HSF 2 - Embryology: Respiratory System Development Flashcards
what is the early phase of lung development?
positioning of the lung primordium and primary lung bud formation
what is the late phase of lung development?
mechanism of bronchial branching and cytodifferentiation
how is the location of the lungs determined in the early phase?
TBX4 from the T-box transcription factor gene family; linked to increase in RA produced by adjacent mesoderm and expressed in endoderm surrounding the foregut; induces the formation, growth and continued differentiation
when does the respiratory system begin to develop? into what?
week 4, formation of laryngeotracheal diverticulum
what does the original opening of the respiratory system become? what about the surrounding mesenchyme?
laryngeal orifice; supporting cartilages
what separates the trachea from the esophagus?
dorsally by the tracheoesophageal septum
what is a tracheoesophageal fistula?
most common malformation in infants, abnormal communication between the trachea and esophagus which is caused by improper formation of tracheoesophageal septum; about 90% come with an esophageal atresia
what can misexpression of TBX4 cause?
ectopic endodermal budding and tracheoesophageal fistual
how can an esophageal atresia be diagnosed and treated?
suspected in an infant with excessive drooling that is accompanied by choking, coughing, and sneezing; when fed these infants swallow normally but cough and struggle as the fluid returns through the nose and mouth; can become cyanotic and may stop breathing as the overflow of fluid from the blind puch is aspirated the trachea and lungs; can be fixed surgically
what are the laryngotracheoesophageal clefts?
1: supraglottic interarytenoid cleft
2: partial cricoid cleft
3: total cricoid cleft
4: laryngoesophageal cleft
air can leak out of the trachea reducing air to the lungs and increasing air in the thoracic cavity
what is tracheal stenosis?
narrowing of the trachea
what happens at week 5 of development?
buds divide into 2 bronchial buds that will become the primary bronchi
what happens to the splanchnic mesoderm of the respiratory system?
differentiates into the smooth muscle, nerves, and blood vessels of the lungs
how is the pattern of branching of the lung endothelium regulated?
by the surrounding mesenchyme
as you move further into the system, what happens to resistance?
goes up
airway segment length is ….. than its diameter
never more than 3x larger
what are the different stages in lung development?
embryonic (4-7) psuedoglandular (8-16) canalicular (17-26) terminal sac (26-birth) postnatal (alveolar development)
what happens during embryonic stage of development of the lungs?
initial formation of respiratory diverticulum up to formation of all major bronchopulmonary segments, lungs grow into pleural cavities, differentiation of pleura
what happens during psuedoglandular stage of development of the lungs?
major formation and growth of duct systems within bronchopulmonary segments, no respiratory components, no gas exchange, histological structure resembles a gland, induction of vasculogenesis of pulmonary veins is thought to be mediated by vascular endothelial growth factor (VEGF), which is expressed in the epithelium of terminal buds in the human fetal lung during the late parts of this stage
what happens during canalicular stage of development of the lungs?
formation of respiratory bronchioles and terminal sacs (primitive alveoli), vascularization increases, capillaries found in walls
what happens during terminal sac stage of development of the lungs?
alveoli develop from the respiratory bronchioles, epithelium lining alveoli differentiates into 2 cell types
what happens during postnatal stage of development of the lungs?
up to 90% of alveoli can be formed, primary mechanism is septation of pre-existing alveoli
how do ectopic lung lobes form?
from additional respiratory buds of the foregut or from misexpression of TBX4 or FGF10
what is atelectasis?
incomplete expansion or collapse of parts of or a whole lung
