Systemic arteries

Arteries carry blood away from the heart. Pulmonary artery is attached to the heart's right ventricle and it transports deoxygenated blood to the lungs to absorb oxygen and release carbon dioxide. The oxygenated blood then flows back to the heart. Systemic circulation moves blood between the heart and the rest of the body.

Systemic arteries transport oxygenated blood from the left ventricle to the body tissues. Blood is pumped from the ventricles into large elastic arteries that branch repeatedly into smaller and smaller arteries until the branching results in microscopic arteries called arterioles.

The arterioles play a key role in regulating blood flow into the tissue capillaries. Capillaries are the smallest and most numerous of the blood vessels. They connect between the arteries and the veins. The primary function of capillaries is the exchanging of materials, like oxygen, between the blood and tissue cells.

The main artery of the systemic circulation is the aorta. It carries oxygenated blood. It originates from the left ventricle of the heart, through an opening (regulated by the aortic valve), rises upward a short distance (known as “ascending aorta) and then sags back down to form the aortic arch (or systemic arch). The aorta branches into arteries of the body that go to different organs and body regions.

Arteries look like tubes. They have thicker and more muscular walls than veins so they can handle the force of blood coming from your heart’s left ventricle. Arteries of the body contain a high percentage of a special type of muscle, called smooth muscle, that can be controlled by hormones and special signals from the nervous system.

The artery's structure includes:
*An outer layer made of collagen fibers (Tunica externa)
*A middle layer of smooth muscle and elastic fibers (Tunica media)
*An inner layer called the endothelium (Tunica intima)
Systemic arteries

Systemic veins

Veins are a type of blood vessel that return deoxygenated blood from organs back to the heart for reoxygenation. These are different from the arteries, which deliver oxygenated blood from heart to the rest of the body.

After blood delivers oxygen to the tissues and picks up carbon dioxide, it returns to the heart through a system of veins. The capillaries, where the gaseous exchange occurs, merge into venules and these converge to form larger and larger veins until the blood reaches either the superior vena cava or inferior vena cava, which drain into the right atrium.

There are four types of veins:
*Deep veins are located within muscle tissue
*Superficial veins are closer to the skin’s surface
*Pulmonary veins transport blood that’s been filled with oxygen by the lungs to the heart
*Systemic veins

Systemic veins are located throughout the body from the legs up to the neck, including the arms and trunk. Systemic veins transport blood from the body tissue to the right atrium of the heart. This blood has a reduced oxygen content because the oxygen has been used for metabolic activities in the tissue cells.

The systemic veins may be arranged into three groups:
(1) The veins of the heart.
(2) The veins of the upper extremities, head, neck, and thorax, which end in the superior vena cava.
(3) The veins of the lower extremities, abdomen, and pelvis, which end in the inferior vena cava.

The inferior vena cava, also referred to as the posterior vena cava, is the largest vein in the human body. The superior vena cava is a large vein located in the upper anterior mediastinum. It is responsible for carrying deoxygenated blood from the upper body (head, neck, upper limbs, and some organs of the chest) to the heart.
Systemic veins