The American Black Bear's Digestive System
The American black bear digestive system is very similar to that of a human because they are both mammals. The first step is that the black bear mechanical (chewing) and chemical (enzymes) digests the food in it's mouth by using the salivary glands which are triggered by food coming into contact with the bears oral cavities (mouth).The food then goes down the pharynx to esophagus where peristalsis push the food into the stomach. The stomach produces a gastric juice which kills all the bacteria. The gastric juice also contains pepsin in it. Pepsin is an enzyme chemically breaks down proteins. Then the liver makes bile and sends it to the gallbladder and the gallbladder sends it to the small intestine. In the small intestine the bile salts absorbs and digests fats and holds onto wastes from the liver. This takes place in the duodenum the first part of the small intestine. The duodenum is where the stomach juice comes next after being in stomach and is churned with juices from the liver, pancreas and gallbladder. The pancreas then sends enzymes to the small intestine such as amylases or maltase. Amylases are proteins that turn starch into sugar. Maltase finishes digestion by splitting the two molecules in glucose apart. Then the small intestine absorbs the nutrients from the food through small finger like projections called the villi that are on the lining of the small intestine.Other enzymes that occur in the small intestine are nucleases. Nucleases chemically break down the DNA and RNA in our food and put it the correct nucleic acids. After that the large intestine absorbs the excess water. Then the rectum pushes the feces (poop) out. In the winter bears hibernate and don't eat for 5-6 months. This means that they slow down there metabolism which means that they do not need food throughout their hibernation. When they do wake up they eat berries, fish, rabbits, plants, deer and other organisms.
Diffusion in the Digestive System
Diffusion occurs in the villi which as we know are on the walls of the small intestine. To be more specific on how these tiny projections absorbed nutrients we must understand what they are made of and how exactly they work. Millions of villi cover the small intestine. The center of a villi has one artery, a small piece of muscle and a capillary. The layer on the outside of the central area is a mucous membrane. This membrane is made up of two cells. 1. Long and thin cells. 2. Bottle looking cells. There are about 600 microvilli on the thin cells that help in absorption. Villi in the small intestine move back and forth and this is to raise blood flow and increase diffusion of nutrients.
Source:
http://www.britannica.com/EBchecked/topic/629261/villus
Source:
http://www.britannica.com/EBchecked/topic/629261/villus
American Black Bear Slideshow
http://denverdigestive.com/gastroenterologist.html
http://www.blackbearkingdom.net/black-bear-hibernation.html
http://www.srvhs.org/staff/teachers/CSoldati/mammalian%20digestive%20system.htm
http://www.blackbearkingdom.net/black-bear-hibernation.html
http://www.srvhs.org/staff/teachers/CSoldati/mammalian%20digestive%20system.htm