Glomerular Filtration Rate

Urine formation is a result of three processes:

1) Glomerular Filtration

2) Tubular Reabsorption

3) Tubular secretion

Urine= Filtration – Absorption + Secretion

Glomerular Filtration:

Glomerular filtration is the filtration of protein free plasma from glomerular capillaries into bowman’s capsule.

This is the first step in urine formation.

Glomerular Filtration Rate:

The volume of glomerular filtrate formed per minute.

This is nearly 125 ml/min.

Glomerular Filtration Membrane:

It has three layers:

1) Capillary endothelial layer

2) Basement membrane

3) Podocyte layer

Determinants of Glomerular Filtration Rate:

1) Filtration Coefficient

2) Net filtration pressure

Regulation of Glomerular Filtration Rate:

There are three primary regulators:

1) Autoregulation

2) Neural control

3) Hormonal and autocoid control

Regulation of Urine Output:

There are two lines of defence:

1) Tubuloglomerular Feedback

2) Glomerulotubular Feedback

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Glomerular Filtration Rate