I have a small curious doubt. How porous are veins and arteries?
In other words, do veins and arteries exchange a lot of chemicals before their arrival to capillary beds, or does the exchange all take place in the capillaries?
the wall of capillaries is unistratified, so the vast majority of exchanges take place here.
Capillaries are semipermeable which means things pass through them, therefore all nutrients and gas exchange takes place in the capillaries, before transfering it to the cells.
and there are also cappilairies that are fenestrated –> increased permeability for example in the kidneys.
Are vein walls more muscular than arteries’?
Do veins have valves on the inside to prevent backflow?
Arteries have more muscle fibres than veins…
Then my question: why arteries are muscular whereas veins are not so? 😉
blood comes to arteries with high pressure, so they are muscular to avoid the pressure affect negatively.
Ozge is right. Arteries are accumulators of pressure, so they need muscle fibers. Veins are accumulators of volume so they need to be able to expand.
By the way, Dr.Stein, was this a test or sth like that? 🙂
This was a little quiz like the one that I regularly give to my students in the end of my class or before my next class to provide their comprehension of things they already got from my previous lecture 😉
What causes veins to form into strong arteries when used for a tripple bypass?
Also, when training the cardiovascular system, would the veins become more muscular over time?