Ch 19 Blood Vessels

Ch 19 Blood Vessels - Ch 19: The Cardiovascular System:...

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Ch 19: The Cardiovascular System: Blood Vessels Blood vessels comprise the 3 rd component of the Cardiovascular system: blood is the transport vehicle, the heart provides the motor that moves the vehicle and blood vessels are the routes over which blood must travel to deliver goods and pick up wastes. Anatomically, blood vessels connect the heart with the rest of the body and allow blood to move, like the postman, on its assigned rounds. There are three categories of blood vessels: ARTERIES----->move blood away from the heart VEINS----->move blood back to the heart CAPILLARIES----->connect arteries to veins Anatomy of Blood Vessels The basic structure of the wall of a blood vessels consists of 3 layers: Tunica externa/adventitia = fibrous connective tissue Tunica interna/intima = simple squamous epithelium facing blood ----->endothelium plus underlying connective tissue (+/-elastici fibers) Arterioles lack a tunica externa Venules lack a tunica media Capillaries consist of ONLY a tunica interna/intima----->a naked endothelium. There are differences in the structure of these layers that are reflective of the different challenges presented to arteries and veins in fulfilling their role in circulation: In general ----->arterial walls are thicker ----->arterial walls are more muscular (autonomic tone acts here) ----->arterial walls are more elastic ----->allows for vasoconstriction and vasodilation NB: Except under extreme stimulation, veins do not dilate or constrict Arteries & Veins are sub-categorized based on their histological structure. These sub-categories are named based on either structural/functional characteristics, relative diameter: ARTERIES VEINS Elastic arteries Large veins Muscular/distributing arteries Medium-sized veins Arterioles Venules (Capillaries) There are 2 types of capillaries, characterized by how “leaky” they are. ----->fenestrated (“windowed” in Latin) have gaps between endothelial cells = Pores ----->continuous lack gaps = a continuous (=uninterrupted) endothelium
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: Arteries: ELASTIC arteries ---->examples = aorta, pulmonary trunk, common carotid, subclavian Structure: Tunica media is thickest layer----->LOTS of elastic fibers Internal elastic layer of tunica interna prominent Lgest diameter arteries (aorta~1” in diameter) Function: Receive blood under relatively high pressure ----->must be able to expand during ventricular systole and recoil during ventricular diastole to maintian BP MUSCULAR(structure)/DISTRIBUTING(function) arteries ----->examples = external carotids, brachial, femoral Structure: Tunica media thickest layer due to LOTS of smooth muscle ----->fewer elastic fibers = not very resilient Medium-sized arteries: diameters ~ 0.15” Function: Distribution of blood to tissues ARTERIOLES Structure: lack tunica externa----->endothelium wrapped in smooth muscle
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This note was uploaded on 07/23/2009 for the course BIOL 1141 taught by Professor Loripaul during the Summer '09 term at UMSL.

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Ch 19 Blood Vessels - Ch 19: The Cardiovascular System:...

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