Heart Anatomy and Physiology

What is the difference between veins and arteries?

Veins have thin walls, carry blood back to the heart, contain valves, and rely on skeletal muscle. Arteries carry blood away from the heart and have thick muscular walls.

What are the two major paths that lead to the right atrium?

Superior and inferior vena cava (systemic veins).

What are pulmonary veins and arteries?

They carry blood between the heart and lungs for gas exchange (CO₂ for O₂).

Function of pulmonary arteries?

Carry blood high in CO₂ and low in O₂ from the heart to the lungs.

Function of pulmonary veins?

Carry blood low in CO₂ and high in O₂ from the lungs to the heart.

Name and function of the top and bottom heart chambers?

Top = atria, receive blood. Bottom = ventricles, pump blood out of the heart.

Function of the left atrium?

Receives oxygen-rich blood from the lungs and pumps it to the left ventricle.

Function of the left ventricle?

Receives blood from the left atrium and pumps it to the body through the aorta.

Function of the right atrium?

Receives oxygen-poor blood from the vena cava and pumps it to the right ventricle.

Function of the right ventricle?

Receives blood from the right atrium and pumps it to the lungs through the pulmonary artery.

Function of the mitral valve?

Located between the left atrium and left ventricle; prevents backflow.

Function of the tricuspid valve?

Located between the right atrium and right ventricle; prevents backflow.

What is an atrioventricular valve? Name two.

Valves between atria and ventricles. Examples: mitral (bicuspid) and tricuspid valves.

What happens if an AV valve leaks?

Blood backflows from the ventricle to the atrium.

Role of the septum?

Separates oxygen-rich blood (left side) from oxygen-poor blood (right side).

What does the “lub-dub” heart sound represent?

“Lub” = tricuspid and mitral valves closing. “Dub” = beginning of ventricular diastole.

What is being felt when a doctor takes your pulse?

The surge of blood from ventricular contraction through the arteries.

Difference between diastolic and systolic pressure?

Systolic = heart contracting. Diastolic = heart relaxed.

How is blood moved in veins with little pressure?

Skeletal muscles squeeze veins, and valves prevent backflow.

Blood flow speed in arteries vs veins tells us what?

More blood volume is in the veins (~64%) than arteries (~15%) at any moment.

Pulmonary ventilation

The process of moving air in and out of the lungs (breathing).

External respiration

The exchange of gases (O₂ and CO₂) between alveoli and pulmonary capillaries.

Pulmonary transport

The movement of respiratory gases (O₂ and CO₂) through the bloodstream.

Internal respiration

Gas exchange between blood and body cells.

Cellular respiration

Cells use O₂ to produce ATP from glucose; releases CO₂.

Isovolumetric contraction

The phase in the cardiac cycle when ventricles contract with no volume change; all valves are closed.

Isovolumetric relaxation

The phase after ventricular ejection when ventricles relax but all valves remain closed.

Rapid inflow

Part of ventricular diastole when AV valves open and blood rushes into the ventricles.

Atrial contraction

Phase where atria contract to push the last bit of blood into the ventricles.

Ejection

Phase where ventricles push blood into the aorta and pulmonary artery.

P wave

Depolarization of the atria.

QRS complex

Depolarization of the ventricles (also hides atrial repolarization).

T wave

Repolarization of the ventricles.

SA node

The pacemaker of the heart; initiates the electrical signal.

AV node

Delays the electrical impulse to allow atrial contraction before ventricles contract.

Bundle of His

Conducts impulses from AV node to the bundle branches.

Bundle branches

Carry impulses down the interventricular septum.

Purkinje fibers

Distribute the electrical impulse throughout the ventricles.

Aorta

Largest artery; carries oxygenated blood from the left ventricle to the body.

Pulmonary trunk

Origin of pulmonary arteries; carries deoxygenated blood to the lungs.

Pulmonary veins

Vessels that return oxygenated blood from lungs to left atrium.

Vena cava

Large veins (superior and inferior) that return deoxygenated blood to right atrium.

Right atrium

Receives blood from the body; sends it to the right ventricle.

