You'd die without these cells.

4 Feb 2023 · 2 min

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1:34

In this educational monologue, the speaker explains the historical origin of the term "granular cells" based on microscopic observations of white blood cells with visible granules. The discussion distinguishes granulocytes (cells with granules) from agranulocytes (without granules) and highlights mast cells as a specific type of granular immune cell. The core function of granules is described as storage depots for pre‑made chemical mediators that can be rapidly released when the cell is activated, typically by cytokine signaling. Upon appropriate immune stimulation, mast cells undergo degranulation, ejecting these stored chemicals. The released mediators serve multiple roles: they directly contribute to the immune response, attract additional immune cells, increase capillary permeability, and facilitate the movement of larger white blood cells into tissues, thereby promoting local inflammation and tissue access.

Chapters

Granular cells. Now they're called granular cells because a long time ago, when we were using light microscopes and staining things so that we could see them, we noticed that some, for example, white blood cells had no granules in them, little dots, and some had granules in them. So in the white blood cell world, we divide them into the granulocytes and the agranulocytes, or things without granules. Mast cells are a specific type of immune cell that falls into the granular So the purpose of the granules is that they are holding onto material that are within the cell. And then when that cell is triggered, normally by— we've talked about cytokines, which are chemical signaling agents in the body— a granular cell triggered in the right way will degranulate, meaning it will shoot out these chemicals that are inside these little granule storage areas. And On demand when you need it, it's already made and it just turns a switch and gets activated, so to speak. Under immune stimulation, we wind up having them degranulate, and then they release other chemicals that either help us with our direct immune response, maybe help to attract other immune cells to the area, maybe help with access to the tissues, such as opening up the capillaries, creating local inflammation, helping, uh, big white blood cells move in and out of the capillaries, you know, all manner of things that go on.