23- Exocrine glands: A. Discharge their secretion product directly into the bloodstream B. Are classified according to the shape of the cells that constitute them C. Can have a protective role D. Often have a merocrine mode of excretion E. Are always made up of secretory units and excretory units

The correct answers are:

C. Can have a protective role - This is true. Exocrine glands, such as sweat glands and salivary glands, can have a protective role. For example, sweat glands help regulate body temperature, and salivary glands produce saliva that aids in digestion and protects the mouth from bacteria.

D. Often have a merocrine mode of excretion - This is also true. Merocrine secretion is the most common type of exocrine secretion. The glands release their product by exocytosis and no part of the gland is lost or damaged.

The other options are incorrect:

A. Discharge their secretion product directly into the bloodstream - This is false. Exocrine glands release their secretions through ducts onto epithelial surfaces, not directly into the bloodstream. That's a characteristic of endocrine glands.

B. Are classified according to the shape of the cells that constitute them - This is false. Exocrine glands are usually classified based on their mode of secretion (merocrine, apocrine, holocrine), not the shape of their cells.

E. Are always made up of secretory units and excretory units - This is false. While many exocrine glands do have these components, not all do. Some, like sebaceous glands, are simple and unicellular.