Your Heart and Vessels

Made up of the heart and the blood vessels. 

Arteries and arterioles

Arteries have more thinker walls than veins to withstand the high pressure from the heart. 

The structure of arteries varies depending on how closer they lord to the heart. 

In larger arteries the tunica media is made up of more elastic tissue allowing them to stretch, to absorb the pressure wave generated by the heart. 

This proportion decreases as the arteries branches into many artery and become smaller. 

The arterioles tunica media are made up

Of smooth muscles this gives them their precise diameter mainly the systemic pressure. 

Anastomoses and end arteries 

Anastomoses: are arteries that form a link between arteries supplying an area, eg the arteries supplying the palm of the hand and sole . If the arteries supplying an area is blocked, the anastomotic artery supplies a collateral blood supply giving the blocked artery time to dilate. 

End artery: are arteries that are the sole source of blood supply To a tissue. Eg the artery supplying the circulus arteriosus, once the artery is block the tissue it supplies dies because there is no alternative blood supply. 

Capillary and sinusoid

The smallest arteries branches into huge numbers of capillaries. The walls of the capillaries are made up of single layer of endothelial cells permeable to water and small molecules. 

The capillaries form a vast network of tiny vessel that link the arterioles to the venules. 

In area like the liver and bone marrow, the diameter of the capillaries are larger forming the sinusoids. And blood flow are slower. 

Venules and veins

Capillaries converge to form a venules where the blood pressure is lower, the venules converge to foRm the veins, the arteries wall are thicker than the venous walls although the both have the 3 structures. The vein have valves that-prevent the back  flow of blood. They return blood back to the heart.