1. THE CIRCULATORY SYSTEM
3.4
The circulatory system in humans is the organ system that transports oxygen and nutrients throughout the body and carries away wastes. The system is made up of blood, the heart, and blood vessels.
circulatory system

2. THE CIRCULATORY SYSTEM
3.4
Blood is a type of connective tissue that circulates throughout the body. It has four components:
Red blood cells contain hemoglobin, which allows oxygen to be transported in the body.
White blood cells fight infection in the blood.
Platelets help blood clot.
Plasma is a protein-rich liquid that carries the blood cells.
The heart consists of three types of tissue—cardiac muscle tissue, nerve tissue, and connective tissue. Cardiac muscle tissue contracts to move blood throughout the body.
Three types of blood vessels create a network of tubes for transporting blood in the body. They include arteries, veins, and capillaries.
arteries veins capillaries

3. THE CIRCULATORY SYSTEM
3.4
Many conditions affect the function of the circulatory system. The most common heart problem is coronary artery disease, which can lead to a heart attack.
Coronary arteries are the blood vessels that carry blood to the heart muscle. Sometimes these arteries become partially blocked by plaque. Plaque is a deposit of fat, calcium, or other substances carried by the blood. Plaque buildup can be the result of poor lifestyle choices or of heredity. When plaque buildup occurs, heart attacks often follow.
When coronary arteries become completely blocked, the heart muscle no longer receives the oxygen it needs to function. The heart then stops and the tissue begins to die. Medical attention is needed immediately.
The white rectangle in this colourized X-ray image indicates the blockage in the artery of a patient’s heart