Endocrine System What Is It ? & Its Functions With Labelled Diagram

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Endocrine System | What Is The Endocrine System ? | Endocrine System Diagram

The endocrine system is a network of glands that produce and release hormones that
help to control many important body functions, especially the body’s ability to change
calories into energy that powers cells and organs.

Endocrine System Function | Endocrine System Labeled Anatomy

The main function of endocrine glands is to secrete hormones directly into the
bloodstream. Hormones are chemical substances that affect the activity of another part of the body (target site). In essence, hormones serve as messengers, controlling and co ordinating activities throughout the body.

Upon reaching a target site, a hormone binds to a receptor, much like a key fits into a lock. Once the hormone locks into its receptor, it transmits a message that causes the target site to take a specific action. Hormone receptors may be within the nucleus or on the surface of the cell. Ultimately, hormones control the function of entire organs, affecting such diverse processes as growth and development, reproduction, response to stimuli (stress and injury) and sexual characteristics. Hormones also influence the way the body uses and stores energy and control the volume of fluid and the levels of salts and sugar (glucose) in the blood. Very small amounts of hormones can trigger very large responses in the body.
Although hormones circulate throughout the body, each type of hormone influences only certain organs and tissues. Some hormones affect only one or two organs, whereas others have influence throughout the body. For example, thyroid stimulating hormone, produced in the pituitary gland, affects only the thyroid gland. In contrast, thyroid hormone, produced in the thyroid gland, affects cells throughout the body and is involved in such important functions as regulating growth of cells, controlling the heart rate, and affecting the speed at which calories are burned.

Insulin, secreted by the islet cells of the pancreas, affects the processing (metabolism) of glucose, protein and fat throughout the body. Most hormones are proteins. Others are
steroids, which are fatty substances derived from cholesterol.

Glands of the Endocrine System

Each gland of the endocrine system releases specific hormones into bloodstream. These hormones travel through blood to other cells and help control or co-ordinate many body
processes. Endocrine glands include:

Pituitary gland: A gland found at the base of brain behind the sinuses. It is often called the “master gland” because it influences many other glands, especially the thyroid. The pituitary gland produces several hormones. The front part of pituitary gland commonly called the anterior pituitary produces the following types of hormones:

  •  Growth hormone: Growth hormone promotes the growth in childhood. For adults, it helps to maintain healthy muscle and bone mass.
  •  Prolactin: In women, it stimulates milk production. In males, low levels are linked to sexual problems; however, in most of the males, these hormones are inactive.
  •  Adrenocorticotropic hormone: This hormone promotes the production of cortisol, which helps to reduce stress, and maintains healthy blood pressure.
  • Thyroid-stimulating hormone: This hormone helps to regulate the body’s thyroid, which is crucial in maintaining a healthy metabolism.
  •  Luteinizing hormone: In women, this hormone regulates estrogen. In men, it regulates testosterone.
  •  Follicle-stimulating hormone: Found in both men and women. It stimulates the releasing of eggs in women and in man, it helps ensure the normal function of sperm production.
  •  The back part of the pituitary gland is called the posterior pituitary. It produces the following two hormones:
  • Oxytocin: Oxytocin is involved in a variety of processes, such as contracting the uterus during childbirth and also promotes milk flow in nursing mothers.
  • Antidiuretic hormone: Commonly referred to as vasopressin, this hormone helps to regulate water balance in the body


A part of brain that controls hormone production by releasing different chemicals to the pituitary gland. The hypothalamus is in control of pituitary hormones by releasing the following types of hormones:

  •  Thyrotrophic-releasing hormone
  •  Growth hormone-releasing hormone
  • Corticotrophin-releasing hormone
  • Gonadotropin-releasing hormone
Adrenal glands: Two adrenal glands located on the top of the kidneys’ release the hormone cortisol and adrenaline. Adrenal glands are involved in:
  •  Promoting proper cardiovascular function.
  •  Properly utilizing carbohydrates and fats.
  •  Helps to distribute stored fat.
  •  Promotes healthy gastrointestinal functions.
  • Thyroid: A butterfly-shaped gland in the front of the neck that controls metabolism.
  • Ovaries: The ovaries are two small organs located on either side of the uterus

in a woman’s body that release eggs and produce sex hormones. This gland produces
both estrogen and progesterone, which promote the development of breasts. They
also help to maintain healthy menstrual periods.

Islet cells in the pancreas: Cells in the pancreas control the release of the hormones insulin and glucagon. The main function of the pancreas is to maintain healthy blood sugar levels.

Parathyroid: This gland is vital to proper bone development because it helps in controlling both calcium and phosphorous levels in the body. The parathyroid gland is actually a group of four small glands located behind the thyroid gland.

Pineal gland: A gland found near the center of the brain that may be linked to sleep patterns.

Testes: The male reproductive glands that produce sperm and sex hormone testosterone. It regulates production of sperm and stimulates the development and maintenance of male secondary sex characteristics, such as beard growth and deepening of the voice. Other functions of testosterone include:

  •  Maintaining sex drive.
  • Maintaining healthy levels of muscle and
    bone mass.

Thymus: This gland secretes hormones that are commonly referred to as humoral
factors and are important during puberty. The role of these hormones is to make sure a person develops a healthy immune system. Even the slightest hiccup with the function of one or more of these glands can throw off the delicate balance of hormones in body and lead to an endocrine disorder, or endocrine disease.


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