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Flashcards

Digestive Physiology Source Information

J Wellington Inglês 59 flashcards

interior of rumen in sheep

Flashcards do conjunto (59)

  1. 1Ruminants-have four stomach compartments, occupying 3/4ths of the abdominal cavity, filling all of the left side and extending to the right.
  2. 24 Stomach Compartments-Rumen
    -reticulum
    -omasum
    -abomasum
  3. 3Reticulumlies against the diaphragm and is joined to the rumen by a fold of tissue. Could be considered a "cranioventral sac" of the rumen; for example ingesta flows freely between these two organs. Connected to the spherical omasum by a short tunnel
  4. 4RumenThe largest of the forestomaches, is sacculated by muscular pillars into what are called the dorsal, ventral, caudodorsal, and caudoventral sacs.
  5. 5The abomasumthe ruminant's true or glandular stomach. Very similar to the stomach of monogastrics
  6. 6Reticulum and omasuminterior to the rumen, covered exclusively with stratified squamous epithelium similar to the esophagus. Each organ has distinctive mucosa structure.
  7. 7interior of rumen in sheepThe interior surface forms numerous papillae that vary in shape and size from short and pointed to long and foliateinterior of rumen in sheep
  8. 8Reticular epithelium- sheepreticular epithelium- thrown into folds that form polygonal cells that give it a reticular, honey-combed appearance. Numerous small papillae stud the interior floors of these cellsReticular epithelium- sheep
  9. 9Omasum- sheepInside the omasum is thrown into broad longitudinal folds or leaves reminiscent of the pages in a book (a lay term for the omasum is the "book"). The omasal folds which in life are packed with finely ground ingesta have been estimated to represent roughly one-third of the total surface area of the forestomachs
  10. 10Omasum sheep- imageOmasum sheep- image
  11. 11Ruminant Speciesanatomically featured by cattle, sheep, and goats. Other species are called ruminants but have slightly different forestomach anatomy.
  12. 12camelidsspecies: camels, llamas, alpacas, vicunas
    Have reticulum with areas of gland like cells, with an omasum that is tubular and almost indistinct. Occasionally referred to as pseudo ruminants or having "three stomachs" rather than four
  13. 13Stratified, squamous epitheliumsuch as those found in the rumen is not usually considered an absorptive type of epithelium.
  14. 14ruminal papillaevery richly vascularized and the abundant volatile fatty acids produced by fermentation are readily absorbed across the epithelium
  15. 15venous bloodvenous blood from the forestomachs and abomasum carries the absorbed nutrients into the portal vein, straight to the liver
  16. 16Rumen "definition"a fermentation vat par excellence providing anaerobic environment, constant temperature and pH, and good mixing. Well masticated substrates are delivered through the esophagus on a regular schedule and are either absorbed in the rumen or flow out for further digestion and absorption downstream
  17. 17Ruminants diet evolutionruminants evolved to consume and subsist on roughage- grasses and shrubs build of cellulose.
  18. 18esophageal orificepassage through which feed, water, and saliva are delivered to the reticulorumen
  19. 19what objects fall into reticulum or enter rumen proper?Heavy objects- grain, rocks, nails, etc. fall into the reticulum
    light objects- grass, hay, etc. enter the rumen properly. a mixture of voluminous quantities of gas are produced during fermentation
  20. 20saliva productionruminants produce prodigious quantities of saliva
    -cows range from 100-150 L of saliva a day
    -Saliva serves to lubricate, as provision of fluid for the fermentation vat, and as alkaline buffering (saliva is rich is in bicarbonate which buffers the large quantity of acid produced in the rumen and is probably critical for maintenance of rumen pH)
  21. 21Primary zones based on specific gravitymaterials in the rumen partition into 3 zones. Gas fills the upper regions, grain and fluid saturated roughage sink to the bottom, and newly arrived roughage floats in the middle layer
  22. 22rate flow of solid material through the rumenrate of flow of material through the rumen is quite slow and dependent on its size and density. Water flows through the rumen rapidly and appears to be critical in flushing particulate matter downstream
  23. 23fermentation processfeedstuffs are reduced to smaller and smaller sizes and microbes constantly prolifeate. Ruminal Contractions constantly flush lighter solids back into the rumen. The smaller and more dense materials tend to be pushed into the reticulum and cranial sac of the rumen, from which it is ejected with microbe-laden liquid through the reticulo-omasal orifice into the omasum
  24. 24Omasum functionabsorbs residual volatile fatty acids and bicarbonate. The tendency is for fluid to pass rapidly through the omasal canal, but for particulate matter to be retained between omasal leaves for passage into the abomasum
