Chapter 14: The Heart and Heart Disease

Circulation

continuous one-way circuit of blood through the blood vessels

Heart

prime mover that propels the blood throughout the body

Average contractions (strokes) is

72 per minute from in utero to death.

Location of the Heart

• Between lungs in the center
• Slightly to the left
• About the size of your fist

Apex

pointed inferior portion, points to the left

Base

broad superior portion, large vessels attached to it

Endocardium

epithelial cells in a thin layer that lines the heart’s interior

• Smooth layer so blood flows easily
• Flaps of heart valves

Myocardium

muscle layer

my/o = muscle
cardi/o = heart

Epicardium

serous membrane forms the outermost layer

Also considered the visceral layer of the pericardium

The Pericardium

• Sac that encloses the heart
• Outer layer is serous membrane covers the surrounding area between heart and lungs (parietal layer)
• Folds back and cover the heart directly (visceral layer) AKA epicardium

Myocardium

• Lightly striated
• Have a single nucleus
• Involuntary

Intercalated Disks

modified plasma membranes that firmly attach adjacent cells to each other

Rapid transfer of electrical impulses

Pulmonary circuit

right side of heart that pumps blood low in oxygen into the lungs

Systemic circuit

left side of heart that pumps oxygenated blood through the body

Right atrium

receives blood returning from the body

Superior vena cava

brings blood from the head, chest and arms

Inferior vena cava

brings blood from trunk and lower extremities

Right ventricle

pumps blood received from the right atrium into the lungs via the pulmonary trunk

Pulmonary arteries

carry blood from the right ventricle to the lungs

Note: These vessels are carrying low oxygenated blood as veins do, but, because they carry blood away from the heart, they are considered arteries

Left atrium

receives blood high in oxygen from the lungs via the pulmonary veins

Left ventricle

largest muscle wall
• Pumps blood through the aorta into the body

Aorta

is the body’s largest artery
• Receives blood from the left atrium
• Makes up the entire apex of the heart

Septum

Separates chambers completely from each other

Interatrial Septum

separate the two atria

Interventricular Septum

separate the two ventricles

Atrioventricular Valves (AV)

between the atria and ventricles

Semilunar Valves

named because of their shape; exit valves

Right AV valve

AKA- Tricuspid

• Has three flaps (cusps)
• Found between the right atria and right ventricle
• Closes when right ventricle contracts, preventing backflow into the right atria

Left AV Valve

AKA- Mitral Valve

• Bicuspid (2 cusps/flaps)
• Looks like a Bishop’s Hat
• Between the left atrium and left ventricle
• Closes when the left ventricle contracts

Chordae Tendinae

• Thin fibrous threads attached to columnar muscles called papillary muscles
• Found in the walls of the ventricles
• Stabilizes the valve flaps to prevent backflow

Pulmonary Valve

AKA- Pulmonic Valve

• Semilunar
• Between the right ventricle and the pulmonary trunk
• pulmon/o (lungs)

Aortic Valve

• Semilunar
• Between the left ventricle and the aorta

Blood Supply to the Myocardium

• Coronary circulation
• Right and left Coronary Arteries
• Encircle the heart
• Receive blood during diastole from the aorta
• Cardiac veins bring blood back and empty into the right atrium via the coronary sinus

Endocardium, myocardium, epicardium

What are the names of the innermost, middle, and outermost layers of the heart wall?

Pericardium

What is the name of the sac that encloses the heart?

Atrium (atria)

What is the heart’s upper receiving chamber on each side called?

Ventricles

What is the lower pumping chamber called?

Direct the flow of blood through the heart

What is the purpose of each of the four valves in the heart?

Coronary circulation

What is the name of the system that supplies blood to the myocardium?

Heart Function- Systole

action phase (contraction)

Heart Function- Diastole

resting phase

Heart Function- Cardiac cycle

complete sequence of contraction and relaxation; about 0.8 seconds

Heart Function

• Systole begins with both atria contracting and emptying into the ventricles
• Atrial contraction is complete when ventricular contraction begins causing the AV valves to close producing the “lub” sound
• At this point, diastole has started in the atria, but systole is beginning in the ventricles
• When the ventricles have reached diastole, the semilunar valves close, causing the “dub” sound
• Then the entire heart rests for a short period

Cardiac Output (CO)

volume of blood pumped by each ventricle in 1 minute

Stroke Volume (SV)

volume of blood ejected from the ventricle with each beat

Heart Rate (HR)

number of beats per minute

• CO = HR x SV

Cardiac Output

• The more blood entering the heart, the more forceful the heart chambers contract.
• Stronger heart muscle results
• Less circulation, wimpy contractions, more likely blood will pool and develop clots