Physiology

Question 1

What is the pharyngoesophageal sphincter comprised of and what is it’s function?

Answer 1

circular layer of striated muscle; keeps air from entering esophagus & stomach during breathing

Question 2

What is the function of the gastroesophageal (cardiac) sphincter?

Answer 2

controls entrance AND reflux of food; normally tonically contracted when no food is waiting on entrance to stomach; receptive relaxation when food is swallowed & protects against reflux of digested stomach contents

Question 3

What does the esophagus pass through?

Answer 3

The hiatus; weakness allows stomach fundus to protrude back into thoracic cavity’s mediastinum (hiatal hernia)

Question 4

What is tonic contractile activity and what organ parts have it?

Answer 4

• usually found between two organs
• musculature is in a state of stable contraction to occlude lumen
• UES, LES, ileocecal sphincter, internal anal sphincter, proximal stomach, pyloric sphincter

Question 5

What is phasic contractile activity & what organ parts have it?

Answer 5

• periodic contraction lasting a few seconds followed by relaxations often on a cyclical pattern
• esophagus, antrum, SI, colon

Question 6

What are segmenting contractions and which organs/organ parts have it?

Answer 6

• mix chyme w/secretions (like bile or pancreatic enzymes) & bring contents in contact w/mucosa for digestion & absorption
• SI & LI

Question 7

What are haustral contractions and what organs/organ parts have it?

Answer 7

• special kind of segmenting contraction of longer duration; brings contents into contact w/mucosa for water & electrolyte absorption
• occurs in LI

Question 8

What is the primary type of muscle contraction through the GI tract?

Answer 8

Question 9

What can cause increased motility (and increased bowel sounds)?

Answer 9

1) inflammation
2) effect of toxins in/around GI tract
3) unabsorbed materials

Question 10

What can cause decreased motility (and decreased bowel sounds)?

Answer 10

1) ileus
2) obstruction

Question 11

What effect does the SNS have on the GI tract?

Answer 11

• “fight or flight”
• thorocolumnar division
• stimulation will cause a decrease in activity including decreased motility & secretions

Question 12

What effect does the PNS have on the GI tract?

Answer 12

• “rest & digest”
• craniosacral division
• stimulation will cause an increase in activity including increased motility & secretions

Question 13

What are the plexuses of the enteric NS (intrinsic)?

Answer 13

• myenteric (auerbach)
• submucosal (meissner)

Question 14

Where is the myenteric plexus located and what is it’s function?

Answer 14

• located b/t circular & longitudinal muscle layers (in GI tract wall)
• concerned w/ motility

Question 15

What are the functions of the submucosal plexus?

Answer 15

• located in GI tract wall
• controlling the function of each segment of the intestinal tract
• integrates signals from the mucosal layer into local control of motility, intestinal secretions, & absorption of nutrients

Question 16

What factors increase the excitability of smooth muscle contraction?

Answer 16

• stretching smooth muscle (cramping from gas or constipation d/t stretch)
• PNS stimulation (rest & digest)

Question 17

What factors decrease the excitability of smooth muscle contraction?

Answer 17

• SNS stimulation (fight or flight)

Question 18

What is the oral phase of swallowing?

Answer 18

voluntary; bolus collected at back of mouth & tongue can lift food to touch the posterior oropharynx

Question 19

What is the pharyngeal phase of swallowing?

Answer 19

food in pharynx stimulates closure of all pharyngeal openings except esophagus & food is moved to top of the esophagus; UES relaxes then closes after bolus passage

Question 20

What is the esophageal phase of swallowing?

Answer 20

begins once food bolus has passed the UES; vagus nerve stimulates peristaltic contractions & LES relaxation

Question 21

What are the impulses carried for the swallowing reflex & esophageal motility?

Answer 21

• voluntary initiation
• sensory impulses in pharynx & esophagus integrate w/motor impulses from swallowing center in medulla & lower pons
• invol motor impulses for oral & pharyngeal phases carried in CN V, lX, X, & Xll

impulses for esophageal phase carried in CN X

Question 22

What are the two functions of the secretory glands of the GI tract?

Answer 22

1) produce mucous (to lubricate & protect mucosal layer)
2) secrete fluids & enzymes (to aid in digestion & absorption of nutrients)

Question 23

What are the 3 functions of saliva?

Answer 23

1) protection, moisten, & lubrication (mucous)
2) protective antimicrobial action (lysozyme)
3) initiate digestion of starches (ptyalin and amylase)

Question 24

What is the function of mucous secreting cells?

Answer 24

barrier of protection

Question 25

What is the function of parietal cells?

Answer 25

secrete hydrochloric acid (HCl) & intrinsic factor (necessary for B12 absorption)

Question 26

What is the function of chief cells?

Answer 26

secretes pepsinogen which is converted to pepsin when exposed to low pH of stomach

Question 27

What are the functions of gastrin?

Answer 27

stimulate gastric acid & pepsinogen increases gastric blood flow stimulates gastric smooth muscle contraction stimulates growth of gastric and intestinal mucosal cells

Question 28

What is the most common site for a gastric ulcer?

Answer 28

lesser curvature of the stomach

Question 29

What is the function of cholecystokinin?

Answer 29

stimulates CTX of GB, secretion of pancreatic enzymes, slows gastric emptying, inhibits food intake

Question 30

What is the function of secretin?

Answer 30

stimulates the secretion of bicarb-containing fluids by the pancreas & liver

Question 31

What is the secretion of the LI?

Answer 31

mucous

Question 32

What is secreted by the bowels during episodes of inflammation or irritation?

Answer 32

large amounts of water and electrolytes

Question 33

What are the metabolic activities of gut flora?

