An Overview of some of the other Endocrine Glands

The Pineal Gland

The pineal gland is a tiny, pine cone-shaped gland, the size of a grain of rice in humans, located deep within our brains.

The pineal gland secretes the hormone melatonin, which helps us to sleep soundly during the night. The pineal gland is intimately involved in managing our night-day cycle of sleeping and waking patterns, i.e. our daily circadian rhythm.

The Hypothalamus

Underneath the pineal gland and the size of an almond in humans, sits the hypothalamus, which is actually part of the brain and nervous system as well as being a secretor of endocrine hormones.

The hypothalamus is the means by which we respond to everything going on around us and inside of us and manage to remain healthy through the appropriate influences and controls on the rest of the endocrine system.

The Pituitary Gland

The pituitary gland hangs from a small stalk at the base of the brain and is surrounded by bone for protection. It is a peanut-shaped gland, which is about the size of a pea in humans. It is divided into two parts that produce different control hormones: the anterior pituitary and the posterior pituitary.

The pituitary is sometimes known as the 'master gland' of the endocrine system because its role is to accurately control the action of the other endocrine glands.

Pituitary Negative Feedback Control

The pituitary gland works via a negative feedback loop.

In general, this means that when one of the target glands that it controls is not producing enough of a certain hormone then the pituitary gland will be instructed by the hypothalamus to raise the level of the stimulating hormone. When the target endocrine gland responds and produces more of the required hormone, then once the hypothalamus notices the increase, it will stop requesting the pituitary gland to stimulate the target endocrine gland.

It's an extremely clever system and works really well, until it doesn't!

The Parathyroid Glands

Humans usually have four parathyroid glands. These are situated at the rear of the thyroid gland. The parathyroid glands control the calcium levels in our blood and in our bones.

The parathyroid glands produce parathyroid hormone (PTH), which controls calcium and phosphate balance as well as the physiology of our bones. PTH has a variety of effects including raising blood calcium levels (by breaking down and releasing calcium in our bones), increasing calcium absorption in the digestive system and it also affects our sense of well being.

The Pancreas and Insulin

The pancreas has two distinct parts.

The exocrine pancreas secretes pancreatic juice containing the enzymes, which are essential for us to digest our food in the small intestine.

The endocrine part of the pancreas secretes insulin, glucagon and somatostatin in an area of the pancreas known as the islets of Langerhans.

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