Developmental Aspects of Lung Disease COPY Flashcards
Stages of lung development
- Embryonic 3 - 8 weeks
- Psuedo-glandular 5 - 17 weeks
- Canalicular 16 - 26 weeks
- Saccular (forms acceni) - 24 - 38 weeks
- Alveolar (36 weeks - 2-3 years)
Where do the lungs develop from?
Primitive foregut
What are the lung tubes filled with when developing?
Liquid
Lung lobes
3 on right
2 on left
What happens in psuedoglandular stage?
Get lobes
21 branches of original trachea
Fluid secreting
Tracheal cartilage tissue
Blood vessels far away from tubes - gas exchange not possible
What happens in canicular stage?
Cuboidal epithelium
Blood vessels close to tubes - gas exchange just becoming possible
Airway thinner and more sponge like
What happens in saccular stage?
More and more saccules
What happens in alveolar stage?
Saccules develop into alveoli
Thin walled, very few cells
Post natal lung growth
Alveolar separation continues
Increased alveolar dimensions
Functional changes in lungs at birth
Change from fluid secretion to fluid absorption (first few breaths of life)
Pulmonary vasodilation
What is surfactant?
Detergent - phospholipids and lipophilic proteins
Function of surfactant
Stabilises alveoli and promotes gas exchange
When do surfactant proteins appear?
12 - 14 weeks
What produces surfactant?
Type II pneumocytes
(Lamellar bodies)
Congenital abnormalities from embryonic development stage
Tracheal, laryngeal stenosis
Pulmonary agenesis
Tracheo oesophageal fistula
What is pulmonary agenesis?
Incomplete development of the lungs
What is a tacheo oesophageal fistula?
Abnormal connection between the trachea and the oesophagus
What congenital abnormalities can occur in the pseudoglandular stage of development?
Pulmonary sequestration (bits of the lung are not attached to the pulmonary arterial circulation so fail to function properly)
Cyst formation
Cystadenomatoid malformation
Types of pulmonary sequestration
Extralobar
Intralobar
What is cystadenomatoid malformation?
Similar to pulmonary sequestration, however an entire lobe of lung is replaced by a non working cystic piece of abnormal lung tissue
When does closure of diaphragm develop?
18 weeks
Diaphragmatic abnormalities
Diaphragmatic hernia
Pulmonary hypoplasia
Persistent pulmonary HTN
Eventration
Where is a diaphragmatic hernia most common?
Left lung
Features of pulmonary hypoplasia
Incomplete development of lungs
Heart pushed into right side of chest and bowel migrates into chest
Lung on that side is really underdeveloped
Features of persistent pulmonary HTN of the newborn
Failure of normal circulatory transition that occurs after birth.
Causes hypoxemia secondary to R to L shunting of blood
What is eventration?
Area less tense so the diaphragm bulks into the thoracic cavity
What is the commonest situation to go wrong with the lungs at birth?
Transient tachypnoea of the newborn
What does surfactant deficiency at birth lead to?
Hyaline membrane disease - respiratory distress syndrome (RDS)
Pathology of RDS
Less surfactant and so the smaller alveoli collapse into the larger ones
Treatment of RDS
Antenatal glucocorticoids
Surfactant replacement (lasts a day or two until baby produces own)
Oxygen
CPAP
Mechanical ventilation
How to antenatal glucocorticoids work in RDS?
Can rapidly mature the foetus cells to produce surfactant earlier and so have surfactant by the time they are born
What does CPAP stand for?
Continuous positive airway pressure
Examples of chronic neonatal lung disease
BPD
CLPD
Antenatal risk factors for COPD
In utero nicotine exposure
Nutrition
LBW / prematurity
Micronutrients/vitamins
Post natal risk factors for COPD
Infection (barker hypothesis)
Growth
Environmental tobacco smoke (+/- a1 AT deficiency)
Environmental pollution
Micronutrients/vitamins
Can nicotine cross the placenta?
Yes
What is airway remodelling?
Structural changes that occur in both small and large airways relevant to miscellaneous diseases including asthma
