American Society for Clinical Pathology (ASCP) Histotechnologist Practice Test

Which cells in connective tissue contain abundant secretory granules including histamine and heparin?

1. Fibroblasts

2. Mast cells

3. Macrophages

4. Neutrophils

The correct answer is: Mast cells

Mast cells are the connective tissue cells that contain abundant secretory granules filled with substances such as histamine and heparin. These cells play crucial roles in the immune response and in inflammatory reactions. Histamine is a key mediator in allergic responses and is involved in the dilation of blood vessels, increasing blood flow and permeability during inflammation. Heparin, on the other hand, acts as an anticoagulant, helping to prevent blood clotting in the immediate area of injury and facilitating the migration of other immune cells to the site of inflammation. Mast cells are often found in close proximity to blood vessels and are distributed widely throughout various tissues in the body, especially in the skin, respiratory tract, and digestive system. Their granules are released when mast cells degranulate, which can occur in response to allergens or injury, leading to the characteristic symptoms of allergic reactions. This distinct specialization sets mast cells apart from other connective tissue cells, which do not contain the same types of secretory granules or play similar roles in immediate immune responses. For example, fibroblasts are primarily involved in producing the extracellular matrix and collagen, macrophages are key players in phagocytosis and immune response, and neutrophils are critical for combating infection