|
Unlimited Tutoring & Homework Help
|
|
Introduction
The nitrogenous waste materials produced in the animal body due to metabolic reactions are of no use to the cell. These waste materials if allowed to accumulate in the body, may become toxic. Therefore, they must be removed from the body. The process of elimination of metabolic waster products from the animal body to regulate the composition of the body fluids and tissues is called excretion.
Nitrogenous Waste Materials
These form the principal excretory product. They are formed mainly as the end product of protein metabolism. Some wastes are generated by the metabolism of nucleic acids. The principal nitrogenous waste product varies in different animals.
Types of Excretion
Different animals expel different nitrogenous compounds. On the basis of the type of nitrogenous end product.
Excretory System Of Cockroach
The excretory organ of cockroach is the malpighian tubules. It is found at the junction of the midgut and hind gut and are about 150 in number. They are fine, yellow coloured and branched threads present in bundles. They lie freely in the haemolymph.
Excretory System in Man
The excretory system in man is formed of one pair of kidneys, a pair of ureters, a urinary bladder and a urethra.
Structure of a Nephron
The nephron or uriniferous tubule is the functional unit of the kidney. A nephron consists of a twisted tubule closed at one end, open at the other with a network of associated blood vessels. Each kidney of man is formed of about one million nephrons.
Types Of Nephrons
A kidney receives the blood from the renal artery that arises from the dorsal aorta. In the kidney, the renal artery divides and subdivides to send an afferent arteriole into each Bowman's capsule. Here the afferent arteriole forms a bunch of about 50 parallel capillaries called glomerulus. These rejoin to form the efferent arteriole. The efferent arterioles forms a network in the cortex around the proximal and distal convoluted tubules of the nephron.
Formation And Composition Of Urine
The urine is a pale yellow coloured fluid. The yellow colour is due to the presence of urochrome pigment formed from the haemoglobin of dead RBC's in the liver cells. It is acidic in nature and has a pH of 6.0. It has a faint anamalic odour due to the presence of urinod. It soon gets a strong smell of ammonia which forms as a result of degradation of urea.
Counter Current Mechanism
Mammals and birds secrete a hypertonic urine. This is a main adaptation of land rentilates for the conservation of water. There are 2 counter current mechanisms operating inside the kidneys.
Kidney Failure Or Renal Failure
A partial or total inability of kidneys to carry on excretion and salt - water regulatory functions is called as kidney or renal failure.
Artificial Kidney
The haemodialyzer or artificial kidney is a machine used to filter the blood of a person whose kidneys are damaged. The process is called haemodialysis.
Renal Transplantation
Grafting a kidney from a donor who is compatible to the recipient to restore kidney functions in a recipient is called renal transplantation. All patients with renal failure are considered eligible for kidney transplantation.
Role Of Kidney In Osmoregulation
Osmo regulation is the process which regulates the concentration and osmotic pressure of blood by regulating the water contents of blood plasma. It is an important process as excessive loss of water may cause dehydration whereas excess of water intake may dilute the body fluids.
Role of Liver in Excretion
The liver is a multipurpose,largest gland in vertebrates. It plays a vital role in excretion of many substances.
Excretory Role Of Skin
Skin plays an important role in excretion in the mammals. Skin of mammals is glandular and has 2 types of glands, e.g., sebaceous glands and sudoriferous or sweat glands.
Summary
Excretion is the elimination of waste products from the body. The non - volatile products are mainly excreted in the urine. The urinary system consists of those organs which form, store and void urine.