CP Respiratory System Embryology Flashcards
What pharyngeal arch develops into the lungs?
Sixth pharyngeal arch
What layer gives rise to the cartilage, smooth muscle, and connective tissue of the respiratory system?
Splanchnic mesoderm
In what week is the laryngotracheal diverticulum forming?
4th week
During what week do the tracheoesophageal septa close, forming the trachea and esophagus?
5th week
What embryological structure gives rise to the laryngeal cartilage?
Neural crest cells
What swellings of neural crest cells become the laryngeal cartilages?
Arytenoid swellings
In what week does recanalization complete?
By the 10th week
What eminence gives rise to the epiglottis?
Hypobranchial / Hypopharyngial eminence
What defect is caused by a failure of recanalization?
Laryngeal atresia
What are 85% of cases of tracheoesophageal fistulae associated with?
Esophageal atresia
In what stage of lung development do we start to see respiratory bronchiole?
Canalicular Stage
What weeks make up the canallicular stage?
Week 16 - 25
What weeks make up the terminal sac stage?
24 weeks to Birth
What weeks make up the alveolar stage
32 weeks to 8 years
When do we see surfactant being produced?
Terminal stage
What issue makes pulmonary hypoplasia significantly more likely?
Oligohydramnios before 26 weeks
What are the steps to make the tracheoesophageal septum?
foregut endoderm from PA 6 becomes the laryngotracheal groove
the groove becomes the laryngeotracheal diverticulum
the diverticulum becomes the tracheoesophageal folds
the folds become the tracheoesophageal septum
What forms the glottis?
bilateral arytenoid swellings made from
endoderm covering neural crest cells
The hypopharyngeal eminence comes from the
foregut endoderm from PA 3 and 4
describe proliferation and recanalization of the larynx
endodermal proliferation closes off the glottis
recanalization (apoptosis re-opening the larynx) occurs by week 10
forms vocal and vestibular folds
Trachea endoderm forms what?
splanchnic mesoderm of the trachea forms what?
epithelium and glands of the lungs
cartilage, BV, CT
What is the pseudoglandular stage?
wk 5-17
terminal bronchioles and capillaries formed but no interaction
no survival
What is the canalicular stage
wk 16-25
respiratory bronchioles and primitive alveoli present
+/- survival, more optimistic towards the 25wk mark
What is the saccular stage?
wk 24-birth
type 1 and 2 pneumocytes form
surfactant produced
survival much higher
What is the alveolar stage?
wk 32-8yrs old
mature alveoli
susceptible to lung damage (ex. secondhand smoke)
What are fetal breathing movements and how are they related to oligohydramnios?
FBM: priming lungs for respiration outside of womb. AKA practice breathing
inhale amniotic fluid, helps form thoracic space and recycles amniotic fluid
oligohydramnios (too little fluid) can lead to pulmonary hypoplasia (lungs weren’t able to form well because they couldn’t perform FBM)
more likely with oligo before 26wks
What is Laryngeal Atresia?
failure of recanalization
associated with CHAOS syndrome
dilated airways, lungs enlarged and fluid filled, diaphragm flat/inverted, ascites and/or hydrops
tx: endoscopic dilation of laryngeal web
What is the cause of tracheoesophageal fistulae?
What are the s/s?
failure of foregut to proliferated rapidly enough in relation to the rest of the embryo
unable to swallow, lots of drooling, regurgitation, may have reflux into trachea and lungs via fistula
associated with polyhydramnios (too much fluid) because it cannot be swallowed effectively by fetus
Pulmonary agenesis
unilateral-absence of a lung or lobe
bilateral=nonviable fetus
What is Potter’s Sequence
caused by severe oligohydramnios, resulting in stillborn baby with limb hypoplasia, Potter’s facies, nasal flaring, wide bridge, renal failure
can be associated with renal agenesis
Respiratory Distress Syndrome
rapid, labored breathing, seen rarely, but often cause of death in premature infants
deficient surfactant is typically the cause
glassy membrane on xray of lungs
s/s tachypnea, retractions, cyanosis
Congenital Lung Cysts
filled with fluid/air
thought to be formed by dilation of terminal bronchi later in fetal life
s/s wheezing, cyanosis, diff. breathing
Describe lung development
- laryngotracheal diverticulum forms respiratory bud (4th wk)
- bud forms 1’ bronchial buds that grow laterally into pericardioperitoneal canals
- 1’ bronchial buds branch to form 2’ bronchial buds which form 3’ bronchial buds
- bronchopulmonary segments form in 7th week
(segmental bronchi + mesenchyme)
- pattern is regulated by splanchnic mesoderm
Congenital Diaphragmatic Hernia
Bowel can push up thru diaphragm and lead to pulmonary hypoplasia
caused by failure of the pleuroperitoneal membrane to form
