What is an endocrine gland?
Answers
Answer:
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Explanation:
The endocrine system is a chemical messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In humans, the major endocrine glands are the thyroid gland and the adrenal glands. In vertebrates, the hypothalamus is the neural control center for all endocrine systems. The study of the endocrine system and its disorders is known as endocrinology. Endocrinology is a branch of internal medicine.
A number of glands that signal each other in sequence are usually referred to as an axis, such as the hypothalamic-pituitary-adrenal axis. In addition to the specialized endocrine organs mentioned above, many other organs that are part of other body systems have secondary endocrine functions, including bone, kidneys, liver, heart and gonads. For example, the kidney secretes the endocrine hormone erythropoietin. Hormones can be amino acid complexes, steroids, eicosanoids, leukotrienes, or prostaglandins.
The endocrine system can be contrasted to both exocrine glands, which secrete hormones to the outside of the body, and paracrine signalling between cells over a relatively short distance. Endocrine glands have no ducts, are vascular, and commonly have intracellular vacuoles or granules that store their hormones. In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen.
The word endocrine derives via New Latin from the Greek words ἔνδον, endon, "inside, within," and "crine" from the κρίνω, krīnō, "to separate, distinguish".
Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into interstitial spaces and then absorbed into blood rather than through a duct. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The hypothalamus and pituitary gland are neuroendocrine organs.
Cells Edit
There are many types of cells that comprise the endocrine system and these cells typically make up larger tissues and organs that function within and outside of the endocrine system.
Hypothalamus
Anterior pituitary gland
Pineal gland
Posterior pituitary gland
Thyroid gland
Follicular cells of the thyroid gland produce and secrete T3 and T4 in response to elevated levels of TRH, produced by the hypothalamus, and subsequent elevated levels of TSH, produced by the anterior pituitary gland, which further regulates the metabolic activity and rate of all cells, including cell growth and tissue differentiation.
Parathyroid gland
Epithelial cells of the parathyroid glands are richly supplied with blood from the inferior and superior thyroid arteries and secrete parathyroid hormone (PTH). PTH acts on bone, the kidneys, and the GI tract to increase calcium reabsorption and phosphate excretion. In addition, PTH stimulates the conversion of Vitamin D to its most active variant, 1,25-dihydroxyvitamin D3, which further stimulates calcium absorption in the GI tract.[1]
Adrenal glands
Adrenal cortex
Adrenal medulla
Pancreas
Alpha cells
Beta cells
Delta cells
F Cells
Ovaries
Granulosa cells
Testis
Leydig cells
Endocrine system is made up of eight major glands that each secrete different types of hormones that regulate metabolism, growth and development, sexual reproduction and mood among other things. Its main function is to establish and keep equilibrium within the body.
Major Glands and Théir Functions :-
Hypothalamus
- Integrates the nervous and vertebrate endocrine systems by receiving information from nerves throughout the body and other parts of the brain.
- Once the hypothalamus receives this info, it works to initiate endocrine systems that are appropriate for environmental conditions.
- The Hypothalamus regulates all other endocrine glands via the pituitary gland
Pituitary Gland
- The pituitary gland is made up of the anterior and posterior pituitary glands which are found at the base of the brain and surrounded by bone.
- Although known as the "master gland" it obeys hormonal orders from the hypothalamus
Posterior Pituitary Gland
- An extension of the brain which develops from a small bulge of the hypothalamus and remains an extension of the hypothalamus.
- Stores and dsecretes antidiuretic hormone (ADH) and oxytocin
Anterior Pituitary Gland
- Develops from a fold of tissue at the roof of the developing embryo's mouth and grows upward toward the brain, eventually disconnecting from the mouth.
- Consists of endocrine cells that synthesize and secrete several hormones directly into the blood
- Unlike the posterior, it is not an extension of the brain