6-Adaptive Tissue Responses Flashcards
Define adaptive changes.
Changes in mature cells and tissues after growth has occurred
What are the factors that determine a cells ability to adapt?
Vulnerability to certain agents State of differentiation (labile/stable/permament) Blood supply Nutrition Previous state of the cell
What are the different types of changes a cell/tissue can undergo?
Atrophy
Hyperplasia
Hypertrophy
Metaplasia
What is atrophy?
Reduction in the size of the organ or tissue due to decrease in size/number of its specialised cell
What can cause atrophy of an organ/tissue?
Decreased blood supply Loss of innervation Decreased workload (disuse) Prolonged pressure Loss of hormonal/endocrine stimulation Lack of nutrition Physiological Senile atrophy (aging)
Give an example of a physiological change that causes atrophy of a tissue/organ
Thymus undergoes involution during puberty
Uterus decreases in size after parturition
What is the process involved in atrophic changes of a cell/tissue/organ?
Apoptosis
Explain the mechanism of atrophic changes in cells/tissues
Apoptosis: decrease I’m the number if cells (decreased number of organelles)
Reduction cell size due to catabolic > anabolic processes (increased proteolysis/protein degradation by ubiquinisation stimulated by growth hormones and cytokines) - fewer mitochondria, myofilaments, ER and increased autophagic vacuoles
Define hyper trophy
Increase In size of an organ/tissue due to an increase in size of the specialised cells
Generally what causes an increase in size during hypertrophic changes?
Increased workload on cells that cannot divide to form new cells
Increased number of organelles that are limited by the SA:Vol therefore results in increase in size
What are the two categories of the causes of hypertrophic changes?
Compensatory (increased functional demand)
Hormonal (specific hormonal stimulation)
What are the compensatory causes of hypertrophy?
Removal of a kidney
Heavy work load of skeletal muscles
Increased BP in myocardium
What is are the hormonal causes of hypertrophy?
Pregnancy - hypertrophy of the uterus
What can stimulate the signal transduction pathways that cause increase in organelles and cell size during hypertrophy?
Mechanical/physical triggers
Tropic triggers
Give example(s) of mechanical or physical triggers in hypertrophic changes
Stretching of myocardium
What are some of the trophic triggers of hypertrophy?
Growth factors Vasoactive factors (cytokines and hormones)
What are the two possible forms of cardiac muscle hypertrophy?
Eccentric cardiac hypertrophy
Concentric cardiac hypertrophy
What is concentric cardiac hypertrophy?
Cardiac muscle hypertrophy with narrowing of heart chamber due to chronic pressure overloaded and increased resistance Reduced compliance (stiff) Reduced filling and diastolic dysfunction (shorter)
What is a possible outcome of the reduced filling and diastolic dysfunction consequence of concentric cardiac hypertrophy?
Possible cell death and ischemia
What type of cardiac hypertrophy occurs when there is chronic pressure overload and increased resistance (I.e. Vascular disease)?
Concentric cardiac hypertrophy
What type of cardiac hypertrophy occurs during exercise?
Increased blood supply to the heart results in eccentric cardiac hypertrophy
What occurs during eccentric cardiac hypertrophy?
Increased blood flow to the heart
Stress on heart due to volume overload
Lengthening of cardiomyocytes (not thickening)
Ventricular dilation
Normal relative sarcomere lengths - expansion to receive greater volume of blood
walls thicken in proportion to radius of chamber (dilation) therefore total size of chamber is relatively larger
What is the compensatory response to increase cardiac output in eccentric cardiac hypertrophy?
Dilation while stretching of cardiomyocytes allows increase in stroke volume
What will happen if cardiomyocytes are stretch beyond their limitations?
Decreases contractile strength (long term effects)
What is the adaptive change that results in an increase in the size of an organ/tissue due to and increase in the number of its specialised cells?
Hyperplasia
What is hyperplasia
increase in the size of an organ/tissue due to and increase in the number of its specialised cells
In what type of tissues is hyperplasia possible?
Stable or labile cells
Is hyperplasia possible in permanent cells? Why/why not?
No. Permanent cells are cells that have already left the cell cycle and are not able to replicate/re-enter in order to undergo hyperplasia
What are the causes of hyperplasia?
Increased local production of growth factors
Increased growth factor receptors
Activation of specific intracellular pathways
What are the three categories (physical and pathological) of hyperplasia?
Compensatory
Hormonal
Respiratory
What are the compensatory examples of physiological hyperplasia?
Haemopoietic system after blood loss
Mesenteric lymph nodes
What are the hormonal examples of physiological hyperplasia?
Normal cyclical changes in the mammary glands/endometrium
What are the compensatory examples of pathological hyperplasia?
Lymph nodes during infection
What are the respiratory examples of physiological hyperplasia?
Restoration of tissue architecture and function
What are the hormonal examples of pathological hyperplasia?
Excessive hormonal stimulation
- excess erythropoietin (polyothemia): common in athletes to increase RBC count
- excess oestrogen (dysmenorrhea)
Give examples of physiological hyperplasia
Haemopoietic system after blood loss
Mesenteric lymph nodes
Normal cyclical changes in the mammary glands/endometrium
Give examples of pathological hyperplasia
Lymph nodes during infection
Restoration of tissue architecture and function
Excessive hormonal stimulation
-excess erythropoietin (polyothemia): common in athletes to increase RBC count
-excess oestrogen (dysmenorrhea)
Define metaplasia
Change from one type of specialised, fully differential adult cell to another cell type with reduced/loss of function
Describe the mechanism of metaplasia
Protective/adaptive response (reversible) where stem cells are ‘reprogrammed’ within the affected organ
Changes in gene transcription/translation by cytokines, growth factors, ECM components
Give an example of metaplasia
Barrett oesophagus
