P3- Disorders of Growth and Neoplasia Flashcards
What is the size of the cell population in adult tissues determined by?
rates of cell proliferation, differentiation and death by apoptosis
What can cell numbers be altered by?
rates of stem cell input, by cell death due to apoptosis or by changes in the rate of proliferation or differentiation
What is the key to regeneration of a cell population?
control of the cell cycle
what is the cell cycle controlled by?
chemical factors in the microenvironment of the cell :
-stimulation and inhibitors
what can growth result from?
– Shortening cell cycle time
– Recruiting cells from resting or quiescent population
What cells are not capable of replicating?
Terminally differentiated cells e.g. myocytes
What happens to cells in the liver/kidney?
differentiated cells are normally quiescent but can proliferate when needed
What happens to epithelia of oral cavity, gut and the skin?
the mature cells are terminally differentiated, short-lived and incapable of replicating but may be replaced by new cells arising from stem cells
Name 3 inhibitors of apoptosis.
– Growth factors
– Cell matrix components
– Viral proteins
Name 3 inducers of apoptosis.
– Withdrawal of growth factors
– Loss of matrix attachment
– Viruses
Name the molecular mediators and regulators of apoptosis.
– Extrinsic pathway • Death receptors – Intrinsic pathway • Increased mitochondrial permeability • Can induce OR inhibit – Caspases - cascade – p53
What is hypertrophy?
• An increase in cell size • Physiological and pathological • Muscle: – Skeletal – Cardiac
What is hyperplasia?
• An increase in cell number • Physiological and pathological. • Hormonally sensitive organs: – Endometrium – Breast – Thyroid
What happens in hyperplasia?
- Enlargement of gingival tissues
- Hyperplastic responses within epithelium and underlying connective tissue
- Various causes including certain drugs
What is atrophy?
• Reduction in cell size by loss of cell substance
• Manycauses
• Physiological (thyroglossal duct)and pathological
– Ageing
– Lack of use / stimulation
• Mechanical
• Functional
What is hypoplasia?
- Reduced size of an organ that never fully developed to normal size
- Adevelopmental defect
- e.g. pulmonary hypoplasia
What is metaplasia?
- REVERSIBLE change in which one adult cell type is replaced by another adult cell type
- Can be part of an adaptive response to stress
- Reprogramming of stem cells
- Barrett’s oesophagus,
- Cervix, Bronchus,
- Salivary ducts (sialometaplasia)
What can metaplasia also effect?
- Can also affect mesenchymal tissues
- Not in itself a neoplastic disorder
- Environmental changes leading to metaplasia may if persistent lead to further changes that can manifest as dysplasia and progress to malignancy (cancer) – e.g. Barrett’s oesophagus
What disorder of growth and neoplasia are reversible?
o Hypertrophy o Hyperplasia o Atrophy o Metaplasia o Dysplasia o Neoplasia
What disorder of growth and neoplasia are irreversible?
hypoplasia
What does dysplasia mean?
disordered growth
Describe dysplasia.
• A pre-malignant process • Can be identified in many tissues • Epithelia are a good example – Squamous – Glandular
What happens to do the epithelium in dysplasia?
Atypical epithelial alterations limited to the surface epithelium
Alterations in:
- Architecture
- maturation
- Differentiation
What are the 3 different degrees of dysplasia?
– Mild
– Moderate
– Severe / carcinoma in situ
what do more severe forms of dysplasia have a significant risk for?
progressing to invasive malignancy
What does neoplasia mean?
New growth
What is neoplasia?
A neoplasm is an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissues, and persists in the same excessive manner after cessation of the stimuli that evoked the change
What does neoplasia result from?
Aberration of the normal mechanisms that control cell number ie
- Cell production by cell division
- Cell loss by apoptosis
What are features of most tumours?
Most tumours are monoclonal ie all the cells in a tumour appear to arise from one parent cell which has undergone a genetic change. This is then passed on to all the progeny
What do tumour cells lack?
the normal control mechanisms thus the clone expands due to uncontrolled proliferation
What are the two types of tumour?
- Benign
- Malignant
What is epidemiology?
Study of the distribution of diseases in different populations over time
(incidence, prevalence, geographical distribution)
What is incidence?
Number of new cases
What is Prevalence?
Number of existing cases
What do patients have in common?
- Rare cancers can show strong links
- Common cancers may be less easily associated with a putative causal agent
What can be understood about the risk factors and pathogenesis of cancer by studying?
geographic distribution, racial prevalence, occupation of those affected etc
What affects epidemiology and cancer?
- Age
- Sex (reproductive history)
- Culture/ religion
- Hobbies/recreation
- Geographic location (environment, local industry, occupation)
- Family history
- Medical history
- Diet
- Smoking
Name some major risk factors for oral cancer.
– Smoking – Alcohol – Betel/areca nut – Immunosuppression – Previous oral cancer
