Interactive guide to the endocrine system
Use this interactive to explore the glands in the endocrine system.
Endocrine system
The endocrine system is a network of glands that produce hormones to regulate various bodily functions. Understanding how it works helps us see how our bodies maintain balance and respond to changes. Use this resource to explore how these glands and hormones work together to keep us healthy.
Endocrine glands
The endocrine system (or hormonal system) consists of a network of endocrine glands that produce hormones to regulate crucial processes in the body, like growth, metabolism, and mood. Together, these glands help to maintain balance in the body and make sure that we can respond effectively to internal and external changes.
Hormones
Hormones are chemical messengers produced by glands in the endocrine system. They allow your glands to communicate with different parts of your body to make sure your organs and systems are working together harmoniously.
Hormones are released into your bloodstream, where they can then travel to organs and tissues all around the body.
The endocrine glands, their location, functions and examples of hormones involved are shown in the table.
| Gland | Location | Function | Hormones |
|---|---|---|---|
| Hypothalamus | Base of the brain | Regulates body temperature, hunger, thirst; controls the pituitary gland | Corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH) |
| Pituitary | Below the hypothalamus | Controls other endocrine glands; regulates growth and development | Growth hormone (GH), adrenocorticotropic hormone (ACTH) |
| Thyroid | Neck, below the Adam’s apple | Regulates metabolism and energy use | Thyroxine (T4), triiodothyronine (T3) |
| Parathyroid | On the thyroid gland | Regulates calcium levels in the blood | Parathyroid hormone (PTH) |
| Thymus | Upper chest, behind the sternum | Develops immune system cells | Thymosin |
| Adrenal | On top of each kidney | Manages stress and regulates metabolism and electrolyte balance | Cortisol, adrenaline |
| Pancreas | Upper abdomen, behind the stomach | Regulates blood sugar levels | Insulin, glucagon |
| Ovaries | Pelvis, on either side of the uterus | Produces sex hormones for reproduction | Estrogen, progesterone |
| Testes | Scrotum | Produces male sex hormones and sperm | Testosterone |
| Pineal | Middle of the brain | Regulates the sleep–wake cycle | Melatonin |
Watch this video for an overview of how hormones work.
Over the course of our lifetimes, our bodies undergo a series of extraordinary metamorphoses: we grow, experience puberty, and many of us reproduce. Behind the scenes, the endocrine system works constantly to orchestrate these changes.
Alongside growth and sexual maturity, this system regulates everything from your sleep to the rhythm of your beating heart, exerting its influence over each and every one of your cells.
The endocrine system relies on interactions between three features to do its job: glands, hormones and trillions of cell receptors.
Firstly, there are several hormone-producing glands: three in your brain, and seven in the rest of your body. Each is surrounded by a network of blood vessels, from which they extract ingredients to manufacture dozens of hormones. Those hormones are then pumped out in tiny amounts, usually into the bloodstream.
From there, each hormones needs to locate a set of target cells in order to bring about a specific change. To find its targets, it's helped along by receptors, which are special proteins inside or on the cell's surface. Those receptors recognise specific hormones as they waft by and bind to them.
When this happens, that hormone-receptor combination triggers a range of effects that either increase or decrease specific processes inside the cell to change the way that cell behaves.
By exposing millions of cells at a time to hormones in carefully-regulated quantities, the endocrine system drives large-scale changes across the body.
Take, for instance, the thyroid and the two hormones it produces, triiodothyronine and thyroxine. These hormones travel to most of the body's cells, where they influence how quickly those cells use energy and how rapidly they work. In turn, that regulates everything from breathing rate to heartbeat, body temperature, and digestion.
Hormones also have some of their most visible—and familiar—effects during puberty. In men, puberty begins when the testes begin secreting testosterone. That triggers the gradual development of the sexual organs, makes facial hair sprout, and causes the voice to deepen and height to increase.
In women, estrogen secreted from the ovaries signals the start of adulthood. It helps the body develop, makes the hips widen, and thickens the womb's lining, preparing the body for menstruation or pregnancy.
An enduring misconception around the endocrine system is that there are exclusively male and female hormones. In fact, men and women have estrogen and testosterone, just in different amounts.
Both hormones play a role in pregnancy, as well, alongside more than 10 other hormones that ensure the growth of the fetus, enable birth, and help the mother feed her child.
Such periods of hormonal change are also associated with fluctuations in mood. That's because hormones can influence the production of certain chemicals in the brain, like serotonin.
When chemical levels shift, they may cause changes in mood, as well. But that's not to say that hormones have unlimited power over us.
They're frequently viewed as the main drivers of our behaviour, making us slaves to their effects, especially during puberty. But research shows that our behaviour is collectively shaped by a variety of influences, including the brain and its neurotransmitters, our hormones, and various social factors.
