NICU

Question 1

What is the order of the lung developmental stages?

Answer 1

Embryonic, Pseudoglandular, Canalicular, Terminal Sac ( Saccular), Alveolar/Vasculature

Mnemonic: Every physician can sing along

Question 2

What is the approximate age range for the embryonic stage?

Answer 2

0-5 weeks ( 1st trimester)

Question 3

What is the structural developments in the embryonic stage?

Answer 3

• 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

Question 4

what are the developmental abnormalities in the embryonic stage?

Answer 4

-Laryngeal cleft
-Tracheal stenosis
-TE fistula
- Bronchogenic cysts

Question 5

What is the approximate age range for the pseudoglandular stage?

Answer 5

6-16 weeks ( 2nd trimester going into 3rd trimester)

Question 6

What is the structural developments in the pseudoglandular stage?

Answer 6

( 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)

Question 7

What are the developmental abnormalities in the pseudoglandular stage?

Answer 7

-Branching abnormalities of the lung
-congenital diaphragmatic hernia
-congenital lobar emphysema
-Cystic pulmonary airway malformation
-Pulmonary lymphangiectasia

Question 8

What is the approximate age range for Canalicular stage?

Answer 8

16-25 weeks (2nd to 3rd trimester)

Question 9

What is the structural development for the canalicular stage?

Answer 9

(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

Question 10

What are the developmental abnormalities in the canalicular stage?

Answer 10

-pulmonary hypoplasia
-surfactant deficiency
-Alveolar capillary dysplasia

Question 11

What is the approximate age range for the Saccular (Terminal Sac)?

Answer 11

25-36 weeks (3rd trimester)

Question 12

What is the structural developments for the Saccular/Terminal Sac?

Answer 12

(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

Question 13

What are the developmental abnormalities that are in the Saccular/Terminal sac phase?

Answer 13

-Pulmonary hypoplasia
-Surfactant deficiency

Question 14

What is the approximate age range for the alveolar phase?

Answer 14

36 + weeks ( until age 3 to 8 years)

Question 15

What is the structural developments for the alveolar sac?

Answer 15

-Alveoli form from terminal endings of the alveolar sacs
-With time, alveoli increase in diameter
-Microvascular growth and vessel maturation

Question 16

What are the developmental abnormalities that occur in the phase?

Answer 16

-Surfactant deficiency
-congenital lobar emphysema
-pulmonary HTN

Question 17

what are the characteristics of type I pneumocytes?

Answer 17

-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

Question 18

What are the characteristics for type II pneumocytes?

Answer 18

-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

Question 19

What is the OI calculation?

Answer 19

FiO2 x MAP/postductal paO2 x 100

Question 20

What is the origin of SP-A?

Answer 20

Type II mostly,also nonciliated bronchiolar cells=clara cells
-Chromosome 10
expressed early in the 3rd trimester (28-36 w)

Question 21

What is the role of SP-A?

Answer 21

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

Question 22

What happens in the mice with SP-A and if SP-A was deficient?

Answer 22

• 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

Question 23

what are the SP-A characteristics?

Answer 23

• 28, 32 kDa
  -Most abundant
  -induced by steroids
  -hydrophilic
  -collectin memner

Question 24

What is the origin of SP-B?

Answer 24

Type II and clara cells
Chromosome 2
expressed at the end of the 1st trimester

Question 25

What is the role of SP-B?

Answer 25

- critical for surfactant function -assists with tubular myelin formation (with SP-A and calcium) -promotes surface adsorption of phospholipids ( w SP-C)

Question 26

what happens with mice that are SP-B homozygote deficient and SP-B partial deficient?

Answer 26

- 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

Question 27

What are the characterisitcs of SP-B?

Answer 27

-8 kDa- final active form -hydrophobic -induced by steroids

Question 28

What is the origin of SP-C?

Answer 28

Type II cells Chromosome 8 expressed at end of 1st trimester

Question 29

What is the role of SP-C ?

Answer 29

-Critical for surfactant function -promotes surface adsorption of phospholipids ( with SP-B)

Question 30

What role does SP-C have with mice and infants?

Answer 30

-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

Question 31

what are the characteristics of SP-C?

Answer 31

4 kDa final active form hydrophobic induced by steroids

Question 32

What is the origin of SP-D?

Answer 32

Type II cells also present in many nonpulmonary cells Chromosome 10 expressed last, after early third trimester

Question 33

What is the role of SP-D?

Answer 33

-Host defense: significant role of agglutination and reduction of viral infectivity, also involved in opsonization and modualtion of inflammation -antioxidant -surfactant lipid homeostasis

Question 34

What are the roles of SP-D in mice and infants?

Answer 34

-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