Vein Anatomy

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Veins carry blood toward the heart. Veins carry deoxygenated blood toward your heart and are often located close to your skin.

Red Blood Cells (RBCs)

Red blood cells, also known as erythrocytes, are the most common type of blood cell in the human body. They are responsible for carrying oxygen from the lungs to the body's tissues and carrying carbon dioxide, a waste product, from the tissues back to the lungs to be exhaled.


Veins have one-way valves that prevent blood from flowing backward, ensuring that the blood flows in the right direction, towards the heart.

Tunica Externa

The tunica externa is the outermost layer of fibrous connective tissue with nerve fibers, blood vessels, and lymphatic vessels. It provides structural support and protection to help withstand blood flow and pressure changes. It also contains collagen fibers that provide strength and elasticity, allowing the vein to expand and contract with blood flow.

Tunica Media

The tunica media, the middle layer of a vein, regulates vein diameter. It comprises smooth muscle cells and elastic fibers, allowing it to stretch and contract in response to blood pressure and volume changes. This layer also accommodates changes in blood volume by stretching through its elastic fibers, which is crucial for larger veins.

Tunica Intima

The tunica intima is the innermost layer of a vein and is composed of a thin layer of endothelial cells and connective tissue. The tunica intima plays a role in regulating blood flow and preventing the formation of blood clots. It is involved in regulating blood pressure by secreting substances that help to constrict or dilate blood vessels.