What is the difference between endocrine and exocrine glands? Provide an example for each.

• A. Endocrine glands secrete hormones into the bloodstream (e.g., pituitary); Exocrine glands secrete into ducts onto surfaces (e.g., salivary glands, sweat glands).
• B. Exocrine glands secrete hormones into the bloodstream (e.g., pituitary); Endocrine glands secrete into ducts onto surfaces (e.g., salivary glands, sweat glands).
• C. Endocrine glands secrete enzymes into ducts; Exocrine glands secrete hormones into the bloodstream.
• D. Endocrine glands are ductless; Exocrine glands are ductless.

Answer: (A)

Glands are distinguished by how they release their products. Endocrine glands release hormones directly into the bloodstream without using ducts, so their chemical messages travel through blood to distant targets and can have widespread effects. A classic example is the pituitary gland, which sends hormones into the blood to regulate growth, metabolism, and other endocrine organs.

Exocrine glands, in contrast, secrete onto surfaces or into hollow organs through ducts. Their secretions reach a surface or lumen rather than the bloodstream. Salivary glands pour saliva into the mouth via ducts, and sweat glands release sweat onto the skin through ducts.

A helpful note: some organs contain both kinds of secretory tissue, like the pancreas, which has endocrine Islets that release hormones into the blood and exocrine acinar tissue that secretes digestive enzymes into the digestive tract.