4. 3. Atrophy
(smaller cells)
1. Physiologic
During development: i.e. notochord; thyroglossal duct
2. Pathologic (local or generalized) via
* disuse * Loss of endocrine stimulation
* denervation * Aging
* ischemia * Pressure
5. Atrophy
(Mechanism)
Reduction in structural components
Decreased number of mito, myofilaments, ER via
proteolysis (lysosomal proteases; ubiquitin-
proteosome system)
Increase in number of autophagic vacuoles
Residual bodies (i.e. lipofuscin brown atrophy)
11. Muscle fiber atrophy. The number of cells is the same as before the
atrophy occurred, but the size of some fibers is reduced. This is a
response to injury by "downsizing" to conserve the cell. In this case,
innervation of the small fibers in the center was lost. This is a trichrome
15. Hyperplasia
(more cells)
1. Physiologic
* Hormonal (breast/uterus in pregnancy)
* Compensatory (liver after partial hepatectomy)
2. Pathologic
Excessive hormone/GF stimulation of target
tissue
* Endometrial hyperplasia (x’s estrogen)
16. Hyperplasia
(Mechanism)
Cell proliferation
via increased production of TRANSCRIPTION FACTORS
due to
* Increased production of GF
* Increased levels of GF receptors
* Activation of intracellular signaling
23. CARDIAC HYPERTROPHY
Myocardial
hypertrophy.
- Cross-section of the
heart of a patient with long-
standing hypertension
- Shows pronounced,
concentric left ventricular
hypertrophy
26. Question
Which term is most likely to fit the
description of the uterus during
pregnancy?
A. hyperplasia
B. hypertrophy
C. aplasia
D. dysplasia
E. metaplasia
27. Metaplasia
(Mechanism)
Reprogramming
1. of stem cells present in normal tissues
2. of undifferentiated mesenchymal cells
in connective tissue
Mediated by signals from
cytokines, Growth Factor
Leading to induction of specific transcription
factors
29. 4. Metaplasia
**One adult cell type replaces another**
Reversible
Columnar to squamous epithelium (most common epithelial -type of
metaplasia)
Chronic irritation i.e. (in trachea and bronchi of smokers)
Vit A deficiency squamous metaplasia in respiratory epithelium
30. Photomicrograph of the junction of normal epithelium
(1) with hyperplastic transitional epithelium (2).
31. Photomicrograph of the trachea from a smoker. Note that the columnar
ciliated epithelium has been replaced by squamous epithelium.
33. DYSPLASIA-Left
• Cellular dysplasia refers to an alteration in the size, shape
and organization of the cellular components of a tissue.
• It is established that dysplasia is a preneoplastic lesion, in
the sence that, it is a necessary stage in the multi-step cellular
evolution to cancer.
36. Question
Which of the following best describes the
phenomenon of epithelial dysplasia?
A. an increase in thickness of the epithelium because of
increased number of cells
B. a decrease in thickness of the epithelium owing to
decrease in the number of dividing cells
C. an irregular proliferation and maturation of cells
throughout the layers of the epithelium
D. an increase in the thickness of the epithelium owing to
enlargement of the component cells
E. absence of epithelium because of lack of cell
proliferation
38. Muscular Dystrophy
• What Is Muscular Dystrophy?
Muscular dystrophy is a disease in which the
muscles of the body get weaker and weaker and
slowly stop working because of a lack of a
certain protein (see the relationship to
genetics?)
• Can be passed on by one or both parents,
depending on the form of MD (therefore is
autosomal dominant and recessive)
Glucocorticoids, thyroid hormone and TNF stim proteosome-mediated protein degradation; insulin opposes
Kidney: atrophy via renal artery stenosis. NB: decrease in cortex (most metabolically active cells)
Hormonal: Breast at puberty; breast and uterus during pregnancy Compensatory: regeneration of liver after partial hepatectomy NB; hyperplasia regresses if stim removed; difference with cancer
Lft: normal thyroid gland: rings of epithelial cells surrounding colloid. Rt: hyperplasia/hypertrophy of Graves d; note epithelial projections into colloid.
Hypertrophy
Middle = normal heart; left = hypertrophied heart due to hypertension; rt = dilated heart due to inability to adapt to continued stress
Squamous thought to be more durable cell type Squamous epithelium don’t mucus Acid reflux col to squamous metaplasia (Barrett esophagus) Connective tissue metaplasia = formation of bone, cart, or adipose tissue in tissues that normally don’t contain them