The paper I linked above (“The distribution of cellular turnover in the human body,” lmk if you want me to send it to you) states that turnover is about 330 billion cells per day. It also states that erythrocytes account for 65% of that turnover, gastrointestinal epithelial cells account for 12% of turnover, while skin cells accounts for 1.1%. For skin cells, that would be 3.6 billion cells/day; for erythrocytes, 200 billion. That seems totally impossible given what I know about the turnover rate and absolute number of erythrocytes in the human body.
Another paper states that epidermal desquamation is about 500 million cells/day (Fig 1).
So yeah, both the proportions and the absolute number of cells being shed seem wildly divergent. The paper estimating cell turnover rates is in Nature Medicine. I’ll look closer at it and see if I can figure out the disconnect.
Oh shoot, I made a math mistake (wrong units). There’s actually almost 3 trillion erythrocytes in the human body, which is closer to 8% of the human body (~37.2 trillion cells). Their estimate of epidermal cell number and turnover is more than two orders of magnitude lower.
That still means that erythrocytes are heavily overrepresented in terms of cell turnover (of which they compose 65%), but not by as much as I’d originally thought.
The paper I linked above (“The distribution of cellular turnover in the human body,” lmk if you want me to send it to you) states that turnover is about 330 billion cells per day. It also states that erythrocytes account for 65% of that turnover, gastrointestinal epithelial cells account for 12% of turnover, while skin cells accounts for 1.1%. For skin cells, that would be 3.6 billion cells/day; for erythrocytes, 200 billion. That seems totally impossible given what I know about the turnover rate and absolute number of erythrocytes in the human body.
Another paper states that epidermal desquamation is about 500 million cells/day (Fig 1).
So yeah, both the proportions and the absolute number of cells being shed seem wildly divergent. The paper estimating cell turnover rates is in Nature Medicine. I’ll look closer at it and see if I can figure out the disconnect.
Oh shoot, I made a math mistake (wrong units). There’s actually almost 3 trillion erythrocytes in the human body, which is closer to 8% of the human body (~37.2 trillion cells). Their estimate of epidermal cell number and turnover is more than two orders of magnitude lower.
That still means that erythrocytes are heavily overrepresented in terms of cell turnover (of which they compose 65%), but not by as much as I’d originally thought.
Aha! This makes more sense now. Thanks for chasing that down, I feel much less confused.