Home Accessible Science Activities. At the point where the ileum joins the large intestine there is a valve, called the ileocaecal valve, which prevents materials flowing back into the small intestine. They shot it with an airgun and found that the new device protected its contents electronic equipment at forces up to 60, g. Theoretical Ecology Series, vol. These muscles raise the back of the tongue and also close both sides of the fauces to enable food to be swallowed. The normal function of the crop is food storage.
Digestive System Outline:
The hydrolysis of the folates, a necessary step to absorption, takes place on the brush borders of jejunal enterocytes and is completed on lysosomes structures within the cell that contain various hydrolytic enzymes and are part of the intracellular digestive system. When hydrolysis of folates is disturbed, anemia develops. This process is interfered with by certain drugs, especially phenytoin, used in the management of epilepsy, and by the long-term use of sulfonamides in the suppression of disease.
A methyl group is added to pteroylglutamic acid in the enterohepatic circulation in the liver and is excreted in the bile. Approximately micrograms are utilized each day. The method of absorption is uncertain. Vitamin B 12 , also called cobalamin because it contains cobalt, is essential to the formation of blood cells. It is a coenzyme that assists the enzymes responsible for moving folate into the cell interior.
Vitamin B 12 is a product of bacterial metabolism. Although bacteria in the colon also produce vitamin B 12 , it cannot be absorbed at that site. Vitamin B 12 occurs in a bound form in food and is liberated by proteolytic activity in the stomach and small intestine. It then binds with intrinsic factor IF , a glycoprotein produced by the same parietal cells that form hydrochloric acid. Intrinsic factor is essential to transport, and the B 12 protein complex, known as transcobalamin II, is necessary to transfer the vitamin from the intestine to the rest of the body.
Once the IF is attached, further proteolytic digestion of the bound vitamin is prevented. Absorption is confined to the distal cm of ileum, especially the last 20 cm, where the complex binds to receptors in the brush border of the enterocytes. The process is slow; it takes three hours from its presentation in food to its appearance in the peripheral blood via the enterohepatic circulation and hepatic veins. The daily requirement of vitamin B 12 is one microgram. Vitamin B 12 is stored primarily in the liver.
Iron is necessary for the synthesis of hemoglobin, the oxygen-carrying compound of the red blood cells.
It also has an important role as a cofactor in intracellular metabolism. The main dietary sources are meat, eggs, nuts, and seeds. The average daily diet contains approximately 20 mg of iron; humans are unable to excrete iron that has been absorbed in excess of the daily requirement of 1 mg.
The acid in the stomach prevents the formation of insoluble complexes, as does vitamin C. Some amino acids from dietary protein stabilize the iron in low molecular weight complexes. Phosphates and phytates of vegetable origin, some food additives, and the inhibition of acid secretion impede the absorption of iron. Iron is almost wholly absorbed in the duodenum by a process that involves metabolic activity requiring energy.
Most of the iron remains trapped in the surface enterocytes and is lost when the cells die and are shed into the intestine. Alcohol in the stomach and duodenum increases the rate of absorption. Transport of the iron from the enterocyte is achieved by binding to a carrier, a plasma protein called transferrin. From the intestine it passes into the portal circulation and the liver. When the loss of iron is increased, as in excessive menstruation and in bleeding disorders, the rate of absorption is stepped up from less than 1 mg per day to 1.
Vitamin D is essentially a hormone and is available from two sources. First, under the influence of photosynthesis made possible by ultraviolet rays from the Sun, a sterol compound from the liver dehydrocholesterol is converted to vitamin D 3.
This supplies enough vitamin D 3 for human needs. In the absence of exposure to sunlight, dietary supplements become necessary. Eggs, liver, fortified bread, and milk are the main sources of vitamin D.
Deficiency of vitamin D occurs when there is lack of sunlight and inadequate vitamin D in the diet. It may also result from disease or after resection of the small intestine, which may cause malabsorption. In these circumstances softening of bone osteomalacia and rickets may occur. In the jejunum vitamin D is incorporated along with bile salts and fatty acids into the micelles, and, subsequently, as the provitamin D 1 , vitamin D is absorbed in the ileum and then passes into the circulation via the portal vein.
A specific bloodborne protein, an alpha-1—globulin, carries it to the liver, where the process of chemical change to the active hormone begins by hydroxylation to cholecalciferol. The derivatives are conveyed from the liver to various tissues, including the skin, bone, and parathyroid glands.
In the intestine vitamin D influences the permeability of the brush borders of the enterocytes to calcium. Vitamin D levels can influence hemoglobin production in the body. For example, persons with low levels of vitamin D may develop anemia, and hemoglobin levels in these individuals can be increased by vitamin D supplements. Although the mechanism by which vitamin D influences hemoglobin production is unclear, research has suggested that it may protect the oxygen-carrying molecule via a protective anti-inflammatory action.
Vitamin D has also been shown to augment the production of red blood cells in the presence of erythropoietin, a hormone produced primarily in the kidneys that influences the rate of red cell production. We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind. Your contribution may be further edited by our staff, and its publication is subject to our final approval.
