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THE ENDOCRINE SYSTEM

Endocrine system consist of various glands that release hormones also known as secondary messengers directly into the blood and reach the target organs to perform specific function

Glands are the organs of the body that releases some substances such as sweat, sebum, cerumen enzymes or hormones. Glands are classified broadly as exocrine and endocrine glands. Exocrine glands are duct glands that pour their secretion to target organs through ducts. Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into interstitial spaces where they are absorbed into the bloodstream. These are ductless glands. The major glands of the endocrine system are mentioned below along with their location

  • pineal gland (middle of the brain)

  • pituitary gland forebrain)

  • pancreas (back of the abdomen, behind the stomach) 

  • ovaries (pelvic region – only in females)

  • testes (outside abdomen in the scrotum – only in males) 

  • thyroid gland (front of the neck, below the voice box)

  • parathyroid gland (front of the neck, below the voice box)

  • hypothalamus (base of the forebrain)

  • adrenal glands (top of each kidney)

The hypothalamus and pituitary gland are neuroendocrine organs.

Hormones flowing in the blood diffuse into the interstitial liquids encompassing the cell. Cells with explicit receptors for a chemical reaction with an activity that is proper for the cell. Due to the particularity of chemical and target cells, the impacts delivered by a solitary chemical might fluctuate among various types of target cells.

Chemicals enact target cells by one of two strategies, contingent on the compound idea of the chemical.

Lipid-dissolvable chemicals (steroid chemicals and chemicals of the thyroid organ) diffuse through the cell layers of target cells. The lipid-dissolvable chemical then, at that point, ties to a receptor protein that, thus, initiates a DNA section that turns on explicit qualities. The proteins created as an aftereffect of the record of the qualities and ensuing interpretation of mRNA go about as compounds that direct explicit physiological cell action.

Water-dissolvable chemicals (polypeptide, protein, and most amino corrosive chemicals) tie to a receptor protein on the plasma layer of the cell. The receptor protein, thus, invigorates the creation Cyclic AMP (cAMP) or Inositol triphosphate.

Properties of hormones

  • These are emitted by the endocrine organ.

  • Their emissions is delivered straightforwardly into blood for certain exemptions like gastrin

  • These are conveyed to explicit organs, called target organs, which are indirectly found.

  • These have explicit physiological activity (excitatory or inhibitory).

  • These are required in extremely low fixation.

  • Chemicals are non-antigenic, which implies that they can’t invigorate the development of antibodies.

  • These are generally fleeting particles,

  • A few chemicals are emitted in an idle structure called prohormone, e.g., supportive of insulin.

  • Chemicals after their activity are obliterated in the liver and kidney.

Nature of hormones

  • amine hormones 

  • steroids hormones 

  • proteinaceous hormones

  • peptide hormones

Gland 

hormone

function

Disorder

Hypothalamus (super master gland)

   

Pituitary (master gland)

growth hormone (GH), thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), luteinizing hormone (LH), interstitial cell-stimulating hormone (ICSH), prolactin (PRL) and adrenocorticotropic hormone (ACTH)

Growth hormone is responsible for growth of bones and muscles

Hypersecretion of   Growth hormone leads to abnormal excessive growth of the body leading to gigantism and acromegaly hyposecretion of Growth hormone leads to stunted growth resulting in pituitary dwarfism and Simmonds disease

Pineal

Melatonin

It helps in maintaining the various cyclic changes in the body such as sleep-wake cycle and body temperature. pigmentation, the menstrual cycle

 

Thyroid (largest endocrine gland)

tetraiodothyronine or thyroxine (T4) triiodothyronine (T3)


 thyrocalcitonin (TCT)

Maintaining BMR ( basal metabolic rate ), these are also necessary for normal growth. It promotes the effects of growth hormones on protein synthesis. And various metabolic activities are controlled by thyroxine.




calcium metabolism

A lack of iodine in the eating routine prompts the growth of the thyroid organ, known as simple goiter. Hypothyroidism during early advancement prompts cretinism. In grown-ups, it produces myxedema, portrayed by weight and dormancy. Hyperthyroidism prompts a condition known as exophthalmic goiter, portrayed by weight reduction as well as hyperactive and touchy conduct.

Parathyroid

Parathyroid hormone 

calcium metabolism, works antagonistically to TCT

 

Thymus

Thymosin 

Provides immunity 

 

Adrenal

Zona glomerulosa secretes mineralocorticoids primarily aldosterone.

Zona fasciculata secretes glucocorticoids, mainly cortisol.

Zona reticularis secretes sex corticoids including testosterone.

adrenal medulla secretes two hormones – adrenaline (or epinephrine) and noradrenaline (or norepinephrine). These are commonly called as catecholamines as well as 

emergency hormones

Aldosterone is salt retaining hormone


Glucocorticoids stimulate the breakdown of glycogen,lipids and proteins.









Increase alertness, pupillary dilation, piloerection (raising of hairs), sweating etc. Both the hormones increase the heart beat also.

 

Pancreas ( heterocrine gland )

Insulin











Glucagon




Maintains glucose level in body by decreasing the glucose in blood Insulin acts mainly on hepatocytes and adipocytes and enhances cellular glucose uptake and utilization



maintains the normal blood glucose levels. It acts mainly on the hepatocytes and resulting in an increased blood sugar to normal

hyposecretion of insulin leads to diabetes mellitus.

Testis (only in males)

androgens (mainly testosterone).

Responsible for secondary sexual characters in males.

 

Ovary (only in females)

Estrogen 




Progesterone (maintains pregnancy) 

Responsible for secondary sexual characters in females

 

Conclusion

Endocrine glands belong to the body’s system. The hormones that they turn out facilitate control of the functions of cells and tissues throughout the body. Endocrine organs are a unit activated to unharness their hormones by body substance, neural, or secretion stimuli. The feedback mechanism plays a vital role in regulation of secretion of hormones within the blood.