Question

1. "Describe the three processes for urine formation and describe the role of the various regions of the kidney in the process of reabsorption"

2. "Discuss the regulation of chloride ions, potassium ions, calcium ions, magnesium ions, and phosphate ions"

Answer 1

Urine Formation involves three Steps-

1.Glomerular Filtration.

2.Reabsorption

3.Secreation

1.Glomerular filtration:

This is the 1st step in Urine formation.The process of glomerular filtration occur by Ultrafiltration.

The force of hydrostatic pressure in the glomerulus (the pressure exerted from the pressure of the blood vessel-Afferent arteriole and efferent arteriole) is the driving force that pushes filtrate out of the capillaries (Afferent and effernt glomerular capillary)a into the Bowmans Capsule .

Here all the substances in the blood are not filtered into Bowmans capsule.Filterd components in the blood include-water, nitrogenous waste, and nutrients ,which are passed into the filtrate that passes into renal tubule

Non filterable components in the blood inculde-blood cells, albumins, and platelets  that will leave the glomerulus through the efferent arteriole.

2.Secreation:

This is the transfer of substances from peritubular capillaries to the lumen of Renal tubule.This secretion occur by active transport and passive diffusion-

Substances that are secreated into the tubular lumen include- H+, K+,creatinine, histamine,NH3, urea and drugs like penicillin.

3.Reabsorption:

this is the process by which the renal tubule removes water and solutes from the tubular fluid to the circulating blood.That is from lumen into Peritubular capillaries(Remember in Secreation substances moving from peritubular capillaries into Lumen)

Most of the reabsorption occur in PCT-Na+(65-70%),Cl-,K+,amino acids,urea,glucose,H2O are reabsorbed

In the descending limb of Henles Loop-Water is reabsorbed

In the Ascending Limb of Henles Loop-Na+(25%),Cl- and K+ are reabsorbed through Na+K+ 2 Cl- pump

In the DCT-Na+(5%) and cl- are reabsorbed as Nacl

And in the collecting Duct 1-2 % of Na + is reabsorbed

2.

Regulations-

*Chloride ions-Chloride Ions are Reabsorbed in the renal tubules along with Na+ as Nacl in the PCT,DCT ,Collecting duct.Also Through the Na+Ka+-2Cl- Pump

Potassium ion-

Potassium reabsorbtion occur in ascending limb of henles loop through Na+Ka+-2Cl- Pump

Potassium Secreation Occur in the Collecting duct through Na+-K+H+ Antiport(Na+ is reabsorbed ,H+ and K+ Secreated)

Similarly Based on the Hormonal Influence and Ionic Concentration of Ca 2+,Mg2+ and Phosphate ions ,Their reabsorbtion and secreation is varied through which a plasma concentration of these ions are maintained.