9/2/20 Cardiac Anatomy & Physiology Myocardial Layers Heart - - PDF document

9/2/20 1

Cardiac Anatomy & Physiology

Jennifer Cheung, M SN, RN, CCRN

1

Cardiac Anatomy & Physiology – Myocardial Layers

Heart Muscle is compromised of three layers:

• Epicardium: serous membrane and is the external surface of the

heart

• It is surrounded by a thin, though layer of tissue called the
• Pericardium. The pericardium is a double-walled sac which serves as

protection for the heart.

• A slippery fluid between the two surfaces is called the Pericardial
• Fluid. This fluid serves as a lubricant and allows for smooth cardiac

contractions.

• Myocardium: middle muscular layer
• Endocardium: similar to epicardium
• Lines the interior heart chambers

Image Source: Wikipedia

2

Cardiac Anatomy & Physiology – Heart Chambers

The heart chambers are two pumps which work together to effectively oxygenate and circulate blood to the tissues of the body Two superior or upper chamber called Atria

• Right Atrium
• Left Atrium

Two inferior or lower chambers called Ventricles

• Right Ventricle
• Left Ventricle

Image Source: TexasHeart

3

Cardiac Anatomy & Physiology – Cardiac Valves

Cardiac valves ensure blood flows effectively in one direction through the 4 chambers of the heart

• The valves open and close when the heart contracts and relaxes as

pressure changes between the chambers

• As the valves open and close, the familiar “lub” ”dub” sound can be heard

upon auscultation The cardiac valves include

• Atrioventricular valves
• Bicuspid or Mitral Valve
• Tricuspid Valve
• Semilunar Valves
• Pulmonic Valve
• Aortic Valve

Image Source: TexasHeart

4

Cardiac Anatomy & Physiology – Cardiac Valves

Atrioventricular valves (AV Valves)

• The AV valves are located between the atria and

ventricles

• They are made of fibrous flaps called cusps
• Stringy tendinous (ten-din-us) cords, resembling a

parachute, connect the valves cusps to papillary muscles anchored on the ventricle floor

• When the ventricles contract, these muscles keep the

cusps closed to prevent blood from flowing back into the Atria

• Bicuspid or Mitral Valve (two cusps)
• Located between the left atrium and left ventricle
• Tricuspid Valve (three cusps)
• Located between the right atrium and right ventricle

Image Source: TexasHeart

5

Cardiac Anatomy & Physiology – Great Vessels

The great vessels is a term used to describe the four large vessels that bring blood to and from the heart

• Superior Vena Cava
• Returns blood from the head and arms
• Inferior Vena Cava
• Returns blood from the trunk and legs

Image Source: TexasHeart

6

9/2/20 2

Cardiac Anatomy & Physiology – Great Vessels

The great vessels is a term used to describe the four large vessels that bring blood to and from the heart

• Pulmonary Artery
• Transports blood from the heart to the lungs
• Pulmonary Veins
• Transports blood from the lungs back to the heart

Image Source: TexasHeart

7

Cardiac Anatomy & Physiology – Cardiac Cycle

The heart consists of two pumps which work together to oxygenate and circulate blood to the tissues The Cardiac Cycle is composed of

• Systole
• After the ventricles contract, pressure in the

ventricles exceed the arterial pressure causing the aortic and pulmonic valves to open

• Ejection Fraction: approximately 60% of the blood

in the ventricles flows out of the ventricles to the lungs and the body

• Diastole
• Most of the blood flows passively from the atria to

the ventricles

• Atrial Kick: When atria contract, 15-30% of

additional blood is forced into the ventricle

Image Source: TexasHeart

8

Cardiac Anatomy & Physiology – Systemic Circulation

A sophisticated network of vessels connect with the heart and lungs, circulating approximately 5 liters of blood to maintain and sustain the body. The circulatory system is compromised of systemic and pulmonary circulation.

• Systemic circulation carries oxygenated blood

from the heart, throughout the body (including heart muscle via coronary arteries) and deoxygenated blood returns to the heart

Image Source: Quizlet

9

Cardiac Anatomy & Physiology – Pulmonary Circulation

Pulmonary circulation moves deoxygenated blood from the heart through the lungs for oxygenation and back to the heart Unoxygenated blood

• Blood returns to the heart via the superior and inferior

vena cava, filling the right atrium

• Blood flows through the tricuspid valve and into the

right ventricle

• Blood is pumped through the pulmonic valve into the

pulmonary arteries and into the lung where it is

• xygenated

Image Source: Wikitonary

10

Cardiac Anatomy & Physiology – Pulmonary Circulation

Pulmonary circulation moves deoxygenated blood from the heart through the lungs for oxygenation and back to the heart Oxygenated blood

