Hindgut+Fermenters+-+Horses

=Hindgut Fermenters - Horses=

Pre-Small Intestine (Group 2 - Angie E)

 * The mouth:** Digestion begins in the mouth which is also called the "oral cavity." It is made up of the teeth, the hard palate, the soft palate, the tongue and related muscles, the cheeks and the lips. Horses also have three pairs of salivary glands, the parotid (largest salivary gland and located near the poll), submaxillary (located in the jaw), and sublingual (located under the tongue). The front teeth of the horse, called incisors, clip forage, and food is then pushed back in the mouth by the tongue, and ground up for swallowing by the premolars and molars.
 * The esophagus:** The esophagus is about 4 to 5 feet (1.2 to 1.5 m) in length, and carries food to the stomach. A muscular ring, called the cardiac sphincter, connects the stomach to the esophagus. This sphincter is very well developed in horses. This and the oblique angle at which the esophagus connects to the stomach explains why horses cannot vomit. The esophagus is also the area of the digestive tract where horses may suffer from choke.
 * The stomach:** Horses have a relatively small stomach for their size, and this limits the amount of feed a horse can take in at one time. The average sized horse (800 to 1,200 pounds (360 to 540 kg)) has a stomach with a capacity of around 4 US gallons. The horse stomach consists of a non-glandular proximal region (saccus cecus), divided by a distinct border, the margo plicatus, from the glandular distal stomach. In the stomach, assorted acids and the enzyme pepsin (which comes from which zymogen?) break down food. Pepsin allows for the further breakdown of proteins into amino acid chains. Other enzymes include resin and lipase. Additionally, the stomach absorbs some water, as well as ions and lipid soluble compounds. The end product is food broken down into chyme. It then leaves the stomach through the pyloric valve, which controls the flow of food out of stomach.

Small Intestine (Group 2 - Abigail F)
The small intestine of a horse is about 70 feet long and holds around 48 quarts of feed stuffs. It is broken into three parts; the duodenum, jejunum and the ileum. Most abosorption of the nutrients occurs in the jejunum and the beginning of the ileum, but the duodenum also absorbs nutrients as well. Starting with the duodenum, this is the active site of digestion. Panctreatic secretions, from the pancreatic duct, release "juice" which contains several zymogens (inactive enzymes), pancreatic lipase, and pancreatic amylase. The two major zymogens are trypsinogen and chymotrysinogen. Trypsinogen is activated by enterokinase (lies in the intestinal mucosa) which then creates the enzyme trypsin. Now that trypsin is formed, it activates chymotrysinogen which then turns into the enzyme chymotrypsin. Trypsin and chymotrypsin both digest protiens into peptides, but are unable to break them down into single amino acids, but don't fret for there are other zymogens that digest protien as well including proelastase and procarboxypeptidase A and B (also activated by trypsin). Pancreatic lipase breaks down fats (mainly triglyceride) into fatty acids able to be absorbed. Along with lipase, bile (mixture of salts, pigment, mucous, and cholesterol) is secreted from the liver to help break down fats and and suspend them in water. Bile is usually stored by the gall bladder, but since horses don't have one, bile is always being secreted into the small intestine. Pancreatic amylase breaks down carbohydrates (glucose) from plants into maltose which is then able to be absorbed and used.

After the duodenum comes the jejunum which is responsible for most of the nutrient absorption. The jejunum has the most surface area because of villi (finger like projections) and micro villi on the villi them selves.

The ileum is really the last place for nutrient absorption before the mixture of broken down feed and pancreatic juices enter the large intestine.

(Cholesystokinin (CCK) is a hormone that is stimulated by fat and protien entering the duodenum which causes the pancreas to contract that leads to the feeling of being full)

Large Intestine (Group 2 - Brooke F)
Cecum- receives feedstuffs straight from the ileum. I is a blind pouch located at the junction of the small and large intestine (the cecum is part of the LI). Uses Microbial digestion of fibers mostly carbohydrates, which then produces volatile fatty acids. Within the cecum the synthesizing of Vitamins B and K occurs. The colon is split into two parts the large colon and the small colon.the colon secretes mucous which is important to ensure the fibrous material moves through the colon without causing any damage. When feed enters the colon microbial fermentation results in the production of the volatile fatty acids which are synthesized along with vitamin B, also water absorption occurs. Rectum- gets rid of dead bacteria and useless cells also forms the undigested material into feces

Post Large Intestine (Group 2 - Emily D)
Rectum- The leftover material that cannot be absorbed or dead cells are collected in the rectum and eliminated as feces.The rectum is approximately 1 foot long in a horse and the feces is collected here and then exits the body via the anus which is the opening. The rectum is part of the LI, so this part would just be the anus).