Lesson Video: The Pituitary Gland Biology

In this video, we will learn how to describe the structure and the function of the pituitary gland in the human body.


Video Transcript

In this video, we will learn about the structure and function of the pituitary gland. This is a gland that plays such an important role that it’s often called the master gland. First, we will understand the anatomy of this endocrine gland, and then we will learn about the main hormones released from the pituitary gland and how they affect the human body. We’ll discover how this small gland can orchestrate almost all aspects of our lives, from our growth and metabolism to our reproduction and even our social interactions and empathy to others.

The pituitary gland belongs to the endocrine system, which is a series of glands in the body that secrete chemical messengers called hormones. In addition to the pituitary gland that sits just under the brain, some of the endocrine glands of the endocrine system are represented in this diagram, for example, the thyroid gland, the pancreas, the adrenal glands, and the gonads, which in biological females are the ovaries and in biological males are the testes. They’re both represented in the same person on this diagram even though usually only one would be found in a person.

Hormones are released by the cells in these endocrine glands and into the blood. Once in the blood, the hormones can travel throughout the entire body. Eventually, they’ll reach specific cells called target cells. Once hormones reach their target cells or organs, they can act on these cells to cause an effect. Hormones can regulate the functions of their target cells in order to adapt our body to our needs or to the changes in our environment. This maintains the normal functioning of our body. In other words, hormones contribute to maintain homeostasis, which is the fine balance that our body maintains to make all the body functions work in harmony.

Now let’s take a closer look at the anatomy of the pituitary gland. As we mentioned, this gland is located just under the brain. It’s attached to a brain region called the hypothalamus by a stalk called the infundibulum. The gland is divided into two main lobes: the anterior lobe, which is located closer to the front of the brain, and the posterior lobe, which is located closer to the back of the brain. Something that may help you remember this is that A is closer to the front of the alphabet than P. So the anterior lobe is closer to the front of the brain than the posterior lobe.

As with many endocrine glands, there is a rich network of blood vessels around both lobes of the pituitary gland to collect the hormones that they release and bring them to their diverse targets located throughout the entire body. These targets can be all sorts of different cells and different endocrine glands. This is why the pituitary gland is sometimes called the master gland.

Now let’s detail this anatomy a bit more, as these two lobes are organized and function quite differently. The posterior lobe of the pituitary gland is more a storage place for hormones that are fabricated in specialized neurons located in the hypothalamus. The posterior lobe releases hormones depending on neuronal signals processed in the brain by the hypothalamus. Because this part is controlled directly by neuron activity, it’s sometimes called the neurohypophysis.

In contrast, the anterior lobe is a gland that contains endocrine cells. These cells produce their hormones and release them into the bloodstream depending on signals that they received via the blood. This part of the pituitary gland can also be called the adenohypophysis, where the prefix adeno- means gland in Greek.

Now let’s have a look at the hormones released by these two lobes of the pituitary gland, starting with the posterior lobe. This lobe secretes two hormones: ADH, which stands for antidiuretic hormone and is also commonly known as vasopressin, and oxytocin. ADH acts on the kidneys. As indicated by its name, antidiuretic hormone, it acts to reduce urination. This hormone is particularly important to maintain the water balance in our body. Its other name, vasopressin, can help us remember that it controls our blood pressure by constricting our blood vessels.

Oxytocin is released in high quantities during childbirth and during breastfeeding because it stimulates uterine contractions and also the release of milk from the mammary glands. Oxytocin also plays a very important role in both males and females in the attachment with infants but also in the empathetic bonds that we form with our friends, romantic partners, or even pets. This is why oxytocin is sometimes nicknamed the love hormone.

Now let’s have a look at the hormones released by the anterior lobe of the pituitary gland. GH, or growth hormone, acts on many different cells in our body, particularly our bones and muscles, to make us grow when we are children. In adults, it still modulates our metabolism, helping us to build muscles and strengthen our bones.

TSH, or thyroid-stimulating hormone, acts on the cells of the thyroid gland to make them release hormones. TSH is thus called a tropic hormone, as it acts on cells in other endocrine glands. The word tropic comes from the Greek tropikos, which means change or turn. Indeed, tropic hormones are able to turn on and off other endocrine glands. Tropic hormones often have the suffix tropic or tropin in their name. For example, another name given to TSH is thyrotropin, which in Greek means thyroid change. As we mentioned, the changes in the thyroid gland that TSH stimulates is that it releases thyroid hormones. As a result, TSH helps us to regulate our level of energy, body temperature, metabolism, and our blood pressure. Thyroid hormones are also very important for our growth and our brain development.

ACTH, or adrenocorticotropic hormone, is a hormone that has a tropic effect too. But this time, it’s on the cortex of the adrenal glands. ACTH is released in response to stress and makes the adrenal glands release cortisol, a hormone that regulates our metabolism, blood pressure, or immune responses.