• The pulmonary veins receive oxygenated blood and fill

the left atrium

• Blood flows through the mitral valve into the left

ventricle

• Blood is pumped through the aortic valve and the aorta
• ut into the body

Image Source: Wikitonary

11

Cardiac Anatomy & Physiology – Coronary Vessels

The Right Coronary Artery (RCA) and Left Coronary Artery (LCA) systems provide blood flow to the heart. Both arteries are the first to branch from the aorta. Left Main Coronary Artery

• Location
• Originates from the left aortic sinus, above the aortic valve
• Branches into
• Left Anterior Descending Artery
• Circumflex Artery
• Perfuses
• Left heart

Image Source: John Hopkins

12

9/2/20 3

Cardiac Anatomy & Physiology – Coronary Vessels

The Right Coronary Artery (RCA) and Left Coronary Artery (LCA) system provide blood flow to the heart. Both arteries are the first to branch from the aorta. Left Anterior Descending Artery (LAD)

• Location
• Left lateral heart
• Branches into
• Diagonals
• Septal Perforators
• Perfuses
• Front and bottom of left ventricle
• Front of septal wall
• Bundle of His

Image Source: John Hopkins

13

Cardiac Anatomy & Physiology – Coronary Vessels

The Right Coronary Artery (RCA) and Left Coronary Artery (LCA) system provide blood flow to the heart. Both arteries are the first to branch from the aorta. Circumflex Artery

• Location
• Left posterior heart
• Branches into
• Marginal
• Obtuse Marginal
• Perfuses
• Left atrium
• Posterior and lateral side of left ventricle
• SA node and posterior descending artery

Image Source: John Hopkins

14

Cardiac Anatomy & Physiology – Coronary Vessels

The Right Coronary Artery (RCA) and Left Coronary Artery (LCA) system provide blood flow to the heart. Both arteries are the first to branch from the aorta. Right Coronary Artery (RCA)

• Location
• Originates from right aortic sinus at the base of the aorta
• Branches into
• Acute Marginal
• Inter-ventricular
• SA Node
• Perfuses
• Right atrium and ventricle
• Bottom of both ventricles and back of the septum
• SA and AV node
• Bundle of His and Posterior Descending Artery (PDA)

Image Source: John Hopkins

15

Cardiac Anatomy & Physiology – Coronary Vessels

The Right Coronary Artery (RCA) and Left Coronary Artery (LCA) system provide blood flow to the heart. Both arteries are the first to branch from the aorta. Posterior Descending (PDA)

• Location
• Posterior side of heart
• Branches into
• Right coronary artery
• Perfuses
• Posterior wall of the left ventricle
• Back of septum

Image Source: Stanford Health

16

Cardiac Anatomy & Physiology – Cardiac Cell Properties

Cardiac cells are responsible for the heart’s electrical and mechanical activity There are 2 types of cardiac cells Myocardial Cells

• Form the muscular layer of the atrial and ventricular walls
• Primary Function: contraction and relaxation

Pacemaker Cells

• Found in nodes , bundles, and branching networks in the heart
• Primary Function: conduction of electrical activity

17

Cardiac Anatomy & Physiology – Cardiac Cell Properties

Four main cardiac cell characteristics 1. Automaticity: heart’s ability to generate its own electrical impulse 2. Contractility: heart’s response to electrical stimulation in order to eject blood from the heart 3. Excitability: heart’s ability to react to and change the rate of contraction in response to additional or external stimuli 4. Conductivity: heart’s ability to transmit electrical impulses from cell to cell

18

9/2/20 4

Cardiac Anatomy & Physiology – Automaticity

Automaticity: ability of a cardiac muscle to fire off an electrical impulse on its own, without influence from adjacent cells Resting Phase

• No electrical activity. The cardiac cell is at rest

19

Cardiac Anatomy & Physiology – Automaticity

Automaticity: ability of a cardiac muscle to fire off an electrical impulse on its own, without influence from adjacent cells Depolarization

• The cell membrane of cardiac muscle holds on electrical charge which

changes with the movement of sodium, potassium, and calcium ions in different concentrations

• During depolarization, sodium ions enter the cell (through

sodium /potassium pumps) while potassium ions stream out

• Calcium ions stream into the cell through a different pump generating

impulse activity (causing action potential) and muscle cell contraction (electrical activity is seen as a tall, narrow deflection when printed on the ECG)

• Cardiac cells generate an electrical impulse that causes the ions to cross the

cell membrane causing depolarization

• As the conduction system send out waves of electrical activity, cardiac

muscle fibers respond by contracting (shortening) and relaxing (lengthening) Image Source: Difference Between

20

Cardiac Anatomy & Physiology – Automaticity

Automaticity: ability of a cardiac muscle to fire off an electrical impulse on its own, without influence from adjacent cells Repolarization

• The cell changes back to a relaxed state after depolarization
• Electrical activity can be seen as a more rounded, softer deflection when printed on the ECG

21