Embryology of the reparatory system Flashcards
what is the point of transition between the upper and respiratory tract
the larynx
what are the structures of the upper respiratory tract
nasal cavities
nasopharynx
oropharynx
(larynx)
what are the structures of the lower respiratory pathway
(larynx) trachea bronchi bronchioles terminal bronchioles respiratory bronchioles alveolar ducts a sacs alveoli
where does the respiratory portion start
reparatory bronchioles - alveoli
which germ layer produces the inner epithelia and the connective structures of the lungs
inner epithelia - endoderm
connective structure - mesoderm
which part of the gut tube does the respiratory diverticulum develop from
foregut in week 4
which day does the respiratory diverticulum appear
lung buds develop day 22
what direction do the lung buds grow
ventrocaudally
what separates the reparatory diverticulum from the oesophagus (foregut)
tracheosophageal ridges (except laryngeal inlet)
what is the orientation of the oesophagus and the trachea
trachea is anterior to the oesophagus
what is a fistula
an abnormal communication
what are the two types of malformations in development of the lungs
atresia with fistula 85-90%
fistula
why do malformations occur
incomplete division of foregut into oesophageal and respiratory proteins
what is an atresia
proximal closing off of the oesophagus
what is tracheoesophageal fistula with oesophageal atresia and what are the problems associated with it
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
what is H type tracheoesphaogeal fistula
communication between oesophagus and trachea
approx 4% of cases
milk goes into respiratory system and causes infection
TOF are usually associated with other congenital abnormalities what are they
V - vertebral defects A - anal atresia (C) - cardiac defects T - tracheooseophageal fistulas E - Esophageal atresia R - Renal abnormalities (L) - limb defects
what happens in week 5 to the lungs
further growth and differentiation - formation of main bronchi and secondary bronchi (day 30)
3 on the right and 2 on the left
what happens to development during the 6th week
tertiary bronchi - which each supply a bronchopulmonary segment
10 right and 8 left
branching stages are different during development
what occurs at week 16
26
36
terminal bronchioles - 16
respiratori bronchioles - 26 (poor gas exchange can occur)
alveoli - 36
what forms from the visceral mesoderm
cartilage, smooth muscle, connective tissue capillaries and visceral mesoderm
what are the two formations of the pleura
visceral mesoderm - visceral pleura
parietal mesoderm - parietal pleura
lateral plate of the mesoderm forms the pleura
what is pulmonary agenesis
failure for lung to form properly
occurs when lung bud fails to split causing complete absence of bronchi and vasculature
what is the clinical presentation of pulmonary agenesis
child usually develops respiratory distress
remaining lung is compromised - usually lower respiratory tract infection
common with vertebra for rib anomalies
what can happen to the lung in unilateral pulmonary agenesis
enlarge
what is pulmonary hypoplasia
incomplete development of the lungs
severity determines extent of development
may be found in association with congenital diaphragmatic hernia
what is branching morphogenesis
produce azygous lobe (extra lobe) - little functional difference
what are the four periods of maturation of the lungs
(embryonic) pseudoglandular canalicular saccular/terminal sac alveolar there is overlap between the stages
what week does surfactant start to get produced
around the 25/26th week
what is the difference in weeks of the embryonic and the fetal period
embryonic - 2-8 weeks
fetal - 8-38 weeks
what happens during the pseudoglandular period and what is the rough time span of the period
5-17 weeks
branching of the respiratory tree has occurred to form terminal bronchioles (respiration still cannot occur - still part of the conduction pathway)
what happens during the canalicular period and what is the rough time span
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
what is the rough time span of the terminal sac/ saccular period and what occurs
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
what does the epithelium differentiate into and in what period
saccular period - divides into type 1 neumocytes where gas exchange occurs
types 2 pneumocytes where surfactant is produced
what is most likely to happen to a fetus born prematurely at 24 week s
respiratory distress syndrome
what is the alveolar period
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
what happens to the lungs during birth
breathing starts in utero to remove amniotic fluid - kick starts respiration in muscles
remaining lung fluid is rapidly absorbed into capillaries
what is the prime factor in prognosis if child is born prematurely
development of the lungs
what is respiratory distress syndrome
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)
what are the treatments for respiratory distress syndrome
glucocorticoid treatment accelerates fetal lung development and surfactant production
surfactant therapy - natural/artificial replacement - use surfactant A and B proteins)
what is surfactant protein B deficiency
autosomal recessive loss of surf pros B which is fatal and need replacement therapy
