28) The study of tissue is called . 29) Secretions onto body surfaces are characteristic of glands. 30) Unspecialized epithelial cells which act as a source for mitosis are called cells. 31) The combination of fibers and ground substance in supporting connective tissues is known as . 32) are cells that are modified to transmit signals from one place to another. 33) The is the germ layer that differentiates into the GI track, bladder