Which of the following is NOT considered a solid organ?

In traditional Chinese medicine, solid organs are typically categorized as organs that have a dense structure and are involved in the production and storage of vital substances like blood, Qi, and bodily fluids. The gallbladder is classified as a hollow organ because it primarily functions as a storage vessel for bile, which is produced by the liver to aid in digestion. Hollow organs are generally distinguished from solid organs by their capability to contain fluids or gases.

The lung, spleen, and kidney are all solid organs, each serving critical functions in maintaining the body's balance of Qi, blood, and other essential substances. The lung is responsible for respiration and gas exchange, the spleen plays a key role in digestion and blood production, and the kidney is crucial for fluid regulation and detoxification.

Understanding these classifications is important for anyone studying acupuncture and the principles of traditional Chinese medicine, as they impact treatment strategies and the approach to diagnosing and addressing various health patterns.