Lecture 33: Heart Histology

Question 1

What components make up the wall of the heart

Answer 1

The epicardium, myocardium, endocardium, and fibrous skeleton

Question 2

Describe the endocardium

Answer 2

Lines the inner surface of the heart and is composde of simple squamous epithelium

Question 3

Describe the mycocardium

Answer 3

Composed of cardiac muscle. Takes up a lot of space in the heart wall

Question 4

Describe the epicardium

Answer 4

Outer layer. Composed of adipose tissue and CT

Question 5

Describe the fibrous skeleton

Answer 5

Is 4 fibrous rings that are the framework for attachment of myocardial fibres. Also anchor valves at their base. The fibrous skeleton is arranged to maximize contraction

Question 6

Describe the location and function of the fibrous rings of the fibrous skeleton

Answer 6

Surrounds orafaces of each of the valves and anchors and supports them

Question 7

Describe cardiomyocytes

Answer 7

Are involuntary muscle
Striated
Branched
Has 1-2 centrally located nuclei
Connected via intercalated discs

Question 8

What are intercalated discs made of. What do these components provide?

Answer 8

Gap junctions – electrically connect adjacent cells and allows for the passage of ions in cells that produce depolarization
Desmosomes: Increase contractile response by keeping cardiomyocytes attached close together

Question 9

T or F: the cardiac conducting system works independently of the nervous system

Answer 9

TRUE!

Question 10

describe the location and function of the sinoatrial (SA) node

Answer 10

Posterior wall of the right atrium
Sets the pace of the electrical impulse
Sends signal to the atria to contract

Question 11

Describe the location and function of the atrioventricular (AV) node

Answer 11

Located above the coronary sinus opening
Sends a signal from the atria to the ventricles

Question 12

Why is there a brief pause between the SA and AV node?

Answer 12

To ensure that the atria has fully contracted before contraction occurs in the ventricles

Question 13

Describe the location and function of the Bundle of His

Answer 13

Located within the interventricular septa
Carries impulse to the ventricles

Question 14

Describe the location and function of the purkinje fibres

Answer 14

Located in the sub-endothelium below the endocardium
Propagates impulse to the ventricles

Question 15

Describe how the medulla oblongata is involved in cardiac conntrol

Answer 15

Is part of the cardioacceleratory cente and cardioinhibitory center

Question 16

Describe the cardioacceleratory centre

Answer 16

Located within the medulla oblongata
Carries sympathetic ganglia
Releases Norepinephrine
Increases heart rate

Question 17

Describe the cardioinhibitory center

Answer 17

Located within the medulla oblongata
Parasympathetic
Releases acetylcholine
Decreases heart rate

Question 18

What is the systolic phase associated with?

Answer 18

Contraction and increased pressure

Question 19

What is the diastolic phase associated with?

Answer 19

Relaxation and filling, decreased pressure

Question 20

In Atrial systole, what is occurring?

Answer 20

SA node is activated
Atrial contraction is occuring
Active filling of ventricles

Question 21

In atrial diastole, what is occurring?

Answer 21

Passive filling
Atrioventricular valves close

Question 22

In Ventricular Systole (phase 1), what is occurring?

Answer 22

Beginning of ventricular contraction
AV valve closes

Question 23

In ventricular systole (phase 2), what is occurring?

Answer 23

Ventricular pressure rises
Semilunar valves open

Question 24

In Ventricular diastole - early, what is occurring?

Answer 24

Decrease in ventricular pressure
Semilunar valves close
Blood flows into the atria

Question 25

In ventricular diastole - late, what is occurring?

Answer 25

All chambers are relaxed
AV valves open
Passive filling of ventricles