Question

The endodermal derivatives include:
A) Thyroid
B) Pineal gland
C) Spleen
D) Pituitary

Answer 1

Hint: In early embryonic development, endoderm is formed as one of the primary germ layers. Several internal organs, the respiratory tract, digestive tract and the urinary tract are the derivatives or segments of the body, developing from the endoderm.

Complete step-by-step answer:
In the early embryonic stages of development, three primary germ layers are formed, namely the ectoderm, which is the outermost layer, the mesoderm layer which is the middle layer and the endoderm, which is the inner layer. These germ layers are formed during the gastrulation process.
The ectoderm forms the origin of central nervous system (comprising of the brain and spinal cord); the epidermis and its appendages (like nails and hair), the sensory epithelia of the eye, ear, and nose; the peripheral nervous system; the enamel of the teeth; the hypophysis; the mammary glands, and the subcutaneous glands.
From the mesoderm arises cartilages, connective tissues and bone; the heart walls, blood and lymph vessels and cells; smooth and striated muscles; the gonads (including the ovaries and testes) and the genital ducts; the serous membranes which line the body cavities; the kidneys; the suprarenal (adrenal) cortices and the spleen.
The endoderm forms the epithelial lining of the parenchymatous cells of the thyroid, the liver, the tonsils, the parathyroids, the pancreas and the thymus; epithelial lining of the respiratory and gastrointestinal tracts.
Development of endoderm is easier as compared to that of ectoderm or mesoderm.
Moreover, spleen arises from the lateral mesodermal plate whereas pineal gland and pituitary develops from the ectoderm. Oral ectoderm gives rise to the anterior pituitary whereas neural ectoderm forms the posterior pituitary.

So, the correct answer is option “A” that is the thyroid is an endodermal derivative.

Note: In the early stages of embryonic development, a group of cells forming germ layers interacts with each other thereby contributing in the formation of various organs and tissues.