What is fenestrated capillary?

[scilearner]

Hello everyone,

 

In fenestrated capillary there are holes inside the endothelial cell, I don't understand how cells can have holes? Does this mean that individual holes in endothelial cells are covered by a lipid membrane? Can anyone tell how can there be holes in an individual cells when lipid membrane usually covers the whole cell. Thanks

[ewmon]

Try Googling it.

[scilearner]

Try Googling it.

 

Hey I have, and I'm asking how cells can have holes like that, this is the first unhelpful response I have recieved from you.

[ewmon]

I'm sorry, I wasn't trying to be rude. It's just that I googled "fenestrated capillaries" and found

 

Capillaries ... characterized by the presence of circular fenestrae or pores that penetrate the endothelium; these pores may be closed by a very thin diaphragm.

and then for "endothelium"

 

A tissue consisting of a single layer of cells that lines the blood and lymph vessels, heart, and some other cavities.

So, it's the tissue consisting of a single layer of cells that has the pores, not the cells themselves.

 

HOWEVER, Wikipedia does say

 

Fenestrated capillaries have pores in the endothelial cells

but then it says

 

Sinusoidal or discontinuous capillaries are special fenestrated capillaries that have larger openings (30-40 μm in diameter) in the endothelium

So, Wikipedia should say

 

Fenestrated capillaries have pores in the layer of endothelial cells

[scilearner]

It's ok I understand Thanks for the response. However I'm still bit confused.

 

 

In this diagram I think discontinuous capillaries is what you mentioned, doesn't fenestrated capillary have holes inside the cell.

[ewmon]

Hmm.... I studied down to the tunica intima as a tissue, but not its parts. But I did find this:

 

Diffusion through capillary walls is the means by which most substances are transferred between the bloodstream and the interstitial fluid (the fluid between cells in body tissues). Capillaries are thin-walled tubes composed of a single layer of highly permeable endothelial cells lying on a thin basement membrane. Lipid soluble molecules such as ethanol, nicotine & diazepam as well as gases like oxygen & carbon dioxide diffuse directly across the capillary membranes. Gaps between adjacent endothelial cells (intercellular clefts) allow for diffusion of water-soluble substances, as do channels through the endothelial cell walls (fenestrae, "little windows"). Plasmalemma vesicles allow for pinocytosis (vesicle transport) of substances across the membrane. Intercellular clefts in the liver are so wide that plasma proteins can pass directly from the blood into liver tissue. Fenestrae are so large in kidneys that substances can be filtered in the glomeruli without having to pass through intercellular clefts.

Cryogenics protocol

 

Intercellular clefts and fenestrae differ. Pinocytosis is the transfer through the cells, as you said. The fenestrae seem like specialized areas of the cell wall where vesicles form, which are then transported to the other side of the cell, seemingly to another fenestra. Or, just maybe, because that quote says "channels", that fenestrae are channels through these cells.

 

 

I'm confused too, so I'm going to shut my mouth, but I'll keep listening because this is an interesting subject, Thanks.

[scilearner]

Thought this could not get any worse, but it can

 

 

Now I realized each capillary is covered by a basal lamina, now how do the molecules pass through this after they pass through the pores?