NEET BIOLOGY

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 embryonic endoderm develops into the interior linings of two tubes in the body, the digestive and respiratory tube. the lining of the follicles of the thyroid gland and the epithelial component of the thymus (i.e. thymic epithelial cells). Liver and pancreas cells are believed to derive from a common precursor.

Detailed explanation-3: -The endoderm is an embryonic germ layer that gives rise to tissues that form internal structures and organs. The endoderm is found in both vertebrate and invertebrate embryos, and is responsible for the formation of the gut and associated organs.

Detailed explanation-4: -The ectoderm gives rise to the skin, the brain, the spinal cord, subcortex, cortex and peripheral nerves, pineal gland, pituitary gland, kidney marrow, hair, nails, sweat glands, cornea, teeth, the mucous membrane of the nose, and the lenses of the eye (see Fig. 5.3).