= Podocyte foot process
A <podocyte foot process> is a fine extension of a <podocyte> that lies against the glomerular <basement membrane>. Neighboring <podocyte foot process> structures interdigitate, leaving narrow filtration slits crossed by a <slit diaphragm>. The <podocyte> is one whole <epithelial cell>; its many processes collectively shape part of the <glomerular filtration barrier>.
An <electron microscope> section makes the distinction concrete: identify the <basement membrane>, then the small profiles resting on its outer side, then the gaps between those profiles. A profile is not necessarily a separate <cell>; multiple profiles can belong to branches of one <podocyte>. Conversely, the gap between two profiles is not itself a <podocyte foot process>.
In a 1999 study, <immunogold labeling> placed <nephrin> at the slits between these processes. Figure3 includes sections across the slit and a tangential view with a row of gold particles. Combining the label with the local geometry helped locate a <protein> at a junction rather than merely somewhere in the <glomerulus>.<Nephrin is specifically located at the slit diaphragm of glomerular podocytes by V. Ruotsalainen and others>[Abstract; Figure3A–D]{ref}
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