What is the X in X-mas?
endoderm en·do·derm (ěn'də-dûrm') or en·to·derm (ěn'tə-)
The innermost of the three primary germ layers of an embryo, developing into the gastrointestinal tract, the lungs, and associated structures. Also called hypoblast.
The innermost of the primary germ layers of an animal embryo. In vertebrates, the endoderm gives rise to the respiratory tract, gastrointestinal tract (except mouth and anus), glands associated with the gastrointestinal tract, bladder, and urethra. Compare ectoderm, mesoderm.
the innermost of the three germ layers, or masses of cells (lying within ectoderm and mesoderm), which appears early in the development of an animal embryo. The endoderm subsequently gives rise to the epithelium (tissue that covers, or lines, a structure) of the pharynx, including the eustachian tube, the tonsils, the thyroid gland, parathyroid glands, and thymus gland; the larynx, trachea, and lungs; the gastrointestinal tract (except mouth and anus), the urinary bladder, the vagina (in females), and the urethra. The term endoderm is sometimes used to refer to the gastrodermis, the simple tissue that lines the digestive cavity of cnidarians and ctenophores. Compare ectoderm; mesoderm.