Question

Which structure does very little albumin escape from the blood during glomerular filtration?

Answer 1

Answer:

b. Basement membrane

Explanation:

Together, the endothelial cells of the glomerular capillaries and the podocytes that completely surround the capillaries form a permeable barrier called filtration membrane or endothelial capsular membrane. This sandwich arrangement allows filtration of water and small solutes, but prevents filtration. of most plasma proteins, blood cells and platelets. The filtered substances move from the bloodstream through three barriers: a gIomerular endothelial cell, the basal lamina and a filtration slot formed by a podocyte.

1 The endothelial cells of the gIoméruIo are quite permeable because they have large perforations (pores) of 70 to 100 nm (0.07 to 0.1 ml) in diameter. These dimensions allow all solutes of the blood plasma to leave the gIomerular capillaries, but prevents blood cells and platelets from leaking. The mesangial cells, contractile cells that help regulate gIomerular filtration are located in the middle of the gomeromer capillaries and the groove formed between the afferent and efferent arterioles.

2 The basement membrane is a layer of acellular material between the endothelium and podocytes, which consists of fibruses in a gIucoprotein matrix; prevents filtration of large plasma proteins.

3 From each podocito thousands of extensions in the form of feet called pedicels that surround the glomerular capillaries extend. The spaces between the pedicels are called filtration cracks. A thin membrane, the crack membrane, extends through each filtration crack and allows the passage of molecules with a diameter smaller than 6 to 7 nm (0.006 to 0.OO7 mm), including water, glucose, vitamins, amino acids , very small plasma proteins, ammonia, urea and ions. Since the most abundant plasma protein, albumin, has a diameter of 7.1 mm, less than 1% of it crosses the membrane of the crack.