1. Exercise 21: Anatomy of Blood Vessels

2. 3 Tunics (t. intima, t. media, t. externa)1
Very thick tunica media in arteries 2 3
Only tunica intima in capillaries
Figure 11.9b

3. Blood Vessel Tunic
Description
Tunica intima
Most internal tunic;
Its smooth surface decreases friction
Tunica media
Bulky middle tunic contains smooth muscle and elastin;
Tunica externa (adventitia)
Most superficial tunic

4. *Also called
“Tunica adventia”
Tunic/
Vessel
Tunica Intima
Tunica media
Tunica externa*
Artery X
Vein
Capillary
Only tunica intima in capillaries

5. Capillaries
Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue
Only capillaries directly serve the needs
of the body’s cells. It is through the capillary
Walls that exchanges are made between tissue cells and blood.
Respiratory gases, nutrients, and wastes move along diffusion gradients.

6. Artery Veins
VALVE

7. Blood Vessels: The Vascular System
Figure 11.9a

8. Elastic recoil of artery propels blood along
They have the greatest amount of elastin, enabling them to expand. When the heart relaxes, the recoil propels blood onward.

9. Muscular Pumps aids blood flow in Veins
As skeletal muscles surrounding the veins contract and relax, blood is milked through the veins toward the heart.

10. Respiratory Pump aids blood flow in veins!
Pressure changes that occur in the thorax during breathing also aid blood return to the heart through the veins.

11. Arteries are thicker than veins
Because arteries are closer to the pumping action of the heart, they must be able to expand as blood is propelled into them and then recoil passively as the blood flows off into the circulation during diastole. Arterial walls must be strong and resilient to withstand blood pressure fluctuations.