CVS S2 - The Heart as a Pump + Embryology S1

Question 0

Where does each side of the heart pump blood to?

Answer 0

Left: systemic circulation
Right: pulmonary circulation

Question 1

Name the compartments of the heart

Answer 1

Right atrium, left atrium, right ventricle, left ventricle

Question 2

How long is the cardiac action potential?

Answer 2

~200-300ms

Question 3

What controls contraction of the heart?

Answer 3

Pacemaker cells - normally the SAN (sino-atrial node) but if this isn’t working then the AVN (atrio-ventricular node) can perform the same function

Question 4

What is systole?

Answer 4

When the ventricles of the heart are contracting

Question 5

What is diastole?

Answer 5

When the ventricles are not contracting

Question 6

Describe atrial contraction

Answer 6

Not very forceful
Small volume of blood moved
Occurs just before ventricular systole

Question 7

Describe the first heart sound

Answer 7

Caused by the closure of the A-V valves
“Lub” sound
Occurs in ventricular systole

Question 8

Describe the second heart sound

Answer 8

Caused by the closure of the semi lunar valves
“Dub” sound
Occurs in ventricular diastole

Question 9

What do murmurs sound like and what causes them?

Answer 9

A “whooshing” noise

Caused by turbulent or disturbed flow eg through a narrowed valve

Question 10

What is cardiac output?

Answer 10

Cardiac output = stroke volume x heart rate

This is the volume of blood pumped by the left ventricle per minute

Question 11

When is the cardiogenic field formed?

Answer 11

Gastrulation

Question 12

Where is the cardiogenic field just after formation and where and how does it move?

Answer 12

The cardiogenic field is initially at the cranial end of the embryo
Embryonic folding causes the field to move into the chest area

Question 13

What is the cardiogenic field?

Answer 13

Embryonic tissue from which the heart, blood vessels and blood develop

Question 14

When do the endocardial tubes form?

Answer 14

In the third week of development

Question 15

What happens after the formation of the endocardial tubes?

Answer 15

The endocardial tubes are brought together in embryonic folding and fuse at the mid line to create the primitive heart tube

Question 16

Describe the primitive heart tube

Answer 16

-Highly symmetrical
-Has four sections:
>Bulbus cordis
>Truncus arteriosus
>Primitive atrium
>Primitive ventricle

Question 17

How does the primitive heart tube sit in the pericardial cavity?

Answer 17

Suspended by a membrane which subsequently degenerates

Question 18

What does looping achieve?

Answer 18

Places both the inflow and outflow cranially with the inflow dorsal (behind/posterior) to the outflow
Places primordium of right ventricle nearest to outflow tract
Places primordium of left ventricle nearest to inflow tract
Formation of the transverse pericardial sinus

Question 19

What will the primitive atrium become?

Answer 19

Contributes a SMALL component to the future atria

Question 20

What will the bulbis cordis become?

Answer 20

It will go on to form part of the right ventricle

Question 21

What will the primitive ventricle become?

Answer 21

The left ventricle

Question 22

What will the truncus arteriosus become?

Answer 22

It will give rise to the roots and proximal portions of the aorta and pulmonary trunk

Question 23

What does lateral/cephalocaudal folding achieve with respect to cardiac development?

Answer 23

Lateral folding causes formation of the primordial heart tube
Cephalocaudal folding brings the tube into the thoracic region

Question 24

Describe blood flow in the primitive heart tube

Answer 24

Linear at first
Caudal-end inflow from sinus venosus
Cranial-end outflow through aortic roots

Question 25

When does looping occur?

Answer 25

Between days ~23-28

Question 26

How does looping of the primitive heart tube proceed?

Answer 26

Continued elongation of the tube results in bending
The cephalic, cranial end bends ventrally, caudally and to the right
The caudal portion bends dorsally, cranially and to the left

Question 27

Describe communication between the atrium and ventricle after looping and what is the significance?

Answer 27

The communicate via the atrioventricular canal

This is the first division between the atrium and ventricle

Question 28

What is the transverse pericardial sinus?

Answer 28

The space behind the cardiac outflow and in front of the inflow where a finger can be inserted

Question 29

Describe the the sinus venosus and it’s development

Answer 29

All embryonic blood collects here
Right and left horns are initially equal
Venous return shifts to right hand side
Left horn recedes
Enlarging right atrium absorbs right sinus horn

Question 30

Describe development of the right atrium

Answer 30

Develops mostly from the primitive atrium
Absorbs the right horn of the sinus venosus
Receives drainage from the body (venae cava) and heart (coronary sinus) after birth

Question 31

Describe development of the left atrium

Answer 31

Develops from a small portion of the primitive atrium
Absorbs proximal parts of pulmonary veins
Receives oxygenated blood from the lungs after birth

Question 32

Describe the oblique pericardial sinus and it’s development

Answer 32

A “cul-de-sac” or recess

Formed as left atrium expands by absorbing the pulmonary veins

Question 33

Describe the general development of the aortic arches

Answer 33

Begins as bilaterally symmetrical system of arched vessels (1, 2, 3, 4, 6)
Undergo extensive remodelling
Most important arches are 4 and 6

Question 34

Describe the development of the 4th arch of the aorta

Answer 34

The right arch forms the proximal part of the right subclavian artery
The left arch forms the arch of the aorta

Question 35

Describe the development of the 6th arch of the aorta

Answer 35

Also known as the pulmonary arch
Right side forms right pulmonary artery
Left side forms left pulmonary artery and ductus arteriosus

Question 36

Describe the path of the right and left recurrent laryngeal nerves compared to one another

Answer 36

The left laryngeal nerve is pulled down lower than the right by the ductus arteriosus and the the descent of the heart