How are tissues and organs different?

Three germ layers and tissues or organs that deriving from each?

• Answer:

  1. The ectoderm is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers. The ectoderm forms: the central nervous system, the lens of the eye, cranial and sensory, the ganglia and nerves, pigment cells, head connective tissues, the epidermis, hair, and mammary glands. 2. The endoderm consists at first of flattened cells, which subsequently become columnar. It forms the epithelial lining of the whole of the digestive tube except part of the mouth and pharynx and the terminal part of the rectum (which are lined by involutions of the ectoderm). It also forms the lining cells of all the glands which open into the digestive tube, including those of the liver and pancreas; the epithelium of the auditory tube and tympanic cavity; the trachea, bronchi, and air cells of the lungs; the urinary bladder and part of the urethra; and the follicle lining of the thyroid gland and thymus. The endoderm forms: the stomach, the colon, the liver, the pancreas, the urinary bladder, the lining of the urethra, the epithelial parts of trachea, the lungs, the pharynx, the thyroid, the parathyroid, and the intestines. 3. The mesoderm germ layer forms in the embryos of triploblastic animals. During gastrulation, some of the cells migrating inward contribute to the mesoderm, an additional layer between the endoderm and the ectoderm. The formation of a mesoderm led to the development of a coelom. Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks. The mesoderm forms: skeletal muscle, the skeleton, the dermis of skin, connective tissue, the urogenital system, the heart, blood (lymph cells), the kidney, and the spleen.