L24: Development Of Respiratory System Flashcards
Developement of upper and lower respiratory system
Upper:
- division of stomodeum by palate —> nasal + oral component
Lower: (begin at 4th week)
- Pleural cavity creation
- Airway branching
Pleural cavity
Lateral mesoderm —> intraembryonic coelom (cavity)
Branching of airway
Formed from gut tube Endoderm / endoderm at caudal end of pharynx
—> Ventral part of pharynx outgrowth (later become laryngeal inlet)
—> laryngotracheal groove
—> laryngotracheal diverticulum (pouch-like)
—> tracheoesophageal fold (folds fused —> separate ventral laryngotracheal tube from dorsal oropharynx + oesophagus)
—> trachea
—> 2 bronchial buds / lung buds
Abnormal separation of tracheoesophageal fold
Tracheoesophageal:
- Fistulas (abnormal connection)
- Atresia (abnormal narrowing / absence of opening)
Coelomic cavity forms:
- Pleura
- Pericardium
- Peritoneum
Pleural and pericardial cavities separated by pleuro-pericardial folds (future mediastinal pleura)
Pleural and peritoneal cavities separated by
- septum transversum (anterior diaphragm)
- pleuro-peritoneal membranes (posterior diaphragm)
Expansion of lung buds
中間:
- Pleural and Pericardial cavities separated by pleuro-pericardial folds (future mediastinal pleura: 包住個心)
- Pleural and Peritoneal cavities separated by
1. septum transversum (anterior diaphragm)
2. pleuro-peritoneal membranes (posterior diaphragm)
肺兩側:
- Lung buds grow toward pericardio-peritoneal canal (pleural canal)
—> pericardio-peritoneal folds fuse to form Pleural and Peritoneal cavity
Formation of diaphragm
Pleuroperitoneal folds appear (5th week)
—> fuse with septum transversum (7th week)
—> muscular ingrowth from body wall forms peripheral part of diaphragm
Development of trachea and bronchi
Endoderm of laryngotracheal tube
—> respiratory epithelium + glands
Laryngotracheal diverticulum
—> main bronchi
—> secondary (future lung lobes)+ tertiary bronchi (future bronchopulmonary segment) (continue to divide for 23-30 generations)
—> 18th division —> accessory lobes (左二右三)
—> terminates in alveoli (1/6 of adult alveoli present at birth)
Lung lobes
Left:
- Upper lobe (superior + lingular division)
- Lower lobe
Right:
- Upper lobe
- Middle lobe
- Lower lobe
Maturation of lungs (4 stages)
- Pseudoglandular period (5-17 week)
- Tall columnar epithelium - Canalicular period (16-25 week)
- canaliculi branch out of the terminal bronchioli
—> lined by Cuboidal cells
—> proper respiratory part of the lungs (pulmonary parenchyma)
—> air spaces that derive from a terminal bronchiolus form an acinus
—> comprises respiratory bronchioli and alveolar ducts - Terminal sac period (24 week - birth)
- cuboidal cells become very thin (thin simple squamous epithelium) and in close contact with blood + lymph vessels - Alveolar period (32 week - 8 years)
- rapid growth and maturation
- number of respiratory bronchioles and primitive alveoli increase
- differentiation into type I and type II pneumocytes
Overview for development of lower airway
- Pleural cavity formation (4-7 week)
- Development of airway (4-7 week)
- Maturation of lung / Alveoli differentiation / surrounding mesenchyme becomes highly vascular (7 week - birth)
Clearance of amniotic fluid from the lung due to aspiration
- Expulsion by pressure on the thorax during delivery
- Fluid enters lung capillaries
- Passing into lymph vessels
Congenital malformation
- Tracheoesophageal fistula
- Tracheoesophageal atresia
- Respiratory distress syndrome
- insufficient surfactant by type II pneumocyte
- collapse of alveoli
—> hyaline membrane disease - Congenital diaphragmatic hernia
- failure of pleuroperitoneal membrane / fold to grow across the intraembryonic coelom
—> hole mainly on left side
—> abdominal contents enter thoracic cavity
—> pulmonary hypoplasia
