Chemical Messengers 3. Hormones â¢Longârange messengersâ¢Secreted into blood by endocrine glands in response to appropriate signalâ¢Exert effect on target cells some distance away from release site 4.hemical Messengers 3. Hormones â¢Longârange messengersâ¢Secreted into blood by endocrine glands in response to appropriate signalâ¢Exert effect on target cells some distance away from release site 4.
Scale box in millimeters. Vesicular texture is a volcanic rock texture characterized by a rock being pitted with many cavities (known as vesicles) at its surface and inside.
Vision Optic vesicle lies close to the surface ectoderm. The surface ectoderm overlying the optic vesicle, in response to this contact, has thickened to form the lens placode. Diaphragm - pleuroperitoneal fold (PPF) first discernible in human embryos (CRL 6mm).