The Endocrine System

Endocrine System

System that produces hormones

The endocrine system is a system of glands that release extracellular, long-range, signaling molecules known as hormones. The endocrine system regulates metabolism, growth, development and puberty, and tissue function and also plays a part in determining mood.^[1]

Each gland produces and releases exact quantities at precise moments. Problems occur when a gland produces an incorrect amount of hormones (too much or too little) or when target cells do not identify and absorb the hormone (ie. insulin resistance).

Endocrine system glands^[2]

• Hypothalamus
• Pineal body (epiphysis)
• Pituitary Gland (hypophysis)
  • Anterior pituitary lobe (adenohypophysis)
  • Posterior pituitary lobe (neurohypophysis)
  • Intermediate pituitary lobe (pars intermedia)
• Thyroid
• Parathyroid
• Heart*
• Striated muscle*
• Skin
• Adipose tissue*
• Stomach*
• Duodenum*
• Liver*
• Pancreas
• Kidney*
• Adrenal glands
  • Adrenal cortex
  • Adrenal medulla
• Testes
• Ovary
• During Gestation
• Placenta
• Uterus

There are four major forms of signaling in the endocrine system:

• Endocrine
• Autocrine
• Paracrine
• Juxtacrine

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 major endocrine glands are the pineal, pituitary, thyroid, thymus, pancreas, ovary/testes, and adrenal glands.

Endocrine glands

Endocrine glands are, in general, characterized by their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones.^[3]

Exocrine glands

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 than endocrine glands. These glands help metabolism in your body.^[4]

References:

[1] eMedicineHealth.com. “Anatomy of the Endocrine System.”
Available at:
http://www.emedicinehealth.com/anatomy_of_the_endocrine_system/article_em.htm
Accessed August 01, 2009.

[2] Wikipedia.org. “Endocrine System.”
Available at: http://en.wikipedia.org/wiki/Endocrine_system
Accessed August 01, 2009.

[3] MedlinePlus Medica Encyclopedia. “Endocrine Glands.”
Available at: http://www.nlm.nih.gov/medlineplus/ency/imagepages/1093.htm
Accessed August 01, 2009.

[4] ScienceDaily.com. “Exocrine Gland.”
Available at: http://www.sciencedaily.com/articles/e/exocrine_gland.htm
Accessed August 01, 2009.

* Thank you to Dr. Armando Gonzalez for pointing out that although this organ produces certain hormones, it is not commonly grouped/identified as an endocrine gland. [August 10, 2009]

** Thank you to Dr. Armando Gonzalez for pointing out that this organ helps in digestion of foods through the use of enzymes and not hormones. [August 10, 2009]