GI physiology

Question 1

besides mechanical ingestion, what systems are necessary to acquire and ingest food?

Answer 1

sensory

• tactile
• visual
• olfactory
  
  • memory

Question 2

prehension

Answer 2

seizing food and conveying it into the mouth

Question 3

Mastication

Answer 3

mechanical breakdown of food in the mouth

chewing

Question 4

deglutition

Answer 4

swallowing

3 stages:

• through the mouth (voluntary)
• through the pharynx (reflex)
  
  • through esophagus (reflex)

Question 5

segmentation

Answer 5

back and forth mixing due to intermittent contraction of circular smooth muscle

Question 6

peristalsis

Answer 6

unidirectional (usually aboral) waves of contraction

Question 7

propulsive motility

Answer 7

moving bolus aborally

Question 8

retentive motility

Answer 8

material is retained longer

Question 9

mixing motility

Answer 9

material in lumen is churned

Question 10

digestive transit time

Answer 10

timing of getting material from one area to another

short in birds (less digestion of high energy berries)

long in ruminants (30+ hours)

Question 11

digestion vs absorption

Answer 11

digestion is a reduction in size using physical, chemical, and enzymatic breakdown. Aim is to make molecules small enough to be absorbed.

Absorption: transport of nutrient particles into vascular system

Question 12

mechanical digestion

Answer 12

simple decrease in size

mastication

gastric digestion through contractions, mixing

Question 13

enzymatic digestion

Answer 13

hydrolysis of chemical bonds via enzymes produced by alimentary tract or bacteria

Question 14

chemical digestion

Answer 14

hydrolysis of chemical bonds via HCl

mostly in stomach

Question 15

ruminant saliva

Answer 15

buffered solution required to help support rumen microbes buffer acid produced in fermentation

antifoaming characteristics

flow is continuous but varies with activity

Question 16

major digestive enzyme in saliva

Answer 16

salivary amylase

Question 17

maldigestion and malabsorption diseases

Answer 17

share clinical signs but etiologies are different and are treated differently

Question 18

elimination

Answer 18

Production, temporary storage, expulsion of fecal mass

Question 19

detoxification

Answer 19

liver is integral

Question 20

GI bacteria management

all species must:

Answer 20

• prevent bacteria from leaving gut
• maintain correct types of bacteria
• keep colonic bacteria out of small intestine
  
  • provide a good environment for fermentation bacteria

Question 21

GI intrinsic neuronal control

Answer 21

enteric nervous system

component of ANS

controls majority of GI functions independent of CNS

Question 22

intrinsic GI hormones

Answer 22

regulate secretions, not released into lumen

made by alimentary tract

have local and systemic functions (secreted into circulation)

Question 23

extrinsic neuronal control of GI system

Answer 23

parasympathetic: vagus, pelvic n
sympathetic: splanchnic, and hypogastric nerves

only extrinsic gut hormone is aldosterone (water absorption)

Question 24

aldosterone

Answer 24

extrinsic GI hormone that regulates water absorption

Question 25

immune function of the GI system

Answer 25

pathogens can enter GI since its exposed to environment

Question 26

peyer's patches

Answer 26

immune surveillance of intestinal lumen facilitate immune response in gut especially in ileum

Question 27

paneth cells

Answer 27

secrete antimicrobial peptides and proteins in gut

Question 28

luminal phase of digestion

Answer 28

within the lumen of the GI tract varies in region of GI tract (chemical, physical, and chemical) mouth through at least small intestine enzymes produced by the organ itself, accessory organs, and/or hosted microbes

Question 29

luminal digestion produces:

Answer 29

short chain polymers that are still to big to be absorbed in ruminant and equine symbiotic bacteria can produce some absorbable products

Question 30

mucosal phase of digestion

Answer 30

only in small intestine enteric enzymes further digest end products of luminal digestion absorbable products

Question 31

intracellular phase of digestion

Answer 31

only in small intestine important only for protein

Question 32

short GI reflexes

Answer 32

from gut directly back to gut named from origin to destination (ex gastrocolic) usually affect motility or secretion

Question 33

long GI reflexes

Answer 33

from gut to spinal cord or brainstem the back to gut ex: defecation, vomiting

Question 34

starch

Answer 34

repeting units of glucose highly digestible

Question 35

cellulose

Answer 35

repeating units of glucose not digestible without microbial flora

Question 36

hindgut fermenters

Answer 36

horse large intestine is modified to host microbes and support fermentation microbial mass passed out in feces

Question 37

foregut fermenters

Answer 37

ruminants stomach modified to host fermentative microbes