The endocrine glands are hormonal glands that release their secretions directly into the bloodstream. Control of the entire endocrine system is the responsibility of the pituitary gland. In organ diseases of the endocrine glands, the hormonal balance gets confused and metabolic problems in particular set in.
What are endocrine glands?
The word endocrine comes from the Greek and means giving off inward. Endocrine glands are therefore glands that secrete directly inward into the blood without an excretory duct. Exocrine glands are to be distinguished from endocrine glands. They secrete their secretions through an excretory duct apocrine, eccrine, holocrine or merocrine into a cavity. Most glands in humans are exocrine glands. Only hormones are secreted directly into the blood without an excretory duct. Therefore, the term endocrine gland is usually synonymous with endocrine gland. For example, the pituitary gland, the adrenal cortex, and the thyroid gland are endocrine glands. The pancreas, on the other hand, has both endocrine and exocrine properties. Together, all endocrine glands form the endocrine system, also known as the endocrine system.
Anatomy and structure
Glands have specialized epithelial cells in the area of the parenchyma, sometimes embedded in capsules of connective tissue. Unlike exocrine glands, endocrine glands consist of so-called islands of cells, surrounded by a reticular structure of closely spaced blood vessels. In exocrine glands, the synthesis of secretions takes place in the gland bodies. In a hemispherical shape, excrine glands are enclosed by secretory ducts that drain secretions into the bloodstream. Often associated with these ducts are other duct systems that direct the secretion to the organs that will process it further. The secretory ducts are absent in endocrine glands. In this case, the blood becomes the transport medium. This transport pathway gives the glands a wide range. However, there are also many paracrine endocrine glands. Their hormones target only the organs in the immediate vicinity. Sometimes their secretions are even autocrine secretions, which are reabsorbed by the producing gland itself.
Function and tasks
Metabolic processes and organ functions in multicellular organisms are regulated by the hormonal system. The hormonal system encompasses all endocrine glands. In the human organism, the pituitary gland, pineal gland, thyroid gland, and parathyroid gland, together with the adrenal glands and the islet gland, form the endocrine system. The glands in the human reproductive organs are also endocrine. The same is true for certain cells of the heart muscle, where peptides are produced. The hypothalamus connects the diencephalon with the endocrine system. This body controls hormone secretion by sending stimulating commands to the pituitary gland in particular. The pituitary gland itself is also a central site of the endocrine system, because hormones from the pituitary stimulate the secretion of yet other hormones from the thyroid, adrenals, and gonads. The hormones of the parathyroid gland mainly regulate the calcium balance in the organism. After stimulation by the pituitary hormone, the pancreas releases insulin into the blood and the adrenal glands secrete stress hormones such as adrenaline and cortisol. In contrast, the sex hormones are produced and secreted in the gonadal islet organ. The endocrine system is thus involved in vital regulatory processes in the organism. Above all, reproduction, metabolism and growth processes are enocrine processes, but also bone formation and blood pressure are partly controlled by hormones of the endocrine glands. In particular, misregulation in the area of stress hormones has life-threatening consequences. Since the endocrine system is a perfectly coordinated network of individual systems, the individual glands influence each other. Thus, if secretion in one of the endocrine glands is faulty, problems usually arise with respect to the other glands as well.
Diseases
The group of endocrine diseases includes various hormonal disorders. These diseases are characterized by either underproduction or overproduction of certain hormones. Usually, in either scenario, the problem is either with the gland itself or with the pituitary gland.If the gland is responsible for the above-average or below-average hormone production, there are usually organ diseases or injuries in the respective organs. Thyroid disorders and adrenal disorders are common causes. If the adrenal glands are misregulating hormone production, symptoms such as truncal obesity, diabetes, or hypertension sometimes present themselves. Depression and fatigue also often occur. Comparable symptoms occur with a disease of the parathyroid glands. Thus, psychiatric clinical pictures in particular are often associated with a disease of the parathyroid glands. Stomach ulcers and kidney stones are also sometimes associated with such a disease. If, on the other hand, the pituitary gland is the cause of misregulated hormone production and secretion, then the general hormone balance can become unbalanced. This can occur, for example, after brain injuries or be caused by a tumor in the area of the pituitary gland. In some hereditary diseases, the pituitary gland is also abnormally formed. Stimulation of other hormone glands by the pituitary gland may thus be impeded. In the same way, a hormone-producing tumor can upset the hormone balance. Such hormone-producing tumors often occur in the pancreas, for example, but the pituitary gland can also be affected by such tumors.