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Physiology III > Lecture 27: Forestomach Motility > Flashcards

Lecture 27: Forestomach Motility Flashcards

1
Q

What are the 3 things create a favorable environment for microbial fermentation

A
  1. Continuous substrate supply
  2. Appropriate and constant temperature, sufficient time and space, pH control
  3. Removal of indigestible waste, microbes, VFA
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2
Q

What 2 components facilitate selective retention

A
  1. Specific forestomach morphology
  2. Motility patterns
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3
Q

What is selective retention

A

Retain actively fermented material and remove waste

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4
Q

What type of epithelium is in the forestomach

A

Stratified squamous

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5
Q

What are the 3 surface extensions throughout the forestomach

A
  1. Honeycomb folds in reticulum
  2. Rumen papillae
  3. Omasal laminae
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6
Q

What is the purpose of the surface extensions

A

Increase surface area to retain VFA, electrolytes, water to be absorbed in rumen and omasum

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7
Q

What separates the cranial and ventral sac of the rumen

A

Cranial pillar

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8
Q

What connects the omasum to the reticulum

A

Reticulo-omasum orifice

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9
Q

What are the 3 motility patterns of reticulum and rumen

A
  1. Mixing
  2. Eructation
  3. Rumination
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10
Q

What happens during mixing pattern

A

Reticulum and rumen facilitate mixing via contraction cycle

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11
Q

What is the contraction cycle in the mixing pattern

A
  1. 1st recticular contraction mixes fresh material to send to rumen
  2. Contraction of the cranial pillar and reticulum moves food to dorsal sac
  3. Dorsal sac contracts followed by ventral sac
  4. Ventral sac contracts and cranial pillar relaxes and moves dense material to reticulum
  5. Second reticular contraction evacuates dense particles through ROO
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12
Q

What happens to the non-sedmented material, small particles that do not move through ROO

A

Regurgitated as cud

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13
Q

Describe the path of a single bolus

A
  1. Initial chewing and some mechanical/mastication and chemical breakdown with
  2. Ingesta arrives in reticulum and transported via mixing contractions to rumen
  3. Ventral caudal sac spills material with smallest particles to cranial ventral sac to reticulum
  4. Reticulum contraction forces material through ROO to omasum
  5. 1-3 cycles per minute
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14
Q

How do contraction cycles change during feeding

A

Increase

lower during resting

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15
Q

What is eructation

A

Removal of gases

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16
Q

Describe the process of eructation

A
  1. Cranial pillar remains solid and retains solid digesta in rumen
  2. Dorsal sac contracts caudal to cranial and moves gas cap forward
  3. Reticulum and cranial sac relax and
  4. Cardia opens and gas enters esophagus
  5. Ventral sac contracts and cranial pillar relaxes to move dense material into cranial sac and secondary contraction cycle concludes
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17
Q

What is rumination

A

Reduction of particle size via mastication and salivation

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18
Q

What are the 4 important components of rumination

A
  1. Regurgitation
  2. Mastication
  3. Salivation
  4. Deglutition
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19
Q

How does mastication help in rumination

A
  1. Breaks down cell wall and structures making it easily digestible
  2. Stimulates saliva production
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20
Q

How does regurgitation occur

A
  1. LES/cardia relaxes
  2. Inspiratory excursion of thorax
  3. Glottis remains closed
  4. Reversed esophageal peristalsis
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21
Q

Why do ruminants always rest in sternal recumbency

A

To maintain layer structure of rumen which is essential for normal motility and removal of gas cap

Need gravity for floatation and sedimentation of rumen digesta

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22
Q

What is the normal layering in the rumen

A
  1. Gas cap on top
  2. Fiber mat floating on water layer
  3. High density sedimented material
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23
Q

Why does unfermented and digestible material float

A

Plants contain lots of air that makes them less dense

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24
Q

What separates the sediments and floating fiber mat

A

Liquid layer

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25
Q

How are the different layers in the rumen content generated

A

Different material density

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26
Q

Where is the largest microbial activity in the rumen and why

A

Boundary between fiber mat and water layer because microbes prefer a more anaerobic area

27
Q

What is bloat

A

Form of indigestion marked by excessive accumulation of gas in rumen

28
Q

Bloat is a failure of what

A

To clear cardia due to foaming ingesta, foaming prevents typical layer structure ingesta in rumen

