GI Physio

Question 1

Saliva Contains 6

Answer 1

• Hypotonic water secretion
• Electrolytes
• Mucus
• Amylase
• Lysozyme
• Alkaline bicarbonate

Question 2

Parotid Gland

Answer 2

• 25% of saliva
• Largest, near ear
• Affected by Mumps
• Serous secretion units

Question 3

Submandibular Gland

Answer 3

• 70%
• Serous and mucous secretions

Question 4

Sublingual Gland

Answer 4

• 5%
• Serous and predominately Mucous scretions

Question 5

Control of Saliva secretion

Answer 5

• Stimulated by parasympathetic
• Mild activation of Sympathetic inhibits saliva–> dry mouth
• Strong activation of sympathetic causes mild increase in saliva with high amounts of mucous –> foaming at mouth
• Tactile stimulation, food in mouth

Question 6

Regions of Pharynx (Throat) and what passes through

Answer 6

• Common passageway for food, liquid, air
• Nasopharynx
• Oropharynx
• Laryngopharynx
• Food passes through oropharynx and laryngopharynx to esophagus

Question 7

Esophagus general, begins at, enters via, innervated by

Answer 7

• Hollow muscular tube
• Begins posterior to circoid cartilage
• Enters abdominopelvic cavity through esophageal hiatus
• Innervated by fibers from esophageal plexus

Question 8

Esophagus muscle type and sphincters

Answer 8

• Voluntary muscle first 1/3
• Smooth muscle lower 2/3
• Sphincters at each end
  
  • Upper esophageal sphincter keeps air out of stomach during respiration
    
    • Cricopharyngeal muscle
  • Lower esophageal sphincter
    
    • Gastroesophageal sphincter

Question 9

Swallowing 3 phases

Answer 9

• AKA Deglutition
• Initiated voluntarily then continues automatically
• 3 phases
  
  • Buccal
  • Pharyngeal
  • Esophageal

Question 10

Buccal Phase

Answer 10

• Compression of bolus against hard palate
• Bolus assists in elevation of the soft palate
  
  • Sealing off nasopharynx
  • Reflex responses begin and bolus move toward stomach

Question 11

Pharyngeal Phase 3

Answer 11

• Bolus contacts posterior pharyngeal wall
• Bolus passes glottis by elevation of the larynx and folding of epiglottis
• Uvula and soft palate block passage back to the nasopharynx

Question 12

Esophageal Phase 2

Answer 12

• Pharyngeal muscles force bolus into esophagus
• Bolus pushed toward stomach by peristaltic wave

Question 13

Peristalis General def, how many waves

Answer 13

• Wave of relaxation followed by wave of constriction propels food into stomach
• Normally a single wave (primary peristalsis) is enough to move food to stomach

Question 14

If food becomes stuck…

Answer 14

• Stretch receptors activate secondary perstalsis until the food is forced to stomach
• Each wave becomes more forceful

Question 15

Peristalsis Steps

Answer 15

• Contraction of circular muscles behind bolus
• Contraction of longitudinal muscles ahead of bolus
• Contraction in circular muscle layer forces food forward

Question 16

Stomachs 5 regions

Answer 16

• Cardiac
• Fundus
• Body
• Antrum
• Pylorus

Question 17

Stomach Sphincters

Answer 17

• Gastroesophageal sphicnter
  
  • Lets food into stomach
• Pyloric sphincter
  
  • Lets food out of stomach into small intestine

Question 18

Innervation of stomach

Answer 18

• Parasympathetic
• Sympathetic
• Intrinsic (enteric) system

Question 19

What lines stomach

Answer 19

• Simple columnar epithelium lines all portions of stomach
• Epithelium is a secretory sheet
  
  • Produces mucus that covers interior surface
  • Gastric pits, shallow depressions that open onto the gastric surface

Question 20

Histology of Gastric Glands

Answer 20

• Mucous neck cells
  
  • Secrete mucous
• Parietal cells
  
  • Hydrochloric acid
  • Intrinsic factor to absorb VitB12
• Chief cells at base
  
  • Pepsinogen (low pH)–> pepsin
• Enteroendocrine
  
  • Cells in pylorus
  • Serotonin, enhance muscle tone
  • Gastrin, induces more parietal and chief cell function

Question 21

Regulation of Gastric Activity

Answer 21

• Production of acid and enzymes by gastric mucosa
  
  • Controlled by CNS
  • Regulated by short reflexes of the enteric nervous system
  • Regulated by hormones of digestive tract

Question 22

Cephalic Phase

Answer 22

• Sight, smell, taste or thoughts of food
• CNS stimulated–> vagus nerves X
• Submucosal plexus
• Mucous cells
• Chief cells–> pepsinogen
• Parietal –>HCL
• G cells –> Gastrin

Question 23

Gastric phase

Answer 23

• Neural response
• Prescence of food sensed by chemoreceptors and stretch receptors
• Submucosal and myenteric plexuses
  
  • Mixing waves
  • Mucous cells
  • Chief Cells
  • Parietal Cells
  • G cells
• Gastrin–> Chief, parietal, mixing waves

Question 24

Intestinal Phase

Answer 24

• Gastrin is released when a small amount of food enters intestine
• Gastrin is inhibited when larger amounts of food enter intestine

Question 25

Small intestine characteristics

Answer 25

• Longest section
• Complete enzymatic digestion of all foods
• Almost all absorption of nutrients
• Receives pancreatic secretions
• Segmentation and peristalsis

Question 26

Small intestine 3 segments

Answer 26

• Duodenum 10”
  
  • Bile and pancreatic juice enter here
• Jejunum 8”
• Ileum 12”

Question 27

Segmentation in SI

Answer 27

• Local contractions of smooth muscle
• Same muscles as peristalsis but NO propulsion
• Segmented food helps to increase absorption
• Mixes food with digestive juices

Question 28

Modifications for Absorption

Answer 28

• Length
• Circular folds (plicae circulares)
  
  • Permanent folds that increase surface area for absorption
  • Slows the chyme
• Villi
  
  • Can move during digestion
  • Enhance absorptive efficiency
• Microvilli
  
  • Amplify absorptive surface
  • Contain enzymes that complete final stages of digestion
• THERE WILL BE AN EXAM QUESTION ON THIS