anatomy of coronary arteries and the heart Flashcards
what are the layers of the pericardium?
fibrous outer layer
serous pericardium- visceral and parietal
what does the fibrous pericardium attach to?
adventitia of the great vessels
central tendon of the diaphragm
what does the parietal pericardium attach to?
fibrous pericardium
what does the visceral pericardium attach to?
the myocardium - heart muscle
what is the pericardial cavity?
the cavity between the parietal and visceral layers
what are the functions of the pericardium?
fixes heart in the mediastinum (anchors it)
protects from infections from other organs
prevents excessive dilation of the heart
lubrication
define pericardial effusion
abnormal accumulation of fluid in the pericardial cavity which can lead to cardiac tamponade
define cardiac tamponade
when fluid causes the compression of the heart
what are the two types of cardiac tamponade?
acute
chronic
what causes acute tamponade?
trauma
e.g. myocardial infarction
what causes chronic tamponade?
metastasis
infection
how is chronic tamponade different from acute tamponade?
chronic - over a longer period of time.
chronic - the heart expands to hold 1.5 litres
acute - can only hold 100ml/150ml
what is the long term effect of cardiac tamponade?
equalises the pressure in all the heart chambers
what does accumulation of fluid under high pressure cause?
compression of all the heart chambers
impairs diastolic filling of both ventricles
affects venous pressure and the stroke volume
how does pericardial effusion affect the right ventricle?
compresses the RV
blood pools in the atrium
JVP is increased
why does pericardial effusion have a bigger effect on the right ventricle than the left?
RV is under lower pressure
RV has thinner walls
how is an increased JVP presented in a person?
engorged veins in the neck
how does pericardial effusion have an effect on the left ventricle?
impairs LV filling
blood backs up to the right ventricle
pulmonary congestion to the lungs
how does pulmonary congestion present in a person?
rales in the lung field
define stroke volume
the volume of blood that’s pumped out of the left ventricle per heartbeat
what is the usual stroke volume at rest?
60-100ml
define cardiac output
the volume of blood pumped out of the heart per minute
what is the equation for cardiac output?
HR x SV
how does pericardial effusion have an effect on stroke volume?
impaired diastolic filling
decreased stroke volume
decreased CO
hypotension
explain the mechanism of reflex tachycardia
increased systolic pressure
baroreceptors in the aorta detect this
increase heart contractions temporarily to increase SV
(reflex tachycardia)
what is pericardiocentesis?
a treatment for cardiac tamponade where the fluid is drained from the pericardial sac
name the three methods of pericardiocentesis
subxiphoid
parasternal
apical
name the layers of the heart
epicardium
myocardium
endocardium
what does the epicardium attach to?
the visceral layer of the serous pericardium
what is the myocardium made of?
cardiac muscle fibres arranged in bundles
where is the endocardium found?
continuous with endothelium
lining chambers and valves
what is another name for the coronary sulcus?
coronary groove
atrioventricular sulcus
what is the coronary sulcus?
the oblique plane which separates the atria and the ventricles
what are the auricles?
extensions/appendages of the atria, allowing more blood to be held
where does the right atrium receive blood from?
vena cava
coronary sinus
what is the coronary sinus?
a collection of veins that join together to form a large vessel which collects blood from the heart muscle
where is the coronary sinus?
posterior surface of the heart in the heart muscle
what is the fossa ovale?
one of the two fetal cardiac shunts which moved blood from the right atrium to the left atrium
when does the fossa ovale close?
at birth
what is the crista terminalis?
the ridge that divides the anterior and posterior wall
what is the sulcus terminalis?
how the crista terminalis is seen externally
what do pectinate muscles do?
reinforce/protect the wall during filling
what is the sinus venarum?
smooth region of the right atrium which receives input from the vena cava and the coronary sinus
how many papillary muscles does the tricuspid valve have?
three
name the papillary muscles of the tricuspid valve
septal
posterior
anterior
what do the papillary muscles do?
anchor the chordeae tendinae
what do chordae tendineae do?
cord like structures which attach onto valves to stop them from inverting into the atrium
what are trabeculae carneae?
rounded or irregular muscular columns which project from the inner surface of the right ventricle
how are trabeculae carneae different from pectinate muscles?
trabeculae carneae are found in the ventricles while pectinate muscles are found in the atria
what do trabeculae carneae do?
help papillary muscles in contraction
prevent cusps from inverting
stop chambers from sucking together
what is another name for the septomarginal trabecula?
moderator band
where is the moderator band?
part of the trabeculae carneae
runs from the septum to the margin of the heart muscle
what is the function of the moderator band?
helps speed of conduction
what does the interventricular septum do?
carries the bundle of His and the AV bundles before they separate into the Purkinje fibres
where does the left atrium receive oxygenated blood from?
pulmonary veins
where are pectinate muscles found in the left atrium?
left auricle
how many pectinate muscles are found in the left atrium?
very few
how many papillary muscles does the mitral valve have?
