Ch 9 - Digestive

Question 1

Types of digestion

Answer 1

• intracellular - glucose and fatty acid oxidation
• extracellular - digestion outside of the cell
• mechanical - physical breakdown of large pieces of food
• chemcial - enzymatic cleavage of bonds
• absorption - products into circulatory system

Question 2

Digestive tract

Answer 2

• mouth - pharynx - esophagus - lower esophageal sphincter (cardiac sphincter) - stomach - duodenum - jejunum - ilium - ileocecal valve - cecum - colon - rectum - anus
• accessory organs - pancreas, liver, gallbladder
• controlled by the enteric nervous system
• peristalsis - rhythmic contractions of the gut

Question 3

oral cavity

Answer 3

• mechanical and chemical digestion
• mastication - chewing
• salivary glands produce saliva that has enzymes
  
  • salivary amylase - hydrolize starch
  • lipase - hydrolize lipids
• Form bolus

Question 4

Pharynx

Answer 4

• connects mouth and nasal cavity to esophagus and larynx
• nasopharynx
• oropharynx
• laryngopharynx
• epiglottis blocks larynx (windpipe)

Question 5

Esophagus

Answer 5

• top is skeletal muscle then transition to smooth muscle
• rhythmic swallow is called peristalsis
• emesis - vomiting
• swallowing starts at the upper esophageal sphincter
• pushes to the lower esophageal sphincter
• top under somatic control, bottom under autonomic control

Question 6

Stomach

Answer 6

• fondus, body, pylorus, antrum
• rugae - internal folds
• gastric glands
  
  • mucous cells - produce bicarbonate rich mucus to protect wall
  • chief cells - secrete pepsinogen (inactive pepsin)
  • parietal cells - secrete HCL, activates pepsinogen into pepsin
    
    • also secrete intrinsic factor - glycoprotein that helps absorb vitamin B₁₂
• pepsin - digests proteins by cleaving amino acids after aromatic rings
• gastric juice - HCL and pepsin
• pyloric glands - have G-Cells that secrete Gastrin
  
  • gastrin - induces parietal cells and causes peristalsis
• chyme leaves stomach and enters duodenum through pyloric sphincter
• most absorption occurs in the small intestine NOT the stomach (except EtOH and Aspirin)

Question 7

Duodenum

Answer 7

• CHEMICAL DIGESTION
• minimal absorption
• brush border enzymes - peptidases and disaccharidases
• enteropeptidases - activate accessory organs
• secrete secretin and cholecystokinin (CCK) into bloodstream
• aminopeptidases - remove N terminal amino acid
• di and tri peptides can be absorced across the small intestine wall
• enteropeptidase - activate trypsinogen into trypsin
  
  • also activate procarboxypeptidases A and B

Question 8

secretin

Answer 8

• peptide hormone
• causes pancreatic enzymes to enter duodenum
• help regulate pH, lowering HCl secretion, and increase bicarbonate secretion
• enterogastrone - slows motility through tract

Question 9

cholecystokinin (CCK)

Answer 9

• stimulate release of bile and pancreatic juices
• promote satiety in brain
• bile - bile salts, pigments, cholesterol
  
  • bile salts - hydrophobic and philic areas, bridge aqueous and lipids
    
    • create micelles of fats and cholesterol, increases surface area for lipase to act
• pancreatic juice - enzymes in bicarb alkaline solution
  
  • help digestive enzymes with 8.5 optimal pH

Question 10

Pancreas

Answer 10

• acinar cells - produce pancreatic juice, exocrine (secrete into duct) cells
• bicarbonate rich, alkaline
• pancreatic amylase - carb digestion
• pancreatic peptidases - released in zymogen form
  
  • enteropeptidase - from duodenum and activates trypsin which activates others
• pancreatic lipase
• enter via major and minor duodenal papillae

Question 11

Liver

Answer 11

• bile ducts - connect liver to gallbladder and small intestine
• hepatic portal vein from digestive tract
• excess sugar uptake for glycogen and triacylglycerol storage
  
  • reverse - glycogenolysis, glyuconeogenesis, lipoproteins
• bile production - bile salts, pigments, cholesterol
  
  • pigments - ex. bilirubin - byproduct from hemoglobin breakdown
    
    • attached to protein fro excretion
    • Jaundice
• albumin - produced in liver, maintain oncotic pressure, carrer for drugs and hormone, clotting factors

Question 12

gallbladder

Answer 12

• store and concentrate bile
• Release bile when activated by CCK

Question 13

jejunum and ileum

Answer 13

• absorption of nutrients
• lined with villi
  
  • microvilli to increase surface area
  • villi each have a capillary bed and lacteal (lymphatic channel for fat uptake)
• secondary active transport and facilitated diffusion for nutrient uptake into epithelial cells then diffuse into capillaries
• absorb lipids via lacteals using chylomicrons and the lymphatic system
• absorb vitamins
• absorb water that is secreted into GI tract
  
  • transcellularly (across membranes)
  • paracellularly (between cells)

Question 14

Vitamin Absorption

Answer 14

• absorbed in small intestine
• fat-soluble - (ADEK are fat soluble)
  
  • dissolve into chylomicrons
• Water soluble - B comples and C
  
  • across endothelial cells into plasma

Question 15

Large Intestine

Answer 15

• water absorption - small intestine still absorbs more water
• cecum - colon - rectum
• into via ileocecal valve
• appendix on cecum
• colon - ascending, transverse, descending, sigmoid
  
  • concentrate into feces
• rectum - storage of feces