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Endocrine system - Реферат

Endocrine system

Contents

  • 1 Function

    • 1.1 Types of signaling

      • 1.1.1 Endocrine

      • 1.1.2 Autocrine

      • 1.1.3 Paracrine

      • 1.1.4 Juxtacrine

  • 2 Role in disease

  • 3 Table of endocrine glands and secreted hormones

    • 3.1 Hypothalamus

    • 3.2 Pineal body (epiphysis)

    • 3.3 Pituitary gland (hypophysis)

      • 3.3.1 Anterior pituitary lobe (adenohypophysis)

      • 3.3.2 Posterior pituitary lobe (neurohypophysis)

      • 3.3.3 Intermediate pituitary lobe (pars intermedia)

    • 3.4 Thyroid

    • 3.5 Parathyroid

    • 3.6 Heart

    • 3.7 Striated muscle

    • 3.8 Skin

    • 3.9 Adipose tissue

    • 3.10 Stomach

    • 3.11 Duodenum

    • 3.12 Liver

    • 3.13 Pancreas

    • 3.14 Kidney

    • 3.15 Adrenal glands

      • 3.15.1 Adrenal cortex

      • 3.15.2 Adrenal medulla

      • 3.15.3 Testes

    • 3.16 Ovary

    • 3.17 Placenta (when pregnant)

    • 3.18 Uterus (when pregnant)

  • 4 See also

  • 5 References

  • 6 External links

The endocrine system is a system of small organs that involve the release of extracellular signaling molecules known as hormones. The endocrine system is instrumental in regulating metabolism, growth, development and puberty, and tissue function and also plays a part in determining mood.[1] The field of study that deals with disorders of endocrine glands is endocrinology, a branch of the wider field of internal medicine.

Major endocrine glands. (Male on the left, female on the right.) 1. Pineal gland 2. Pituitary gland 3. Thyroid gland 4. Thymus 5. Adrenal gland 6. Pancreas 7. Ovary 8. Testes

Function

The endocrine system is an information signal system much like the nervous system. However, the nervous system uses nerves to conduct information, whereas the endocrine system mainly uses blood vessels as information channels. Glands located in many regions of the body release into the bloodstream specific chemical messengers called hormones. Hormones regulate the many and varied functions of an organism, e.g., mood, growth and development, tissue function, and metabolism, as well as sending messages and acting on them.

Types of signaling

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.[2] Purely neurocrine signaling between neurons, on the other hand, belongs completely to the nervous system.

Endocrine

A number of glands that signal each other in sequence is usually referred to as an axis, for example, the hypothalamic-pituitary-adrenal axis. Typical endocrine glands are the pituitary, thyroid, and adrenal glands. 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.

Autocrine

Other signaling can target the same cell.

Paracrine

Paracrine signaling is where the target cell is nearby.

Juxtacrine

Juxtacrine signals are transmitted along cell membranes via protein or lipid components integral to the membrane and are capable of affecting either the emitting cell or cells immediately adjacent.

Role in disease

Diseases of the endocrine system are common,[3] including conditions such as diabetes mellitus, thyroid disease, and obesity. Endocrine disease is characterized by dysregulated hormone release (a productive pituitary adenoma), inappropriate response to signaling (hypothyroidism), lack or destruction of a gland (diabetes mellitus type 1, diminished erythropoiesis in chronic renal failure), or structural enlargement in a critical site such as the neck (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. Tertiary endocrine disease is associated with dysfunction of the hypothalamus and its releasing hormones.

Cancer can occur in endocrine glands, such 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.[4]

Table of endocrine glands and secreted hormones

Hypothalamus

Secreted hormone

Abbreviation

From cells

Effect

Thyrotropin-releasing hormone

TRH

Parvocellular neurosecretory neurons

Release thyroid-stimulating hormone from anterior pituitary (primarily)Stimulate prolactin release from anterior pituitary.

Gonadotropin-releasing hormone

GnRH

Neuroendocine cells of the Preoptic area

Release of FSH and LH from anterior pituitary.

Growth hormone-releasing hormone

GHRH

Neuroendocrine neurons of the Arcuate nucleus

Release GH from anterior pituitary

Corticotropin-releasing hormone

CRH

Parvocellular neurosecretory neurons

Release ACTH from anterior pituitary

Oxytocin

Magnocellular neurosecretory cells

Contraction of cervix and vagina

Involved in orgasm, trust between people.[5] and circadian homeostasis (body temperature, activity level, wakefulness).[6] release breast milk

Vasopressin

ADH or AVP

Parvocellular neurosecretory neurons

Increases permeability of distal convoluted tubule and collecting duct to water in the nephrons of the kidney, thus increasing water reabsorbtion.

Somatostatin, also growth hormone-inhibiting hormone

SS or GHIH

Neuroendocrine cells of the Periventricular nucleus

Inhibit release of GH and TSH from anterior pituitary

Prolactin inhibiting hormone or Dopamine

PIH or DA

Dopamine neurons of the arcuate nucleus

Inhibit release of prolactin and TSH from anterior pituitary

Prolactin-releasing hormone

PRH

Release prolactin from anterior pituitary

Pineal body (epiphysis)

Secreted hormone

From cells

Effect

Melatonin (Primarily)

Pinealocytes

antioxidant and causes drowsiness

Pituitary gland (hypophysis)

Anterior pituitary lobe (adenohypophysis)

Secreted hormone

Abbreviation

From cells

Effect

Growth hormone

GH

Somatotropes

stimulates growth and cell reproduction

Release Insulin-like growth factor 1 from liver

Prolactin

PRL

Lactotropes

milk production in mammary glandssexual gratification after sexual acts

Adrenocorticotropic hormone or corticotropin

ACTH

Corticotropes

synthesis of corticosteroids (glucocorticoids and androgens) in adrenocortical cells

Lipotropin

Corticotropes

lipolysis and steroidogenesis,stimulates melanocytes to produce melanin

Thyroid-stimulating hormone or thyrotropin

TSH

Thyrotropes

stimulates thyroid gland to secrete thyroxine (T4) and triiodothyronine (T3)

Follicle-stimulating hormone

FSH

Gonadotropes

In female: stimulates maturation of Graafian follicles in ovary.

In male: spermatogenesis, enhances production of androgen-binding protein by the Sertoli cells of the testes

Luteinizing hormone

LH

Gonadotropes

In female: ovulation

In male: stimulates Leydig cell production of testosterone

Posterior pituitary lobe (neurohypophysis)

f ing Secreted hormone

Abbreviation

From cells

Effect

Oxytocin

Magnocellular neurosecretory cells

Contraction of cervix and vagina

Involved in orgasm, trust between people.[5] and circadian homeostasis (body temperature, activity level, wakefulness).[6] release breast milk

Vasopressin or antidiuretic hormone

AVP or ADH

Magnocellular neurosecretory cells

retention of water in kidneys

moderate vasoconstriction

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