Heart

heart functions

• generating blood pressure

• routing blood

• one-way blood flow

• regulatiing blood supply

apex

• directed anteriorly

• inferiorly and to the left

• sits on the diaphragm

base

• directed posteriorly

• superiorly and to the right

anterior surface

deep to the sternum and ribs

inferior surface

rests on the diaphragm

right border

faces right lung

left border

• pulmonary border

• faces left lung

epicardium

• outer part of the heart

• serous pericardium is composed of a parietal layer and a visceral layer

pericardial cavity

Between the parietal and visceral layers of the serous pericardium

pericardial fluid

reduces friction between the two membranes

myocardium

• middle part of the heart

• cardiac muscle layer is the bulk of the heart allows heart to contract

endocardium

• chamber lining and valves

• Made up of simple squamous tissue allowing blood to flow

serous pericardium parietal layer

Surrounds the wall itself/pericardial cavity

fibrous pericardium

• Made up of dense irregular tissue

• Anchors the heart

• Protects the internal portion of the heart

• prevents the heart from overfilling with blood

auricles

• point towards the pulmonary trunk

• aids in increasing the capacity of the atriums

superior vena cava

carries deoxygenated blood to the right atrium from head neck and upper limbs

inferior vena cava

carries deoxygenated blood to the right atrium from the lower body

pulmonary trunk

passageway for blood to enter from the right ventricle

pulmonary veins

carries oxygenated blood from right and left lungs to the left atrium

pulmonary arteries

the only arteries that carries deoxygenated blood to the lungs to be oxygenated

aorta

main artery that carries blood away from the heart to the rest of the body

right atrium

receives blood from superior vena cava, inferior vena cava, coronary sinus

right and left ventricles

contains papillary muscles, chordae tendineae, intraventricular septum

papillary muscles

tightens the chordae tendineae to prevent the tricuspid valves from closing/opening when it’s not supposed to

chordae tendineae

• “heartstrings”

• cords between valve cusps and papillary muscles

Intraventricular septum

partitions ventricles

left atrium

Receives oxygen-rich blood from lungs via pulmonary veins (left and right)

left ventricle

Receives blood from left atrium and sends blood to the aorta

bicuspid valve

blood passes through into the left ventricle

tricuspid valve

• Blood flows through into right ventricle

• composed of dense connective tissue covered by endocardium

• aka right AV valve

atrioventricular valve

valves close preventing backflow of blood into atria, occuring when ventricles contract

blood flow steps

1. superior/inferior vena cava and coronary sinus drains deoxygenated blood into right atrium

2. blood moves through the tricuspid valve and into the right ventricle

3. blood moves through the pulmonary semilunar valve, into the pulmonary trunk into the pulmonary artery

4. blood moves into the lungs where gas exchange will take place (CO2/O2)

5. oxygenated blood enter the pulmonary veins and drains into the left atrium

6. from the Left atrium blood goes through the bicuspid valve into the left ventricle

7. from the left ventricle blood goes through the aortic semilunar valve into the aorta

8. blood moves to the rest of the body

coronary circulation

• flow of blood through the many vessels that flow through the myocardium of the heart

• delivers oxygenated blood and nutrients to, and removes carbon dioxide and wastes from, the myocardium

coronary arteries

Branches off aorta above aortic semilunar valve

left coronary artery

contains circumflex branch and anterior interventricular artery

circumflex branch

supplies left atrium and left ventricle

anterior interventricular artery

supplies both ventricles and intraventricular septum

right coronary artery

contains marginal branch and posterior interventricular artery

marginal branch

supplies right atrium, right ventricle, myocardium

posterior interventricular artery

supplies both R. and L. ventricles posterior myocardium

coronary veins

• Collects wastes from cardiac muscle

• drains into the coronary sinus

coronary sinus

• drains deoxygenated blood and empties into the right atrium

• large sinus on posterior surface of heart

autorhythmic cells

• cells fire spontaneously

• act as pacemaker and form conduction system for the heart

sino atrial node

• cluster of cells in wall of Rt. Atria creates electrical impulse

• begins heart activity that spreads to both atria

• excitation spreads to AV node

• 75 beats/min

Atrioventricular node

• in bottom of the atrium

• autorhythmic cells receives signal from SA node

• transmits signal to bundle of His

AV bundle of His

• connection between atria and ventricles

• Autorhythmic cells but slower than SA Node

• 40-60 beats per min

purkinje fibers

• large diameter fibers that conduct signals quickly (depolarization)

• contraction of the muscles sending out signals

heart conduction steps

1. Right atrium: Signal begins in the SA node, will generate an action potential (AP).

2. AP moves around right atrium into the left atrium.

3. All atrium are depolarized (contraction) squeezing blood into the ventricles

4. AV node: AV nodes receives the signals from SA nodes

5. signal is sent to bundle of his

6. signal travels down left and right branch of bundle of his, causing ventricles to depolarize

7. Purkinje fibers transmit the electrical signals along sides of the ventricles and up the heart walls and ventricle sides

electrocardiogram

• recording of the electrical changes that accompany each cardiac cycle (heartbeat)

• helps to determine if the conduction pathway is abnormal, if the heart is enlarged, and if certain regions are damaged

p wave

atrial contraction

p to q interval

conduction time from atrial to ventricular excitation

qrs complex

ventricular contraction

t wave

ventricular relaxation

“lubb” sound

• first heart sound

• blood turbulence associated with the closing of the atrioventricular valves

“dubb” sound

• second heart sound

• closing of the semilunar valves

cardiac cycle

• repetitive pumping process beginning with onset of contraction and ends with the beginning of the next contraction

• Blood flows from higher to lower pressure

systole

chamber contracting

diastole

chamber relaxing

ventricular filling

1. SA node fires and stimulates the Atrial contraction (p wave)

2. atrial contraction causes pressure in atrium to increase and push blood into the ventricles

3. ventricular volume slowly increases

4. atrial pressure falls, reversing pressure gradient, causing AV valves to close

5. produces first heart sound (“lubb”); systole begins

isovolumetric contraction

1. ventricular contraction occurs (qrs complex)

2. ventricular pressure increases, semilunar valves (SLV) are closed

3. ventricular volume is the same, no blood ejected until SLV open when ventricular pressure overcomes aortic pressure

rapid ejection

1. Aortic and Pulmonary semilunar valves open

2. blood is ejected out from the ventricles

3. volume decreases since blood decreases

isovolumetric relaxation

1. ventricular relaxation (t wave)

2. ventricular pressure falls, ejection force is reduced

3. second heart sound “dubb”; diastole begins

stroke volume

volume of blood pumped by each ventricle per beat (mL/beat)

cardiac output

• amount of blood ejected by each ventricle from the heart in one minute (approx. 4-6 L)

• need heart rate (beats/min) and stroke volume (mL/beat) to calculate

coronary artery disease

• condition where the heart muscle receives an inadequate amount of blood d/t obstruction of its blood supply

• causes include: atherosclerosis (hardening of blood vessels), coronary artery spasm, or a clot in a coronary artery

• risk factors: high blood cholesterol/pressure, cigarette smoking, obesity, diabetes, “type A” personality, sedentary lifestyle