Lecture 5- Anatomy of the heart part 2

Question 1

How many valves are there is each pump?

Answer 1

2

Question 2

What are the two general names of the valves on both the right and left side and where are they located?

Answer 2

• Atrioventricular (AV) valve separate the atrium and ventricle.
• Semilunar valve separates the ventricle and the outflow artery

Question 3

What is the function of the Atrioventricular (AV) valve?

Answer 3

Prevent blood returning to atria during ventricular contraction.

Question 4

What is the name of the Atrioventricular (AV) valve on the right and left sides of the heart?

Answer 4

• Right side: tricuspid valve.

- Left side : bicuspid (mitral) valve.

Question 5

How does the tricuspid and bicuspid (mitral) valves differ structurally?

Answer 5

• Tricuspid has 3 flap like leaflets

- Bicuspid only has 2 flaps/leaflets

Question 6

What is the diastole phase of heart contraction?

Answer 6

• Blood travels from the atrium to the ventricle i.e. it is the filling phase.
• The atrioventricular valves are open
• The semilunar valves are shut

Question 7

What is the (Ventricular) systole phase of heart contraction?

Answer 7

• This is when the contraction of the heart muscle occurs
• The atrioventricular valves are closed to prevent backflow of the blood
• Once the pressure from heart being full of blood exceeds the pressure in the outflow artery the semilunar valves are pushed open and blood flows out of the heart (ejecting)
• The semilunar valves then close again as blood starts to backflow into the heart

Question 8

After being squeezed out why does blood start to backflow into the heart?

Answer 8

There is passive recoil as the blood moves from the now high pressure outflow artery to the relatively low pressure chamber.

Question 9

What is the function of the semilunar valves?

Answer 9

Prevent blood returning to ventricles during

filling (diastole: the relaxed phase)

Question 10

What are the names of the semilunar valves on the right and left sides of the heart?

Answer 10

• Right side: Pulmonary (semilunar) valve

- Left side : Aortic (semilunar) valve

Question 11

How many cusps do the semilunar valves on both the right and left side of the heart have?

Answer 11

3

Question 12

In a diagram showing the heart valves visually which set of valves are the bigger circles?

Answer 12

-The AV valves (tricuspid and mitral)

Question 13

Why are the semilunar openings smaller than the AV openings?

Answer 13

• The semilunar valves are open in the ejection phase of heart contraction (systole) they therefore work under high pressure where it is easy to get blood through.
• The AV openings on the other hand need to be large so that blood will flow in to fill up the heart in the diastole phase of contraction as this is passive (not driven by pressure)

Question 14

What structures support the AV valves and why are they needed?

Answer 14

• It is large and also the one on the left side of the heart (mitral/bicuspid) only has 2 leaflets/flaps so doesn’t have as much support. Therefore, there are structures around that perform that function preventing collapsing.
• Papillary muscles extends into chordae tendineae(heart strings) which attach to the AV valves
• When pressure rises in the ventricle a muscle contracts inside the papillary muscle this creates tension in chordae tendineae causing leaflets of the AV to shut slowly rather then not slamming thus preventing damage.

Question 15

What are the vessels of cardiac circulation?

Answer 15

Supply=

• Go from aorta (oxygenated)
• to coronary arteries right and left (oxygenated)
• to myocardial capillaries(oxygenated)- diffuse into tissues

Drainage=

• Cardiac veins (deoxygenated)
• to coronary sinus (deoxygenated)
• to right atrium (deoxygenated)

Question 16

What is the basic idea of cardiac circulation?

Answer 16

The heart has its own supply and drainage system, also includes the first part of the systemic circulation system as oxygenated blood reaches the heart first via the myocardial capillaries.

Question 17

The right side of the heart is drained by the…

Answer 17

Small cardiac vein

Question 18

The left side of the heart is drained by the…

Answer 18

Great cardiac vein

Question 19

What happens when the small and great cardiac veins combine?

Answer 19

Form the coronary sinus and deoxygenated blood flows into the right atrium

Question 20

How does cardiac muscle get it’s oxygen supply?

Answer 20

From capillaries, the thin walls of the myocardial capillaries mean efficient diffusion of oxygen across

Question 21

What does cardiac muscle cells look like under a microscope?

