An artery is a blood vessel that carries oxygenated blood away from the heart to the rest of the body. Its structure consists of three main layers, each with distinct functions:

1. Tunica Intima (Inner Layer):
- Endothelium: A smooth, thin layer of endothelial cells that lines the inside of the artery, providing a slick surface to reduce friction and allow smooth blood flow.
- Basement Membrane: Provides structural support for the endothelial cells.
- Internal Elastic Lamina: A layer of elastic tissue that allows the artery to stretch and maintain pressure.

2. Tunica Media (Middle Layer):
- Smooth Muscle: The thickest layer, composed of smooth muscle cells that allow the artery to contract and regulate blood pressure and flow.
- Elastic Fibers: These fibers give the artery the ability to expand and recoil in response to the pressure from the heartbeat, maintaining steady blood flow.
- External Elastic Lamina: A thin layer of elastic tissue separating the tunica media from the tunica adventitia.

3. Tunica Adventitia (Outer Layer):
- Connective Tissue: Mainly composed of collagen and elastin fibers that provide structural support and protect the artery.
- Vasa Vasorum: Small blood vessels within the tunica adventitia that supply blood to the outer parts of large arteries.

Together, these layers help arteries withstand and regulate the high pressure of blood pumped by the heart.

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