What leads to an increase in organ size? Right Ans - Increase in stress
What are the two processes via which an organ can increase in size? Right
Ans - Hyperplasia (increase in number of cells) and hypertrophy (increase in
size of cells)
What are three processes/events that occur in hypertrophy? Right Ans -
Gene activation, protein synthesis, production of organelles
Where do the new cells in hyperplasia come from? Right Ans - Stem cells
What tissues cannot undergo hyperplasia, only hypertrophy? Right Ans -
Permanent tissue, i.e. skeletal muscle, cardiac muscle, nerve tissue
What is the only type of muscle that can undergo hyperplasia? Right Ans -
Smooth muscle (i.e. uterus)
How do cardiac myocytes respond to hypertension? Right Ans -
Hypertrophy, not hyperplasia
Picture shows left ventricular hypertrophy
Hyperplasia that occurs due to underlying pathologic process Right Ans -
Pathologic hyperplasia
Pathologic hyperplasia pathway Right Ans - Hyperplasia --> dysplasia -->
cancer
What is one exception to the rule that pathologic hyperplasia can lead to
cancer? Right Ans - Benign prostatic hyperplasia does not increase the risk
for cancer
What leads to atrophy? Right Ans - Decrease in stress --> decrease in organ
size
What are the two processes that cause atrophy? Right Ans - A decrease in
the size of cells (via ubiquitin-proteosome degradation of the cytoskeleton
,and autophagy of cellular components) and a decrease in the number of cells
(via apoptosis)
Where are the three places stem cells are found? Right Ans - Bone marrow,
skin, base of intestinal crypts
What is Ubiquitin? Right Ans - Protein put on intermediate filaments of the
cytoskeleton to mark them for degradation in ubiquitin-proteosome
degradiation (decrease cell size)
What does a Proteasome do? Right Ans - Destroys ubiquitin-tagged
proteins, often intermediate filaments
What does ubiquitin tag in atrophy? (to reduce cell size) Right Ans -
Intermediate filaments
What destroys ubiquitin tagged proteins? Right Ans - Proteosomes
Autophagy Right Ans - Cell consumes its own components in vacuoles,
which fuse with lysozomes, whose hydrolytic enzymes breakdown the cellular
components in the vacuoles
What are the two processes in atrophy that can decrease cell size Right Ans
- Ubiquitin-proteosome degradation (to decrease cytoskeleton) and
autophagy (to decrease organelles)
What promotes metaplasia? Right Ans - A change in stress on a cell -->
change in cell type (metaplasia)
What is Epithelium? Right Ans - Cells that line body surfaces
What type of cells are most commonly involved in metaplasia? Right Ans -
Change of one type of surface epithelium to another (i.e. squamous, columnar,
urethelial/transitional)
Barrett's Esophagus Right Ans - Non-keratinized squamous epithelium of
the esophagus becomes non-ciliated, mucin producing columnar cells (normal
cell in stomach)
This is done to better handle the stress of acid reflux in the esophagus
, Is metaplasia reversible? Right Ans - Yes, in theory, with the removal of the
driving stressor
Ex/ treatment of GERD may reverse Barrett esophagus
How does metaplasia occur? Right Ans - Via reprogramming of stem cells,
which then produces a new cell type
Metaplasia to cancer pathway Right Ans - Metaplasia --> dysplasia -->
cancer
Barrett esophagus can progress to ___ if under persistent stress? Right Ans
- adenocarcinoma of esophagus
What type of metaplasia does not produce an increase in cancer risk? Right
Ans - Apocrine metaplasia of the breast, which is seen in fibrocystic change of
the breast
What vitamin deficiency can result in metaplasia? Right Ans - Vitamin A
deficiency
Why is Vitamin A necessary? Right Ans - It is necessary for the
differentiation of specialized epithelial surfaces such as the conjunctiva
covering the eye (causes night blindness!!); also necessary for maturation of
the immune system
What happens to the conjunctiva of the eye during Vitamin A deficiency?
Right Ans - Undergoes metaplasia from goblet cell/columnar epithelium to
keratinizing squamous epithelium (leading to dry eyes --> destruction of
cornea --> blindness)
Xerophthalmia Right Ans - Dry eyes (caused by vitamin A deficiency and
metaplasia); can lead to keratomalacia
Keratomalacia Right Ans - Corneal destruction due to vitamin A deficiency;
can eventually result in blindness; example of metaplasia, columnar
epithelium becomes squamous, and can lead to xerophthalmia (dry eye)
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