Question

Place the following in order of their replacement times, from shortest to longest.

A. epidermal cell
B. nerve cell
C. bone matrix
D. red blood cell
E. cell lining the gut

Answer 1

The cells with the shortest replacement time are the cells lining the gut, followed by red blood cells, epidermal cells, bone matrix, and finally nerve cells, which have the longest replacement time or do not replenish at all.

Step-by-step explanation:

To place the following in order of their replacement times, from shortest to longest: epidermal cell, nerve cell, bone matrix, red blood cell, and cell lining the gut, a general understanding of cell turnover in human tissues is required.

The cells lining the gut have one of the fastest turnover rates as they are constantly exposed to food, acidity, and pathogens, which necessitates regular replenishment, typically every few days. Red blood cells, while not as rapid, also have a definable lifespan and are typically replaced after about 120 days. The epidermal cells, forming the protective outer layer of the skin, are shed and replenished regularly, typically within weeks. Bone remodeling is a slower process as bone matrix is broken down and rebuilt over months to years. Finally, nerve cells are among the slowest to be replaced, if at all, especially in the central nervous system, where many neurons persist for the lifetime of the individual.

The correct order from shortest to longest replacement time would therefore be:

1. Cell lining the gut (few days)
2. Red blood cell (around 120 days)
3. Epidermal cell (weeks to a month)
4. Bone matrix (months to years)
5. Nerve cell (years to not at all)