EXCRETORY SYSTEM Metabolic wastes of the chemical reactions

EXCRETORY SYSTEM • Metabolic wastes of the chemical reactions in the cell are removed from the body. • This process is called EXCRETION.

FUNCTIONS OF EXCRETORY SYSTEM 1. Filtration and excretion of metabolic wastes 2. The regulation of blood content. 3. The regulation of blood p. H. 4. Homeostasis.

EXCRETORY SUBSTANCES The metabolic wastes of cells are; WATER, CO 2, NITROGENOUS COMPOUNDS

WATER and CO 2 • Water and CO 2 are formed by means of cellular respiration. • Water is excreted by lungs, sweating and kidneys. • CO 2 is excreted only by lungs.

NITROGENOUS WASTES • At the end of the catobolisation of aminoacids, AMMONIA(NH 3) is formed. • In some organisms, ammonia is removed fro body directly. • But in some organisms ammonia is converted to other substances such as UREA and URIC ACID.

AMMONIA (NH 3) • Ammonia is the most toxic nitrogenous waste material. • It can soluble in water. • Organisms need large amount of water for excretion of ammonia. • Organisms need small amount of energy formation of NH 3 • Ammonia is excretory substances of freshwater organisms.

UREA [CO (NH 2)2] • Urea is less toxic than ammonia. • It is formed in the liver by ornithin cycle. • Urea is excreted by the kidney. • Urea is the excretory substances of amphibians, mammals, fish and human. • Organisms use more energy in formation of urea than ammonia. • Living things need normal amount of water.

URIC ACID (C 5 NH 4 O 3) • Uric Acid is least toxic nitrogenous waste. • It is insoluble in water. • Uric acid is excreted by with only small amount of water. • Uric acid is the excretory substance of terrestial organisms such as INSECTS, REPTILES AND BIRDS.

The excretory and reproductive system of vertebrates are interrelated and this complex is called UROGENITAL SYSTEM • The kidney is the main excretory organ of vertebrates.

TYPES OF KIDNEYS There are three types of Kidneys; a) Pronephros kidney b) Mesonephros kidney c) Metanephros kidney

PRONEPHROS KIDNEY • Pronephros kidney is found in the embryonic stage of fish and amphibia and in adult form of shark. • Pronephros kidneys contain many nephridia. • Nephridia have ciliary funnels that is connected to ball of capillaries or glomerulus by ciliary funnels.

MESONEPHROS KIDNEY • Mesonephros kidney is found in embryonic stage of reptiles, birds an mammals and adutlt stage of fish and amphibia. • In mesonephros kidney, ciliary funnels are replaced with Bowman’s capsules. • A glomerulus is located in Bowman’s capsule. Waste materials pass to Bowman’s capsule from glomerulus.

METANEPHROS KIDNEY • Metanephros kidney is found in adult reptiles, birds, mammals and human. • Each kidney contains a millions of nephrons.

CLOACA • In fish, amphibians, reptiles and birds; excretory substances, unigested materials and reproductive cells are expelled through the same channel or openin that called CLOACA.

PARTS OF HUMAN EXCRETORY SYSTEM 1. Kidneys 2. Ureter 3. Urinary bladder 4. Urethra

KIDNEY • Kidneys are bean shaped organs that filtere 180 lt. blood in a day. • Blood is come into kidney by renal artery. • Filtered blood leaves from kidney by renal vein.

FUNCTIONS OF KIDNEY 1. They remove wastes of cellular metabolism from the blood. 2. They control concentration of various substances found in the body fluid.

STRUCTURE OF KIDNEY 1. Cortex: It contains glomerulus and Bowman’s capsules. 2. Renal Capsule: It surrounds and protects the kidneys.

3. Medulla: It is located under the cortex and has malphigian pyramids. Malphigian pyramids contains urine collecting canal and loop of henle. 4. Pelvis: It is innermost part of kidney. The urine is collected in pelvis.

NEPHRONS • They are structural unit of kidneys. • A nephron begins with a glomerulus. • Glomerulus is surrounded by a Bowman’s capsule. • Each glomerulus is formed by capillaries from a branch of renal arteriole.

• The complex of Bowman’s capsule and glomerulus is called malpighian body. Bowman’s capsule is connected with long tubule that is called Loop of Henle. • Loop of Henle is joined with collecting duct.

URINE FORMATION There are three steps during urine formation. 1. Filtration 2. Reabsorbtion 3. Secretion

FILTRATION • During filtration, substances pass from the blood into the Bowman’s capsule. • Under pressure, water and many small molecules such as salts, urea, glucose and aminoacids pass from glomerulus into Bowman’s capsule.

REABSORBTION • The absorbtion of needed materials such as glucose, amino acids and water from nephrons to blood capillaries is called reabsorbtion. • Water is reabsorbed passively by osmosis. But reabsorbtion of glucose, aminoacids and salt ions occurs by active transport.

• All glucose, aminoacids and many salt ions are reabsorb during reabsorption. • Most reabsorbtion takes places in loop of henle. • Antidiuretic hormone (ADH or Vasopressin) regulates concentration of water in blood. • It increases water permeablity of the cells of the distal tubules.

SECRETION • The cells of distal tubule excrete molecules such as penicilin, ammonia, potassium and excess acids. This process is called secretion. • After secretion, the fluid remaining in the nephrons is called urine. • Urine contains urea, uric acid, sodium, potassium, calcium, chlorine, phosphorus, water and small amount of cells.

• Urine flows from the tubules into the collecting ducts and it is stored temporary in pelvis. • Than urine is transported into the urinary bladder by the urether of each kidney. • And than it is expelled through the urethra.