Molecules below what molecular mass can pass between the pedicels of podocytes during ultrafiltration?

The molecular mass cut-off for molecules to pass between the pedicels of podocytes during ultrafiltration is approximately 30,000 Daltons. This means that molecules smaller than this size, such as water, glucose, and ions, can pass through, while larger molecules like proteins and blood cells are generally retained.

Here are the steps to understand this:

1. Ultrafiltration is a process that occurs in the kidneys to filter out waste products from the blood. This process takes place in the glomerulus, a network of tiny blood vessels in the kidneys.

2. The glomerulus is surrounded by a structure called the Bowman's capsule, which contains specialized cells called podocytes. These podocytes have foot-like extensions called pedicels that wrap around the capillaries of the glomerulus.

3. The gaps between these pedicels form a filtration barrier, allowing certain substances to pass through while retaining others. This is known as selective permeability.

4. The size of the gaps between the pedicels determines what can pass through. Molecules smaller than 30,000 Daltons can pass through these gaps. This includes substances like water, glucose, and ions.

5. Larger molecules, such as proteins and blood cells, are generally too large to pass through these gaps and are therefore retained in the blood. This helps to prevent the loss of important substances from the body.