Science Test - Heart & Lungs

Artery

A blood vessel that carries blood away from the heart. Except for the pulmonary artery, all arteries transport oxygen-rich blood.

Vein

A blood vessel that returns blood to the heart. Except for the pulmonary vein, all veins transport deoxygenated blood.

Capillary

Tiny, thin-walled blood vessels that connect arteries to veins. They are the site of gas, nutrient, and waste exchange between blood and body cells.

Heart

The muscular organ that pumps blood throughout the body. Contains four chambers: right atrium, right ventricle, left atrium, and left ventricle.

Atrium

Either of the two upper chambers of the heart that receives blood from veins.

Ventricle

Either of the two lower chambers of the heart that pumps blood out to the arteries.

Heart Valves

Structures that open and close to control blood flow through the heart. Allow blood to flow in one direction only. There are four valves: two atrioventricular and two semilunar valves.

Aorta

The major artery that takes blood away from the heart to the systemic circulatory system.

Pulmonary Artery

The artery that carries deoxygenated blood from the right ventricle to the lungs.

Pulmonary Vein

The vein that carries oxygenated blood from the lungs to the left atrium.

Trachea

Also known as the windpipe. A tube that carries air from the larynx to the bronchi.

Bronchi

The two large tubes that branch off from the trachea and lead to each lung.

Alveoli

Tiny air sacs at the end of the bronchioles where gas exchange occurs between the air and the blood.

Pulmonary Circulation

The flow of blood away from the heart through the lungs where oxygenation occurs and then back to the heart.

Systemic Circulation

The flow of blood away from the heart to the brain, liver, kidneys, stomach, organs, limbs, and muscles, and then back to the heart.

Blood Components

Blood is made of four parts: red blood cells (carry oxygen via hemoglobin), white blood cells (fight infection), platelets (help clotting), and plasma (liquid that carries cells, nutrients, hormones, and waste).

Hemoglobin

An iron-containing protein in red blood cells that binds to oxygen, transports it from the lungs to body tissues, and carries some CO₂ back to the lungs. Gives blood its red color.

Blood Pressure

The force of blood against blood vessel walls (mmHg). Systolic = pressure when heart contracts; diastolic = pressure when heart relaxes. Affected by vessel diameter, blood volume, and heart rate.

Coronary Arteries

Arteries that branch off the aorta and supply oxygen and nutrients directly to the heart muscle. Blockage can cause a heart attack.

Left Ventricle

The lower left chamber that pumps oxygenated blood through the aorta to the entire body. Its wall is thicker than the right ventricle because it must generate greater force.

Diaphragm

A dome-shaped muscle below the lungs. Contracts and flattens during inhalation (expanding chest cavity); relaxes and rises during exhalation (pushing air out). Works with intercostal muscles.

Immune System

The body's defense system. First line: physical barriers (skin). Internal defense: T-cells and B-cells target specific pathogens, B-cells produce antibodies, and macrophages engulf harmful organisms.

What is the difference between pulmonary and systemic circulation?

Pulmonary circulation carries deoxygenated blood from the heart to the lungs and back. Systemic circulation carries oxygenated blood from the heart to all other body organs and tissues and returns deoxygenated blood to the heart.

What is the main function of the heart?

The heart pumps blood throughout the body — sending deoxygenated blood to the lungs and oxygenated blood to the rest of the body.

What happens during gas exchange in the alveoli?

Oxygen diffuses from the alveoli into surrounding capillaries, while carbon dioxide diffuses from the blood into the alveoli to be exhaled.

How do the trachea, bronchi, and alveoli work together?

Air enters through the trachea, splits into the bronchi leading to each lung, branches into smaller tubes, and reaches the alveoli where gas exchange occurs.

What is the role of heart valves?

Heart valves prevent backflow of blood, ensuring one-directional flow. Atrioventricular valves prevent backflow into the atria; semilunar valves prevent backflow into the ventricles.

Describe the path of blood through the heart and lungs.

Deoxygenated blood → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta → body.

Why does the pulmonary vein carry oxygenated blood instead of the pulmonary artery?

Because veins carry blood toward the heart and arteries carry blood away from the heart — the pulmonary vein returns oxygenated blood from the lungs back to the heart, regardless of oxygen content.

What factors affect blood pressure?

Blood vessel diameter (vasoconstriction raises it, vasodilation lowers it), blood volume, heart rate, and the force of heart contractions.

Why is the left ventricle wall thicker than the right?

The left ventricle pumps blood through the aorta to the entire body, requiring more force than the right ventricle, which only pumps blood to the nearby lungs.

How do the diaphragm and intercostal muscles work during breathing?

During inhalation, both contract to expand the chest cavity and fill the lungs. During exhalation, both relax, the chest cavity shrinks, and air is pushed out.

What is the function of the coronary arteries?

They supply oxygen and nutrients to the heart muscle cells by branching off the aorta. Blockage leads to a heart attack.

How does the immune system protect the body?

Through physical barriers (skin), T-cells and B-cells targeting specific pathogens, B-cells producing antibodies, macrophages engulfing harmful organisms, and the circulatory system transporting immune cells throughout the body.