cardiovascular system - anatomy of the heart Flashcards by ellie lo

amphibians

3-chambered heart
-both atria expel blood into single ventricle
-oxy.blood and deoxy.blood mixed together
-cold blooded

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reptiles

3-chambered heart (septated)
-partially separated ventricle
-still some mixing between oxy.blood and deoxy.blood

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birds + mammals

4-chambered heart
-separate heart pumps
-left side = oxy.blood (under HIGH pressure = higher metabolic rate)
-right side = deoxy.blood (under lower pressure = facilitates good gaseous exchange, esp. in lungs)

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human circulation

two-sided pump
-left: blood pumped at high pressure to body (systemic circulation)
-right: deoxy.blood to lungs (pulmonary circulation)

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position of the heart (in thoracic cavity)

-sits central/middle
-lung on either side
-surrounding heart is the pericardial sac

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importance of pericardial sac

-filled with pericardial fluid which prevents heart from being compressed
-allows freedom of movement (heart able to freely contract/relax and move)

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pericardium protects the heart

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heart has three layers

-endothelium
-myocardium
-epicardium

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endothelium

-inner layer
-consists of chain of endothelial cells lining the heart chambers
-makes contact with blood
-forms barrier with rest of tissue

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myocardium

-middle layer
-consists of myocytes
-contractile elements of the heart in this region (muscle of heart)

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epicardium

-outer layer
-visceral layer of serous pericardium
-in contact with pericardial sac/structures surrounding pericardium

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fibrous pericardium

-stiffest part of structure
-prevents pericardium from being overly stretched

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typical human heart

-approx. length: 6 inches
-approx. mass: 300g
-approx. stroke vol.: 70ml
-approx. 38 mil beats/year

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stroke volume

volume of blood pumped out of the left ventricle during each systolic cardiac contraction (each beat)

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cardiac output (CO)

volume of blood pumped out in one minute

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how is CO calculated ?

CO = HR x SV

-CO: cardiac output (ml/min)
-HR: heart rate (beats/min)
-SV: stroke vol. (ml/beat)

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heart rate (HR)

number of heart beats per minute

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cardiac reserve

difference between RESTING and MAXIMAL cardiac output

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interventricular septum

-separates the two ventricles
-helps blood flow in correct directions
-has role in electrical conduction
-similar thickness to L.ventricle
-tends to pump as part of L.ventricle

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RIGHT ventricle thickness

-thinner wall
-blood pumped at lower pressure to lungs (pulmonary circulation)
-lower pressure so as to not damage delicate vessels in pulmonary system

LEFT ventricle thickness

-thicker wall
-blood pumped at high pressure to body (systemic circulation)

atria thickness

-thin
-ventricular filling is done by gravity
-therefore requiring little atrial effort

significance of systolic pressure

-approx. 100 mmHg in human
-approx. 250 mmHg in giraffe
-higher systolic pressure as gravity must be overcome to pump blood to head (giraffe much taller than human)

muscle fibre arrangement around heart

when contracting muscle fibres SHORTEN but also TWIST (wring) in order to empty chambers of blood

metabolic activity of heart

-about 5% of all the blood that is pumped out of the heart goes to the heart -dense supply of vessels to maintain oxygen (+nutrients) demand

left coronary artery

arises from left side of aorta and splits into two branches: -circumflex -left anterior descending (LAD)

right coronary artery

emerges from right side of aorta

different vessels perfuse different areas of the heart, but there is overlap

-left side perfuses left side of heart mostly but also perfuses some of right and vice versa -

importance of vessel perfusion (arterial + venular) across the heart ?

allows protection from blockages that can occur

atrioventricular valves

-bicuspid/mitral (L.atrium from L.ventricle) -tricuspid (R.atrium from R.ventricle) =maintains unidirectional flow

pulmonary (pulmonic) valve

-right ventricle to pulmonary trunk -when blood is pumped towards the lungs, it stays out and does not come back in

tricuspid valve

right atrium to right ventricle

bicuspid (mitral) valve

left atrium to left ventricle

aortic valve

left ventricle to aorta

valve damage

significantly reduces cardiac output and result in heart failure due to reducing the hearts efficiency

what are valves made up of ?

fibrous connective tissue

valve leaflets

connected to papillary muscles

papillary muscles

contain myocytes (part of ventricular wall)

electrical activity of the heart

-passes through ventricular wall and papillary muscles -pap.muscle SHORTEN -as they shorten, they pull down on the valve leaflets -this stops the valve leaflets from turning inside out

significance of valve leaflets being connected to pap.muscle

-are not made of actively contractile tissue -but connected to pap.muscle (that respond to the contractile cycle) -they are able to CONTRACT+RELAX -valves can OPEN+CLOSE at the right time

example of atrioventricular (AV) valves

-blood from atria to ventricles -pressure develops in ventricles -valves close -stops blood from flowing back into atria -allows blood to leave aorta in pulmonary artery

example of semi-lunar (SL) valves

-once ventricles contract, blood goes to aorta on the left side (aortic arch) -blood pumped INTO the aorta -SL valves slam SHUT to prevent blood returning to ventricular chamber

how are heart valves connected to papillary muscles ?

via tendinous strings (chordae tendinae)

role of papillary muscle

contracts during SYSTOLE thus preventing valves from inverting

heart sounds (S1)

closing of AV valves at the START of ventricular systole

heart sounds (S2)

closing of the SL valves at the END of ventricular systole

heart sounds (S3)

(inaudible) blood at the opening of AV valves during diastole

heart sounds (S4)

(inaudible) atrial contraction

heart sounds

-usually only S1 and S2 are audible -if there is an issue with the heart then S3 and S4 may also be audible