Chapter 6: Developmental Disorders

Question 1

Normal length of human pregnancy and normal newborn weight?

Answer 1

1) 40 +/- 2 weeks

2) 3300 +/- 600 grams

Question 2

Gestational age of less than 37 weeks

Answer 2

prematurity

Question 3

1) Appropriate for gestational age (AGA)

OR

2) Small for gestational age (SGA)

Newborn weight <2500g

Answer 3

Low-birth-weight infants

Question 4

Deficiency of surfactant
Atelectasis
Perfused but not ventilated alveoli = hypoxia & acidosis
Leak of fibrin-rich fluid into the alveoli
Lungs are dark red and airless
Hyaline membranes line the alveolar ducts (eosinophilic, fibrin-rich, amorphous structures)
Within an hour of birth: increased respiratory effort, forceful intercostal retraction and accessory neck muscle use

Answer 4

Respiratory Distress Syndrome of Newborns

Question 5

Most common acquired gastrointestinal emergency in the neonate
Ischemia of the intestinal mucosa
Injury followed by bacterial colonization (C. difficile)
Lesion: Pseudomembranes to gangrene and perforation of the bowel

Answer 5

RDS of Neonate, necrotizing enterocolitis

Question 6

Antibody mediated hemolytic disease affecting the fetus in utero
Caused by transplacental passage of maternal antibodies to antigens expressed on fetal RBCs
Rh- mother sensitized to Rh + in first pregnancy, 2nd pregnancy with Rh + baby = DISASTER (increase in mom’s anti-Rh antibody titer)
What type of antibody? Why can it cross the placenta? Disease?

Answer 6

IgG, small enough to cross the placenta (IgM is too large, pentameric) 
Erythroblastosis fetalis (hemolytic anemia of the neonate)

Question 7

Absence of an organ coupled with persistence of the organ anlage or a rudiment
For the lung: main bronchus ends blindly in nondescript tissue composed of rudimentary ducts and connective tissue

Answer 7

Aplasia

Pulmonary aplasia

Question 8

Failure of apposed structures to fuse

Answer 8

Dysraphic anomolies

Question 9

Reduced size owing to the incomplete development of all or part of an organ

Answer 9

Hypoplasia

Question 10

Persistence of embryonic or fetal structures that should involute at certain stages of development
Example: persistent thyroglossal duct

Answer 10

Involution failures

Question 11

Defects caused by incomplete formation of a lumen, these defects were not fully established in embryogenesis
Example: esophagus

Answer 11

Atresia

Question 12

Brain contains aggregates of normally developed cells arranged into grossly visible “tubers”

Answer 12

Tuberous sclerosis (example of dysplasia)

Question 13

Focal, benign overgrowths of one or more of the mature cellular elements of a normal tissue, often with one element predominating

Answer 13

Hamartomas

Question 14

Minute or microscopic aggregates of normal tissue in aberrant locations

Answer 14

Choristomas

Question 15

Composed of phospholipids, lecithin (phosphatidylcholine, 75%), and phophatidylglycerol (10%)
Concentration of lecithin increases rapidly at the beginning of the 3rd trimester
How can the maturity of the fetal lung be assessed?

Answer 15

Pulmonary surfactant made by type 2 pneumocytes
Measure pulmonary surfactant released into amniotic fluid
Lecithin to sphingomyelin ratio above 2:1 = fetus will survive w/o developing RDS

Question 16

Most serious form of erthyroblastosis fetalis

Severe edema secondary to congestive heart failure caused by severe anemia

Answer 16

Hydrops fetalis

Question 17

Severe jaundice + neurological condition
Bile staining of the brain (basal ganglia, pontine nuclei, and dentate nuclei) in the cerebellum
Severe unconjugated hyperbilirubinemia results in injury to brain via interference of mitrochondrial fxn = loss of startle reflex and athetoid movements, lethargy, death or severe mental retardation
Why is there unconjugated bilirubin?
What is the treatment? How does it work?

Answer 17

Kernicterus aka Bilirubin encephalopathy
Bilirubin is unconjugated b/c usually related to erythroblastosis fetalis, immature liver does not have glucuronyl transferase to conjugate released heme, premature infants are more susceptible
Treatment: phototherapy, converts toxic unconjugated bilirubin into isomers that are nontoxic and excreted in the urine