Which of the following occurs after tissues are injured?
Select one:
A. Local blood vessels begin to dilate
B. Red blood cells separate from plasma
C. Red blood cells become less sticky
D. Platelets collect at the injury site
The Correct Answer and Explanation is:
The correct answer is A. Local blood vessels begin to dilate.
When tissues are injured, a series of physiological responses occur as part of the body’s inflammatory process. One of the first reactions is the dilation of local blood vessels, a process known as vasodilation. This response is critical because it increases blood flow to the affected area, which is essential for the delivery of immune cells, nutrients, and oxygen necessary for tissue repair.
During the inflammatory response, injured tissues release signaling molecules called inflammatory mediators, including histamine and prostaglandins. These substances cause the smooth muscle in the walls of blood vessels to relax, leading to vasodilation. As a result, more blood enters the capillaries in the injured area, which contributes to the classic signs of inflammation: redness and heat.
Increased blood flow allows for a greater supply of immune cells, such as neutrophils and macrophages, to migrate to the site of injury. These cells play a crucial role in defending against infection, clearing debris, and promoting healing. Additionally, the enhanced permeability of dilated blood vessels allows plasma and proteins, including clotting factors and antibodies, to leak into the tissue. This process helps form a protective barrier and provides the necessary components for tissue repair.
While option D, “Platelets collect at the injury site,” is also a correct response to injury, it occurs after the initial vasodilation and increased permeability have already begun. Therefore, option A is the most immediate response after tissue injury.
In summary, the dilation of blood vessels is a fundamental step in the inflammatory process that facilitates the body’s healing mechanisms by increasing blood flow and enabling immune response mobilization.