Respiratory development Flashcards
Laryngotracheal groove develops from what?
Ventral wall of primitive pharynx caudal to 4th pair of pharyngeal pouches.
What does the laryngotracheal groove deepen to form?
Respiratory diverticulum
What respiratory structures develop from the endoderm?
Epithelium, glands of larynx, trachea, bronchi, pulmonary epithelium
What respiratory structures develop from the splanchnic mesenchyme of foregut?
Connective tissue, cartilage, smooth muscle
Laryngeal cartilages develop from what?
Cartilages of 4th and 6th pharyngeal arches
What do the 4th and 6th pharyngeal arches develop from?
Mesenchyme derived from NEURAL CREST CELLS
What do laryngeal muscles develop from?
Myoblasts of 4th and 6th pairs of pharyngeal arches
What nerves innervate laryngeal muscles?
Superior laryngeal (sensory above vocal cord) and recurrent laryngeal (sensory below and all motor) Origin: vagus nerve
What gives rise to epiglottis?
Hypobranchial eminence
What is larynx epithelial lining derived from?
Endoderm
What is the trachea formed from?
Laryngotracheal tube distal to larynx
What parts of trachea are of endodermal origin?
Tracheal glands (develop from ingrowth of surface epithelium)
What parts of trachea are derived from splanchnic mesoderm?
Cartilage, connective tissue, muscles
Tracheoesophageal fistula
–Abnormal communication (fistula) between trachea and esophagus
What is the most common anomaly of lower respiratory tract?
Tracheoesophageal fistula
What is tracheoesophageal fistula commonly associated with?
Esophageal atresia
What is esophageal atresia?
Blind-ended esophagus
What causes tracheoesophageal fistula?
Abnormal partitioning between tracheoesophageal septum causing abnormal communication between trachea and esophagus
How can pneumonia or pneumonitis occur from tracheoesophageal fistula?
Food or gastric contents may enter lungs
How can polyhydramnios occur from tracheoesophageal fistula?
Amniotic fluid accumulates because amniotic fluid can’t pass to stomach and intestines for absorption and transfer via placenta to mother’s blood
How do bronchopulmonary segments develop?
Laryngotracheal groove–> respiratory diverticulum –> tracheal bud –> primary bronchial buds –> secondary bronchial buds –> segmental branches
What do primary bronchial buds grow into?
Pericardioperitoneal canals
What are epithelium and bronchial glands derived from?
Endoderm
What parts of bronchi are derived from splanchnic mesoderm?
Cartilaginous plates, bronchial smooth muscle, connective tissue, pulmonary connective tissue and capillaries
What is the visceral pleura derived from?
Splanchnic mesoderm
What is the parietal pleura derived from?
Somatic mesoderm
Azygous lobe
Part of superior lobe of right lung that grows medial to azygos vein instead of lateral to it
Agenesis of lungs
Failure of bronchial bud to develop can be unilateral or bilateral
What is lung hypoplasia typically associated with (2 different things)?
Congenital diaphragmatic hernia or oligohydramnios
Potter syndrome
Pulmonary hypoplasia, bilateral renal agenesis, caused by oligohydramnios
How can oligohydramnios cause pulmonary hypoplasia?
Uterine wall compresses fetal thorax causing lung hypoplasia
What can cause oligohydramnios?
Bilateral renal agenesis causes lack of urine production and reduces amount of amniotic fluid present
Four stages of lung maturation
- Pseudoglandular period
- Canalicular period
- Terminal sac period
- Alveolar period
Pseudoglandular period
- -6-16 wks
- -Ductal elements (bronchi and terminal bronchioles) of lung development
- -No alveoli present
Canalicular period
- -16-26 weeks
- -Bronchi and terminal bronchioles enlarge and respiratory bronchioles and alveolar ducts develop
- -Vascularization
- -Respiration is possible because of developing alveoli
What direction do respiratory and alveolar ducts develop from?
Cranial to caudally
Terminal sac period
- -26 wks to birth
- -Type 1 alveolar cells form
- -Blood-air barrier develops
- -Type II alveolar cells start to secrete surfactant
What is infant survival dependent on in terminal sac period?
Adequate vasculature and surfactant
Type I alveolar cell origin
Squamous epithelium of endodermal origin
Type II alveolar cells
Secrete pulmonary surfactant
When does surfactant secretion begin?
Begins at 20 weeks, not sufficient until 26-28 wks.
What can accelerate surfactant production during pregnancy?
Glucocorticoids
Alveolar period
- -Late fetal period to year 8 of childhood
- -Maturation of alveoli
- -Increase respiratory bronchioles and primitive alveoli
What do fetal breathing movements do?
Stimulate lung development and facilitates development of respiratory musculature
How many alveoli are present at birth? What do they increase to by age 3? How long do we continue to develop new alveoli?
150 million. 300 million. 8 years old.
What is lung fluid in fetus derived from?
Amniotic fluid, lung tissue itself, secretions by tracheal and bronchial glands
How does removal of lung fluid occur at birth?
- Through mouth and nose by pressure on thorax during delivery
- Into pulmonary capillaries
- Into lymphatics
Congenital lung cysts
Formed by dilation of terminal bronchioles due disturbance in bronchial development during late fetal life
What do lungs with congenital lung cysts look like?
Honeycomb appearance
What accounts for 20% of all infant deaths during newborn period
Respiratory distress syndrome
Hyaline membrane disease/respiratory distress syndrome cause and location?
Deficiency of surfactant and injury to alveolar wall causing protein-rich, fibrin-rich exudate derived from injured pulmonary epithelium and circulating blood substance. Located in alveolar space and forms hyaline membrane
What is difference between newborn lungs and stillborn lungs?
Stillborn lungs sink because they contain fluid, not air. Newborn lungs contain air and float in water.
