Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Rebel Biology - Nutrition ✱ organisms need a variety of nutrients to perform life’s activities ✠ the most important ones are fats, carbs, proteins vitamins, water, ✠ these either provide direct value(fats/carbs/proteins) or they help facilitate the rxns ✠ necessary for the extraction of the others(H20 and vitamins) ✱ not all nutrients need to be digested in order to be effective ✠ some, like fiber, help stimulate the digestive process There are 4 basic steps to get the nutrients: ✱ in order for the nutrients to be effective in helping organisms they first have to be ingested ✠ this is basically bringing the food into the organism ✠ often involves the mechanical breakdown of food ✱ next the food must be chemically broken down into simpler forms by the process of digestion ✱ thirdly the simpler nutrients must be absorbed by the cells of the organism ✱ finally the waste products(stuff not needed) have to be eliminated Human Digestion ✱ the structure of the human digestive sys is very similar in the basics earthworm ✠ diff. organs for diff. stages of digestion ✱ the food enters the body through the mouth(oral cavity) where mechanical and some chemical digestion takes place ✱ then the following path is taken: pharynx esophagus lg. intestine stomach rectum sm.intestine anus ✱ throughout this process there are diff. digestive glands that secrete digestive juices into the alimentary canal ✠ these are the salivary glands, liver, and pancreas The Mouth ✱ the teeth and tongue are the important structures that help breakdown and form the food into a bolus(a food mass) ✱ the salivary glands also secrete salivary amylase to help breakdown the starch contained in the food ✱ when food is sufficiently chewed it passes through the pharynx and down the esophagus The Esophagus ✱ this is the tube leading from the pharynx to the stomach ✱ the food is passed down the tube by varying waves of muscular contractions that is called peristalsis ✠ muscles in front of the food relaxes and those behind will contract ✱ there is also a strong ring of muscles called a sphincter that will open to allow food to pass into the stomach The Stomach ✱ this is a thick walled, muscular sac ✠ can expand to hold up to 2 liters of materials ✱ there are various glands that release enzymes that act on the food to break it down chemically ✠ gastric juices come from gastric glands and help to lower the pH(1.5 - 2.5) of the stomach to help break down proteins in the food ✠ pyloric glands secrete mucous to help protect the lining of the stomach from the high pH ✱ only partial digestion of food takes places here and food usually passes through in 2 - 6 hours and liquids move through faster in around 20 mins or less ✱ when the stomach is empty the gastric juices are removed ✠ stimulation from 3 main factors will stimulate the release of the juices again: ➀ the though, sight or smell of food ➁ food touching the lining of the stomach ➂ when food stretches the lining of the stomach then the hormone gastrin will help to stimulate the gastric juices ✱ when the food is digested enough into a soupy mess called chyme then the pyloric sphincter will open and it will empty into the small intestine or duodenum Small Intestine ✱ a coiled tube about 2.5 cm in diameter and 6.5 m long ✱ there are 3 basic parts: duodenum(first section) jejunum (middle section) ileum (end section) ✱ most chemical digestion takes place here and this is also the site of absorption ✱ this is made more efficient by the presence of many tiny finger like projections on the folds called villi ✱ there are also even smaller villi called microvilli ✱ the sm int is in constant motion when food is present in it ✠ this mvmnt is much similar to the mvmnt of the esophagus ✠ this has 4 main effects: ➀ squeeze through the chyme ➁ mix chyme with with dig. juices ➂ break down food mechanically ➃ speed up absorption ✱ contrasting with the stomach most of the dig juices in the sm int are generally alkaline which means basic (pH above 7) ✱ the chyme mixes with pancreatic juice, intestinal juice and bile to aid the chem dig. Large Intestine ✱ this is 1.5 m long and about 6cm in diameter ✱ no digestion occurs here it has already been done ✱ right at the juncture of the sm an lg int there in the appendix (on right side of body) ✱ the main function of the lg int is the reabsorption of water from food ✠ about 3/4 of the water gets taken back in ✱ a second function of the lg int is the absorption of the vitamins that get produced by the bacteria that live in it ✱ the third function is elimination of the waste products which consist of cellulose, bile, mucous, and worn out cells from the dig sys ✠ this material (feces) is stored for a while in the rectum and periodically removed rough the anus