"An Introduction to Endocrinology and the Endocrine System"

Hi Everyone!!!

Guess what? I'm going to share to you (Yes, you my dear reader) some useful bits of info about a "fun to know" body system...

*drum roll please*

THE ENDOCRINE SYSTEM!!!

"The Endocrine System....ahuh?" " What are the substances secreted by the Endocrine glands ( which are also known as the ductless glands) , Hormones?... Glands?

"What on Earth am I pertaining to?!"

Come, spare some time reading and I will discuss some basic information about the world of ENDOCRINOLOGY...

Let's start with the ever boring definition portion.

Endocrinology is a branch of medicine which deals with the study of the Endocrine system of the human body. It also deals with the study of specialized glands and their corresponding Hormones they produce and secrete. This body of knowledge also deals with diseases associated with the endocrine glands and their specific hormones.

Ooookaayyy...I now you are thinking that this is going to be a difficult topic, well worry not because I will just be sharing to you the basics that you have to understand. :)

For starters, let's have a quick overview of the Endocrine System.

The Endocrine system is one of the most important systems in our body that secretes special substances called Hormones. The hormones regulate various activities and functions of the human body. This system has the control of the growth and development, metabolism of the body, the tissue functions and would you believe that it has also something to do with our moods, which means when we are in a good or a bad mood, don't just blame other people or circumstances, we might as well consider our body as the responsible for our mood. :)

The Hormones which are produced and secreted by the glands serve as the chemical messengers and are designed to relay information as well as instructions from one part of the body to the other. The main pathway in which the hormones travel inside our body is through our blood stream. These specialized chemicals are also designed to affect specific part or cells of the body.

The Endocrine Glands are glands of the said system which secrete the hormones, directly into the blood stream instead of using a duct.

Here are the Interaction of the Hormones to their corresponding target cells:

Permissiveness - which means that a hormone can not be secreted or produced without the secretion of another hormone.
Synergism - it happens when there a presence of two or more hormones that express the similar effects but also amplifying their function.
Antagonism - happens when a hormone regulates or reverses the effect or the other.

Now let's begin our journey inside to body and let's meet our different endocrine glands...let's start with our head! The main endocrine found inside our head, just below our brain is the Hypothalamus, which contains various types of neurons which are the ones responsible for the secretion of various hormones.

The Hypothalamus secretes six hormones which include:

Thyrotropin-releasing hormone (TRH)
Gonadotropin-releasing hormone (GnRH)
Growth hormone-releasing hormone (GHRH)
Corticotropin-releasing hormone (CRH)
Somatostatin
Dopamine

Fig.1
This shows a picture of the Hormones produced by the Hypothalamus as well as the Pituitary Gland
Image Credit: http://www.themagicisbac.com/bac-files/hypothalamic-complex.jpg

Yes, I know that these are new terms which are not easily memorized, but I promise you, in practice, you will be able to love and understand these new words. You might as well assign some Mnemonics in order to aid memorizing them.

After the Hypothlamus, is a gland which secretes a hormone that regulates our Circadian rhythm ( or our sleep-wake pattern). This gland is called the Pineal Gland and the hormone it secretes is called Melatonin. So if catching some ZZZzzZZzs is your thing, thank your Pineal gland. :)

Next, just below our hypothalamus, there is also a gland which is also known as the "Master Gland" or the Pituitary Gland which secretes hormones which are needed for the other glands in order to function. The Pituitary Gland is divided into two lobes namely: the Anterior Lobe and the Posterior Lobe.

The Anterior (front) Lobe produces the following hormones:

Thyroid-stimulating Hormone (TSH) and is also known commonly as Thyrotropin
Adrenocorticotrophic Hormone (ACTH)
Luteinizing Hormone (LH)
Follicle-stimulating Hormone (FSH)
Growth Hormone (GH)
Melanocyte-stimulating Hormone (MSH)
Prolactin

The Posterior (back) Lobe produces the following hormones:

Vasopressin or also commonly known as the Anti-diuretic Hormone (ADH)
Oxytocin

Fig 2.
This image shows the Hormones of the Pituitary Gland
as well as their corresponding target sites.
Image Credit: http://www.medicalook.com/systems_images/Pituitary_Hormones_large.jpg

As we go deeper inside our body, we head next to the Thyroid Gland. This gland can be located front part of our mid neckline. It is composed of two lateral lobes protruding on each side.