The primary function of the endocrine system is to regulate bodily processes, not control us. Sometimes disease, stress, and even diet can disrupt that regulatory function, however, altering the quantity of hormones that glands secrete or changing the way that cells respond.
Diabetes is one of the most common hormonal disorders, occurring when the pancreas secrets too little insulin, a hormone that managed blood sugar levels. And hypo- and hyperthyroidism occur when the thyroid gland makes too little or too much thyroid hormone.
When there's too little thyroid hormone, that results in a slowed heart rate, fatigue and depression, and when there's too much thyroid hormone, weight loss, sleeplessness, and irritability.
But most of the time, the endocrine system manages to keep our bodies in a state of balance. And through its constant regulation, it drives the changes that ultimately help us become who we are.
We will just look at the hypothalamus, pituitary gland and pancreas in more detail, but you can explore the Further resources at the end of the page to learn more about the other glands and how they function.
Did you know?
Ever heard of the gut–brain connection? Serotonin, a hormone that helps regulate mood, is also found in the digestive system, highlighting this connection.
The hypothalamus and pituitary gland
The hypothalamus is a small but crucial part of the brain located at its base. It acts as a bridge between the nervous and endocrine systems, helping to regulate body temperature, hunger, thirst, and emotions.
The hypothalamus monitors the body's internal environment and responds by releasing hormones that communicate with the pituitary gland. These hormones ensure the body maintains balance and reacts properly to changes, like stress or external temperature shifts. You can learn more about homeostasis and the body's balancing act on the Homeostasis page.
Did you know?
The pituitary gland is only about the size of a pea, yet it has a powerful influence on many body systems and processes.
The pituitary gland, known as the "master gland," sits just below the hypothalamus. Despite its small size, it plays a significant role in controlling other endocrine glands.
The pituitary gland releases hormones that influence growth, metabolism, and reproduction. For example, growth hormone helps control how the body grows, while adrenocorticotropic hormone (ACTH) stimulates the adrenal glands to produce cortisol, a vital stress hormone.
Together, the hypothalamus and pituitary gland coordinate many essential bodily functions. They ensure that hormones are released in the right amounts and at the right times, keeping the body's systems running smoothly. This teamwork between the brain and the endocrine system is key to overall health and well-being.
The pancreas
The pancreas is a vital organ located in the upper abdomen, behind the stomach.
It has two main functions:
- producing enzymes that help digest food in the small intestine
- releasing hormones that regulate blood sugar levels.
To perform its function in the endocrine system, the pancreas makes the hormone insulin, which lowers blood sugar, and glucagon, which raises it, helping maintain balance.
Its role in digestion and blood sugar control is essential for keeping the body healthy. You can learn more about blood sugar regulation in Homeostasis.
You can use this interactive model to see how the pancreas interacts with the duodenum, a part of the digestive system.
Pancreas and duodenum by Ebers via Sketchfab, licensed under Standard Sketchfab License
An interactive three-dimensional model of the pancreas and duodenum, a part of the small intestine. Parts of the pancreas, duodenum and surrounding tissue are annotated with descriptions.
- Pancreas: The pancreas is an organ located in the abdomen. It plays an essential role in converting the food we eat into fuel for the body's cells. The pancreas has two main functions: an exocrine function that helps in digestion and an endocrine function that regulates blood sugar.
- Duodenum: The duodenum is the first part of the small intestine. It is located between the stomach and the middle part of the small intestine, or jejunum. After foods mix with stomach acid, they move to the duodenum, where they mix with bile from the gallbladder and digestive juices fro the pancreas.
- Pancreatic duct: The pancreatic duct, or duct of Wirsung (also, the major pancreatic duct due to the existence of an accessory pancreatic duct), is a duct joining the pancreas to the common bile duct to supply pancreatic juice provided from the exocrine pancreas, which aids in digestion.
- Common bile duct: The common bile duct is a small, tube-like structure formed where the common hepatic duct and the cystic duct join. Its physiological role is to carry bile from the gallbladder and empty it into the upper part of the small intestine (the duodenum). The common bile duct is part of the biliary system.
- Portal vein: The portal vein or hepatic portal vein is a blood vessel that carries blood from the gastrointestinal tract, gallbladder, pancreas and spleen to the liver. This blood contains nutrients and toxins extracted from digested contents.
- Abdominal aorta: The abdominal aorta is a continuation of the descending thoracic aorta. It supplies all of the abdominal organs, and its terminal branches go on to supply the pelvis and lower limbs. It also supplies the undersurface of the diaphragm and parts of the abdominal wall.
- Merging of pancreatic duct and common bile duct
Exercise
See how well you understand the endocrine system and its function with a quick quiz.
