Resp Embryology

Question 1

What are the germ layer contributions to respiratory development

Answer 1

Endoderm: resp tract from foregut endoderm
Lateral plate mesoderm:
1. Splanchnic mesoderm - lines endoderm. Visceral pleura, sm muscle including diaphragm
2. Somatic mesoderm - parietal pleura
3. Intra-embryonic coelom - pleural cavity

Question 2

Name the stages of development of the respiratory system in weeks

1. 4-6
2. 6-17
3. 17-26
4. 27-36
5. 36-8yrs

Answer 2

1. Embryonic stage - wk4 diverticulum, wk5 secondary lung buds
2. Pseudoglandular - 16 generations of branching, terminal bronchioles
3. Canalicular - resp bronchioles, vasculature, begin cytodifferentiation
4. Saccular - primitive alveoli, surfactant
5. Alveolar - alveoli multiply and mature

Question 3

4 contributions to diaphragm development

Answer 3

1. Septum transversum - ventral
2. Pleuroperitoneal membranes - dorsal + lateral
3. Dorsal mesentery of esophagus
4. Diaphragm muscle from cervical somites 3, 4, 5 (paraxial mesoderm)

Question 4

Source of development of pulmonary circulation:

1. Pulmonary A
2. Pulmonary V
3. Capillary beds

Answer 4

1. Pulmonary A = Brachial arch 6
2. Pulmonary V = vascular plexus between heart and liver
3. Capillary beds = angiogenesis from pre-existing pulmonary vessels

Question 5

Describe how blood is shunted in the fetal/neonatal heart

Answer 5

2/3 flow via foramen ovale

1/3 continue into pulmonary A
90% shunted via ductus arteriosus
10% fetal lungs (fluid filled alveoli create high resistance)

Question 6

Describe 2 developmental abnormalities of the respiratory system

Answer 6

1. Trachea-esopghageal fistula - incomplete division of the foregut and developing resp tract
2. Congenital Diaphragmatic Hernia - pleuroperitoneal foramen (bochdalek) fails to close on the left side. Intestine, stomach, spleen can enter pleural cavity = compressing lung