Embryology 2 Flashcards
How does the embryo fold to form the gut tube?
amniotic cavity folds down and yolk
Where does the lung tube come from?
the gut tube - endoderm
Where does the cartilage, connective tissue and muscle derive from?
splanchnic mesoderm
What is the name of the outpouching of the foregut and when does it further develop?
respiratory diverticulum on the front. develops into lung buds at week 4
What splits the foregut oesophagus and the trachea?
tracheoesophageal ridge
What happens at week 5?
bronchial buds form.
What happens at week 6?
6 - right bronchi forms 3 secondary bronchi and left forms 2. mesoderm covers the outer lung with pleura (somatic - parietal and splanchnic - visceral)
What happens at week 8?
bronchi grows so much that its attached to the pleura. terminal bronchioles with terminal sacs form.
How is the pleura formed?
lung bud pushes against the intraembryonic coelom.
What splits the pleural and pericardial cavities?
pleuropericardial folds. separates lungs and pericardium by forming a separate pericardial cavity
What covers the pericardial cavity?
somatic mesoderm
Which weeks are the embryonic stage and what occurs?
weeks 4-7. lung bud appears.
What weeks are the pseudoglandular stage and what occurs?
weeks 7-17. lungs develop but no respiratory part
What weeks are the canalicular stage and what occurs?
weeks 17-27. respiratory part develops. alveolar ducts form and epithelium differentiates into type I and II pneumocytes
What weeks are the saccular stage and what occurs?
weeks 27-40. alveolar sacs form and primitive alveoli and surfactant is made.
What is the postnatal period and what occurs?
32 weeks to 8 years. proliferation of alveolar sacs to alveoli.
How much of our alveoli is formed postnatally?
95%.
How is atresia and a fistula made?
these are congenital abnormalities. trachea and oesophagus don’t separate - fistula. atresia is when the oesophagus isn’t formed and is closed off
What is lung agenesis? whats the cause?
failure of a lung bud to develop or branch, causing absence of lung. could be due to insufficient no. of mesoderm cells, or teratogens
What is pulmonary hypoplasia?
incomplete development of lungs. leads to abnormally low no. or size of broncho-pulmonary segments - small lungs
How many structures form the diaphragm? what are they made from?
- made from mesoderm.
When does diaphragmatic development occur and what is it?
end of 5th week. separates thoracic and abdominal cavity
What 4 parts fuse to form the diaphragm?
septum transversarium, pleuroperitoneal fold, oesophagus mesentery and muscular ingrowth from body wall
What does the septum transversarium form?
the central tendon of the diaphragm
What may lead to a hiatal hernia?
incomplete closing of diaphragm during development. organs may protrude
What is a diaphragmatic hernia?
gap in diaphragm. small intestine can enter left chest and push heart and lungs to the right. liver can push into chest, causing pulmonary hypo-plasia (small lungs)
What embryological structure forms the superior surface of the diaphragm?
parietal pleura, so somatic lateral plate mesoderm
