Cardiovascular System

Heart and Blood Vessels

Heart : Facts● Pumps 7,000 liters of blood daily.● Beats some 3 billion times in an average

lifetime● heart size varies with body size

● Avg adult: 14 cm long and 9 cm wide-closed fist

● located in the mediastinum of the thorax and rests on diaphragm● base is beneath 2nd rib, apex at 5th

rib, slightly to the left

Cardiovascular System

Heart● Coverings and Walls

● Pericardium: double-walled sac that encloses the heart● reduces friction of beating heart

● Epicardium: outer layer of the wall of the heart, protective covering, secretes serous fluid

Heart● Coverings and Walls

● Pericardium: double-walled sac that encloses the heart● Outer layer: fibrous pericardium● Inner layer: parietal pericardium contacts

fibrous pericardium and visceral pericardium covers the heart● between parietal and visceral layers is

serous fluid-reduces friction of beating heart

Heart● Coverings and Walls

● Myocardium: middle layer of wall, cardiac muscle tissue, contracts to pump blood

● Endocardium: thin inner layer, protective lining of heart chambers and valves

● Septum: portion of myocardium that separates the right and left ventricles.

Teach It! ● Partner 1:

● Explain to your shoulder partner how the heart is protected in the chest; the structure of the Pericardium. -25 seconds

● Partner 2: ● Restate what your partner just explained.-15 sec

● Partner 2:● Name and describe to your partner the different layers of

the wall of the heart. -25 seconds● Partner 1:

● Restate what your partner just explained. -15 sec

Heart● Chambers and Valves

● Right Side: receives oxygen-poor blood from the body● Superior and Inferior Vena Cava: main veins

that deliver blood to the heart from the upper and lower body

● Right Atrium: receives the blood from the body● Tricuspid valve prevents backflow of blood back into

rt ventricle● Right Ventricle: receives blood from rt atrium and

pumps blood to lungs via Pulmonary arteries

Heart● Chambers and Valves● Right Side:

● Pulmonary semilunar valves prevent backflow of blood into rt ventricle from pulmonary arteries

● Left Side: receives oxygen-rich blood from the lungs● Left Atrium: receives blood from the lungs via

Pulmonary Veins● Bicuspid or Mitral valve: prevents backflow

from left ventricle

Heart● Chambers and Valves

● Left Side● Left Ventricle: strongest and thickest

myocardium, receives blood from left atrium and pumps blood to the entire body via aorta

● Aortic semilunar valve: prevents backflow into left ventricle

● Aorta: main artery from which arteries branch to supply blood to all body tissues

Heart● Pathway: the flow of blood

● Superior and Inferior Vena Cava● Right Atrium

● Tricuspid valve● Right Ventricle

● Pulmonary semilunar valve● Pulmonary arteries● Lungs● Pulmonary veins● Left Atrium

● Bicuspid or Mitral valve● Left Ventricle

● Aortic semilunar valve● Aorta● Body tissues

Heart● Pulmonary Circulation:

● circulation of blood from the right side of the heart to the lungs and back to the left atrium.

● only function is to carry blood to the lungs for gas exchange and then return it to the heart.

● Systemic Circulation:● circulation from the left side of the heart through the

body tissues and back to the right atrium● supplies oxygen and nutrient-rich blood to all body

organs

Heart● Cardiac Circulation:

● Right and Left Coronary Arteries provides the myocardium with oxygen and nutrients

● Cardiac Veins returns oxygen-poor blood back to the right atrium

Heart● Did You Get It?

● Discuss with partners and write your answer on whiteboard

1. Which chamber has the thickest walls? Why would that be?

2. How does the function of the systemic circulation differ from that of the pulmonary circulation?

3. Why are heart valves important?4. Why might a thrombus (blood clot) in a coronary artery

cause sudden death?

Heart : Physiology●

Heart : Physiology● Cardiac muscle is able to initiate its own contraction,

but the rate is influenced by both intrinsic and extrinsic factors.

● Intrinsic conduction system or nodal system is built into the heart tissue● sets the basic rhythm● composed of special tissues● travels in one direction-from atria to the ventricles

Heart : Physiology● Components of intrinsic conduction system

● sinoatrial node or SA node● located in right atrium● “the pacemaker”● starts the heartbeat and sets the pace

● atrioventricular node or AV node● located at junction of atria and ventricles

● Purkinje fibers● spread within the muscle of ventricle walls

Heart : PhysiologyImpulse● The atria contract simultaneously - as they start to relax -

contractions of ventricles begins● SA node starts the impulse● Atria contracts● Spreads thru the atria to the AV node

● brief pause to allow atria to finish contracting● passes rapidly thru Purkinje fibers

