BSC 2086 1st EditionExam 3 Study Guide1.How are blood vessels organized and classified? What are the three layers of blood vessels? What is the vasa vasorum?a. Classified by size and histological organizationi. Size: 1. Largest blood vessels are connected to the hearta. Pulmonary trunk carries blood into pulmonary circulation from the right ventricleb. Aorta carries blood into systemic circulation from the left ventricle 2. Capillaries are the smallest blood vesselsa. Exchange nutrients, chemicals, gases and waste across walls ii. Types:1. Arteries carry blood away from heart2. Arterioles smallest branches of arteries 3. Capillaries smallest blood vessels which allow for exchange between blood and interstitial fluid4. Venules get blood from the capillaries5. Veins return blood to the heart b. Three layers: i. Tunica intima 1. Inner layer2. Includes:a. Endothelial liningb. Connective tissue layerc. Internal elastic membranei. In the arteries, this layer is found in the outer margin of the tunica intima ii. Tunica media 1. Middle layer2. Concentric sheets of smooth muscle in the connective tissuea. Smooth muscles under autonomic control3. Binds to both inner and outer layers4. External elastic membranea. Separates the tunica media from the tunica externa iii. Tunica externa1. Outer layer2. Attaches vessel to adjacent tissues in the arteriesa. Collagen and elastic fibers3. In veins it contains elastic fibers and smooth muscle cells 4. Vasa vasorum a. “Vessels of vessels”b. Small arteries and veins which are found in the walls of large arteries and veins c. Supply the cells of the tunica media and externa 2.What are the similarities and differences between arteries and veins? How does vasoconstriction and vasodilation affect blood flow?a. Arteries: i. Usually roundii. Thick wall made up mostly of tunica media1. Dominated by smooth muscle cells and elastic fibers iii. Higher blood pressure iv. Collapsed artery has small round lumen (internal space)v. Lining is able to fold and is more elastic 1. Able to absorb pressure waves that come with each heart beat due to their elasticity b. Veins:i. Flattened or collapsed, with a thin wallii. Absent internal and external elastic membrane iii. Large flat lumeniv. Lining of the vein will contract unlike the lining of the arteryv. Have valves c. Similarity: run side by side d. Vasoconstriction: contraction of smooth muscle by the ANS which restricts the flow of blood by making the vessel smaller e. Vasodilation: relaxation of smooth muscle which enlarges the lumen allowing more blood to flow through the vessel f. Affects of vasoconstriction and vasodilationi. Afterload on heart1. Resistance against the flow of blood (stroke volume) out of the heartii. Peripheral blood pressureiii. Capillary blood flow 1. Amount of blood that actually flows into the capillaries 3.What are the differences between elastic arteries, muscular arteries, and arterioles? Whatare these arteries also known as?a. Elastic arteriesi. Large vessels like the pulmonary trunk and the aortaii. Tunica media:1. Few muscle cells 2. A lot of elastic fibersiii. Elasticity is able to even out pulse force1. Stretches when the ventricles contract and pushes blood into vessel2. Recoils back to normal state when ventricles relax3. This recoil allows blood to retain pressure b. Muscular arteries i. Medium sized ii. Tunica media is composed of many smooth muscle cells c. Arterioles i. Small arteriesii. Little or no tunica externaiii. Thin or incomplete tunica media d. Elastic arteries = conducting arteriese. Muscular arteries = distribution arteriesf. Arterioles = small arteries 4.What are the properties of capillaries? What are the different types of capillaries and how do their differences account for their different functions?a. Smallest vessels with thin wallsb. Function to diffuse materials between interstitial fluid and blood i. All exchange functions of the cardiovascular systemc. Structurei. Endothelial tube with a thin basement membrane inside ii. Diameter is similar to that of a red blood celliii. NO tunica media or tunica externa d. Types:i. Continuous capillaries1. Complete endothelial lining 2. Found in all tissues except cartilage and epithelia3. Functions:a. Allow diffusion of water, small solutes and lipid soluble materialsb. Block blood cells and plasma proteins c. Specialized continuous capillaries in the central nervous system have strict permeability i. Responsible for blood brain barrierii. Fenestrated capillaries1. Pores in endothelial lining2. Allow rapid exchange of water and large solutes3. Found in: a. Endocrine organsb. Choroid plexusc. Kidneysd. Intestinal tractiii. Sinusoidal Capillaries 1. Gaps between adjacent endothelial cells 2. Found in:a. Spleenb. Liver make plasma proteins that enter bloodc. Bone marrow d. Endocrine organs 3. Allow free exchange of water and large plasma proteins between blood and interstitial fluid5.How is blood flow regulated in capillaries? What are the roles of precapillary sphincters, thoroughfare channels, and anastomoses? What is vasomotion and why is it important to capillary blood flow?a. Phagocytic cells monitor blood at the sinusoids i. Engulf damaged red blood cells, pathogens and wastes b. Precapillary sphincter – smooth muscle cellsi. Guard the entrance to each capillaryii. Capillary blood flows in pulses due to them opening and closing c. Thoroughfare Channelsi. Direct capillary connections between the arterioles and the venulesii. Controlled by metarterioles smooth muscle segments d. Collaterals: multiple arteries which all contribute to one capillary bed i. Allow circulation to continue if one artery is blocked ii. Arterial anastomosis 1. Union of 2 collateral arteriesiii. Arteriovenous anastomoses 1. Direct connectors of arterioles and venules which bypass the capillary bede. Vasomotion i. Cycle of relaxation and contraction of capillary sphincters ii. Allows the blood flow in the capillary beds to constantly change routes 6.Since blood is under low pressure in the veins, how does blood move back to the heart? Which structures and mechanisms help to move blood back to the heart? (You may haveto also refer to lesson 10 to answer this question)a. Compression of the venous valves helps push blood toward the heart without permitting the backflow of blood.b. Pressures from the systole also push the blood throughout the body, and pressure reserve squeezes out excess blood from
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