functional anatomy Flashcards
what are the three main layers the heart wall is made of
- endocardium
- myocardium
- epicardium
endocardium
- endothelial inner layer
- similar to lining of blood vessels
myocardium
- makes up bulk of the heart
- cardiac muscle (specialised)
epicardium
- around the heart
: visceral - covering of an organ
: parietal - next to the cavity
role of the pericardium
- protects and anchors the heart
- prevents overfilling of heart
- provides a friction free environment
what is pericardial effusion
- when excess fluid/blood in the pericardial cavity
- if volume big enough chambers of heart compressed
- prevents complete filling and reduces cardiac output
- causes inc. trauma and cancer
what blood vessels are involved in returning blood to the heart
- superior and inferior vena cava
- right and left pulmonary veins (bring blood from lungs)
what blood vessels are involved in transporting blood away from the heart
- pulmonary trunk split into left and right pulmonary arteries
- ascending aorta (delivers oxygenated blood to body)
what is the cardiac cycle
- all the events that occur in one heart beat
- heart is either relaxing (diastole) or contracting (systole)
- it is important to control contraction to ensure proper pumping
- atrial contraction must be before ventricular contraction
what are the phases of cardiac cycle 1
- blood enters atria into ventricles
- atria contracts
- AV open to allow blood to enter
cardiac cycle 11
- atria relax, the increase in pressure closes av valves
- ventricles contract
- the semi lunar valves open
- prevents back flow of blood back into ventricles
what is the thickness of the heart muscle dependent on
- on what work it has to do and its function
- left ventricle thickness to supply oxygenated blood to whole body - high pressure - strong contraction
purpose of heart valves
- prevent back flow of blood
what is cordae tendinae
- attached to the small capillary muscles to ventricle
- prevents valve from opening wrong way
- they anchor valves to papillary muscles which contract to prevent inversion
where are av valves found
- between atria and ventricles
- bicuspid valve (mitral) on left and tricuspid on the right
- tricuspid valve on low pressure side of heart meaning less resistance is needed
- bicuspid on high pressure meaning more room of attachment of codae tendinae
- bicuspid has two flaps
where are semi lunar valves located
- between pulmonary artery and aorta
- prevents back flow into ventricles
- high pressure in arteries compared to ventricles forces them shut
why can splitting of heart sounds be important
- can be used diagnostically to identify heart abnormailites
how are cardiac muscle cells attached
- cells are joined together by intercalated discs which anchor cardiac cells together
- gap junction allows rapid transfer of ions
- involuntary, short, fat, branched
adaptions of cardiac muscle cells
- fatigue resistant (lots of mitochondria, good blood supply, oxygen containing myoglobin)
how is an action potential generated
- by a change in the potential difference between the inside and the outside of the cell
action potential at the SA node
- inside of cell more negative than outside of cell
- at SAN there isn’t a stable resting potential
- due to influx of Na+ ions this causes voltage gated channels to open
- leads to depolarisation (inside of cell more positive)
- potassium channels open K+ ions leave meaning charge becomes more negative
- leads to repolarisation
action potential in contractile cells
have a stable resting potential
- rapid depolarisation due to influx of sodium ions
- calcium channels open slowly and potassium channel open
- calcium enter, potassium leave
- closing of calcium channels
- depolarisation
in refractory period contractions cannot occur
why are ions important
- heart activity is dependent on movement of ions
- important to control conc of ions inside and out of the cell
how are the SAN and AV joined in intrinsic conduction
- intermodal pathways
- surrounded by fibrous tissue
- so that signals generated within the cell are not spread to tissues immediately
what is the sequence of excitation
- delay between the SAN and AV node
- atria contract before ventricles
- purkinje fibres send signals to bottom of ventricles
why do some people need artificial pacemakers
- electric signals to the heart can be disrupted
- leading to heart blocks or arrhythmias
- so an implantable device which generates electric signals directly to the heart
3 steps to cardiac tissue contraction
- action potential stimulates calcium influx from outside of cells
- stimulates a further release of calcium intracellular stores
- ca2+ binds to tropmins allowing actin and myosin filaments to contract