● Ventricles contract starting at apex moving up towards atria

Heart : PhysiologyImpulse●

SA

AV

purkinje fibers

21

3

4

5

1. SA node begins signal

2. Signal flows from right to left atria. Atria contract

3. Signal reaches AV node

4. AV node sends signal down septum via bundle branches

5. Signal reaches apex and flows through Purkinje fibers and Ventricles contract

Heart : Physiology● Cardiac Cycle and Heart Sounds

● Systole (LUB) - contraction of the ventricles-AV valves closed● Diastole (DUB)- relaxation of the ventricles-SL valves closed● The time and events occurring from one heartbeat to the next are the

cardiac cycle● 3 periods of cardiac cycle

● Mid-to-late diastole● complete relaxation of ventricles, pressure in heart is low,

blood flowing passively into and thru atria to ventricles from pulmonary and systemic circulations, Semilunar valves are closed and AV valves are open, Atria contract and force remaining blood into ventricles

Heart : Physiology● Cardiac Cycle and Heart Sounds

● 3 periods of cardiac cycle● Ventricular systole

● pressure within ventricles increases, bicuspid/tricuspid valves close, Semilunar valves open, Ventricles contract, blood rushes out, atria are relaxed and blood enters

● Early diastole● ventricles relax, semilunar valves close, pressure changes in

ventricles, bicuspid/tricuspid valves open, ventricles begin to fill up again

● Cardiac output is the amount of blood pumped out by each ventricle in 1 minute

● Stroke volume is the amount of blood pumped out by each ventricle with each heartbeat, - increases as force of contractions increases

Cardiac Cycle Review

Systole:Heart Pressure:Ventricles:Blood flow:AV valves:SL valves:Atria:

Heart Pressure:Ventricles:Blood flow:AV valves:SL valves:Atria:

Diastole:

Heart : Physiology● Cardiac Cycle and Heart Sounds

● Abnormal Sounds● Heart murmurs

● blood flow is not smooth and uninterrupted● valve problems-doesn’t close tightly so some

blood flows backwards

blood vessels● Arteries and Arterioles● carries oxygen-rich blood away from the heart

● pulmonary arteries carry oxygen-poor blood from heart● thick walls, strong and stretchy● blood moves thru as result of the pressure from heartbeats● Major arteries

● Aorta● Carotid● Brachiocephalic -> Subclavian● Coronary● Femoral

blood vessels● Veins and Venules

● carries oxygen-poor blood towards the heart● pulmonary veins carry oxygen-rich blood from lungs to the heart

● thinner walls, wider diameter, contains valves to prevent backflow● skeletal muscles help move blood to the heart● Major veins

● Superior and Inferior Vena Cava● Jugular vein● Brachiocephalic -> Subclavian● Femoral● Cardiac veins

blood vessels● Capillaries and Capillary beds

● one cell layer thick● site of gas exchange● form interweaving networks

blood vessels● PHYSIOLOGY OF CIRCULATION

● Arterial Pulse: the pressure wave of blood that travels through the entire arterial system● pressure surges per minute● Avg resting-70-76 beats per minute

● Blood Pressure: the pressure the blood exerts against the inner walls of the blood vessels● the force that keeps blood circulating● Systolic Pressure: pressure in arteries at the peak of ventricular

contraction, 1st number of BP● Diastolic Pressure: pressure when ventricles are relaxing, 2nd

number of BP● normal range: 110-140/70-80 mm Hg

blood vessels● PHYSIOLOGY OF CIRCULATION

● Hypertension: high blood pressure● heart pumps against increased resistance● 140/90 or higher● strains the heart and damages the arteries

● Arteriosclerosis● clogging of the arteries by thickening of the interior

artery walls

blood vessels● PHYSIOLOGY OF CIRCULATION

● Effects● Arterial BP is directly related to Cardiac Output and Peripheral

resistance BP=CO x PR● Peripheral resistance: amount of friction blood encounters as it

flows● narrowing of blood vessels due to sympathetic nervous

system● vasoconstriction: hemorrhaging, exercising

● the kidneys● regulate water retention/loss from plasma● increase BP, kidneys allows water to leave which

decreases blood volume and BP

blood vessels● PHYSIOLOGY OF CIRCULATION

● Effects● Peripheral resistance:

● temperature● cold-vasoconstriction/heat-vasodilation

● Chemicals● Epinephrine increases heart rate and BP● Nicotine increases BP by vasoconstriction● Alcohol decreases BP by vasodilation

● Diet● low in salt, saturated fats, and cholesterol prevents high BP

● Exercise● if heart can work less to pump, the force on arteries decrease

blood vessels● PHYSIOLOGY OF CIRCULATION