functional anatomy

Question 1

what are the three main layers the heart wall is made of

Answer 1

• endocardium
• myocardium
• epicardium

Question 2

endocardium

Answer 2

• endothelial inner layer

- similar to lining of blood vessels

Question 3

myocardium

Answer 3

• makes up bulk of the heart

- cardiac muscle (specialised)

Question 4

epicardium

Answer 4

• around the heart
  : visceral - covering of an organ
  : parietal - next to the cavity

Question 5

role of the pericardium

Answer 5

• protects and anchors the heart
• prevents overfilling of heart
• provides a friction free environment

Question 6

what is pericardial effusion

Answer 6

• 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

Question 7

what blood vessels are involved in returning blood to the heart

Answer 7

• superior and inferior vena cava

- right and left pulmonary veins (bring blood from lungs)

Question 8

what blood vessels are involved in transporting blood away from the heart

Answer 8

• pulmonary trunk split into left and right pulmonary arteries
• ascending aorta (delivers oxygenated blood to body)

Question 9

what is the cardiac cycle

Answer 9

• 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

Question 10

what are the phases of cardiac cycle 1

Answer 10

• blood enters atria into ventricles
• atria contracts
• AV open to allow blood to enter

Question 11

cardiac cycle 11

Answer 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

Question 12

what is the thickness of the heart muscle dependent on

Answer 12

• on what work it has to do and its function

- left ventricle thickness to supply oxygenated blood to whole body - high pressure - strong contraction

Question 13

purpose of heart valves

Answer 13

• prevent back flow of blood

Question 14

what is cordae tendinae

Answer 14

• 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

Question 15

where are av valves found

Answer 15

• 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

Question 16

where are semi lunar valves located

Answer 16

• between pulmonary artery and aorta
• prevents back flow into ventricles
• high pressure in arteries compared to ventricles forces them shut

Question 17

why can splitting of heart sounds be important

Answer 17

• can be used diagnostically to identify heart abnormailites

Question 18

how are cardiac muscle cells attached

Answer 18

• cells are joined together by intercalated discs which anchor cardiac cells together
• gap junction allows rapid transfer of ions
• involuntary, short, fat, branched

Question 19

adaptions of cardiac muscle cells

Answer 19

• fatigue resistant (lots of mitochondria, good blood supply, oxygen containing myoglobin)

Question 20

how is an action potential generated

Answer 20

• by a change in the potential difference between the inside and the outside of the cell

Question 21

action potential at the SA node

Answer 21

• 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

Question 22

action potential in contractile cells

Answer 22

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

Question 23

why are ions important

Answer 23

• heart activity is dependent on movement of ions

- important to control conc of ions inside and out of the cell

Question 24

how are the SAN and AV joined in intrinsic conduction

Answer 24

• intermodal pathways
• surrounded by fibrous tissue
• so that signals generated within the cell are not spread to tissues immediately

Question 25

what is the sequence of excitation

Answer 25

• delay between the SAN and AV node
• atria contract before ventricles
• purkinje fibres send signals to bottom of ventricles

Question 26

why do some people need artificial pacemakers

Answer 26

• 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

Question 27

3 steps to cardiac tissue contraction

Answer 27

• 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