Where does the respiratory system begin its growth?
Median outgrowth of laryngotracheal groove
What happens to the outgrowth of laryngotracheal groove?
The groove evaginates to form the laryngotracheal diverticulum that will elongate
What forms at the distal end of the laryngotracheal diverticulum?
Respiratory bud
The respiratory bud is the origin of?
Respiratory tree
What develop to form the tracheoesophageal septum?
Tracheoesophageal folds
What do the tracheoesophageal folds cause to happen?
Splits the foregut into ventral and dorsal portions
- ventral = laryngotracheal tube
- dorsal = esophagus
What creates the pulmonary epithelium and glands of the trachea, larynx and bronchi?
Endoderm of laryngotracheal groove
What creates the cartilage, smooth muscle and CT of the trachea, larynx and bronchi?
Splanchnic lateral plate mesoderm
What pharyngeal arches contribute to larynx and laryngeal muscle development?
4 and 6
For the development of the larynx, mesenchyme produces?
Arytenoid swellings
What do the arytenoid swellings do?
Convert the primordial glottis into a T-shaped laryngeal inlet
After the arytenoid swellings for the T-shaped laryngeal inlet, what occurs to the laryngeal epithelium?
It proliferates and blocks the lumen of the larynx
Recanalization of the larynx occurs by what week?
10th
During recanalization of the larynx, what form that are bounded by mucous membranes?
Vocal and vestibular folds
In a neonate, what is the epiglottis in contact with?
Soft palate
How old is someone if their larynx is very high up?
Less than 2 years old
Laryngeal descent occurs when?
Over first 2 years of life
Laryngeal atresia
Failure of recanalization of the larynx
“CHAOS” - congenital high airway obstruction syndrome
What are the symptoms of laryngeal atresia?
Lungs enlarged and filled with fluid
Airways dilated
Diaphragm flattened
The trachea develops from?
Laryngotracheal tube
Tracheal epithelium and glands form from?
Endoderm
Tracheal cartilage, muscle and CT form from?
Splanchnic mesoderm
Tracheoesophageal Fistula
Abnormal connection between the esophagus and trachea
What causes a tracheoesophageal fistula
Foregut endoderm does not proliferate rapidly enough
Most cases of tracheoesophageal fistula include what mechanical setup?
Esophageal atresia (blind esophagus)
Symptoms of a tracheoesophageal fistula include?
Cannot swallow
Polyhydramnios - fluid cannot enter stomach for absorption
May reflux gastric contents into trachea and lungs
What does the respiratory bud create?
Bifurcates into primary bronchial buds
Primary bronchial buds grow into pericardioperitoneal canals and branch to form secondary and tertiary buds. What controls the branching pattern?
Splanchnic mesoderm
Stages of lung development
- Pseudoglandular
- Canalicular
- Terminal sac
- Alveolar
Pseudoglandular stage lung development
Weeks 5-17
All elements formed except for elements involved in gas exchange
Can a fetus survive if born during pseudglandular stage (5-17 weeks)?
NO
Canalicular stage of lung development
Weeks 16-25
Vascularization, respiratory bronchioles and primitive alveoli form
Can a fetus survive if born during canalicular stage (16-25 weeks)?
Maybe
Terminal sac stage of lung development
Weeks 24-birth
Type 1 and 2 alveolar cells present and gas exchange can occur!
Can a fetus survive if born during terminal sac stage (24weeks +)?
Yes
Alveolar stage of lung development
32 weeks - 8 years
Alveoli increase in number
When do most mature alveoli develop?
Postnatally
Lung growth involves an increase in?
NUMBER of bronchioles and alveoli
Fetal breathing movements
Intermittent pattern that conditions respiratory muscles and fills lungs with amniotic fluid for their development
At birth, the lungs require rapid replacement of the intra-alveolar fluid with air. How can this occur?
- vaginal delivery pushes fluid out mouth and nose
- arteries, veins, lymphatics
- mechanically
Pulmonary agenesis is the failure of ____ to split into right and left bronchial buds
Respiratory buds
Can pulmonary agenesis be unilateral?
Yes
Pulmonary hypoplasia
Due to restriction of fetal thorax due to uterine pressure and stunts their growth
What condition can dramatically increase the risk of pulmonary hypoplasia?
Oligohydramnios
Respiratory distress syndrome
Type 2 alveolar cells altered and cannot make surfactant!!
When will you notice respiratory distress syndrome?
Shortly after birth
What do the alveoli contain instead of surfactant with respiratory distress syndrome?
Glassy membrane fluid
Signs of respiratory distress syndrome?
Rapid, labored breathing right after birth
- grunting, cyanosis, nasal flaring