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RUSVM Physiology II > GI 4 > Flashcards

GI 4 Flashcards

1
Q

What type of digestion occurs in the forestomach of ruminants or in the cecum/colon of horses

A

Fermentative digestion

Digestive enzymes of microbial origin

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2
Q

The forestomach of the ruminant is lined with _____________________ epithelium

A

Stratified squamous epithelium

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3
Q

What is the true stomach in ruminants?

A

Abomasum

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4
Q

What is the largest compartment of the newborn ruminant stomach?

A

Abomasum

Enlargement of the forestomach occurs after birth

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5
Q

What type of protozoa in the forestomach are _________ and belong to genus _______ and _______________

A

Ciliated; isotricha or entodinium

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6
Q

Describe the ruminal environment

A

Substrate availability : food intake regulates by volume, structure, energy, palatability

Temperature: 0.5 to 1 C above body temp

Fluid: drink water and saliva

pH: 5.5–7

Osmolarity: 260bis>400mOsm/L

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7
Q

What is an example of symbiosis of the ruminant stomach?

A

Waste products of one species serve as a substrate for another

Eg
R.albus digests cellulose –> hexose, but not protein
B.rumincola detests protein –>fatty acid and ammonia

R.albus requires ammonia and fatty acid for growth
R.rumincola requires hexose for growth

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8
Q

What are the layers of the ruminal contents?

A

Gas
Fiber mat
Intermediate zone
Liquid zone

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9
Q

Rumen microbes intake carbohydrates, protein,and lipids to form ?

A

Volatile fatty acid

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10
Q

What enzyme hydrolyzes cellulose, hemicellulose, and pectin?

A

Cellulase (in the rumen)

Polysaccharide to monosaccharide

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11
Q

What must occur in the fore stomach for glucose, monosaccharides, and short chain polysaccharides to be absorbed by the animal

A

Microbe uptake
Glucose- glycolytic pathway -> 2pyruvate, 2NADH, and 2ATP

Anaerobic fermentation digestion to produce volatile fatty acids AKA short chain fatty acid (SCFA)

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12
Q

What are the primary volatile fatty acids

A 
Acetic acid (acetate)
Propionic acid (propionate) 
Butyric acid (butyrate)
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13
Q

What component of plants, that increase with age and ambient temperature of the plant is not digestible?

A

Lignin

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14
Q

________ on the surface of microbes generate peptides

A

Protease

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15
Q

What is the fate of short chain peptides in the microbial cell?

A

Hydrolyzed to amino acids

  • > synthesis of microbes protein
  • > metabolized to VFA and ammonia
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16
Q

Microbes used _______ and __________ to synthesize amino acids

A

Ammonia (NH3) and volatile fatty acids (VFA)

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17
Q

What is required for an amino acid to enter the VFA pathway?

A

Deamination

amino acid –> NH3 + carbon skeleton

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18
Q

Most amino acids following deamination can enter directly into the VFA pathway except for?

A

Branch-chain aa (BCAA)

Eg valine
Leucine
Isoleucine

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19
Q

Most dietary protein undergoes fermentation in the microbes within the rumen. How does the animal meet its protein needs?

A

Microbial proteins

Microbes are washed out of the rumen with rumen fluids to the abomasum and small intestine -> digestion of microbes

Other sources
Ammonia, nitrates, and urea synthesized to protein within rumen

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20
Q

Urea can be recycled to the rumen to produce proteins for the host, what are the two sources of urea?

A

Deamination of endogenous amino acids -> ammonia
Nitrogen absorbed as ammonia from rumen

Liver turns ammonia back to urea which is returned back to the rumen

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21
Q

What enzymes do microorganisms produce for lipid digestion

A

Lipase and phospholipids

Usually rare in plants, but fats are added to diets to increase energy density

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22
Q

What major type of lipid is found in cereal grains, oilseeds, animal fats, and byproduct feeds?

A

Triglycerides

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23
Q

What major lipid if found in forages?

A

Glycolipids

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24
Q

What minor components of most feeds forms cell membranes of animal cells and the surface of milk fat globules

A

Phospholipids

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25
Q

What minor component of diary feeds is a major component of fat supplements

A

Free fatty acids

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26
Q

How are fats hydrolyzed in the ruminant?

A

Microbial lipase

Anaerovibrio lipolytica -> triglycerides

Buyrivibrio fibrisovlens -> phospholipid and glycolpids

27
Q

Microbial lipase hydrolyze fats to ?

A

Glycerol, sugars, and free fatty acids

28
Q

Glycerol and sugars are formed into ______in the rumen microbes

A

Volatile fatty acids

29
Q

Fatty acids released from fatty acids undergo ____________

A

Hydrogenation

Unsaturated fatty acid -> saturated fatty acid
Absorbed in the small intestine

30
Q

What is the ratio of VFA in ruminants

A

Acetic/propionic/butyric acid

High forage (fiber) diet-> 70:20:10

High grain (starch) diets -> 60:30:10

The ratio of acetate is lower in the starch diet but the total about produced is greater than the fiber diet

31
Q

Microbes can synthesize what vitamins

A

C, K , B

32
Q

A ____________ deficiency can be observed when a ruminants diet is suddenly changed from roughage to concentrate

A

B1 (thyamin)

33
Q

A ________ deficiency can be observed in cobalt poor solids or with diets too high in grain

A

B12 (cobalamin)

34
Q

What are the two main mechanisms that VFA are absorbed in the rumen

A

Ionized- require carrier (HCO3-/Ac-antiport)

Non-ionized - diffuse through apical membrane

35
Q

What is rumen acidosis ?

