Circulatory System
The muscular organ that pumps blood throughout the body.
heart
Either of the two respiratory organs that take in oxygen and expel carbon dioxide.
lung
To press firmly together; to contract.
squeeze
A tiny infectious agent that replicates only inside the living cells of an organism.
virus
One complete cycle of contraction and relaxation of the heart.
heartbeat
The red liquid that circulates in the heart, arteries, and veins, carrying oxygen and nutrients.
blood
The large airway that leads from the larynx to the bronchi, also called the windpipe.
trachea
To have something inside; to hold.
contain
Microscopic single‑celled organisms found everywhere, some of which can cause disease.
bacteria
A long, hollow cylinder used for carrying liquids or gases.
tube
A large blood vessel that carries blood away from the heart to the body.
artery
A large, dome‑shaped muscle below the lungs that helps with breathing.
diaphragm
To find out the size, amount, or degree of something using an instrument.
measure
A disorder of structure or function in a human, animal, or plant, producing specific symptoms.
disease
A substance that provides nourishment essential for growth and life.
nutrient
A blood vessel that carries blood back toward the heart.
vein
A gas produced during breathing and combustion, exhaled by animals and used by plants.
carbon dioxide
To move a fluid (like blood) by mechanical action; also a device that does this.
pump
To contaminate a living organism with a disease‑causing agent.
infect
The rhythmic expansion of an artery caused by the beating of the heart.
pulse
The smallest type of blood vessel, connecting arteries and veins.
capillary
To move smoothly and continuously in a current or stream.
flow
Large, serious, or significant in size, number, or effect.
major
Resistant to a particular infection or toxin because of specific antibodies.
immune
A set of organs or parts that work together to perform a function in the body.
system