The process by which water molecules move across a cell membrane from an area of higher concentration to an area of lower concentration.


The process by which molecules move from an area of higher concentration to an area of lower concentration


Blood vessels that carry blood from the heart to the body tissues.


Tiny, thin-walled blood vessels that allow the exchange of gases and nutrients between the blood and the cells of the body.


Blood vessels that carry deoxygenated blood from the body tissues to the heart.


A mixture of constanly circulationg red blood cells, white blood cells, platelets and plasma that transports gases, nutrients, wastes, and other important substances around the body.


Tiny sacs of lung tissue specialized for the movement of gases between the air and the blood. It is here that oxygen molecules bind to hemoglobin, a red blood cell protein.

systolic blood pressure

Pressure in the artery when the left ventricle is contracting to force the blood into the aorta and other arteries.

diastolic blood pressure

Pressure in the artery when the ventricles are relaxing and the heart is filling, receiving blood from the venae cavae and pulmonary veins.


Greek surgeon who studied the body and described the valves of the heart and noted differences between arteries and veins.

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