Excretory Products And Their Elimination NEET Study Material

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Excretory Products And Their Elimination Notes For NEET


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INTRODUCTION

Many nitrogen containing substances, ions, CO2, water, etc., that accumulate in the body have to be eliminated. Nature of nitrogenous wastes formed and their excretion vary among animals, mainly depending on the habitat (availability of water). Ammonia, urea and uric acid are the major nitrogenous wastes excreted. Protonephridia, nephridia, malpighian tubules, green glands and the kidneys are the common excretory organs in animals. They not only eliminate nitrogenous wastes but also help in the maintenance of ionic and acid-base balance of body
fluids. In humans, the excretory system consists of one pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Each kidney has over a million tubular structures called nephrons. Nephron is the functional unit of kidney and has two portions – glomerulus and renal tubule. Glomerulus is a tuft of capillaries formed from afferent arterioles, fine branches of renal artery. The renal tubule starts with a double walled Bowman’s capsule and is further differentiated into a proximal convoluted tubule (PCT), Henle’s loop (HL) and distal convoluted tubule (DCT). The DCTs of many nephrons join to a common collecting duct many of which ultimately open into the
renal pelvis through the medullary pyramids. The Bowman’s capsule encloses the glomerulus to form Malpighian or renal corpuscle. Urine formation involves three main processes, i.e., filtration, reabsorption.

excetory products and their elimination

Topics

19.1  Modes Of  Excertion

19.2  Human Excertory System

19.3  Urine Formation

19.4  Mechanism Of Concentration Of The Filtrate

19.5  Regulation Of Kideny Function

19.6  Micturition

19.7  Role Of Other Organs In Excertion

19.8  Disorder Of The Excertory System