When do hypertrophy and hyperplasia occur?
1 Answer
Tissues/organs undergo hypertrophy/hyperplasia as a response to a disruption in homeostasis.
Explanation:
The key to understanding why hypertrophy/hyperplasia occur is knowing that tissues and organs always have the "goal" to be in homeostasis, which is a state of equilibrium maintained by physiological processes. In other words, the cell is not under any sort of stress.
When an organ/tissue is placed under stress it is no longer in homeostasis. The stress can be either pathological (infection, diminished blood flow, etc.) or physiological (such as when the uterus of a female has to prepare for menstruation). Because the organ desires to get back to homeostasis, it has to work harder (or compensate) to overcome this new stressful environment.
Hypertrophy/hyperplasia are two common mechanisms to help the organ re-achieve homeostasis. Increased size or cell number lessens the burden of individual cells in the tissue, which makes it easier for the organ to function overall.
Want an example? Look no further than people who lift weights frequently. The muscles are routinely placed under the stress of heavy lifting, and so over time, the muscles will hypertrophy so that they will not have to overwork as much during the next weight-lifting session.
One important thing to note: hypertrophy and hyperplasia often occur at the same time , but there are three tissue types where it is physically impossible for hyperplasia to occur:
- Cardiac muscle
- Skeletal muscle
- Nerves
The reason that they cannot undergo hyperplasia is because they do not have reserve stem cells and so new cells cannot be made. In these three tissues, the only option is hypertrophy.
Hope this helps!
~AP
