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1-Introduction 2-Excretory organs 3- Excretory products 4-Physilogy of excretion 5- Importance of excretion 6-Disorder of kidney Introduction The removal of toxic , waste metabolic products from the body is known as excretion.All plants and animals produces harmful substances during metabolic activities such as co2 ,ammonia, urea and uric acid. Excretory organs SKIN LUNGS RECTUM LIVER KIDNEY Excretory organs 1-SKIN- Skin is the one of the excretory organs which remove salts and other metabolic wastes of body cells through sweat and regulate body temperature. Lungs:-Lungs help in the release of carbon dioxide from the body which is formed during respiration. Liver- liver also performs excretory functions which are as follows :1 – Bile pigments are produced in liver which are discharged in the alimentry canal 2-Liver converts harmful toxic substances into harmless substances which are formed during metabolic activities. LIVER Rectum r Solid wastes containing undigested food are removed through anus . Stomach Intestine Rectum Anus The Kidney The human kidneys: are two bean-shaped organs, one on each side of the backbone. Represent about 0.5% of the total weight of the body, But receive 20–25% of the total arterial blood pumped by the heart. Each contains from one to two million nephrons. Internal structureIn longitudinal Section We see Renal cortex outer part having Malpighian corpuscles . Medulla having Henley's loop and collecting tubules Each kidney is made up of numerous (about one million ) coiled tubules , known as uriniferous tubules or nephrons . In other words , nephron is the structural and functional unit of kidney. NEPHRON (URINIFEROUS TUBULES) THE NEPHRON The nephron is a tube; closed at one end, open at the other. It consists of a: •Bowman's capsule. Located at the closed end, the wall of the nephron is pushed in forming a double-walled chamber. •Glomerulus. A capillary network within the Bowman's capsule. Blood leaving the glomerulus passes into a second capillary network (not shown in the figure) surrounding the •Proximal convoluted tubule. Coiled and lined with cells carpeted with microvilli and stuffed with mitochondria. •Loop of Henle. It makes a hairpin turn and returns to the •Distal convoluted tubule, which is also highly coiled and surrounded by capillaries. •Collecting tubule. It leads to the pelvis of the kidney from where urine flows to the bladder and, periodically, on to the outside world. Fuction of kidney:-Kidneys play an important role in regulating the composition of blood by filteration . They maintain mineral balance ,exact proportion of water and acid –alkali balance in the blood .They regulate the osmatic pressure of the body. Filtration of blood Filtration Formation of Urine The nephron makes urine by filtering the blood of its small molecules and ionsand then reclaiming the needed amounts of useful materials. Surplus or waste molecules and ions are left to flow out as urine The steps: Blood enters the glomerulus under pressure. This causes water, small molecules (but not macromolecules like proteins) and ions to filter through the capillary walls into the Bowman's capsule. This fluid is called nephric filtrate. As the table shows, it is simply blood plasma minus almost all of the plasma proteins. Essentially it is no different from interstitial fluid. Process of urine formation IMPORTENCE OF EXCRETION 1-It regulate pH , osmotic pressure and structure of body. 2- Harmful byproducts throw away from body. 3- It maintain Homeostasis. Disorder of Kidney 1- Dialysis – Kidney function less urea increase in blood . The urea is separated from body by dialysis. 2-Diuresis –dilute urine comes due to increase water ,less secretion of ADH .Increase BP. 3-Kidney stone –Oxilate crystal collect and chock tubules .It is treated by laser rays Point to remember •The removal of harmful, toxic wastes from the body is known as excretion. •Ammonia is the main nitrogenous waste formed in the body due to the metabolism of proteins. The •Solid wastes containing undigested food are removed through the anus and liquid nitrogenous wastes are excreted through skin and kidney. •Kidneys are the main organs of excretion in man which separate nitrogenous waste from blood . •In higher animals,liver ,lungs skin,rectum.and kidneys also constitute the excretory organs . •The nephron is the structural and functional unit of Exercise 1-What is excretion? 2-Name the main excretory organs of man? 3-Which is more toxic to body urea or ammonia 4- Name the structural and functional unit of kidney? 5- In the following which are metabolic wastes ? O2 , CO2,urea,glucose, fatty acids.ameno acids,ammonia. 6- What is the role of glomerulas in the kidney. We are Thankful to M. S. Encarta Microft I.T.Acadamy Mrs S. Kapoor ISAP Question paper Student data base Web site