the master gland
the pituitary gland
Although hormones are produced in various glands dispersed within the body, one gland functions as a coordinator of those glands - the pituitary gland. This gland is about the size of a bean. It has two lobes: an anterior (front) and posterior (back) lobe. The posterior lobe is an anatomical extension of the hypothalamus. Nerves from the hypothalamus traverse into the posterior lobe. The anterior lobe, however, is a tissue which has been fused on.
This image provides a sense of scale to help visualize the size of the pituitary gland.
The way in which the pituitary gland coordinates other glands is by releasing various hormones stored within it.
The anterior lobe and the posterior lobe behave completely independently.
Although the diagram may seem confusing, it is important to understand that there are two systems being shown. Due to anatomical reason, the systems overlap each other, however they do not interact.
The posterior lobe
Nerves from the hypothalamus travel down to the posterior lobe. Hormones stored at the tips of those nerves are released. These hormones enter the capillaries of the posterior pituitary gland, which in turn releases other hormones into the blood stream.
The anterior lobe
This lobe is not an extension of the hypothalamus. Nerves from the hypothalamus run to that direction but stop short. The capillaries from the anterior lobe, however, extend further up to interact with those nerves. This allows for a similar procedure to occur. Hormones from the nerves are released into the capillaries. These hormones migrate to the anterior lobe, which in turn releases the appropriate subsequent hormones to various target glands.
The anterior lobe and the posterior lobe behave completely independently.
Although the diagram may seem confusing, it is important to understand that there are two systems being shown. Due to anatomical reason, the systems overlap each other, however they do not interact.
The posterior lobe
Nerves from the hypothalamus travel down to the posterior lobe. Hormones stored at the tips of those nerves are released. These hormones enter the capillaries of the posterior pituitary gland, which in turn releases other hormones into the blood stream.
The anterior lobe
This lobe is not an extension of the hypothalamus. Nerves from the hypothalamus run to that direction but stop short. The capillaries from the anterior lobe, however, extend further up to interact with those nerves. This allows for a similar procedure to occur. Hormones from the nerves are released into the capillaries. These hormones migrate to the anterior lobe, which in turn releases the appropriate subsequent hormones to various target glands.
The posterior lobe releases two hormones to two glands. The anterior lobe releases six hormones to various glands and tissues.