Hyperplasia and hypertrophy

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Hyperplasia and hypertrophy

Introduction to pathology

Cellular injury

Free radicals and cellular injury

Necrosis and apoptosis

Ischemia

Hypoxia

Amyloidosis

Inflammation

Inflammation

Wound healing

Neoplasia

Atrophy, aplasia, and hypoplasia

Hyperplasia and hypertrophy

Metaplasia and dysplasia

Oncogenes and tumor suppressor genes

Assessments

Hyperplasia and hypertrophy

USMLE® Step 1 questions

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High Yield Notes

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Questions

USMLE® Step 1 style questions USMLE

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A 39-year-old woman comes to the clinic with weight gain, facial swelling, and muscle weakness. Physical examination shows marked central obesity with thinning of the extremities and abundant purple striae covering the abdomen. Serum laboratory studies show glucose is 205 mg/dL, cortisol is 80 ug/dL, and an elevated ACTH. ACTH levels are decreased after the administration of a high dose of dexamethasone. Head CT scan reveals an adenoma in the pituitary gland and the patient was diagnosed with ACTH-producing pituitary adenoma. The elevated levels of ACTH will cause which of the following changes in the adrenal glands?  

External References

First Aid

2022

2021

2020

2019

2018

2017

2016

Cardiomyopathy (hypertrophic)

Hypertrophic osteoarthropathy p. 709

cancer association p. 221

Hypertrophic scars p. 213

Osteoarthropathy, hypertrophic

cancer association p. 221

Transcript

Contributors

Anuj Paul

Gil McIntire

Tanner Marshall, MS

Pauline Rowsome, BSc (Hons)

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!

Our body is the same; when the demand placed on an organ or tissue is more than it can handle, its called “stress,” and the body can adapt through either hyperplasia or hypertrophy.

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.

An example of pathologic hypertrophy is when the heart undergoes hypertrophy to deal with high blood pressure or hypertension.

In hypertension, the heart has to pump blood against a high resistance and cardiac myocytes once again adapt by increasing the synthesis of myofilaments causing individual cells to get bigger.

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.

Compensatory hyperplasia occurs in organs that regenerate, like the skin, lining of the intestines, the liver, and bone marrow.

Summary

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.

Sources

  1. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  2. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  3. "Yen & Jaffe's Reproductive Endocrinology" Saunders W.B. (2018)
  4. "Bates' Guide to Physical Examination and History Taking" LWW (2016)
  5. "Robbins Basic Pathology" Elsevier (2017)
  6. "Analysis of arterial intimal hyperplasia: review and hypothesis" Theoretical Biology and Medical Modelling (2007)
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