These exocrine glands are enlarged and modified sweat glands and are the characteristic of mammals which gave the class its name. The basic components of the mammary gland are the alveoli (hollow cavities, a few millimetres large) lined with milk-secreting cuboidal cells and surrounded by myoepithelial cells.

Understanding Multicellular Glands
Multicellular glands are specialized structures in the body that produce and secrete substances like hormones, enzymes, and other fluids. The formation of these glands is closely associated with epithelial tissue.
Role of Epithelial Tissue
- Epithelial tissue is a type of tissue that lines the surfaces of organs and structures throughout the body.
- It is characterized by closely packed cells with minimal extracellular matrix, making it ideal for forming barriers and secretory structures.
Folding Mechanism
- Multicellular glands originate from the invagination (folding inward) of epithelial tissue.
- As the epithelial cells proliferate and fold, they create pockets that develop into glandular structures.
- These structures can either be exocrine (secreting substances onto surfaces or into cavities) or endocrine (secreting hormones into the bloodstream).
Examples of Multicellular Glands
- Exocrine glands: Sweat glands, salivary glands, and mammary glands.
- Endocrine glands: Thyroid gland, adrenal glands, and pituitary gland.
Conclusion
In summary, multicellular glands are formed by the folding of epithelial tissue, which allows for the creation of complex structures capable of producing and releasing various vital substances. Understanding this relationship between epithelial tissue and gland formation is essential in the study of human anatomy and physiology.