Cellular Adaptations Flashcards
(25 cards)
What is the restriction point of the cell cycle?
Critical check point for cell replication
Triggers DNA repair or apoptosis
How is the cell cycle controlled?
Cyclins + CDKs (cyclin dependent kinases)
CDKs activated by binding with cyclins
What is hyperplasia?
Cells increase in number above normal
What is hypertrophy?
Cells increase in size
What is atrophy?
Cells become smaller
What is metaplasia?
Cells are replaced by cells of a different type
In what tissues does hyperplasia occur?
Labile or stable tissues
Caused by increased functional demand or hormonal stimulation
In which tissues does hypertrophy occur?
Labile, stable and permanent tissues
Caused by increased functional demand or hormonal stimulation
Cells contain more structural components
What are examples of physiological hyperplasia?
Endometrium under influence of oestrogen
Bone marrow produces RBCs in hypoxia
What are examples of pathological hyperplasia?
Eczema
Thyroid goitre
What are examples of physiological hypertrophy?
Skeletal muscle
Pregnant uterus
What are examples of pathological hypertrophy?
RV hypertrophy in hypertension
Bladder hypertrophy as a result of an enlarged prostrate
What is compensatory hypertrophy?
Usually occurs in paired organs
One organ is underperforming so other hypertrophies to compensate
What happens in cell atrophy?
Cell shrinks to a size where survival is still possible
Reduced structural components
What happens in tissue atrophy?
Combination of cellular atrophy and apoptosis
Parenchymal cells apoptose - replaced by fibrous tissue
Reversible up to a point
What are examples of physiological atrophy?
Ovarian atrophy in post menopausal women
Uterus after birth
What are examples of pathological atrophy?
Atrophy of disuse
- muscle atrophy
Loss of innervation
- wasted hand muscles after median nerve damage
Inadequate blood supply
- skin thinning with PVD
Inadequate nutrition
- malnutrition
Loss of hormonal stimuli
- breast
- ovarian tissue
Persistent injury
What happens in metaplasia?
Due to altered stem cell differentiation
Adaptive substitution of cells that are sensitive to stress
Occurs in labile or stable tissues
Reversible
Examples of metaplasia
Barrett’s oesophagus
Spleen taking on role of bone marrow
What is aplasia?
Complete failure of a specific tissue or organ to develop
What is hypoplasia?
Underdevelopment or incomplete development of tissue or organ at embryonic stage
Congenital condition
What is involution?
Normal programmed shrinkage of an organ
E.g. uterus after childbirth
What is reconstitution?
Replacement of a lost part of the body
What is atresia?
Congential imperforation of an opening
