Endocrine glands release chemical messengers known as hormones directly into the blood. Hormones are chemicals released by the endocrine glands that affect the physiological activity of the body.
The endocrine glands are the structures that are present in the various parts of the body and form the endocrine system. They produce and release hormones directly into the blood, and these hormones are transported in the blood to the target organs or organs of the body. Hormones have high levels of specificity, which means they only react with certain target sites (tissues or organs) in the body. These hormones help to control the physiological activities of the body, along with the nervous system.
The endocrine system draws its name from the ability of the glands to secrete hormones and substances into blood vessels. The exocrine system on the other hand, glands such as salivary and sweat glands secrete substances out of ducts. This can be further divided into two classifications. Hormones and glands can be classed as autocrine, in which they secrete chemicals to act in short distances and on themselves or paracrine in which they secrete hormones that work over short distances but on other organs.
Practice Questions
Khan Academy
MCAT Official Prep (AAMC)
Biology Question Pack, Vol 2. Passage 14 Question 94
Key Points
• The endocrine glands are the structures that produce and release chemical messengers known as hormones directly into the bloodstream.
• Hormones are chemical messenger molecules that help to regulate the physiological activities of the body along with the nervous system.
• Hormones move from the glands to the target organ or tissue via the blood.
Key Terms
gland: an organ that synthesizes a substance, such as hormones or breast milk, and releases it, often into the bloodstream or into cavities inside the body or on its outer surface
endocrine system: the collection of glands that produce hormones that regulate bodily processes
target organ: a specific organ on which a hormone, drug, or other substance acts
hormone: a chemical that is made by specialist cells, usually within an endocrine gland, and it is released into the bloodstream
