ANATOMY

Detailed explanation-1: -The endoderm constructs the digestive tube and the respiratory tube. 15. Four pairs of pharyngeal pouches become the endodermal lining of the eustacian tube, tonsils, thymus, and parathyroid glands. The thyroid also forms in this region of endoderm.

Detailed explanation-2: -The gastrointestinal (GI) system involves three germinal layers: mesoderm, endoderm, ectoderm. Mesoderm gives rise to the connective tissue, including the wall of the gut tube and the smooth muscle. Endoderm is the source of the epithelial lining of the gastrointestinal tract, liver, gallbladder, pancreas.

Detailed explanation-3: -The respiratory system (the trachea, bronchi, and alveoli of the lungs) is derived from the germ layer endoderm.

Detailed explanation-4: -The endoderm forms organs of the gastrointestinal and respiratory systems, as well as the thymus, parathyroid, bladder, and urethra. The ectoderm is responsible for the development of the skin and skin appendages, the nervous system, and portions of sensory organs.

Detailed explanation-5: -The endoderm is the innermost germ layer that forms the linings of the respiratory and gastrointestinal tracts, and their associated organs, during embryonic development.