Blood Arteries and Veins

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Definitions.

Arteries and veins are types of blood vessels that transport blood around the body. Arteries carry blood away from the heart, while veins return it.

Blood vessels form two systems going to and from the heart. These two systems form the blood circulatory system.

Systemic circulation supplies oxygen and other vital substances to organs, tissues, and cells.

The systemic arteries transport oxygen-rich blood from the left ventricle to the rest of the body. Afterward, the blood that is now low in oxygen is collected in systemic veins and travels to the right atrium.

Pulmonary circulation is where fresh oxygen enters the blood.

Pulmonary arteries transport low oxygen blood from the right ventricle to the lungs. Pulmonary veins then transport oxygen-rich blood back to the heart through the left atrium.

Capillaries are a third type of blood vessel in the body. They carry blood between arteries and veins.

Types of arteries

There are three types of arteries:

Elastic arteries

Elastic arteries are the large vessels coming out of the heart. For example, they include the pulmonary artery and the aorta. The aorta is the main artery carrying blood away from the heart.

The heart forcefully pumps blood out to keep it moving around the body. Elastic arteries must be flexible to handle surges of blood. They expand as the heart pushes blood out.

Elastin is a protein found in many tissues that allow flexibility, including elastic arteries.

Muscular arteries

Elastic arteries feed blood into muscular arteries, such as the femoral or coronary arteries.

Smooth muscle fibers make up the walls of muscular arteries. The muscles allow these arteries to expand and contract. These changes in size control how much blood moves through the arteries.

Arterioles

Arterioles are the smallest type of artery. They distribute blood from larger arteries through networks of capillaries.

The outer layer of arterioles also contains smooth muscle that allows for expansions and contractions.

Types of veins

The same layers make up arteries and veins, but veins are thinner and have less muscle, allowing them to hold more blood. Veins typically contain around 70% of blood in the body at any one time.

Venules are the smallest type of vein. They have very thin walls to hold lots of blood. They feed low-oxygen blood through capillaries from arteries directly into veins. The blood then moves back to the heart through a series of veins of increasing size and muscle.

There are two main types of veins, pulmonary and systemic.

People can further classify systemic veins into either:

• Deep veins: These veins usually have a corresponding artery nearby and are in muscle tissue. These veins may have a one-way valve to prevent blood from flowing backward.
• Superficial veins: These veins do not have an artery with the same name nearby and are close to the surface of the skin. They may also have a one-way valve.
• Connecting veins: These small veins allow blood to flow from the superficial veins to the deep veins.

Anatomy

Veins and arteries consist of three layers:

• Tunica adventitia: The outer layer of a blood vessel consists of collagen and elastin and is known as the tunica adventitia. This layer allows the vessel to expand or contract, depending on what type of vein or artery it is. This feature is important for controlling blood pressure.
• Tunica media: This is the middle later of a blood vessel. Elastin and muscle fibers make up the tunica media. The amount of elastin or muscle varies, depending on the type of blood vessel. For example, elastic arteries contain few muscle fibers in their tunica media.
•  Tunica indirection:
• This name refers to the inner layer of a blood vessel. It mostly contains elastic membranes and tissues and can include valves that help the blood move in the right direction. 

Cardiovascular system

The cardiovascular system refers to the heart and blood vessels together. The system makes up a closed circuit of vessels that transport blood around the body.

The cardiovascular system is essential to support human life. It is the first major organ network to develop in an embryo.

All body tissues need oxygen and nutrients to survive. They also require the removal of waste substances that are a byproduct of metabolism.

The blood is essential to both providing oxygen and nutrients and removing waste from tissues.

The heart pumps blood around the body. It must work constantly and with enough force to ensure all bodily tissues receive blood to function. Disruptions to the cardiovascular system can have severe consequences.

Cardiovascular diseases are a group of disorders that affect the heart and blood vessels, such as coronary heart disease.

These diseases are the leading cause of death worldwide, accounting for around 17.9 million deaths in 2016.

Summary

Arteries are a type of blood vessel that transports blood away from the heart. Veins carry blood back to the heart. Along with capillaries, these blood vessels are responsible for moving blood to and from tissues around the body.

The heart pumps blood through a complex system of blood vessels. There are several types of arteries and veins with different functions. For example, some contain more muscle for changing how much blood they carry.

The cardiovascular system is essential to human life. Disruptions in the heart or blood vessels can be severe and, sometimes, fatal.

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