Many of the endocrine glands have a similar basic structure, composed of clusters of secretory cells of epithelial origin. Hormones are secreted into the interstitial space wherby they are rapidly absorbed into the circulatory system. In contrast the exocrine system has a duct system and so can secrete its contents directly into its target area. | Many of the endocrine glands have a similar basic structure, composed of clusters of secretory cells of epithelial origin. Hormones are secreted into the interstitial space wherby they are rapidly absorbed into the circulatory system. In contrast the exocrine system has a duct system and so can secrete its contents directly into its target area. |