Veins

Veins are blood vessels that carry blood from the body back to the heart. They are part of the circulatory system, which is responsible for transporting blood, oxygen, and nutrients throughout the body.

Structure of Veins

Veins are composed of three main layers: the tunica intima, tunica media, and tunica externa. The tunica intima is the innermost layer, made up of endothelial cells and connective tissue. The tunica media is the middle layer, composed of smooth muscle and elastic tissue. The tunica externa is the outermost layer, consisting of connective tissue and collagen fibers.

Function of Veins

Veins function to carry deoxygenated blood from the body's tissues back to the heart. They have one-way valves that help prevent the backflow of blood and assist in returning blood to the heart, especially from the lower body against gravity.

Study Guide

1. What is the main function of veins in the body?
2. Describe the structure of veins, including the three main layers.
3. How do the one-way valves in veins help with blood flow?
4. What is the difference between arteries and veins?
5. Explain the role of veins in the circulatory system.