What term describes the movement of molecules into the bloodstream?

The term that describes the movement of molecules into the bloodstream is absorption. This process is crucial in various biological systems, primarily in digestion, where nutrients from food are absorbed through the intestinal walls and then transported into the circulatory system.

During absorption, small molecules such as glucose, amino acids, vitamins, and minerals pass through the intestinal lining into the bloodstream. This allows cells throughout the body to access the nutrients necessary for energy, growth, and repair.

In contrast, the other terms refer to different biological processes: excretion pertains to the removal of waste products from the body, secretion involves the production and release of substances (such as hormones or enzymes) by cells or glands, and digestion focuses on the breakdown of food into smaller components. Each of these processes plays a unique role in maintaining physiological balance, but absorption specifically relates to the integration of nutrients into the circulatory system for use by the body.