Embryology of the reparatory system

Question 1

what is the point of transition between the upper and respiratory tract

Answer 1

the larynx

Question 2

what are the structures of the upper respiratory tract

Answer 2

nasal cavities
nasopharynx
oropharynx
(larynx)

Question 3

what are the structures of the lower respiratory pathway

Answer 3

(larynx) 
trachea 
bronchi 
bronchioles 
terminal bronchioles 
respiratory bronchioles 
alveolar ducts 
a sacs 
alveoli

Question 4

where does the respiratory portion start

Answer 4

reparatory bronchioles - alveoli

Question 5

which germ layer produces the inner epithelia and the connective structures of the lungs

Answer 5

inner epithelia - endoderm

connective structure - mesoderm

Question 6

which part of the gut tube does the respiratory diverticulum develop from

Answer 6

foregut in week 4

Question 7

which day does the respiratory diverticulum appear

Answer 7

lung buds develop day 22

Question 8

what direction do the lung buds grow

Answer 8

ventrocaudally

Question 9

what separates the reparatory diverticulum from the oesophagus (foregut)

Answer 9

tracheosophageal ridges (except laryngeal inlet)

Question 10

what is the orientation of the oesophagus and the trachea

Answer 10

trachea is anterior to the oesophagus

Question 11

what is a fistula

Answer 11

an abnormal communication

Question 12

what are the two types of malformations in development of the lungs

Answer 12

atresia with fistula 85-90%

fistula

Question 13

why do malformations occur

Answer 13

incomplete division of foregut into oesophageal and respiratory proteins

Question 14

what is an atresia

Answer 14

proximal closing off of the oesophagus

Question 15

what is tracheoesophageal fistula with oesophageal atresia and what are the problems associated with it

Answer 15

upper oesophagus ends abruptly, lower oesophagus forms fistula with trachea - causes abdomen rapidly to distend as stomach fills with air
the atresia causes air sacs to be filled with milk and other contents from the stomach such as enzymes and acid

Question 16

what is H type tracheoesphaogeal fistula

Answer 16

communication between oesophagus and trachea
approx 4% of cases
milk goes into respiratory system and causes infection

Question 17

TOF are usually associated with other congenital abnormalities what are they

Answer 17

V - vertebral defects 
A - anal atresia 
(C) - cardiac defects 
T - tracheooseophageal fistulas 
E - Esophageal atresia 
R - Renal abnormalities 
(L) - limb defects

Question 18

what happens in week 5 to the lungs

Answer 18

further growth and differentiation - formation of main bronchi and secondary bronchi (day 30)
3 on the right and 2 on the left

Question 19

what happens to development during the 6th week

Answer 19

tertiary bronchi - which each supply a bronchopulmonary segment
10 right and 8 left

Question 20

branching stages are different during development
what occurs at week 16
26
36

Answer 20

terminal bronchioles - 16
respiratori bronchioles - 26 (poor gas exchange can occur)
alveoli - 36

Question 21

what forms from the visceral mesoderm

Answer 21

cartilage, smooth muscle, connective tissue capillaries and visceral mesoderm

Question 22

what are the two formations of the pleura

Answer 22

visceral mesoderm - visceral pleura
parietal mesoderm - parietal pleura
lateral plate of the mesoderm forms the pleura

Question 23

what is pulmonary agenesis

Answer 23

failure for lung to form properly

occurs when lung bud fails to split causing complete absence of bronchi and vasculature

Question 24

what is the clinical presentation of pulmonary agenesis

Answer 24

child usually develops respiratory distress
remaining lung is compromised - usually lower respiratory tract infection
common with vertebra for rib anomalies

Question 25

what can happen to the lung in unilateral pulmonary agenesis

Answer 25

enlarge

Question 26

what is pulmonary hypoplasia

Answer 26

incomplete development of the lungs severity determines extent of development may be found in association with congenital diaphragmatic hernia

Question 27

what is branching morphogenesis

Answer 27

produce azygous lobe (extra lobe) - little functional difference

Question 28

what are the four periods of maturation of the lungs

Answer 28

``` (embryonic) pseudoglandular canalicular saccular/terminal sac alveolar there is overlap between the stages ```

Question 29

what week does surfactant start to get produced

Answer 29

around the 25/26th week

Question 30

what is the difference in weeks of the embryonic and the fetal period

Answer 30

embryonic - 2-8 weeks | fetal - 8-38 weeks

Question 31

what happens during the pseudoglandular period and what is the rough time span of the period

Answer 31

5-17 weeks branching of the respiratory tree has occurred to form terminal bronchioles (respiration still cannot occur - still part of the conduction pathway)

Question 32

what happens during the canalicular period and what is the rough time span

Answer 32

16-25 weeks terminal bronchioles give rise to respiratory bronchioles which give rise to alveolar ducts mesodermal tissue becomes highly vascularised respiration possible towards the end of this period towards the end of this period there is better prognosis for birth but low chance of fetal survival

Question 33

what is the rough time span of the terminal sac/ saccular period and what occurs

Answer 33

from week 26 until birth primitive alveoli are developed epithelium thins and capillaries come into contact with epi blood air barrier formed surfactant forms a film over the internal walls - facilitating inflammation of the lungs

Question 34

what does the epithelium differentiate into and in what period

Answer 34

saccular period - divides into type 1 neumocytes where gas exchange occurs types 2 pneumocytes where surfactant is produced

Question 35

what is most likely to happen to a fetus born prematurely at 24 week s

Answer 35

respiratory distress syndrome

Question 36

what is the alveolar period

Answer 36

36 - 8 years development of he lugs which increase in number of alveoli and respiratory bronchioles 95% of mature alveoli do not develop until after birth

Question 37

what happens to the lungs during birth

Answer 37

breathing starts in utero to remove amniotic fluid - kick starts respiration in muscles remaining lung fluid is rapidly absorbed into capillaries

Question 38

what is the prime factor in prognosis if child is born prematurely

Answer 38

development of the lungs

Question 39

what is respiratory distress syndrome

Answer 39

eg birth at 23 weeks laboured breathing increased rate of breathing mechanical ventilation needed damage to alveolar lining as fluid and serum leak into alveoli can lead to bronchopulmonary dysplasia (abnormal formation)

Question 40

what are the treatments for respiratory distress syndrome

Answer 40

glucocorticoid treatment accelerates fetal lung development and surfactant production surfactant therapy - natural/artificial replacement - use surfactant A and B proteins)

Question 41

what is surfactant protein B deficiency

Answer 41

autosomal recessive loss of surf pros B which is fatal and need replacement therapy