Endocrine System – Introduction, Structure & Functions

Human Endocrine System

The endocrine system helps to perform several body processes by the function of hormones including respiration, metabolism, sexual development, movement, sensory perception, reproduction, growth, etc.”Endo”  means “inside” and “crine” means” to secrete “

The fundamental functions of the endocrine system are long-distance intercellular communication, coordination, and maintain hemostasis.




A hormone is formed in one organ or gland and carried in the blood to another target organ or tissue, where it affects cellular activity, especially growth and metabolism.

Most hormones are synthesized from amino acids (amines, polypeptides, and proteins) or are cholesterol-based lipids.

Endocrine signaling

The endocrine system uses chemical signaling as a method of communication. Endocrine organ sent the chemical signal which secretes hormones or chemical into the extracellular fluid.

Hormones transported throughout the body via bloodstreams where they bind to receptors on target cells and develop a characteristics response.

So, endocrine signaling requires more time to prompt a response in target cells, though the precise amount of time varies with different hormones.

For example, the hormones released when you are confronted with a dangerous or frightening situation, called the fight-or-flight response, occur by the release of adrenal hormones—epinephrine and norepinephrine—within seconds.

Also Read: Cardiovascular system – Complete story of the heart & blood circulation

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In contrast, it may take up to 48 hours for target cells to respond to a certain reproductive hormone.




The endocrine signaling is typically less specific than. The same hormone may play a role in a variety of different physiological processes depending on the target cells involved.

For example, the hormone oxytocin promotes uterine contractions during labor pain.

It also plays an important role important in breastfeeding and may be involved in the sexual response and in feelings of emotional attachment in both males and females.

Structure Of The Endocrine System

The endocrine system consists of glands widely separated from each other with no direct anatomical links.

It also consists of the number of cells, tissue, and organs that secrete hormones. Endocrine glands are ductless glands as the hormones directly secreted and diffuse into the bloodstream.

The endocrine system consists of a number of distinct glands and some tissues in other organs. Although the hypothalamus is classified as a part of the brain and not as an endocrine gland it controls the pituitary gland and has an indirect effect on many others. The endocrine glands are:-



  • 1 Pituitary gland- Master gland of the body, It has two lobes, Present at the base of the brain in the form of a protrusion, Secretes 9 different major hormones
  • 1 Thyroid gland- One of the largest glands of the body, Found in the neck below the thyroid cartilage, Mainly controls body metabolism, Secretes 3 different hormones
  • 4 Parathyroid glands- Four in number, located behind the thyroid gland, produce parathormone
  • 2 Adrenal (suprarenal) glands- Found attached to the kidneys, Consists of two parts; Cortex and Medulla, Adrenal cortex produces 3 different hormones and adrenal medulla produces 4 different hormones
  • The pancreatic islets (islets of Langerhans)- Primarily an organ of the digestive system, produces 4 different hormones including Insulin and Glucagon
  • 1 Pineal gland
  • 1 Thymus gland
  • 2 Ovaries in the female
  • 2 Testes in the male.

The ovaries and the testes secrete hormones associated with the reproductive system after puberty.

Functions of the endocrine system:-

  • It secretes the hormones which play an important role to control growth and development, metabolism, organs, and reproduction in the human body
  • It also controls the level of hormones in the human body.
  • And homeostasis is also partly maintained by the endocrine system.




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