Question

Define the following.
(a) Exocrine gland
(b) Endocrine gland
(c) Hormone

Answer 1

Hint: The given terms refer to the chemical messenger system in the body. The glands are responsible for producing and secreting molecules that regulate and control important physiological processes of the body.

Complete answer:
(a) Exocrine gland: Exocrine glands are glands that deposit secretions into ducts. These ducts may open outside the body to release secretions such as sweat from sweat glands and milk from mammary glands, or maybe released onto another surface within the body such as digestive juices into the gastrointestinal tract.
(b) Endocrine gland: Glands that do not discharge secretions through ducts and directly deposit them in the blood are endocrine glands. Endocrine glands secrete hormones.
(c) Hormones: These are chemical messengers, molecules that are transported by the circulatory system to target organs to regulate physiological and behavioral processes. They are intercellular messengers and are produced in trace amounts.

Additional information:
- Hormones have diverse molecular structures and are classified as eicosanoids, steroids, or protein/amino acid derivatives.
- Apart from the endocrine glands that are specifically for producing hormones, the gastrointestinal tract, liver, kidney, and heart also produce hormones.
- The hypothalamus is the neural control center for the endocrine system.
- Exocrine glands are classified into three types based on how the product is secreted from the cells: merocrine glands that secrete substances by exocytosis, apocrine glands where a portion of the cell membrane buds off during secretion, and holocrine glands where the entire cell disintegrates to excrete its substance.

Note:
- Pancreas and liver are composite glands that act as both an exocrine and endocrine gland.
- Hormones are non-nutrient chemicals, molecules that are essential for the body but do not have nutritional value.