Ch. 7.8 Circulatory System Key Terms
aortic valve
Located between the left ventricle and the aorta. It closes when the left ventricle is finished contracting, allowing blood to flow into the aorta (the largest artery in the body) and preventing blood from flowing back into the left ventricle.
circulatory system
Also known as the cardiovascular system, it is often referred to as the "transportation" system of the body. It consists of the heart, blood vessels, and blood, and it transports nutrients, wastes, oxygen, carbon dioxide, hormones, and antibodies.
left atrium
One of the two upper chambers of the heart that receives oxygenated blood from the lungs.
pericardium
A double-layered membrane, or sac, that covers the outside of the heart. A lubricating fluid (pericardial fluid) fills the space between the layers to prevent friction and damage as the heart beats.
septum
A muscular wall that separates the heart into a right side and a left side, preventing blood from moving between the two sides. The upper part is the interatrial septum, and the lower part is the interventricular septum.
arrhythmias
Abnormal heart rhythms that can be mild to life-threatening.
diastole
A brief period of rest in the cardiac cycle. During diastole, the atria relax, and blood returning from the body enters the right atrium, while blood returning from the lungs enters the left atrium.
left ventricle
One of the two lower chambers of the heart. It receives blood from the left atrium and pumps the blood into the aorta for transport to the body cells.
plasma
The fluid part of blood, which is approximately 90 percent water. It contains many dissolved or suspended substances, including blood proteins, nutrients, mineral salts, gases, and hormones.
systole
A period of ventricular contraction in the cardiac cycle. During systole, the right ventricle pushes blood to the lungs, and the left ventricle pushes blood to all other parts of the body.
arteries
Blood vessels that carry blood away from the heart. They are more muscular and elastic than other blood vessels because they receive blood as it is pumped from the heart.
endocardium
A smooth layer of cells that lines the inside of the heart and is continuous with the inside of blood vessels, allowing for the smooth flow of blood.
leukocytes
Also known as white blood cells. Their main function is to fight infection by engulfing, ingesting, and destroying pathogens (germs) through a process called phagocytosis.
pulmonary valve
Located between the right ventricle and the pulmonary artery. It closes when the right ventricle has finished contracting, preventing blood from flowing back into the right ventricle.
thrombocytes
Also called platelets. They are described as fragments or pieces of cells and are important for the clotting process, which stops bleeding.
blood
Often called a tissue because it contains many kinds of cells. It is composed of a fluid called plasma and formed or solid elements called blood cells (erythrocytes, leukocytes, and thrombocytes).
erythrocytes
Also known as red blood cells. They are produced in the red bone marrow and live about 120 days. They contain hemoglobin, and their function is to carry both oxygen and carbon dioxide.
mitral valve
Located between the left atrium and left ventricle. It closes when the left ventricle is contracting, allowing blood to flow into the aorta and preventing blood from flowing back into the left atrium.
right atrium
One of the two upper chambers of the heart that receives blood as it returns from the body cells.
tricuspid valve
Located between the right atrium and the right ventricle. It closes when the right ventricle contracts, allowing blood to flow to the lungs and preventing blood from flowing back into the right atrium.
capillaries
Blood vessels that connect arterioles with venules (the smallest veins). They have thin walls (only one layer of cells) that allow oxygen and nutrients to pass through to the cells, and carbon dioxide and metabolic products to enter the capillaries.
hemoglobin
A complex protein composed of the protein molecule called globin and the iron compound called heme. Hemoglobin is contained within erythrocytes and carries both oxygen and carbon dioxide.
myocardium
The thickest layer of the heart; it is the muscular middle layer.
right ventricle
One of the two lower chambers of the heart. It receives blood from the right atrium and pumps the blood into the pulmonary artery, which carries the blood to the lungs for oxygen.
veins
Blood vessels that carry blood back to the heart. Most veins contain valves that keep the blood from flowing in a backward direction.