Look up template in Wiktionary, the free dictionary.

Template may mean:

• a stencil, pattern or overlay used in graphic arts (drawing, painting, etc.) and sewing to replicate letters, shapes or designs
• a pre-developed page layout in electronic or paper media used to make new pages with a similar design, pattern, or style
• Form letter, a predefined letter which retains its primary intent when individually customised with variable data or text.

Computer science and information technology[link]

• Template (file format), a standardized non-executable file type used by computer software as a pre-formatted example on which to base other files, especially documents
• Template (C++), a tool for generic programming especially in the C++ language
• Template metaprogramming, a programming technique used by a compiler to generate temporary source code
• Template method, an object-oriented design pattern
• Template processor, a system that combines a template with data to produce an output.
• Template (word processing), a standard document containing layout and styles used to configure word processing software
• Style sheet (web development) or master page on which you can globally edit and format graphic elements and text common to each page of a document
• Web template or web template system, a master page used to produce web pages
• A main document from which mail merge documents are created

Manufacturing[link]

• Mechanical template, used to cut and shape a product, such as:
  • a die (manufacturing)
  • a mold

Molecular genetics[link]

• a strand of DNA which sets the genetic sequence of new strands
• a strand of RNA which translates genes into proteins

Miscellaneous[link]

• Template (racing), a device used in car racing to ensure that the body of the race vehicle adheres to specifications

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Endocrine glands
The major endocrine glands: 1 Pineal gland 2 Pituitary gland 3 Thyroid gland 4 Thymus 5 Adrenal gland 6 Pancreas 7 Ovary (female) 8 Testes (male)
Latin	glandulae endocrinae
Code	TH H2.00.02.0.03072

Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. The main endocrine glands include the pituitary gland, pancreas, ovaries, testes, thyroid gland, and adrenal glands. The hypothalamus is a neuroendocrine organ. Other organs which are not so well known for their endocrine activity include the stomach, which produces such hormones as ghrelin.

Local chemical messengers, not generally considered part of the endocrine system, include autocrines, which act on the cells that secrete them, and paracrines, which act on a different cell type nearby.

The ability of a target cell to respond to a hormone depends on the presence of receptors, within the cell or on its plasma membrane, to which the hormone can bind.

Hormone receptors are dynamic structures. Changes in number and sensitivity of hormone receptors may occur in response to high or low levels of stimulating hormones.

Blood levels of hormones reflect a balance between secretion and degradation/excretion. The liver and kidneys are the major organs that degrade hormones; breakdown products are excreted in urine and feces.

Hormone half-life and duration of activity are limited and vary from hormone to hormone.

Interaction of hormones at target cells[link]

Permissiveness is the situation in which a hormone cannot exert its full effects without the presence of another hormone.

Synergism occurs when two or more hormones produce the same effects in a target cell and their results are amplified.

Antagonism occurs when a hormone opposes or reverses the effect of another hormone.

Control of hormone release[link]

Endocrine organs are activated to release their hormones by humoral, neural, or hormonal stimuli. Negative feedback is important in regulating hormone levels in the blood.

The nervous system, acting through hypothalamic controls, can in certain cases override or modulate hormonal effects.

Major endocrine organs[link]

Pituitary gland (hypophysis)[link]

Endocrine glands in the human head and neck and their hormones

The pituitary gland hangs from the base of the brain by a stalk and is enclosed by bone. It consists of a hormone-producing glandular portion (anterior pituitary) and a neural portion (posterior pituitary), which is an extension of the hypothalamus. The hypothalamus regulates the hormonal output of the anterior pituitary and synthesizes two hormones that it exports to the posterior pituitary for storage and later release.

Four of the six adenohypophyseal hormones are tropic hormones that regulate the function of other endocrine organs. Most anterior pituitary hormones exhibit a diurnal rhythm of release, which is subject to modification by stimuli influencing the hypothalamus.

