4. embryology of heart

Question 1

stages of heart formation

Answer 1

linear heart tube formation

formation of cardiac loop

heart septation

cavitation of ventricle, formation of valves and great vessels

4 chambered heart

Question 2

Answer 2

Question 3

Answer 3

Question 4

where is the inflow tract?

Answer 4

sinus venosus

Question 5

How does the cardiac loop form?

Answer 5

As the ventricles and bulbus cordis of the heart grow faster than other regions, the heart bends in a rightward direction. This leads to the atrium and sinus venosus, which were initially caudal (below) to the ventricle, moving cranially and dorsally.

Question 6

cardiac looping after 28 days

Answer 6

Question 7

what are endocardial cushions?

Answer 7

localised swellings in the outflow region and atrioventricular canal.

Question 8

what happens to endocardial cushions?

Answer 8

enlarge and protrude into lumen of heart

become cellularised-> activated cells, migrated into endocardial cushions

septa fuses with cushions

endocardial cushions form cardiac valves

Question 9

septation of primordial atrium

4 weeks

Answer 9

Perforations form in septum primum, the developing foramen secundum

Question 10

septation of primordial atrium

5-6 weeks

Answer 10

foramen secondum formed, foramen primum closes

Question 11

Answer 11

Question 12

Answer 12

Question 13

Answer 13

Question 14

formation of the great arteries

Answer 14

• truncal and bulbar ridges/ cushions are continuous but positioning shows that they are spiralling around outflow region of heart
• Division of the truncus arteriosus and bulbus cordis into the aorta and pulmonary trunk, occurs by the formation of the aorticopulmonary septum
• the aorticopulomnary septum spirals, so pulmonary trunk twists around ascending aorta

Question 15

how do semi lunar valves form in aorta and pulmonary trunk

Answer 15

When division of the truncus arteriosus is nearly complete, swellings begin to form near the entrance to the newly formed aorta and pulmonary trunk (outflow region of the heart), from endocardial cushions.

These swellings are the primordial aortic and pulmonary valves, and will ultimately form the mature semilunar valves.

Question 16

formation of SVC and IVC

Answer 16

Are derived from primordial veins which undergo a series of changes during development, leading to their remodelling and incorporation into these new vessels.

Question 17

formation of pulmonary veins

Answer 17

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

Question 18

Answer 18

Oxygenated blood from placenta

Enters in right atrium

Blood shunted straight to left atrium to left ventricle then around body

Some mixing of blood from blood returning of embryo and lungs

After first breath;

Three shunts close,

Question 19

how does foramen ovale close in postnatal circulation

Answer 19

• Lungs expand
• decreased Resistance to blood flow
• Pressure in RA < LA
• Blood stops flowing through foramen ovale

Question 20

three shunts that close

Answer 20

foramen ovale

ductus arteriosus constricts to form ligamentum arteriosum

ductus venosus constricts to form ligamentum venosus in the liver

Question 21

Answer 21

Question 22

5 congenital heart defects

Answer 22

atrial septal defects

ventricular septal defects

patent ductus arteriosus

patent truncus arteriosus

tetraology of fallot

Question 23

atrial septal defect

Answer 23

hole in heart

patent foramen ovale

usually small and of no significance if isolated

• The most clinically significant type is ostium secundum ASD

more common in females

Enlarged RA, RV, PA

Question 24

ventricular septal defect

Answer 24

Most common CHD

• More common in males
• Usually involves membranous part of interventricular septum failing to develop normally

Question 25

patent ductus arteriosus

Answer 25

too much blood going to lungs

Question 26

patent truncus arteriosus

Answer 26

primitive truncus doesnt divide into pulmonary artery and aorta- too much blood to lungs

Question 27

tetralogy of fallot

Answer 27

4 abnormalities-

pulmonary valve narrow, muscle below thickened

hole- ventricular septal defect

aorta over left and right ventricle instead of just left

right ventricle englarged and more muscular

can cause mixing of blood