What is the term for red blood cells shrinking in a hypertonic solution?

The term used to describe red blood cells shrinking in a hypertonic solution is crenation. When red blood cells are placed in a hypertonic environment, the concentration of solutes outside the cell is higher than that inside the cell. As a result, water moves out of the red blood cells to balance the solute concentrations. This loss of water causes the cells to shrink and take on a wrinkled appearance, a process known as crenation.

Understanding the context around this is helpful. For example, plasmolysis typically refers to the shrinking of plant cells in a hypertonic solution, while hemolysis refers to the bursting of red blood cells in a hypotonic solution, where water enters the cells due to lower external solute concentration. Plasmoptysis is not a commonly used term in this context and generally does not apply to red blood cells. Thus, crenation is the correct term that accurately describes the behavior of red blood cells in a hypertonic solution.