mechanism of urine formation plz plz help me
Answers
the mechanism can't be explained in short if you wanna to cut something then u can so this is your ans:-
There are three steps/ process involved in the formation of urine ,[1]
Glomerular Filtration
Selective Reabsorption
Tubular Secretion
Filtration in the kidney through glomerulus
The substance get filtrate in glomerulus is similar to the component of plasma with exception of proteins and blood cells.
Blood cells, plasma proteins and other large molecules are too large in size to filter and remain in the capillaries.
Process of filtration take place through glomerulus & glomerulus capsule through semipermeable membrane.
Water and other small molecules readily get absorbed.
Why filtration take place in the body?
Filtration occure due to difference between the blood pressure in the glomerulus & filtrate pressure in glomerular capsule.
The volume of filtrate formed by both kidneys each minute is called glomerular filtration rate.
In a healthy adult, Normal gfr is about 125ml/min. i.e. 180 litres of filtrate is formed of which only 1% get excreted as urine.
Selective Reabsorption
Process of reabsorption is done through two processes,
Active Transport
Passive Transport
Active transport take place at a carrier site in the epithelial membrane by using chemical energy to transport the substance.
Some ions, Chloride and sodium absorption in the kidney done by both active and passive mechanism.
Water, electrolytes and organic nutrients are passively absorbed in renal tubule.
Renal tubule are of distal convoluted tubule and proximal convoluted tubule.
Most reabsorption takes place in proximal convoluted tubule, whose walls are lined by microvilli to increase surface area for absorption.
Kidneys maximum capacity for reabsorption of substances is called as transport maximum or renal threshold.
For ex. Normal blood glucose level -- 63 to 144 mg/100mL if this rises above the transport maximum of about 160 mg/100ml than glucose appear in the urine.
Tubular Secretion
Tubular secretion is the process by which the substances are transported from blood into renal tubule.
Tubular reabsorption take place in distal and convoluted tubule and some substance secreted into the lumen from the peritubular capillaries through the tubular epithelial cells.
Potassium regulation is done actively by sodium-potassium pump in proximal and distal convoluted tubules and collecting ducts
Ammonia is secreted in the proximal convoluted tubule.
Summary of formation of urine in the kidney
Plasma is filtrate in glomeruli next the substance reach the renal tubule along with water as filtrate.
The 99% of filtrate is reabsorbed in different segments of renal tubule.
Last stage, tubular secretion are transported fr blood into the renal tubule. With all this changes, the filtrate becomes urine.
hope this helps buddy ^-^ may it go through your mind ........................
Ultrafiltration, where almost all the blood components are filtered by the kidneys except for the blood cells and the plasma proteins, e.g. urea, water, sodium, glucose, potassium, ...etc.
Selective reabsorption, where the essential components are reabsorbed back into the blood vessels, e.g. glucose, water, sodium, ...etc.
Secretion, where, e.g. potassium is secreted by cells in exchange for another useful component, e.g. sodium in that case.
Then the water reabosprtion content is further regulated before exiting the kidney through a hormone known as ADH.
Urine is then formed, collected in the bladder and excreted outside the body later on