MOD 7 Flashcards
Name 3 factors that influence the size of a cell population
- cell proliferation
- cell differentiation
- death by apoptosis
What are 3 mechanisms and 3 things cells use for communication
Things: hormones, local hormones (growth factors), stroma-stroma contact
Mechanisms: autocrine, paracrine, endocrine
How do Stem cells divide and why is this method beneficial
They divide asymmetrically to replenish differentiated cells whilst keeping one stem cell able to continually fuel the stem cell population
Name two examples of labile tissue and its relevance to the cell cycle
Always in the cell cycle
a) epidermal hyperplasia from basal layer
b) Bone marrow - hyperplasia
Name two examples of stable tissue and its relevance to the cell cycle
In G0 but can be induced back into the cell cycle
a) osteoblasts
b) hepatocytes
Name three examples of permanent tissue and its relevance to the cell cycle
Does not enter the cell cycle, is only capable of hypertrophy
a) brain neurons
b) cardiac muscle
c) skeletal muscle
What are the 5 cellular adaptations?
- regeneration
- hypertrophy
- hyperplasia
- atrophy
- metaplasia
What is regeneration and reconstitution?
Regeneration is restoring the cell # back to normal, reconstitution is replacing an entire organ/body part which humans have little capacity to do - only our capillaries are capable of this.
What 3 conditions influence the formation of resolution?
- if injurious stimuli is removed
- non-extensive tissue damage
- if it’s in labile or stable tissues
What 3 conditions influence the formation of scarring?
- if injurious stimuli persists
- if tissue damage is extensive
- if it occurs in permanent tissues
What is hyperplasia, and what does it put you at risk for?
Cell proliferation, increases the chance of a mutation
2 Pathological hyperplasia examples (not cancer)
a) The goitre:
- TSI mimics TSH stimulating the thyroid to overwork and produce more T3 and T4.
- An iodine deficiency: no T3 and T4 being produces stimulates the thyroid to try harder and make more (no negative feedback)
b) Eczema: proliferation of the dermal layer
2 Physiological hyperplasia examples
a) endometrium under influence of estrogen
b) Bone marrow produces erythrocytes in response to hypoxia
What is Hypertrophy?
What are the conditions in which it is mainly seen
Increase in cell size
Done in permanent tissues and likely alongside hyperplasia in labile and stable tissues
2 Physiological examples of hypertrophy
a) skeletal muscle at the gym
b) During pregnancy your uterus undergoes hyperplasia and hypertrophy
2 Pathological examples of hypertrophy
a) Ventricle walls of the heart in response to hypertrophy, to increase the FOC
b) An enlarged prostate gland will cause hyperplasia and hypertrophy of the bladder
What is atrophy and what process is it usually in combination with?
The shrinking of a tissue/organ due to decrease in size and/or # of cells. Therefore it is highly associated with apoptosis (involution)
3 physiological examples of atrophy
a) loss of the thyroglossal duct
b) thymus shrinks with age
c) ovarian atrophy post-menopause
4 types of atrophy (all pathological)
- Disuse
- Denervation
- Scenile
- Sarcopenia - not enough nutrition
4 pathological examples for atrophy that are NOT a type of atrophy ;)
- Loss of blood supply - thinning of the skin over the legs
- Pressure - can be due to the pushing of a benign tumour on surrounding tissue
- Loss of endocrine stimuli - causes atrophy of breast and reproductive organs
- Persistent Injury - polymyositis: disease of constant inflammation to muscles and muscle associated tissues
What is metaplasia, is it reversible or irreversible and what is it often a precursor to?
Changing of a cell type in response to stress, a precursor to dysplasia (which is pre-malignant reversible until a neoplasm is formed).
Metaplasia is reversible
What might happen if you have constant acid reflux?
Barett’s esophagus:
stratified squamous epithelium change to gastric glandular epithelium
What could happen in the bronchus as a result of smoking?
Cell type changes from pseudostratified columnar - stratified squamous
What does aplasia mean? Provide an example
Complete failure to develop a specific tissue or organ, likely an embryological development disorder.
e.g: Thymus aplasia makes you prone to infections
What does dysplasia mean?
Abnormal maturation of cells within a tissue
What cell types is EGF mutagenic for and what cell types is it produced by?
Mutagenic for… hepatocytes, fibroblasts and epithelial cells
Produced by… macrophages, inflammatory cells and keratinocytes
What does VEGF do? What 3 processes is it important for?
Aid in vascularisation and angiogenesis
Important for chronic inflammation, tumours and wound healing
Where is PDGF stored and when is it released?
In platelet alpha granules and it’s released when platelets become activated
What other 4 cell types (other than platelets) secrete PDGF?
endothelial cells, macrophages, smooth muscle cells and tumour cells
What does PDGF do?
causes migration and proliferation of fibroblasts, smooth muscle cells and monocytes
What is the R point, and what does it do if it becomes activated?
Restriction point at the end of G1, known as the “point of no return” and is monitored by prb (a tumour suppressor gene)
If activated, the R point will slow the cell cycle and initiate DNA repair mechanisms such as apoptosis - facilitated by p53
How is the cell cycle controlled by cyclins and CDKs?
CDK (cyclin-dependent kinases) become active by binding with cyclin. Once active CDKs drive the cell cycle by phosphorylating proteins critical for cell cycle transitions
How is the activity of cyclin CDK complexes regulated? (3 things)
Cyclin is stimulated by many growth factors (stimulatory of the complex).
There are CDK inhibitors (inhibitory of the complex).
Some growth factors will also shut off the production of these CDK inhibitors (stimulatory)
