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Introduction to pathology
Hyperplasia and hypertrophy
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cancer association p. 221
cancer association p. 221
Imagine a lumberjack. At first she can handle cutting down a few trees a day, but suddenly her boss wants her to chop down an entire forest by the end of the week! Now she’s stressed out from the increased demand!
Hyperplasia refers to the process where cells in an organ or tissue increase in number, so its like hiring a bigger pack of lumberjacks.
Hypertrophy is when these cells in an organ or tissue increase in size, like if the lumberjack gets really tough so that she can cut down twice as many trees.
So hyperplasia, bigger pack, and hypertrophy, tough lumberjack!
So, a tissue or organ might get stressed by physiological processes or from disease processes.
An example of physiologic hypertrophy is lifting a 10 pound sack of potatoes which puts a bigger functional demand on your skeletal muscles.
In response, the muscle cells produce more proteins or myofilaments and get larger in size, allowing the biceps as a whole to generate more force. As a result your muscles also become bigger and tougher.
In both cases there’s hypertrophy, but the triggers are quite different.
Now, in hyperplasia there’s an increase in the number of cells - a larger pack.
And that can only happen in organs with stem cells that can undergo cellular differentiation to become a mature cell in that organ, like cells in the intestines for example.
So hyperplasia doesn’t occur in relatively permanent tissues without stem cells- like cardiac, nerve, and adult skeletal muscle tissue.
And that’s why those tissues typically only undergo hypertrophy when they face increased stress.
Now there’s compensatory hyperplasia and hormonal hyperplasia.
Hyperplasia and hypertrophy are two ways that the size of cells can increase. Hyperplasia is an increase in the number of cells, while hypertrophy is an increase in the size of cells. During hypertrophy, the cells enlarge as they fill with more cytoplasm. This can lead to an increase in the strength or function of the tissue. During hyperplasia, new cells are formed as existing cells divide. This can lead to an increase in the number of cells and the overall size of the tissue.
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