Digestion in Intestine Digestion in Intestine

Small Intestine Small intestines are roughly 6 metres long. Small intestines are roughly 6 metres long. Enzymes and bile are added. Enzymes and bile are added. Villi increase the surface area to help absorbtion. Villi increase the surface area to help absorbtion. Nutrients from the food pass into the bloodstream through the small intestine walls. Nutrients from the food pass into the bloodstream through the small intestine walls.

Small intestine Chyme passes out of the stomach through the pyloric sphincter into the small intestine. The small intestine is a tube about 6 metres long. The small intestine is divided into three sections, the duodenum, jejunum and the ileum. The first section of the small intestine is the duodenum.

Duodenum The duodenum receives about 12 grams of chyme each time the pyloric sphincter opens. The duodenum receives about 12 grams of chyme each time the pyloric sphincter opens. The duodenum is about 25 centimetres long and in the shape of a horse shoe. In the duodenum, chyme is diluted with bile salts (from the gall bladder) and pancreatic juices (from the pancreas).

Liver Directly affects digestion by producing bile Directly affects digestion by producing bile –Bile is an enzyme that helps dissolve fat Processes nutrients in the blood, filters out toxins and waste. Processes nutrients in the blood, filters out toxins and waste. Is often called the body’s energy factory Is often called the body’s energy factory

Gall Bladder Stores bile from the liver Stores bile from the liver Delivers bile when food is digested Delivers bile when food is digested Fatty diets can cause gallstones Fatty diets can cause gallstones

Bile Bile is produced in the liver and stored in the gall bladder. This contains bile salts which emulsify fat. Fat is normally insoluble in water. The bile salts are released into the duodenum making it easier to break down fat. The bile allows the fats to mix in with the watery digestive juices, and allows the enzyme lipase to digest the fats efficiently. Fat can take from 3 to 5 hours to be broken down and absorbed.

Pancreas Produces compounds to digest fats and proteins Produces compounds to digest fats and proteins Neutralizes acids that enter small intestine Neutralizes acids that enter small intestine Regulates blood sugar by producing insulin Regulates blood sugar by producing insulin

Pancreatic juices The pancreas provides alkaline pancreatic juices. These juices contain sodium bicarbonate to neutralise the hydrochloric acid mixed into the chyme from the stomach. Pancreatic juices also contain digestive enzymes such as: ●Trypsin and chymotrypsin – break down protein to peptides and amino acids.; ●Pancreatic amylase – breaks down starch and glycogen to maltose; ●Lipase – breaks down fat to fatty acids and glycerol.

Large Intestine About 1.5 metres long About 1.5 metres long Accepts what small intestines don’t absorb. Accepts what small intestines don’t absorb. Absorbs water and minerals from the waste matter. Absorbs water and minerals from the waste matter. Absorption means taking into the body via the blood stream. Absorption means taking into the body via the blood stream.

Table Showing Proteolytic Enzymes Sourc e Enzyme Acti vate d by SubstrateFunctions and/or Products Stom ach Pepsins (pepsinogens ) HCl Proteins and Polypeptides Cleaves interior peptide bonds of aromatic amino acids Pancr eas Trypsin (trypsinogen) Enter opepti dase Proteins and Polypeptides Cleaves peptide bonds on carboxyl side of basic amino acids (argenine or Lysine) Chymotrypsin (chymotrypsinogen) Tryps in Proteins and Polypeptides Cleaves peptide bonds on carboxyl side of aromatic amino acids Elastase (proelastase) Tryps in Elastin and other Proteins Cleaves peptide bonds on carboxyl side of aliphatic amino acids Carboxypeptidase A (procarboxypeptida se A) Tryps in Proteins and Polypeptides Cleaves peptide bonds on carboxyl terminal amino acids with aliphatic or aromatic side chains Carboxypeptidase B (procarboxypeptida se B) Tryps in Proteins and Polypeptides Cleaves peptide bonds on carboxyl terminal amino acids with basic side chains

Small Intestine mucosa Enteropeptidase...TrypsinogenTrypsin Aminopeptidases... Polypeptides Cleaves amino terminal amino acid from peptide Carboxypeptidases... Polypeptides Cleaves carboxyl terminal amino acid from peptide Endopeptidases... Polypeptides Cleaves mid portions of peptide Dipeptidases... Dipeptides----> two amino acids

Rectum and Anus Rectum Rectum –About 15cm long –Stores waste before egestion. Anus Anus –Muscular ring that controls egestion.

