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Physiology 2 > 2. GI Part 11 > Flashcards

2. GI Part 11 Flashcards

1
Q

what are the 2 motility patterns in the rumen and what kind of contractions do they have

A
  1. mixing (primary contractions)

2. eructation (secondary contractions)

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2
Q

steps of primary contractions (8)

A
  1. bolus enters rumen and remains suspended in area near cardis (contains air bubbles)
  2. biphasic (double) contractions of reticulum
  3. caudal moving contraction of dorsal sac moves ingesta further back into dorsal sac
  4. cranial moving contraction of dorsal sac mixes ingesta; ingesta now under bacterial fermentation and produces gas; gas accumulates in dorsal sac
  5. smaller particles decant into ventral sac
  6. contraction of ventral sac separates big and small particles; small material goes over cranial pillar into cranial sac
  7. contraction of cranial sac which further separates material into big and small
  8. reticulum contracts – reticulo-omasal orifice relaxes and small particles (dense material) are forced through opening into omasum

then a new cycle starts

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3
Q

describe the biphasic contraction of the reticulum during the primary contractions

A
  1. first contraction is weak

2. second is forceful, nearly obliterating reticulum lumen –> bigger particles pushed to dorsal sac

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4
Q

what is the function of primary contractions

A

reduce particle size of forage

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5
Q

what influences rate of particle passage from rumen and rate of feed intake

A

digestibility of feed

physical characteristics of feed

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6
Q

how many reticulo-rumen contractions occur per minute

A

1-3

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7
Q

when are reticulo-rumen contractions most frequent; when do they dissapear

A

most frequent 00 during eating

disappear – during sleep

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8
Q

what do the rate and strength of contractions depend on

what stimulates the most frequent and strongest contractions

A

rate and strength depend on structure of the diet

coarse, fibrous feeds stimulate the most frequent and strongest contractions

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9
Q

what is the function of secondary contractions

A

force gas toward cranial portion of rumen

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10
Q

when do secondary contractions occur

A

at end of primary contraction cycle

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11
Q

steps (?) of secondary contractions

A
  1. cranial moving contraction starting in the caudal dorsal blind sac
  2. forward moving contractions of the dorsal sac that moves gas toward the cardia; gas will enter the esophagus and can be eructed
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12
Q

function of regurgitation reflex

A

bring large particles from rumen back to mouth so they can be chewed to reduce particle size

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13
Q

steps (?) of regurgitation reflex

A
  1. begins with contraction of mid dorsal rumen –> this pushes gas cap caudally and big particles toward cardia
  2. lower esophageal sphincter relaxes and bolus enters esophagus and is propelled to mouth by antiperistalsis
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14
Q

normal frequency of regurgitation

what % of cows should be chewing cud

A

1 regurgitation every 2-3 minutes

60% of cows in a herd should be actively chewing cud

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15
Q

what are main gases produced during rumination and percentages

A

carbon dioxide – 60-70%

methane – 30-40%

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16
Q

eructation frequency

A

1 per minute

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17
Q

describe eructation center

A

localized in medulla

receives afferent fibers from mechanoreceptors placed in dorsal sac of rumen (where gas accumulates)

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18
Q

where does gas accumulate in the rumen

A

dorsal sac

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19
Q

what is tympanism and when does it occur

A

bloating

occurs when eructation mechanisms fail

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20
Q

causes of tympanism (4)

A
  1. blockage of esophagus
  2. impaired vagal nerve function
  3. rabies
  4. mor typical due to ingestion of legumes
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21
Q

describe legume bloat:
type of pasture that causes it and what they contain
how does gas accumulate
can gas be detected

A

when cattle feed on lush, rapidly growing alfalfa or clover pastures –> contain waxy saponins

gas becomes trapped in tiny bubbles and normal free gas bubble cannot accumulate on top of dorsal rumen sac

presence of gas is not detectable by mechanoreceptors of dorsal sac

22
Q

what controls the reticulorumen motility

A

ENS and vagus nerve

23
Q

what do stretch receptors and chemoreceptors monitor

A

distension, consistency of ingesta, pH, VFA concentration, ions

24
Q

where is the control center for reticulorumen motility located

type of fibers and where they go

A

located in the brainstem – dorsal vagal nucleus

efferent fibers go to rumen with the vagus nerve

25
Q

describe the esophageal groove (reticular groove)

