NICU Flashcards
What is the order of the lung developmental stages?
Embryonic, Pseudoglandular, Canalicular, Terminal Sac ( Saccular), Alveolar/Vasculature
Mnemonic: Every physician can sing along
What is the approximate age range for the embryonic stage?
0-5 weeks ( 1st trimester)
What is the structural developments in the embryonic stage?
- lung forms from the ventral bud of the esophagus
-Asymmetric bronchi established
-Initial evidence of the 5 lobes of the lungs - Elongation and branching of proximal airway
-Pulmonary vascular development from 6th aortic arch
what are the developmental abnormalities in the embryonic stage?
-Laryngeal cleft
-Tracheal stenosis
-TE fistula
- Bronchogenic cysts
What is the approximate age range for the pseudoglandular stage?
6-16 weeks ( 2nd trimester going into 3rd trimester)
What is the structural developments in the pseudoglandular stage?
( nonrespiratory bronchioles)
-Continued branching
-By the end of this stage , all large airway bronchi up to terminal bronchi is established
-Developing broncho-pulmonary epithelium begins to produce amniotic fluid
-pneumocyte precursors become evident by end of this phase
-Vasculature of arteries and veins
-Separation of thorax and peritoneal cavity ( 7 week gestation)
What are the developmental abnormalities in the pseudoglandular stage?
-Branching abnormalities of the lung
-congenital diaphragmatic hernia
-congenital lobar emphysema
-Cystic pulmonary airway malformation
-Pulmonary lymphangiectasia
What is the approximate age range for Canalicular stage?
16-25 weeks (2nd to 3rd trimester)
What is the structural development for the canalicular stage?
(respiratory bronchioles)
-Canaliculi branch out of the terminal bronchioles
-preliminary gas exchange units
-Type II pneumocytes begin to differentiate into type I pneumocytes
-At the end of this stage, lung is viable
What are the developmental abnormalities in the canalicular stage?
-pulmonary hypoplasia
-surfactant deficiency
-Alveolar capillary dysplasia
What is the approximate age range for the Saccular (Terminal Sac)?
25-36 weeks (3rd trimester)
What is the structural developments for the Saccular/Terminal Sac?
(alveolar ducts)
-Multiple sacs form from the terminal bronchioles
-By the end of this phase, the last generation of air spaces in the bronchiole tree is completed
-Gas exchange via alveolar-capillary membrane
What are the developmental abnormalities that are in the Saccular/Terminal sac phase?
-Pulmonary hypoplasia
-Surfactant deficiency
What is the approximate age range for the alveolar phase?
36 + weeks ( until age 3 to 8 years)
What is the structural developments for the alveolar sac?
-Alveoli form from terminal endings of the alveolar sacs
-With time, alveoli increase in diameter
-Microvascular growth and vessel maturation
What are the developmental abnormalities that occur in the phase?
-Surfactant deficiency
-congenital lobar emphysema
-pulmonary HTN
what are the characteristics of type I pneumocytes?
-Shaped like fried-egg; tight junction
-spread thinly and flatly across the alveolar SURFACE (covers approx 90 % of the surface)
-Fewer number of cells in alveolar LINING
-important role in gas exchange , no gene material for surfactant
-derived from type II cells
What are the characteristics for type II pneumocytes?
-cubodial shape
-comprises approx. 10 % of alveolar surface
-greater number of cells in alveolar lining
-important role in surfactant metabolism and secretion
-progenitor to type I cells
What is the OI calculation?
FiO2 x MAP/postductal paO2 x 100
What is the origin of SP-A?
Type II mostly,also nonciliated bronchiolar cells=clara cells
-Chromosome 10
expressed early in the 3rd trimester (28-36 w)
What is the role of SP-A?
Assist in tubular myelin formation (with SP-B and calcium
-Enhances phospholipid uptake and inhibits phospholipid secretion
-Host defense: significant role of opsonization; also involved in phagocytosis and direct bacterial lysis, agglutination, reduction of viral infectivity, and modulation of inflammation
What happens in the mice with SP-A and if SP-A was deficient?
- SP-A null mice: increased lung inflammation , ineffective pulmonary clearance of organism, no tubular myelin formation
-SP-A deficient mice: some polymorphism associated with increased severity of RDS and development of chronic lung disease in preterm infants; no known mutation of human gene reported
what are the SP-A characteristics?
- 28, 32 kDa
-Most abundant
-induced by steroids
-hydrophilic
-collectin memner
What is the origin of SP-B?
Type II and clara cells
Chromosome 2
expressed at the end of the 1st trimester
What is the role of SP-B?
- critical for surfactant function
-assists with tubular myelin formation (with SP-A and calcium)
-promotes surface adsorption of phospholipids ( w SP-C)
what happens with mice that are SP-B homozygote deficient and SP-B partial deficient?
- SP-B homozygote deficient infants: severe respiratory failure soon after birth; surfactant administration is ineffective; require lung transplantation for survival; autosomal recessive inheritance
-Partial SP-B deficiency: associated with chronic interstitial lung disease in childhood
What are the characterisitcs of SP-B?
-8 kDa- final active form
-hydrophobic
-induced by steroids
What is the origin of SP-C?
Type II cells
Chromosome 8
expressed at end of 1st trimester
What is the role of SP-C ?
-Critical for surfactant function
-promotes surface adsorption of phospholipids ( with SP-B)
What role does SP-C have with mice and infants?
-SP-C null mice: minimal effect on postnatal respiratory function or survival
-SP-C deficient infants: clinical symptoms NOT evident until a few months of age; leads to interstitial lung disease; clinical variability ranging from mild respiratory symptoms to progressive respiratory failure requiring lung transplantation to survival; autosomal dominant inheritance or sporadic
what are the characteristics of SP-C?
4 kDa
final active form
hydrophobic
induced by steroids
What is the origin of SP-D?
Type II cells
also present in many nonpulmonary cells
Chromosome 10
expressed last, after early third trimester
What is the role of SP-D?
-Host defense: significant role of agglutination and reduction of viral infectivity, also involved in opsonization and modualtion of inflammation
-antioxidant
-surfactant lipid homeostasis
What are the roles of SP-D in mice and infants?
-SP-D null mice: altered surfactant homeostatis ( mice with increased alveolar surfactant pool), susceptible to viral pathogens
SP-D deficient infants: NO ASSOCIATION OF SP-D POLYMORPHISM AND RDS; no known mutations of human gene reported
