Prac 4 Blood vessels and nerves Flashcards
3 major types of blood vessel
Arteries (Thick wall)
Capillaries (Thin wall)
Veins (Thicker wall)
two major circulatory systems in the body
1 the longer systemic circulation through which blood is transported from the heart to all the tissues of the body
2 shorter pulmonary circulation between the heart to the lungs for the re-oxygenation of the blood.
Describe structure and function of lymphatic vessels
lood plasma which leaves the circulation at the capillaries to bathe the adjoining tissues is returned to the general circulation by a series of vein-like lymphatics. These vessels are generally devoid of blood cells, apart from some of those of the immune system
Difference in appearance between artery and vein
The artery normally has a thicker, more muscular wall and appears circular in outline while the accompanying vein is often larger in diameter, has a thinner, less muscular wall and often has an irregular profile.
what does the The innermost intimal layer consist of
It consists of an endothelium with a small amount of connective tissue beneath. It is separated from the medial layer by a wavy internal elastic lamina (it glistens), a tube-like sheet of elastic tissue
3 layers of arteries and veins
an innermost intimal layer, a medial layer and an outermost adventitial layer.
In muscular arteries what is the medial layer composed of
the media layer is composed mainly of smooth muscle arranged circumferentially. When this muscle contracts it reduces the diameter of the vessel.
VASA VASORUM
Vessels of vessels – Blood vessels near heart are so big they have blood vessels of their own
What classifies as an arteriole?
. As a guideline, arterial vessels with three or less layers of smooth muscle in the medial layer (or which are 100 um or less in diameter) are generally regarded as arterioles
also These vessels normally lack an external elastic lamina and often the internal elastic lamina is poorly developed.
What happens as a result of retrials being small in diameter
They can be closed down completely as a result of the contraction of the smooth muscle in their walls. As a consequence blood is temporarily shunted down a different route.
Describe venues compared to arterioles
Venules are thinner walled and have very little or no muscle. Their walls often consist of an endothelium reinforced only by connective tissues.
Characteristics of lymphatics `
They have an irregular outline and thin walls composed of a mixture of collagen and elastic fibres with a few smooth muscle cells. Like many veins, they contain valves
Typically they are filled with an amorphous colloid (plasma) that stains pink with the H&E stain.
What are lymphatic valves made of
Covered by the endothelium that lines all blood vessels and lymphatics. Inside are some strands of collagen
How do continuous capillaries work
In continuous (closed) capillaries substances are transported across the capillary wall by diffusion or by pinocytosis
How do fenestrated capillaries work
Fenestrated capillaries have pores in them and products can pass fairly freely through the pores (fenestrae - windows).
