E - Development Of The Respiratory System Flashcards
How is the respiratory system split functionally?
Conducting portion and the respiratory portion
Respiratory function of the conducting portion
Warm, moisten and conveys air
Respiratory function of the respiratory portion
Gas exchange
How is the respiratory tract divided structurally
Upper and lower respiratory systems
What does the upper respiratory system consist of?
Nasal and oral cavities, pharynx and associated structures
What does the lower respiratory system consist of?
Trachea, bronchi, bronchioles, alveoli
What is the respiratory system derived from?
The primitive gut tube
What is the primitive gut tube?
The precursor to the GI tract which is endodermal derived and forms due to lateral folding of the embryo during early gestation
When and how does respiratory development start?
Week 4 - an outpocketing of of the proximal gut tube (the foregut) called the respiratory diverticulum
What begins to separate the foregut from the respiratory diverticulum to induce proper function?
The formation of a longitudinal ridge called the tracheoesophageal septum
What does the respiratory diverticulum do after the formation of the tracheoesophageal septum?
Bifurcates (forks) into the left and right primary bronchi, and proliferate to produce secondary and tertiary bronchi
What is tracheoesophageal Fistula?
Where the trachea remains continuous with the oesophagus due to abnormal formation of the tracheoesophageal septum
What are the signs of tracheoesophageal fistula within children
During feeding become cyanosed (blue/purplish skin colour due to a lack of oxygen to blood) or vomit/regurgitate food
How is tracheoesophageal fistula treated?
Surgical resection of the fistula
Weeks 8-16 of respiratory development
Pseudoglandular phase
What occurs during the pseudoglandular stage?
The ducts within the bronchopulmonary segments (the latter of which become their own portions of the lung) start to develop. Bronchiolar buds branch off from tertiary bronchi and begin to develop
Metabolism of lungs during pseudoglandular stage
Metabolically active but cannot carry out gas exchange. Therefore can derive the body of oxygen. Ductus arteriosus prevents this by shunting blood from pulmonary artery to the aortic arch
What do the lungs resemble in the pseudoglandular stage?
The development of the tubuloacinar glands
Weeks 16-26 of respiratory development
Cananalicular stage
What occurs during canalicular stage?
Respiratory bronchioles develop and bud off from the tertiary bronchioles formed in the pseudoglandular stage
Metabolism of canalicular stage
Lungs are metabolically active, but still don’t undergo gas exchange. Babies born in the canalicular stage have poor prognosis
Week 26 - birth of respiratory development
Terminal Sac stage
What happens in the terminal sac stage?
Alveoli development
What two cells do alveoli consist of?
Type I and Type Ii pneumocytes
Type I pneumocytes
Simple squamous epithelial cells - make up 90% of alveolus
Type II pneumocytes
Simple cuboidal cells - make up the remaining 10% and produce surfactant
Surfactant in the lungs is…
Amphipathic - can bind to both hydrophilic and hydrophobic molecules - in this case water and air
Surfactant function in lungs
Reduces surface tension in the alveoli, allows the alveoli in the lungs to expand at greater volumes for any given pressure
Respiratory distress syndrome
Baby is born before producing Type II pneumocytes - doesn’t produce surfactant - difficult to expand lungs and take first breath
How is Respiratory distress syndrome treated?
Mother is given glucocorticoids to stimulate surfactant production in foetus
