Circulation: in the body, the flow of blood through the heart and blood vessels, and the flow of lymph through the lymph vessels. (NCIt)

Transport (of) necessary materials to all the cells of an animal’s body and transport of waste products away from the cells. (Brooker, 995) The "heart" is a pump propelling "blood" through the body in a circular motion. (Bynum, 56) Adjective - 'circulatory.'

Blood: the body fluid that circulates in the … "blood vessels." Whole blood includes “plasma” and blood cells. (MeSH) A complex fluid, red when ‘oxygenated’ and containing various suspended cells, circulating in the "arteries" and “veins” of the higher animals. (Oxford) A "tissue" with “red blood cells,”  “white blood cells,”  “platelets,” and other substances suspended in fluid called plasma. Blood takes "oxygen" and nutrients to the tissues, and carries away wastes. (NCIt) Blood cells constantly die and (the) body makes new ones. Red blood cells live about 120 days, platelets 6 days and white blood cells less than a day. (MedlinePlus)

Blood Sugar: "glucose" (a type of sugar) found in the blood. (NCIt) The concentration of glucose in the blood. (Oxford) The amount of a sugar ... in a sample of your blood. "Hormones" made in the body called "insulin" and 'glucagon' help control blood glucose levels. (PubMedHealth2) Also referred to as 'blood glucose.'

Hemoglobin: a “globular” "protein" found in the blood of many animals where it is mainly responsible for transporting oxygen. (Indge, 135) The substance inside red blood cells that binds to oxygen in the lungs and carries it to the tissues. (NCIt)

Plasma: the clear, yellowish, fluid part of the blood that carries the blood cells. The proteins that form "blood clots" are in plasma. (NCIt) The liquid part of the blood. It consists mainly of water, but about 10% is made up of dissolved substances. Many of these dissolved substances, such as glucose, are maintained at relatively constant levels by the body's "homeostatic" mechanisms; others vary according to circumstances. (Indge, 210) The residual portion of blood that is left after removal of blood cells by ‘centrifugation.’ (MeSH)

Platelets: help blood clot when (there is) a cut or wound. (MedlinePlus) A tiny piece of cell that is made by breaking off of a large cell in the "bone marrow." Platelets are found in the blood and “spleen.” They help form blood clots to slow or stop bleeding, and to help wounds heal. (NCI1) Also referred to as ‘thrombocyte.’ 

Red Blood Cells: cells that deliver oxygen from your lungs to your tissues and organs. (MedlinePlus) A type of blood cell that is made in the bone marrow and found in the blood. Red blood cells contain a protein called hemoglobin, which carries oxygen from the lungs to all parts of the body. Checking the number of red blood cells in the blood is usually part of a complete blood test. It may be used to look for conditions such as "anemia," "dehydration," malnutrition, and "leukemia." (NCI1) Contains the red pigment, the principal function of which is the transport of oxygen. A mature (red blood cell) has no “nucleus.” There are normally about 5 trillion red blood cells per liter of blood. (OxfordMed) Also referred to as ‘erythrocytes’ and ‘RBC.’

White Blood Cells: cells that fight "infection" and are part of the body's defense system. (MedlinePlus) Any blood cell that contains a nucleus. (OxfordMed) Patrol the bloodstream in search of intruders. They have a nucleus containing “chromosomes.” (Watson, 37) A type of blood cell that is made in the bone marrow and found in the blood and "lymph" tissue. Part of the body’s "immune system." (NCI1) Also referred to as ‘leukocytes.’

Blood Vessel(s): any of the tubular vessels conveying the blood. (MeSH) A tube through which the blood circulates in the body. Blood vessels include a network of arteries, "arterioles," "capillaries," "venules," and veins. (NCIt) “Astrocytes” regulate blood vessel diameter in accordance with neuronal demand. (Fields, Figure 40)

Artery: any of the muscular-walled tubes forming part of the system of vessels by which blood is conveyed from the heart to all parts of the body. (Oxford) A blood vessel that carries blood from the heart to tissues and organs in the body. (NCIt) (Carries) blood away from the heart. All arteries except the "pulmonary artery" carry oxygenated blood. The walls of arteries contain smooth muscle fibers, which contract or relax under the control of the “sympathetic nervous system.” (OxfordMed) Adjective - ‘arterial.’

Arteriole: a small branch of an artery leading into many smaller capillaries. (OxfordMed) The smallest divisions of the arteries located between the muscular arteries and the capillaries. (MeSH) A small, terminal branch in the arterial system. Arterioles often connect to capillaries. (NCIt)

Capillary: a capillary vessel; especially any of the extremely narrow blood vessels. (Oxford) The minute vessels that connect the arterioles and venules. (MeSH) An extremely narrow blood vessel, approximately 5-20 microns in diameter. Capillaries form networks in most tissues. (The networks) are supplied with blood by arterioles and drained by venules. The vessel wall is only one cell thick, which enables exchange of oxygen, "carbon dioxide," water, salts, etc., between the blood and the tissues. (OxfordMed)

Vascular: relating to or supplied with “blood vessels.” (OxfordMed) Containing blood vessels. (NCIt) Consisting of, or containing vessels adapted for the carriage or circulation of fluid. In animals it refers to the blood and lymphatic systems. (Lawrence) Verb - ‘vascularize.'

Vein: any of the thin-walled tubes forming part of the system of vessels by which blood is conveyed back to the heart from all parts of the body. (Oxford) A blood vessel that carries blood to the heart from tissues and organs in the body. (NCIt) All veins (except the ‘pulmonary vein’) carry deoxygenated blood from the tissues via the capillaries. The walls of veins consist of three tissue layers, but these are much thinner and less elastic than those of arteries. Veins (usually) contain valves that assist the flow of blood back to the heart. (OxfordMed) Adjective - ‘venous.’

Venule: a minute vessel that drains blood from the capillaries. Many venules unite to form a vein. (OxfordMed)

Bone Marrow: the spongy material inside bones. Makes new blood cells. (MedlinePlus) The soft tissue in the center of bones that helps form all blood cells. (PubMedHealth2) The soft vascular fatty substance in the cavities of bones. (Oxford) Structure in which (white blood cells) mature into mature immune cells. (Booker, 1132)

Cardiovascular System: the heart together with two networks of blood vessels - the ‘systemic circulation’ and the ‘pulmonary circulation.’ (Lawrence) Effects the circulation of blood around the body, which brings about transport of nutrients and oxygen to the tissues and the removal of waste products. (OxfordMed) Includes arteries, arterioles, capillaries, heart, veins, and venules. (PubMedHealth) 

Valve: a structure, found in some tubular organs or parts, that restricts the flow of fluid within them to one direction only. Important structure in the heart, veins, and lymphatic vessels. (OxfordMed)