Unfortunately, our editorial approach may not be able to accommodate all contributions. Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Calcium Calcium is required for the construction of bone; it forms part of the substance cementing together the walls of adjacent cells; and it is vital in the responsiveness to stimuli of muscle and nerve cells, which determines their excitability.
Magnesium An average diet contains around mg of magnesium, of which two-thirds is absorbed. Hematinics Hematinics are substances that are essential to the proper formation of the components of blood. Folic acid Folic acid pteroylglutamic acid is necessary for the synthesis of nucleic acids and for cell replication. Vitamin B 12 Vitamin B 12 , also called cobalamin because it contains cobalt, is essential to the formation of blood cells.
Iron Iron is necessary for the synthesis of hemoglobin, the oxygen-carrying compound of the red blood cells. Vitamin D Vitamin D is essentially a hormone and is available from two sources. Page 20 of Next page Intestinal gas. This is where the majority of digestion takes place.
The small intestine contracts to move food through it with the help of bile secretions and pancreatic and intestinal juices, allowing it to absorb nutrients with villi.
To make a more advanced model, you can distinguish the different parts of the small intestine. The duodenum is a small tube connecting the stomach to the jejunum. The jejunum is where the majority of digestion takes place and is the middle part of the small intestine.
The ileum is the last region of the small intestine that connects to the large intestine. It should be located at the end of the small intestine. Simply draw a small pouch at the end of the small intestine towards the left side of your paper. The appendix is a small pouch-like structure that is thought to have lost its purpose and become more of a liability than an aid in digestion.
But it is part of the digestive system and sits where the small and large intestines connect. Sketch the large intestine. Extending from the end of the small intestine, right above the appendix, draw the large intestine. It should look like two squiggly tubes side by side and should go straight up on the left side of the small intestine, then go across the body below the stomach, and then go straight down towards the bottom of the body on the right.
It should form the top three sides of a squiggly, tubelike- square. The passage of food is slower through the large intestine in order to allow for fermentation by bacteria and other microorganisms, called gut flora. The large intestine processes whatever cannot be used in digestion. It absorbs whatever it can, especially water, but then the rest will expelled as waste after about 12 hours.
To make a more advanced model, distinguish between the different parts of the large intestine. The cecum is attached to the appendix and connects it to the ascending colon. The ascending colon goes straight upwards and connects to the transverse colon, which goes across the body.
The transverse colon connects to the descending colon, which carries food down into the sigmoid colon, which goes directly to the rectum. Draw the rectum and anus. At the end of the large intestine is the rectum. The rectum connects the large intestine to the anus. To draw these, simply draw a wide tube that is the rectum leading to a narrower tube that is the anus. This should go to the bottom of your sheet of paper. Congratulations, you have drawn a digestive model!
The rectum stores feces until expulsion. The anus then expels waste. Now that your model is finished, take a black pen or marker and draw over it to create the final version. This is a nice finishing touch that will make it look more professional and will help it to really stand out. Simply trace over all of the pencil marks that you wish to keep. Color each organ a different color. This helps your model to stand out and also helps to distinguish between the organs.
For some of the organs, simply by looking at the drawing, it can be hard to tell where one ends and another begins, but if you color code them, it will be clear. For overlapping organs, try using using lighter and darker shades of the same color. The areas where they overlap will be darker, and the areas where it is a single organ will be lighter. Draw a thin line to each organ and write its name at the end of the line, outside of your model.
This is great for reference so that you can study your model and learn which organ is which. If you prefer not to write the names of the organs on your model, you could instead make a key at the bottom or on another piece of paper where you draw a little square of each color and write the name of the organ next to it.
If you wish to make your model more advanced, you can differentiate the parts of the small intestine. Simply draw a small line towards the beginning of the small intestine to show where the duodenum turns into the jejunum and then draw a small line towards the end of the small intestine to show where the jejunum becomes the ileum.
If you wish to make your model more advanced, you can also differentiate the parts of the large intestine.
Simply draw a small line to divide each part. The ascending colon is the part that goes straight upwards. It connects to the transverse colon which goes across the body and is the largest part of the large intestine. The transverse colon connects to the descending colon, which carries food downward. Finally, there is the sigmoid colon which goes directly to the rectum.
To learn even better, you can write a short description of each organ either with the labels or with your key. This will reinforce their functions and help your model to be very educational. The main function of the epiglottis is to seal off the windpipe during eating, so that food is not accidentally inhaled.
Not Helpful 0 Helpful 5. Food that contains fat enters the digestive system and stimulates hormone production, which in turn causes the contraction of the gallbladder, allowing the release of bile into the small intestine for the absorption of fat to occur. Not Helpful 3 Helpful 5. The anus is the end of the digestive system and expels waste. It detects the contents of the rectum and then releases waste out of the body.
Not Helpful 10 Helpful The function of the appendix is unknown. Other experts believe the appendix is just a useless remnant from our evolutionary past. Not Helpful 2 Helpful 5.
The pancreas is an accessory digestive organ. It functions to control blood glucose levels releasing insulin to reduce blood glucose levels, and glucagon to increase blood glucose levels , but it also releases many digestive enzymes into the small intestine that help chemically digest food proteins, carbs, etc. Not Helpful 1 Helpful 0. What would be a good description for a resistor? Answer this question Flag as