Developmental Aspects of Lung Disease Flashcards
What are the five stages of the embryological development of the lungs?
- Embyronic (3-8 weeks)
- Pseudoglandular (5-17 weeks)
- Canalicular (16-26 weeks)
- Saccular (24-38 weeks)
- Alveolar (36 weeks - 2/3 years)
What occurs in the embyronic phase of lung development?
Laryngeal tracheal groove comes off primitive foregut and grows into surrounding mesoderm
Later divides to form 2 lung buds
Eventually these branch out form Bvs
Filled with fluid
What occurs in the pseudoglandular phase of lung development?
Moving and budding out to form primitive lung with a few branches
Tracheal cartilage begins to form
Lobe formation
Primitive airway with columnar epithelium
Starting to get myofibroblasts around outside
Branching off into primitive tubules
BVs still too far away from tubules for exchange
What occurs in the canalicular phase of lung development?
More branches form
Primitive sacs
Acini filling so forming more squamous rather than cuboidal epithelium
Capillaries close enough for gas exchange
What occurs in the saccular phase of lung development?
More and more saccules form
More acini form and bud off to become alveoli
What occurs in the aveolar phase of lung development?
Thin walled sacs with few cells bud off resp tract
What is tracheal/laryngeal stenosis?
Narrowing of lumen due to failure to recanalise
What is pulmonary agenesis?
Failure of development of 1 lung bud = only 1 lung
What is pulmonary sequestration?
Piece of tissue develops into lung but is not attached to pulmonary arterial blood supply and so does not contribute to respiration
What are the two types of pulmonary sequestration?
Extralobar - extra lung that has its own pleural sac
Intralobar - usually within visceral pleura of normal lung tissue
What is cystadenomastoid malformation?
Malformation of the airways, some associated with cystic areas and adenomatous overgrowth of terminal bronchioles
On what side is diaphragmatic hernia most common?
L (liver plugs on R side)
What is congenital diaphragmatic hernia?
Herniation of abdominal viscera into the chest cavity due to incomplete formation of the diaphragm
What can congenital diaphragmatic hernia lead to?
Pulmonary hypoplasia (incomplete lung development) and HTN –> respiratory distress shortly after birth
What is the pathophysiology of congenital diaphragmatic hernia?
Failure of pleuroperitoneal canal to close completely
What is eventration of the diaphragm?
Abnormal elevation of part/all of an otherwise normal diaphragm into the chest cavity
What functional changes occur in the lungs at birth?
Fluid secretion –> fluid absorption
Pulmonary vasodilation to allow gas exchange
What is the commonest cause of respiratory distress in the newborn period?
Transient tachypnoea of the newborn
What causes TTN?
Delayed resorption of fluid in the lungs
What is a RF for TTN?
C-section (as fluid is not squeezed out during passage through birth canal)
Prematurity
What might CXR should in TTN?
Hyperinflation, fluid in horizontal fissure
What is the treatment of TTN?
Supplementary oxygen
Usually settles within 1-2 days
What cells make surfactant?
Type II pneumocytes
What is surfactant deficient lung disease?
AKA RDS and hyaline membrane disease
Condition seen in premature babies due to insufficient surfactant and structural immaturity of the lungs (smaller alveoli collapse into bigger ones)
Aside from prematurity what are other RFs for surfactant deficient lung disease?
Male
Diabetic mother
C-section
2nd born of premature twins
What are clinical features of surfactant deficient lung disease?
Tachypnoea, intercostal recession, expiratory grunting and cyanosis
What is the typical CXR finding with surfactant deficient lung disease?
Ground glass appearance with an indistinct heart border
What is the management of surfactant deficient lung disease?
Prevent with corticosteroids during pregnancy to induce foetal lung maturity
Oxygen
Assisted ventilation (e.g. CPAP)
Exogenous surfactant given via endotracheal tube
