Answer:
Glands made up of parenchyma of glandular epithelium that forms the secretory portions of the glands.
Glandular epithelium is a modified form of columnar epithelium. Their cells are modified to secrete certain substances. It lines the stomach, intestine and other secretory organs.
The glands occur singularly as unicellular glands. Unicellular glands are the goblet cells in the mucous membrane of the alimentary canal.
It may occur congregate to form multicellular glands which includes sweat glands and sebaceous glands in the skin, mammary glands and salivary glands, etc.
Glandular epithelium secretes sweat, milk, digestive enzymes, oil and other hormones.
There are two types of glands: exocrine and endocrine glands. Exocrine glands can be unicellular or multicellular. They have ducts and secretion is delivered into these ducts and end up on the epithelial surface. For example: sweat glands.
Endocrine glands are without ducts and secretions are released directly to the bloodstream. Example: pineal gland, pituitary gland.
Note:
Glandular epithelium are the specialised epithelial cells that secrete glands. They are of two types: endocrine and exocrine glands. Exocrine glands hold secretion for covering and lining of the body until secretion is needed. Endocrine glands control hormone production and enclose the formed hormones until they are needed in the body.
