I know that the vascular system of the human body is organized in the two, "ever branching", structures of the veins and the arteries. These two structures stem from their connections to the heart and stretch and branch throughout the body.
The two structures are interconnected through capillary beds, responsible for the interactions between the blood and the extracellular liquid, surrounding the tissue cells of the body.
The capillary beds are connected to the arteries and the veins through small vessels, venules, branching out from veins and arterioles, branching out from the arteries.
The capillary beds consist of a web of capillaries, vessels small and thin enough to allow exchange of nutrients and waste between the blood in the vessels and the extracellular liquid surrounding the vessels as well as the cells of the body.
Now, I realize that the capillary beds must be ubiquitous throughout the body, sustaining every part of the body but the circulatory system itself.
I am eager to find out more about the venules and arterioles. Looking at the structure of veins and arteries, how prevalent are the smaller blood vessels? Are the arteries and veins "fuzzy" with arteriole and venules or are the small vessels more sparse? Do they emanate from large vessels as well as smaller ones? How do their presence interfere with vascular interventions or even drawing blood for blood tests?
I'd be happy for information in these matters. Cheers Mats