Endocrine Glands: Introduction, Endocrine Glands, Major Endocrine Glands

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Introduction to Endocrine System

  • Endocrine System can be defined as a chemical messenger system comprising feedback loops of the hormones released by internal glands of an organism.

  • This includes regulating distant target organs and the circulatory system.

  • This system can be contrasted to both exocrine glands which secrete hormones to the outside of the body which further includes paracrine signaling between cells over a short distance.

  • Through nine primary glands hormones are produced in the body along with other organs that provide auxiliary functions make up the endocrine system.

Major Endocrine Glands

Major Endocrine Glands

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Endocrine Glands

  • The endocrine glands belong to the body’s control system and they secrete their respective substances directly into the bloodstream rather than through a duct.

  • The hormones help in regulating the functions of cells and tissues. Some of the glands are specific to either male (testis) or female (ovaries).

Major Endocrine Glands

Major Endocrine Glands

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Pituitary Gland

  • It is a small pea-sized gland that plays a vital role in regulating vital body functions and general wellbeing.

  • It is also known as the master gland as it controls the activity of most other hormone secreting glands.

  • This gland hangs on a stalk at the base of the brain.

  • The anterior portion produces hormones and a posterior portion that has many neural links.

  • This gland also secretes prolactin, which stimulates the production of milk.

Thyroid Gland

  • It is an endocrine gland in the neck that consists of two connected lobes.

  • Thyroid isthmus is a thin band of tissue connecting the lower two thirds of the lobes.

  • The thyroid is located at the front of the neck below Adam’s apple.

  • The most important hormones produced are T3 and T4 among other thyroid hormones which influences the body’s rate of metabolism.

Parathyroid Glands

  • These are the four small glands of the endocrine system which regulate the calcium in our bodies.

  • These glands are located inside in the neck behind the thyroid where they continuously monitor and regulate blood calcium levels.

Adrenal Glands

  • These are small glands located on top of each kidney.

  • They produce some very prominent hormones such as sex hormones and cortisol.

  • Cortisol helps in reducing stress.

  • In case there is disorder glands make too much or not enough hormones.

  • Some of the ways in which this stress hormone helps the organism to either face a dangerous situation or to avoid it altogether are increasing blood sugar levels, Dilating the pupils, etc.


  • These glands are specific to males and females where ovaries are specific to females and are in the pelvic cavity.

  • Testis are specific to males.

  • Estrogen is produced by ovaries or reproduction and female sex characteristics.

  • Testosterone is produced by testes which is responsible for male sex characteristics.


  • The pancreas is exocrine as well as an endocrine gland.

  • It is 6 inches long and rather flat.

  • Two primary roles are producing digestive enzymes and producing hormones such as insulin and glucagon.

Pineal Gland

  • It is a small, pea-shaped gland in the brain.

  • It produces and regulates some hormones, including melatonin.

  • Melatonin plays a vital role in regulating sleep patterns.

  • Sleep patterns are also called circadian rhythms.