IMMUNOLOGY

Detailed explanation-1: -Injured tissue mast cells release histamine, causing the surrounding blood vessels to dilate and increase in permeability.

Detailed explanation-2: -During acute inflammatory responses, leukocyte-derived mediators such histamine and bradykinin will cause arteriolar dilation thereby increasing blood flow leading to rubor.

Detailed explanation-3: -(b) Histamine increases blood flow to the wound site, and increased vascular permeability allows fluid, proteins, phagocytes, and other immune cells to enter infected tissue. These events result in the swelling and reddening of the injured site, and the increased blood flow to the injured site causes it to feel warm.

Detailed explanation-4: -One of the best-known chemical mediators released from cells during inflammation is histamine, which triggers vasodilation and increases vascular permeability. Stored in granules of circulating basophils and mast cells, histamine is released immediately when these cells are injured.

Detailed explanation-5: -Histamine is released at the mucosal surfaces as a result of exposure to foreign particles. This histamine release causes the capillaries to become more permeable to white blood cells, which move into the capillaries and proceed to target and attack foreign bodies in the affected tissue.

Detailed explanation-6: -Histamines are responsible for dilating blood vessels and increasing their permeability in inflammation. Heparin inhibits blood clotting, and also promotes the movement of leukocytes into an area of infection.

Detailed explanation-7: -Histamine is released from cells in response to an antibody called immunoglobulin E (IgE). This antibody may be secreted in response to an invading pathogen such as a virus, bacteria, or an allergenic substance such as pollen. Histamine can also be released in response to injury caused by toxins.