chap 20: the heart

What is the heart?

The heart is a muscular pump to move the blood through the vessels

Where do arteries carry blood?

AWAY from the heart

Where do veins carry blood?

back TOWARD the heart

What are capillaries?

microscopic vessels connecting the smallest arteries and veins

What are the two divisons of the cardiovascular system?

pulmonary and systemic circuit

What is the pulmonary circuit

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

What is the systemic circuit

supplies blood to every organ of the body, including other parts of the lungs and the wall of the heart itself

what is the pulmonary circuit supplied by

right half of the heart

What blood does the heart recieve from the body and where does it pump it too?

Heart receives deoxygenated blood from body, pumps it to lungs

What is the systemic circuit supplied by

left side of the heart

What type of blood does the heart recieve from the lungs

Heart receives oxygenated blood from lungs, pumps it to body

What does the aorta carry

freshly oxygenate blood leaving the left ventricle to be distributed throughout the body

What are the 3 regions of the aorta

ascending aorta, aortic arch, descending aorta

What does the pulmonary trunk carry

carries deoxygenated blood leaving the right ventricle to be carried to the lungs, it quickly branches into right and left pulmonary arteries to the respective lungs

What are the veins of the heart

pulmonary veins, superior vena cava, inferior vena cava

What do the pulmonary veins return

return freshly oxygenated blood from the lungs to the left atrium, with two of these emptying into the atrium from each side

What does the superior vena cava carry

deoxygenate blood to the heart from the head, upper limbs, and all other regions above the diaphragm

Where does the superior venca cava empty

into the right atrium

what does the inferior vena cava carry

carries deoxygenated blood to the heart from body regions below the diaphragm

where does the inferior vena cava empty

into the right atrium from below

what are the 3 layers of the heart wall from outermost to innermost

epicardium, myocardium, endocardium

what is the epicardium of the heart wall

(visceral layer of serous pericardium)—thin membrane of

simple squamous epithelium overlying elastic connective tissue

What is the myocardium

composed of cardiac muscle; most of the mass of the heart.

What does the myocardium perform

performs the work of the heart & its thickness varies with the workload of the individual chamber.

what is the vortex of the heart?

Cardiac muscle cells (cardiomyocytes) grouped in bundles that coil around heart in a spiral

What does the vortex of the heart cause?

causes heart to contract with a twisting, wringing motion, enhances the ejection of blood.

what is the endocardium

inner lining of heart chambers and covers valves;

simple squamous epithelium and thin layer of connective tissue.

Describe the anatomy of the atria chambers

• Thin, flaccid walls

• Atria separated by interatrial septum

• Right atrium and both auricles contain ridges of pectinate muscles

Describe the anatomy of the ventricle chambers

•Left ventricle wall much thicker than right; reflects workload. It is 4X as thick as it pumps blood through out the entire body

• Ventricles separated by interventricular septum

• Both have trabeculae carneae—internal ridges

• Volume of both ventricle about the same

What is the left ventricle wall much thicker than the right ventricle wall?

reflects workload, it is 2-4X as thick as it pumps blood through out the entire body

What do heart valves ensure?

one-way flow of blood through heart

What do heart valves consist of ?

two or three cusps or leaflets covered with endocardium

What are Atrioventricular (AV) valves?

between atria and ventricles

What is the Right AV Valve

three cusps, so also called tricuspid valve

What is the left AV valve

also called the mitral valve or bicuspid valve

What ate valve cusps anchored to and by what?

anchored to papillary muscles by tendinous cords (chordae tendinae)

What happens when tendinous cords that anchor valve cusps start to slack?

excessive bulging (valvular prolapse) will occur.

What are semilunar valves (SV)

between ventricles and great arteries

Give specific locations of SV valves

aorta, pulmonary trunk-bld vessels leading to the lungs

What are the two SV valves

aortic and pulmonary

Where is the pulmonary valve

between right ventricle and pulmonary trunk

where is the aortic valve

between left ventricle and aorta

** know blood flow through the heart

T/f: Coronary circulation is critical

True

What happens when blockage occurs in a coronary artery

this can produce a myocardial infarction (MI)

What is a myocardial infarction(MI)

sudden death of cardiac tissue

Where do the LCA and RCA emerge from?

the base of the ascending aorta (proximal end of aorta).

Where does the left coronary artery (LCA) travel?

through coronary sulcus, under left auricle and divides into two branches

What are the two branches of the LCA?

anterior interventricular branch and circumflex branch

Where does the anterior interventricular branch of the LCA pass?

passes down anterior interventricular sulcus, joins posterior interventricular branch.

