Embryology of the Respiratory System Flashcards
How does development of the LRT begin?
It begins as a respiratory diverticulum (laryngotracheal diverticulum) from ventral surface of laryngopharynx (foregut) during 4th week.
Origin of LRT epithelium
Endoderm
What aspects of LRT is derived from mesoderm?
CT, cartilage and muscles.
How does the larynx, trachea and primary bronchi form?
- The oesophagotracheal ridges fuse to form oesophagotracheal septum, which separates the trache from the oeseophagus.
- The larynx remains in communication with laryngopharynx at laryngeal orifice (aditus).
- Branching begins - primaru bronchial buds (lung buds).
Problems with oesophagotracheal ridge/septum
Results in oesophageal atresia and/or tracheoesophageal fistula.
Most common form is proximal oesophageal atresia with distal tracheosophageal fistula.
Less commonly, atresia only, fistula only, or distal atresia with proximal fistula.
Draw a proximal oesophageal atresia with distal tracheoesopageal fistula.
Pharyngeal arches
Mesenchyme swellings of pharynx
Pharyngeal clefts
Also known as pharyngeal ‘grooves’: ectoderm, external surface between pharyngeal arches.
Pharyngeal pouches
Endoderm, internal surfaces between pharyngeal arches.
What gives rise to the caritlages and muscles of larynx?
Pharyngeal arches 4 and 6 (mesenchyme)
Development of the lungs
Primary bronchial buds (lung buds) divide repeatedly
- Secondary: lobar bronchi (week five)
- Tertiary: segmental bronchi (week six)
- Further branching week six onwards.
Bronchial branching abnormalities
Epithelial (endoderm): mesenchymal (mesoderm) interactions direct branching morphogenesis.
- Agenesis: lung fails to develop
- Aplasia: some rudemintary bronchi
- Hypoplasia: insufficient branching and development.
What occurs in week 5-16 of bronchial development?
Several bronchi generations, several bronchiole generations, to terminal bronchioles.
_The conducting zone is established. _
Respiratory zone development period
Weeks 16-28 is the initial development of the respiratory zone.
What occurs during respiratory zone development?
The terminal bronchioles divide into respiratory bronchioles, which divide into terminal sacs (future alveoli).