Changes

* Podocytes

* Podocytes

===Fenestrated Capillary Endothelium===

====Fenestrated Capillary Endothelium====

* There are small gaps called fenestrae in the cytoplasm of the capillary endothelium.   

* There are small gaps called fenestrae in the cytoplasm of the capillary endothelium.   

* They act mainly as a barrier to the cells of the blood

* They act mainly as a barrier to the cells of the blood

===Glomerular Basement Membrane===

====Glomerular Basement Membrane====

* Also known as the '''basal lamina'''

* Also known as the '''basal lamina'''

* Lower permeability to anions compared to cations.  This allows for further selective filtration

* Lower permeability to anions compared to cations.  This allows for further selective filtration

===Podocytes===

====Podocytes====

The cells of the visceral layer of the Bowmans capsule posses finger like foot processes called pedicels.  These wrap around the outer layer of the basal lamina.  Filtration occurs through small gaps between pedicels called slit diaphragms. This is the final barrier against proteins

The cells of the visceral layer of the Bowmans capsule posses finger like foot processes called pedicels.  These wrap around the outer layer of the basal lamina.  Filtration occurs through small gaps between pedicels called slit diaphragms. This is the final barrier against proteins

==Factors Which Determine Selective Filtration==

===Factors Which Determine Selective Filtration===

* Hydrostatic pressure in the capillaries causes filtration but as the filtrate is basically protein free there is no real protein osmotic pressure in the Bowmans capsule.  This means the filtration is almost entirely powered by the hydrostatic pressure in the capillaries.

* Hydrostatic pressure in the capillaries causes filtration but as the filtrate is basically protein free there is no real protein osmotic pressure in the Bowmans capsule.  This means the filtration is almost entirely powered by the hydrostatic pressure in the capillaries.

* Molecular size - molecules with a radius of 4nm or more aren't filtered, whilst those with a radius less than 2nm are filtered without restriction. Thus the filtration barrier is selectively permeable.

* Molecular size - molecules with a radius of 4nm or more aren't filtered, whilst those with a radius less than 2nm are filtered without restriction. Thus the filtration barrier is selectively permeable.

** The higher the rigidity of a molecule the less easily it is filtered

** The higher the rigidity of a molecule the less easily it is filtered

==Composition of Filtrate==

===Composition of Filtrate===

* Normal filtrate is basically protein free.

* Normal filtrate is basically protein free.

* Charged molecules over 70,000 Da are not filtered at all

* Charged molecules over 70,000 Da are not filtered at all

* The threshold for neutral molecules is 100,000 Da

* The threshold for neutral molecules is 100,000 Da

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