A Level Biology Practice Exam

Histamines play a crucial role in the inflammatory response when tissues are damaged or injured. Their primary function is to cause blood vessels to dilate and increase their permeability. This dilation allows more blood to flow to the affected area, which brings vital immune cells and nutrients necessary for healing. The increased permeability also enables proteins, fluids, and other molecules to move out of the bloodstream and into the surrounding tissue, contributing to swelling and the overall inflammatory response.

Additionally, the release of histamines can lead to various symptoms associated with hypersensitivity reactions, such as allergies, where similar mechanisms occur. By understanding this function of histamines, one can appreciate their importance in both normal healing processes and pathological conditions.