Podocytes glomerular capillary wall

Contractile elements of the podocyte foot processes, which may influence the hydraulic permeability of the glomerular capillary wall, may be regulated via vasoactive hormones. Receptors for some vasoactive hormones, for example, en-dothelin (R4), atrial natriuretic peptide (S9), nitric oxide (K22), and angiotensin n (Yl), have been described on the podocyte surface. 

Figure 2.16b shows the structure of the glomerular vessel wall. The interior is covered by endothelial cells with multiple holes ( fenestrations ). The podocytes (= foot cells ) form a likewise discontinuous outer layer. Between them is an acellular basal membrane, consisting of proteins and proteoglycans, which has the smallest pore diameter of all three and therefore, as in any the capillaries found elsewhere in the body, represents the effective filter layer. The filter has a cut-off size of very few nanometers, so that most protein molecules will be retained. Salt ions and small molecules - if they are not protein-bound - will be filtrated. The amount of filtrate produced is about 1501 per day in a healthy adult this corresponds to about 1/10 of the blood plasma volume that passes the kidneys. 

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