Cardiac Anatomy, Function, and the Cardiac Cycle

pericardial sac

lining that surrounds the heart and helps to reduce friction

LAYERS:

1. fibrous (outer)

2. parietal (inner cavity wall)

pericardial fluid

serous fluid between parietal & visceral pericardium

*reduces friction when heart beats

**contains mesothelial cells

pericarditis

inflammation of the pericardial sac surrounding the heart

epicardium, myocardium, endocardium

What are the 3 layers of the heart wall?

epicardium

aka visceral pericardium

outer layer of heart muscle tissue

CONTAINS:

1. coronary vessels

(supply blood to the heart muscle)

2. fat

(cushion, shock absorber)

3. loose connective tissue

4. mesothelial cells

*added protection

myocardium

the middle, muscular layer of the heart wall

4 chambers & 4 valves

*contains cardiomyocytes and fibroblasts

**has contractile and pacemaker function

structural integrity--> collagen production

endocardium

inner lining of the heart

*contains endothelial cells

**barrier between vessels and blood

***has anti-inflammatory & anticoagulant properties

endocarditis

inflammation of the inner lining of the heart

*typically a valve issue

epicardium

The great vessels are part of which layer of the heart?

inferior vena cava (IVC)

returns blood from portions of the body below the heart to the right atrium

superior vena cava (SVC)

receives blood from the head and arms and chest and empties into the right atrium of the heart

aorta

large arterial trunk that carries blood from the heart to be distributed by branch arteries through the body

BRANCHES FROM ARCH:

1. brachiocephalic (innominate)

2. common carotid

3. subclavian

brachiocephalic, left common carotid, left subclavian

What are the 3 branches off of the aortic arch?

brachiocephalic (innominate) artery

the first major branch off of the aorta and the major artery to the forelimbs and head

left common carotid artery

the second major branch off of the aorta that supplies the head and neck

left subclavian artery

the third branch of the aortic arch that distributes blood to the left arm

*commonly utilized during bypass surgery

pulmonary trunk

carries blood from right ventricle to the R & L pulmonary arteries

*carries deoxygenated blood

internal thoracic artery

branch of left subclavian artery that supplies the pericardium and anterior wall of the chest

aka left internal mammary artery (LIMA)

**used during bypass surgeries

pulmonary circuit, systemic circuit

What are the 2 circulation systems of the heart?

pulmonary circuit

carries deoxygenated blood to the lungs for gas exchange and returns it to the heart

1. SVC

2. IVC

3. pulmonary trunk

RA--> RV--> lungs

systemic circuit

transports oxygenated blood to and from the rest of the body

1. pulmonary veins

2. aorta

LA--> LV--> body

systemic (pushes blood to entire body)

Is the pulmonary or systemic circuit under a greater amount of pressure?

mitral, aortic semilunar

Which 2 valves are more commonly involved with pathologies?

HINT: high pressure

atria

upper chambers of the heart

push blood to the ventricles

(primarily gravity)

*pectinate muscle

**auricles

pectinate muscle

internal ridges of myocardium in right atrium and both auricles

*smooth lining with minimal ridges

auricle

aka atrial appendages

the externally visible flap formed by the collapse of the outer wall of a relaxed atrium

ventricles

the two lower chambers of the heart

*work anti-gravity

- trabeculae carneae

- Purkinje fibers

- interventricular septum

trabeculae carneae

thick muscular ridges on the internal surface of the ventricles

*main contractile tissue

**decreases suction chance

Purkinje fibers

fibers in the ventricles that transmit impulses to the right and left ventricles

*causes contraction

(<40 bpm)

interventricular septum

partition between the right and left ventricle

*important for electrical conduction

papillary muscles

responsible for pulling the atrioventricular valves closed by means of the chordae tendineae

chordae tendinae

fibers attached to the tricuspid and mitral valve which pull it closed when papillary muscles contract

*preventing back flow of blood

**maintain structural support of valve

tricuspid, mitral

What are the 2 atrioventricular (AV) valves?

pulmonary, aortic

What are the 2 semilunar valves?

tricuspid valve

valve between the right atrium and the right ventricle

mitral valve

valve between the left atrium and the left ventricle

pulmonary semilunar valve

heart valve opening from the right ventricle to the pulmonary artery

aortic semilunar valve

heart valve located between the left ventricle and the aorta

tricuspid, mitral

What valves are OPEN during DIASTOLE?

aortic, pulmonary

What valves are OPEN during SYSTOLE?

SA (sinoatrial) node

pacemaker of the heart

*60-100 bpm

AV (atrioventricular) node

backup generator

(40-60 bpm)

conducts impulses to AV bundle in interventricular septum

*delays impulse, so that atria finish contracting before ventricles contract

increase in blood pressure

To maintain CO when HR decreases, SV must increase. How is this typically accomplished?

ECG cycle

graphic representation of cardiac cycle

2/3 = filling time (SV)

1/3 = contraction time (HR)

P wave

atrial depolarization

(contraction/systole)

QRS complex

ventricular depolarization

(contraction/systole)

Q wave

initial negative deflection produced by ventricular depolarization

simultaneous with blood entering ventricles

S wave

ventricular muscles begin to relax

R

Problems with the ___ wave of an ECG are the most concerning.

T wave

ventricular repolarization (relaxation/diastole)

*should be bigger than P wave

amplitude (force of contraction)

The vertical height on a ECG is what?

refractory period

a period of inactivity represented by horizontal line on ECG

lub

S1

sound heard w/ closing of AV valves

*occurs at ventricular systole

dub

S2

sound heard w/ closing of semilunar valves

*occurs at ventricular diastole

when all 4 valves are closed

The onset of diastole occurs when?

coronary arteries

blood supply to the heart muscle

*found in epicardium

1. R coronary artery (RCA)

2. L (main) coronary artery (LCA)

- L anterior descending artery (LAD)

- L circumflex artery (LCx)

right coronary artery (RCA)

dominant supplier of heart muscle

left (main) coronary artery (LCA)

devastating when occluded

"widow maker"

left anterior descending artery (LAD)

BRANCH OF LCA

lays over interventricular septum

*commonly bypassed

left circumflex artery (LCx)

BRANCH OF LCA

supplies left ventricular wall

right

86% of patients have ___________ dominant coronary system.

coronary sinus

receives blood from most coronary veins and delivers to R atrium

tunica externa

outer layer of a blood vessel which connects it to surrounding tissues

*collagenous, fibrous tissue with own nerves and blood vessels

**STRUCTURAL SUPPORT

tunica media

middle and thickest layer of tissue of a blood vessel wall

*smooth muscle (contractile)

**elastic tissue

vasoconstriction/dilation by mechanical, chemical, or neurological stimulus

tunica intima

the innermost layer of a blood vessel

*endothelial cells

**smooth mm.

***LDL permeable

cholesterol lab guidelines

REFER TO IMAGE