A

Fast-fermentable carbohydrates (starch rich) can lead to increased VFA production –> acids decrease the pH of rumen

VFA have pka of 4.8 => more acid will be in HAc form than Ac-
HAc can diffuse direct through membrane
Less Ac- antiport with HCO3- (less HCO3- to rumen => pH increases)

Acidic pH -> proliferation of lactate-producing bacteria –> lactic acid -> more acidic

36
Q

How is sodium absorbed in the rumen?

A

Na+ channel- Apical (electrochemical gradient)
Na/N exchanger -apical

Na/K ATPase- basolaterally

37
Q

How is chloride reabsorbed into the rumen?

A

Cl-/HCO3- exchanger -apical

Basolateral channel

38
Q

How is potassium absorbed in the rumen?

A

Apical and basolateral channels - high luminal K+ concentration (transepithelial potential difference)

39
Q

How is magnesium absorbed in the rumen?

A

Mg2+ channel

Affected by K+ concentrations

40
Q

How is calcium reabsorbed int he rumen?

A

Not well understood

Apical- probably Ca/H exchanger

Basolateral - Na/Ca exchanger and Ca ATPase

41
Q

What are the functions of the omasum?

A

Concentrate ingesta (absorb water)

VFA (SCFA) absorption - diffusion

Na and Cl absorption (cotransporter)

HCO3- reabsorbed (antiport with Cl-)

42
Q

What are the two mobility patters on the rumen?

A

Mixing (primary)

Erutation (secondary)

43
Q

What are the steps of the mixing/primary contractions of the rumen?

A

Bolus enter rumen to cardia

Biphasic contraction of rumen - weak followed by forceful to push larger particles to dorsal sac

Caudal-moving contraction of dorsal sac pushes ingesta farther back

Cainial-moving contraction of dorsal sac- > mix ingesta and start bacteria fermentation

Smaller particles decant to ventral sac separates big and small material

Ventral sac contraction- smaller particles to over crainial pillar to the crainial sac

Cranial sac contracts -further separates to small and large particles

Recticulum contract, recticulum-omasal orfice relax and small particle go omasum

44
Q

What is the main function of primary contractions of the rumen?

A

Reduce particle size

45
Q

What the the function of secondary contractions of the rumen?

A

Force gas toward the cranial portion of rumen

Occurs at end of primary contraction cycle

46
Q

What are the secondary contractions of the rumen?

A

Cranial-moving contraction staring in cardio-dorsal blind sac

Contraction moves toward cardia forcing gas to esophagus

47
Q

How many recticular-rumen contractions occur per minute

A

1-3

Rate and strength depend on structure of diet

48
Q

What are the main gases produced during rumination?

A

CO2

Methane

49
Q

the ________________center is located in the medulla and receives afferent fibers from mechanoreceptor in the dorsal sac where gas accumulates

A

Eructation

50
Q

What can occur in cattle when the eructation mechanism fails ?

A

Tympanism or bloating

51
Q

What is legume bloat?

A

Cattle eat fast growing clover/alfalfa

Gas trapped in plant material and doesnt rise to dorsal sac

Mechanoreceptor do not detect gas

Eructation mechanism fails

52
Q

When cattle do not have enough oxaloacetate or an excessive amount of acetylCoA, often seen in high-producing dairy cattle, what condition develops?

A

Ruminant ketosis

Acetyl CoA -> acetoacetyl CoA -> ketone bodies (acetoacetate, betahydroxybutyrate, and acetone)

53
Q

What controls reticulorumen motility

A

ENS and vagus nerve

Stretch receptors/chemoreceptor-> afferent to brainstem (dorsal vagus nucelus)->vagus nerve

54
Q

What invagination of the wall of the reticulum spans from the cardia to the recticulo-omasal orfice; it diverts milk away from developing rumen, directly into abomasum

A

Recticular groove (esophageal groove)

55
Q

What closes the reticular groove, so milk bypasss the rumen and directly enters the abomasum

A

Reflex

Anticipate suckling and suckling -> CNS -> brainstem -> vagus nerve -> groove contracts forming a tube

56
Q

Horses and rabbits are ___________ fermenters

A

Hindgut

57
Q

What are the substrates required for hindgut fermentation?

A

Carbohydrates and proteins

58
Q

What is the product of hindgut fermentation

A

Volatile fatty acids

59
Q

What must be controlled to maintain fermentation in the hindgut

A 
Substrate supply
Control of pH
Osmolarity 
Anaerobiosis 
Retain fermentation material 
Remove wastes
60
Q

What is the predominant motility pattern of the cecum? How does this differ from the ventral colon?

A

Cecum: Low-amplitude contractions move ingesta from haustra to haustra (mixing)

Ventral colon: haustra segmentation and retropulsive peristalsis (mixing) and propulsive peristalsis (movement)

61
Q

Carbohydrates digestion in ruminants takes place mostly in the?

A

Forestomach

Almost no digestible carbohydrate enters intestine

62
Q

All the glucose available to ruminants is formed by ________________

A

Gluconeogenesis

63
Q

What volatile fatty acid is the most important precursor for gluconeogenesis of ruminants

A

Propionate

Will enter Krebs cycle as succinate

64
Q

Proprionate is absorbed from the portal blood supply by the _________

A

Liver

Never enters systemic circulation

RUSVM Physiology II (11 decks)

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