Lecture 19: Vascular Histology

Question 1

What are the three layers of blood vessels?

Answer 1

Tunica Intima (innermost)
Tunica Media (middle)
Tunica Adventitia (outermost)

Question 2

What is the tunica intima composed of?

Answer 2

1) Endothelium: reduces friction
2) Basal lamina
3) Subendothelial Layer

Question 3

The endothelium of the tunica intima is composed of what type of cells?

Answer 3

Squamous epithelial cells (single layer)

Question 4

The tunica media in the arteries is relatively ____.

The tunica media in the veins is relatively ____.

Answer 4

Arteries: thick
Veins: thin

Question 5

Why does the tunica media have small openings?

Answer 5

Openings are for nutrients to diffuse

Question 6

How is the tunica media arranged?

Answer 6

Circular pattern of arranged smooth muscle layers

Question 7

What separates the tunica media from the tunica adventitia?

Answer 7

Layer of elastin

Question 8

How is the tunica adventitia arranged?

Answer 8

Longitudinally (up/down) arranged

Question 9

The tunica adventitia in the arteries is relatively ____.

The tunica adventitia in the veins is relatively ____.

Answer 9

Arteries: thin
Veins: thick

Question 10

What is the vasa vasorum?

Answer 10

Vessels of tunica adventitia that supply blood to the tunics of the vessels (allows diffusion of nutrients)

Question 11

What is the nervi vasorum?

Answer 11

Nerves of vessels that allow ANS input that can control the contraction

Question 12

Describe the hallmarks of the large (elastic) arteries.

Answer 12

• Elastin found in concentric sheets b/t tunica layers
• No fibroblasts
• Very thick tunica media

Question 13

Describe the hallmarks of the medium (muscular) arteries.

Answer 13

• Less elastin
• Internal and external elastic membranes are more prominent
• Smooth muscle in spiral fashion
• Tunica media and tunica adventitia about same thickness

Question 14

Describe the hallmarks of the small arteries.

Answer 14

• Internal elastic membrane present

- Up to 8 layers of tunica media

Question 15

Describe the hallmarks of the arterioles.

Answer 15

• Internal elastic membrane may/may not be present

- Up to 1-2 layers of tunica media

Question 16

In arterioles, what will sympathetic innervation to the tunica media cause?

Answer 16

Vasoconstriction

Question 17

In arterioles, what will parasympathetic innervation to the tunica media cause?

Answer 17

Vasodilation

Question 18

What are pericytes?

Answer 18

Contractile cells that wrap around the endothelial cells that line the capillaries and venules throughout the body

Question 19

What are the function of pericytes?

Answer 19

Promote stability of capillaries and postcapillary venules

Question 20

What controls pericytes?

Answer 20

Nitric Oxide

Question 21

What connects endothelial cells found in the innermost layer of tunica intima?

Answer 21

Cell-cell junction

Question 22

What is the function of endothelial cells?

Answer 22

• Supports basement membrane
• Produces collagen
• Metabolically involved in blood coagulation and thrombosis, and local vasodilation/constriction

Question 23

Describe continuous capillaries.

Answer 23

• Most common
• Tight junctions don’t allow many molecules to enter
• Pericytes present
• Continuous basement membrane

Question 24

Describe fenestrated capillaries.

Answer 24

• Located in organs where blood exchange is most important
• Larger items can go through
• small windows in capillaries
• Continuous basement membrane

Question 25

Describe sinusoidal capillaries.

Answer 25

- Open exchange for large molecules and cells | - Discontinuous basement membrane

Question 26

What are metarterioles?

Answer 26

First branch off of arteriole supplying tissues

Question 27

What are precapillary sphincters?

Answer 27

Regulate blood flow to capillaries | -can open/close

Question 28

What are true capillaries?

Answer 28

Between arterioles and venules | -where proper gas exchange occurs

Question 29

What is a thoroughfare channel?

Answer 29

Distal end of metarteriole

Question 30

What does a thoroughfare channel connect to?

Answer 30

Postcapillary venule

Question 31

Describe the hallmarks of veins.

Answer 31

- Tunica not well defined - Thinner walls - Larger lumen (often collapsed)

Question 32

What does the tunica intima contain that arteries don't have?

Answer 32

Have valves

Question 33

In what direction do lymph in lymphatic vessels flow?

Answer 33

Unidirectional

Question 34

In lymphatic capillaries, what are the openings between the endothelial cells called?

Answer 34

Anchoring filaments

Question 35

Describe the flow of lymph.

Answer 35

- Lymphatic capillaries --> vessels --> trunks - Either right lymphatic duct or thoracic duct - Brachiocephalic vein