What is the anterior interventricular branch called clinically?

left anterior descending branch

What does the anterior inter ventricular branch do?

This artery supplies blood to both ventricles and the anterior two-thirds of the interventricular septum.

What occurs with a blockage to the anterior interventricular branch

A blockage here would cause massive damage or death hence it is called the widow maker.

What does the circumflex branch do in the LCA

contuses around left side of heart; gives off left marginal branch

Where does the right coronary artery RCA travel?

travels along coronary sulcus under right article and divides into two branches

What two branches does the RCA divide into

right marginal branch and posterior interventricular branch

Where is the right marginal branch?

along right margin of heart

Where is the posterior interventricular branch

along posterior interventricular sulcus

** know the cardiac conduction system

what is the cardiac cycle

one complete cycle of contraction and relaxation of the

heart

what is cardiomyocytes electrically charged

electrically polarized (negative on the inside)

Excitation leads too….

depolarizes (less negative on the inside, as Na+ enters the cells) the cells and cause their contraction; after contraction, the cells repolarize (K+ leaves the cell returning it to more neg on inside) and relax

Define systole

contraction of a heart chamber

Define diastole

relaxation of a heart chamber

What measures electrical activity of the heart

electrocardiogram (ECG or EKG)

What are the major events of ECG

P wave, QRS complex, T wave

What is p-wave?

atrial depolarization

What is QRS complex?

ventricular depolarization

What is t-wave?

ventricular repolarization

What occurs in the cardiac cycle initially?

all four chambers are relaxed; AV valves are open and blood flows from atria to ventricles

What occurs when SA nodes fire?

produces P wave of ECG as atria depolarize; atria contract (atrial systole) to finish filling the ventricles; signal delayed at AV node

Where does the signal delayed at AV node go?

Signal spreads down rest of conduction system, depolarizes ventricles, which produces QRS complex; ventricles contract and AV valves close—first heart sound (S1); blood is ejected

What produces the first heart sound (S1)?

AV valves closing

What happens when ventricles repolarize and relax?

Ventricles repolarize and relax (ventricular diastole), which produces T wave; blood tries to flow backward and closes semilunar valves—second heart sound (S2)

What causes the second heart sound?

SV valves close

How does the cycle start over?

Ventricles begin refilling again and cycle starts over

Why does the heart develop early in the embryo?

so it can distribute nutrients and oxygen

When does the heart start beating?

22-23 days (week 3)

What occurs in week 3 of the embryo?

mesoderm condenses to form cords that hollow out to form parallel endocardial heart tubes

What are the dilated spaces formed from tubes fusing in the embryo?

runcus arteriosus, bulbus cordis (becomes R. atrium), ventricle, atrium, and sinus venosus

What shape does the heart form and how? What else is present?

Heart loops and then forms S shape; primordial atrium and ventricles present

What is the opening between atria?

foramen ovale

What does the foramen ovale allow?

allows the blood to bypass the lungs, goes from right atrium to left atrium.

What allows the most blood to bypass pulmonary circuit in the fetal heart?

foramen ovale and ductus arteriosus

What is caused by lungs inflating at birth?

their resistance to blood flow decreases

A drop in resistance to blood flow causes?

causes tissue flap to seal foramen ovale, becomes a depression—the fossa ovalis

What occurs several hours after birth with the ductus arteriosus?

ductus arteriosus begins to close, fully closed in 2–4 days; remnant is ligamentum arteriosum

What is a ductus arteriosus

a shunt from the base of the left pulmonary artery to the aorta

The ductus arteriosus closes fully in how many days?

2-4 days

What is patent ductus arteriosus?

failure of the ductus arteriosus to close

What does Patent Ductus Arteriosus lead too overtime?

as the lungs become inflated and more functional, pulmonary blood pressure drops below aortic blood pressure. Blood may then begin to flow from the aortic arch back into the pulmonary circuit for an immediate second trip through the lungs. Since this blood returns to the left ventricle, it adds markedly to the left ventricular workload. The lungs sometimes respond to the persistent high blood flower with vascular changes that increase pulmonary resistance and stress the right ventricle as well.

What are some signs of PDA?

poor weight gain, frequent respiratory illnesses, dyspnea, cardiomegaly

When is PDA usually suspected

about 6-8 weeks of age because of persistent “machinery-like” murmur.

What is PDA confirmed by

echocardiogram

** know the diseases