Every cell has a life span
Cells die when no longer needed and new cells replace them.
A cell’s whole life
Your skin cells do their job, then die and are replaced. This happens all the time.
What happens to a cell that is no longer needed in the body?
What this lesson covers
The idea
Cells grow and divide in a controlled way, carry out their functions and die when no longer needed, being replaced by new cells; problems arise if cells die too early or fail to die when they should.
A cell’s whole life
Your skin cells do their job, then die and are replaced. This happens all the time.
What happens to a cell that is no longer needed in the body?
- It dies, and a new cell replaces it
- It lives forever
- It grows bigger and bigger
Watch a tissue over time
Run time forward for each case: normal, cells that die too early, cells that fail to die.
Cells do not live forever
Cells grow and divide in a controlled way, stay in the right place, carry out their functions, and die when they are no longer needed. Dead cells are replaced by new cells that carry out the same function. So every cell has a definite life span. If cells do not die when they should, or if they die too early, problems can arise in the body.
Every day, hundreds of billions of cells in the human body are replaced: almost 1 per cent of all cells.
- Case | What happens to the tissue
- Normal | old cells die, new cells replace them
- Cells die too early | cells are lost: gaps
- Cells fail to die | extra cells build up
Notes
Every cell has a definite life span. Cells grow and divide in a controlled way, do their job, and die when no longer needed; new cells replace them. Cells that die too early or fail to die cause problems.
Check yourself
Why is a dead cell in the body replaced?
Which can cause problems in the body?
Cells grow and divide…
- A new cell carries out the same function — correct. Yes.
- So that the body gets smaller. The body needs the function done.
- It never is replaced. Dead cells are replaced by new cells.
- Cells that die too early or fail to die when they should — correct. Yes.
- Cells that die when they are no longer needed. That is normal: each cell has a life span.
- Cells that carry out their function. That is normal.
- in a controlled way — correct. Yes.
- without any control. Control is needed to avoid problems.
- only once. Cells divide to replace those that die.