✅ EMBRIOLOGÍA del APARATO RESPIRATORIO 😙💨
Hemrology of the Respiratory System
In this section, the speaker discusses the hemrology of the respiratory system, covering topics such as pulmonary development, the origin of various respiratory structures, and the stages of lung maturation.
Formation of Tracheal Buds and Separation from Anterior Intestine
- The respiratory diverticulum emerges around four weeks in the embryo.
- This structure initially communicates with the anterior intestine.
- Crests separate it from the intestine forming tracheoesophageal ridges.
- These ridges divide into tracheoesophageal septum, separating esophagus and trachea.
Origin of Respiratory Epithelium and Musculature
- Endoderm gives rise to epithelium in larynx, trachea, bronchi, and lungs.
- Cartilaginous and muscular components come from splanchnic mesoderm surrounding anterior intestine.
- Laryngeal muscles derive from fourth and sixth pharyngeal arch mesenchyme.
- Rapid proliferation changes laryngeal opening shape to a T-form.
Development of Trachea, Bronchi, and Lungs
- Respiratory diverticulum forms trachea and primary bronchial buds.
- Primary bronchi branch into secondary bronchi forming lobes in each lung side.
- Lungs grow caudally within body cavity through pericardioperitoneal canals.
- Mesoderm becomes visceral pleura covering lungs.
Lung Maturation Phases
This part delves into four stages of lung maturation: pseudoglandular period, canalicular period, terminal sac period, and alveolar period.
Pseudoglandular Period (Weeks 5-16)
- Lung resembles an exocrine gland with endodermal tubules surrounded by mesoderm.
- Each tubule branches into terminal bronchioles; no respiration is possible during this phase.
Canalicular Period (Weeks 16-26)
- Terminal bronchioles divide into respiratory bronchioles then alveolar ducts.
- Epithelium changes to simple cuboidal; survival before week 20 is rare for premature babies.
Terminal Sac Period (Weeks 26-Birth)
- Terminal sacs emerge from alveolar ducts expanding towards surrounding mesoderm.
- Simple cuboidal epithelium differentiates into type I pneumocytes forming capillary barrier.
Alveolar Period (Birth-Eight Years)
- Sacs develop septa forming adult alveoli; significant increase in alveoli count by age eight.
El mecanismo principal por el cual ocurre el aumento es la formación de septos secundarios que dividen los alveolos existentes. Antes del nacimiento los pulmones están llenos de obliguio con alto contenido e incluiro, proteínas escasas y cierta cantidad de moco, proveniente de las glándulas bronquiales, así como el surfactante derivado de los neomocitos tipo dos.
This section discusses the primary mechanism behind lung expansion, focusing on the formation of secondary septa dividing existing alveoli before birth and the composition of the lungs prenatally.
Mechanism of Lung Expansion
- The main mechanism for lung expansion is through the formation of secondary septa that divide existing alveoli.
- Before birth, the lungs contain high-obligate content with scarce proteins, some mucus from bronchial glands, and surfactant derived from type two pneumocytes.
Cabe mencionar que la cantidad de surfactante en el fluido se incrementa particularmente durante las últimas dos semanas previas al nacimiento. Después del nacimiento el aumento en el tamaño del pulmón se debe a un aumento en el número de los bronquios respiratorios.
This part highlights the increase in surfactant levels in fluid during the final two weeks before birth and explains postnatal lung size growth due to an increase in respiratory bronchioles.
Surfactant Increase and Postnatal Lung Growth
- The amount of surfactant in fluid notably increases during the last two weeks before birth.