1. Blood Vessels and Circulation
Chapter 21, part 1
Blood Vessels and Circulation

2. Learning Objectives Distinguish among the types of blood vessels.
Describe fluid and dissolved material transport into and out of the cardiovascular system.
Describe the factors that influence blood pressure and blood pressure regulation.
Discuss the mechanisms involved in the movement of fluids between capillaries and interstitial spaces.

3. Learning Objectives
Describe how blood flow and pressure in tissues is regulated.
Identify the principle blood vessels of each circuit and the areas they serve.
Describe fetal circulation patterns and the changes that occur in these patterns at birth and during aging.

4. SECTION 21-1 The Anatomy of Blood Vessels

5. Structure of vessel walls
Walls of arteries and veins contain three distinct layers
Tunic intima
Tunica media
Tunica externa

6. Figure 21.1 A Comparison of a Typical Artery and a Typical Vein

7. Differences between arteries and veins
Compared to veins, arteries
Have thicker walls
Have more smooth muscle and elastic fibers
Are more resilient

8. Arteries Undergo changes in diameter
Vasoconstriction – decreases the size of the lumen
Vasodilation – increases the size of the lumen
Classified as either elastic (conducting) or muscular (distribution)
Small arteries (internal diameter of 30 um or less) are called arterioles

9. Capillaries An endothelial tube inside a basal lamina These vessels
Form networks
Surround muscle fibers
Radiate through connective tissue
Weave throughout active tissues
Capillaries have two basic structures
Continuous
Fenestrated
Flattened fenestrated capillaries = sinusoids

10. Figure 21.2 Histological Structure of Blood Vessels

11. Figure 21.4 Capillary Structure

12. Capillary Beds An interconnected network of vessels consisting of
Collateral arteries feeding an arteriole
Metarterioles
Arteriovenous anastomoses
Capillaries
Venules

13. Figure 21.5 The Organization of a Capillary Bed
Figure 21.5a, b

14. Veins
Collect blood from all tissues and organs and return it to the heart
Are classified according to size
Venules
Medium-sized veins
Large veins

15. Venous Valves Venules and medium-sized veins contain valves
Prevent backflow of blood

16. Figure 21.6 The Function of Valves in the Venous System

17. Distribution of blood Total blood volume is unevenly distributed
Venoconstriction maintains blood volume
Veins are capacitance vessels
Capacitance = relationship between blood volume and pressure
PLAY
Animation: Anatomy Review: Blood Vessel Structure and Function

18. Figure 21.7 The Distribution of Blood in the Cardiovascular System

19. SECTION 21-2 Cardiovascular Physiology

20. Circulatory Pressure
Circulatory pressure is divided into three components
Blood pressure (BP)
Capillary hydrostatic pressure (CHP)
Venous pressure

21. Figure 21.8 An Overview of Cardiovascular Physiology

22. Resistance (R)
Resistance of the cardiovascular system opposes the movement of blood
For blood to flow, the pressure gradient must overcome total peripheral resistance
Peripheral resistance (PR) is the resistance of the arterial system

23. Overview of Cardiovascular Pressures
Factors involved in cardiovascular pressures include
Vessel diameter
Cross-sectional area of vessels
Blood pressure
Blood viscosity

24. Figure Relationships among Vessel Diameter, Cross-sectional Area, Blood Pressure, and Blood Viscosity
Figure 21.9