Medicine and Health related Information

The respiratory system develops from the median diverticulum of the foregut. Its lining epithelium is therefore of endodermal in origin. The connective tissue cartilage and muscle, in relation to the organs of respiration are derived from splanchno-pleuric mesoderm.
The respiratory diverticulum deepens to form tracheobronchial groove. Initially it communicates with the foregut, but later it is seperated from it by oesophageal tracheal septum. But in adults the larynx still communicates with the pharynx.
LARYNX- The larynx develops from the cranial most end of the respiratory diverticulum. The communication between the diverticulum and the pharynx persists as the inlet of larynx, the caudal part of the hypobronchial eminence forms the epiglottis. The thyroid, cricoid, arytenoid cartilages are derivatives of the fourth, fifth and sixth pharyngeal arches. The laryngeal muscles are also derived from bronchial mesoderm as it is indicated by their nerve supply.
TRACHEA AND BRAONCHII- The trachea develops from the part of the respiratory diverticulum, that lies between the points of its bifurcation and the larynx.
The two primary divisions of the respiratory diverticulum form the right and left principal bronchii. The left division comes to lie more transversely than the right. It shows two subdivisions that represent the two lobar bronchii of the left lungs. The right division divides into three labor bronchii.
LUNGS- The tracheo-braonchial tube divides into two lung buds which invaginates the developing pleural sac (or) peritoneal canal.
The right lung bud divides into 3 branches which forms 3 bronchi and 3 lobes of lung.
The left lung bud divides into 2 branches which divides into 2 bronchi and 2 lobes of lung.
The alveoli and its lining epithelium are developed from endoderm. The pleural cavity is the cavity of intra-embryonic coelom.