  25. 25abomasumtrue, glandular stomach which secretes acid and otherwise functions very similarly to the stomach of a monogastric. It has a need to process large masses of bactera. The abomasum secretes lysozyme.
  26. 26lysozymean enzyme that efficiently breaks down bacterial cell walls
  27. 27Difference between adult ruminants and you ruminantsfor the first month or so of life the ruminant is functionally a monogastric. The forestomachs are formed, but are not yet fully developed. if milk is induced to the rumen it would rot, not be fermented.
  28. 28Prevention of rotting milk in the rumenTo avoid this problem in young ruminants, suckling causes a reflex closure of muscular fold that form a channel from the esophageal orifice toward the omasum, shunting milk away from the rumen and straight toward the stomach where it can be curdled by rennin and digested enzymatically
  29. 29omasumthe esophageal groove
  30. 30renninChymosin, known also as rennin, is a proteolytic enzyme related to pepsin that synthesized by chief cells in the stomach of some animals.
  31. 31role of renninIts role in digestion is to curdle or coagulate milk in the stomach, a process of considerable importance in the very young animal. If milk were not coagulated, it would rapidly flow through the stomach and miss the opportunity for initial digestion of its proteins.
  32. 32Reticuloruminal motilityAn orderly pattern of ruminal motility is initiated early in life and, except for temporary periods of disruption, persists for the lifetime of the animal. These movements serve to mix the ingesta, aid in eructation of gas, and propel fluid and fermented foodstuffs into the omasum. If motility is suppressed for a significant length of time, ruminal impaction may result.
  33. 33Motility contractionsA cycle of contractions occurs 1 to 3 times per minute. The highest frequency is seen during feeding, and the lowest when the animal is resting.
  34. 342 types of reticuloruminal contractionsPrimary contractions
    Secondary contractions
  35. 35Primary contractionsoriginate in the reticulum and pass caudally around the rumen. This process involves a wave of contraction followed by a wave of relaxation, so as parts of the rumen are contracting, other sacs are dilating.
  36. 36secondary contractionsoccur in only parts of the rumen and are usually associated with eructation.
  37. 37How is rumen motility controlledThe forestomachs possess a rich enteric nervous system, but coordinated contractions require central input. Motility centers in the brainstem control both the rate and strength of contraction via vagal efferents. Cutting the vagus nerve in a ruminate abolishes coordinated reticuloruminal motility. There are also vagal afferents from the rumen to the motility centers which allow stretch receptors and chemoreceptors in the rumen to modulate contractility.
  38. 38Rumen conditions and motilityIf ruminal contents become very acidic (as occurs in grain engorgement), motility will essentially cease. Also, the type of diet influences motility: animals on a high roughage diet have a higher frequency of contractions than those on a diet rich in concentrates.
  39. 39Rumination"cud chewing"
    -is regurgitation of ingesta from the reticulum, followed by remastication and reswallowing. It provides for effective mechanical breakdown of roughage and thereby increases substrate surface area to fermentative microbes.
  40. 40RegurgitationRegurgitation is initiated with a reticular contraction distinct from the primary contraction. This contraction, in conjunction with relaxation of the distal esophageal sphincter, allows a bolus of ingesta to enter the esophagus. The bolus is carried into the mouth by reverse peristalsis. The fluid in the bolus is squeezed out with the tongue and reswallowed, and the bolus itself is remasticated, then reswallowed.
  41. 41When does rumination occur?Rumination occurs predominantly when the animal is resting and not eating, but that is a considerable fraction of the animal's lifespan.
  42. 42Fermentationthis generates enormous, even frightening, quantities of gas. We're talking about 30-50 liters per hour in adult cattle and about 5 liters per hour in a sheep or goat.
  43. 43Eructationis how ruminants continually get rid of fermentation gases. As mentioned above, an eructation is associated with almost every secondary ruminal contraction. Eructated gas travels up the esophagus at 160 to 225 cm per second and, interestingly, a majority is actually first inspired into the lungs, then expired. (belching)
  44. 44Interfering with eructationAnything that interferes with eructation is lifethreatening to the ruminant because the expanding rumen rapidly interferes with breathing. Animals suffering ruminal tympany (bloat) die from asphyxiation.
