Cellular Adaptation - hyperplasia, hypertrophy, atrophy and metaplasia + cell injury

Summary

This script discusses cellular adaptation, detailing four types: hyperplasia (increase in cell number), hypertrophy (enlargement of cells), atrophy (decrease in cell size), and metaplasia (epithelial type change). It distinguishes between physiologic and pathologic stimuli, explaining how cells can adapt to normal stresses but may fail if the stimulus is abnormal or prolonged. It also touches on the consequences of cellular injury, including reversible and irreversible damage, and the potential progression to cell death via necrosis or apoptosis.

Takeaways

• 🌿 Cellular adaptation is the ability of cells to respond to stimuli and environmental changes.
• 🔬 The four basic types of cellular adaptation are hyperplasia, hypertrophy, atrophy, and metaplasia.
• 🤰 Physiologic stimuli include normal stresses like pregnancy and exercise, leading to adaptive changes in cells.
• 🚨 Pathologic stimuli are abnormal, such as hormonal imbalances causing hyperplasia or hypertrophy.
• 📈 Hyperplasia is an increase in the number of cells, which can be due to normal growth or abnormal stressors.
• 💪 Hypertrophy is an increase in cell size, occurring in response to both normal and abnormal stressors.
• 📉 Atrophy is a decrease in cell size due to a loss of normal stimulus, which can be either physiologic or pathologic.
• 🔄 Metaplasia is a change in cell type to adapt to new environmental conditions, often pathologic.
• ⚠️ If cells cannot adapt to stimuli, they can become injured, leading to cell death through necrosis or apoptosis.
• 🔍 Cellular injury can be reversible if the stimulus is removed, allowing cells to return to normal function.

Q & A

What is cellular adaptation?

Cellular adaptation is the ability of cells to respond to various types of stimuli and adverse environmental changes.

What are the four basic types of cellular adaptation?

The four basic types of cellular adaptation are hyperplasia, hypertrophy, atrophy, and metaplasia.

What is hyperplasia and how does it occur?

Hyperplasia is an increase in the number of cells. It can occur due to physiologic or pathologic stimuli, such as an increase in breast size during pregnancy or adrenal gland growth due to pituitary adenoma.

Which cells are capable of undergoing hyperplasia?

Cells capable of undergoing hyperplasia include the epidermis, intestinal cells, liver cells, bone marrow cells, and fibroblasts.

What is hypertrophy and how does it differ from hyperplasia?

Hypertrophy is an increase in the size of a cell. Unlike hyperplasia, hypertrophy involves an increase in cell size rather than cell number. It can occur due to physiologic stimuli like exercise or pathologic stimuli such as aortic stenosis.

What is atrophy and what causes it?

Atrophy is the decrease in the size of a cell that was once normal-sized. It can be caused by physiologic stimuli, like the uterus shrinking after pregnancy, or pathologic stimuli such as disuse or aging.

What is metaplasia and how does it occur?

Metaplasia is the change of one type of epithelium to another type in response to a new environment or stimulus. It often occurs pathologically, such as in Barrett's esophagus due to reflux of gastric contents.

Can metaplasia be reversed?

Most forms of metaplasia are reversible if the stimulus is removed, but some, like Barrett's esophagus, tend to be permanent once established.

What happens if cells cannot adapt to their new environment?

If cells cannot adapt to their new environment, they become injured, which can lead to cell death through necrosis or apoptosis if not reversed.

What is the difference between reversible and irreversible cellular injury?

Reversible cellular injury can be reversed if the stimulus is removed, allowing the cell to return to normal function. Irreversible cellular injury leads to cell death through necrosis.

What is dysplasia and how is it related to metaplasia?

Dysplasia is not a true cellular adaptive response but a condition where cells divide and become abnormal in structure and function. It may progress to become cancerous. Metaplasia can progress to dysplasia if the stimulus persists.