7.1b Cell adaptations of growth and differentiation Flashcards
(clinical relevance of 5 types of cell adaptation & distinguish from aplasia, hypoplasia, dysplasia )
Is cell adaptation reversible or irreversible ?
reversible
Adaptations are often …1… changes in cellular.
….2…. (5) changes due to ..3.. or ….4….
- reversible
- size,number,phenotype, metabolic activity, function
- environment
- demand
what’s regeneration ?
replacement of cell losses by identical cells to maintain tissue or organ size
Harmful agent -> resolution, steps ?
- harmful agent removed
- limited tissue damage
- regeneration
- resolution
harmful agent -> scar, process ?
- harmful agent persists
- extensive tissue damage
- permanent cells
- scar
- ….. capacity of tissue vary
- cells can regenerate …..
- only … cells can proliferate …..
- regenerative
- many times
- stem , indefinitely
hayflick number = amount of times a line of cells can ….?
divide before telomere loss prevents further division
Hayflick number varies….
dependent on the species
- reconstitution is what ?
- requires ….
- replacement of a lost part of the body
- coordinated regeneration of several types of tissues
mammals ability to reconstitute a body part is ?
minimal
In wound healing what’s able to reconstitute ?
small blood vessels
give 2 examples of cells that regenerate and do they ?
- liver - hepatocytes, post lobectomy
- skin epidermis, post burn
what’s hyperplasia ?
increase in tissue or organ size due to increased cell numbers
Which cell populations can hyperplasia only occur in ?
labile or stable because permanent cannot divide
Which control does hyperplasia remain under ? & is reversible
physiological control
Hyperplasia can occur secondary to a pathological cause i.e ?
proliferation is a normal reponse to another abnormal condition -> neoplasia - the proliferation in itself is abnormal
What does repeated cell divisions expose the cell to ?
risk of mutations and neoplasia (not always?)
physiological & pathological of hyperplasia ?
physiological:
* hormonal
* compensatory
pathological:
* excess hormonal stimulation
* growth factor production
2 Physiological examples of hyperplasia ?
- proliferative endometrium under influence of oestrogen / increase in breast gland for lactation
- bone marrow produces erythrocytes in response to hypoxia
pathological example of hyperplasia
thyroid goitre in iodine deficiency
Pathological hyperplasia usually occurs secondary to ….1… or ….2….
- excess hormonal stimulation
- growth factor production
what’s hypertrophy ?
increase in tissue or organ size due to increase in cell size without increase in cell number
Why do cells become bigger in hypertrophy ?
they contain more structural components (not because of swelling)
Which tissue us hypertrophy especially seen in ?
permanent tissues
Why does hypertrophy mainly occur in permanent tissues ?
these tissues have little replicative capacity and so increase in organ size MUST occur via hypertrophy
pathological examples of hypertrophy ?
- ventricular cardiac hypertrophy due to hypertension
- bladder smooth muscle hypertrophy with obstruction due to enlarged prostate gland (hypertrophy & hyperplasia)
Atrophy definition ?
shrinkage in size of cell by loss of cell substance
where is shrinkage in the size of the cell to a size which survival is still possible
Organ/tissue atrophy is typically due to a combination of ?
cellular atrophy and apoptosis
Examples of physiologic and pathologic atrophy ?
physiologic
* during early development
* e.g. thyroglossal duct atrophy in adolescence, thymus atrophy
pathologic
* depending on cause, localised or generalised
3 physiological examples of atrophy ?
- ageing = thymus gland atrophy as age
- ovarian atrophy = post-menopausal women
- decrease in seize of uterus = after parturition (childbirth)
8 pathological examples of atrophy ?
- Reduced functional demand/workload: muscle atrophy after disuse, reversible with activity
- Loss of innervation = denervation atrophy: wasted hand muscles after median nerve damage
- Inadequate blood supply: thinning of skin on legs with peripheral vascular disease
- Wasting of muscles with malnutrition + immobility = sarcopaenia [fundamental pathogenesis of frailty]
- Loss of endocrine stimuli: breast, reproductive organs
- Persistent injury: polymyositis (inflammation of muscle)
- Aging = senile atrophy: brain, heart
- Pressure: tissues around an enlarging benign
tumour (probably secondary to ischaemia)
What’s slim disease in AIDS an example of ? due to what ?
- gross body atrophy (wasting)
- due to HIV infection and disseminated tuberculosis
mechanism of atrophy ?
- decreased protein synthesis
- increased protein degradation (ubiquitin proteasome path)
- increased autophagy (residual bodes; autophagosomes with lipofuscin)
What’s metaplasia ?
reversible change in which one adult cell type is replaced by another cell type
Metaplasia is most clelarly adaptive in which tissue ?
epithelial
Metaplasia is due to what differentiation ?
altered stem cell
What may metaplasia represent ?
an adaptive substitution of cells that are sensitive to stress by cell types better able to withstand the adverse environment
How does the differentiation status of cells in metaplasia compare to that in dysplastic and cancerous epithelium?
In metaplasia, cells are fully differentiated
In contrast, dysplastic and cancerous epithelia have disorganized and abnormal differentiation, with cancerous cells exhibiting irreversible changes
What is metaplasia sometimes a prelude to ?
dysplasia and cancer
2 examples of metaplasia ?
- bronchial pseudostratified ciliated epithelium -> stratified squamous epithelium due to effect of cigarette smoke
- stratified squamous epithelium -> gastric glandular epithelium with persistent acid reflux (Barrett’s oesophagus)
A detrimental and no apparent use of metaplasia is transformation of bronchial pseudostratified ciliate columnar epithelium to stratified squamous epithelium due to cigarrette smoking
explain the effect of this transformation
squamous epithelium doesn’t produce cleansing mucus and lack cilia to move it along making the smoker more vulnerable to respiratory infections
Metaplasia can sometimes be a prelude to dysplasia and cancer.
Give an example of this.
Severe types of epithelial metaplasia predispose to malignant epithelial cancers e.g., Barret’s oesophagus and intestinal metaplasia of the stomach (which occurs in chronic H. pylori infection).
what’s aplasia ?
- complete failure of a specific tissue or organ to develop
- an embryonic developmental disorder (congenital)
Example of aplasia
thymic aplasia results in susceptibilty to infections and auto-immune problems
What’s hypoplasia ?
underdevelopment or incomplete development of a tissue or organ at embryonic stage, inadequate number of cells
What is hypoplasia in a spectrum with ?
aplasia
example of hypoplasia ?
- kidneys
- breasts
- testes in klinefelter’s syndrome
- chambers of heart
- definition of dysplasia ?
- potentially …
- often…
- in skin : dysplasia =
- abnormal maturation of cells within a tissue
- reversible
- pre-cancerous
- carcinoma in situ
What are the 2 completely different meaning dysplasia has in pathology ?
- abnormal cellular development with abnormal cell cycling and accumulating genetic abnormalities, leading to cancer
- abnormal development or maturation leading to malformation of an organ, eg renal dysplasia & fibrous dysplasia of bone