Answer 33

1) fermentation of undigestible dietary residue & mucous to produce short chain FAs 2) vitamin synthesis & mineral absorption

Question 34

What are the trophic effects of the gut flora?

Answer 34

"grooming" of intestinal epithelial cells

Question 35

What are the protective effects of the gut flora?

Answer 35

protection of the colonized host against invasion by pathogenic organisms

Question 36

What brush border enzymes aid in the digestion of carbs and proteins and where do they adhere?

Answer 36

1) aminopeptidases 2) maltase 3) sucrase 4) lactase - Adhere to the border of the villus structure

Question 37

What is the pathophysiology of carb digestion & absorption?

Answer 37

- begins in mouth w/salivary amylase - pancreatic secretions also contain amylase (breaks starches down into disaccharides) - brush border enzymes convert disaccharides into monosaccharides & then they are absorbed into the bloodstream

Question 38

What is the pathophysiology of fat digestion and absorption?

Answer 38

- large fat gobules (mainly trigs) are broken down into smaller particles (emulsification) by agitation in the stomach & bile from the liver - pancreatic lipase splits trigs into free fatty acids & monoglycerides - bile salts form micelles that transport free FAs & monoglycerides to surface of villi - ultimately transported through lymphatics as chylomicrons - small quantities of short & medium chain FAs are absorbed into the portal blood & fat that is not absorbed is excreted into the stool (steatorrhea)

Question 39

What is the pathophysiology of protein digestion & absorption?

Answer 39

- protein digestion begins in the _stomach w/pepsin_ & proteins are broken down into AA by pancreatic enzymes called _proteases in SI_ - brush border enzymes then break down the proteins into peptides that are 1-3 AAs long - Absorption occurs through _mucosal membrane_

Question 40

What are the functions of the liver?

Answer 40

1) produces bile 2) metabolizes hormones and drugs 3) synthesizes plasma proteins & blood clotting factors 4) stores vitamins & minerals 5) maintains blood glucose levels 6) regulates VLDL levels

Question 41

What are the metabolic functions in regard to carb metabolism?

Answer 41

1) stores excess glucose as glycogen 2) synthesizes glucose 3) converts excess carbs to trigs for storage in adipose tissue

Question 42

What are the metabolic functions of the liver in regard to lipid metabolism?

Answer 42

1) to derive energy from neutral fat (trigs) it needs to be split into glycerol & FAs

Question 43

What are the metabolic functions of the liver in regard to AA metabolism?

Answer 43

- Transaminaton/deamination of AA's --\> ammonia that must be removed quickly & is synthesized into urea and then one of the following occurs: - excretion by kidneys - excretion into intestines & converted back to ammonia by enteric bacteria &brought back to liver [for round 2]

Question 44

What increases ammonia production?

Answer 44

- ingestion of high protein foods - GI bleeding (this process is impaired with advanced liver disease)

Question 45

What is bilirubin a product of?

Answer 45

RBC breakdown

Question 46

What is free biliruben?

Answer 46

unconjugated- insoluble in plasma

Question 47

What is conjugated bilirubin?

Answer 47

soluble constituent of bile

Question 48

What is unobilinogen?

Answer 48

highly soluble substance that is either excreted in feces or absorbed into portal circulation where it is reexcreted into bile or eliminated by kidney

Question 49

What are the 4 major causes of jaundice?

Answer 49

1) excessive RBC destruction 2) impaired uptake of bilirubin 3) decreased conjugation of bilirubin 4) obstruction of bile flow in canaliculi of hepatic lobules, intrahepatic or extrahepatic bile ducts

Question 50

What is prehepatic jaundice and what conditions cause it?

Answer 50

excessive RBC destruction - hemolytic transfusion reaction, hereditary disorders of RBCs, acquired disorders, hemolytic dz of newborn & AI heme anemia

Question 51

What is intrahepatic jaundice and what conditions cause it?

Answer 51

liver damage - decreased bilirubin uptake, decreased bilirubin conjugation, hepatocellular liver damage, drug induced cholestasis

Question 52

What is posthepatic jaundice?

Answer 52

obstruction of bile flow - structural disorders of bile duct, cholelithiasis, congenital atresia of extrahepatic bile duct, bile duct tumors

Question 53

What are the labs to eval hepatobiliary function?

Answer 53

ALT, AST, serum protein, prothrombin time, fibrinogen, coag factors (ll, Vll, lX & X), serum bilirubin, GGT, alkaline phosphates (to look for bile duct disorders)

Question 54

What are the contents of bile?

Answer 54

bile salts cholesterol bilirubin lecithin FAs water electrolytes

Question 55

What is the function of the gallbladder and how is the passage of bile regulated?

Answer 55

products of food digestion (particularly lipids) stimulate the release of GI hormone cholecystokinin (CCK) which stimulates GB contraction passage is regulated by pressure in common bile duct which is regulated by gallbladder

Question 56

What happens after a cholecystectomy?

Answer 56

dilation of the common duct occurs & regulation of flow is controlled by sphincters in the common bile duct

Question 57

What tissue secretes pancreatic juice and what is it composed of?

Answer 57

exocrine tissue (tubuloacinar glands) - pancreatic juice is composed of an alkaline secretion and an enzyme-rich secretion

Question 58

What is included in the enzyme-rich component of pancreatic juice? **T**ell **C**hloe **C**onnor **E**asily **P**aid **L**ona **P**romptly **R**egarding **D**rugs **T**oday

Answer 58

major enzymes of food digestion - enzyme precursors of proteolytic enzymes: trypsin, chymotripsin, carboxypeptidase, & elastase - phospholipase A, lipase - pancreatic amylase, ribonuclease, deoxyribonuclease - tripsin inhibitor (prevents activation of other enzymes)