The endocrine system

Endocrine System Overview
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Most calcium is stored in the bones. When calcium levels in the blood are low, the parathyroid glands make PTH to get the bones to release calcium into the blood. When calcium levels in the blood are high, the parathyroid glands make less PTH, and calcium levels in the blood lower. The thymus is a gland in the upper part of the chest, just behind the breastbone sternum and between the lungs. The thymus is part of the endocrine system, the lymphatic system and the immune system.

The thymus makes hormones that help T cells a type of white blood cell to mature and function. Find out more about the thymus. We have 2 adrenal glands, one on top of each kidney. The adrenal glands make several hormones that control different body functions, including metabolism, heart rate, blood pressure and water and salt balance.

They also make small amounts of the sex hormones estrogen and testosterone. Find out more about the adrenal glands and adrenal gland hormones. The pancreas is a slim, long organ in the upper left part of the abdomen that sits under the stomach between the liver and spleen. The pancreas is part of the digestive and endocrine systems. The pancreas makes enzymes that are released directly into the small intestine to help digest food. It also makes hormones that help with digestion and control blood sugar glucose levels such as insulin.

The hormones are made in small groups of specialized cells in the pancreas called islets. This part of the pancreas that makes hormones is called the endocrine pancreas. Find out more about the pancreas. Women have 2 ovaries where immature eggs develop into mature eggs ova. The ovaries also make the hormones estrogen and progesterone. Find out more about the ovaries.

About the Endocrine System

A man has 2 testicles. The testicles make sperm and the male sex hormone testosterone. Find out more about the testicles. The neuroendocrine system is made up of special cells called neuroendocrine cells. They are scattered throughout the body. Neuroendocrine cells act like nerve cells neurons and also make hormones like cells of the endocrine system endocrine cells.


Neuroendocrine cells receive messages signals from the nervous system and respond by making and releasing hormones. Neuroendocrine cells are scattered along the gastrointestinal GI tract and are found in the gallbladder, lungs, hypothalamus, pituitary gland, thyroid, parathyroid glands, pancreas and inner layer of the adrenal gland adrenal medulla. Find out more about the neuroendocrine system. The heart and kidneys also play a role in the endocrine system.

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What's this? Human endocrine system. Parathyroids: Attached to the thyroid are four tiny glands that work together called the parathyroids pronounced: par-uh-THY-roydz. Miscellaneous hormones. While the nervous system uses neurons, the endocrine chemicals and hormones must circulate through the body via blood vessels.

They make hormones that help control blood pressure and the amount of blood inside the body called blood volume. The kidneys also make a hormone that makes the body absorb calcium from the food we eat. Some hormones can cause cancer to grow and some cancers make hormones that lead to problems in the body. Estrogen and progesterone are female sex hormones. They can cause breast cancer cells to grow. Some types of breast cancer cells have estrogen receptors ER and progesterone receptors PR on their surface or inside the cell. When hormones attach to these receptors, they can cause the cancer cells to grow and divide.

Hormones can consist of either 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 using ducts 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.

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The endocrine system is the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function. The endocrine system is a system of glands that make hormones. Your body uses hormones to control growth, development, metabolism.

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 human endocrine system consists of several systems that operate via feedback loops.

Endocrine System, Part 1 - Glands & Hormones: Crash Course A&P #23

Several important feedback systems are mediated via the hypothalamus and pituitary. 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.

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.

Endocrine System - On a Molecular Level

A hormone is any of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behaviour. The glands that secrete hormones comprise the endocrine system.

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The term hormone is sometimes extended to include chemicals produced by cells that affect the same cell autocrine or intracrine signalling or nearby cells paracrine signalling. Hormones are used to communicate between organs and tissues for physiological regulation and behavioral activities, such as digestion, metabolism , respiration , tissue function, sensory perception , sleep , excretion , lactation , stress , growth and development , movement , reproduction , and mood.

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Hormones affect distant cells by binding to specific receptor proteins in the target cell resulting in a change in cell function. This may lead to cell type-specific responses that include rapid changes to the activity of existing proteins, or slower changes in the expression of target genes. Amino acid—based hormones amines and peptide or protein hormones are water-soluble and act on the surface of target cells via signal transduction pathways; steroid hormones , being lipid-soluble, move through the plasma membranes of target cells to act within their nuclei.

The typical mode of cell signalling in the endocrine system is endocrine signaling, that is, using the circulatory system to reach distant target organs. However, there are also other modes, i. Purely neurocrine signaling between neurons , on the other hand, belongs completely to the nervous system. Autocrine signaling is a form of signaling in which a cell secretes a hormone or chemical messenger called the autocrine agent that binds to autocrine receptors on the same cell, leading to changes in the cells.

Some endocrinologists and clinicians include the paracrine system as part of the endocrine system, but there is not consensus. Paracrines are slower acting, targeting cells in the same tissue or organ. An example of this is somatostatin which is released by some pancreatic cells and targets other pancreatic cells.

Juxtacrine signaling is a type of intercellular communication that is transmitted via oligosaccharide, lipid, or protein components of a cell membrane, and may affect either the emitting cell or the immediately adjacent cells. It occurs between adjacent cells that possess broad patches of closely opposed plasma membrane linked by transmembrane channels known as connexons. Diseases of the endocrine system are common, [8] including conditions such as diabetes mellitus , thyroid disease, and obesity.

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Endocrine disease is characterized by misregulated hormone release a productive pituitary adenoma , inappropriate response to signaling hypothyroidism , lack of a gland diabetes mellitus type 1 , diminished erythropoiesis in chronic renal failure , or structural enlargement in a critical site such as the thyroid toxic multinodular goitre. Hypofunction of endocrine glands can occur as a result of loss of reserve, hyposecretion, agenesis , atrophy, or active destruction.

Hyperfunction can occur as a result of hypersecretion, loss of suppression, hyperplastic or neoplastic change, or hyperstimulation. Endocrinopathies are classified as primary, secondary, or tertiary.

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Primary endocrine disease inhibits the action of downstream glands. Secondary endocrine disease is indicative of a problem with the pituitary gland. Tertiary endocrine disease is associated with dysfunction of the hypothalamus and its releasing hormones. As the thyroid , and hormones have been implicated in signaling distant tissues to proliferate, for example, the estrogen receptor has been shown to be involved in certain breast cancers.

Endocrine, paracrine, and autocrine signaling have all been implicated in proliferation, one of the required steps of oncogenesis. Other common diseases that result from endocrine dysfunction include Addison's disease , Cushing's disease and Graves' disease. Cushing's disease and Addison's disease are pathologies involving the dysfunction of the adrenal gland. Dysfunction in the adrenal gland could be due to primary or secondary factors and can result in hypercortisolism or hypocortisolism.

Cushing's disease is characterized by the hypersecretion of the adrenocorticotropic hormone ACTH due to a pituitary adenoma that ultimately causes endogenous hypercortisolism by stimulating the adrenal glands. More in this section What is Endocrinology? Find an Endocrinologist Find an endocrinologist today to ensure that you are on the path to health with the right medical care. Physician Directory. Email Address. First Name.