Respiratory Embryo

Question 1

When does gas exchange happen in a baby?

Answer 1

Not until after birth (transitional circulation)

Question 2

What layer is the lining of the respiratory system from?

Answer 2

endoderm

Question 3

What are the muscle, cartilage, vessels, and connective tissue of the respiratory system from?

Answer 3

mesoderm

Question 4

What is the nervous system part of the respiratory system from?

Answer 4

ectoderm

Question 5

What is the lung bud?

Answer 5

Out-pouching from the ventral wall of the cranial portion of the endoderm (foregut)

Question 6

What is the innervation of the larynx?

Answer 6

superior laryngeal and recurrent laryngeal nerves

Question 7

What are the cartilage and muscles derived from in the larynx?

Answer 7

4th and 6th pharyngeal arches

Question 8

Where does the larynx open into the pharynx? What part of the respiratory tree is the larynx?

Answer 8

Btn the 4th & 6th pharyngeal arches; larynx is most proximal portion of the respiratory tree

Question 9

How are the trachea and esophagus divided?

Answer 9

Two ridges form to separate them - tracheo-oesophageal septum

Question 10

What’s a tracheoesophageal fistula? What’s a fistula in general? What’s an esophageal
atresia?

Answer 10

A TEF is an abnormal connection (fistula) between the esophagus and the trachea. A fistula in general is an abnormal communication between two epithelialized surfaces. Congenital TEF can arise due to a failed fusion of the tracheoesophageal ridges during the 3rd week of embryological
development. VACTERL association.

Esophageal atresia - the esophagus ends in a blind-ended
pouch rather than connecting normally to the stomach

Question 11

What is the VACTERL association with TEF?

Answer 11

Vertebral
Anorectal
Cardiac
Tracheal
Esophageal
Radial/Renal
Limb

Question 12

The trachea buds into the right and left main bronchi in the 5th week. What do the right and
left main bronchi branch into?

Answer 12

R: 3 secondary bronchi, 10 tertiary (segmental) bronchi. L: 2 secondary bronchi, 8 segmental
bronchi

Question 13

What are heterotaxy syndromes?

Answer 13

Heterotaxy syndrome is a disorder that results in certain organs forming on the opposite side
of the body. For example, instead of the heart normally forming on the left side of the chest, it
will be located on the right side. Heterotaxy has been known to affect the development of the
heart, liver, lungs, intestines, and spleen.

Question 14

What’s in the pseudoglandular period (5-16 wks)?

Answer 14

Terminal bronchioles present

Question 15

What’s in the canalicular period (16-26 wks)?

Answer 15

Respiratory bronchioles and alveolar ducts

Question 16

What’s in the terminal sac period (26 wks to birth)?

Answer 16

Terminal sacs, capillaries are close

Question 17

What are the four periods of lung maturation?

Answer 17

Pseudoglandular (5-16 wks), canalicular period (16-26 wks), terminal sac period (26 wks to
birth), alveolar period (8 mo to childhood)

Question 18

What do we get if there’s abnormal budding (defective mesenchyme) in respiratory
development?

Answer 18

Bronchogenic cysts; respiratory lined cysts that are adjacent to the respiratory tree but not
connected

Question 19

If there is abnormal signaling in bronchial epithelium-mesenchyme communication, what can
we get?

Answer 19

CCAM: Congenital Cystic Adenomatoid Malformation

Question 20

Explain the malformation histology of Cystic Adenomatoid (CCAM)? What can we diagnose
it with?

Answer 20

Increased terminal bronchiolar tissue, intercommunication cysts lined by respiratory
epithelium, restricted to one part of one lung. Diagnosed by prenatal ultrasonography or fetal
MRI

Question 21

What happens when the esophagus is compressed from fetal lung lesions?

Answer 21

polyhydramnios

Question 22

What happens when the lung is compressed from fetal lung lesions?

Answer 22

hypoplasia

Question 23

What happens when the vena cava and heart are compressed by fetal lung lesions?

Answer 23

hydrops (fetal heart failure)

Question 24

Abnormal lung budding leads to ______

Answer 24

Aberrant/absent bronchi

Question 25

Failure of mesenchymal maturation results in _______

Answer 25

Persistent systemic circulation to the lung

Question 26

What’s a pulmonary sequestration?

Answer 26

Lung mass with: blood supply from abnormal systemic artery & no anatomically normal
bronchus

Question 27

What’s an extralobar pulmonary sequestration?

Answer 27

It’s separate from the normal lung usually in the posterior/lower chest; systemic artery,
venous drainage to azygous, hemiazygous, portal or pulmonary veins

Question 28

What’s an intralobar pulmonary sequestration?

Answer 28

It’s within the visceral pleural envelope, an artery from descending or abdominal aorta,
venous drainage to pulmonary veins

Question 29

With respect to lung maturation, there is a steady increase in # of ______ from 7th month to
school age

Answer 29

alveolar sacs

Question 30

What can lung maturation and surfactant production be stimulated by?

Answer 30

Steriod administration; artificial surfactant can also be administered

Question 31

Initially the pleural and peritoneal cavities are one completely open cavity. What’s the last
thing to close?

Answer 31

Pleuroperitoneal canal (posterolateral)

Question 32

Does fetal breathing movement occur before birth? Talk about fetal lung fluid.

Answer 32

the lungs actively produce fluid in-utero. Fetal breathing movement does occur before birth.
Amniotic fluid also assists with lung development in-utero. The fluid is expelled as the child
passes through the birth canal and with the first cry. The remaining fluid is absorbed by
pulmonary lymphatics leaving a coat of surfactant

Question 33

What’s the origin for the pleura? If there is fluid in the pleural space and an abnormal
communication between the structures, is this a fistula?

Answer 33

Mesoderm; not a fistula since this is not epithelialized!

Question 34

What is a congenital diaphragmatic hernia? Which side does it usually occur on?

Answer 34

CDH is a congenital malformation (birth defect) of the diaphragm. Malformation of the
diaphragm allows the abdominal organs to push into the proper lung formation. Newborns with
CDH often have severe respiratory distress; life-threatening pathology. Usually occurs on the left side – mortality is high, especially prenatally

Question 35

What’s the concept of fetoscopic tracheal occlusion (FETO)?

Answer 35

Block/plug the trachea to keep fluid in underdeveloped lungs to make the lung expand and grow