Somatotropic hormone or Growth hormone (GH) is an anabolic hormone that stimulates growth of all body tissues but especially skeletal muscle and bone. It may act directly, or indirectly via insulin-like growth factors (IGFs). GH mobilizes fats, stimulates protein synthesis, and inhibits glucose uptake and metabolism. Secretion is regulated by growth hormone releasing hormone (GHRH) and growth hormone inhibiting hormone (GHIH), or somatostatin. Hypersecretion causes gigantism in children and acromegaly in adults; hyposecretion in children causes pituitary dwarfism.

Thyroid-stimulating hormone (TSH) promotes normal development and activity of the thyroid gland. Thyrotropin-releasing hormone (TRH) stimulates its release; negative feedback of thyroid hormone inhibits it.

Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to release corticosteroids. ACTH release is triggered by corticotropin-releasing hormone (CRH) and inhibited by rising glucocorticoid levels.

The gonadotropins—follicle-stimulating hormone (FSH) and luteinizing hormone (LH) regulate the functions of the gonads in both sexes. FSH stimulates sex cell production; LH stimulates gonadal hormone production. Gonadotropin levels rise in response to gonadotropin-releasing hormone (GnRH). Negative feedback of gonadal hormones inhibits gonadotropin release.

Prolactin (PRL) promotes milk production in humans females. Its secretion is prompted by prolactin-releasing hormone (PRH) and inhibited by prolactin-inhibiting hormone (PIH).

The neurohypophysis stores and releases two hypothalamic hormones:

• Oxytocin stimulates powerful uterine contractions, which trigger labor and delivery of an infant, and milk ejection in nursing women. Its release is mediated reflexively by the hypothalamus and represents a positive feedback mechanism.
• Antidiuretic hormone (ADH) stimulates the kidney tubules to reabsorb and conserve water, resulting in small volumes of highly concentrated urine and decreased plasma osmolality. ADH is released in response to high solute concentrations in the blood and inhibited by low solute concentrations in the blood. Hyposecretion results in diabetes insipidus.

Thyroid gland[link]

The thyroid gland is located in the anterior throat. Thyroid follicles store colloid containing thyroglobulin, a glycoprotein from which thyroid hormone is derived.

Thyroid hormone (TH) includes thyroxine (T4) and triiodothyronine (T3), which increase the rate of cellular metabolism. Consequently, oxygen use and heat production rise.

Secretion of thyroid hormone, prompted by TSH, requires reuptake of the stored colloid by the follicle cells and splitting of the hormones from the colloid for release. Rising levels of thyroid hormone feed back to inhibit the pituitary and hypothalamus.

Most T4 is converted to T3 (the more active form) in the target tissues. These hormones act by turning on gene and protein synthesis.

Graves' disease is the most common cause of hyperthyroidism; hyposecretion causes cretinism in infants and myxoedema in adults.

Calcitonin, produced by the parafollicular cells of the thyroid gland in response to rising blood calcium levels, depresses blood calcium levels by inhibiting bone matrix resorption and enhancing calcium deposit in bone.

Parathyroid glands[link]

The parathyroid glands, located on the dorsal aspect of the thyroid gland, secrete parathyroid hormone (PTH),^[1] which causes an increase in blood calcium levels by targeting bone, the intestine, and the kidneys. PTH is the antagonist of calcitonin. PTH release is triggered by falling blood calcium levels and is inhibited by rising blood calcium levels.

Hyperparathyroidism results in hypercalcaemia and all its effects and in extreme bone wasting. Hypoparathyroidism leads to hypocalcaemia, evidenced by tetany and respiratory paralysis.

Pancreas[link]

The pancreas, located in the abdomen close to the stomach, is both an exocrine and an endocrine gland. The endocrine portion (islets of langerhans) releases insulin and glucagon and smaller amounts of other hormones to the blood.

Glucagon, released by alpha (α) cells when glucose level in blood are low, stimulates the liver to release glucose to the blood.

Insulin is released by beta (β) cells when blood levels of glucose (and amino acids) are rising. It increases the rate of glucose uptake and metabolism by most body cells. Hyposecretion of insulin results in diabetes mellitus; cardinal signs are polyuria, polydipsia, and polyphagia.

