A vein is one of several types of blood vessels that transport blood around the body.
The structure of a vein is as follows:
The walls (outer structure) of veins consist of three layers of tissues that are thinner and less elastic than the corresponding layers of arteries. Veins include valves that aid the return of blood to the heart by preventing blood from flowing in the reverse direction.
The functions of veins include:
- Transport blood towards the heart
- Carry de-oxygenated blood
(except in the case of the pulmonary vein)
- Have relatively wide lumens
- Have relatively less muscle/elastic tissue than arteries
- Transports blood under lower pressure than arteries
- Have valves throughout the main veins of the body. These are to prevent blood flowing in the wrong direction, as this could (in theory) return waste materials to the tissues.
For more information about blood vessels and the components (sometimes called the 'constituents') of blood see the pages about the the structure and functions of blood vessels and the structure and functions of blood. This might interest students of holistic massage, reflexology, beauty therapies, or health-related courses.