The endocrine system consists of endocrine glands that produce hormones. These hormones function as chemical messengers that circulate through the body and tell other organs and tissues what to do. By doing this, the endocrine system plays a vital role in helping the body to coordinate all of its activities and maintain homeostasis.
This post gives an overview of the endocrine system anatomy & physiology. It also highlights the most important components and functions that a massage student or therapist needs to know to prepare for the MBLEx.
Primary functions of the endocrine system
The primary function of the endocrine system is regulation of other body organs and tissues. It does this by secreting hormones, which are very small and powerful chemical messengers.
For example, the hormone thyroxine (T4) is produced in the thyroid gland and then it travels through the bloodstream to affect almost every other system in the body. It plays and important role in metabolism, heart function, digestive function, brain development and muscle control.
In order for the body to maintain homeostasis and function properly, all organs must work in harmony. The hormones produced by the endocrine system are like the body’s internal communication system. Once produced by the endocrine glands, hormones are then secreted into the tiny capillaries around the gland, and then carried by the bloodstream to their target.
Some of the body functions that the endocrine system influences include: metabolism, growth and development, movement, respiration, cardiac output, reproduction, and sensory perception. Damage to an endocrine gland or other causes of hormone imbalance will usually affect multiple body systems.
The endocrine system works closely with the nervous system. In fact they both function as messenger systems within the body. The difference is that the endocrine system uses hormones to send its messages and the nervous system uses electrical signals to send its message.
Getting ready to take the massage exam? Be sure to check out our Ultimate Guide To Passing The MBLEx.
Components of the endocrine system
The endocrine system is composed of a collection of endocrine glands that produce hormones. Endocrine glands are different from exocrine glands. Exocrine glands like sweat glands and sebaceous glands have ducts that carry their substances to the surface. However the glands of the endocrine system are ductless. This means they secrete their hormones directly into the bloodstream via the tiny capillaries around the endocrine glands.
Once in the bloodstream, the hormones are carried throughout the body. Hormones only affect their target cells, which have specific receptor sites for the hormone. A hormone is kind of a tourist walking around the city looking for someone who speaks her language. When she finds someone who speaks her language then she can deliver her message. The message that the hormone is delivering is to tell the organ or tissues to do something, like speed up or slow down their work.
Below is a list of endocrine glands and a few of the main hormones that each gland produces. You may see one or two of these on the MBLEx. The depth and detail required on the MBLEx will likely be less than that required in your anatomy and physiology class. So focus on the major concepts and terminology.
The pituitary gland is known as the “master gland” because it controls the function of many other endocrine glands. This small gland that is located in a cavity within the sphenoid bone of the skull.
The pituitary is a single structure, but it is often divided into the anterior pituitary and posterior pituitary when discussing its different functions. The anterior pituitary gland produces more hormones, many of which target other endocrine glands. Hormones of the anterior pituitary gland include:
- Human growth hormone (hGH)
- Adrenocorticotropic hormone (ACTH)
- Follicle-stimulating hormone (FSH)
- Thyroid-stimulating hormone (TSH)
- Luteinizing hormone (LH)
- Melanocyte-stimulating hormone
The hypothalamus functions as a bridge between the nervous system and the endocrine system. It is located just above the pituitary gland, and anterior to the brain stem. The hypothalamus controls the pituitary gland to a great extent. It also produces the hormones oxytocin and antidiuretic hormone (ADH).
The pineal gland is a pea-sized gland in the brain that produces melatonin, which regulates the body’s sleep cycle. This is also known as circadian rhythm.
The thyroid gland is a butterfly-shaped endocrine gland located on the anterior side and wrapping around to the lateral sides of the trachea. It produces 3 main hormones:
- Triiodothyronine (T3): works to regulate metabolic rate and increase cellular activity.
- Thyroxine (T4): similar function as T3.
- Calcitonin: regulates the amount of calcium ions in the blood.
The parathyroid gland consists of 4 small masses of endocrine tissue located on the posterior side of the thyroid gland. It produces the hormone parathyroid hormone (PTH), which is used to regulate the balance of calcium ions and phosphorus levels in the blood.
The pancreas is located behind the stomach, and has both endocrine and exocrine functions. As an exocrine gland, it is an accessory organ to the digestive system. The endocrine function of the pancreas involves a very small part of the organ (about 1% by mass), but it is a very important role.
Cells in the islets of Langerhans produce 2 hormones that help regulate blood glucose levels.
- Alpha cells: produce glucagon which raises blood glucose levels
- Beta cells: produce insulin which lowers blood glucose levels
There are two adrenal glands, one at the superior aspect of each kidney. The adrenal glands (also called the suprarenal glands because of their location) produce three classes of hormones.
- Glucocorticoids: involved with the immune response and in the production of glucose.
- Mineralocorticoids: help to regulate the balance of minerals in the body.
- Androgens: hormones involved with growth.
These endocrine glands are the ovaries and testes. The gonads produce hormones such as testosterone, progesterone and estrogen, which are involved with growth and development.
The thymus is located behind the sternum. It plays a role in the development of the body’s immune function during childhood. After puberty, the job of the thymus is over and the gland gets replaced by adipose tissue.
Interaction between the endocrine system and other systems
The endocrine system has a lot of influence over the activities of other body systems and organs. These systems also influence the endocrine system. The following is a few basic ways that these systems interact.
The endocrine system uses hormones to regulate heart rate, blood pressure, blood volume, red blood cell production, and strength of heart contractions. The circulatory system helps the endocrine system by transporting hormones to their target organs and tissues.
Hormones affect muscle growth and strength, as well as control smooth muscle activity.
The skeletal system provides protection for glands such as those in the cranial cavity, and the thymus located behind the sternum. The endocrine system uses hormones to regulate calcium levels, skeletal growth and development.
Hormones of the endocrine system can affect integumentary system by effecting skin coloring, hair growth, and the activity of sebaceous glands.
The hormone epinephrine produced by the adrenal glands affects the respiratory system when exercising or under stress (part of the “fight or flight” response). Epinephrine widens the airways to facilitate breathing.
Hormones of the endocrine system such as aldosterone and antidiuretic hormone influence kidney function. The kidneys in turn help to break down and eliminate inactivated hormones.
The endocrine system helps to regulate the production of enzymes produced by the digestive system. Hormones influence the motility of the intestinal tract by affecting the smooth muscle in the wall of the GI tract.
Glucocorticoids produced by the adrenal glands help to suppress the immune response and decrease inflammation.
Hormones help in the development and normal function of the nervous system. The parathyroid hormone regulates calcium ion levels, which are needed to generate nerve impulses.
Hormones of the endocrine system play a major role in the development and function of reproductive organs.
How massage therapy affects the endocrine system
Massage therapy likely has a physiological affect on the endocrine system. For example, many types of massage will stimulate a relaxation response. This response is usually associated with a decrease in hormones such as cortisol.
Massage and bodywork also activates the parasympathetic nervous system. This will stimulate a relaxed physiological and psychological state. A relaxed body and mind produces different hormones than one that is stressed or anxious.
A stressed body will produce the hormones adrenaline, norepinephrine and cortisol. On the other hand, a relaxed body will produce hormones like oxytocin, endorphins, serotonin and dopamine.
Research on specific affects of massage therapy is often inconclusive, biased or conflicting. It stands to reason though that the benefits of massage for conditions such as anxiety, depression, pain and stress aren’t due to dramatic changes in a single hormone, but rather a combined affect across multiple body systems.
This covers some of the most important aspects of the endocrine system that massage therapists will likely see on the MBLEx. If you have a few minutes, try out a couple of free practice quizzes.