1. Blood Vessels & Circulation
Chapter 13

2. Types of Blood Vessels Arteries Capillaries Veins
Blood vessels that carry blood away from the heart
Capillaries
microscopic blood vessels that allow exchanges between blood and tissue
Veins
Blood vessels that carry blood to the heart

4. General Features of Blood Vessels
Veins and arteries consist of three layers
Tunica intima: innermost layer
Tunica media: middle layer
Tunica adventia: outermost layer

5. Arteries THREE TYPES OF ARTERIES Elastic arteries Largest in diameter
Thickest walls
Mostly elastic tissue
Stretch when ventricles pump into them
Prevents blood pressure from falling rapidly
Maintains blood flow when ventricles are relaxed

6. Arteries Muscular arteries Medium and smaller diameter
Made up of a lot of smooth muscle
Control blood flow to different regions of body
Vasoconstriction:
Caused by contraction of smooth muscle in blood vessels
Decreases blood vessel diameter and blood flow
Vasodilation:
Relaxation of smooth muscle in blood vessels
Increases blood vessel diameter and blood flow

8. Arteries Small arteries Arterioles Smaller diameter Smaller walls
Smallest arteries
Transport blood from small arteries to capillaries

9. Capillaries Structure Function
Single layer of simple squamous epithelium
Diameter approximately the same as that of a red blood cell (7.5 micrometers)
Function
Receive blood from arterioles
Branches out to form networks
Regulated by precapillary sphincters
Give up oxygen and nutrients to body tissues
Take up carbon dioxide and other waste products from body tissues.

10. Single Erythrocyte squeezing through capillary

11. Capillaries
Video Clip

12. Capillaries

13. Veins Venules Small Veins Medium Sized Veins
Receive deoxygenated blood from capillaries
Diameter a little larger than capillaries
Small Veins
Receive blood from venules
Medium Sized Veins
Collect blood from small veins and deliver it to large veins

15. Veins
Valves
Found in veins that are larger than 2 millimeters in diameter.
Allow blood to flow to the heart, but not backward
Composed of two cusps, or flaps
Similar in function to the semi-lunar valves
Valve animation

18. Types of Blood Vessels Video Clip

19. Blood Pressure
Blood Pressure= measure of force blood exerts against the blood vessel walls.
Systolic: Top number. Pressure in the arteries when the ventricles contract.
Diastolic: Bottom number. Pressure in the arteries between beats when ventricles are resting.

20. Blood Pressure

21. Blood Pressure Blood pressure values
Normal adult value is about 120 Hg systolic and 80 Hg diastolic or 120/80.