Mast cells contain

The correct answer is heparin and histamine.

Step-by-Step Explanation:

1. Understanding Mast Cells: Mast cells are a type of granulocyte (a category of white blood cells) derived from the myeloid stem cell line. They are part of the immune and neuroimmune systems and are found in rich numbers in connective tissues, particularly beneath the skin, near blood vessels and lymphatic vessels, and in the respiratory and digestive tracts.
2. Functions of Substances Contained in Mast Cells:
- Histamine: Mast cells are packed with granules containing histamine. When activated during an allergic reaction or in response to injury, they release histamine, which causes vasodilation (widening of blood vessels) and increases vascular permeability, leading to inflammation and recruiting other immune cells to the site.
- Heparin: This is a powerful anticoagulant (blood thinner) that prevents blood clotting, ensuring smooth blood flow in the inflamed area and helping immune cells migrate easily through tissues.
3. Analyzing the Options:
- heparin and calcitonin: Calcitonin is a hormone produced by the thyroid gland, not mast cells.
- heparin and histamine: This option correctly identifies the primary substances stored and released by mast cells.
- serotonin and melanin: Melanin is a pigment produced by melanocytes, not mast cells.
- vasopressin and relaxin: Vasopressin is an antidiuretic hormone produced by the hypothalamus/posterior pituitary, and relaxin is a hormone produced by the corpus luteum and placenta.