3-I Review of Vessel Histology

Question 1

Describe the layers in the wall of generic blood vessel

Answer 1

three tunics:i) Intima : endothelium and thin layer of loose connective tissue, sometime accompanied by a n internal elastic membrane, ii) media : smooth muscle, secreting elastic lamiae are made of overlapping sheets of elastin with fenestrations, iii) adventitia: outer layer of loose connective tissue, includes vasa vasorum and autonomic innervation to the adventitia

Question 2

Describe the unique features of arteries and arterioles and the structural and functional distinctions between elastic and muscular arteries

Answer 2

Arteries have substantial internal elastic membrane, the tunica media being the thickest tunica:i) Elastic arteries are closest to the heart to produce continuous flow into the systemic circulation, ii) Muscular arteries have a much greater ability to control their lumen diameter and blood flow rates. b) Arteries have 5+ layers of smooth muscle, Arterioles may not have an internal elastic lamina and contain precapillary sphincters to control flow into the capillaries

Question 3

Explain the role of arteries in hypertension.

Answer 3

Arteriolar vasoconstriction contributes significantly to essential hypertension regulated by sympathetic as well as vasoactive messengers

Question 4

Explain how atherosclerosis progresses

Answer 4

Endothelial injury can lead to thickening of the tunica intima and gradual obstruction of the vessel as LDL and monocytes enter the tunica intima, and eventually movement of smooth muscle cells, b) Can causes an obstruction, embolis or aneruysm

Question 5

Distinguish the unique structures and functions of the three types of blood capillaries

Answer 5

Capillaries consist of only a tunica intima made of endothelium and basement membrane: i) Continuous capillaries: cells joined by tight junctions, tightly regulated, ii) Fenestrated capillaries: cells linked by tight junctions, their endothelial cells have perforations called fenestrae containing a diaphragm, exist where rapid exchange occurs, iii) Discontinuous: frequently lack junctional complexes and basement membranes, large enough for cells to exit ; these are often called sinusoids (generally large diameter and highly anastomotic)

Question 6

Describe the unique structure and function of the lymphatic capillaries

Answer 6

return lymph to blood, contain valves to prevent back flow

Question 7

Describe the 5 mechanisms of transporta across capillary endothelium.

Answer 7

Diffusion, vescicular transport, fenestrae, paracellular pathway and endothelial discontinuties

Question 8

Describe the unique features of venules and veins and how blood flow is controlled through veins

Answer 8

Venules: during an immune reaction, mast cells secrete histamine which causes the tight junctions of venules and capillaries to become more permeable; are mostly endothelium surrounded by a little bit of connective tissue; Veins composed of endothelium and basement membrane, valves and smooth muscle Bonus: Ateriovenous anastomosis convey blood directly from arterial system to the venous system by bypassing the capillary bed- can be used to regulate temperature

Question 9

Define angiogenesis and describe its steps

Answer 9

Angiogenesis: development of new blood vessel from an existing vessel: Endothelial cells enzymatically dissolve the basal laminal in a small area, Cells migrate, secreting basal lamina as they migrate, Migration and alignment of endothelial cells for a solid sprout, Endothelial cell proliferation and hollowing of the sprout, Sprout fuses with another vessel