Neonatal and Pediatric Pulmonary Disease Flashcards
What are the periods of lung development up until age 20? What develops in each of these stages?
Lung bud = 4-6 weeks - up to segmental bronchi
Pseudoglandular period = 6-16 weeks - up to terminal bronchioles
Canalicular period = 16-26 weeks - up to alveolar ducts
Saccular / Alveolar period = 26 weeks to term - up to terminal sacs
Alveolar period = birth to 10 years - up to adult alveoli number
10-20 years - HYPERTROPHY of existing alveoli
What does the lung develop from and when can the lung lobes be actually distinguished? When is conduction system branching complete?
Develops from foregut endoderm
Lobes are distinguished by week 12 (pseudoglandular period), branching to terminal bronchioles is complete by week 16 (End of pseudoglandular period)
Do mucous or serous glands develop first? Why?
Mucous glands - develop around the time of the cilia so that particles can be conducted out of the airway, around 8-10 weeks
Serious glands - develop around 26 weeks (when respiration is first possible) because their function is to humidify the air
What is the order of pulmonary vasculature development?
pulmonary veins -> pulmonary arteries -> bronchial arteries (heart develops later)
4,5,7 weeks respectively
What important development happens in the canalicular stage and what cell is the precursor to type 1 and 2 pneumocytes?
Alveolar ducts develop which are lined by cuboidal cells, which are the precursor to Type 1 and 2
Important relationship is made as ducts because surrounded by a very prominent capillary network
What ratio is thought to be predictive of neonatal respiratory distress syndrome? How does this change with age?
Lecithin:sphingomyelin in amniotic fluid
Both substances are present in surfactant, but sphingomyelin remains stable while lecithin increases to make surfactant more effective
> 2 ratio indicates there will be no neonatal respiratory distress
What agents accelerate lung maturation?
Think asthma drugs / stimulants
Steroids - i.e. betamethasone Stress Thyroxine Theophylline Sympathomimetics Prolactin (increases late in pregnancy)
What agents decelerate lung maturation? Why is this relevant?
Steroid antagonists
Insulin
insulin is relevant because babies of diabetic mothers will have high insulin levels, and high risk for RDS
When does the insult occur to cause tracheo-esophageal fistula and what are the symptoms? What is the most common type?
4th week of development (lung bud stage) -> failure of separation of esophagus and lung buds
Most common type: esophageal atresia with tracheoesophageal fistula
Symptoms: choking, coughing, and vomiting on first feeding which can inflate stomach and lead to aspirations of food into airways
What can happen if there is failure of airway budding into mesenchyme at 4-8 weeks and what are the symptoms?
Absence of a Lung or Lobe
Symptoms: Generally asymptomatic, but reduced respiratory reserve in trauma or infections
What are two extra lobes of the lung which occur not uncommonly?
Azygous lobe -> right upper lung at apex
Cardiac lobe -> right lower lung
Generally asymptomatic
What is a bronchogenic cyst and its clinical significance?
Abnormal development of primitive airway buds, cysts are attached to bronchial tree via defective airway
Clinical significance:
Poor mucosal clearance, recurrent infections / pneumonia which may require surgical removal
What is the difference between a bronchogenic sequestration and cyst?
Sequestration - clinically very similar to cysts, except there is no connection to tracheobronchial tree.
Importantly:
Cyst - supplied by low pressure PULMONARY circulation
Sequestration - supplied by high pressure SYSTEMIC circulation - more difficult to remove
What is hyaline membrane disease and its pathophysiology?
Neonatal respiratory distress syndrome (RDS)
Low surfactant -> low lung compliance, atelectasis and collapse of lungs w/ increased work of breathing -> hypoxemia / respiratory acidosis -> pulmonary hypertension -> capillary endothelial damage / leak with epithelial necrosis and hyaline membrane formation
What factors make RDS more or less likely?
More likely - diabetic mothers (insulin), prematurity (prior to 30 weeks), C-section birth (less stressful for baby than uterine)
Less likely - intrauterine stress, heroin-addicted mothers
