Embryology of Cardiovascular System

Question 1

Where does the CVS originate from in embryological development?

Answer 1

Mesoderm

Question 2

What are the 2 mechanisms involved in the formation of the vascular system?

Answer 2

1. Vasculogenesis - de novo development blood cells from endothelial cells differentiating in situ
2. Angiogenesis - new blood vessels

Question 3

Where does blood vessel development start?

Answer 3

Yolk sac + trophoblast layer

Question 4

What are the function of the decidua?

Answer 4

• Nourishment
• Helps form maternal component placenta - remainder forms decidua basalis
• Forms cleave plane so placenta + membranes can separate from uterus

Question 5

What is the fetal portion of the placenta called?

Answer 5

Chorion frondosum

Formed by growth of villi on embryonic side

Question 6

What is the maternal portion of the placenta called?

Answer 6

Decidua basalis

Question 7

What are the layers of the fetomaternal (placental) barrier?

Answer 7

1. Synctiotrophoblast
2. Cytotrophoblast
3. Basal lamina under cytotrophoblasts
4. Basal lamina of endothelium of fetal capillary
5. Endothelium of villous capillary

Question 8

Describe what happens in vasculogenesis

Answer 8

Blood islands fuse - endothelial cells arranged in vessels

Question 9

What is the common progenitor for hematopoietic and endothelial cells?

Answer 9

Haemangioblast

Question 10

When can vasculogenesis occur?

Answer 10

Restricted to embryonic development whereas angiogenesis can occur during entire lifespan

Question 11

What are the 4 dilations heart tube shows during embryological development?

Answer 11

1. Truncus arteriosus
2. Bulbus cordis
3. Primitive ventricle
4. Primitive artium
5. Sinus venosus

Question 12

What is cardiac dextral looping?

Answer 12

Correct venous blood flow from entering left ventricle so that it enters the right ventricle (like in adult heart)

Question 13

What happens during week 4-7 of heart development?

Answer 13

Heart divides into 4 chamber structure

Septum formation arises

Question 14

What develops in week 5 of heart development?

Answer 14

Conducting system of heart

Question 15

Describe saturated fetal circulation

Answer 15

Placental blood (saturated) > fetus via umbilical vein

Flows through ductus venosus into IVC

Mixes with deoxygenated and enters right atrium > passes through foramen ovale > left atrium

Mixes with some desaturated blood from lungs > left ventricle + ascending aorta

Question 16

Describe desaturated fetal circulation

Answer 16

Flows from SVC > right ventricle > pulmonary trunk

Blood passes through ductus arteriosus > descending aorta (mixes with blood from proximal aorta) > placenta via 2 umbilical arteries

Question 17

What circulatory changes take place at birth?

Answer 17

1. Closure of ductus arteriosus
2. Closure of umbilical arteries
3. Closure of foramen ovale
4. Closure of umbilical vein + ductus venous

Question 18

How does the ductus arteriosus close?

Answer 18

• By muscle wall contraction
• Immediately after birth
• Causes by bradykinin releases from lungs at first breath
• Takes 1-3 months for total obliteration
• > Ligamentum arteriosum

Question 19

How do the umbilical arteries close?

Answer 19

• Wall contraction
• Caused by thermal/mechanical stimuli + change in O2 tension
• Few mins after month
• 1-3 months for total

Question 20

How does the foramen ovale close?

Answer 20

• From increased pressure in left atrium and decreased pressure on right
• 1st breath/crying creates shunt right to left

Question 21

How does the umbilical vein and ductus venosus close?

Answer 21

After closure umbilical arteries

-> Ligamentum teres hepatis + Ligamentum venosum

Question 22

Name some cardiac teratogens

Answer 22

• Rubella
• Thalidomide
• Vitamin A (retinoic acid)
• Alcohol

Question 23

What is the most common type of congenital heart defect?

Answer 23

Ventricular septal defect