Lecture 34: Abnormal growth and differentiation Flashcards
What is adaptation defined as?
Defined as cellular changes in response to changes in environment or demand.
What might 5 changes from adaptation be seen in?
Cell size
Cell number
Cell phenotype
Metabolic activity
Cell function
Why would cells adapt?
Enables cells to survive as their environment changes, avoiding injury, reaching new metabolic steady state.
What 2 forms of adaptation are there?
- Physiological
- Pathological
Can adaptation be reversible?
Usually
What type of cells can adapt easily?
Labile populations with active stem cell compartments.
Give an example of a cell that can adapt easily?
eg. Epithelial cells
What type of cells cannot adapt easily?
Permanent population of terminally differentiated cells.
Give an example of a cell that cannot adapt easily?
Cerebral neurons
Give an example and why a cell may not need to adapt?
Some are inherently robust, not needing to adapt.
eg. Fibroblasts
How can cellular activity be increased?
Increasing the size or number of cells
How can cellular activity be decreased?
Decreasing the size or number of cells
What is hypertrophy?
increase in cell size
What is Hyperplasia?
increase in cell number.
What do both Hypertrophy and Hyperplasia result in?
Both result in increased mass of cells.
How does cell size increase in hypertrophy?
There is synthesis of more structural elements within the cell.
What does an increase in cell size lead to?
increased functional capacity of the cell.
Is hypertrophy physiological or pathological?
Can be both
In what type of cells is hypertrophy the most available mode of adaptation?
In cells with limited capacity for proliferation eg.skeletal and cardiac muscle.
What is Gravis Uterus?
induced hypertrophy of smooth muscle
What are the two types of physiological hyperplasia?
- Hormonal
- Compensatory
What are the subdivisions of pathological Hyperplasia?
Hormone or growth factor driven -> Proliferation of mature cells or/and Increased output of new cells
Explain an example of Compensatory physiological hyperplasia? (Liver regeneration)
Liver regeneration – eg. In transplant, donor liver undergoes hyperplasia in months following transplantation.
(Also has an element of hypertrophy in acute phase –remember, they can co-exist!)
What is Graves disease?
– thyroid hyperplasia, induced by autoimmune stimulation of TSH receptor.
What is endometrial hyperplasia?
often secondary to excess stimulation from oestrogen; several possible causes,eg.anovulation, obesity, ovarian pathology (granulosa celltumour, thecoma etc.).
What is atrophy?
Defined as reduction in the size of an organ or tissue, by reduction in cell size or number.
Give an example of physiological atrophy?
g. Uterus after pregnancy or menopause
Can atrophy be pathological and physiological?
Yes
Name 6 causes of pathological atrophy?
- Decreased workload (disuse atrophy).
- Loss of innervation (denervation atrophy).
- Inadequate nutrition.
- Diminished blood supply.
- Loss of endocrine stimulation.
- Pressure (likely related to diminished blood supply).
What can cerebral atrophy be exacerbated by?
by cerebrovascular disease, dementias of various types, etc.
When does involution of thymus occur and what happens?
Adolescence
Overall functioning mass of tissue replaced with fat cells
What does steroid therapy exert negative feedback on?
ACTH production
Reduces drive on adrenal gland
What is failure of formation of embryonic cell mass to a differentiation of organ specific tissues called?
Agenesis
What is aplasia?
Failure of structural organisation of tissues into an organ.
What is dysgenesis?
Failure of an organ growing to its full size
What is hypoplasia?
Failure of a normal organ developing
What are the 4 developmental causes of reduced cell mass?
- Agenesis
- Aplasia
- Dysgenesis
- Hypoplasia
What is Metaplasia?
transformation of one differentiated cell type into another.
What is the benefits of metaplasia?
Can give better adaptation to new environment.
Can affect epithelial and mesenchymal tissues.
Is metaplasia physiological or pathological?
Again, can be physiological or pathological.
Describe physiological cervical metaplasia?
enlargement/eversion of cervix during puberty and pregnancy exposes endocervical cells to more acid pH.
In response, endocervical cells undergo metaplasia from columnar to squamous type epithelium at transformation zone.
Describe Barrett’s oesophagus - a pathological metaplasia example?
chronic inflammation, usually secondary to acid reflux, induces transition from stratified squamous epithelium to columnar epithelium (intestinal type).
How does cigarette smoke trigger a metaplasia response?
Turns pseudostratified ciliated bronchial epithelium into squamous epithelium
How does chronic trauma trigger a metaplasia response?
Turns fibrocollagenous tissue into bone
How does chronic trauma trigger a metaplasia response?
Turns fibrocollagenous tissue into bone
Give 3 examples of adaptation leading to neoplasia?
Glandular metaplasia in oesophagus
-> Adenocarcinoma
Squamous Metaplasia in Cervix
-> CIN and squamous cell carcinoma
Endometrial hyperplasia due to increased oestrogens
-> Adenocarcinoma
Which is the earliest morphological manifestation of the multistage process of neoplasia?
Dysplasia
(Proliferation of atypical cells.)
Is dysplasia malignant and invasive?
Shows cytological features of malignancy, but not invasive.
Give an example of Dysplasia?
cervical intraepithelial neoplasia (CIN)/squamous intraepithelial lesion (SIL)
What is a neoplasm?
Abnormal growth of tissue with uncontrolled replication
What are the 3 different routes of metastasis?
- Lymphatics
- Haem
- Implantation
