The respiratory system develops from the foregut of an embryo. Around 4 weeks, lung buds form as outgrowths from the foregut and expand into the spaces that will become the lungs. The trachea and bronchi also develop from these outgrowths. Mesoderm surrounding the foregut develops into tissues surrounding the lungs and trachea. Over subsequent weeks, the lung buds branch repeatedly to form the bronchopulmonary segments. Around 5 months, the structures develop into gas exchange sacs called alveoli. Surfactant production begins around 6 months to prevent alveolar collapse. Further alveolar development continues for 10 years after birth.
The respiratory system develops from the foregut of an embryo. Around 4 weeks, lung buds form as outgrowths from the foregut and expand into the spaces that will become the lungs. The trachea and bronchi also develop from these outgrowths. Mesoderm surrounding the foregut develops into tissues surrounding the lungs and trachea. Over subsequent weeks, the lung buds branch repeatedly to form the bronchopulmonary segments. Around 5 months, the structures develop into gas exchange sacs called alveoli. Surfactant production begins around 6 months to prevent alveolar collapse. Further alveolar development continues for 10 years after birth.
Original Description:
Embryology, all about embryology is stored here and you can get it for free
The respiratory system develops from the foregut of an embryo. Around 4 weeks, lung buds form as outgrowths from the foregut and expand into the spaces that will become the lungs. The trachea and bronchi also develop from these outgrowths. Mesoderm surrounding the foregut develops into tissues surrounding the lungs and trachea. Over subsequent weeks, the lung buds branch repeatedly to form the bronchopulmonary segments. Around 5 months, the structures develop into gas exchange sacs called alveoli. Surfactant production begins around 6 months to prevent alveolar collapse. Further alveolar development continues for 10 years after birth.
The respiratory system develops from the foregut of an embryo. Around 4 weeks, lung buds form as outgrowths from the foregut and expand into the spaces that will become the lungs. The trachea and bronchi also develop from these outgrowths. Mesoderm surrounding the foregut develops into tissues surrounding the lungs and trachea. Over subsequent weeks, the lung buds branch repeatedly to form the bronchopulmonary segments. Around 5 months, the structures develop into gas exchange sacs called alveoli. Surfactant production begins around 6 months to prevent alveolar collapse. Further alveolar development continues for 10 years after birth.
Download as DOCX, PDF, TXT or read online from Scribd
Download as docx, pdf, or txt
You are on page 1of 1
Riezky Febriyanti 130110110064- A4
EMBRYOLOGY RESPIRATORY SYSTEM
Formation of lung buds When the embryo is approximately 4 weeks old, the respiratory diverticulum (lung bud) appears as an outgrowth from the ventral wall of the foregut. Initially the lung bud is in open communication with the foregut. When the diverticulum expands caudally, the tracheoesophageal septum formed, the foregut is divided into a dorsal portion, the esophagus, and a ventral portion, the trachea and lung buds. Hence epithelium of the internal lining of the larynx, trachea, and bronchi, as well as that of the lungs, is entirely of endodermal origin. The cartilaginous, muscular, and connective tissue components of the trachea and lungs are derived from splanchnic mesoderm surrounding the foregut Trachea, Bronchi, and Lung During its separation from the foregut, the lung bud forms the trachea and two lateral outpocketings, the bronchial buds. At the beginning of the fifth week, each of these buds enlarges to form right and left main bronchi. The right then forms three secondary bronchi, and the left, two. With subsequent growth in caudal and lateral directions, the lung buds expand into the spaces for the lungs, the pericardioperitoneal canals, that is lie on each side of the foregut. The remaining spaces form the primitive pleural cavities The mesoderm, which covers the outside of the lung, develops into the visceral pleura. The somatic mesoderm layer, covering the body wall from the inside, becomes the parietal pleura. The space between the parietal and visceral pleura is the pleural cavity. During further development, secondary bronchi divide, forming 10 tertiary (segmental) bronchi in the right lung and 8 in the left, creating the bronchopulmonary segments of the adult lung. By the end of the sixth month, approximately 17 generations of subdivisions have formed, additional 6 divisions form during postnatal life.
Maturation of Lung After a pseudoglandular (516 weeks) and canalicular (1626 weeks) phase, cells of the cuboidal lined bronchioles change into thin, flat cells, type I alveolar epithelial cells, intimately associated with blood and lymph capillaries known as terminal sacs or primitive alveoli. In the seventh month, gas exchange between the blood and air in the primitive alveoli is possible. In addition another cell type develops at the end of the sixth month. These cells, type II alveolar epithelial cells, produce little protein, some mucus and surfactant (forms a phospholipid coat on the alveolar membranes). Fetal breathing movements begin before birth and cause aspiration of amniotic fluid. These movements are important for stimulating lung development and conditioning respiratory muscles. When respiration begins at birth, most of the lung fluid is rapidly resorbed (by the blood and lymph capillaries, and a small amount is probably expelled via the trachea and bronchi during delivery) except for the surfactant coat, which prevents the collapse of the alveoli during expiration by reducing the surface tension at the air-blood capillary interface. Absent or insufficient surfactant in the premature baby causes respiratory distress syndrome (RDS) because of collapse of the primitive alveoli (hyaline membrane disease). The remaining alveoli are formed during the first 10 years of p ostnatal life through the continuous formation of new primitive alveoli.