Ruminants+-+Cows

=**Ruminants - Cows GREAT JOB, PERFECT AS IS :) **=

Pre-Small Intestine (Group 4 - Emily Nelsen)
Mouth – Cows have no upper incisors or canines, instead they have a dental pad. Only molars exist on the top of their mouth. They do have teeth in the front on the bottom, but those are for cutting and pulling. They bring feed into their mouth with their lips and tongue and chew it until it is fully mixed with the saliva (water, mucin, sodium bicarbonate, and salivary amylase) in which it forms a bolus.

Esophagus – The esophagus has circular and longitudinal smooth muscles which contract and push the feed through peristalsis. In ruminants, they have two way peristalsis in their esophagus so they can regurgitate their cud for further ruminating.

Stomach – Cows have a four compartment stomach consisting of the reticulum, rumen, omasum, and abomasum. The reticulo-rumen is basically the reticulum and the rumen. The reticulum has a honey comb-like structure and the rumen has finger-like papillae. The organs have the same function and are filled with microbes (bacteria, protozoa, and fungi). Both ferment fibrous carbohydrates and produce Volatile Fatty Acids, B and K-vitamins. It is the site of storing, moistening and the physical breakdown of food. The omasum is a sheet of very thin papillae that absorbs water and controls the passage rate of particles by their size. The abomasum is the “true” stomach. It is glandular and produces HCl (from chief cells) and enzymes for digestion. In this “stomach,” peptic cells secrete the zymogen pepsinogen. When this makes contact with HCl and protein, it forms the active enzyme, pepsin, to digest protein.

The reticular/esophageal groove is found mostly in young, milk-fed ruminants. It allows milk to bypass the rumen and enter directly into the omasum. We know it is stimulated to close with suckling and milk protein, but it could close with other substances we do not know of yet.

Small Intestine (Group 4 -Kayla Rinkel)
//__Small Intestine:__// There are 3 parts to the small intestine: the duodenum, the jejunum, and the ileum.

//Duodenum:// This section of the small intestine is the active site of digestion. Enzymes are used to break down food particles chemically. Zymogens, inactive enzymes, are secreted through the pancreatic juice, but must be activated to digest anything. The zymogen Tripsinogen must be activated by the enzyme enterokinase to transform it into the enzyme trypsin. Trypsin is then the enzyme to activate all of the other zymogens: Chymotrypsinogen (goes to the enzyme Chymotrypsin), Proelastase (goes to the enzyme Elastase), Procarbopeptidase (goes to the enzyme Carboxypeptidase A), and Procarbopeptidase B (goes to the enzyme Carboxypeptidase B). All of these five enzymes digest protein. Aside from zymogens the pancreatic juice also contains pancreatic lipase and pancreatic amylase. The amylase breaks starch down into sugars. From there maltase enzyme digests maltose, sucrase enzyme digests sucrose, and the lactase enzyme digests lactose. CCK is a hormone that is activated by fat and protein entering the duodenum which causes the pancreas and gull bladder to contract to secrete all of the digestive aids. The gull bladder stores and secretes bile. Bile salts break down lipids and phospholipids to create micelles (These transport lipids through the aqueous portion of the small intestine.).

//Jejunum:// This section of the small intestine has the function of nutrient absorption. There are three mechanisms for absorption: simple or passive diffusion which requires no energy, facilitated diffusion which requires the help of a carrier, and active transport which requires the use of energy.

//Ileum:// This is the last section of the small intestine and is used for residual nutrient absorption.