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
oxide and the vasoconstrictor endothelin. Venous tunica intima -
