○ Very long
○ Inner surface is very large
○ Divided into 3 sections, the duodenum, jejunum, and ileum
○ Most digestion occurs in the duodenum
§ The duodenum receives bile from the liver and zymogens from the pancreas
□ Zymogens: trypsinogen –> enterokinase –> trypsin
○ Cecum is connected to large intestine

Question 2

Liver’s Role in Digestion

Answer 2

○ Produces bile which is a solution of digestive chemicals and liver waste products, it is stored in the gallbladder
Bile salts emulsify fats and bile ducts open to the small intestine

Question 3

Ghrelin

Answer 3

○ Stimulates NPYRH in hypothalamus –> NPY
○ Stimulates hunger
○ May also increase gastric motility and acid secretion
○ Ghrelin levels are negatively correlated with weight
○ Prader-willi syndrome –> High ghrelin

Question 4

PPY

Answer 4

○ Secreted by colon when full
○ Suppresses appetite
○ Increased from dietary fiber and breaking down of proteins

Question 4

Leptin

Answer 4

○ Secreted by white adipose when lipid content is high
○ Suppresses appetite
○ Leptin sensitivity is decreased in obese people

Question 5

Neuropeptide Y

Answer 5

○ Hypothalamic/pituitary hormone
○ Produced in arcuate nucleus of the hypothalamus
○ Increases appetite and energy stored as fat
○ Co-expressed with agouti-related protein- also stimulates appetite