Embryology 3 Flashcards
What are the 4 stages of lung development?
Development of trachea and lung buds
Development of pleural cavity and pleurae
Differentiation of lung buds
Development of diaphragm
When does development of the trachea and the lungs occur?
Week 4 of gestation
Define primordium
An organ or tissue in its earliest recognizable stage of development
Where does the respiratory primordium form?
Starts as a median outgrowth from the laryngotracheal groove (diverticulum) from the ventral part f the foregut
When does the diverticulum form the trachea and the lung buds?
When the diverticulum becomes covered with mesoderm on its outside and enlarges
What forms between the trachea and the oesophagus?
Oesophagotracheal septum
What is a tracheoesophageal fistula?
Fistula = an abnormal or surgically made passage between a hollow or tubular organ and the body surface, or between two hollow or tubular organs, ie. between 2 epithelialized surfaces. TOF is a common congenital abnormality.
Atresia = a condition in which an orifice or passage in
the body is (usually abnormally) closed or absent.
Where does the visceral pleura arise from?
The splanchnic mesoderm
Where does the parietal pleura arise from?
The somatic mesoderm
Where on the diagram is the splanchnic and the somatic mesoderm?
Where do the pulmonary arteries individuate?
6th aortic arch
Which part of the embry (in the embryonic period) creates the median trachea and two lateral pockets?
The respiratory diverticulum
What stages is the foetal period split into?
The pseudoglandular stage
Canalicuar stage
Saccular stage
What happens during the pseudoglandular stage?
Set up of all pulmonary structures except elements needed for gas exchange
What happens during the canalicular stage?
Terminal bronchioles give rise to tubes that form the respirtory part of the lung. Differentiation of epithelium into cuboidal secretory cells (type 2 pneumocytes) and flat type 1 pneumocytes.
What happens during the saccular stage?
Formation of alveolar sacs separated by primary septa.
These sacs are progressively divided into smaller subunits by secondary septa leading to the formation of alveoli.
What happens to alveoli during the postnatal period?
More form from the terminal sacs (95% of adult like alveoli are formed post-natally)
Alveoli enlarge
As lungs enlarge - Increase in respiratory bronchioles
What is the effect of folding of embryo during week 3?
Gives rise to the primitive gut tube, gut tube forms the endoderm
What is the name given to the congenital problem whereby there is insufficient surfactant?
Respiratory distress syndrome or hyaline membrane disease
Agenesis is another congenital condition of the lung, what is it and how does it differ from aplasia?
Agenesis refers to the failure of an organ to develop during embryonic growth and development due to the absence of primordial tissue.
Aplasia- the failure of an organ or tissue to develop or to function normally.
What is an accessory lobe?
Invaginations of the visceral pleura create accessory fissures that separate individual bronchopulmonary segments into accessory lobes
Define azygous lobe.
Congenital variation of the upper lobe of the right lung. Caused when the posterior cardinal vein, one of the precursors of the azygos vein, fails to migrate over the apex of the lung and penetrates it instead, carrying along two pleural layers that invaginates into the upper portion of the right upper lobe.
What are the four embryonic components of the diaphragm?
Where is the septum transversum originally located?
Opposite C3-C5 somites
Where does the septum transversum migrate during the development of the diaphragm?
Caudally, bringing with it spinal nerves C3-C5
What are the three major congenital defects?
Diaphragm doesn’t completely close
Herniation of abdominal contents into the chest
Pulmonary hypoplasia
What is a hernia?
Hernia is a general term used to describe a bulge or protrusion of an organ through the structure or muscle that usually contains it.
What are the names given to these hernia?
Give examples of hiatal herniae