Gonads[link]

The ovaries of the female, located in the pelvic cavity, release two main hormones. Secretion of estrogens by the ovarian follicles begins at puberty under the influence of FSH. Estrogens stimulate maturation of the female reproductive system and development of the secondary sex characteristics. Progesterone is released in response to high blood levels of LH. It works with estrogens in establishing the menstrual cycle.

The testes of the male begin to produce testosterone at puberty in response to LH. Testosterone promotes maturation of the male reproductive organs, development of secondary sex characteristics, and production of sperm by the testes.

Pineal gland[link]

The pineal gland is located in the diencephalon. Its primary hormone is melatonin, which influences daily rhythms and may have an antigonadotropic effect in humans.

Other hormone-producing structures[link]

Many body organs not normally considered endocrine organs contain isolated cell clusters that secrete hormones. Examples include the heart (atrial natriuretic peptide); gastrointestinal tract organs (gastrin, secretin, and others); the placenta (hormones of pregnancy—estrogen, progesterone, and others); the kidneys (erythropoietin and renin); the thymus; skin (cholecalciferol); and adipose tissue (leptin and resistin). B

Developmental aspects of the endocrine system[link]

Endocrine glands derive from all three germ layers. Those derived from mesoderm produce steroidal hormones; the others produce the amino acid–based hormones.

The natural decrease in function of the female’s ovaries during late middle age results in menopause. The efficiency of all endocrine glands seems to decrease gradually as aging occurs. This leads to a generalized increase in the incidence of diabetes mellitus and a lower metabolic rate.

References[link]

The endocrine system is the system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body. The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts. It derives from the Greek words "endo" meaning inside, within, and "crinis" for secrete. The endocrine system is an information signal system like the nervous system, yet its effects and mechanism are classifiably different. The endocrine system's effects are slow to initiate, and prolonged in their response, lasting from a few hours up to weeks. The nervous system sends information very quickly, and responses are generally short lived. Hormones are substances (chemical mediators) released from endocrine tissue into the bloodstream where they travel to target tissue and generate a response. Hormones regulate various human functions, including metabolism, growth and development, tissue function, and mood. The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine.

Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing 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.

In addition to the specialised endocrine organs mentioned above, many other organs that are part of other body systems, such as the kidney, liver, heart and gonads, have secondary endocrine functions. For example the kidney secretes endocrine hormones such as erythropoietin and renin.

The endocrine system is made of a series of glands that produce chemicals called hormones. A number of glands that signal each other in sequence are usually referred to as an axis, for example, the hypothalamic-pituitary-adrenal axis.

Endocrine organs and secreted hormones[link]

Endocrine glands in the human head and neck and their hormones

[edit] Hypothalamus

[edit] Pineal body (epiphysis)

[edit] Pituitary gland (hypophysis)

[edit] Anterior pituitary lobe (adenohypophysis)

[edit] Posterior pituitary lobe (neurohypophysis)

Oxytocin and anti-diuretic hormone are not secreted in the posterior lobe, merely stored.

[edit] Thyroid

Alimentary system[link]

[edit] Stomach

[edit] Duodenum

[edit] Liver

[edit] Pancreas

[edit] Kidney

[edit] Adrenal glands

[edit] Adrenal cortex

[edit] Adrenal medulla

Reproductive[link]

[edit] Testes

[edit] Ovarian follicle and corpus luteum

[edit] Placenta (when pregnant)

[edit] Uterus (when pregnant)

Calcium regulation[link]

[edit] Parathyroid

[edit] Skin

Miscellaneous[link]

[edit] Heart

[edit] Bone marrow

[edit] Adipose tissue

Major endocrine systems[link]

The human endocrine system consists of several systems that operate via feedback loops. Several important feedback systems are mediated via the hypothalamus and pituitary.^[12]

• TRH - TSH - T3/T4
• GnRH - LH/FSH - sex hormones
• CRH - ACTH - cortisol
• Renin - angiotensin - aldosterone

Diseases[link]

