Human Anatomy: Chapter 20

The Heart

What is the primary function of the heart?

To pump blood through a closed system of blood vessels.

Where is the heart located?

Between the lungs in the mediastinum of the thoracic cavity.

What is the approximate size and weight of the heart? 

About the size of a fist and weighs less than one pound. 

How is the heart positioned in the body? 

About 2/3 to the left of the midsternal line; base at top, apex points to the left hip. 

What is the double-walled sac that encloses the heart?

The pericardium

What are the two layers of the pericardium?

Fibrous pericardium and serous pericardium

What does the fibrous pericardium do? 

Anchors the heart in place and protects it. 

What are the two layers of the serous pericardium?

Parietal layer (lines fibrous pericardium) and visceral layer (epicardium). 

What is the function of the pericardial cavity?

Contains serous fluid to reduce friction during heart movement. 

What is pericarditis?

Inflammation of the pericardium that causes friction and restricts movement.

What is cardiac tamponade?

Fluid buildup in the pericardial cavity that compresses the heart and limits contraction.

What are the three layers of the heart wall?

Epicardium, Myocardium, and Endocardium.

Which layer forms the bulk of the heart wall? 

The Myocardium.

What is the endocardium composed of?

Epithelial and connective tissue; lined with endothelium.

How many chambers does the heart have? 

Four (two atria and two ventricles)

What separates the two atria?

The Interatrial septum.

What separates the two ventricles?

The interventricular septum

What is the function of the atria?

To receive incoming blood and pump it into the ventricles.

What are auricles? 

Earlike extensions of the atria that increase surface area.

What is the fossa ovalis?

A remnant of the foramen ovale, which allowed fetal blood to bypass the lungs.

Which chambers have thicker walls and why?

The ventricles, because they pump blood to the body.

What are trabeculae carneae? 

Internal ridges in ventricles that prevent walls from sticking. 

What is the function of the heart valves?

To ensure one-way blood flow through the heart

What are the two atrioventricular (AV) valves?

Tricuspid (right side) and bicuspid/mitral (left side).

What are chordae tendineae and papillary muscles?

Structures that anchor AV valve flaps and prevent backflow.

What are the two semilunar (SL) valves?

Pulmonary semilunar and aortic semilunar valves

What do semilunar valves prevent?

Backflow of blood into the ventricles

What is valvular stenosis? 

Narrowing of valve openings due to stiff flaps.

What is mitral valve prolapse?

A condition where the mitral valve doesn’t close properly, allowing backflow. 

What are the three circulation patterns of the heart?

Pulmonary, systemic, and coronary circulation.

Trace the flow of blood through the heart.

Right atrium —> Tricuspid Valve —> Right ventricle —> Pulmonary SL Valve —> Pulmonary arteries —> Lungs —> Pulmonary veins —> Left atrium —> Bicuspid valve —> Left ventricle —> Aortic SL valve —> Aorta —> Body.

What is the function of the coronary arteries? 

Supply oxygenated blood to the myocardium

What is angina pectoris?

Chest pain caused by insufficient blood supply to the heart muscle.

What is myocardial infarction?

Death of heart tissue due to blocked blood flow (heart attack).

What type of muscle is cardiac muscle? 

Striated and involuntary

What are intercalated discs?

Structures that connect cardiac cells for strength and coordination.

What is autorhythmicity?

The heart’s ability to contract without external stimulation.

Why does cardiac muscle have many mitochondria?

To produce ATP for continuous contraction.

What is the function of the cardiac conduction system?

Coordinates heart contractions

List the conduction pathway in order

SA Node —> AV Node —> AV Bundle —> Bundle Branches —> Purkinje Fibers

What is the SA Node known as?

The pacemaker of the heart.

What is an arrhythmia?

Irregular heartbeat

What is tachycardia?

Heart rate above 100 bpm

What is bradycardia?

Heart rate below 60 bpm

What part of the brain controls heart activity? 

The medulla oblongata.

Define systole and diastole

Systole = Contraction; Diastole = Relaxation

What produces the “lubb” sound?

Closing of AV valves during ventricular systole.

What produces the “dubb” sound? 

Closing of semilunar valves at the end of systole

What are the three waves on an ECG?

P wave (atria contract), QRS complex (ventricles contract), T wave (ventricles relax)

What is cardiac output?

The amount of blood pumped by each ventricle per minute.

How does the sympathetic division affect heart rate? 

Increases heart rate via epinephrine and norepinephrine

How does the parasympathetic division affect heart rate?

Decreases heart rate after stress

When does the heart begin developing in the embryo? 

Around 19 days after conception

What is the foramen ovale?

A fetal opening that allows blood to bypass the lungs (right—>left atrium)

What is the ductus arteriosus?

A fetal vessel that connects the pulmonary artery to the aorta.

What is congestive heart failure? 

When the heart can’t pump efficiently, causing poor circulation. 

What is circulatory shock?

Inadequate blood supply to tissues; causes pale skin and cyanosis.

What is cardiac catheterization?

A diagnostic test using a catheter inserted into the heart.

What is echocardiography? 

Ultrasound imaging of the heart. 

Name common risk factors for heart disease.

High cholesterol, High BP, smoking, obesity, lack of exercise, age, genetics, gender, diabetes.