Blood Vessels Cheat Sheet

Blood vessels Blood vessel structure ● Tunics = layers of the blood vessel 1. Tunica Intima (innermost) ● Derived from endothelium ● Squamous, epithelial cells ● Continuous with the chambers of the heart (blood being removed and brought back to the heart is continuous) ● Subendothelium has some connective tissue with elastic fibres for stretching and recoiling in vasoconstriction and vasodilation (not always epithelium, but predominantly epithelium) 2. Tunica media ● Derived from mesoderm → smooth muscle ● Involuntary control ● Vasomotor nerves enables vasodilation and vasodilation (changes the space of the lumen to fill or reduce the amount of blood) ● Vasa vasora → direct blood supply to the muscle layer, to provide nutrients and to survive 3. Tunica externa (outermost) ● Connective tissue sheath that wraps around the blood vessel ● Composed of dense irregular connective tissue ○ Can move along with the changing dilation ○ Anchor blood vessel to target organ/tissue Types of blood vessels ● There are three types of blood vessels: arteries, veins and capillaries ● Capillaries = connection between the smallest arteries and veins ○ Where the last of the oxygenated blood with nutrients reaches the tissue, collects what it needs and releases waste into the space around the capillaries. The blood can then go into the veins to be distributed back to the heart. ● Veins and arteries normally come in matching pairs Differences between veins and arteries Arteries (A for Away) Function - Distinguishing features - Veins Carries blood away from the heart to supply target organ Decrease in size as you go away from the heart (branches) - Carries blood back to the heart (venous return/drainage) Tributaries (vein that empties into another vein) increase in size towards the heart Thicker tunica media - Thicker tunica externa between arteries and veins - - Narrow lumen More elastic and collagen fibres → can maintain shape regardless of there is blood or no blood flowing through them, can resist changing blood pressures Very thick walls Arterial blood squirts and has a pulsating flow Larger lumen → greater capacity to hold more blood Less elastic and collagen fibres → tubes collapse when there’s no blood in them Valves Very thin walls More numerous than arteries Venous blood is silent and has a steady, slow flow - - Types of arteries and veins Elastic arteries Muscular arteries Arterioles Venules Veins ♡ START HERE → → →→→→→→→→ → → → → → → CAPIL LARY → → → → → → → → → END HERE ♡ - Largest artery A lot of elastin Transports blood under high pressure to organs - Medium sized artery Thick tunica media to keep pumping blood to target organ - Smallest artery Thin walls with all 3 tunics Controls blood flow Enters the - Smallest vein Small venules = tunica intima Larger venules= all 3 tunics - Largest vein Have valves, which help it to move up in increments, it goes up and the - Needs to vasoconstrict to transport blood around the body in a short amount of time - Controls blood flow and regulates organs capillary bed where it transitions into the smaller veins - Drain the capillary beds - Major arteries ● Arteries are one blood vessel through the entire body but it has branches to get to different places - endothelial layers are continuous ● Name change when the blood vessel goes to a different part of the body valve shuts (can't go back down) Returns blood back to the heart