ExcrePATEins PDF

Shadiya Nidaire 4. EXCRETORY PRODUCTS AND THEIR ELIMINATION Excretion is the elimination of metabolic wastes like ammonia, urea, uric acid etc. from the tissues. Types of excretion 3. Uricotelism Process of excretio...

Shadiya Nidaire 4. EXCRETORY PRODUCTS AND THEIR ELIMINATION Excretion is the elimination of metabolic wastes like ammonia, urea, uric acid etc. from the tissues. Types of excretion 3. Uricotelism Process of excretion of uric acid. It is 1. Ammonotelism: Process of excretion of NH3. insoluble in water. So water is not required for excretion. Ammonotelic animals: Aquatic invertebrates, bony Uricotelic animals: Birds, terrestrial reptiles, insects, fishes, aquatic amphibians, aquatic insects etc. NH; is land snails and some land crustaceans. highly toxic. So excretion needs excess of water. Ureotelism & uricolelism are needed for water conservation. NH; is readily soluble in water and is excreted by Some excretory organs in animals diffusion across body surfaces or through gill surfaces (in Protonephridia(flame cells): In Flatworms, rotiſers, lishes) as ammonium ions. Kidneys do not play any some annelids & cephalochordate. Protonephridia are significant role in its removal, primarily for osmoregulation. 2. Ureotelism: Process of excrction of urca. Nephridia: In Annelids. Help in the removal of Ureotelic animals: Mammals, terrestrial & semi-aquatic nitrogenous wastes and osmoregulation amphibians (frogs, toads ctc.), cartilaginous fishes,. Malpighian tubules: In Insects. Help in the removal of aquatic or semi-aquatic reptiles (alligators, turtles) etc. nitrogenous wastes and osmoregulation. In liver, NH; is converted into less toxic urea. So it requires Antennal or green glands: In Crustaceans (prawn etc.) only moderate quantity of water for excretion. Kidneys: In Higher animals. HUMAN EXCRETORY SYSTEM It includes a pair of kidneys, a pair of ureters, a urinary o Renal tubule: It begins with a double walled cup-like bladder and a urethra. Bowman's capsule, which encloses the glomerulus. Structure of KidneyPenal Glomerulus+ Bowman's capsule = Malpighian body covere - Reddish brown, bean-shaped structures situated between The (ubule continues with proximal convoluted tubule the levels of last thoracic and 3rd lumbar vertebra. (PCT), Henle's loop & distal convoluted tubule (DCT). Length: 10-12 cm, width: 5-7 cm, thickness: 2-3 cm. - Henle's loop is hairpin-shaped. It has descending and Averageweight: 120-170 gm. ascending limbs.. It is enclosed in a tough, 3-layered fibrous renal capsule. The DCTs of many nephrons open into a collectingduct. On the concave sideof kidney, there is an opening (hilum Collecting duct extends from cortex to inner parts o! ITIES or hilus) through which blood vessels, nerves, lymphatic medulla. They converge and open into the renal pelvis ducts and ureter enter the kidney - Hilum leads to funnel shaped cavity called rename Malpighian body (Renal corpusele), PCT and DCT are with projections called calyces. situated in renal cortex. Loop of Henle dips into medulla. Each kidney has outer cortex and inner medulla. The efferent arteriole emerging from glomerulus forms a Medulla has few conical projections called medullary finc capillary network (peritubular capillaries) around the pyramids (renal pyramids) projecting into the calyces. renal tubule. A minute vessel of this network runs parallel Cortex extends in between the medullary pyramids as to Henle's loop forming a 'U'shaped vasa recta. renal columns Columns of Bertini). - Each kidney has nearly one million tubular nephrons. Types of nephrons Nephron 1. Cortical nephrons (85%): In this, the Henle's loop is Nephrons are the structural & functional units of kidney. short and extends only very little into the medulla. Vasa Each nephron has 2 parts: Glomerulus & Renal tubule. recta is absent or highly reduced. o Glomerulus: A tuft of capillarics formed by afferent 2. Juxtamedullary nephrons(15%): In this, Henle's loop is arteriole (a fine branch of renal artery). Blood from the long and runs deep into medulla. Vasa recta present. glomerulus is carried away by an efferent arteriole. WDURINE FORMATION (PHYSIOLOGY OF KIDNEY) 3 processes: Glomerular filtration, reabsorption & secretion. - Almost all constituents of the blood plasma except the 1. Glomerular filtration (ultrafiltration) proteins pass onto the lumen of the Bowman's capsule. - The glomerular capillary blood pressure causes filtration About 1100-1200 ml of blood is filtered by the kidneys of blood through 3 layers, i.e. endothelium of per minute. It constitutes 1/5" of the blood pumped out by glomerular blood vessels, epithelium of Bowman's , cach ventricle of the heart in a minute. capsule & a basement membrane between these 2 layers. The amount of the filtrate formed per minute is called The epithelial cells (podocytes) of the Bowman's capsule Glomerular filtration rate (GFR). are arranged in an intricate manner so as to leave some Normal GFR = 125 ml/minute, i.e., 180 litres/day. minutc spaces called filtration slits (slit pores). No Ich-By