Chylomicrons enter the bloodstream and travel via the thoracic duct to which tissues first?

• A. Bone, heart, adipose tissue, and then liver
• B. Brain, muscles, and kidneys
• C. Lungs
• D. Liver first

Answer: (B)

When chylomicrons reach the bloodstream, they’re destined for tissues that have high lipoprotein lipase activity to unload their triglycerides. The first major destinations are skeletal muscle and adipose tissue, where LPL breaks down the triglycerides into fatty acids that these tissues can take up for energy or storage. After most triglycerides are removed, the remaining chylomicron particle becomes a chylomicron remnant and is cleared by the liver. The brain is largely protected by the blood–brain barrier, and kidneys aren’t the primary first recipients of chylomicron lipids.

Among the provided options, the tissues that are most consistent with the initial delivery of dietary triglycerides are the muscles (with adipose tissue also a primary site). This is why the choice including muscles is the best fit.