The human body is a prime example of the marvel that teamwork can bring about! Just like machines require the teamwork of several parts to operate perfectly, so also our body requires all its organs to coordinate properly. The circulatory system, nervous system and excretory system are well-known organ systems of the human body. However, two lesser known organ system, ones that don’t work towards a specific function, but labour to keep almost a hundred functions in order, are the Exocrine and Endocrine system.
The Exocrine System-
Exocrine glands are glands that pour their secretions- called enzymes- into ducts, which then direct these enzymes to the target organs. The exocrine glands and related ducts together form the exocrine system. For example, salivary glands, tear glands etc.
The Endocrine System-
Endocrine glands are glands that pour their secretions- called hormones- directly into the blood stream which then directs these hormones to the target organs. These organs form the endocrine system.
Each hormone or enzyme released performs a specific function and its effect is limited to a particular part only.
Since endocrine glands don’t need any ducts for their secretions, they are also called ductless glands. Their secretions are called hormones.
A chemical substance secreted from an endocrine gland, which is directly poured into the blood stream and acts on a target organ or cells is called a hormone.
There are several endocrine glands. The four most important ones are-
Thyroid Gland: The thyroid gland is a butterfly shaped gland with two lobes, situated on either side of the trachea, just below the voice box.
The hormone secreted by it is called thyroxin which is a protein that contains iodine.
This hormone accelerates most activities of the body. It stimulates growth in infants. Thus, we need to intake proper amounts of iodine salt.
This gland also secretes calcitonin that helps in bone generation.
The over-secretion of this hormone causes increased heartbeat, obesity and restlessness. Under-secretion causes goitre (swelling of thyroid gland) and myxedema (swelling of hands and feet) in adults and cretinism (lack of bone growth, underdevelopment) in children.
Adrenal Glands: Adrenal glands are situated like caps over the two kidneys. Each adrenal gland consists of a central medulla and a peripheral cortex.
The medulla part of these glands secretes a hormone called adrenaline which is also known as the emergency hormone. The rush of excitement we feel on a rollercoaster is all because of adrenaline. This hormone is secreted when the body is under severe stress, physically or emotionally. It prepares the body for fight or flight- it has made its presence felt since our ancient Neanderthal beginnings.
The cortex of the adrenal gland secretes cortisone which influences nutrient metabolism. It regulates salt and water in the body and also adapts the body to extreme physical stresses.
Pancreas: Pancreas is both, an exocrine as well as an endocrine gland. It secretes pancreatic juice which is an enzyme but the Islets of Langerhans are the hormone secreting cells of the pancreas. These cells secrete the hormones insulin and glucagon. Insulin lowers the sugar (glucose) level in the blood stream. Insufficient secretion of insulin causes diabetes. Glucagon stimulates the breakdown of glycogen (stored glucose) in the liver back to glucose. It thus raises sugar levels in the body.
Pituitary Gland: This is a pea sized gland located just below the brain. It secretes hormones that regulate the activities of other endocrine glands. Thus, this gland is also called the master gland.
The pituitary gland also secretes the growth hormone which regulates growth in the human body. Its Gonad Stimulating Gland stimulates the gonads to produce eggs and sperms. It also produces a hormone that controls the secretion of mammary glands at child birth.
These are but a few of the important endocrine organs in the human body, without which the body wouldn’t be able to function efficiently.