7. Cell Adaptations Flashcards
What does the size of cell populations depend on?
Rate of cell proliferation, cell differentiation, and cell death by apoptosis.
What regulates normal cell proliferation?
Proto-oncogenes.
What are the final outcomes of cellular adaptations?
Survive - resist apoptosis.
Divide - enter cell cycle.
Differentiate - take on specialised form and function.
Die - undergo apoptosis.
What forms of cell to cell signalling are there?
Hormones, local mediators, and direct cell-cell or cell-stroma contact.
What are growth factors involved in?
Cell proliferation.
How do growth factors regulate cells entering the cell cycle?
Bind to specific receptors, stimulate transcription of genes that regulate entry of cell into cell cycle.
What do growth factors affect?
Cell proliferation and inhibition, locomotion, contractility, differentiation, viability, activation, angiogenesis.
What are four types of important growth factors?
EGF - epidermal growth factor.
VEGF - vascular endothelial growth factor.
PDGF - platelet derived growth factor.
GCSF - granulocyte colony-stimulating factor.
How is growth in the cell cycle increased?
Shortening the cell cycle, conversion of quiescent cells to proliferating cells by making them enter the cell cycle.
What happens in each of the steps of the cell cycle?
G1 - gap 1, presynthetic, cell grows.
S - DNA synthesis.
G2 - gap 2, premitotic, cell prepares to divide.
M - mitosis.
What is the most critical checkpoint of the cell cycle?
R (restriction) point towards the end of G1. Most commonly altered in cancer cells.
What controls the cell cycle?
Cyclins and CDKs.
What are labile cell populations?
Stem cells divide persistently to replenish losses.
What are stable cell populations?
Stem cells normally quiescent or proliferate very slowly, but proliferate persistently when required.
What are permanent cell populations?
Stem cells present, but cannot mount an effective proliferative response to significant cell loss.
What are the five types of cell adaptation?
Regeneration - cells multiply to replace losses.
Hyperplasia - cells increase in number above normal.
Hypertrophy - cells increase in size.
Atrophy - cells become smaller.
Metaplasia - cells are replaced by cells of a different type.
What will the result of a harmful agent be if it is removed, there is limited tissue damage, and regeneration?
Resolution.
What will the result of a harmful agent be if it persists, there is extensive tissue damage, and permanent cells?
Scar.
How many times can human cells regenerate?
61.3
What is reconstitution?
Replacement of a lost part of the body.
Which cell populations does hyperplasia happen in?
Labile or stable cell populations.
Which cell population does hypertrophy happen in?
Permanent cells.
What are some physiological examples of hyperplasia?
Proliferation of endometrium under the influence of oestrogen. Bone marrow producing erythrocytes in response to hypoxia.
What are some pathological examples of hyperplasia?
Eczema, thyroid goitre in iodine deficiency.
What are some physiological examples of hypertrophy?
Skeletal muscles and pregnant uterus (hypertrophy and hyperplasia).
What are some pathological examples of hypertrophy?
Right ventricular hypertrophy.
What are some physiological examples of atrophy?
Ovarian atrophy in post menopausal women.
What are some pathological examples of atrophy?
Atrophy of disuse - muscle atrophy.
Denervation atrophy - wasted hand muscles after median nerve damage.
Inadequate blood supply - thinning of skin on legs with peripheral vascular disease.
Inadequate nutrition - wasting of muscles with malnutrition.
Loss of endocrine stimuli - breast.
Persistent injury - polymyositis.
Senile atrophy - brain, heart.
Pressure - tissues around an enlarging benign tumour.
What example of metaplasia does smoking cause?
Bronchial pseudostratified ciliated epithelium to stratified squamous epithelium in the respiratory system.
What example of metaplasia does acid reflux, Barrett’s oesophagus, cause?
Stratified squamous epithelium to gastric glandular epithelium.
What is hypoplasia?
Underdevelopment or incomplete development of a tissue or organ at the embryonic stage, inadequate number of cells.
What is aplasia?
Complete failure of a specific tissue or organ to develop, an embryonic developmental disorder.
What is involution?
Overlaps with atrophy, normal programmed shrinkage of an organ - like uterus after childbirth.
