Nutrients, Enzymes and Digestion Lesson 4: Digestion and Absorption Digestive Tract and Accessory Organs http://highered.mheducation.com/sites/0072495855/student_view0/chapter26/animation organs_of_digestion.html 1
Pancreas: Two types of tissues 1.digestive tissues secrete digestive enzymes 2.Hormonal tissues release hormones into the blood Neutralizing Acids Acids entering the small intestine from the stomach convert the chemical prosecretin to secretin Secretin carried by blood to the pancreas, stimulates the pancreas to release bicarbonate ions into the small intestine to neutralize the HCl from the stomach The bicarbonate ions raise the ph in the small intestine from 2.5 to 9 Pancreatic Enzymes returns pepsin to its inactive form pepsinogen The pancreas also secretes enzymes for digesting 1. Fats (lipids) Lipases 2. Carbohydrates (starch) Pancreatic amylase 3. Proteins Trypsinogen (becomes trypsin in small intestine) 2
Small Intestine o In mammals, the length of the small intestine is related to diet. Meats are relatively easy to digest, while plant materials are more difficult to digest carnivores, such as wolves and lions, have short small intestines herbivores, such as rabbits, have long small intestines Omnivores, such as raccoons, pigs, bears, and humans, have small intestines that are of intermediate length, allowing them to digest both types of food o Length approx. 3 4 meters long o Diameter approx. 2.5 centimetres wide o Has 3 sections: 1. Duodenum 25 30 cm long; majority of digestion occurs here 2. Jejunum majority of absorption occurs here 3. Ileum more absorption o Enzyme Secretions Erepsins protein digesting enzymes (peptide chains amino acids) Enterokinase activates trypsinogen Maltase breaks down maltose (maltose glucose) Sucrase breaks down sucrose (sucrose glucose + fructose) Lactase breaks down lactose o Villi projections from the wall of the small intestine where absorption of nutrients take place. The villi greatly increase the surface area for absorption to occur There are millions of them all along the small intestine Each villus is supplied with a blood vessel (capillary) and a lymph vessel (lacteal) Capillary absorbs amino acids and sugars Lacteal absorbs fats Also have microvilli attached which provides more surface area absorbtion of nutrients into blood vessels occurs by diffusion and by active transport 3
Liver and Gall Bladder: Bile produced in the liver and stored in the gall bladder Produced from the breakdown of hemoglobin from dead red blood cells carried by the bile duct to the small intestine when fats are present In the small intestine, bile breaks apart fat globules into smaller pieces increases surface area for enzyme action Functions of the liver 1. The liver produces and stores glycogen and vitamins 2. Produces bile (stored in the gall bladder) 3. Detoxifies chemicals (i.e. alcohol and drugs) The liver is positioned next to your stomach on the right side of your body 4
Digestive Enzymes of the Pancreas and Small Intestine Digestion of Proteins in the Small Intestine Functions of the Liver. 5
Large Intestine: Includes the cecum, colon, rectum, and anal canal Length approx. 1.5 m long Diameter approx. 7 cm wide Absorbs water, vitamins, salts Stores non digestible material until defecation Cecum below the spot where the small intestine enters Ascending colon goes up the right side of the body Transverse colon goes across the body just below the stomach Descending colon goes down the left side of the body Sigmoid colon enters the rectum Rectum last 20cm of the large intestine; opens at the anus Anus THE END!!! Feces is brown due to the breakdown of pigments found in bile Feces is smelly due to gases produced by bacteria in our colon Polyps small growths on the lining of the colon can be benign or cancerous caused by diets high in fat and low in fibre Appendix a vestigial (useless) organ attached to the cecum if inflamed (appendicitis) it can rupture and cause infection in the body leading to illness and maybe death Defecation occurs when feces accumulates in the rectum causing it to stretch the stretching initiates a reflex action which contracts rectal muscles and defecation occurs Diarrhea Excess water in feces Causes: Infection intestinal wall becomes irritated and peristalsis increases, preventing wat absorption Nervous stimulation intestinal wall is stimulated, diarrhea results Constipation dry, hard feces Causes Dehydration lack of water causes dry, hard feces Lack of fibre no bulk to stimulate rectal contraction. 6