Maintaining Balance: The Endocrine System

Your cells all communicate with one another. Similar to how we send messages to our friends and family, cells send signals to their neighbors or “distant” relatives using the endocrine and nervous systems. The endocrine system serves as a postal service for your body, delivering messages to all types of cells and tissues. Because of this, we are able to regulate cycles of imbalance, illness, mood, sexual reproduction, and growth. 

Basic Anatomy of the Endocrine System

The endocrine system is a collection of glands that secrete hormones to regulate internal body conditions, also known as homeostasis. While none of the eight major glands of this system are connected to one another, each function in correlation with the others to maintain balance throughout the body. Below, the anatomical position of each gland is shown:

Types of Glands

There are two main types of glands in the body: exocrine and endocrine. Exocrine glands are mostly seen in the integumentary system. Structures like sweat glands, oil glands, and mammary glands utilize ducts to transport their excretions to the surface of the body. Endocrine glands are the opposite, secreting hormones into the bloodstream that are shuttled around the inside of the body. Endocrine glands do not use ducts and secretions never exit the body. Instead, the secretions, called hormones, travel to cells with specific receptor sites to cause a bodily reaction. The main endocrine glands of the endocrine system are shown below:

Hormones

Hormones are the messengers of the body, traveling through the bloodstream to reach a target cell or tissue to cause a reaction. As with antibodies and antigens in the integumentary system, hormones utilize a “lock and key” pairing. Only cells with hormone receptors specific to the released hormone will react. Most of the reactions take time, happening in hours, days, or even weeks. Along with cellular communication, hormones aid in growth and development, sexual function, mood, reproduction, and metabolism. Here is a list of some of the most influential hormones:

• Adrenaline: secreted from the adrenal gland; released in short-term stressful situations to allow for quick responses to the stressor.

• Cortisol: secreted by the adrenal gland; controls the body’s response to long-term psychological and physiological stress. 

• Estrogen: secreted by the ovaries; female sex hormone; plays a role in female reproduction, menstruation, and menopause.

• Growth Hormone: secreted from the pituitary gland; stimulates growth, cellular reproduction, and metabolism.

• Insulin: secreted by the pancreas; converts glucose from food to be used as immediate energy or stores it for later use and maintains blood glucose levels

• Progesterone: secreted by the ovaries, adrenal glands, and placenta (during pregnancy); prepares the body for pregnancy and regulates the monthly cycle.

• Prolactin: secreted by the pituitary gland; only in females following childbirth – causes lactation for feeding the newborn.

• Testosterone: secreted by the testes; male sex hormone; plays a role in male development – forms reproductive tissues, increases muscle mass and body hair.

• Thyroid Hormones: secreted by the thyroid gland; control metabolism in the body to regulate weight, body temperature, and energy levels.

Hormones must be released in amounts that do not go over or under the necessary amount. Again, the endocrine system aims to maintain homeostasis, or internal balance, so the secretion of hormones is highly regulated. 

Want to know more about the human body? Check out this article!