Embryology

Question 1

Where does the heart originate?

Answer 1

It is a mesodermal structure that comes from the visceral mesoderm

Question 2

What makes a midline tube structure in the development of the heart?

Answer 2

As the embryo folds the 2 sides of the horseshoe shape come together

Question 3

What type of folding moves the heart down to the thoracic cavity?

Answer 3

Cranial caudal folding

Question 4

How many dilatations does the heart tube develop?

Answer 4

5

Question 5

Where does blood flow from and to in the embryological heart?

Answer 5

From the sinus venous at the caudal end to the truncus arteriosus at the cranial end

Question 6

What does the truncus arteriosus form in the adult heart?

Answer 6

Aorta and pulmonary trunk

Question 7

What does the bulbus cordus form in the adult heart?

Answer 7

Trabeculated (muscular ridges) part of the right ventricle and the outflow part of both ventricles

Question 8

What does the embryological ventricle form in the adult heart?

Answer 8

Trabeculated part of the left ventricle

Question 9

What does the embryological atrium form in the adult heart?

Answer 9

Trabeculated part of both atria

Question 10

What do the sinus venosus form in the adult heart?

Answer 10

Smooth part of the right atrium and the coronary sinus

Question 11

5 dilatations that the heart tube develops

Answer 11

Truncus arteriosus, bulbus cordus, ventricle, atrium, sinus venosus

Question 12

On which day does the heart begin to loop and fold?

Answer 12

Day 23

Question 13

As the heart loops and folds, what happens to the:

• Atrium
• Ventricle
• Bulbus cordis

Answer 13

• Atrium moves dorsally and cranially, which impacts the ventricle
• Ventricle is displaced left, which impacts the bulbus cordis
• Bulbus cordis is moved inferiorly and ventrally to the right

Question 14

How many pairs of vessels are there in the development of the vasculature?

Answer 14

6

Question 15

Development of the vessels:

- What do vessels 1 and 2 contribute to?

Answer 15

The neck

Question 16

Development of the vessels:

- What do vessels 3 give rise to?

Answer 16

The common carotid arteries, first part of internal carotid artery

Question 17

Development of the vessels:

- What does the right and left part of vessel 4 give rise to?

Answer 17

Right gives rise to subclavian artery, left contributes to part of the aortic arch

Question 18

Development of the vessels:

- Vessel 5

Answer 18

Rudimental or absent

Question 19

Development of the vessels:

- What does the right and left vessels from pair 6 give rise to?

Answer 19

Right = sprout branches that form pulmonary arteries
Left = forms the ductus arteriosus

Question 20

3 things each horn of the sinus venosus receives

Answer 20

Common cardinal vein (anterior and posterior), vitelline vein, oxygenated blood comes from the placenta via umbilical vein

Question 21

What does most of the venous drainage in the unformed embryological heart

Answer 21

Common cardinal veins

Question 22

What happens to the following as development of the heart progresses:

• Umbilical veins
• Vitelline veins

Answer 22

• Communication between left and right umbilical veins is lost
• The right vitelline vein gets a lot larger than the left

Question 23

What do vitelline veins do?

Answer 23

Drain the yolk sac

Question 24

What do cardinal veins do?

Answer 24

Give systemic venous system - drain blood

Question 25

What do the umbilical veins do?

Answer 25

Brings oxygenated blood from the placenta

Question 26

What do the vitelline veins develop into in the adult heart?

Answer 26

Portal venous system draining gut, hepatic sinusoids and veins, hepatic portions of IVC

Question 27

What do the anterior cardinal veins drain?

Answer 27

Head and neck

Question 28

What do the anterior cardinal veins develop into in the adult heart?

Answer 28

Jugular system, left brachiocephalic vein, SVC

Question 29

What do the posterior cardinal veins drain?

Answer 29

Trunk

Question 30

What do posterior cardinal veins develop into in the adult heart?

