Cellular Adaptations Flashcards
How can a cell population increase its numbers?
1) Shorten the cell cycle
2) Convert quiescent cells to proliferating cells by making them enter the cell cycle
What is the restriction point?
A point in G1 of the animal cell cycle at which the cell becomes “committed” to the cell cycle and after which extracellular proliferation stimulants are no longer required
In cancer, where are there usually mutations?
In cyclins, CDKs or CDK inhibitors
What are the different types of cellular adaptations?
Hyperplasia, hypertrophy, atrophy, metaplasia
What is hyperplasia?
Increase in tissue or organ size due to increased numbers of cells
In which types of tissues does hyperplasia occur?
Labile or stable tissues
What causes hyperplasia?
Increased functional demand or hormonal stimulation
How does hyperplasia differ from neoplasia?
In hyperplasia, the organ/tissue growth remains under physiological control and is reversible
What are some examples of physiological hyperplasia?
Proliferative endometrium under influence of oestrogen
Bone marrow producing erythrocytes in response to hypoxia
What are some examples of pathological hyperplasia?
Hyperplasia of epidermis - eczema
Thyroid goitre in iodine deficiency
What is hypertrophy?
Increase in tissue or organ size due to increase size of cells
In which cell types does hypertrophy occur?
Labile, stable but especially permanent tissues
In which tissues do hypertrophy and hyperplasia usually occur together?
Labile and stable
What are some examples of physiological hypertrophy?
Hypertrophy of skeletal muscle (exercise) Pregnant uterus (hyperplasia and hypertrophy)
What are some examples of pathological hypertrophy?
In the heart (LV hypertrophy - hypertension, aortic stenosis)
Bladder (enlarged prostate gland)
Why don’t athletes get cardiac muscle hypertrophy?
They rest - in somebody with pathological cardiac hypertrophy, the heart is always having to work hard so is always slightly hypoxic
What is compensatory hypertrophy?
Hypertrophy of one of a pair of two organs or part of an organ
What is atrophy?
Shrinkage of tissue or organ due to an acquired decrease in size and/or/number of cells
What is organ/tissue atrophy usually due to?
Combination of both cellular atrophy and apoptosis
What types of atrophy are there?
Pressure, disuse, ischaemic, neurogenic, nutritional, endocrine
How is the mechanism in which the individual cells each become smaller brought about?
Lipid peroxidation of cell membranes
True or False:
If the cell membrane is broken down into polymers of lipid and other compounds, unfortunately the cell can’t fully degrade some of these and has to store them in phagolysosomes in the cytoplasm.
True
What is the name of the brown pigment derived from breakdown of lipid membranes?
Lipofuscin
What is an example of physiological atrophy?
Ovarian atrophy in post menopausal women, thymus in children
What are some examples of pathological atrophy>
Disuse atrophy, loss of innervation, inadequate blood supply, inadequate nutrition, loss of endocrine stimuli, aging, pressure
What is metaplasia?
Reversible change of one differentiated cell type to another
What is metaplasia due to?
Altered stem cell differentiation
What cell types does metaplasia occur in?
Stable and labile cell types
True or False:
Metaplasia involves expression of a new genetic progamme
True
What examples are there of metaplasia?
Bronchial pseudostratified ciliated epithelium to stratified squamous epithelium due to cigarette smoke
Stratified squamous epithelium to gastric glandular epithelium with persistent acid reflux
What is aplasia?
The failure of an organ or tissue to develop or to function normally
What is hypoplasia?
The underdevelopment or incomplete development of a tissue or organ
What is involution?
The shrinkage of an organ in old age or when inactive, e.g. of the uterus after childbirth
What is atresia?
The absence or abnormal narrowing of an opening or passage in the body.
What is dysplasia?
Abnormal maturation of cells within a tissue
What is reconstitution?
Replacement of a lost part of the body
