GROWTH ADAPTIONS Flashcards
What happens when an organ is in homeostasis?
It remains stable under the physiologic stress placed on it.
What can cause growth adaptations in an organ?
An increase, decrease, or change in stress on the organ.
What happens when stress on an organ increases?
The organ increases in size via hypertrophy (increase in cell size) and/or hyperplasia (increase in cell number).
How does hypertrophy occur at a cellular level?
Through gene activation, protein synthesis, and organelle production.
How does hyperplasia occur?
By producing new cells from stem cells.
Do hypertrophy and hyperplasia occur together?
Yes, generally they do (e.g., uterus during pregnancy), but some tissues, like cardiac and skeletal muscle, can only undergo hypertrophy.
What happens to cardiac myocytes in response to hypertension?
They undergo hypertrophy, not hyperplasia.
Can hyperplasia lead to cancer?
Yes, pathologic hyperplasia (e.g., endometrial hyperplasia) can progress to dysplasia and cancer, but benign prostatic hyperplasia (BPH) does not increase cancer risk.
What causes atrophy?
Decreased stress due to factors like reduced hormonal stimulation, disuse, or lack of nutrients/blood supply.
How does atrophy occur?
Through a decrease in cell number (via apoptosis) and cell size (via ubiquitin-proteosome degradation and autophagy).
What is ubiquitin-proteosome degradation?
A process where intermediate filaments are tagged with ubiquitin and destroyed by proteosomes.
What is metaplasia?
A change in cell type due to altered stress, usually involving a switch in surface epithelium.
What is a classic example of metaplasia?
Barrett esophagus, where squamous epithelium in the esophagus changes to mucin-producing columnar cells due to acid reflux.
How does metaplasia occur at the cellular level?
Through the reprogramming of stem cells to produce a new cell type.
Can metaplasia be reversed?
Yes, if the driving stressor is removed (e.g., treating acid reflux can reverse Barrett esophagus).
Can metaplasia lead to cancer?
Yes, persistent stress can cause metaplasia to progress to dysplasia and eventually cancer. However, apocrine metaplasia of the breast does not increase cancer risk.
How does vitamin A deficiency cause metaplasia?
It impairs differentiation of specialized epithelial cells, leading to keratomalacia, where conjunctival cells turn into keratinizing squamous epithelium.
Can connective tissue undergo metaplasia?
Yes, an example is myositis ossificans, where muscle connective tissue transforms into bone after trauma.
What is dysplasia?
Disordered cellular growth, often referring to precancerous cell proliferation.
What are some examples of dysplasia?
Cervical intraepithelial neoplasia (CIN), which is a precursor to cervical cancer.
What conditions can lead to dysplasia?
Longstanding pathologic hyperplasia (e.g., endometrial hyperplasia) or metaplasia (e.g., Barrett esophagus).
Can dysplasia be reversed?
Yes, if the inciting stressor is removed, but persistent stress can lead to carcinoma (which is irreversible).
What is aplasia?
The failure of cell production during embryogenesis (e.g., unilateral renal agenesis).
What is hypoplasia?
A decrease in cell production during embryogenesis, leading to a smaller organ (e.g., streak ovary in Turner syndrome).