29
Q

What does bloat due to respiratory rate, heart rate and organ perfusion

A

Decreases respiratory rate because compressing diaphragm, decrease HR and decrease organ perfusion

30
Q

What determines particle size and its reduction rate

A

Digestibility, microbial action, mastication and physical properties of ingesta

31
Q

Break down of poorly digestible fibers takes __

A

Longer

32
Q

Rumen volume is limited therefore intake rate can’t exceed ___

A

Outflow rate

33
Q

Poorly digestible feed takes longer/has longer ___ and is associated with ___intake

A

Transit time and is associated with less intake

34
Q

Would grinding poorly digestible fiber increase dry matter intake

A

Yes temporarily but VFA and lactate production will increase, decreasing pH which provides advantage to lactate producing bacteria but disadvantages to cellulolytic, hemicelulolytic and pectinolytic species

35
Q

How does increase VFA affect activity of microbes

A

Negatively impacts because microbial enzymes require certain pKa’s to function so decrease pH can decrease their activity

36
Q

How does the rapid passage of feed affect VFA production

A

Reduces

37
Q

How does smaller particle size influence mastication and saliva

A

Requires less mastication and therefore less saliva produced, which means less water, buffer, and urea via saliva provided to the rumen

Acidosis

38
Q

What determines dilution rate

A

Water influx to the rumen

39
Q

What are the sources of water to the rumen

A

Drinking, saliva, water in feed

40
Q

What does saliva production depend on

A

Chewing time and feed type

41
Q

How does a high roughage diet affect mastication and saliva

A

Increases both

42
Q

How does a highly digestible feed affect mastication and saliva

A

Decreases both

43
Q

Water is importantly for __sorting, __ and transport of solids and ___yield from rumen to omasum

A

Particle sorting, fermentation, and microbial yield

44
Q

A __ dilution rate would cause more rapid removal of microbes

A

Higher

45
Q

A higher dilution rate can stimulate __growth if sufficient substrate is available

A

Microbial

46
Q

Microbial action of ___ bacteria would be reduced as a result of paid passage of fluid

A

wanted bacteria like VFA producing

47
Q

Dilution rate can positively and negatively affect ___ production and ___ yield

A

VFA production and microbial yield

48
Q

Is there a sequence of cephalic, gastric, and intestinal phase of secretion in ruminants

A

No because digesta flows continuously from rumen to abomasum which is associated with continuous secretion from stomach and pancreas and saliva production

49
Q

What PNS nerve controls motility

A

Vagus

50
Q

What do afferent signals/receptors communicate about motility

A

Distention, ingesta, consistency, pH, VFA, concentration, ionic strength

51
Q

What nucleus in brain is necessary for normal motility

A

Dorsal motor nucelus

52
Q

Where are motility stretch receptors located

A

Wall and pillar of rumen

53
Q

How do stretch receptors control motility

A

Moderate distention causes increase motility

54
Q

How do stretch receptors respond to severe distention like bloat

A

Can’t compensate, insufficient force produced by rumen wall

55
Q

How do tension receptors control motility

A

Measure tension force generated by rumen wall muscles. Rumen mat provides different resistance

56
Q

What is the normal rumen pH

A

5.5-6.8

57
Q

How do VFA’s affect motility

A

Decrease pH which reduces motility

58
Q

How do chemoreceptors control motility

A

Sense pH which is decreased by VFA’s and motility is reduced, this helps slow down fermentation until enough material is removed from rumen

59
Q

How do chemoreceptors work in abomasum

A

Senses pH drop below 2-3 which stimulates rumen motility to advance waste to omasum.

Feedback mechanism from abomasum to rumen o signal that more food can be digested to abomasum

60
Q

Afferent signals from ___ and __ nerve affect motility and generate normal motility patterns

A

Dorsal motor nucleus and vagus nerve

61
Q

What is Hoflund syndrome

A

Damage to the vagal innervation removes or causes erratic motility patterns

Fatal

62
Q

What is reticuloperitonitis

A

Aka hardware disease

Sharp object trapped in reticulum and contractions can cause object to penetrate through reticulum wall causing leakage of ingesta and bacteria into peritoneal cavity

63
Q

How can we treat reticuloperitonitis

A

Use magnets to trap objects

Physiology III (34 decks)

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