Ch. 7.8 Circulatory System Key Terms
Aortic valve:
The valve (like a one-way door) that blood passes through to leave the heart's main pumping chamber (left ventricle) and enter the aorta, the body's largest artery.
Arrhythmias
An irregular or abnormal heartbeat, meaning it beats too fast, too slow, or with an uneven rhythm.
Arteries
Muscular tubes that carry oxygen-rich blood away from the heart to the rest of the body (the pulmonary artery is the one exception).
Blood
The fluid that circulates in the body, delivering oxygen and nutrients to cells and taking away waste products.
Capillaries:
Tiny, thin-walled blood vessels that connect arteries to veins. This is where the exchange of oxygen, nutrients, and waste happens with the body's tissues.
Circulatory system
The body's entire transport network, which includes the heart, blood vessels (arteries, veins, capillaries), and blood. Its job is to move blood throughout the body.
Diastole
The part of the heartbeat when the heart muscle relaxes to fill with blood. It's the "bottom number" in a blood pressure reading.
Endocardium
The thin, smooth membrane that lines the inside of the heart's chambers and covers the heart valves.
Erythrocytes
Their main job is to carry oxygen using hemoglobin.
Hemoglobin
The iron-rich protein inside red blood cells that attaches to oxygen in the lungs and carries it to the body's tissues.
Left atrium:
The top-left chamber of the heart. It receives oxygen-rich blood from the lungs.
Left ventricle
The bottom-left chamber of the heart. It is the strongest chamber and pumps oxygen-rich blood out to the entire body.
Leukocytes
White blood cells. They are the main cells of the immune system and help the body fight infections and diseases.
Mitral valve
The valve located between the left atrium and the left ventricle. It ensures blood flows in only one direction.
Myocardium
The heart muscle itself. It's the thick, muscular middle layer of the heart wall that contracts to pump blood.
Pericardium
The thin, protective sac that surrounds the outside of the heart, holding it in place and helping it work properly.
Plasma
The yellowish, liquid component of blood that holds the blood cells (red, white, and platelets) in suspension. It's mostly water but also contains proteins, hormones, and nutrients.
Pulmonary valve
The valve that blood passes through to leave the right ventricle and go to the pulmonary artery, which leads to the lungs.
Right atrium
The top-right chamber of the heart. It receives oxygen-poor blood returning from the body.
Right ventricle
The bottom-right chamber of the heart. It pumps the oxygen-poor blood to the lungs to get re-oxygenated.
Septum
The muscular wall that divides the right and left sides of the heart, keeping oxygen-rich and oxygen-poor blood from mixing.
Systole
The part of the heartbeat when the heart muscle contracts (squeezes) to pump blood out. It's the "top number" in a blood pressure reading.
Thrombocytes
Also known as platelets. These are small cell fragments in the blood that are essential for clotting and stopping bleeding.
Tricuspid valve:
The valve located between the right atrium and the right ventricle.
Veins:
Blood vessels that carry (mostly) oxygen-poor blood toward the heart from the rest of the body (the pulmonary veins are the exception).