The Pituitary Gland a “Master Gland”
By W. Jean Rohrer
If the endocrine system, or ductless glandular system can be compared to an orchestra, then the pituitary, as one source describes it, plays first violin. This pea-sized gland is so important to the body that it is nested in a tiny cavity at the base of the skull in the sphenoid bone, and attached to the brain by a stalk of tissue. Demonstrative of the adage “Good things come in small packages” the pituitary is divided into ante and posterior lobes, each of which secretes several hormones that control the function of other endocrine glands and organs throughout the body. Because the pituitary is so involved in not only reproduction but in milk production in new moms, this gland tends to be slightly larger in women than in men.
So here's this tiny little organ with seven hormones capable of influencing the entire body. But how does the pituitary know when to secrete a particular hormone and how much? Or when to send the cut‑off signal? The adenohypophysis has only endocrine function; it has no direct connection to the rest of the body. Therefore it's up to the controlling hypothalamus to send chemical messengers via the bloodstream through the pituitary stalk to the anterior lobe. Once these specific messengers reach the anterior pituitary, it immediately secretes the appropriate hormone into the blood stream. It is therefore quite obvious that anything that impairs blood flow, either generally or especially into and through the pituitary stalk, radically impairs the function of this all‑important gland.
The posterior lobe of the pituitary may seem less important; after all, it (only!) secretes two hormones. As the term neurohypophysis implies, it is embryologically developed from nerve tissue. This posterior lobe contains nerve endings from the hypothalamus, which cause production or suppression of hormones. Again, the communication with the hypothalamus is via that vital pituitary stalk.
As puberty begins and the gonads start producing their hormones, the hypothalamus receives the cut-off signal, and notifies the pituitary to decrease and then stop producing growth hormone. One source describes the action of gonadal sex hormones as "neutralizing" growth hormone.
There is no way the human organism can survive without the pituitary gland. The number and scope of actions of the multiple hormones involve the entire body. A normally functioning pituitary keeps the body in harmony and all systems working as they are designed to do. Malfunction, whether from either too much or too little hormone, has enormous consequence for the body both in structure and in the functioning of other organs. The pituitary's interactive ability and its capacity to respond rapidly as needed yet maintain prolonged stimulus for the long human growth period is truly amazing. It's not called the master gland for nothing!
What Is the Endocrine System?
Although we rarely think about the endocrine system, it influences almost every cell, organ, and function of our bodies. The endocrine system is instrumental in regulating mood, growth and development, tissue function, metabolism, sexual function and reproductive processes.
In general, the endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes like breathing and body movement are controlled by the nervous system. But even though the nervous system and endocrine system are separate systems, they often work together to help the body function properly.
The foundations of the endocrine system are the hormones and glands. As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another. Many different hormones move through the bloodstream, but each type of hormone is designed to affect only certain cells.
A "gland" is a group of cells that produces and secretes, or gives off, chemicals. A gland selects and removes materials from the blood, processes them, and secretes the finished chemical product for use somewhere in the body.
Some types of glands release their secretions in specific areas. For instance, exocrine glands, such as the sweat and salivary glands, release secretions in the skin or inside the mouth. Endocrine glands, on the other hand, release more than 20 major hormones directly into the bloodstream where they can be transported to cells in other parts of the body.
The major glands that make up the human endocrine system include the:
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