Disability-adjusted life year for endocrine disorders per 100,000 inhabitants in 2002.^[13]

  no data

  less than 80

  80-160

  160-240

  240-320

  320-400

  400-480

  480-560

  560-640

  640-720

  720-800

  800-1000

  more than 1000

Diseases of the endocrine system are common,^[14] including conditions such as diabetes mellitus, thyroid disease, and obesity. Endocrine disease is characterized by disregulated 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. 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.^{[citation needed]}

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.^[15]

Other types of signaling[link]

The typical mode of cell signaling in the endocrine system is endocrine signaling. However, there are also other modes, i.e., paracrine, autocrine, and neuroendocrine signaling.^[16] Purely neurocrine signaling between neurons, on the other hand, belongs completely to the nervous system.

Autocrine[link]

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.

Paracrine[link]

Paracrine signaling is a form of cell signaling in which the target cell is near the signal-releasing cell.

Juxtacrine[link]

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. The gap between the cells can usually be between only 2 and 4 nm.

Unlike other types of cell signaling (such as paracrine and endocrine), juxtacrine signaling requires physical contact between the two cells involved.

Juxtacrine signaling has been observed for some growth factors, cytokine and chemokine cellular signals.

See also[link]

• Releasing hormones
• Neuroendocrinology
• Nervous system
• Endocrine disruptor
• Human anatomy#Major organ systems
• Endocrine disease
• Endocrinology

References[link]

This article relies largely or entirely upon a single source. Please help improve this article by introducing citations to additional sources. Discussion about the problems with the sole source used may be found on the talk page. (February 2012)

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Gland
Human submaxillary gland. At the right is a group of mucous alveoli, at the left a group of serous alveoli.
Latin	glandula
Code	TH H2.00.02.0.02002

A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).

Types[link]

Glands can be divided into 2 groups:

• Endocrine glands — are glands that secrete their products through the basal lamina and lack a duct system.
• Exocrine glands — secrete their products through a duct or directly onto the apical surface, the glands in this group can be divided into three groups:
  • Apocrine glands — a portion of the secreting cell's body is lost during secretion. Apocrine gland is often used to refer to the apocrine sweat glands, however it is thought that apocrine sweat glands may not be true apocrine glands as they may not use the apocrine method of secretion.
  • Holocrine glands — the entire cell disintegrates to secrete its substances (e.g., sebaceous glands)
  • Merocrine glands — cells secrete their substances by exocytosis (e.g., mucous and serous glands). Also called "eccrine".

The type of secretory product of an Exocrine gland may also be one of three categories:

• Serous glands — secrete a watery, often protein-rich product.
• Mucous glands — secrete a viscous product, rich in carbohydrates (e.g., glycoproteins).
• Sebaceous glands — secrete a lipid product.These glands are also known as oil glands.

Formation[link]

Every gland is formed by an ingrowth from an epithelial surface. This ingrowth may from the beginning possess a tubular structure, but in other instances glands may start as a solid column of cells which subsequently becomes tubulated.

As growth proceeds, the column of cells may divide or give off offshoots, in which case a compound gland is formed. In many glands the number of branches is limited, in others (salivary, pancreas) a very large structure is finally formed by repeated growth and sub-division. As a rule, the branches do not unite with one another, but in one instance, the liver, this does occur when a reticulated compound gland is produced. In compound glands the more typical or secretory epithelium is found forming the terminal portion of each branch, and the uniting portions form ducts and are lined with a less modified type of epithelial cell.

Glands are classified according to their shape.

• If the gland retains its shape as a tube throughout it is termed a tubular gland.
• In the second main variety of gland the secretory portion is enlarged and the lumen variously increased in size. These are termed alveolar or saccular glands.

Specific glands[link]

• List of human endocrine glands.
• List of human exocrine glands.

Additional images[link]

• 

  Section of submaxillary gland of kitten. Duct semidiagrammatic.

• 

  Section of pancreas of dog. X 250.

• 

  Dissection of a lactating breast.

• 

  Section of portion of mamma.

• 

  Apocrine

• 

  Methods of secretion

References[link]

Look up gland in Wiktionary, the free dictionary.

•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.