Final answer:
The key difference between exocrine and endocrine glands is their mode of secretion.
Step-by-step explanation:
The key difference between exocrine and endocrine glands lies in their mode of secretion. Exocrine glands secrete chemicals through ducts that lead outside the gland, while endocrine glands release hormones directly into the bloodstream. For example, sweat glands are classified as exocrine glands because they secrete sweat through ducts onto the surface of the skin, whereas the pancreas is classified as both an exocrine and endocrine gland because it releases digestive juices through ducts into the small intestine as well as hormones into the bloodstream.