All glands that secrete substances do so by exocytosis. Exocytosis is the process by which cells release substances from their interior to the exterior.

Here's a breakdown:

* Glands: Specialized cells or groups of cells that synthesize and secrete substances.

* Exocytosis: The process where a vesicle (a membrane-bound sac) inside the cell fuses with the cell membrane, releasing its contents outside the cell.

Types of Glands:

There are two main types of glands based on how they release their secretions:

* Exocrine glands: These glands secrete their products into ducts that carry them to a specific location. Examples include salivary glands, sweat glands, and mammary glands.

* Endocrine glands: These glands secrete their products (hormones) directly into the bloodstream. Examples include the thyroid gland, pituitary gland, and adrenal glands.

Regardless of the type of gland, exocytosis is the mechanism by which they release their secretions.