Now these two are the Hormones produced and are secreted to our body by our Thyroid Glands:

Triiodothyronine (T3)
Thyroxine (T4)

Fig. 3
This shows the interaction of the Pituitary gland to the Thyroid gland and
the Thyroid gland to the other cells of the body.
Image Credit: http://www.medcom.co.nz/images/hormones/Thyroidfunction1.gif

The gland has also specialized cells which produces Calcitonin, a hormone which is involved Calcium and Phosphorus metabolism. Located also within the Thyroid gland is the Parathyroid Gland which has Chief cells that produces the Parathyroid Hormone (PTH) which is responsible for the regulation of the Calcium and Phosphorus metabolism.

Traveling further inside our body, we go into our superior (upper) part of our abdomen. Our next endocrine gland is the Pancreas. It has also specialized cells which secrete various hormones responsible for the regulation of the glucose metabolism of our body. The specialized cells include the Islet of Langerhans which produces Glucagon (from the alpha cells) which raises blood sugar levels, Insulin (from beta cells) which functions the opposite of the Glucagon and Somastostatin (from delta cells) which inhibit various hormones and other substances secreted by our body.

Fig. 4
This image shows the different cells of the Pancreas
which secretes their corresponding hormones.
Image Credit: http://media-1.web.britannica.com/eb-media/17/74317-004-9B143D52.jpg

Fig. 5
A closer look at the Islet of Langerhans
Image Credit: http://scienceaid.co.uk/biology/humans/images/langerhans.png

Not far from the Pancreas, are the Adrenal Glands. These pair of glands are located just above our kidneys.

The Adrenal Glands has two portions namely the: Adrenal Cortex and Adrenal Medulla.

The Adrenal Cortex produces and secretes three hormones:

Cortisol
11-deoxycortisol
Aldosterone

The Adrenal Medulla on the other produces two namely:

Epinephrine (Adrenaline) also known as Fight or Flight Hormone
Norepinephrine

Fig. 6
The location of the Adrenal Gland as well as the hormones secreted by it.
Image Credit: http://www.emc.maricopa.edu/faculty/farabee/biobk/adcortx.gif

For our last destination, there glands (organs) are gender specific, which also means the hormones they secrete are dependent on the gender of the person. These are also responsible of the specific characteristics of each gender.

As the saying goes, "Ladies first", we will now tackle the female specific glands (organs), the Ovaries. The ovaries are also responsible for producing the egg cells of the female. As for their endocrine function, these secrete Estrogen which exists within the body of females in three forms which are called Estriol, Estradiol and Estrone. Take note that the true ovarian hormone is the Estradiol.

Fig. 7
This image shows the interaction of the Pituitary Gland
and the Ovaries through the use of hormones.
Image Credit: http://professionals.epilepsy.com/img/hormone_2_s.gif

The females also produces Human Chorionic Gonadotropin Hormone or hCG, which is produced by Placenta during pregnancy.

Now for the Males, the glands (organs) are the Testes. The testes are the ones responsible for the production of the sperm cells of the male. And for their endocrine function, these secrete the hormone Testosterone.

Fig. 8
The Testis
Image Credit: http://www.macmillan.org.uk/Images/Cancerinfo/Cancertypes/testicle_2011.jpg

Fig. 9
Chemical Structure of Testoterone
Image Credit: http://www.iimcs.org/wp-content/uploads/2012/01/Testosterone1.jpg

Well, that's it for the introduction and the overview of Endocrinology, the Endocrine System as well as the glands and hormones of our body.

Just never forget to reach for our own STARS!!!

Oh by the way, before I forget, there are also other hormones found inside the body which are not secreted by the endocrine glands that we need to be familiar with. These include the hormones which stimulates blood and platelet production; these hormones are the Erythropoietin and Thrombopoietin respectively.

Here a Picture of our Entire Journey of the Endocrine System inside the Human Body: