cardiovascular system - anatomy of the heart Flashcards
amphibians
3-chambered heart
-both atria expel blood into single ventricle
-oxy.blood and deoxy.blood mixed together
-cold blooded
reptiles
3-chambered heart (septated)
-partially separated ventricle
-still some mixing between oxy.blood and deoxy.blood
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)
human circulation
two-sided pump
-left: blood pumped at high pressure to body (systemic circulation)
-right: deoxy.blood to lungs (pulmonary circulation)
position of the heart (in thoracic cavity)
-sits central/middle
-lung on either side
-surrounding heart is the pericardial sac
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)
pericardium protects the heart
heart has three layers
-endothelium
-myocardium
-epicardium
endothelium
-inner layer
-consists of chain of endothelial cells lining the heart chambers
-makes contact with blood
-forms barrier with rest of tissue
myocardium
-middle layer
-consists of myocytes
-contractile elements of the heart in this region (muscle of heart)
epicardium
-outer layer
-visceral layer of serous pericardium
-in contact with pericardial sac/structures surrounding pericardium
fibrous pericardium
-stiffest part of structure
-prevents pericardium from being overly stretched
typical human heart
-approx. length: 6 inches
-approx. mass: 300g
-approx. stroke vol.: 70ml
-approx. 38 mil beats/year
stroke volume
volume of blood pumped out of the left ventricle during each systolic cardiac contraction (each beat)
cardiac output (CO)
volume of blood pumped out in one minute
how is CO calculated ?
CO = HR x SV
-CO: cardiac output (ml/min)
-HR: heart rate (beats/min)
-SV: stroke vol. (ml/beat)
heart rate (HR)
number of heart beats per minute
cardiac reserve
difference between RESTING and MAXIMAL cardiac output
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
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
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