The last group of hormones released by the anterior lobe of the pituitary gland is a group of gonadatropic hormones called gonadotropins. As indicated by the name, these hormones have a tropic effect on the gonads. This means that they stimulate the release of other hormones by the gonads. Remember the gonads are our sexual glands, the ovaries in biological females and the testes in biological males. In males and females, these gonadotropins are FSH, or follicle-stimulating hormone, and LH, or luteinizing hormone. They are essential for the development of the sexual organs during puberty and for the function of the reproductive systems, especially with the production of gametes and sex hormones.

There are two more hormones secreted by the pituitary gland that we can mention too. Prolactin is important for the production of milk or lactation. Lactation occurs during breastfeeding in females. 𝛽-endorphins reduce our perception of pain and make us feel good while exercising, listening to music, or eating chocolate.

Let’s see how much we’ve learned about the pituitary gland by applying our knowledge to some practice questions.

ADH and oxytocin are released by the posterior pituitary gland. In what structure are they produced?

This question asks us about hormones released from the pituitary gland, which is a small gland about the size of a pea located under the brain. The pituitary gland is divided into two lobes according to which side of the brain they’re closest to: the anterior or frontal part of the brain or the posterior lobe, which is located closer to the back of the brain. Let’s take a closer look at the pituitary gland so we can see these lobes more clearly.

The two lobes of the pituitary gland have a different structure and they also function a bit differently. The anterior, or frontal, lobe contains cells that produce and secrete a wide variety of hormones into the blood that will modulate the activity of many different tissues in the body. For example, the anterior lobe produces and releases growth hormones, or GH, that act on our muscles and bones to stimulate our growth and metabolism.

The anterior lobe also releases various hormones that are said to be tropic because they can stimulate the release of other hormones by other endocrine glands, for example, ACTH that stimulates the adrenal glands. These hormones and many others can then be transported via the blood to their target cells.

In contrast, the posterior lobe of the pituitary gland is not a site of production of hormones. It’s rather a site of storage of hormones. In fact, this part contains the terminals of specialized neurons that have the capacity to produce hormones that can then be released into the blood. Some of the hormones that are released from the posterior pituitary gland include ADH, or antidiuretic hormone, and a hormone called oxytocin. The cell body of the neurons that produce these hormones is located in a region of the brain called the hypothalamus.

Neurons in the hypothalamus process the information coming from the entire body and the environment, which is why the hypothalamus is considered a control center that coordinates the nervous system and the endocrine system. When stimulated, these neurons send a signal along their axons and to their axon terminals to command the release of hormones into the blood. Therefore, the answer to this question that’s asking us where ADH and oxytocin are produced is the hypothalamus.

Let’s try another practice question together.

Thyrotropin in as an example of a tropic hormone released from the pituitary gland. What is a tropic hormone? (A) A hormone that is insoluble in the body. (B) A hormone that is transmitted via the lymphatic system rather than the bloodstream. (C) A hormone that is only released in response to stress. Or (D) a hormone that influences the activity and secretions of other endocrine glands.

The pituitary gland is often referred to as the master gland, mainly because this endocrine gland releases hormones that target other endocrine glands in the body. We can see some of these endocrine glands in this diagram of the endocrine system. Through their effects on other endocrine glands, pituitary gland hormones can control the release of various other hormones and indirectly control many more functions of the body. One example of a pituitary hormone is thyrotropin, which you might know better as TSH, or thyroid-stimulating hormone.

Thyrotropin stimulates the thyroid gland to control the secretion of various thyroid hormones. In turn, these hormones regulate many target tissues in the body. Thyrotropin in is a typical example of a tropic hormone, which is a hormone that influences the activity and secretion of other endocrine glands. The suffix -tropin and the adjective tropic mean in ancient Greek to change or to turn. So if you meet the suffix in the name of a hormone, you can guess its function.

Thyrotropin is a hormone that changes the activity of the thyroid. Gonadotropin is a hormone that changes the activity of the gonads. And ACTH, which is short for adrenocorticotropic hormone, is a hormone that changes the activity of the cortex of the adrenal glands. Therefore, we’ve worked out the answer to our question that a tropic hormone is a hormone that influences the activity and secretions of other endocrine glands.

Let’s summarize the key points that we’ve learned in this video about the pituitary gland. The pituitary gland is made up of the adenohypophysis, which is otherwise known as the anterior lobe, and the neurohypophysis, which is otherwise known as the posterior lobe. The posterior lobe releases hormones that are made in the hypothalamus, such as ADH and oxytocin. The anterior lobe releases tropic hormones that affect the activity of other endocrine glands, for example, TSH, ACTH, and gonadotropins. The anterior lobe also releases hormones that don’t have a tropic effect but directly regulate certain cell functions, such as growth hormone, prolactin, and 𝛽-endorphins.

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