The laryngotracheal groove is a precursor for the

larynx The larynx (), commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...

and

trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from t ...

. The rudiment of the respiratory organs appears as a median longitudinal groove in the ventral wall of the pharynx. The groove deepens and its lips fuse to form a septum which grows from below upward and converts the groove into a tube, the laryngotracheal tube. The cephalic end opens into the pharynx by a slit-like aperture formed by the persistent anterior part of the groove. Initially the cephalic end is in open communication with the foregut but eventually it becomes separated by indentations of

mesoderm The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical Emb ...

, the tracheoesophageal folds. When the tracheoesophageal folds fuse in the midline to form the tracheoesophageal septum, the foregut is divided into trachea ventrally and the esophagus dorsally. The tube is lined by endoderm from which the epithelial lining of the

respiratory tract The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa. Air is breathed in through the nose to ...

is developed. The cephalic part of the tube becomes the larynx, and its next succeeding part the trachea, while from its caudal end a

respiratory diverticulum The lung bud sometimes referred to as the respiratory bud forms from the respiratory diverticulum, an embryological endodermal structure that develops into the respiratory tract organs such as the larynx, trachea, bronchi and lungs. It arises from ...

appears as the

lung bud The lung bud sometimes referred to as the respiratory bud forms from the respiratory diverticulum, an embryological endodermal structure that develops into the respiratory tract organs such as the larynx, trachea, bronchi and lungs. It arises from ...

. The lung bud branches into two lateral outgrowths known as the bronchial buds, one on each side of the trachea. The right and left bronchial buds branch into main (primary), lobar (secondary), segmental (tertiary), and subsegmental

bronchi A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronchus. ...

and lead to the development of the

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of ...

s. The Hox complex, FGF-10 (fibroblast growth factor), BMP-4 (bone morphogenetic protein), N-myc (a proto-oncogene), syndecan (a proteglycan), tenascin (an extracellular matrix protein) and epimorphin (a protein) appear to play a role in development of the respiratory system.

References

External links

* http://www.uoguelph.ca/zoology/devobio/210labs/lung1.html * https://web.archive.org/web/20071013195736/http://embryology.med.unsw.edu.au/Notes/respire.htm {{Authority control Animal developmental biology Embryology Human head and neck