  45. 45Rumen gasesparticularly methane, are increasingly in the news because of their contribution to greenhouse gas and climate change. As with most topics that attract the attention of activists and politicians, it is somewhat difficult to obtain accurate estimates of the contribution of ruminant digestive processes to global greenhouse gas. However, data from the Food and Agriculture Organization of the United Nations indicates that ruminants are responsible for roughly 20% of global methane emmisions, which equates to approximately 3-5% of total greenhouse gas production.
  46. 46Volatile Fatty Acids (VFA)produced in large amounts through ruminal fermentation and are of paramount importance in that they provide greater than 70% of the ruminant's energy supply. Virtually all of the acetic, proprionic and butyric acids formed in the rumen are absorbed across the ruminal epithelium, from which they are carried by ruminal veins to the portal vein and hence through the liver.
  47. 47Why do VFA need to be continuously removed from the rumenContinuous removal of VFA from the rumen is important not only for distribution, but to prevent excessive and damaging drops in pH of rumen fluid.
  48. 48squamous epitheliumlines the rumen and is similar to skin, has a structure similar to the columnar e. in the small gut performing efficient absorption of VFA, lactic acid, electrolytes, and water
  49. 49how is epithelial surface expandedby formation of vascularized papillae
  50. 50Importance of papillae size and lengthAnimals that have been on a high plane of nutrition, with abundant VFA production, have long, luxuriant papillae well suited to promote absorption. In contrast, animals which have been under nutritional deprivation have small, blunted papillae, and require time on a high quality diet to allow for development of their papillae and absorptive capacity.
  51. 51VFA diffusionVFA diffuse through the epithelium, down a concentration gradient
  52. 52VFA MetabolismAs they pass through the epithelium, the different VFA undergo different degrees of metabolism. Acetate and proprionate pass through the epithelium largely unchanged, but almost all of the butyric acid is metabolized in the epithelium to beta-hydroxybutyric acid, a type of ketone body.
  53. 533 Major VFA absorbed in the rumeneach have distinctive metabolic fates
    1) acetic acid
    2) proprionic acid
    3) butyric acid
  54. 54acetic acidutilized minimally in the liver, and is oxidized throughout most of the body to generate ATP. Another important use of acetate is as the major source of acetyl CoA for synthesis of lipids.
  55. 55proprionic acidalmost completely removed from portal blood by the liver. Within the liver, proprionate serves as a major substrate for gluconeogenesis, which is absolutely critical to the ruminant because almost no glucose reaches the small intestine for absorption.
  56. 56butyric acidmost of which comes out of the rumen as the ketone beta-hydroxybutyric acid, is oxidized in many tissues for energy production.
  57. 57example of VFA/lactose synthesisLet's put some of the academic information presented here into perspective. The little goat pictured here weighed about 200 lb when this picture was taken and produced 1570 kg of milk in a 305 day lactation. Her milk was roughly 4% lactose, 3.5% protein and 3.6% fat. This means that, for the sole task of producing milk, this goat has to synthesize about 250 grams of lactose and 180 grams of protein and 185 grams of fat every day.
    Essentially all the glucose in that lactose was synthesized in the liver and most of that synthesis was from proprionic acid generated by fermentation. Likewise, much of the fat as synthesized from ruminal acetate. When you consider that synthesis of lactose and milk fat are only two of many, many processes that are supported by volatile fatty acids, the process of fermentation in herbivores gains new meaning.
  58. 58Particle separator video- penn statehttp://bit.ly/2RWqs0H
    -can calculate meat particle size
    -has screens 19mm, 7mm, 4mm(effective fiber)
    -thickness of screens are proportional to diameter of holes
    -screen (1.18mm) (size of a piece of feed leaving rumen of a cow)
    -4mm looks at physical effective fiber (below this is very small)
    -calibrated with three dry feeds of material (silage)
    -shake 40 times (5 then turn) allows feed to move back and forth and pass through screens/holes
    -if you have silage with a lot of clumps make sure they are on top to be broken up.
    - take what's remaining on screens, weight it, record the weight, and insert on spreadsheet or add up amounts on tray and examine fraction on top, middle, and bottom try, to calculate percentages
  59. 59—

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FlashCards sobre Digestive Physiology Source Information, criado por J Wellington em 28-01-2020.
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J Wellington
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