Lesson 6B.docx - Question 1 Needs Grading Describe the structure of the three layers of the walls of arteries[1 tunica externa 2 tunica media 3 tunica

Lesson 6B.docx - Question 1 Needs Grading Describe the...

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Question 1 Needs Grading Describe the structure of the three layers of the walls of arteries [1) tunica externa; 2) tunica media; 3) tunica intima] and state how the structure contributes to the functioning of the vessel. Describe the structural differences in these layers in veins, and explain the reason for each difference. Selected Answer: 1. Arterial tunica externa is the outermost layer is is made of fibrous connective tissue. Tunica externa is strong to prevent rupture of the vessel from pressure of blood inside. Venous tunica externa is the outermost layer of the vein made of thinner fibrous connective tissue, because veins do not carry blood under high pressure. 2) Arterial tunica media is the middle layer and is made of smooth muscle and elastic connective tissue, involved in the maintenance of normal blood pressure. Relaxion of the smooth muscle brings about dilation of the vessel and a lower pressure. Contraction of the muscle layer brings about constriction and a higher blood pressure. Smooth muscle also also has a nerve supply, increased sympathetic nerve impulses bring bout vasconstriction, and a decrease in impulses contributes to vasodilation. Venous tunica media is the middle layer made of thin smooth muscle, because veins because veins do not regulate the maintenance of blood pressure and blood flow. 3) Arterial tunica intima is the inner most layer made of simple squamous epithelial tissue , it is very smooth to prevent adhesion of platelets and abnormal blood clotting. Aterial tunica intima also secretes the vasodilator nitric oxide and the vasoconstrictor endothelin. Venous tunica intima is smooth endothelium folded into valves to prevent the backflow of blood as it returns to the heart. Correct Answer: 1) Arterial tunica externa - fibrous connective tissue - strong to prevent rupture of the vessel from pressure of blood inside. Venous tunica externa - thin fibrous connective tissue, because veins do not carry blood under high pressure 2) Arterial tunica media - smooth muscle and elastic connective tissue - contributes to maintenance of blood pressure - smooth muscle relaxes to bring about dilation of the vessel when blood pressure inside increases (the opening becomes larger) and smooth muscle contracts to bring about constriction of the vessel when blood pressure drops too low (smaller opening through which blood can flow increases pressure) - elastic connective tissue allows for normal stretching when the heart contracts and pumps blood and recoil when the heart relaxes to help keep blood moving in arteries and prevent extreme highs and lows inside the vessel with normal beating of the heart. Venous tunica media - thin smooth muscle, because veins are not as important in the maintenance of BP. 3) Arterial tunica intima - simple squamous epithelial tissue - very smotth to prevent adhesion of platelets and abnormal blood clotting - also secretes the vasodilator nitric
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oxide and the vasoconstrictor endothelin. Venous tunica intima -
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