Embryology

2

INI CET 2021 May

Question

Statement 1: Development of tongue is seen around the 4th week of IU life. 
Statement 2: It develops as a single swelling from the 1st brachial arch.

OPTION 3

TONGUE

 

•            The tongue develops in relation to the pharyngeal arches (1st to 4th) in the floor of the developing mouth.

It develops during 4th to 8th weeks. Each pharyngeal arch arises as a mesodermal thickening in the lateral wall of the foregut and that it grows ventrally to become continuous with the corresponding arch of the opposite side.

•            The medial most parts of the mandibular arches proliferate to form two lingual swellings.

The lingual swellings are partially separated from each other by another swelling that appears in the midline. This median swelling is called the tuberculum impar.

 

 

•            Immediately behind the tuberculum impar, the epithelium proliferates to form a downgrowth (thyroglossal duct) from which the thyroid gland develops. The site of this downgrowth is subsequently marked by a depression called the foramen cecum.

•            Another, midline swelling is seen in relation to the medial ends of the second, third and fourth arches.

•            This swelling is called the hypobranchial eminence or copula of His. The eminence soon shows a subdivision into a cranial part related to the second and third arches (called the copula) and a caudal part related to the fourth arch. The caudal part forms the epiglottis.

•            The anterior two thirds of the tongue is formed by fusion of the tuberculum impar and the two lingual swellings.

•            The anterior two thirds of the tongue is thus derived from the mandibular arch. According to some, the tuberculum impar does not make a significant contribution to the tongue. 

Key concept:

•           The tongue develops in relation to the pharyngeal arches (1st to 4th) in the floor of the developing mouth.

•            It develops during 4th to 8th weeks. Each pharyngeal arch arises as a mesodermal thickening in the lateral wall of the foregut and that it grows ventrally to become continuous with the corresponding arch of the opposite side.