2
what are aortic sinuses?
dilations in the aorta in the semilunar cusps
name the aortic sinuses
left
right
middle
how does blood leave each of the aortic sinuses?
left and right - leave via coronary arteries
middle - no arteries leaving
where do the left and right coronary artery stem from?
the root of the aorta
what is another name for the left coronary artery?
left main stem
what does the left coronary artery branch into?
circumflex artery
anterior interventricular (LAD)
lateral branches
what is another name for the anterior interventricular arteries?
left anterior descending
what part of the heart does the circumflex artery supply?
the outer side and back of the heart
what part of the heart does the left anterior descending supply?
front of the left side
what part of the heart does the right coronary artery supply blood too?
right ventricle
right atrium
SAN
AVN
what does the right coronary artery branch into?
posterior descending artery
acute marginal artery
how much of the septum is supplied by the LCA?
2/3
`how much of the septum is supplied by the RCA?
1/3
what blood vessel determines the dominance of the heart?
posterior descending artery
what is the most common site of occlusion in a myocardial infarction?
coronary arteries
1 - LCA 40/50%
2 - RCA 30-40%
3 - circumflex 15-20%
how can damage to the coronary arteries damage the conducting system?
LAD to the septal branches supplies the AV bundles
RCA supplies the SAN and AVN
heart block
what are the different views in a coronary angiogram?
left anterior oblique
right anterior oblique
anterior-posterior
where are coronary veins found?
following the course of the arteries
what do coronary veins do?
collects waste from cardiac muscle and drains into coronary sinus
what is the fibrous skeleton of the heart made up of?
dense connective tissue
describe the structure of the fibrous skeleton
4 fibrous rings, with each one surrounding each of the valves
fuse together and merge with the interventricular septum
what is the function of the fibrous skeleton?
supports/anchor the cusps
prevents overstretching of the valves
attachment point for myocardium
electrical insulator between atria and ventricles
when do the AV valves open?
when atrial pressure is greater than ventricular pressure
how do AV valves open?
ventricles relax
chordae tendineae slack
papillary muscles relax
when do AV valves close?
ventricular pressure is higher than atrial pressure
how do AV valves close?
ventricle contract
chordae tendineae pulled taut
papillary muscles contract to pull cords and stop cusps from inverting
how many cusps do the semilunar valves have?
3
how do semi-lunar valves open and close?
by passive action
weight of the blood on the vessels causes them to close
when do semi-lunar valves open and close?
open in ventricular systole
close in ventricular diastole
what causes the first “lub” in the heart noise?
closing of AV valves just before systole
what causes the second “dub” heart noise?
semilunar valves closes before diastole
how do cardiac muscle fibres form atrial and ventricular networks?
via gap junctions at intercalated disks desmosomes
how are impulses transmitted in the atrial network?
cell to cell conduction
how are impulses transmitted in the ventricular network?
fibres in the conducting system,
why are there no gap junctions between the atrial and ventricular networks?
bc they have to function as individual units
what plexus innervates the heart?
cardiac plexus
where is the deep plexus?
anterior to the carina
where is the superficial plexus?
posterior to the aortic arch
what does the cardiac plexus contain?
sympathetic
parasympathetic
general visceral afferents
what are the two centres in the medulla oblongata?
cardionhibitory centre
cardioacceleratory centre
how does the vagus slow down the heart rate?
ACh makes heart cells more permeable
K+ moves in
Hyperpolarisation
Decreases heart rate and force of contraction
where are preganglionic sympathetic neurons found?
thoracic spinal cord
where are postganglionic sympathetic neurons found?
innervating the SAN and AVN and to the coronary vascular smooth muscle
how is cardiac referred pain felt?
stimulates visceral sensory nerve endings in the myocardium
ascend to CNS through cardiac branches of sympathetic trunk
organ and skin pain fibres go to the spinal cord together
pain isnt felt in the heart but is referred as though it came from somatic areas
