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1. Rumination: Partially digested plant food (cud) is regurgitated up to the esophagus, where it is chewed and reswallowed. This process facilitates the mechanical breakdown of tough plant material through multiple chewing cycles, resulting in a greater surface area on which the rumen microbes and digestive enzymes can act.
2. Eructation: Built-up carbon dioxide or methane gas is expelled from the rumen. This is essential for dispelling excessive gas created by fermentation, thereby reducing the risk of too much gas being trapped in the rumen (a condition called bloat).


1. What is ileus? What causes it?

1. Ileus happens when there is a decrease in peristaltic waves resulting in ingesta moving too slowly through the intestinal tract.


How does ingesta flow from the small intestine to the anus in nonruminant herbivores like the horse? Include the different flexures in your description.

1. Duodenum
2. Jejunum
3. Ileum
4. Right ventral colon
5. Sternal flexure of the colon
6. Left ventral colon
7. Pelvic flexure
8. Left dorsal colon
9. Diaphragmatic flexure
10. Right dorsal colon
11. Transverse colon
12. Small colon
13. Rectum


Fat-soluble vitamins

Vitamin A - Promotes growth, the immune system, reproduction, and vision
Vitamin D - Essential for blood clotting and bone and tooth formation
Vitamin E - Important antioxidant
Vitamin K - Essential for the generation of clotting factors and many proteins made by the liver
Fat-soluble vitamins are stored for long periods of time in tissues. Excess is not excreted, making toxicity a possibility if high levels are consumed.


Upper incisors in a ruminant

Cattle, for example, do not have any upper incisors or upper canine teeth. Instead, ruminants have a dental pad, which is a flat, thick, connective tissue structure on the maxilla opposite the lower incisors and canine teeth.


Floating teeth

Horses often develop enamel points (sharp edges) on the buccal edge of the occlusal surface of their upper arcade of teeth and on the lingual edge of the corresponding teeth of the lower arcade. To reduce these points, as well as other occlusal-surface malformations, the surface of the teeth in horses may have to be filed with a rasp. This procedure is called floating teeth.



Yellow breakdown product of hemoglobin
Excess red blood cell breakdown results in an excess amount of unconjugated or free bilirubin in plasma. If the amount of the unconjugated bilirubin exceeds the ability of the liver to conjugate or join it, the excess unconjugated bilirubin will be deposited in tissues. This causes the tissues to turn yellow, a condition called jaundice or icterus.
Clinically, jaundice is most readily seen as a yellowish color of the mucous membranes and the whites (sclera) of the eyes.


Name some animals that are hindgut fermenters.



Hindgut vs. foregut fermentation

Obtaining and transporting nutrients is a vital function for all multicellular organisms and different species have evolved some interesting ways of gaining, storing and digesting their nutrients.
Amongst herbivores, for example, almost all have cellulose digesting bacteria within their gut that live symbiotically, assisting with the break down of vegetation. Some are classified as “hindgut fermenters”, which have microbes and fermentation in their hindgut, the cecum and proximal colon. These animals are less efficient at digesting their food and can sometimes be observed practicing coprophagy (eating feces).
Other herbivores are “foregut fermenters”, or ruminants, which have pouches with microbes in the stomach. These microbes consume glucose from cellulose but produce fatty acids that the animal can use for energy. Microbes can also be digested further along the digestive tract as they are also a source of protein. Foregut fermentation, or rumination, is a slower digestive process, but has the advantage of providing more nutrients and wasting less energy.


Digestive compartments of a ruminant

Reticulum - Most cranial part of the forestomach; has a honeycomb appearance inside
(Reticulorumen - pertaining to both the reticulum and rumen; often describes the contractions of the rumen and reticulum together)
Rumen - large, fermentative section of the forestomachs of ruminants; the rumen is responsible for production of volatile fatty acids, microbial protein, and other essential nutrients needed by the ruminant
Omasum - A chamber of the ruminant forestomach that absorbs nutrients and water
Abomasum - the true stomach of the ruminant; secretes acids, mixes and contracts ingesta, and moves liquid chyme into the small intestant


Ruminoreticular fold

Separates the reticulum from the rumen


Muscular sacs of rumen

The rumen is actually a series of muscular sacs partially separated from one another by long, muscular folds of rumen wall called pillars.
During ruminal contractions, these pillars can almost close off certain sacs of the rumen and in this way allow the effective mixing and stirring of ruminal contents.
Mixing of the reticulorumen contents is essential for the fermentative function of the rumen.


Which layer of small intestine has villi and a brush border?

The mucosa
It's adapted to provide a tremendously large surface area for absorbing nutrients thanks to villi.
Each villus contains thousands of very small villi of its own called microvilli.
They are so plentiful that they resemble short bristles on a brush, so they are often called the brush border.


Lubrication & digestion

Mucosa is the tissue lining of some organs and body cavities such as the nose, mouth, lungs, and digestive tract.
Glands in the mucosa produce a thick fluid called mucus. In the digestive system, this mucus acts as a lubricant allowing food to smoothly pass along the digestive tract. In the stomach and intestinal tract, mucus also prevents digestive enzymes from eating the internal lining of the organs.