the process of removal of nitrogenous wastes along with excess of water ,minerals ,saltsiment out of the body is called excretion .the organs and its physiology which are involved in excretion collectively called excretory
It regulates the chemical composition of body fluid ,by removing metabolic wastes and retainin the proper amount of water ,salts and nitrogens .
the kidney are responsible for filtering toxins wastes ,ingested water and mineral salts out of the regulation the acidity of the blood by excreting alkaline salts when necessary .
it is an evolutionary modification of the nephridium is the kidney functional unit or the nephron is the basic excretory unit of kidney .There are over million in each kidney each is of is about 6 cm long,
components of the nephrones .
the glomerulus is small knot of blood vessels formed by capillary network of the renal artery the smaller efferent vessels takes blood away from the glomerulus and enter the capillary network around the tubules of the nephron.
2 bowman’s capsule
the glomerulus is surrounded by doubled walled cup shaped structure called bowmans capsule .the outer wall is called parietal layer .Which is thinner and inner layer iss called visceral layer the space between the two is called" capsular space visceral layer".Which is made of specialized epithelium celss podocytes .
3 proximal convulated tubules
the proximal convulated tubules is long and coiled tube arises from the posterior end of bowmans capsules.
4 loop of henle
it runs straight in renal medulla.it is U shaped tubules structure formed by a thin descending limb and thick ascending limb.
Distal convulated tubules .
it is a convulated part and is again present in the cortex .
6 collecting duct
the collecting duct are longer tubes each receviving about eight uriniferous tubules and each collecting duct pass into renal medulla and join to each other foring still ultimately leads into pelvis .
7 ranal blood supply
each kindey is supplied is supplied by renal artery directly from the dorsal aorta inside the kidney renal artey divides into a number of major braches called interlobar artreis.An afferent arteiols enter the cavity of bowmans capsule and forms a tuft of capillaries called golmerulus.
from the hilum of each kidney arises a narrow muscular and tubular structure the ureter . it is about 25 to 30 cam long it is internally lined by trasitioal epithelium surrounded by, a layer of muscular fibres followed by a layer of connective tissue it coveys a urine from the kidney into the urinary bladder .
the bladder is alge thin walled pear shaped sac like organ composed of musculomembrane fibres. it can hold about 0.5 liter of urine it is situated behind the pubic symphysis in male and in front of the uterus in the female externalled lined by losses connective tissue and blood and lymphatics vessels with nere and internally lined by transitional epithelium.
from the urinary bladder arise a membrane tube known as urethra. it is a vessels of transport for urine conveying .it from the urnary bladder and join the ejaculatory duct from urinogentinal canal .Which passes through and forward behind the symphysis pubis and opens through external urethral orifice very close o vagina.
1 excrete toxi c metabolism by production such as urea ammonia and uric acid .
2 maintain volumn of exta cellula fluid .
3 maintain ionic blanace in extra celluar fluid .
4 maintain PH and osmotic concentration of extra celluar fluid .
5 kindey perfrom of homeostatic fucnction .
6 help to eliminated excess blood sugar , drug vitamin hormones .
7 secrete hormone rennin which help in glomerular filtration.
the metabolic wastes which are formed inside all the living cells of body .these are transported to the kidney by blood where these are changed into urine the formation of urine involved. the processes ultra filtration selective reabsorption and tubular secretion.
the blood pressure is glomrular capillaries of"bownmans capsule" is about twice as that in capillary network. it is due to larger diameter of afferent vessel than the efferent vessels bring the blood into the gomerulaus tubules the endothelial cells of blood vessels and the single celllining the "bowmans capsule", form a semi permeable membrane the blood entering the capsule under pressure this filtration under pressure is called "ultra filtration" which is entirely passive process hydrostatic blood pressure. in glomerular capillaries is about 75 mm HG add .This pressure of fluid presnt indide the ranal tubule is about 10 mm Hg so the effective filtration pressure which is responsible at which the blood enter the glomerulust.And the sum of these pressure which is resist the hydrostatics prsuure is called GFR .its normally 25 mmHg .
they are islated to plasmaand has the same composition of blood except it does not contain blood cells and protens this GFR includes a number of large amount of water and small sized soluble useful subsutance like glucose amino acid vit C na and number of harmful substance like urea , uric acid , cretinine , ammonium salts , pigments etc . this filtration is called ultrafiltration nephrone filtrates 125 ml of body fluid per minutes filtering the entires body fluid compsed 16 times each days in 24 hours period nephrone peroduce 180 litre of filtrates of which 178.5 litres are reabsorbed the ramaing 1.5 litres form the urine.
the maintance by organism of an internal blance between water and dissolved material regardless of environment conditions is called "osmoregulation". the excretory system is also responsible for regulation of water balance in various body fluid terrestrial animals use a variet of methods to reduce water loss . living environment in mosit environment ,developing impermeable a body convering production of more concetntrated urine water loss can be considerable a person in 100 degrre F temperratureloses 1 liter of water per hour .
it is process of keeping a constant amount of water and salts in the blood our bodies need to constantly replaces the water being lost in breathing sweating urine and faces as our cells cannt function without sufficient water .If there is too much water in our bodies however. it will move by mosmosis into the cell which may swell or even brust a balace is needed and aains it is the hypothalamus which maintains this balance .
if you loss water from too much of sweating your bodys feed back meachnism ouccus and causes an stimulation on the pituitary to release ADH. ADH stops theremoval of water from the blood in the kindey so blood water level returns to normal which is also know to be as homeostatis.
Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069
Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.
Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.