Lecture 20 - Cardiovascular Histology

Question 1

What are the different layers (tunics) of the heart?

L20 S5+9

Answer 1

Endocardium:

• innermost layer of atria and ventricles
• continuous with tunic intima of blood vessels
• subendocardium (contains nerves and Purkinje fibers)

Myocardium:
-cardiac muscle cells

Epicardium:

• external layer
• simple squamous epithelium (mesothelium)
• contians adipose cells, nerves, and coronary vessels

Question 2

What are the different vascular layers (tunics)?

L20 S10-11

Answer 2

Tunica intima:

• endothelium and basal lamina
• endothelial cells produce von WIllebrand’s factor VIII
• subendothelial connective tissue (elastic and muscular arteries)
• internal elastic membrane

Tunica media:

• circular smooth muscle tissue and fibroblasts
• collagen and elastic fibers

Tunica adventita:

• loose areolar tissue
• lacking in arterioles

Question 3

What are the characteristics of elastic arteries?
Where are these arteries found?

L20 S14

Answer 3

• conducting arteries
• stretch during systole and recoil during diastole
• tunica media contains several layers of organized elastic fibers called elastic laminae

Examples:

• aorta
• pulmonary trunk
• large branches of the aorta

Question 4

What are the characteristics of muscular arteries?
Where are these arteries found?

L20 S16

Answer 4

• distributing arteries
• tunica media consists of smooth muscle which responds to autonomic stimulation and hormones

Examples:
-al named arteries except those that are elastic

Question 5

What are the characteristics of arterioles?

L20 S19

Answer 5

• tunica media consists of 1-3 layers of smooth muscle cells

- gives rise to metarterioles which have discontinuous smooth muscle layer

Question 6

What are the 3 different types of capillaries and what are their features?

L20 S23

Answer 6

Continuous:

• cytoplasm of endothelium is continuous with the circumference of the vessel
• gas exchange occurs readily but other substances require transcytosis

Fenestrated:

• endothelium is not continuous and contains fenestrae
• basal lamina is continuous

Discontinuous:
-both endothelium and basal lamina are not continuous

Question 7

What are the characteristics of veins?

L20 S24

Answer 7

• large lumen compared to arteries
• thin walls
• valves may be present
• larger veins have layer of longitudinal smooth muscle in tunica adventita