Blood vessels

What are the three layers of blood vessel walls?

Tunica intima, tunica media, and tunica externa.

What is the tunica intima composed of?

The inner layer with endothelial lining and variable elastic fibers, including a thick internal elastic membrane in arteries.

function of tunica intima

provides frictionless pathway for blood

What is the main function of the tunica media?

To allow control of the internal diameter through smooth muscle sheets and connective tissue.

composition of tunica externa

• connective tissue

• merges with surrounding connective tissue

What is the structure and function of elastic arteries?

• high density of elastic fibers in the tunica media

• allowing them to expand during ventricular systole

• contract during diastole for continuous blood flow.

What distinguishes muscular arteries from elastic arteries?

Muscular arteries have a thicker tunica media and contain more smooth muscle cells.

function of muscular arteries

• distribute blood to organ and muscles

• capable of vasodilation and vasoconstriction to control blood flow

What are arterioles and their characteristics?

Small resistance vessels with poorly defined tunica externa.

What is arteriosclerosis?

The thickening and hardening of arterial walls.

What is atherosclerosis?

The deposition of lipids in the tunica media damaging the endothelial lining.

function of capillaries

connect arterioles to venules

gaseous exchange

permits 2 way exchange from interstitial space and out

What are continuous capillaries known for?

Having a complete endothelial lining with restricted permeability, found in most tissues.

What allows fenestrated capillaries to facilitate exchange?

Pores that penetrate the endothelial lining allowing rapid exchange between interstitial fluid and blood.

What are sinusoids?

Specialized capillaries with discontinuous endothelium and a thinner or absent basement membrane, found in organs like the spleen.

What regulates blood flow in capillary beds?

Precapillary sphincters and the lymphatic system.

marterioles

• supplies whole capillary bed

• each continues as a channel which directly lead to a vein

• constriction can reduce flow to whole bed

arteriovenous anastomoses

• direct communication between arteriole and venule

• bypasses the capillaries

What are venules?

Small veins that direct blood from capillary beds to larger veins.

What are the characteristics of large veins?

They include structures like the superior and inferior venae cavae and have venous valves.

What is the significance of angiogenesis?

It is the formation of new blood vessels, crucial in cardiac muscle, driven by vascular endothelial growth factor (VEGF).