Category Archives: Blood

Neutrophils TEM

Granulocytes are a category of white blood cells characterized by the presence of granules in their cytoplasm.  They are also called polymorphonuclear leukocytes (PMN or PML) because of the varying shapes of the nucleus, which is usually lobed into three segments. In common parlance, the term polymorphonuclear leukocyte often refers specifically to neutrophil granulocytes, the most abundant of the granulocytes. Granulocytes or PMN are released from the bone marrow by the regulatory complement proteins. (from wikipedia)

Image by Rob Young.  From Wellcome images (link)

Fungal elements engulfed by neutrophils- col
Colour enhaced transmission electron micrograph
showing fungal bodies (blue) being engulfed by
polymorphonuclear leucocytes (yellow) deep in the
corneal stroma. The fungal hyphae within the cells
are approximately 1.1nm in diameter.

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Adult humans have roughly 2–3 × 1013 (20-30 trillion) red blood cells at any given time, comprising approximately one quarter of the total human body cell number (women have about 4 to 5 million erythrocytes per microliter (cubic millimeter) of blood and men about 5 to 6 million; people living at high altitudes with low oxygen tension will have more). Red blood cells are thus much more common than the other blood particles: there are about 4,000–11,000 white blood cells and about 150,000–400,000 platelets in each microliter of human blood.

Human red blood cells take on average 20 seconds to complete one cycle of circulation.  (From Wikipedia)

Image form Wellcome Images  Creative Commons. Image credit Annie Cavanagh (link)

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Erythrocytes in capillary TEM

Capillaries are so small that red blood cells can only travel through them in single file. Capillaries measure in size from about 5-10 microns in diameter. Capillary walls are thin and are composed of endothelium (a type of simple squamous epithelial tissue). Oxygen, carbon dioxide, nutrients and wastes are exchanged through the thin walls of the capillaries. (from

Image from (link).   Image by David Phillips

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Leukocytes anchors

Like a fast-flowing river, the bloodstream carries white blood cells – the first responders of our immune system, also called leucocytes – to areas of infection in the body. This high-speed journey is fraught with danger. To prevent the currents from washing the leucocytes away once they arrive, they do what any salty sea dog would – drop their anchors. The leucocytes pictured here were scattered over a man-made surface similar to the lining of a blood vessel and then blasted with fast-flowing liquid to simulate the bloodstream. Prickly anchors developed immediately to tether the base of the cell to the vessel-like floor. Only after a dramatic voyage inside our blood vessels can the job of the leucocytes really begin, penetrating through the vessel lining on a mission to tackle a nearby infection. (adapted from  John Ankers’ “Brave Blood”)

 Image found at (link)

Jacob Rullo & Myron Cybulsky
University of Toronto, Canada

Images available under a BY-NC-SA License
Published in Journal of Cell Biology 197(1):115-129

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