Blood Vessels

Introduction

• Blood vessels are integral parts of the cardiovascular system.
• Major types include veins, arteries, and capillaries.

Types of Blood Vessels

Arteries

• Carry blood away from the heart.
• Blood flows under pressure due to the heart's pumping action.
• Most arteries carry oxygenated blood, except the pulmonary artery (carries deoxygenated blood to the lungs).
• Largest artery is the aorta, connected to the heart and extends into the abdomen.
• Subdivided into smaller arteries and arterioles.

Veins

• Carry blood toward the heart.
• Blood flow aided by skeletal muscle action and valves in larger veins.
• Veins contain about 60% of the body's total blood volume.
• Most veins carry deoxygenated blood, except the pulmonary veins (carry oxygenated blood from lungs to heart).
• Largest veins: superior and inferior vena cava.
• Smallest veins are venules, receiving blood from capillaries.

Capillaries

• Smallest blood vessels, connecting arterioles and venules.
• Form networks called capillary beds.
• Facilitate exchange of substances between blood and surrounding tissues.

Structure of Blood Vessels

• All blood vessels have a lumen for blood flow.
• Walls of arteries and veins have three layers:
  1. Tunica intima: Inner layer, thin, reduces friction.
  2. Tunica media: Middle layer, thicker in arteries, contains smooth muscle for vessel diameter control.
  3. Tunica externa: Outer layer, thickest in veins, provides protection and strength.
• Capillary walls consist of a single layer of epithelial cells.

Blood Pressure

• Blood in arteries is under pressure from heartbeats.
• Highest during heart contraction (systolic) and lowest during relaxation (diastolic).
• Normal blood pressure: <120/80 mm Hg.
• Pressure decreases from arteries to capillaries to veins.

Vasoconstriction and Vasodilation

• Arterial walls can contract (vasoconstriction) or relax (vasodilation).
• Helps regulate blood pressure and body temperature.
• Controlled by autonomic nervous system.

Varicose Veins

• Enlarged, twisted veins due to ineffective valves.
• Common in legs, due to blood pooling.
• Risk factors: age, gender, family history, obesity, pregnancy, prolonged standing.
• Treatments range from conservative management to surgical interventions.

Review Questions

1. Define blood vessels and list the three major types.
2. Describe arteries and name the largest artery.
3. Define veins and identify the two largest veins.
4. Compare blood movement through arteries and veins.
5. Explain capillaries and their function.
6. Compare wall structures of arteries, veins, and capillaries.
7. Define blood pressure and its normal range.
8. Discuss functions of vasoconstriction and vasodilation.
9. Explain oxygen presence in veins.
10. True or False: Only one red blood cell can pass through a capillary at a time.
11. True or False: Pulmonary artery carries oxygenated blood.
12. Identify tissue responsible for vasodilation and vasoconstriction.
13. Compare blood pressure at arterioles and aorta.
14. Why are thin capillary walls important?
15. Most blood is located in capillaries, arteries, heart, or veins?

Additional Notes

• Images included for visual understanding of structures.
• Explore more sections for further learning.