Cardiovascular System

Functions of Cardiovascular System

1. generate blood pressure2. send oxygenated blood to organs3. insure one-way blood flow4. regulate blood supply

The HeartO muscular organO pumps blood through body with

forceful contractionsO pumps approximately 5 liters per

minuteO enclosed in pericardium

O contains pericardial fluid to reduce friction

Layers of the Heart Wall

O epicardium – serous membrane forming the outer surface of the heartO simple squamous epithelium over loose

connective tissue and fatO myocardium - thick

O cardiac muscleO contracts heart

O endocardium – inner surface of chambersO simple squamous epithelium over connective

tissueO allows blood to flow easily through heartO forms valves

The HeartO right and left atria – where blood

entersO right and left ventricles – where it

exitsO vessels that move blood in/out of

heartO superior vena cavaO inferior vena cavaO pulmonary veinsO pulmonary trunk/arteriesO aorta

AtriaO receive bloodO send blood to ventriclesO Right atrium has 3 inputs.

1. superior vena cava (low O2)

2. inferior vena cava (low O2)

3. coronary sinus (low O2)

O Left receives blood from 4 pulmonary veins. (high O2)

VentriclesO pumping chambersO eject blood into circulatory systemO have 1 outflow eachO Right ventricle sends blood through

pulmonary trunk/arteries to lungs.O Left ventricle sends blood through

aorta to rest of the body.O thick wall; generates high blood

pressure

ValvesO prevent back flow of blood1. tricuspid valve

O between right atrium and right ventricle

2. bicuspid (mitral) valveO between left atrium and left ventricle

O Papillary muscles attach to chordae tendinae which attach to cusps.

O open when ventricles relaxO closed when ventricles contract

Valves3. semilunar valves

O 3 pocket-like cuspsO aortic semilunar

O between left ventricle and aortaO pulmonary semilunar

O between right ventricle and pulmonary trunk

O When ventricles contract, blood is forced through valve. When ventricles relax, valves close.

Blood flow through body

O beating heartO superior and inferior vena cava, right atrium,

tricuspid valve, right ventricle, pulmonary semilunar valve, pulmonary semilunar valve, pulmonary trunk, pulmonary arteries, lungs, pulmonary veins, left atrium, bicuspid valve, left ventricle, aortic semilunar valve, aorta, brachiocephalic artery, left common carotid artery, left subclavian artery, abdominal aorta, arteries, arterioles, capillaries, venules, veins

Heart BeatingO coordinated heart

beatO controlled by

electrical impulsesO SA (sinoatrial) node

O pacemaker of the heart

O located on superior wall of right atrium

O initiates contractions

Heart BeatingO AV (atrioventricular) node

O lower right atriumO slower moving electrical impulses

video

Blood flow to the heartO coronary arteries

O originate from base of aortaO supply blood to heart wall1. left coronary artery2. right coronary artery

O cardiac veinsO parallel to arteriesO drain blood into coronary sinus

(large vein) then to right atrium

Cardiac CycleO repetitive pumping process

O start: cardiac muscle contractionO end: just before next contraction

O changes in pressure due to muscle contraction

O systole – contraction of ventricles “lub”O pushes blood through atria; valve closes

O pressure forces open semilunar valves

Cardiac CycleO diastole: relaxation of ventricles

“dup”O decreased pressure in ventriclesO Semilunar valves close.O lower pressure – tricuspid and

bicuspid openO Blood flows from atria to ventricles

and fills about 70%.O Atrial contraction completes filling.

Cardiac OutputO volume of blood pumped by either

ventricle of heart each minuteO cardiac output = stroke volume(SV) x

heart rate (HR)O HR – beats per minuteO SV – volume of blood pumped per

ventricle each time heart contracts (mL/min)

O CO must be continually adjusted to meet needs of the body.

Heart ConductionO electrical impulses carried by Ca+2,

K+, and Na+

O constant concentrationsO increased extracellular K+, decrease

HR and SVO even higher K+, blocks conduction

O increased extracellular Ca+2, arrhythmia

O decreased extracellular Ca+2, decrease HR and SV

ECG/EKGO recording deviceO electrodes placed on body surface O P wave

O depolarization of atrial myocardiumO followed by atrial contraction

O QRS complexO depolarization of ventriclesO followed by ventricular contraction

O T waveO repolarization of ventriclesO followed by ventricular relaxation