ADAPTATIONS Flashcards
Define Adaptation
Adaptations are reversible changes in the size, number, phenotype, metabolic activity, or functions of cells in response to:
1) changes in physiologic states
2) some pathologic stimuli
TO REACH
new but altered steady states
TO ALLOW
the cell to survive and continue to function
Describe the types of adaptations
1- HYPERTROPHY: increase in the size of the cells and functional activity
2- HYPERPLASIA: increase in cell number
3- ATROPHY: Decrease in the size of cells and metabolic activity
4- METAPLASIA: change in the phenotype of cells
5- DYSPLASIA: Abnormal growth or development, but NOT CONSIDERED ADAPTATION, first step of neoplastic transformation, still reversible
Describe hypertrophy
1- It is the increase in the size of cells, that results in an increase in the size of the affected organ
2- THey are bigger for synthesis and assembly of additional intracellular structural components
3- May coexist with hyperplasia adn contribute to increased size
4- Not capable of division
Explain hypertrophy in striated muscle cells
1- Caused by increased functional demand or by
stimulation by hormones and growth factors
2- Hypertrophy of striated muscle cells
1) skeletal muscles in response to increased workload
2) heart for chronic hemodynamic overload
(hypertension or faulty valves)
The muscle cells syntetize more proteins and the
number of myofilaments increases.
Increase in the force of the muscle
In the heart can lead to heart failure, arrhythmias and
sudden death
Example of normal physiological hypertrophy
Pregnancy: hypertrophy of
muscle fibers of the uterus due to
estrogenic hormones.
Explain the mechanism of myocardial hypertrophy
1• Increased protein synthesis -->increased cell size --> increased organ size 2• Nondividing cells produce more protein and membrane without division 3• Mechanosensors, PI3K /Akt signaling pathway important in exercise- induced growth 4• Growth factors, vasoactive agents, hormones mediate stress-induced response 5• Unrelieved stress eventually results in irreversible injury 6• Expression of fetal or embrionic proteins -contractile proteins (more energetically economical contraction) -atrial natriuretic factor (ANF) (causes salt secretion by the kidney, decreases blood volume and pressure, reduce hemodynamic load).
Explain the epidemiology Cardiac hypertrophy
1• Prolonged hypertrophy is a highly important risk factor for the development of
heart failure
2• Cardiac hypertrophy includes a group of inherited conditions that produce
hypertrophy of the myocardium in the absence of an alternate cause (e.g.
aortic stenosis or hypertension).
3• It is the most common cause of sudden cardiac death in young people and
affects 1 in 500 of the population.
4• The majority of cases are familial autosomal dominant, due to mutations in the
genes encoding sarcomeric proteins .
5• The most common causes of cardiac hypertrophy are mutations of the β-
myosin heavy chain and myosin-binding protein C.
6• Often asymptomatic
7• Symptoms: CHEST PAIN and atrial fibrillation
Describe Hyperplasia
- Definition: Increase in the number of cells in
an organ or tissue in response to a stimulus.
2• frequently occur together with hypertrophy
(same stimulus)
3• Only in tissues composed by cells
capable of dividing
4• physiologic or pathologic.
Examples of physiological hyperplasia
1) Hormonal:
- proliferation of the glandular epithelium of the
female breast at puberty and during pregnancy, usually
accompanied by enlargement (hypertrophy) of the glandular
epithelial cells. - Endometrial profileration during normal menstrual cycle
2) Compensatory:
- after damage or resection. Best example is
liver and bone marrow regeneration.
Explain Pathologic Hyperplasia
- Caused by excessive or inappropriate actions of hormones or
growth factors acting on target cells. - Pathologic hyperplasias are abnormal, but can regresses if the
hormonal stimulation is eliminated.
3. Hyperplasia is distinct from cancer but pathologic hyperplasia constitutes a fertile soil in which cancerous proliferations may eventually arise (endometrium hyperplasia increases risk for developing endometrial cancer).
Example of pathologic hyperplasia
1- Endometrial hyperplasia: pathologic when the balance
between estrogens and progesterone is disturbed;;
abnormal menstrual bleeding/Abnormal vaginal bleeding
2- Benign prostatic hyperplasia: induced by androgens.
Explain the mechanism of Hyperplasia
- Growth factor-driven proliferation of mature cells
2. Proliferation of tissue stem cells
Describe Atrophy
1- Defintion: Reduction in the size of an organ or tissue due to
a decrease in cell size and number.
2- Could physiologic or pathologic
3- Physiologic atrophy
during fetal development.
decrease in the size of the uterus that occurs shortly after parturition
What are the casues of pathological atrophy?
1• Decreased workload (atrophy of disuse).
Es: skeletal muscle atrophy after immobilization
2• Loss of innervation (denervation atrophy).
Metabolism of skeletal muscle are dependent on its nerve supply.
3• Diminished blood supply.
Es: brain and heart atrophy for atherosclerosis (senile atropy)
4• Inadequate nutrition.
Use of skeletal muscle proteins as a source of energy
marked muscle wasting (cachexia)
5• Loss of endocrine stimulation.
Physiologic atrophy of the endometrium, vaginal
epithelium, and breast due to loss of estrogen stimulation after menopause
6• Pressure.
Tissue compression by benign tumor can cause atrophy as a result of ischemic
Explain the mechanism of atrophy
1- Decreased protein synthesis for
reduced metabolic activity.
2- Increased protein degradation by the
ubiquitin-proteasome pathway.
3- Increased autophagy (“self-eating”)
starved cell eats its own components
in an attempt to reduce nutrient
demand to match the supply
