Name Date Class

Digestion,Absorption and Use of Food Nutrients are used by the cells as an energy source. This energy is used for metabolic activities, growth and repair of tissues. Nutrients are usually too large to pass through the cell membranes. Thus, organisms must break down their foodstuffs into their components for passing through the cell membrane. All animals and human are the heterotrophic organisms that obtain their food from autotrophs. Plants are the autotrophic organisms that produce their own food.

The alimentary canal İt is a long tube which start from mouth and with anus. Food is digested in the alimentary canal, the soluble products are absorbed and the indigestible residues expelled.

The structure of alimentary canal 1- Mucosa layer: The inside of the alimentary canal is lined by layers of Epithelium cells The functions of Epithelium cells a) they produce new cells b) Some of them can produce MUCUS. MUCUS: It is a slimy liquid that lubricates the lining of the canal and protects it from wear and tear, mucus may also protect the lining from attack by the digestive enzymes. c) Some epithelium cells produce digestive enzymes Such as; in the stomach and small intestinal lining.

2- Submucosa layer : This layer is rich in blood capillaries

3- Muscularis: In this layer there are two main kinds of muscles which are; a)Circular muscle: the fibres of circular muscle run round the canal b) Longitudinal muscle: The fibres of longitudinal muscle run along the alimentary canal.

Foodstuffs can be divided into six groups: Carbohydrates Minerals Lipids Vitamins Proteins Water

Carbohydrates, lipids and proteins are large food molecules, so that they need digestion Vitamins, water, and minerals may enter the blood vessels without digestion

STEPS IN DIGESTION 1-Mechanical digestion (INGESTION): It is the breaking down the big food molecules into their smaller pieces by the aid of teeth, tongue, and saliva. 2-Chemical Digestion. It is the breaking down the food molecules into their smallest unit by the aid of enzymes and water. 4-Absorption: Smallest units of foods can pass through the epithelium of alimentary canaland enter the blood vessels. Blood transports the absorbed nutrients to cells. HUMAN DIGESTIVE SYSTEM

Human digestive system has two parts 1) Alimentary canal 2) The accessory organs

The major organs of your alimentary canal (digestive tract) 1- Mouth 2- Esophagus (glottis) 3- Stomach 4- Small intestine 5- Large intestine (colon and rectum) Food passes throuhg alll of these organs.

The accessory organs are The tongue, teeth, salivary glands, liver, gallbladder, and pancreas. Although food doesn`t pass through them, they are important in mechanical and chemical digestion.

Digestive Enzymes - Some of the digestive enzymes are produced by epithelial cells in the lining of the alimentary canal such as stomach and small intestinal lining - Others are produced by glands such as salivary glands pancreas produce enzymes and pour them through tubes into the alimentary canal.

1) Alimentary canal

a) The Mouth

Mechanical and chemical digestion begin in your mouth. Food is ingested using the teeth, lips and tongue. The teeth then bite or grind the food into smalle pieces. The tongue mixes the food with saliva and form of it into a bolus The bolus is then swallowed.

SWALLOWING 1) Tongue move upward and forcing the bolus to the back of the mouth. 2) The soft palate closes the nasal cavity at the back. 3) Epiglottis automatically covers the opening to the windpipe to prevent food (bolus) from entering it, otherwise you would choke. b) Esophagus It is a muscular tube about 25cm long. No digestion takes place in the esophagus.

The wall of the tube contains circular and longitudinal muscles which conract and relax to make food move down. These waves of muscle contraction, called Peristalsis, move food through the entire digestive tract.

c) STOMACH The structure of Stomach  The entrance of stomach is normally closed by a ring of muscle at the lower end of the esophagu and Stomach also is connected with the small intestine by a lower opening called pyloric sphincter.

 The stomach has strong, elastic, muscular walls. Circular muscles provide horizontal movement of stomach. Longitudinal muscles provide upward and downward movements of stomach.

 Inner layer of stomach has a wrinkled appearance. The millions of gastric glands are located in the mucosal layer. Gastric glands Produce gastric juice containing HCL acid, pepsinogen, and Mucus. Mucus protects the stomach from strong digestive solution. Pepsinogen inactive form of Pepsin, and Pepsinogen is converted to pepsin by HCI acid.

