Type your responses to the following questions. Question 2/2 Filtration membrane is formed by three components of the glomerulus: small pores in the capillary endothelium called fenestrae a double basement membrane between the endothelium and the podocytes; and narrow spaces called filtration slits between pedicles.
The Correct Answer and Explanation is:
The filtration membrane in the glomerulus is a specialized structure that allows for the filtration of blood while retaining larger molecules and cells. It is composed of three key components: fenestrae in the capillary endothelium, a double basement membrane, and filtration slits between the podocyte pedicles. Together, these elements create a barrier that regulates which substances pass into the filtrate and which are retained in the blood.
- Fenestrae (small pores in the capillary endothelium): The capillaries in the glomerulus are lined with endothelial cells that contain small pores, known as fenestrae. These fenestrae allow for the passage of water, ions, and small solutes while preventing larger molecules like blood cells and most proteins from passing through. These pores are large enough to permit the passage of certain molecules, but small enough to block others, contributing to selective permeability.
- Double Basement Membrane: Beneath the endothelial cells is a double-layered basement membrane, which acts as another filtration barrier. It is made up of two layers: an inner layer adjacent to the endothelium and an outer layer closer to the podocytes. This membrane is rich in negatively charged glycoproteins that repel negatively charged proteins (such as albumin), which helps prevent protein loss in the filtrate. The basement membrane also provides structural support to the capillaries.
- Filtration Slits (between podocyte pedicles): Podocytes are specialized epithelial cells that surround the capillaries of the glomerulus. The pedicles (foot-like extensions) of these cells interdigitate, forming narrow filtration slits. These slits are lined with a thin diaphragm that further restricts the passage of larger molecules, including proteins. The filtration slits contribute to the selective filtration process, allowing only small solutes, like glucose and ions, to pass into the Bowman’s capsule.
Together, these components form an intricate filtration barrier that ensures only essential substances pass into the urine, while larger molecules and cells remain in circulation. The selective permeability of the filtration membrane is crucial for maintaining the body’s homeostasis.
