Question

1. Describe the three processes that are important for the formation of urine?
2. Trace the pathway of urine. From where it is produced to where it is released. describe, please

Answer 1

Three different stages in the formation of urine are:

(a) Glomerular filtration

(b) selective reabsorption.

(c) Tubular secretion

(a) Glomerular filtration-(a) Glomerular filtration is the first step of urine formation,it is protein free filtrate.it is carried out by by the glomerulus.it is physiological function of kidney.kidney filter about 1100-1200 ml /minute.there are three layer involve in glmerulus filtration (I)endothelium of glomerulus blood vessels (ii)the epithelium of bowman's capsule (iii) basement membrane lies betwen above two lyer.some slits pores present in epithelial cells of bowman's capsule here high pressure in the glomerulus capallaries the substance filter in these pores.it is very fine process so it is called ultrafiltration.

(b) selective reabsorption- It is second step of urin formation.the GFR rate of kidney is 1.5 urine released after filtration of 180l blood.so 99 % material in the filtrtate reaborbed by the tubules.these reabsorption is done by passive or active tranportation.material means water, urea(passive transport),glucose and amino acids (active transport),reabsorption of Na+ by passive andf active transport.

(c) Tubular secretion-It is very important process and highly selective process.in this process removal of certain chemicals from the blood which are not filtrate secrete them in to nephric filtrate certain chemicals like uric acid ,creatinine k+,ammonia.only active transport is involved.

                                  Pathway of urine

Urine transport following pathways

                              kidneys

                             ureters

                              urinary bladder,

                              urethra

which are collectively known as the urinary tract.

Urine is formed in the kidneys urine is then passed through the ureters to the bladder passed from the bladder through the urethra to the body