Biological Systems MCAT Practice Exam

What distinguishes exocrine glands from endocrine glands?

1. Exocrine glands produce hormones only

2. Exocrine glands have ducts for secretion

3. Exocrine glands are located in the brain

4. Exocrine glands do not release their products into the bloodstream

The correct answer is: Exocrine glands have ducts for secretion

Exocrine glands are distinguished from endocrine glands primarily by their secretion mechanisms. Exocrine glands have ducts that transport their secretions to specific sites, which allows them to release substances directly onto epithelial surfaces or into body cavities. This process is essential for functions such as lubrication, digestion, and protection. Common examples of exocrine glands include salivary glands that secrete saliva into the mouth, and sweat glands that release sweat to the skin surface. In contrast, endocrine glands release their products, mainly hormones, directly into the bloodstream. This allows hormones to be transported throughout the body to affect various physiological processes. The presence of ducts in exocrine glands is a key characteristic that clearly sets them apart from endocrine glands, which function without ducts. The other options do not accurately capture this distinction. For example, stating that exocrine glands produce hormones only is misleading, as they can produce a variety of substances, including enzymes and mucus. The idea that exocrine glands are located in the brain is not accurate, since many exocrine glands are found in various tissues throughout the body. Lastly, while it's true that exocrine glands do not release their products into the bloodstream, this statement does not fully highlight the role of ducts in