Ch 18--The Heart

the Heart

keeps blood flowing, drives blood through the body, spplies tissues with nutrients and oxygen, allows excrement of metabolic wastes

approx the size of a fist

in the thoracic cavity

attached superiorly to the disphragm, anterior to the vertebral column, posterior to the sternum; flanked laterally by the lungs

what side of the heart receives from what system

right side receive from the systematic circuit and pumps blood to the lungs

left side receives from the lungs and pumps blood back through the systemic circuit

the four chambers of the heart

Right Atrium—receives deoxygenated blood from systemic
Left Atrium—receives oxygenated blood from pulmonary
Right Ventricle—pumps blood through pulmonary trunk (into lungs)
Left Ventricle—pumps blood through aorta (and the rest of the body)

pericardium

sac that surrounds the heart, made of external/fibrous layer and internal/serous layers

fibrous layer

anchors the heart

serous layer

two parts:

parietal pericardium is under the fibrous layer and surrounds the cvity

visceral pericardium is on the external heart

pericardial cavity

between the fibrous and serous layers

filled with serous fluid

layers of the heart wall

epicardium, myocardium, endocardium

epicardium

superficial to visceral layer of the pericardium

myocardium

middle layer, muscle tissue, conracts to “pumo” forms rings for compression

endocardium

inner layer, lines the chambers with endothelial tissue

atria

contribute little to flow of blood

receiving chambers

interatrial septum

separates atriums

interventricular septum

separates ventricles

superior vena cava

returns blood from diaphragm up, not pulmonary

right atrium

inferior vena cava

returns blood from diaphragm down

right atrium

coronary sinus

blood supply for the heart itself

right atrium

left atrium

receives oxygenated blood from the lungs

attach to four pulmonary veins

ventricles

pump blood through systems

trabeculae carnae

extensions or muscle ridges to make the muscle larger to fill with more blood

papillary muscle

attaches to and moves heart strings

chordae tendineae

heart strings

collagen fibers, hold valves closed during systole

heart valves

four—AV valves and Semilunar valves

ensure one-way blood flow through the heart, like a tissue door

atrioventricular (AV) valve

between the atrium and ventricle, heart strings anchor to papillary muscles

tricuspid and mitral

tricuspid

three flaps between right atrium and right ventricle

mitral/bicuspid

two flaps, between left atrium and left ventricle

semilunar valves

between the ventricle and blood vessel it pumps into

moved by pressure changes

pulmonary semilunar valve

between right ventricle and pulmonary trunk

aortic semilunar valve

between left ventricle and aorta

Blood flow through the heart

1. Enters right atrium, then goes through tricuspid valve
2. Enters right ventricle, then goes through pulmonary semilunar valve
3. Enters pulmonary trunk, then goes to the lungs and back to the heart through pulmonarycorono veins
4. Enters left atrium, then goes through mitral/bicuspid valve
5. Enters left ventricle, then goes through aortic semi. valve, then enters aorta and body

coronary circulation

functional supply to the heart muscle itself

shortest circulation in the body, prone to being clogged

first branch off the aorta

left coronary artery

supplied left artium and ventricle

2 main branches: anterior interventricular artery and circumflex artery

anterior interventricular artery

down the front between the ventricles

circumflex artery

goes around and to the back

right coronary artery

supplies blood to the right atrium and ventricle

2 main branches: right marginal artery and posterior interventricular artery

right marginal artery

around the heart

posterior interventricular artery

continues around the back side of the heart

coronary veins

return heart blood

merge into the right atrium

coronary sinus

empties into right atrium

formed from great, middle, and small cardiac veins

intercalated discs

connecting junctions between cardiac cells

contain gap junction that connects cells together and allow electrical activity to flow through the heart

intrinsic conduction system

network of noncontractile cells, initiate and distribute impulses

sinus rhythm

electrical activity or current that makes the heart work and pumps electrolytes around the heart

the sequence of excitation

1. Sinoatrial (SA) node—pacemaker, atria are depolarized
2. Impulses pause at atrioventricular (AV) node
3. The AV connects the atria to the ventricles
4. Bundle branches conduct impulses through interventricular septum
5. Depolarization of both ventricles

sinoatrial node (SA node)

pacemaker, causes depolarization in the atria

atrioventricular node (AV node)

delays impulses approx 0.15 seconds between the end of atrial and the beginning of ventricle contraction

right and left bundle branches

two pathways; carries impulse through the septum to the ventricles

subendocardial conducting network

completes the pathway, follows apex of the heart to the atria and depolarizes ventricles

EKG Features and meanings

P wave: atrial depolarization, made by pacemaker
QRS complex—ventricular depolarization and atrial repolarization
T wave—ventricle repolarization

how does your body change the heart’s rhythm

vagus nerve lowers heart rate

sympathetic cardiac nerves elevate heart rate

cardiac cycle

Phase 1: Ventricular filling—atrial and ventricular diasole
     A. pressure is low, blood passively flows through open AV valves into ventricles
     B. atrial depolarization triggers atrial systole (P wave)
Phase 2: Ventricular systole—atria relaxed, ventricles begin to contract
     A. depolarization spreads to ventricles (QRS complex)
     B. ventricular pressure—AV valves to close, blood ejects into pulmonary trunk/aorta
Phase 3: Heart Relaxation
     A. ventricular repolarization (T waves)
     B. Backflow of blood from aorta and pulmonary trunk closes semilunar valves

systole

contraction of pumping phase of the cycle

disatole

the relaxation, or filling phase of the cycle

heart rate

the number of beats per minute

valve prolapse

a bulging valve, blood leaks back into the atria

electrocardiography

detect electrical currents generated by the heart

electrocardiogram

graphic recording of electrical activity in the heart

arrhythemia

irregular heart rate

bradycardia

slower than normal heart rate

tachycardia

elevated heart rate

fibrillation

uncoordinated contractions

heart block

block of impluses to the ventricles

blood pressure

block of impulses to ventricles

ischemic heart disease

heart issues caused by narrowing of the arteries

myocardial infarction

heart attack, caused by plaque build up due to fat

stroke

blockage of blood to the brain

coronary heart disease

fatty material and other substances, plaque build up and arteries narrow

angina

chest pain caused by reduced blood flow to the heart

valve stenosis

scarred, not flexible valve

doesnt open or close