Functions of stomach: It stores ingested food. It produces gastric juice to continue the digestion of food. It mixes the digestive juices and food by physical movements

SMALL INTESTINE: Small intestine is located between stomach and large intestine. Digestion of food is completed in the small intestine and nutrients are absorbed through its wall.

The structure of Small intestine  Different part of small intestine has different name; the first part, nearest the stomach is the duodenum, the part nearest to the colon is the ileum. 1- Duodenum: Most of the chemical digestion takes place in the duodenum. Liver and pancreas give their secretion to duodenum by duct. 2-ileum

 The lining of the small intestine appears velvety because of the millions of tiny finger-like projections called villi. These structures increase the surface area of small intestine (about 600 times)

 If the lining of intestine was smooth like the inside of water pipe, food would move rapidly through the intestine and many valuable nutrients would not be absorbed.

Villi; They are tiny finger like projections which are located internal surface of the small intestine. They resist the food movement to complete its digestion and contain blood capillaries transporting digested sugars and proteins. Also they contain lymphatic vessels transport the digested fats.

DIGESTIVE SECRETIONS: Digestive secretions originate from; Salivary glands. Gastric glands. Pancreas. Liver-Gall bladder. Small intestine.

The Secretion of MOUTH: There are three pairs of salivary glands in the lining of the mouth. Salivary glands secrete saliva into the mouth. Saliva contains salivary amylase (sometimes called ptyalin enzyme) which converts the carbohydrates (e.g.starch) into disaccharides (e.g.maltose) .

The Secretion of STOMACH: The millions of gastric glands are located in the inner layer of stomach. Gastric glands produce Gastric juice. Gastric juice contains hydrochloric acid and pepsin enzyme and Mucus

Functions of HCL; HCL destroys the most micro organisms which are entering the stomach and it provides the best degree of acidity for pepsin to work in. Function of pepsin enzyme; Pepsin is a protease (or proteinase), it acts on proteins and breaks them down into soluble compounds called peptides Pepsinogen is the inactive form of Pepsin; it will be active in the presence of HCL.

Function of Mucus: The lining of the stomach is protected from the action of pepsin and HCI acid by the layer of Mucus.

The Secretion of Small Intestine: The digestion of all foodstuffs is completed at the small intestine. Small intestine secretes following enzymes; Enterokinase: Converts the trypsinogen to Trypsin. Proteinase: breaks down the polypeptides to aminoacids. Sucrase; acts on sucrose. Maltase; acts on maltose Lactase; acts on lactose.

The Secretion of Liver : Liver cells secrete bile. Bile is a green, watery fluid made in the liver, stored in the gall bladder Gall bladder is a sac connected with liver by the liver-bile duct and it is located behind the right lobe of the liver. Its function is Bile also contains bile salts which act on fats rather like a detergent.They help the digestion of fatty materials by breaking them into small pieces.

Pancreatic secretions: Pancreas is a digestive gland lying below the stomach and is connected with duedonum by pancreatic duct.

Pancreas secretes following enzymes; Lipase; acts on fats Pancreatic Amylase; acts on carbohydrates There are several proteases which break down proteins to peptides and amino acids for example; trypsin one of the proteases from the pancreas, is secreted as the inactive trypsinogen and is activated by Enterokinase, Trypsin acts on proteins

DIGESTION OF CARBOHYDRATES

Digestion of Carbohydrates in MOUTH Chemical digestion of carbohydrate starts in mouth. Salivary glands secrete saliva into the mouth. Saliva is a juice which contains digestive enzyme called salivary amylase. Amylase acts on cooked starch and begins to break it down into maltose.

Starch + Water Amylase Maltose

Digestion of Carbohydrates in STOMACH Stomach is an acidic area. Amylase can not work in acidic region. Therefore, chemical digestion of carbohydrates stop in stomach.

Digestion of Carbohydrates in SMALL INTESTINE When food passes into the small intestine from stomach, it stimulates the cells of duodenum. Then, Secretin hormone is released into the blood from cells in the duodenum. When secretin reaches the pancreas it stimulates the pancreas to produce pancreatic juice. Pancreatic juice contains several enzymes and hydrogencarbonate which partly neutralizes the acid liquid from the the stomach. This is necessary because the enzymes of the pancreas and small intestine do not work well in acid conditions.

Enzymes act on every types of carbohydrates.

