Podocytes , visceral epithelial cells - cells in the capsules of Bowman - Shumlyansky kidneys , which cover the glomerular capillaries . Bowman's capsules filter the blood without passing large molecules such as proteins , and passing small molecules such as water, salts, and sugars. This filtration is the first stage of urine formation.
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 The structure of the renal corpuscles Blood flows into the bringing arteriole (9) above, and from the carrying arteriole (11) below. Blood flows through the capillaries of the glomerulus (10), where it is filtered by pressure. Podocytes (3b) cover the capillaries. Blood is filtered through filtration gaps between the “legs” of podocytes (3a). Filtered urine passes through the proximal tubule (B) on the right.
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The “legs” of the podocytes cover the capillaries, leaving gaps. Blood is filtered through these slots, known as filter slots. Some proteins are necessary to perform the functions of these “legs”. If babies are born with defects in these proteins (e.g., nephrine or CD2AP), then their kidneys cannot function. Different people have different variants of these proteins, and some variants may predispose to renal failure in the future. Nephrine is a protein that forms filtration gaps. Its structure is similar to lightning, whose teeth are large enough to allow water and sugar to pass through, but are too small to allow proteins to pass through. Defects in nephrin cause congenital renal failure. CD2AP regulates the cytoskeleton of podocytes and stabilizes filtration gaps. [1] [2]
Content
Functions
Neighboring podocytes are closed to cover the basal plate, which is closely connected with the capillaries of the glomeruli, but at the same time leaving room for filtering gaps. These gaps consist of several cellular surface proteins, including nephrine, podocalyxin, and P-cadherin, which allow large molecules, such as albumin and gamma globulin , to be found in the blood, preventing them from entering the filtrate.
Small molecules, such as water, glucose, and soluble salts, can pass through the filter slots and form a filtrate, which is then treated with a nephron to form urine. Podocytes are also involved in the regulation of glomerular filtration. When the podocytes contract, they cause the filter slots to close, which leads to a decrease in glomerular filtration by reducing the surface area used in the filtration.
Structural Features
The structural features of podocytes are determined by the high level of vesicular transport in these cells. Podocytes have a well-developed endoplasmic reticulum and a large Golgi apparatus , which indicates active protein synthesis and a high level of post-translational modifications . In these cells, multivesicular complexes and other lysosomal components are also usually detected, which indicates active intracellular activity. The “legs” of podocytes increase the surface area, which is crucial for filtration efficiency. [3]
Pathology
Violations in the functioning of the filter slots or the destruction of podocytes can lead to an increase in the protein content in the urine. For example, this occurs with a Finnish-type congenital nephrotic syndrome, in which a newborn has an increased protein content in the urine, which leads to renal failure. The cause of this disease is a mutation in the gene encoding nephrine.
See also
- Nephron
- Kidney (anatomy)
Notes
- ↑ Wickelgren, I. CELL BIOLOGY: First Components Found for Key Kidney Filter (Eng.) // Science: journal. - 1999. - Vol. 286 , no. 5438 . - P. 225–226 . - DOI : 10.1126 / science.286.5438.225 . - PMID 10577188 .
- ↑ Löwik MM, Groenen PJ, Levtchenko EN, Monnens LA, van den Heuvel LP Molecular genetic analysis of podocyte genes in focal segmental glomerulosclerosis — a review // Eur. J. Pediatr. : journal. - 2009 .-- November ( vol. 168 , no. 11 ). - P. 1291-1304 . - DOI : 10.1007 / s00431-009-1017-x . - PMID 19562370 .
- ↑ Physiology: 7 / 7ch04 / 7ch04p08 - Essentials of Human Physiology
Links
- Urinary / mammal / vasc1 / vasc1 - Comparative Organology at University of California, Davis - "Mammal, renal vasculature (EM, High)
- Histology image: 22401loa - ". Ultrastructure of the Cell: podocytes and glomerular capillaries »
- Physiology: 7 / 7ch04 / 7ch04p09 - Essentials of Human Physiology
- podocyte.ca (link unavailable) at Samuel Lunenfield Research Institute