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Structures & Functions of the Endocrine System

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  • 0:55 The Endocrine System
  • 1:37 Control Glands
  • 2:48 Glands Controlled by…
  • 4:28 Glands Not Controlled…
  • 6:08 Types of Hormones
  • 6:50 Lesson Summary
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

This lesson will cover the basics of the endocrine system. We will discuss different types of hormones, and examine how the glands and hormones work together to make up this system.

The Endocrine System

The body is absolutely amazing! Think about everything that happens in the body on a day-to-day basis. Your digestive system breaks down food and converts it into energy. Your musculoskeletal system works with your nervous system to produce movement. Your immune system defends your body, and your urinary system gets rid of waste and maintains homeostasis in the body. Each of these systems carries out their functions and makes sure your body work like a factory.

The body, like all factories, has to know when to start and stop production of each of its products. When there's a need for a product, then the factory manager sends a signal that starts production of that product. When enough of the product is made, then the factory manager sends a signal that stops production of the product.

That is similar to what happens in the body. This process is carried out by the endocrine system, which is the body system that communicates and controls functions in the body. This control is maintained through chemical messengers called hormones that are released by glands, or cells or organs that secrete.

Want an example of a hormone? Let's discuss one that many people wish they could consciously control. Leptin is a hormone that indicates you are full and no longer hungry. This is often referred to as the satiety hormone. Being able to control the release of leptin would make weight loss much easier. We would all be able to release this hormone and no longer feel like we're hungry. No more overeating!

Control Glands

There are several glands located throughout the body and all of them are important. However, there are two glands in the brain that are like the masterminds of the other organs. The hypothalamus is a lot like the operations manager in a factory that makes sure every aspect of the factory is functioning optimally. The hypothalamus is a small gland in the brain that assesses the body's environment and releases hormones that control other glands. The hypothalamus essentially coordinates and dictates the activities of all other glands in order to keep the body functioning properly.

The other major gland in the brain is the pituitary gland. This is the gland that controls the rest of the endocrine system. This may start to seem like the body factory has two operations managers. The pituitary gland does control the rest of the endocrine system, but it does so under the direction of the hypothalamus. So the operations manager, or hypothalamus, tells the production manager, or pituitary gland, when production of the different hormones should start and stop. The pituitary gland is divided into the anterior and posterior pituitary glands.

Glands Controlled by the Pituitary Glands

Our first set of glands in the body are the ones controlled by the anterior pituitary gland. Let's look at each of these now.

The thyroid gland is the gland located in the neck between the larynx and trachea. Hormones are secreted by the thyroid when the anterior pituitary gland, or production manager, sends the signal to start production. The thyroid hormones directly affect metabolism and indirectly affect blood calcium levels.

The adrenal glands are the triangle-shaped glands that sit on top of the kidneys. There are two sections of the adrenal glands: the adrenal cortex and adrenal medulla. Only the adrenal cortex responds to the anterior pituitary gland. The hormones released by the adrenal cortex control blood pressure, the immune system, and energy conversion. The hormones of the adrenal medulla are released in response to stress.

The last pair of glands that are under control of the pituitary gland are the gonads or sex glands, which are glands that secrete sex hormones. We'll look at each of these separately, since they are different in males versus females.

Ladies first! The small, oval-shaped pair of female gonads are the ovaries, which secrete two different hormones that control the female reproductive cycle and the process of puberty.

The oval-shaped male gonads located in the scrotum are the testes. A hormone to control the development of male body characteristics is released by the testes when the production manager sends production signals to the testes.

Glands Not Controlled by the Pituitary Glands

Another gland that is located in the brain is the pineal gland, also sometimes called the third eye. It gets that nickname because it is activated based on signals from the optic nerve. So this gland isn't really part of the factory that works together. The pineal gland is a gland shaped similar to a corn kernel and secretes several hormones. The pineal gland hormones affect secretion of hormones from the ovaries and a person's sleep-wake cycle.

Our next gland is the parathyroid gland, which is the gland that surrounds the thyroid glands. The parathyroid gland is composed of four tiny glands that secrete PTH, which controls the blood calcium levels, allowing the muscular and nervous systems to function optimally. Parathyroid action is controlled by changes in calcium levels in the blood and does not change in response to another gland.

The pancreas is the flat gland attached to the small intestines behind the stomach that regulates blood glucose levels. Activation of the pancreas is controlled by detection of changes in blood glucose levels. Maintaining blood glucose levels is vitally important in order for the body to function as it should.

The final gland we are going to discuss is the thymus. The thymus is a two-lobed gland located in the upper chest between the lungs. Now that you are an adult, you don't have any use for this gland, and in fact, it has diminished since you hit puberty. A group of hormones are released by the thymus that make the T-cells of the immune system develop. This gland is of the utmost importance in causing the immune system to develop.

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