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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
How are the different layers in the rumen content generated
Different material density
26
Where is the largest microbial activity in the rumen and why
Boundary between fiber mat and water layer because microbes prefer a more anaerobic area
27
What is bloat
Form of indigestion marked by excessive accumulation of gas in rumen
28
Bloat is a failure of what
To clear cardia due to foaming ingesta, foaming prevents typical layer structure ingesta in rumen
29
What does bloat due to respiratory rate, heart rate and organ perfusion
Decreases respiratory rate because compressing diaphragm, decrease HR and decrease organ perfusion
30
What determines particle size and its reduction rate
Digestibility, microbial action, mastication and physical properties of ingesta
31
Break down of poorly digestible fibers takes __
Longer
32
Rumen volume is limited therefore intake rate can’t exceed ___
Outflow rate
33
Poorly digestible feed takes longer/has longer ___ and is associated with ___intake
Transit time and is associated with less intake
34
Would grinding poorly digestible fiber increase dry matter intake
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
How does increase VFA affect activity of microbes
Negatively impacts because microbial enzymes require certain pKa’s to function so decrease pH can decrease their activity
36
How does the rapid passage of feed affect VFA production
Reduces
37
How does smaller particle size influence mastication and saliva
Requires less mastication and therefore less saliva produced, which means less water, buffer, and urea via saliva provided to the rumen Acidosis
38
What determines dilution rate
Water influx to the rumen
39
What are the sources of water to the rumen
Drinking, saliva, water in feed
40
What does saliva production depend on
Chewing time and feed type
41
How does a high roughage diet affect mastication and saliva
Increases both
42
How does a highly digestible feed affect mastication and saliva
Decreases both
43
Water is importantly for __sorting, __ and transport of solids and ___yield from rumen to omasum
Particle sorting, fermentation, and microbial yield
44
A __ dilution rate would cause more rapid removal of microbes
Higher
45
A higher dilution rate can stimulate __growth if sufficient substrate is available
Microbial
46
Microbial action of ___ bacteria would be reduced as a result of paid passage of fluid
wanted bacteria like VFA producing
47
Dilution rate can positively and negatively affect ___ production and ___ yield
VFA production and microbial yield
48
Is there a sequence of cephalic, gastric, and intestinal phase of secretion in ruminants
No because digesta flows continuously from rumen to abomasum which is associated with continuous secretion from stomach and pancreas and saliva production
49
What PNS nerve controls motility
Vagus
50
What do afferent signals/receptors communicate about motility
Distention, ingesta, consistency, pH, VFA, concentration, ionic strength
51
What nucleus in brain is necessary for normal motility
Dorsal motor nucelus
52
Where are motility stretch receptors located
Wall and pillar of rumen
53
How do stretch receptors control motility
Moderate distention causes increase motility
54
How do stretch receptors respond to severe distention like bloat
Can’t compensate, insufficient force produced by rumen wall
55
How do tension receptors control motility
Measure tension force generated by rumen wall muscles. Rumen mat provides different resistance
56
What is the normal rumen pH
5.5-6.8
57
How do VFA’s affect motility
Decrease pH which reduces motility
58
How do chemoreceptors control motility
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
How do chemoreceptors work in abomasum
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
Afferent signals from ___ and __ nerve affect motility and generate normal motility patterns
Dorsal motor nucleus and vagus nerve
61
What is Hoflund syndrome
Damage to the vagal innervation removes or causes erratic motility patterns Fatal
62
What is reticuloperitonitis
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
How can we treat reticuloperitonitis
Use magnets to trap objects

Physiology III (34 decks)

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