Circulatory system (LG 3)

What is the function of the atria?

Receive blood — right atrium from the body, left atrium from the lungs.

What is the function of the ventricles?

Pump blood — right ventricle to lungs, left ventricle to the body.

What does the septum do?

Separates the right and left sides of the heart to prevent mixing of oxygenated and deoxygenated blood.

What is the purpose of valves (tricuspid, bicuspid/mitral, pulmonary, aortic)?

Ensure one-way flow of blood and prevent backflow.

What are the two main types of circulation?

Pulmonary (heart–lungs–heart) and systemic (heart–body–heart).

Describe the flow of blood starting from the right atrium.

Right atrium to right ventricle to pulmonary artery to lungs to pulmonary veins to left atrium to left ventricle to aorta to body to vena cava to right atrium.

Why is the left ventricle thicker than the right?

It pumps blood to the whole body, requiring more force.

What are arteries and what do they do?

Thick-walled vessels that carry blood away from the heart under high pressure.

What are veins and what do they do?

Thin-walled vessels that return blood to the heart; contain valves to prevent backflow.

What are capillaries?

Tiny, one-cell-thick vessels where exchange of gases, nutrients, and waste occurs with tissues.

What are the 4 main components of blood?

Red blood cells, white blood cells, platelets, plasma.

What is the role of red blood cells (RBCs)?

Transport oxygen using hemoglobin.

What do white blood cells (WBCs) do?

Fight infections and form part of the immune system.

What is the function of platelets?

Help with blood clotting by forming plugs in damaged vessels.

What is plasma?

The fluid portion of blood that carries nutrients, hormones, and waste.

What is an open circulatory system?

Blood is not always inside vessels; it flows freely in body cavities (e.g., insects).

What is a closed circulatory system?

Blood is always contained in vessels (e.g., humans, fish, mammals).

How many heart chambers do fish have?

Two (1 atrium, 1 ventricle) – single circulation.

How many heart chambers do amphibians have?

Three (2 atria, 1 ventricle) – partial mixing of blood.

How many heart chambers do mammals and birds have?

Four (2 atria, 2 ventricles) – complete separation of oxygenated and deoxygenated blood.

What controls the heartbeat?

The sinoatrial (SA) node — the heart’s natural pacemaker.

What is the pathway of the electrical signal?

SA node to atria contract to atrioventricular (AV) node to bundle of His to Purkinje fibers to ventricles contract.

What causes the "lub-dub" sound of the heartbeat?

"Lub": closure of atrioventricular valves; "Dub": closure of semilunar valves.

How does the heartbeat adapt during exercise?

It increases in rate and strength to deliver more oxygen to muscles.