Vascular System Overview

The cardiovascular system (CVS) is responsible for transporting blood throughout the body, delivering oxygen and nutrients and removing waste products.

Arteries are blood vessels that carry blood away from the heart to various organs and tissues.

Veins carry blood back to the heart from organs and tissues.

Arteries generally carry oxygenated blood, except for the pulmonary and umbilical arteries.

The wall of an artery has three layers: the tunica intima, tunica media, and tunica adventitia.

The innermost layer of an artery is the tunica intima, a smooth endothelial lining.

The tunica media is the middle layer of an artery, composed of muscle and elastic fibers.

The outermost layer of an artery is the tunica adventitia, a fibrous coat.

Elastic arteries are large arteries with a thick media layer rich in elastic fibers.

Examples of elastic arteries include the aorta and its major branches, as well as the pulmonary trunk.

Muscular arteries are medium-sized arteries with a thicker media layer containing more smooth muscle and fewer elastic fibers.

Examples of muscular arteries include arteries in the limbs and organs.

Arterioles are small, thin-walled arteries with only smooth muscle in their media layer.

Vasa vasorum are blood vessels that supply the walls of large arteries.

Sympathetic nerve stimulation generally causes vasoconstriction (narrowing of blood vessels) in most parts of the body.

The sympathetic nerve supply to the brain, heart, and skeletal muscles does not cause vasoconstriction.

Capillaries are tiny blood vessels that connect arterioles and venules.

Capillaries have a single layer of endothelial cells, allowing for easy diffusion of gases, nutrients, and waste products.

Venules are small veins that collect blood from capillaries.

Veins have thinner walls than arteries and contain valves to prevent backflow of blood.

Large veins are larger than venules and have similar three-layered walls, but with less muscle and elastic tissue.

Examples of large veins include the superior and inferior vena cava, which drain blood from the upper and lower body, respectively.

The pulmonary circuit carries blood between the heart and the lungs.

The systemic circuit carries blood between the heart and the rest of the body.

Blood pressure is the force exerted by blood against the walls of blood vessels.

Systolic pressure is the highest pressure in the arteries during ventricular contraction.

Diastolic pressure is the lowest pressure in the arteries during ventricular relaxation.

Blood pressure is measured in millimeters of mercury (mmHg).

Normal blood pressure is typically around 120/80 mmHg.

High blood pressure (hypertension) can damage blood vessels and contribute to heart disease.