![]() ![]() Gland cells and their intertwined vascular beds can be controlled by autonomic innervation and by hormones from other glands.Įach adrenal gland is a two-part organ composed of an outer cortex and an inner medulla. Other secretory mechanisms include holocrine (in which the gland cell membrane disintegrates to release its secretion), apocrine (in which the ends of the gland cells pinch off, carrying the secretion), and direct active transport of particular molecules across the gland cell membrane. The most common secretory mechanism is merocrine, in which secretion-filled intracellular vesicles release their contents by fusing with the cell membrane. Glands can also be classified according to the secretory mechanisms of their cells. The ducted glands are further divided into those in which there is only a single sac (simple tubular glands or simple alveolar glands) and those in which the sacs are connected by branching ducts (branched or compound glands). The cells of ducted glands (exocrine glands) secrete into a cylindrical sac (tubular glands) or into a flask-shaped sac (alveolar glands). ![]() The cells of ductless glands secrete specific molecules into the adjacent interstitial space (paracrine glands) or into the bloodstream (endocrine glands). The multicellular glands are classified according to their architectures, i.e., ducted or ductless. ![]() Glands can be unicellular or multicellular. An epithelial tissue that is specialized for the manufacture and export of particular molecules. ![]()
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