Embryology of respiratory system Flashcards
Summary of the development of the respiratory system
Lung bud appears at week 4 from endoderm;
Week 4- 6 ; lung bud > trachea > bronchi > secondary bronchi > tertiary bronchi ; lungs grow into the pericardioperitoneal cavity
Connective tissue, pleura , muscles and cartilage of respiratory system comes from the …
Splanchnic mesoderm
Describe the pseudoglandular stage of lung maturation
Pseudoglandular ; 5-16 weeks, terminal bronchioles form (only components needed for gas exchange haven’t formed yet) ; pleuropericardial folds separate lungs from heart
Explain the relationship between the heart and lungs
Lobular and segmental veins → left pulmonary veins → oxygenated blood into LHS of heart → pumped out via aorta
deoxygenated blood enters RHS of heart via vena cava → pumped out via pulmonary artery → pulmonary artery branches into left and right versions via the pulmonary trunk
Epithelium and glands of trachea/pulmonary epithelium arise from the …
Endoderm
Describe the formation of the diaphragm
Septum transversal
Describe the canicular stage of lung formation
canalicular ; 16-26 weeks, vascularisation and further branching of terminal bronchioles into alveolar ducts ; initial formation of type 1 pneumocytes
Describe the terminal sac stage of lung formation
terminal sac ; 26 weeks to birth, epithelial cells of terminal sacs become flat and thin (type 1 alveolar epithelial cells) , capillaries come into close contact with the epithelial cells , type II alveolar cells form
Describe the alveolar stage of lung formation
alveolar ; 8 months pregnancy - childhood , increased surfactant production , few alveoli fully mature before birth , primordial alveoli continue maturing
The embryonic diaphragm is derived from 4 sites
name them
Septum transversum - located between the heart and liver ; goes on to form the central tendon
pleuroperitoneal membranes - forms the posteror and lateral parts of diaphragm
dorsal oesopheageal mesentery - forms the crura
body wall ; forms the peripheral parts of the diagram
Respiratory distress syndrome
what is it
causes
symptoms
treatment
Insufficient surfactant has been produced
high surface tension at air-blood interface
risk of alveoli collapsing during expiration
symptoms - rapid, laboured breathing
treatment - artificial surfactant/ glucocorticoids to stimulate surfactant prinduction
What is oesophagela atresia and tracheoesophageal fistulas ?
what are the problems they may cause ?
Abnormal separation of the oesophagus and trachea
atresia refers to the narrowing of oesophagus or trachea
fistula refers to an abnormal opening
this may lead to excessive amounts of fluid in respiratory tract ; gastric contents may reflux into trachea = coughing or choking or pneumonia
What are congenital cysts of the lungs?
what are the problems they may pose ?
occur when terminal bronchi are abnormallly dilated
usually at lung periphery
problems - poor drainage ; chronic lung infection
What is a congenital diaphragmatic hernia
Occur when pleuroperitoneal membrane fails to fuse with the other 3 components
most cases on left side
Leads to spilling of abdominal contents into the pleural cavity and compression of lungs ; hypo plasma of lungs