Question

what are the THREE types of gland in humans ? give one example for each

Answer 1

Endocrine glands

Main article: Endocrine gland

Endocrine glands secrete substances that circulate through the blood stream. The glands secrete their products through basal lamina into the blood stream. Basil lamina typically can be seen as a layer around the glands to which a million, maybe more, tiny blood vessels are attached. These glands often secrete hormones which play an important role in maintaining homeostasis. The pineal gland, thymus gland, pituitary gland, thyroid gland, and the two adrenal glands are all endocrine glands.

Exocrine glands

Main article: Exocrine gland

Exocrine glands secrete their products through a duct onto an outer or inner surface of the body, such as the skin or the gastrointestinal tract. Secretion is directly onto the apical surface. The glands in this group can be divided into three groups:

   Apocrine glands - a portion of the secreting cell's body is lost during secretion. 'Apocrine glands' is often used to refer to the apocrine sweat glands, however it is thought that apocrine sweat glands may not be true apocrine glands as they may not use the apocrine method of secretion, e.g. mammary gland, sweat gland of arm pit, pubic region, skin around anus, lips and nipples.

   Holocrine glands - the entire cell disintegrates to secrete its substances, e.g. sebaceous glands: meibomian and zeis glands.

   Merocrine glands - cells secrete their substances by exocytosis, e.g. mucous and serous glands; also called "eccrine", e.g. max sweat gland of humans, goblet cells, salivary gland, tear gland and intestinal glands.

The type of secretory product of exocrine glands may also be one of three categories:

   Serous glands secrete a watery, often protein-rich, fluid-like product, e.g. sweat glands.

   Mucous glands secrete a viscous product, rich in carbohydrates (such as glycoproteins), e.g. goblet cells.

   Sebaceous glands secrete a lipid product. These glands are also known as oil glands, e.g. Fordyce spots and meibomian glands.

Clinical significance

Answer 2

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