Endocrine System
The endocrine system consists of specialized glands located in different parts of the body. These glands secrete chemical substances called Hormones, which transfer information from one set of cells to another. This enables the organism to adjust various activities of the body to the changing demands of the external and internal environment. The endocrine glands have no ducts connecting them to their target organs or tissues (they are hence often called the ductiles glands), and so they liberate hormones directly into the bloodstream . Mammalian endocrine glands include the hypothalamus, pituitary, thyroid , parathyroid, thymus , pancreas , adrenal, testis, and ovary. Invertebrates posses few glands, and many of these are simply clusters of nerve cells. Arthropods have neurosecretory structures in the eyestalks, brain and ganglia that regulate reproduction, moiting, development, pigmentation, water balance, blood sugar level, and heart rate. The conventional ductless glands of arthr...