Anatomy - Small Intestine (small bowel) Stomach empties into the small intestine Extends from to Large Intestine The acidic digestive juices released from the stomach create a mixture that is released into the small intestine Unlike the large intestine, the small intestine normally remains bacteria-free Long, coiled looped tube with [thumb] diameter and up to 8 m long Fills lower of abdominal cavity & is attached by a thin membrane called mesentery [ serves several functions: attaches and supports SI preventing loops from tangling; carries blood and lymph vessels which supply O2 and remove nutrients]

Small Intestine The of digestion and absorption processes occur in this area of the digestive tract. There is a layer of the intestine that contains a rich supply of in order to provide the blood an opportunity to pick up the digested substances Resulting nutrient molecules absorbed into circulatory system & delivered to cells of the body

Villi in the Small Intestine - The inside wall of the SI has millions of projections called on which are located -

Small Intestine The small intestine releases about of fluid a day to produce digestive juices Many mucus producing glands called are located in the . These glands release secretions that the small intestine from the acidic the stomach releases. These glands do not function well during times of stress

Absorption of Nutrients C6H12O6 and aas ( )move through the cells of the intestinal wall to the blood stream by Fig. 6.22 Fig. 6.23

Absorption of Nutrients Glycerol and fatty acid molecules into the cells of the intestinal wall where they are resynthesized into fats, coated with proteins, and move into lymph vessels for eventual transport into the bloodstream. Fig. 6.24

Peristalsis Fig. 6.15

Small Intestine Duodenum: Jejunum Ileum is about long The small intestine is made up of three sections: Duodenum: is about long receives food from , from liver (stored in gall bladder), and from the pancreas some absorption occurs here Jejunum is about 2 m long - Ileum is about 3 m long - mainly absorbtion connects to the first part of the LI( )

Small Intestine Intestinal Enzymes: Intestinal lining has an important exocrine function The cells in this lining produce many important enzymes that do the majority of the chemical digestion The intestinal enzymes are needed to break nutrients into their smallest chemical components so they can be absorbed into the Large Molecules- such as most proteins, polysaccharides and disaccharides are too large to move into the blood stream They must first be broken down in the small intestine by the intestinal enzymes

Intestinal Hormones The lining of the duodenum produces an important digestive hormone called . Increased acidity in the small intestine or nervous activity causes the release of secretin by the lining of the small intestine The release of secretin into the blood stream causes the nearby pancreas to step up the production of juices to acidic materials that the stomach is beginning to release

Pancreas As food moves from the stomach to the small intestine, soaked in and pepsin. When acids enter the small intestine, a chemical called is converted into . Secretin is absorbed into the and carried to the , where it signals the release of a solution containing Bicarbonate ions are released by the pancreas and carried to the small intestine where they the HCl in gastric juices and raise the pH from about 2.5 to 9.0. The basic pH

HCl enters the from the stomach HCl stimulates the conversion of into secretin 3. Secretin is absorbed into the blood vessels 4. Secretin is carried by the into the pancreas 5. Here secretin acts as a , stimulating the release of pancreatic fluids. 6. The bicarbonate ions released by the pancreas, neutralize the HCl from the stomach. The neutralization of acid protects the lining of the duodenum

Pancreatic Secretions Pancreatic secretions also contain enzymes that promote the breakdown of the three major components of food Protein: Trypsinogen - Once trypsinogen reaches the small intestine, an enzyme called enterokinase converts the inactive trypsinogen into trypsin, which acts on partially digested proteins. - Trypsin breaks down long-chain polypeptides into shorter peptide chains.

Pancreatic Secretions Erepsin: Released from the pancreas and small intestine -Complete protein digestion by breaking the bonds between short chain peptides, releasing individual amino acids 2. Carbohydrates: Amylase - Continue digestion of carbohydrates which began in the mouth - Carbohydrates are further broken down by disaccharides from the small intestine

Pancreatic Secretions 3) Lipids: Lipases 2 Types: 1) Pancreatic Lipase: the most common breaks down fats into 2) Phospholipase: acts on

Liver and Gallbladder The liver continually produces a fluid called . Bile contains , which help with fat (lipid) digestion. When the stomach is empty, bile is stored and concentrated by the

Liver and Gallbladder Fats enter the duodenum (small intestine) and stimulates the release of the hormone 2. CKK is carried by the to the gallbladder. 3. CKK stimulates the gallbladder to release 4. Once inside the small intestine the bile salts (breakdown) large fat globules ( ) 5. Increase surface area  further breakdown fats

Liver and Gallbladder Bile also contains pigments. The liver breaks down from and stores the products in the gallbladder for removal (poo is brown because of hemoglobin breakdown) Liver stores and vitamins A, B12 , and D The liver is also important in many substances in the body. - Harmful chemicals are made and can be dissolved in the blood and . * One of the more

Liver and Gallbladder Problems Cholesterol, an component of bile. Acts as a for the salt crystals found in bile. - The and form larger crystals called . -Gallstones can the , impairing fat digestion and causing pain. - Any obstruction of the bile duct or accelerated destruction of RBC can cause  turns skim and other tissues yellow

Large Intestine (Colon) About 1.5 m long and has a diameter of 7 cm Receives of digestion (material unable to pass into bloodstream) H2O, Na+ and other minerals are absorbed at the LI as is formed If absorption process is interfered with diarrhea results [mortality from infant diarrhea, still the main cause if death in infants in many countries, principally caused by dehydration]

Large Intestine The large intestine is made up of three distinct sections: Transverse colon: Ascending colon Descending colon These colons are designed to go up, across and then down so that materials move slowly through this area of the GI tract, which allows for sufficient time to

Large Intestine There is an important one-way valve called the valve that or fecal contents from the colon into the small intestine There are one-way valve called that control the out of the body. The last of these two sphincters is called the and is controlled .

Large Intestine The colon contains a rich supply of for the of water into the blood stream. However, there is no villi or microvilli in the large intestine or enzymatic production; therefore no digestion occurs. The main function of the large intestine is to and to slow the progress of material through the digestive process. The colon also to help solids slide through the intestinal tubing

Large Intestine LI harbours bacteria break down minerals for which we lack enzymes to digest synthesize a.a. and vitamins some of which are absorbed into the bloodstream This organ does not experience continuous peristalsis like the SI  several times per day it experiences contractions which move its contents a short distance The area of the large intestine that until they are ready to be released is called the There are over 1000 species of bacteria

Four Functions of the Large Intestine 1. Absorbs water, minerals and salts 2. Decomposes left-over organic material with the help of resident bacteria 3. Produces vitamin B, vitamin K and folic acid (needed for blood cell production) 4. Stores and eliminates solid wastes and feces when appropriate

Anatomy - Anus Sphincter which ends the GI tract When the rectum is distended & full, nerve endings in the walls (stretch receptors) send a message to the indicating that it is time to void the feces The bulk of feces consists of (mostly dead cells) and along with other indigestible materials

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