Abnormal Growth Flashcards
What are adaptations?
Cellular changes in response to changes in environment or demand (size, number, phenotype, metabolic activity, function).
REVERSIBLE
What is homeostasis?
Homeostasis is the ability to maintain a relatively stable internal state that persists despite changes in the world outside.
Are adaptations reversible?
Often reversible (compared with cell injury and neoplasia)
What can trigger an adaptation?
Reversible functional and structural responses to more severe physiologic stresses and some pathologic stimuli.
What is the result of an adaptation?
New but altered steady states are achieved, allowing the cell to survive and continue to function
What is hypertrophy?
Increase in SIZE of cells and eventually size of organ
What is hyperplasia?
Increase in NUMBER of cells caused by cell division
What causes hypertrophy?
Increased synthesis of structural components (proteins) caused by increase in functional demand (or hormones)
Where is hypertrophy particularly seen?
In permanent cell populations (very limited capacity for division) especially cardiac and skeletal muscle
What does hypertrophy lead to?
Increase in functional capacity and increased metabolism
What is the most common stimulant of hypertrophy for muscles?
Increased workload
Ability to adapt varies in different cell types. Why do fibroblasts not need to adapt?
Survive severe metabolic stress without harm. e.g absence of oxygen
Why can epithelial cells adapt easily?
- Labile cell population
- Active stem cell compartment
- Highly adaptive in number and function
Why can cerebral neurons not adapt?
- Terminally differentiated and permanent cell population
- Highly specialised function and easily damaged
Why is physiological adaptation?
Responding to normal changes in physiology or demand
What is pathological adaptation?
Responding to disease related changes
What are the 3 types of adaptive responses?
- Increased cellular activity (Increased size or number of cells)
- Decreased cellular activity (Decreased size or number of cells)
- Change of cell function and/or morphology
What is a good example of a hormone-induced increase in the size of an organ that results mainly from hypertrophy of muscle fibres?
The massive physiologic growth of the uterus during pregnancy
What stimulates cellular enlargement of the uterus?
Oestrogenic hormones acting on smooth muscle oestrogen receptors, eventually resulting in increased synthesis of smooth muscle proteins and an increase in cell size.
What causes the prostate to enlarge?
Ageing process –> by adenomyomatous hyperplasia
Detrusor muscle has to work harder during micturition and undergoes hypertrophy (trabeculated appearance)
How can the enlargement of the prostate affect the bladder?
Can lead to bladder outlet obstruction
Herniation of mucosa between the hyperplastic muscle trabeculae leading to the formation of a bladder diverticulum (prominent opening)
What are permanent cells?
Permanent cells are cells that are incapable of regeneration. These cells are considered to be terminally differentiated and non-proliferative in postnatal life.
What are examples of permanent cells?
Neurons, heart cells, skeletal muscle cells and red blood cells
How can hypertension lead to hypertrophy
Hypertension leads to increased peripheral resistance –> increases work required by left ventricle –> hypertrophy
The hypertrophy will compensate for some time, but if the hypertension is untreated the compensation may eventually fail.
Subcellular organelle may also undergo selective hypertrophy. What is an example of a drug that can stimulate this?
Barbiturates
What is the adaptive response of barbiturates?
Individuals treated with drugs such as barbiturates
show hypertrophy of the smooth endoplasmic reticulum (ER) in hepatocytes
What is the purpose of this adaptive response after treatment with barbiturates?
Increases the amount of enzymes (cytochrome P-450 mixed function oxidases)
available to detoxify the drugs.
N.B. after a while the patient will not respond as well to these drugs due to increased metabolism
What is non-dividing cell increased tissue mass due to?
Hypertrophy
What are the 2 types of hyperplasia?
- Physiological
2. Pathological
What can physiological hyperplasia be divided into?
Hormonal and compensatory
What is hormonal hyperplasia? What is an example?
Increases the functional capacity of a tissue when needed.
E.g. the proliferation of the glandular epithelium of the female breast at puberty and during pregnancy, usually accompanied by enlargement (hypertrophy) of the glandular epithelial cells
What is compensatory hyperplasia? What is an example?
Increases tissue mass after damage or partial resection.
E.g. capacity of the liver to regenerate
Where is hyperplasia possible?
In labile and stable cell populations
Can hyperplasia and hypertrophy occur together?
Hyperplasia and hypertrophy are distinct processes but frequently occur together.
Both can triggered by the same external stimulus.
What are most forms of pathological hyperplasia caused by?
Excesses of hormones or growth factors acting on target cells
What causes benign prostatic hyperplasia?
A common example of pathologic hyperplasia induced by responses to hormones, in this case, androgens
Where is hyperplasia seen in Grave’s disease?
An autoantibody binds to and switches on the TSH receptor in the thyroid, leading to prolonged, uncontrolled hyperplasia of the thyroid and hyperthyroidism (thyrotoxicosis).
What is atrophy?
Reduction in size of organ or tissue by decrease in cell size and number.
It can be physiological or pathological.
What can cause pathological atrophy?
- Decrease workload (disuse atrophy)
- Loss of innervation (denervation atrophy)
- Diminished blood supply
- Inadequate nutrition (e.g. cachexia)
- Loss of endocrine stimulation
- Pressure
What is an example of disuse atrophy?
When a fractured bone is immobilised in a plaster cast
What can cause denervation atrophy?
Damage to nerves
What type of atrophy can slowly developing arterial occlusive disease cause?
Diminished blood supply