Blood vessels

Question 1

What is the tunica intima?

Answer 1

• inner layer of a blood vessel (thin, squamous cells - for diffusion)
• contains a layer of endothelial cells in intimate contact with the blood and a layer of elastic and loose collagenous tissue containing intimal cells

Question 2

What is the tunica media?

Answer 2

• middle layer of a blood vessel

Question 3

What is the tunica adventitia?

Answer 3

• outer supporting layer of blood vessels

- comprised of collagenous tissue

Question 4

What are vasa vasorum?

Answer 4

• blood vessels in the adventitia that supply oxygen and nutrients to the adventitia and outer part of the media

Question 5

What is characteristic of the largest arteries’ media?

Answer 5

a thick media with multiple elastic layers

Question 6

Why are the elastic layers crucial in arteries?

Answer 6

elastic layers are crucial to permit expansion of the vessels after systolic contraction of the heart, dampening the systolic blood pressure

Question 7

What is characteristic of the intima in the aorta and larger arteries (elastic arteries) branching from it?

Answer 7

• thin layer of endothelial cells
• underlying layer of collagen/elastin-rich fibers
• contains fibroblasts
• myointimal cells that have similar structural features to smooth muscle cells

Question 8

What is characteristic of the media in the aorta and larger arteries (elastic arteries) branching from it?

Answer 8

• multiple elastic layers

- some collagenous fibers and smooth muscle cells sandwiched in between

Question 9

What is characteristic of the adventitia in the aorta and larger arteries (elastic arteries) branching from it?

Answer 9

vasa vasorum (vessels within the vessel)

Question 10

What do the multiple elastic layers in elastic arteries become restricted to in muscular arteries?

Answer 10

inner elastic lamina (between the intima and the media) and the outer elastic lamina (between the media and adventitia)

Question 11

Describe the intima, media, and adventitia in muscular arteries.

Answer 11

intima - thin and contains endothelial cells and a relatively thin layer of connective tissue
media - primarily smooth muscle cells
adventitia -thick and contains collagen and elastin

Question 12

Do smaller muscular arteries have both outer and inner elastic lamina?

Answer 12

no, just inner

Question 13

What is the structure of arterioles?

Answer 13

• inner lining of endothelial cells on a thin basement membrane
• 1-2 layers of smooth muscle cells
• outer collagenous tissue (blends with surrounding connecting tissue)

Question 14

Describe the structure of capillaries.

Answer 14

• smallest vessels
• 1-2 endothelial cells surrounding the lumen
• no muscular layer
• often surrounded by pericytes (can give rise to smooth muscle cells during vessel growth and wound healing and may be contractile)

Question 15

Describe the structure of continuous capillaries.

Answer 15

• endothelial cells form an uninterrupted lining

- transfer across the lining can occur via pinocytotic vesicles

Question 16

Describe the structure of fenestrated capillaries.

Answer 16

• have pores or fenestrations in the endothelial cells

- some are covered by a thin diaphragm

Question 17

What are post-capillary venues?

Answer 17

• capillaries empty into these vessels (have larger diameter but structurally similar)
• have surrounding pericytes (can give rise to smooth muscle cells during vessel growth and wound healing and may be contractile)
• slow blood flow and leukocytes tend to diapedese through vessel walls at these sites
• responsive to vasoregulatory substances such as histamine

Question 18

What are pericytes?

Answer 18

can give rise to smooth muscle cells during vessel growth and wound healing and may be contractile

Question 19

Do small veins have an inner elastic lamina?

Answer 19

no

Question 20

What is the structure of medium sized veins?

Answer 20

• intimal layer of endothelial cells
• smooth muscle of 2-4 layers
• increasing thickening of the tunica adventitia (thickest layer)

Question 21

What is the structure of large veins?

Answer 21

• thin intima of endothelial cells
• media of interlayer smooth muscle and collagen fibers with very small amounts of elastin fibers
• tunica adventitia is thick and contains vasa vasorum

Question 22

What is the structure of lymphatics?

Answer 22

• single, very thin endothelial layer