- Filtration slits are formed by
(1) podocytes
(2) endothelial cells of capillary
(3) mesangial cells
(4) Lacis cells
Filtration slits are crucial microscopic structures in the kidney’s filtration barrier, playing a pivotal role in the formation of urine by allowing selective passage of fluids and small solutes while retaining larger proteins and cells within the bloodstream.
What Are Filtration Slits?
-
Filtration slits are tiny gaps between podocyte foot processes (also called pedicels) that wrap around the glomerular capillaries.
-
These slits form part of a multilayered filtration barrier within the renal corpuscle, which also includes the capillary endothelium and the fused basement membrane.
How Are Filtration Slits Formed?
-
Podocytes, specialized epithelial cells in the inner layer of Bowman’s capsule, have numerous primary processes branching into secondary foot processes.
-
The foot processes from adjacent podocytes intertwine but do not tightly fuse, leaving narrow filtration slits about 25-40 nm wide.
-
These slits are spanned by a slit diaphragm, a thin proteinaceous structure acting as a selective sieve.
Role and Importance
-
Filtration slits allow the passage of water, ions, glucose, and small molecules into the filtrate.
-
They prevent larger molecules such as plasma proteins (albumin) and blood cells from passing, maintaining blood composition.
-
The slit diaphragm proteins, including nephrin, podocin, and others, maintain the integrity and selective permeability of the filtration slits.
Other Cellular Structures in Filtration
-
Endothelial cells of glomerular capillaries are fenestrated, allowing passage of materials but without forming slits.
-
Mesangial cells provide structural support and phagocytic functions but do not form filtration slits.
-
Lacis cells (extraglomerular mesangial cells) regulate glomerular filtration but are not involved in slit formation.
Summary Table
Structure Role in Filtration Filtration Slits Formation? Podocytes Foot processes form filtration slits Yes Endothelial cells of capillaries Fenestrated for filtration No Mesangial cells Support and phagocytosis No Lacis cells Regulation No Conclusion
The filtration slits crucial for selective blood filtration in the kidneys are specifically formed by podocytes. Their foot processes interdigitate, creating narrow slits spanned by slit diaphragms that act as filters preventing protein and cell loss while allowing essential substances to pass.
Correct Answer: (1) Podocytes
-
