Development of Cardiovascular System

Question 1

Describe the stages of heart development

Answer 1

Linear heart tube formation
Formation of the cardiac loop
Heart septation
Cavitation of ventricle, formation of valves and great vessels
4 chambered heart, not fully mature

Question 2

Describe linear heart tube formation

Answer 2

Around day 22
Need picture
1st aortic arch, truncus arteriosus, conus cordis, bulbus cordis, ventricle, atrium, L/R sinus venosus horn

Question 3

What makes the outflow tract/region?

Answer 3

Truncus arteriosus
Conus cordis
Bulbus cordis

Question 4

What does the truncus arteriosus develop into?

Answer 4

Most of proximal aorta and pulmonary trunk

Question 5

What will the bulbus cordis develop into?

Answer 5

Right ventricle

Question 6

What will the ventricular region develop into?

Answer 6

Left ventricle

Question 7

What will the left sinus venosus horn develop into?

Answer 7

Coronary sinus

Question 8

What will the right sinus venosus horn develop into?

Answer 8

Smooth wall of RA

Question 9

What is another name for sinus venosus?

Answer 9

Inflow region/tract

Question 10

How does the cardiac loop form?

Answer 10

Ventricles and bulbus cordis of the heart grow faster than other regions, therefore the heart bends in the rightward direction
Leads to atrium and sinus venosus to move cranially and dorsally (initially caudal to ventricle)

Question 11

Around what day is looping complete?

Answer 11

28th day

Question 12

Name the endocardial cushions and describe where they are

Answer 12

1. Atrioventricular cushions - AV canal
2. Truncates cushions/ridges - top of OFT
3. Canal cushions/ridges - below

Question 13

What are endocardial cushions?

Answer 13

Extracellular matrix proteins

Localised swellings in the OFT and AV canal

Question 14

What happens to the cushions?

Answer 14

Swell more as heart grows
‘Activated’ cells migrate into endocardial cushions
Cellularises with mesenchyme

Question 15

Why are cushions essential?

Answer 15

Cardiac valve formation and sepation of the heart

Question 16

When does septation of the primordial atrium occur?

Answer 16

4-6 weeks

Question 17

What occurs in the first step of septation of the primordial atrium?

Answer 17

Septum primum lengthens
Perforations form
Gap is called foramen primum

Question 18

What occurs in the second part of the septation of the primordial atrium?

Answer 18

Foramen secundum formed
Foramen primum closed
Septum secundum initiated

Question 19

What occurs in the third part of the septation of the primordial atrium?

Answer 19

Valve of foramen ovale forms from septum primum (foramen ovale)
Septum primum degenerating

Question 20

What occurs in the fourth part of the septation of the primordial atrium?

Answer 20

Foramen ovale closed by valve of foramen ovale

Question 21

When does septation of the primitive ventricle occur?

Answer 21

5-20 weeks

Question 22

Septation of the primitive ventricle

Answer 22

Interventricular septum grow up, closing the interventricular foramen
Made of thin membranous part of interventricular septum

Question 23

Cavitation of the ventricle

Answer 23

Papillary muscles, chordae tendineae - attach wall of ventricles to the valves

Question 24

Where are the mitral and tricuspid valves derived from?

Answer 24

Endocardial cushions

Takes weeks to develop - undergo modelling

Question 25

Which vessels are derived from the outflow region?

Answer 25

Aorta | Pulmonary trunk

Question 26

Formation of aorta and pulmonary trunk

Answer 26

Truncal and bulbar ridges are continuous, but positioning means they are spiralling round the outflow region of the heart P A separated by aortico-pulmonary septum A P A P Pulmonary trunk twists around ascending aorta

Question 27

Development of semi-lunar valves (aortic and pulmonary valves)

Answer 27

When division of truncus arteriosus is nearly complete Swellings begin to form near entrances From endocardial cushions

Question 28

Formation of SVC and IVC

Answer 28

Derived from primordial veins | Series of changes and remodelling and incorporation

Question 29

Development of pulmonary veins

Answer 29

Most of the smooth wall of the LA is derived from primordial pulmonary vein and branches As atrium expands, more of the PPV is incorporated until 4 veins present

Question 30

What occurs in the heart at birth?

Answer 30

3 shunts close Lungs expand - reduced resistance to blood flow Pressure in RA < LA Blood stops flowing through foramen ovale

Question 31

How does the foramen ovale close?

Answer 31

After first breath: RA has lower pressure than left, which closes the valve The fossa ovalis fuses over it (thin area of septum)

Question 32

What is the second shunt that closes postnatally?

Answer 32

Ductus arteriosus constructs | Leads to closure and ligamentum arteriosum forms

Question 33

What is the third shunt that shuts postnatally?

Answer 33

Ductus venosus constricts | Leads to closure and ligamentum venosum in liver forms

Question 34

When do lateral endocardial tubes form?

Answer 34

19 days

Question 35

When is a primitive 4-chambered heart formed?

Answer 35

7 weeks

Question 36

What are congenital heart defects usually caused by?

Answer 36

Single gene defect Chromosomal anomaly Exposure to teratogens

Question 37

Examples of congenital heart disease

Answer 37

Atrial Septal Defects Ventricular Septal Defects Patent Ductus arteriosus Tetralogy of fallout

Question 38

Describe ASD

Answer 38

Atrial Septal defects Common - 6.4/10,000 births Ore common in females Most clinically significant: ostium secundum ASD

Question 39

Pathophysiology of ASD

Answer 39

Enlarged RA, RV and PA | Considerable intracardiac shunting may occur

Question 40

Describe VSD

Answer 40

Ventricular Septal Defects Most common More common in males Usually involves membranous part of interventricular septum fails to develop normally

Question 41

Tetralogy of fallot

Answer 41

combination of four congenital abnormalities: | VSD, pulmonary valve stenosis, a misplaced aorta and a thickened right ventricular wall (right ventricular hypertrophy)