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Thursday, January 26, 2012

Hormones and Their Functions - Lesson 297

Endocrine glands are ductless glands. We will now see hormones and their functions. Exocrine glands have ducts to secrete their secretions inside the bloodstream, such as sweat glands. Exocrine gland functions are different from endocrine glands. They secrete chemical compounds named as hormones into the bloodstream to maintain some important functions of the body. Human brain has two important endocrine glands, such as pituitary and pineal gland in the center portion of the brain. Thyroid and parathyroid glands are present in the neck portion. Thymus gland is present behind the sternum in the mediastinum. Pancreas is an endocrine gland that is present in the liver. Adrenal glands are present above each kidney. Ovaries are present in the female reproductive system and testes are the endocrine glands that are present in the male reproductive system. Now we will see what are the hormones they secrete to maintain important functions of the human body. In fact, the functions of two endocrine glands, such as pineal gland in the center portion of the brain and thymus gland in the back of the sternum are unknown. But these two glands have no ducts and so are added in the endocrine glands group.

Animal Hormones and Their Functions

Now we will see some organs work as endocrine glands and secrete hormones and their functions. The pineal gland secretes a hormone named as melatonin. Melatonin involves in the process of skin pigmentation in the lower animals, for example frogs and fishes. In mammals, melatonin affects the brain and so influence the rate of gonad maturation. Sex glands like ovaries and testes in combination are termed as gonads. Thymus gland secretes a hormone named as thymosis, which helps in the development of immune response in children.  Thymus gland shrinks in size as the child grows.  Some organs like kidney secretes a hormone named as erythropoietin. Erythropoietin involves in the process of development of RBCs or red blood cells by bone tissues or bone marrow. The other three hormones named as cholecystokinin, gastrin, and secretin are secreted by intestines that is alimentary canal. Skin also acts as an endocrine gland, as it secretes vitamin D, which is also considered as a hormone. Calcium functions as a hormone to help absorb calcium from the GI tract.

In the next lesson, we will see about other glands and hormones and their functions. Okay. Come on.

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To go to the prior lesson about Human Endocrine System, please click the link below.