general pathology lecture 4 cellular adaptation
TRANSCRIPT
Adapted
Cell
+StressNormal
cell
Stress = ?
Increased/decreased workload
* skeletal muscle and body building
* cardiac muscle and hypertension
* skeletal muscle disuse (limb immobilization)
Increased/decreased stimulation
* estrogenic stimulation of uterus in pregnancy
* estrogen/prolactin stimulation of breast (lactation)
* denervation of muscle
- Stress
Adapted
Cell
Cellular adaptations to stress
1. Hyperplasia (more cells)
2. Hypertrophy (bigger cells)
3. Atrophy (smaller cells)
4. Metaplasia (different types of cells)
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
* Nutrition
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)
NB: diminished function but not dead
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
stain.
HyperplasiaHyperplasia((more cells)more cells)
1. 1. PhysiologicPhysiologic
* Hormonal (breast/uterus in pregnancy)
* Compensatory (liver after partial hepatectomy)
2. Pathologic2. Pathologic
Excessive hormone/GF stimulation of target
tissue
* Endometrial hyperplasia (x’s estrogen)
* Benign prostatic hyperplasia (x’s androgens)
* Connective tissue cells in wound healing
HyperplasiaHyperplasia(Mechanism)
Cell proliferation
via increased production of TRANSCRIPTION FACTORS
due to
* Increased production of GF
* Increased levels of GF receptors
* Activation of intracellular signaling
Results in larger organ
Adapted
Cell
2. Hypertrophy (larger cells)
* Not due to swelling
* Increased synthesis of structural
components
* Results in larger organ
* May occur with hyperplasia
CARDIAC HYPERTROPHY
Myocardial hypertrophy. - Cross-section of the heart of a patient with long-standing hypertension - Shows pronounced, concentric left ventricularhypertrophy
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
Metaplasia(Mechanism)
Reprogramming
1. of stem cells present in normal tissues
2. of undifferentiated mesenchymal cells in connective tissue
Mediated by signals from
cytokines, GF or ECM
Leading to induction of specific transcription factors
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
May be some loss of function
May predispose to maligancy
Photomicrograph of the junction of normal epithelium
(1) with hyperplastic transitional epithelium (2).
Photomicrograph of the trachea from a smoker. Note that the columnar
ciliated epithelium has been replaced by squamous epithelium.
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.
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
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)