Respiratory Embryology Flashcards
When does the development of the respiratory system start and end
about the 4th week it begins
alveoli will continue to form through the 8th year of life
Where and how does the Respiratory system begin on the embryo
Starts as a median outgrowth known as the Laryngotracheal groove
this is found in the floor of the caudal end of the foregut
inferior to the 4th pharyngeal arches
the primordium of tracheobronchial tree will develop caudal to the 4th pharyngeal pouches
What does the Endoderm of the laryngotracheal groove give rise to
Pulmonary epithelium, and glands of larynx, trachea, and bronchi
What does the splanchnic mesoderm from the lateral plate give rise to in the respiratory system
CT, cartilage, smooth muscle in these structures and surrounds the foregut
How does the respiratory bud form
Laryngotracheal groove will evaginate to form the laryngotracheal diverticulum (lung bud)
this will then elongate and become invested with splanchnic mesenchyme
then the distal end of the laryngotracheal diverticulum will enlarge to form a globular respiratory bud (the orgin of the respiratory tree)
What is the function of the Tracheoesophageal folds and when do they develop
these tracheoesophageal folds will fuse to form the tracheoesophageal septum at the end of the 5th week
these will divide the cranial portion of the foregut
the Ventral part: becomes the laryngotracheal tube (larynx, trachea, bronchi, lungs)
the dorsal part: oropharynx, esophagus
How does the development of the larynx occur
at the laryngotracheal groove, mesenchyme produces arytenoid swellings making a T shaped laryngeal inlet
laryngeal epithelium will then proliferate and occlude the lumen, however this will recanalize at the 10th week of the embryo development
during recanalization, laryngeal ventricles will form to create the vocal folds and vestibular folds
How does the Epiglottis form and what is it in contact with in the mouth
develops from the hypopharyngeal eminence which is produced from mesenchyme of the 3rd and 4th Pharyngeal arches
in contact with the soft palate to separate the respiratory and digestive tracts
What does the Laryngeal muscles develop from and what happens to the larynx during the first two years
Laryngeal muscles develop from the Myoblasts of the 4th and 6th Pharyngeal Arches
the larynx is in a high position in the neck of the neonate and then in the first 2 years the laryngeal will descend
Laryngeal atresia
Failure of recanalization of the larynx
Obstruction of the upper fetal airway or congenital high airway obstruction syndrome (CHAOS Syndrome)
lungs filled with fluid
diaphragm flattened or inverted and there are fetal ascites or hydrops
treatment is by endoscopic dilation of the laryngeal web
Tracheosophageal fistula
an abnormal connection between the trachea and the esophagus
most common congenital anomaly of the lower respiratory tract
caused by a failure of the foregut endoderm to proliferate rapidly enough in relation to the rest of the embryo
cases usually associated with esophageal atresia: blind esophagus
cannont swallow, frequently drool, immediate regurgitation when fed
Polyhydraminos: excess amniotic fluid
- due to not transferred for disposal via the placenta
- cannot enter the stomach/intestines for absorption
How do the lungs develop
Distal end of the laryngotracheal diverticulum enlarges to form the respiratory bud in the 4th week
the bud will grow ventrocaudally and bifurcate to make the primary bronchial buds
then they will grow laterally into the pericardioperitoneal canals
when does the branching of the primary bronchial buds begin, and what dictates the branching pattern
5th week goes to the secondary bronchial buds and then to the tertiary bronchial buds
the branching patterns of the lung endoderm is regulated by the splanchnic mesenchyme
bronchopulmonary segments occur in the 7th week which is due to the segment bronchi and the mesenchyme
What is the Visceral and parietal pleura developed from
Visceral pleura: splanchnic portion of lateral plate mesenchyme
Parietal Pleura: somatic portion of lateral plate mesoderm
What are the 4 steps of the Lung Maturation and what weeks are they when they appear
Pseudoglandular: 5-7 weeks
Canalicular 16-25 weeks
Terminal Sac: 24weeks to birth
Alveolar: 32 weeks to 8 years
Lung Maturation: Pseudoglandular
Looks like exocrine glands
all major elements of the lung have formed except those involved with gas exchange
fetus cant survive
Lung Maturation: Canalicular
Overlaps pseudoglandular
Vascularization
Respiratory bronchioles
Primodial alveolar and sacs are present
+/- survival
Lung Maturation: Terminal Sac
Numerous alveoli form
thin epithelium w/increased Vascularization
- type 1 and type II pneumocytes
- lymphatic capillaries
gas exchange can occur
survivable
Lung Maturation Alveolar
Alveolocapillary membrane
primitive alveoli
form more primitive alveoli
mature alveoli
What are the three things that splanchnic mesoderm is critical in developing for the bronchi development
Cartilaginous plates
Bronchial smooth muscle and connective tissue
Pulmonary connective tissue and capillaries are aslso derived from this tissue
What year is alveolar development largely completed
3 years
what are the three ways that intra-alveolar fluid is cleared
Released from mouth/nose by pressure on the fetal thorax during vaginal delivery
pulmonary capillaries, arteries and veins
lymphatics
What are Fetal Breathing Movements
Essential for normal lung development
intermittent pattern that conditions respiratory muscles
also used during fetal monitoring and as a predictor of fetal outcome in pre term delivery
Forceful enough to cause aspiration of amniotic fluid and helps stimulate lung development
Pulmonary Agenesis
Unilateral agenesis of a complete lung or a lobe and accompanying bronchi
respiratory bud fails to split into R/L bronchial buds