Right ventricle

Pumps deoxygenated blood to lungs via pulmonary arteries.

Left atrium

Receives oxygenated blood from lungs; sends it to left ventricle.

Left ventricle

Pumps oxygenated blood to the body through the aorta.

Tricuspid valve

Prevents backflow from right ventricle to right atrium.

Bicuspid (mitral) valve

Prevents backflow from left ventricle to left atrium.

Pulmonary semilunar valve

Prevents backflow from pulmonary artery into right ventricle.

Aortic semilunar valve

Prevents backflow from aorta into left ventricle.

Chordae tendineae

Fibrous cords that prevent valve inversion.

Papillary muscles

Muscles that anchor the chordae tendineae and help keep AV valves closed.

Pericardium

Double-walled sac that surrounds and protects the heart.

Myocardium

Muscular middle layer of the heart wall responsible for contraction.

Endocardium

Inner lining of the heart chambers.

Heart

Pumps blood through the body

Arteries

Carry blood away from the heart; thick muscular walls; high pressure

Veins

Carry blood to the heart; thinner walls, valves; low pressure

Capillaries

Allow exchange of gases, nutrients, and waste; one-cell-thick wall

Blood

Transports oxygen, nutrients, and waste; includes RBCs, WBCs, platelets, plasma

Right atrium

Receives deoxygenated blood from body via vena cava

Tricuspid valve

Prevents backflow between right atrium and right ventricle

Right ventricle

Pumps deoxygenated blood into pulmonary artery

Pulmonary valve

Prevents backflow into right ventricle

Pulmonary artery

Carries deoxygenated blood to lungs

Pulmonary veins

Return oxygenated blood from lungs to heart

Left atrium

Receives oxygenated blood from lungs

Bicuspid (mitral) valve

Prevents backflow between left atrium and left ventricle

Left ventricle

Pumps oxygenated blood to body through aorta

Aortic valve

Prevents backflow into left ventricle

Aorta

Largest artery; sends oxygenated blood to body

Pulmonary circuit

Right heart → lungs → left heart; oxygenates blood; low-pressure system

Systemic circuit

Left heart → body → right heart; delivers oxygen; high-pressure system

SA node

Pacemaker; initiates heartbeat and atrial contraction

AV node

Delays signal; allows atria to finish contracting

Bundle of His

Conducts signal from AV node down the septum

Purkinje fibers

Distribute signal through ventricles, causing contraction

P wave

Atrial depolarization (contraction) (atria)

QRS complex

Ventricular depolarization (contraction)

T wave

Ventricular repolarization (resetting)

ST segment

Early part of ventricular repolarization

PR interval

Time between onset of atrial depolarization and onset of ventricular depolarization (Atria, AV node, Bundle of His)

"Lub" sound

AV valves closing (start of ventricular systole)

"Dub" sound

Semilunar valves closing (start of ventricular diastole)

Murmur

Abnormal heart sound caused by turbulent flow (valve issues)

Systolic pressure

Pressure during heart contraction (top number)

Diastolic pressure

Pressure during heart relaxation (bottom number)

Normal BP

Approximately 120/80 mmHg

Blood pressure influences

Blood volume, vessel diameter, cardiac output

Pulse pressure

Systolic - Diastolic

MAP (Mean Arterial Pressure)

Diastolic + 1/3(Pulse Pressure)

Cardiac output

Stroke Volume × Heart Rate

Stroke volume

Approx. 70 mL per beat

Average cardiac output

~5 L/min at rest

Atrial systole

Atria contract and push blood into ventricles (0.1 sec)

Ventricular systole

Ventricles contract, AV valves close ("lub"), blood ejected (0.3 sec)

Diastole

All chambers relax, semilunar valves close ("dub"), heart fills with blood (0.4 sec)

AV valves

Tricuspid and bicuspid/mitral; prevent backflow into atria

Semilunar valves

Aortic and pulmonary; prevent backflow into ventricles

Ventricular pressure

Rises during systole; must exceed artery pressure to open semilunar valves