Physiology

Question 1

L15.1 Fluids and nutrients entering and leaving the GIT

Answer 1

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Question 2

L15.2 Ingestion, digestion, absorption, secretion, and excretion

Answer 2

• Ingestion: food in mouth, mastication, salivary secretions, deglutition
• Digestion: mechanical & chemical breakdown of food into smaller size
• Absorption: nutrients, electrolytes, water from GIT to circulation
• Secretion: mucus, enzymes, buffers, hormones
• Excretion: fecal waste matter via defection

Question 3

L15.3 Epithelial cells: barrier and selective portal for secretion and absorption

Answer 3

• Absorption
  
  • Apical
    
    • ENaC, Na-Nutrient transporter, Na-Cl co-transporter, Na-H anitporter, Cl-HCO3 anitporter
  • Basolateral
    
    • Na-K ATPase, Cl channel, K channel
• Secretion: 7-10L daily; >99% reabsorbed
  
  • Types: saliva, gastric juice, pancreatic juice, bile
  • Function: sufficient digestive enzymes

Question 4

L15.4 Anatomy: cross-section of mucosa; myenteric and submucosal plexi

Answer 4

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Question 5

L15.5 Major digestive hormones and functions

Answer 5

• motilin (M cells)
  
  • increase MMC
  • increase gastric & intestinal motility
• cholecystokinin (CCK)(I cells)
  
  • stimulates gall bladder motility & secretion of bile
  • secretion of chyme from stomach
  • increase pancreatic secretions
  • increase satiety
• gastric inhibitory polypeptide (GIP)(K cells)
  
  • stimulate insulin release
  • inhibit gastric HCl secretion
  • stimulate glucagon secretion
• secretin (S cells)
  
  • decrease gastric HCl secretion
  • increase pancreatic HCO3 secretion
• gastrin (G cells)
  
  • stimulates HCl secretion of pareital cells
  • stimulates histamine release from ECL cells
  • increase gatric mucosa growth
• ghrelin (X cells)
  
  • food intake (hunger)
  • gastric motility
  • increase gastric acid
• glucagon-like peptide (GLP-1)(L cells)
  
  • increase insulin secretion
  • decrease glucagon release
• somatostatin (D cells)
  
  • decrease pancreatic/gastric secretion
  • decrease motility
  • decrease gall bladder contraction
  • decrease nutrient absorption
  • vasoconstrictor
• serotonin (enterochromaffin (EC) cells)
  
  • enhance gut motility & pancreatic secretions
• histamine (enterochromaffin-like (ECL) cells)
  
  • stimulate gastric HCl secretion
  • enhance vascular vasodilation
    *

Question 6

L15.6 Summation of regulatory pathways

Answer 6

• parasympathetic
  
  • increase motility & secretion
  • upper GIT: vagus
  • lower GIT: S2-S4
  • NTs: ACh (contraction) & VIP (relaxes)
  • sensory: receptors detect nausea & distension
• sympathetic
  
  • vasoconstriction, blood vessels, sphincter contraction
  • thoracolumbar; pre-gang at ganglions, post gang on ENS
  • transmitter: NorEpi
  • sensory: nausea, pain

Question 7

L15.7 Endocrine secreting major GI hormones

Answer 7

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Question 8

L16.1 Describe the volume and composition of salivary fluid coming from major salivary glands

Answer 8

• parotid
  
  • serous (low glycoportein, high amylase)
• sublingual
  
  • mixed serous & mucus; mostly mucous (high mucin glycoprotein)
• submandibular
  
  • mixed serous & mucus; mostly serous
• 1-2 liters/day
• pH 7-8 (alkaline)

Question 9

L16.2 Understand how acinar secretions are modified by duct cells to produce the final salivary fluid that enters the buccal cavity

Answer 9

• acinar cells secrete the initial saliva (isotonic)
  
  • initial saliva, osmolarity, Na+, K+, Cl−, and HCO3− concentrations are similar to those in plasma.
• ductal cells modify the initial saliva.
  • transport mechanisms involved in this modification are

Question 10

L16.3 Describe the physiological function of the components of saliva

Answer 10

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Question 11

L16.4

Answer 11

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Question 12

Cholecystokinin