Embryology (respi) Flashcards
Stages of respi development (earliest to latest)
Embryonic
Pseudoglandular
Canalicular
Saccular
Alveolar
What is a lung bud/respiratory diverticulum?
Outpouching of developing foregut region
What is necessary for functional stability?
Separation btw developing foregut and respiratory diverticulum
Main origins for development of respi structures
Gut tube
Fn of tracheoesophageal septum?
Separates trachea and esophagus
What envelopes tracheoesophageal septum?
Mesoderm
What facilitates separation of trachea and esophagus during fetal development?
Emergence of tracheoesophageal folds
How is tracheoesophageal septum formed?
Fusing of tracheoesophageal folds in midline
What complication arises if separation doesn’t occur completely?
Fistula
How is bronchial bud formed?
Respiratory diverticulum bifurcates into right and left bud
What does the bronchial bud turn into later on during development?
Pri bronchi
When does formation of tertiary bronchi occur?
End of embryonic stage
What happens during the pseudoglandular stage?
Formation of more intricate structures of the respi sys
What is the canalicular stage?
Specialised development of respi component within lung themselves
What happens during canalicular stage?
Terminal bronchioles -> respiratory bronchioles -> alveolar ducts -> alveolar sacs
Formation of canals and widening of canals
Increased vascularisation and respi bronchioles -> influx of pulmonary capillaries
What is an acinus?
Unit consisting of terminal bronchioles, alveolar duct, terminal sac
Immature precursor to the final alveoli
Is a foetus able to survive it is born premature during the canalicular stage?
Yes, some alveoli capable of supporting gas exchange
What happens during the saccular stage?
Alveolar ducts -> alveolar sacs
Type 1 vs type 2 alveolar cells
Type 1
- flat and thin
- needed for gas exchange
Type 2
- produce surfactant -> reduce surface tension of fluid in lungs to prevent collapse of alveoli
What happens during the alveolar stage?
Proliferation and maturation of alveoli
Continuous increase in vascularisation -> increase in pulmonary capillaries surrounding each alveoli
Describe blood circulation during fetal life
Lungs filled w/ fluid -> alveoli collapsed
Pulmonary vascular resistance high
Heart has shunts to bypass lungs because fetus is receiving oxygenation from placenta
How does babies’ circulation change at birth?
Baby take breath -> lungs fill w/ air and pulmonary vascular resistance drops
- cardiac shunts close -> blood flows through lungs
Components of developing diaphragm
Somites (muscles for diaphragm), septum transversum and pleuroperitoneal folds
What happens if diaphragm is not fully formed?
Abdominal content herniate into thoracic cavity (congenital diaphragmatic hernia)
What is a fistula?
Abnormal connection btw 2 hollow spaces
What is esophageal atresia?
Narrowing/closure of adjacent esophagus
Manifestations of tracheoesophageal fistula
Failure to thrive
Aspiration/lung infection
Polyhydramnios
- fetus can’t swallow amniotic fluid -> excess amniotic fluid in womb
Signs that a baby has tracheoesophageal fistula
GIT distended w/ air -> air go into esophagus instead of trachea
Feeding tube doesn’t extend to stomach as it’s caught in proximal oesophagus
How to treat tracheoesophageal fistula?
Surgical repair
What does newborn respiratory distress syndrome/hyaline membrane disease occur?
Occurs due to insufficient surfactant production in immature lung of premature infants
Clinical features of newborn respiratory distress syndrome
Breathing in rapid and laboured manner
Indrawing of infant’s ribcage -> use of accessory respiratory muscles to generate high intrathoracic pressure to expand poorly compliant lung
Cyanosis -> blue and purple discolouration of skin
Features of an X-ray of an infant w/ respiratory distress syndrome
Decreased lung vol
Increased patchiness of lung
Management of newborn respiratory distress syndrome
Surfactant therapy
Antenatal corticosteroids -> accelerate fetal lung development and surfactant production
Continuous positive airway pressure (CPAP)
What is congenital diaphragmatic hernia?
Failure of normal closure of the pleuroperitoneal membrane
Clinical features of congenital diaphragmatic hernia
Structures displaced to one side
Scaphoid abdomen
Absent breath sounds
Management of congenital diaphragmatic hernia
Surgical repair