Starch + H2O Pancreatic amylase Maltose (disaccharide)

Maltose + H2O maltase Glucose + Glucose

Sucrose + H2O sucrase Glucose + Fructose

Lactose + H2O lactase Glucose+ Galactose

Digestion of carbohydrates is completed in small intestine.

Digestion of PROTEINS

In Stomach Protein molecules must be broken down to individual amino acids in order to be absorbed. The digestion of proteins begins in the stomach, with the secretion of gastric juice. When the food reaches the stomach it stimulates the stomach lining to produce a hormone called gastrin. This hormone circulates in the blood and, when it returns to the stomach in the bloodstream, it stimulates the gastric glandsto secrete gastric juice Gastric juice containing the pepsin enzyme; Pepsin is a protease (or proteinase), it acts on proteins and breaks them down into soluble compounds called peptides

PROTEINS Pepsin peptons (peptides)

in Small Intestine Tripsinogen and other proteinases take role in the digestion of proteins that are secreted by pancreas. Enterocinase secreted by intestinal glands to activate Trypsinogen to trypsin. Tripsinogen + Enterokinase ------Tripsin Peptones+H2O Tripsin Peptides + Amino acids Peptides+ H2O Proteinases aa + aa + aa + aa +… (aa = amino acid)

Digestion of LIPIDS Digestion of lipid occurs only in small intestine. The cells of the liver produce bile. Then, it is stored in gall bladder. When food enters to small intestine, Bile does not contain enzyme but it aids mechanical digestion of lipid. This process is called emulsification. Lipid bile Small lipid particles Lipase is secreted from pancreas. Lipase breaks down lipid molecules into fatty acids and glycerol. Lipid + H2O Lipase 3 Fatty acid + Glycerol

ABSORPTION There are many finger like projections in the lining of small intestine.They are called VILLI. Villi increa the absorption surface of small intestine. Passing of digested materials from small intestine to blood is called absorption. Vitamins and inorganic materials pass into the blood without digestion.

Glucose, amino acids and vitamins are absorbed by blood capillaries via epithelial cells. They are then carried away in capillaries, which join up to form veins. These veins unite to formone large vein , the hepatic portal vein This vein carries all the blood from intestine to the liver, which may store or alter any of the digestion products. When the products are released from the liver, they enter the general blood circulation

Fatty acids and glycerol combined to form fats again in the intestinal epithelium. These fats then pass into the lymphatic system which forms a network all over the body and eventually emptiesits contents into the bloodstream.

The blood will transport the digested simple food materials to body cells then,body cells take their requirements from blood.

Large Intestine It is the final part of the digestive tract

The large intestine consists of the following parts:

1. Caecum and appendix: It is a closed sac-like structure located in the beginning of the large intestine. In humans, appendix and caecum are small structure, possibly without digestive function. The appendix, however, contains lymphoid tissue and may have an immunological function.

2. Colon: It is starts after the caecum The colon is divided into three parts Ascending colon The transverse colon The descending colon

3. Rectum: It is a straight tube, which is located behind the bladder.

The Function of Large Intestine 1-Water absorption will occur in the large intestine. 2- Bile salts are absorbed and returned to the liver by the blood circulation 3-Keeping the waste material for a limited time, until it is excreted in suitable time. 4-The semi-solid waste, the faeces or stool is passed into the rectum by peristalsis and is expelled through anus.

Use of digested food 1- Glucose: During respiration in the cells, glucose is oxidized to carbon dioxide and water. This reaction provides energy for cells 2- Fats: These are built into cell membrane and other cell structure. Fats also form an important source of energy for cell metabolism. Fats can provide twice as much energy as sugars. 3- Amino acids These are absorbed by the cells and built up, with the aid of enzymes, into proteins a) Some of the proteins will become plasma proteins in the blood b) Others may form structures such as the cell membrane or c) They may become enzymes which control the chemical activity within the cell.

Storage of digested food If more food is taken in than the body needs for energy or for building tissues, it is stored in one of the following ways Glucose Excess amount of Glucose changes to Glycogen in Liver Some of the glycogen store in the liver and the rest in the muscles. Fat The fat is stored in adipose tissue in the abdomen, round the kidney and under the skin. These are the fat depots

Amino acids Amino acids are not stored in the body; those are not used in protein formation are deaminated. Excess amino acids are converted to glycogen in the liver. During this process, amino part of the amino acid is removed and changed to UREA which is later excreted by the Kidneys.

