In the January Issue of SciAm (discussing Haemophilia):

When damage occurs to blood vessels, exposure of the blood to collagen in the cell walls and material released by the cells triggers the activation of clotting factors.

I read the original in print, but it is available online here.

This seems to imply that animal cells (in this example, those of humans) have cell walls. I sometimes see similar implications in other resources. However, in elementary biology, one is taught that animal cells never have cell walls.

Therefore, my question: Are references to animal cell cell walls (such as the above, for human animal cells) simple mistakes--or are they exceptions to a generalization?

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    $\begingroup$ This was just a badly worded statement; the better wording should have been: "exposure of the blood to collagen in the blood vessel walls and material released by the cells...". They clearly mean damaged endothelium. $\endgroup$ – anongoodnurse Dec 31 '14 at 2:47
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    $\begingroup$ Can you also post a link to this article. If they have used this erroneous terminology then we should write to the editor. $\endgroup$ – WYSIWYG Dec 31 '14 at 6:35
  • $\begingroup$ @WYSIWYG see edit. When I read the quote, I immediately suspected an error. I do permit SciAm and the author the occasional typo, though, since they're obviously high-quality otherwise. $\endgroup$ – imallett Dec 31 '14 at 11:03
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    $\begingroup$ @imallett It is for everyone's good to report mistakes. I once found ~100 articles that had mistakenly called TCA-Cycle as Trichloroacetic acid cycle instead of tricarboxylic acid cycle. I mailed the editors. $\endgroup$ – WYSIWYG Dec 31 '14 at 11:11

Humans, as well as the rest of the metazoans (i.e. animals), absolutely do not have cell walls. What humans do have is extracellular matrix (ECM), which is the sort of fibrous, sort of gel-like material in which cells in many of the tissues are embedded. Collagen is a major component of ECM.

From the old copy of Alberts that is hosted on the NCBI website:

Tissues are not made up solely of cells. A substantial part of their volume is extracellular space, which is largely filled by an intricate network of macromolecules constituting the extracellular matrix (Figure 19-33). This matrix is composed of a variety of proteins and polysaccharides that are secreted locally and assembled into an organized meshwork in close association with the surface of the cell that produced them...

Two main classes of extracellular macromolecules make up the matrix: (1) polysaccharide chains of the class called glycosaminoglycans (GAGs), which are usually found covalently linked to protein in the form of proteoglycans, and (2) fibrous proteins, including collagen, elastin, fibronectin, and laminin, which have both structural and adhesive functions.

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    $\begingroup$ @anongoodnurse yeah, I figured it was something like that too. I just wanted to make super clear to the OP that, at least in terms of nomenclature, animals definitely do not have cell walls. $\endgroup$ – tel Dec 31 '14 at 3:11
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    $\begingroup$ @anongoodnurse which got me thinking about whether cell wall vs ECM is a difference without a distinction, but I cut that part out of my answer as it didn't really add anything to it. I might put that up myself as a separate question once I've looked into it a bit. $\endgroup$ – tel Dec 31 '14 at 3:13

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