Cardiovascular: Anatomy of Heart II L4

Question 1

Name the four heart valves and the two types.

Answer 1

Atrioventricular (Tricuspid and Mitral) and Semilunar (Aortic and Pulmonary).

Question 2

What does the cardiac skeleton do?

Answer 2

Separates the atria from the ventricles (electrically and physically), also anchors the cardiac muscle.

Question 3

How are atrioventricular valves attached in the heart?

Answer 3

Valves are attached to Chordae Tendineae (made of DFCT) which are attached to finger-like projections coming off the heart wall called papillary muscle.

Question 4

The role of Chordae Tendineae is?

Answer 4

Ensures that valves don’t close too hard and don’t get turned inside out and leak when pressure builds up, otherwise regurgitation occurs.

Question 5

What is Diastole?

Answer 5

Diastole is the atrial contraction causing atrioventricular valves to open allowing blood to pass through from atria to ventricles.

Question 6

What is Systole?

Answer 6

Atrioventricular valves close in ventricular contraction, preventing blood to flow back into the atria. Also semilunar valves open during systole (ventricular contraction).

Question 7

How many cusps do semilunar valves have? Do they require Chordae Tendineae?

Answer 7

3 cusps. They do not require chordae tendineae/papillary muscles. The cusps push open as blood flows out of the heart and close if blood begins to backflow.

Question 8

Where does cardiac circulation originate?

Answer 8

Left and Right Coronary arteries, the first arteries to branch off the aorta.

Question 9

Where does the left coronary artery go to/branch to? Name the location of these arteries by identifying their respective grooves they inhabit.

Answer 9

The left coronary artery runs in the coronary groove on the surface of the heart, this groove separates the atria from ventricles. The left coronary artery then branches off into 2. One branch is called the circumflex artery which bends around the heart. The second branch is the ‘anterior interventricular branch of the left coronary artery’ which runs in a groove called the anterior interventricular sulcus.

Question 10

Where does the circumflex artery and anterior interventricular left coronary artery, lead to first?

Answer 10

These vessels run firstly into the epicardium, and then deeper to supply blood to the rest of the cardiac muscle. This means the heart is the first organ to receive oxygenated blood.

Question 11

Give an example of how cardiac veins and coronary arteries can be similar (pertaining to grooves).

Answer 11

The great cardiac vein goes along the same surface groove as the anterior interventricular branch of the left coronary artery, which is the anterior interventricular sulcus.

Question 12

Where do the majority of cardiac veins drain into?

Answer 12

The majority of cardiac veins drain into a large vein called the coronary sinus (large venous space, posterior to coronary groove), which then carries deoxygenated blood into the right atrium.

Question 13

Percentage of mitochondria in cardiac muscle? Why is this important?

Answer 13

25%, needs the heart to beat for an entire lifetime without fatigue.

Question 14

How is cardiac muscle similar to smooth muscle?

Answer 14

Neither fatigue, both have one or occasionally 2 centrally located nuclei per cell.

Question 15

How is cardiac muscle similar to skeletal muscle?

Answer 15

Contains well-organised contractile units and is therefore striated.

Question 16

How is cardiac muscle unique to other muscle types?

Answer 16

Cardiac muscle is short, fat cells that branch with each other via special intercellular junctions called intercalated discs.

Question 17

What are the three types of cell junctions found within intercalated disc?

Answer 17

Adhesion belts - link cells by binding to actin to actin (vertical portion)
Desmosomes - act like ‘buttons’ or ‘spots’ of attachment by linking cells via cytokeratin.
Gap junctions - enable electrochemical transduction of action potentials. (horizontal portion)

Question 18

Why is it optimal for the heart to have irregular branched sarcomeres in all directions rather than the ordered organised form of sarcomeres in skeletal muscle?

Answer 18

Irregular branched sarcomeres tug on neighbours in a 3-Dimensional space in all directions rather than a skeletal muscle’s 2-D space so that the heart as a whole can contract together.

Question 19

Why does the cardiac muscle have intercalated discs?

Answer 19

To contract in unison as a whole unit.

Question 20

Describe what are Purkinje fibres.

Answer 20

Purkinje fibres are specialised cardiac myocytes, making up 1% of cardiac cells.

Question 21

What is the difference in function between cardiac muscle and Purkinje cells?

Answer 21

Cardiac muscle is specialised for contraction, whereas Purkinje fibres are specialised for the conduction of electrical signals that trigger contraction of cardiac muscle.

Question 22

What does a Purkinje cell contain in relation to cardiac muscle?

Answer 22

Like cardiac muscle, Purkinje fibres contain many mitochondria and a centrally located nucleus. Purkinje fibres are larger than cardiac muscle fibres but comparatively they contain only a few myofibrils. The myofibrils are located on the periphery of the cell. They also have a large amount of glycogen required by mitochondria to create energy for conduction. Purkinje fibres will therefore be more paler in colour than cardiac muscle fibres.

Question 23

How do Purkinje fibres connect?

Answer 23

Mainly by gap junctions, reflecting their function, speeding up propagation of action potentials.