The LIVER İt is a large, reddish- brown organ which lies just beneath the diaphragm and partly overlaps the stomach. All the blood from the blood vessels of the alimentary canal passes through the liver. The functions of LIVER Liver has more than 500 functions, some of them; 1) Regulation of blood sugar After a meal, The liver removes excess glucose from the blood and stores it as Glycogen. Glucose ...... Glycogen In the periods between meals, when the glucose concentration in the blood starts to fall, the liver converts some of its stored Glycogen into glucose and releases it into the bloodstream. In this way, the concentration of sugar, in the blood is kept at a fairly steady level. 2) Production of Bile Cells in the liver make bile continuously and this is stored in the gall bladder. The bile contains bile salts which assist the digestion of fats 3) Deamination Excess amino acids are converted to Glycogen in the liver, During this process, Amino part of the amino acid is removed and changed to UREA. When the Amino group is removed from amino acids, it forms Amonia. Amonia is very poisonous to the body cells, and liver converts it at once to urea (harmless). 4) Storage of IRON Millions of red blood cells break down every day. The iron from the haemoglobin is stored in the liver. 5) Manufacture of plasma proteins The liver makes most of the proteins found in the blood plasma,such as fibronogen (it is involved in blood clotting) 6) Detoxication Poisonous compounds are converted to harmless substances, later excreted in the urine. 7) Storage of Vitamins Liver store fat soluble vitamins; vitamin A and vitamin D

Homeostasis The maintance of the internal environment within narrow limits is called homeostasis. Excretory System Excretion: throw out the metabolic wastes from body which are produced after cellular activities.

The Eliminations are sometimes confused. Elimination: Undigested and unabsorbed food materials are eliminated from the body in the feces. Such substances never participated in the organism’s chemical metabolism or entered body cells.

Digestion Undigested food

Absorption

Utilization of nutrients by cells

Metabolic wastes

EXCRETION ELIMINATION AS FECES

The functions of Excretory System:  Filtration and excretion of toxic wastes in the blood produced by the metabolic reactions of cells.  The maintenance of homeostasis by the balance of water and ionic content of the blood and tissue fluid.  The regulation of blood content.  The regulation of blood PH.  The regulation of blood glucose level.

The principal metabolic waste products are; 1. Water ( H2O )

2. Carbon dioxide ( CO2 ) 3. Nitrogenous wastes ( Ammonia, Urea, Uric Acid ) (a) Water and Carbon dioxide (H2O, CO2) - They are generated during the catabolism of carbohydrates and Lipids. Excreted by → Lungs, Kidney, and SWEATING.

(b) Nitrogenous wastes:

*Ammonia (NH3) Amino acids and Nucleic acids contain Nitrogen. During the breakdown of amino acids, the nitrogen containing amino group is removed (deamination) and converted to Ammonia. - Ammonia is highly toxic; some aquatic animals excrete it into the surrounding water.

* Uric Acid: Uric acid is produced both from ammonia and by the breakdown of nucleotides from nucleic acids. Uric acid forms crystals. Uric acid can be excreted as a crystalline paste with little fluid loss. Exp: Insects, certain reptiles, and birds.

* UREA: Urea is the principal nitrogenous waste product of amphibians and mammals. It’s produce mainly in the liver. Urea less toxic than Ammonia. Urea dissolves in water and is excreted by the Kidney.

THE HUMAN EXCRETORY SYSTEM The human excretory system composed of: 1. Kidney 2. Urinary tract (URETER) 3. Urinary bladder 4. URETHRA

THE KIDNEY The kidneys are two bean shaped organs located in the lower thoracic region of the body. The structure of Kidney: - The Kidney composed of four main parts Renal capsule, Cortex, Medulla and Pelvis.

1) Renal Capsule: It’s a fibrous layer of connective tissue which surrounds the Kidney. 2) CORTEX: It’s located below the fibrous coat. It’s red in color and contains the malpighon bodies (Bowman’s capsule and glomerulus) 3) MEDULLA: It’s located below the cortex. Urinary tracts which drain from the cortex form pyramids. The tip of each pyramid is a renal papilla. Each papilla has several pores, the opening of collecting ducts. As urine is produced it flows through the openings of the collecting ducts, and into the Renal pelvis. 4) Renal Pelvis: It forms the innermost portion of the Kidney. Its function is the collection of urine from the pyramids. The pelvis transmits the accumulated urine to the Ureter.