Answer 21

• It will have a striated(banded) appearance as the Z lines of the sarcomeres are visible
• Short branched cells
• Nuclei are centrally located +oval shaped and usually only 1 or 2 per cell
• Cytoplasmic organelles are packed at the poles of the nucleus
• Cells are interconnected via intercalated discs (ICDs)

Question 22

What is the structure of a capillary like?

Answer 22

• Just cells forming junctions with themselves to create a tube like shape.
• The hole in the middle is called the lumen and is only large enough to fit one red blood cell at a time

Question 23

What is the function of cardiac muscle?

Answer 23

The beating of the heart, it therefore cannot take a break like other forms of muscle e.g. skeletal

Question 24

What is the other name for cardiac muscle?

Answer 24

Myocardium

Question 25

How similar is cardiac muscle to other muscle types?

Answer 25

Has features of both smooth & skeletal muscle as | well as cardiac muscle specific specializations

Question 26

What will skeletal muscle cells look like under a microscope?

Answer 26

- Nucelli are at periphery and there are lots of them - Nucelli are at edge so that cytoplasm can be occupied by contractile apparatus in a uniform way for optimum force generation (will have striated appearance)

Question 27

How do you differ between a electro microscopy of smooth versus cardiac muscle?

Answer 27

- Both will have nuclei centrally located and only a few - Smooth however, will not have a striated appearance like cardiac does - Also, for cardiac mitochondria makes up 20% of the volume of the cell whereas for smooth its just 2%

Question 28

Why is there so much mitochondria in cardiac muscle cells?

Answer 28

- Cardiac muscle is dependent on oxygen for metabolism (need ATP) thus need a lot of mitochondria - The swap to this source was that it means the heart muscle can burn any fuel, this is vital as it cannot stop

Question 29

How does the striated pattern differ in cardiac and skeletal muscle?

Answer 29

- For cardiac there is irregular branched sarcomeres with the Z lines at different angles - In skeletal muscles the pattern is a lot more uniform

Question 30

What are intercalated discs?

Answer 30

-2 cardiac myocytes join together via intercalated discs (3 intercellular joins working as a unit) The 3 intercellular joins are: - Adhesion belts (linking actin to actin)= Vertical portion - Desmosomes (linking cytokeratin with cytokeratin). - Gap junction (electrochemical communication) =Horizontal portion

Question 31

What is the conduction system of the heart?

Answer 31

-Its actions greatly increase the efficiency of heart pumping. -This system is responsible for the co-ordination of heart contraction and of atrioventricular valve action. -Autonomic nerves alter the rate of conduction impulse generation

Question 32

What type of tissue are conduction pathways made of?

Answer 32

It is not nervous tissue but modified cardiac muscle

Question 33

What are Purkinje cells?

Answer 33

'Bloated’ non-contractile cardiac muscle involved with electrical conduction.

Question 34

What is the structure of Purkinje cells like?

Answer 34

- (some) Peripheral myofibrils but not longer contract - Have central nucleus - Have mitochondria, glycogen (as need energy dependent stores to drive conduction) - Lots of gap junctions, some desmosomes & few adhesion belts. - 1% of cardiac cells

Question 35

What does the left coronary artery spilt into?

Answer 35

- Circumflex artery (goes to back) | - Anterior interventricular artery (goes downish)

Question 36

Describe the steps for the heart's conduction system...

Answer 36

- SA node to internodal pathways to AV node (alternative pathway is the interatrial pathway meets at AV node) - Down the septum into what is called the bundle of his (R and L: spilt in two) - Towards the apex and spreads upwards via the purkinje fibers.

Question 37

What is the idea of pacemaker cells? (give examples)

Answer 37

- The heart is not completely controlled by the brain (can beat on its own). - Pace maker cells depolarize at a certain rate independent of brain - 2 types are the SA node (controller) and the AV node (is backup)

Question 38

How is the heart innervated?

Answer 38

Dual innervated by the parasympathetic and sympathetic systems. -Whatever signal is the strongest wins

Question 39

What are the trabeculae carnae?

Answer 39

Muscular beam like structures on the inner surface of the myocardium forming ridges or bridges