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open circulatory system

A circulatory system that allows the blood to flow out of the blood vessels and into various body cavities so that the cells are in direct contact with the blood

closed circulatory system

a circulatory system in which the oxygen-carrying blood cells never leave the blood vessels


blood vessels that carry blood away from the heart


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


upper chamber of the heart that receives and holds blood that is about to enter the ventricle


a chamber of the heart that receives blood from an atrium and pumps it to the arteries

single circulation

a circulatory system consisting of a single pump and circuit, in which blood passes from the sites of gas exchange to the rest of the body before returning to the heart

double circulation

a circulatory system consisting of separate pulmonary and systemic circuits, in which blood passes through the heart after completing each circuit

left ventricle

the chamber on the left side of the heart that receives arterial blood from the left atrium and pumps it into the aorta

superior vena cava

receives blood from the head and arms and chest and empties into the right atrium of the heart

inferior vena cava

receives blood from lower limbs and abdominal organs and empties into the posterior part of the right atrium of the heart

sinoatrial node

pacemaker of the heart

AV (tricuspid) valve

A valve in the heart between each atrium and ventricle that prevents a backflow of blood when the ventricles contract.

semilunar valves

found at each of the two exits of the heart and prevents backflow of blood when the blood pumps

atrioventricular AV node

second pacemaker of the heart, impulses from SA node travel to here


The largest artery in the body; it conducts freshly oxygenated blood from the heart to the tissues.


thin layer of cells that lines heart cavities and blood vessels

systolic pressure

blood pressure in the arteries during contraction of the ventricles

diastolic pressure

the pressure in the arteries when the heart is at rest


the contraction of smooth muscle in artriole walls; increase blood pressure


relaxation of smooth muscles in the artrioles; causes blood pressure to fall

nitric oxide

reactive gas that plays a role in many body processes; promotes relaxation of smooth muscles around blood vessels which dilates and improves blood flow


red blood cells that transfer oxygen and don't have a nucleus


white blood cells that function in defense


irregularly, shaped cell fragments that help clot blood


a leukocyte that is able to migrate into tissues and transform into a macrophage which devours bacteria and antigens


A type of white blood cell that engulfs invading microbes and contributes to the nonspecific defenses of the body against disease.


a type of WBC that promotes inflammation and participates in allergic responses.


white blood cell that are responsible for combating infection by parasites


Make antibodies to destroy foreign pathogens; Make antibodies to destroy foreign pathogens

Countercurrent exchange

____ between the opposing movement of water and blood through blood vessels maximizes the diffusion of oxygen into the blood and carbon diozide into the water


Oxygen enters of carbon dioxide exits the trachea through openings called


Trachea bringes into 2 ____ which enter the lungs

Air rushes into the lungs

When the lunge volume increases, the air pressure with the lungs decreases which causes

There is an increase in respiratory rate

When carbon dixiode is in the blood, the pH drops so..

Lymph nodes

Enlarged bodies throughouit the lymphatic system, act as cleaning filters and as immune respone centers that defend against infection

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