Write the name of each colored organ: Green: Green: Red: Red: Pink: Pink: Brown: Brown: Purple: Purple: Green: Green: Yellow: Yellow:

Peristalsis Peristalsis is the action of waves of muscular contractions which moves food along the digestive system. Dietary fibre aids peristalsis because it increases the bulk of the bolus or chyme being moved along.

Wall of the small intestine The inner surface of the small intestine is folded into finger- like structures called villi, which greatly increase the surface area available for absorption. The villi have a surface area of about 30m 2, this is equivalent to the size of a tennis court!

Digestion in the wall of the small intestine Protease breaks down peptides to amino acids. Protease breaks down peptides to amino acids. Maltase breaks down maltose to glucose. Maltase breaks down maltose to glucose. Sucrase breaks down sucrose to glucose and fructose. Sucrase breaks down sucrose to glucose and fructose. Lactase breaks down lactose to glucose and galactose. Lactase breaks down lactose to glucose and galactose. Lipase breaks down fats to fatty acids and glycerol. Lipase breaks down fats to fatty acids and glycerol.

Substances absorbed in the small intestine Water; Water; Alcohol; Alcohol; Sugars; Sugars; Minerals; Minerals; Water soluble vitamins; Water soluble vitamins; Peptides and amino acids; Peptides and amino acids; Fatty acids, glycerol and fat soluble vitamins. Fatty acids, glycerol and fat soluble vitamins.

Absorption The villi in the small intestine have a high blood supply. There are two types of absorption which occur here. Passive – through the process of osmosis the nutrients pass through the wall of the small intestine and into the blood supply. Active – a carrier transports the nutrient through the wall of the small intestine into the blood supply. This type of absorption requires energy. Once in the blood the nutrients are transported to the liver via the hepatic portal vein. The liver filters, converts the nutrients into substances that can be used by the body’s cells for energy and growth.

Absorption Most fatty acids and glycerol pass into the lymphatic system, and then the bloodstream. Once in the blood, nutrients are carried to all the cells of the body. Some are oxidised to produce energy and other are used to repair the cell or to build new cells. Once the nutrients have been absorbed, the remaining chyme passes into the large intestine or the colon.

Colon The colon is a tube just over one meter long, which is inhabited by bacteria. The main function of the colon is to absorb water into the bloodstream. Bacteria in the colon ferment dietary fibre (NSP) and produce fatty acids and gas. Other bacteria produce vitamin K, which is also absorbed. The products of bacterial digestion, along with water and any remaining minerals are absorbed leaving a residue behind.

Colon The watery residue moves along the colon, and the faeces are formed and stored in the rectum before being excreted through the anus. Young children gradually learn to control this action. It may take hours for the faeces to pass through the colon. This time can be reduced if the diet is high in fibre.

Gut Bacteria Stomach 10 1 – 10 3 cfu/ml Colon – cfu/ml Duodenum & jejunum 10 2 – 10 5 cfu/ml The gut contains bacteria 400 – 500 different species includes potentially pathogenic (e.g. Clostridia) & potentially beneficial (e.g. Bifidobacteria & Lactobacilli) bacteria. These are measured in colony forming units per millilitres (cfu/ml).

Summary of the phases of digestion Ingestion - this is the physical intake of foodstuffs into the gastrointestinal tract. Digestion - a series of physical and chemical processes which begin in the mouth, but take place mainly in the stomach and small intestine. Absorption - the passage of the digested food substances across the gastro-intestinal lining, or mucosa, into the blood and lymph. Elimination - the excretion, or elimination, of those food substances that cannot be digested (such as cellulose) or without any nutritional value in the faeces.

ENERGY Turning food into energy C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Respiration is the conversion of glucose into energy Glucose is “burnt” with oxygen It takes place in the Mitochondria GlucoseOxygen ENERGY Carbon Dioxide Water

Circulatory System What is it for ? We need 2 pumps because 1 would not have enough energy to push blood through the lungs and then around the body.

Describe the digestion of … Fish and chips Hamburger

Review of the learning objectives To recognise the organs involved in digestion; To recognise the organs involved in digestion; To understand the major functions of each body part in the digestive process; To understand the major functions of each body part in the digestive process; To understand the four major phases of digestion; To understand the four major phases of digestion; To understand the functions of different enzymes. To understand the functions of different enzymes.