THE NEPHRON IS THE FUNCTIONAL UNIT OF THE KIDNEY Each kidney is made up of more than million functional units called nephron. Each nephron consists of: 1- Bowman’s Capsule and Glomerulus 2- Proximal Convoluted Tubule 3- Loop of Henle 4- Distal Convoluted Tubule URINARY TRACT 5- Collecting Duct

1) Bowman’s Capsule:

- Semi-spherical structure - The inner surface consists of squamous epithelial cells.

2) Glomerulus: - Blood is delivered to the kidney by the renal artery. - Small branches of renal artery give rise to efferent arterioles. - Glomerulus is formed by capillaries from a branch of the efferent renal arteriole. - The capillaries exit the Bowman’s capsule with the efferent arteriole (Blood pressure is high in the capillaries of the glomerulus due to its position between two arterioles) - These capillaries thicker than other capillaries.

URINARY TRACT: - After the Malpighian body (Bowman’s capsule & Glomerulus), proximal convoluted tubule is there, proximal convoluted tubule extends into the loop of Henle and then into the distal convoluted tubule (the total length approximately 50cm Urinary tract) - Loop of Henle extends into medulla of kidney. - Renal artery: It transports blood rich in oxygen and waste.

- Renal Vein: It transports blood is in CO2 with only a small amount of waste.

FILTRATION: Filtration occurs at the function of the glomerular capillaries and the wall of Bowman’s capsule. Blood flows throw the glomerular capillaries under high pressure, forcing more than 10% of the plasma out of the capillaries and pass into the Bowman’s capsule. Small materials, such as glucose, amino acids, sodium, potassium, chloride, bicarbonate, and other ions and urea pass through the capillaries into the Bowman’s capsule, and become part of the FILTRATE. Blood cells, plasma proteins, and lipid molecules, remain, in capillaries. - The total volume of blood passing through the kidneys is about 1200ml per minute.

REABSORPTION: (proximal convoluted tubule) The simple epithelial cells lining the renal tubule are well adapted for reabsorbing materials. They have abundant microvilli, which increase the surface area of reabsorption. About 65% of the filtrate is reabsorbed as it passes through the proximal convoluted tubule. The-proximal convoluted tubule is isotonic to the tissues, its density is equal to that of the tissue. Glucose Amino acids Vitamins Other substances of nutritional value are reabsorbed there. There are many ions including: - Sodium - Chloride - Bicarbonate - Potassium

LOOP OF HENLE: Urine is concentrated at the loop of Henle. - Loop of Henle a structure composed of two parole descending and ascending arm. - The direction of flow in each arm is the reverse of the other Cl ions are reabsorbed by active transport in the ascending arm Na ions are reabsorbed by passively reabsorbed.

The concentrated urine then flows to the convoluted tubule.

Distal Convoluted Tubule: - Water is reabsorbed in this region. - Its permeability to water is regulated by vasopressin (ADH) - It’s secreted when the concentration of the blood increases. - As a result reabsorption of water from the collecting ducts.

Secretion: Some substances especially potassium, hydrogen and ammonium ions are secreted from the blood into the filtrate. Certain drugs such as penicillin are also removed from the blood into the filtrate. Secretion occurs mainly in the region of the distal convoluted tubule. Secretions have been retained by the tubules.

Urine is composed of: 98% water 2.5% Nitrogenous wastes (Primarily Urine) 1.5% Salts and traces of other substances such as bile pigments, which may contribute to the characteristic color.

Urine volume is regulated by the hormone ADH. When are drinks a great deal of water, the blood becomes diluted and its osmotic pressure Release of ADH to the pituitary gland, decreases, lessening the amount of water reabsorbed from the collecting ducts. A large volume of diluted urine is produced. Sodium reabsorption is regulated by the hormone Aldesterone. Sodium is the most abundant extra cellular ion, accounting for about 90% of all positive ions out side cells. Concentration of sodium is precisely regulated by the hormone ALDESTERONE, (secreted by the cortex of the adrenal gland).