Answer 30

Azygous and hemiazygous systems (body wall), gonadal and renal veins, iliac veins, IVC

Question 31

Placental functions

Answer 31

- Foetal homeostasis - Gas exchange - Acid base balance - Nutrient transport to the foetus - Waste product transport from the foetus - Hormone production - Transport of IgG – provide immunity to infectious disease after birth - PGE2 (prostaglandin E2) – important in maintaining foetal circulation

Question 32

Where does the placenta sit?

Answer 32

End of the umbilical cord. Cross section of the umbilical cord with 2 arteries and 1 vein

Question 33

What does the foetal heart pump blood to the placenta via?

Answer 33

Umbilical arteries

Question 34

What does the blood from the placenta return to the foetus via?

Answer 34

Umbilical veins

Question 35

3 "shunts" specific to foetal life

Answer 35

Ductus venosus, foramen ovale, ductus arteriosus

Question 36

What does the ductus venosus connect?

Answer 36

Connects the umbilical vein to the IVC

Question 37

What is the foramen ovale?

Answer 37

An opening in the atrial septum connecting the right atrium to the left atrium

Question 38

Function of the foramen ovale

Answer 38

Allows oxygenated blood to go into the left atrium, then left ventricle then out the aorta

Question 39

What does the ductus arteriosus connect?

Answer 39

Connects pulmonary bifurcation to the descending aorta

Question 40

Function of the ductus venosus

Answer 40

Carries the majority of the placental blood straight to the IVC bypassing portal circulation

Question 41

What maintains patency of the ductus arteriosus?

Answer 41

Circulating prostaglandin E2 produced by the placenta

Question 42

Adaption of the pulmonary system just after birth

Answer 42

Baby inflates lungs and cries and goes from blue to pink, the cord stops pulsating and is clamped shut, the fluid within the lungs gets pushed out of the alveoli when the baby cries and it is reabsorbed by the lymphatic system and the alveoli are able to be filled with air

Question 43

Circulatory changes after birth

Answer 43

Decreased pulmonary vascular resistance, increased systemic vascular resistance, more cardiac output to lungs

Question 44

What causes decreased pulmonary resistance after birth

Answer 44

The breath in causes the lungs to physically expand, and there is increased circulating oxygen. In lung circulation the oxygen is a vasodilator and this causes decrease in pulmonary resistance

Question 45

How does the foramen ovale close after birth?

Answer 45

Pulmonary vascular resistance falls, systemic vascular resistance rises and this causes the left atrial pressure to exceed the right atrial pressure and the flap is pushed closed

Question 46

What causes ductus arteriosus constriction after birth?

Answer 46

Increased pO2, decreased flow and decreased prostaglandin

Question 47

What does the ductus arteriosus end up as?

Answer 47

Fibrous ligament - ligamentum arteriosum

Question 48

Treatment options for failure of ductus arteriosus closure

Answer 48

Wait and see (often close by themselves), NSAIDs, surgery

Question 49

What can be used to keep the ductus arteriosus open when there is 'duct dependent circulation'

Answer 49

IV prostaglandin E2 until an alternative shunt is established or definitive surgery is carried out

Question 50

When does pulmonary resistance reach 'normal' adult-type levels?

Answer 50

By 2-3 months

Question 51

What causes persistent pulmonary hypertension of the newborn

Answer 51

Lung vascular resistance fails to fall as shunts remain (foramen ovale and ductus arteriosus)

Question 52

Risk factors for persistent pulmonary hypertension of the newborn

Answer 52

Sepsis, hypoxic ischaemic insult, meconium aspiration syndrome, cold stress

Question 53

Oxygen saturation in baby's hand vs baby's foot in persistent pulmonary hypertension of the newborn

Answer 53

Both low: - Baby's hand = 80% - Baby's foot = 60%

Question 54

Signs and symptoms of persistent pulmonary hypertension of the new born

Answer 54

Blue baby with low oxygen saturations

Question 55

Management of persistent pulmonary hypertension of the newborn: - Reduce pulmonary vascular resistance - Increase systemic vascular resistance

Answer 55

- Reduce PVR = oxygen, ventilation, sedation, thermoregulation, correction of acidosis, treatment of sepsis, inhaled NO - Increase SVR = maintain blood pressure, inotropes, support of other organ function, extra corporeal life support in severe cases