embryology Flashcards
Lung development occurs in
5 periods
Lung development - initial development includes
development of lung bud from distal end of respiratory diverticulum during week 4
Lung bud formation - next step
lung buds divides into 2 bronchial buds that branch off into bronchi
Lung development occurs in 5 period - periods and time
- embryonic (wk 4-7)
- Pseydogandular (wk 5-16)
- Canalicular (wk 16-26)
- Saccular (wk 26-birth)
- Alveolar (wk 32-8 yrs)
Lung development - embryonic stage time and events
wk4-7 Lung bud (divides into 2 bronchial buds that branch off into bronchi) --> trachea --> mainstem bronchi --> secondry (lobar) bronchi --> tertiary (segmantal) bronchi
Lung development - Pseudoglandular stage time and events
wk 5-16
Endodermal tubules –> terminal bronchioles
Surrounded by modest capillary network
Lung development - Canalicular stage time and events
wk 16-26
terminal bronchioles –> respiratory bronchioles –> alveolar ducts
Surrounded by prominent capillary network
(AIRWAYS INCREASE IN DIAMETER)
Lung development - Saccular stage time and events
wk 26-birth
- Alveolar ducts –> terminal sacs
- Terminal sacs separated by 1ry septae
- Pneumonocytes develop
Lung development - Alveolar stage time and events
wk32-8yrs
- Terminal sacs –> adult alveoli (due to 2ry septation)
breathing in utero vs breathing at birth
- utero –> via aspirattion and expulsion of amniotic fluid
- -> increased vascular resistance through gestation - birth –> fluids get replaced with air –> decreased in pulmonary vascular resistance
number of aveoli according to according to age
at birth 20-70 milion
8 years 300-400 milion
Surfactant synthesis - time
begins around week 26 of gestation, but mature levels are not achieved until arround week 35 (peak at 1 wk after birth)
Screening test for fetal lung maturity
- lecithin/sphingomyelin ration in amniotic fluid –>
- if more than 2 –> healthy
- if less than 1.5 –> predictive of NRDAS - foam stability test
- surfactant/albumin ratio
tracheoesophangeal fistula - errors at … (time)
Embryonic stage of lung development (wk4-7)
lung development - respiration capable at
25 wks
Respiration at pseudoglandular stage of lung development
impossible –> incompatible with life
Congenital lung malformations
- Pulmonary hypoplasia
2. Bronchogenic cysts
Pulmonary hypoplasia - definition
Poorly developed bronchial tree with abnormal histlogy with involving right lung
Pulmonary hypoplasia - Poorly developed bronchial tree with abnormal histlogy with involving
right lung
Pulmonary hypoplasia is associated with
- congenital diaphragmatic hernia
2. bilateral renal agenesis (Potter sequence)
Bronchogenic cysts - is caused by (and clinical presentation)
abnormal budding of the foregut and dilation of terminal or large bronchi –> drain poorly and cause chronic infection
Bronchogenic cysts - appearance
Discrete, round, shaprly defined and air-filled densities on CXR
Bronchogenic cysts - clinical presentation
drain poorly and cause chronic infection
Lung development - stages, time, mechanism (all)
- embryonic (wk 4-7) –> Lung bud (divides into 2 bronchial buds that branch off into bronchi) –> trachea –> mainstem bronchi –> secondry (lobar) bronchi –> tertiary (segmantal) bronchi
- Pseydogandular (wk 5-16) –> Endodermal tubules –> terminal bronchioles. Surrounded by modest capillary network
- Canalicular (wk 16-26) –> terminal bronchioles –> respiratory bronchioles –> alveolar ducts
Surrounded by prominent capillary network - Saccular (wk 26-birth) –> - Alveolar ducts –> terminal sacs. Terminal sacs separated by 1ry septae. Pneumonocytes develop
- Alveolar (wk 32-8 yrs) –> Terminal sacs –> adult alveoli (due to 2ry septation)
Neonatal respiratory distress syndrome - mechanism/CXR/risk factors/Complications
surfactant deficinecy –> increased surface tension –> alveolar colapse
CXR: ground glass appearance of fields
RF: preamturity, maternal diabetes, C section delivery
Complications: metabolic acidosis, PDA,necrotizing enterocolitis
treatment: maternal sterid before birth, artificial surfactant for infant