A

a gutter like imagination traversing the wall of the reticulum from the cardia to the reticulo-omasal orifice

26
Q

function of the esophageal groove (reticular groove)

A

diverts milk away from the developing rumen and pas it directly to the abomasum

27
Q

describe esophageal groove (reticular groove) closure

A

reflex action (brainstem impulses arrive through vagus)

afferent stimuli arise from centrally (anticipation of suckling –> cephalic phase) and from the pharynx (suckling)

when stimulated, msucles of the groove contract causing it to twist –> lips of groove close together forming tube form cardia to omasal canal

28
Q

what happens in ruminant ketosis

Normal:
acetate and butyrate –> acetyl CoA –> citrate

A

if oxaloacetate is not enough or if acetyl CoA is excessive (excess fat oxidation) – acetyl CoA accumulates as acetoacetyl CoA which is degraded to acetoacetate, beta-hydroxybutyrate, and acetone (ketone bodies)

29
Q

conditions for maintaining fermentation in the horse

A

similar to those of the rumen

substrate supply, control of pH (buffers), osmolality, anaerobiosis, retention of fermenting material, removal of waste product and residue

30
Q

things to consider when talking about fermentation efficiency in horse (4)

A
  1. ingesta passage through stomach and small intestine before arrival to large intestine –> exposure to gastric acids and digestive enzymes may increase digestion rate in hindgut
  2. some proteins escape small intestine digestion and absorption and arrive to hindgut
  3. there is an extensive urea recycling into the colon and cecum (similar to rumen)
  4. in contrast to ruminant, horses do not have a mechanism to recover and utilize microbial proteins and most pass out in feces
31
Q

what helps rabbits recover microbial proteins

A

cecotrophy

32
Q

who is more efficient – degradation of cellulose

A

ruminats

33
Q

who is more efficient – absorption of VFA

A

ruminants

34
Q

who is more efficient – utilization of microbial protein

A

ruminants

35
Q

who is more efficient – poor food quality

A

horses – eat more and have lower retention time

36
Q

who is more efficient – food is scarce

A

ruminants – more efficient at digesting and absorbing

37
Q

where does most carb digestion occur in ruminants and through what type of digestion

how much digestible carbs enter intestine

A

occurs in forestomach through fermentative digestion

almost no digestible carbs enter intestine

38
Q

where does glucose available to ruminants originate from

what is most important precursor of glucose in ruminants

A

originates from gluconeogenesis

precursor – VFA propionate

39
Q

at what level does propionate enter Krebs cycle

A

succinate

40
Q

what is succinate and what can it lead to

A

4 carbon intermediate

can lead to formation of oxaloacetate which is the entry metabolite for gluconeogenesis

41
Q

special considerations – glucose homeostasis in ruminants (5)

A
  1. ruminants exist in constant state of potential glucose deficiency
  2. gluconeogenesis covers 85-100% of glucose needs
  3. insulin levels are regulated by VFA concentrations
  4. all glucose available to ruminants originates from gluconeogenesis
  5. most important precursor of glucose in ruminants is VFA propionate
42
Q

where is most of propionate absorbed from rumen extracted from

does it ever enter the systemic circualtion

A

almost all the propionate absorbed from the rumen is extracted from the portal blood by the liver and never enters the systemic circulation

43
Q

where are fatty acids synthesized in ruminants

what is used as a precursor

A

fatty acids are only synthesized in adipose tissue using acetate as a precursor – never use glucose

44
Q

what does glucose go to in high producing dairy cows

what do remaining tissues use

A

lactose – milk sugar

remaining tissues function on alternative fuels

45
Q

describe the mouth and esophagus of the bird (3)

A

no soft palate

no teeth

esophagus of large diameter

46
Q

describe the crop

A

storage function

ingesta accumulates once gizzard is full

epithelium is rich in mucus secreting cells

47
Q

describe the proventriculus

A

contains a glandular epithelium

48
Q

describe the gizzard

A

muscular organ for grinding and sieving ingesta

ejection of bone, hair, indigestible material into oral cavity for elimination

49
Q

what do grain eating birds do to aid in grinding of food

A

swallow stones and gravel (grit)

50
Q

describe small intestines of bird

A

short in relation to body size

51
Q

describe ceca in birds

A

paired in some species

in other species they are rudimentary

52
Q

describe rectum in birds

A

ends in cloaca – where digestive, urinary, and reproductive discharges converge

Physiology 2 (11 decks)

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