PP: Cellular Adaptations Flashcards
What is autocrine signalling?
Signalling to self.
What is intracrine signalling?
Intracrine refers to a hormone that acts inside a cell, regulating intracellular events.
What is paracrine signalling?
Signally to adjacent cells.
What is endocrine signalling?
Signalling via he blood to reach a target cell.
What is the role of role of cyclins and CDKs within the cell cycle?
CDKs become active by binding to and
complexing with cyclins. Activated CDKs drive the cell cycle by
phosphorylating proteins. They are critical for progression of the cell to the next stage of the cell cycle.
What is the role of role of RB protein within the cell cycle?
The Rb protein is a tumor suppressor, which plays a pivotal role in the negative control of the cell cycle and in tumor progression. It has been shown that Rb protein (pRb) is responsible for a major G1 checkpoint, blocking S-phase entry and cell growth.
Define hyperplasia.
Increase in cell number above normal.
Which tissues can undergo hyperplasia?
It can only occur in labile or stable cell populations and it remains under physiological control and is reversible.
Give a physiological example of hyperplasia.
Physiological hyperplasia is either hormonal, when the
result is an increase in functional capacity, or compensatory, when there is
an increase in tissue mass after tissue damage.
Examples of physiological hyperplasia include increased bone marrow
production of erythrocytes in response to low oxygen and the proliferation
of the endometrium under the influence of oestrogen.
Give a pathological example of hyperplasia.
Examples of pathological hyperplasia include epidermal thickening in chronic
eczema or psoriasis and enlargement of the thyroid gland in response to
iodine deficiency
Define hypertrophy.
Increase in cellular size.
Which tissues can undergo hypertrophy?
Hypertrophy can occur in many tissues
but it is seen especially in permanent cell populations as these cell
populations have little or no replicative potential and so any increase in
organ size must occur via hypertrophy.
Give a physiological example of hypertrophy.
Examples of physiological hypertrophy include the skeletal muscle
hypertrophy of a bodybuilder and the smooth muscle hypertrophy of a
pregnant uterus (which also involves hyperplasia).
Give a pathological example of hypertrophy.
Examples of pathological hypertrophy include ventricular cardiac muscle
hypertrophy in response to systemic hypertension or valvular disease,
smooth muscle hypertrophy above an intestinal stenosis due to the extra
work of pushing the intestinal contents through the narrowing and bladder
smooth muscle hypertrophy with bladder obstruction due to an enlarged
prostate gland (which has undergone both hypertrophy and hyperplasia).
Define atrophy.
When cells become smaller.
Give a physiological example of atrophy.
Examples of physiological atrophy are ovarian atrophy in post-menopausal
women and the decrease in size of the uterus after giving birth.
Give a pathological example of atrophy.
Basically there are shit tons:
- Atrophy of disuse
- Denervation atrophy
- Inadequate blood supply
- Inadequate nutrition
- Loss of endocrine stimulation
- Senile atrophy (ageing)
- Pressure
- Toxic agents
Define metaplasia.
The reversible replacement of one adult differentiated cell type by
another of a different type.
Why does metaplasia occur?
The end result of
metaplasia is to change one cell type to another more suited to an altered
environment. It is seen most commonly in epithelial tissues and often in
columnar epithelium (fragile) which undergoes metaplasia to become
squamous epithelium (more resilient).
Give a pathological example of metaplasia.
Sometimes metaplasia is adaptive and useful. If the bone marrow is
destroyed by disease, splenic tissue undergoes metaplasia to bone marrow
(myeloid metaplasia).
Define reconstitution.
Reconstitution is different to regeneration in that it is the replacement of a
lost part of the body. It requires the coordinated regeneration of several
types of cells. Examples include the regrowth of a lizard’s tail and the
growth of deer antler.
Define aplasia.
the complete failure of a specific tissue or organ to develop. It is an embryonic developmental disorder.
Define involution.
A term which overlaps with atrophy
Define hypoplasia.
The congenital underdevelopment or incomplete
development of a tissue or organ. There are an inadequate number
of cells within the tissue which is present.
Define atresia.
‘No orifice’, the congenital imperforation of an opening,
e.g., atresia of the anus or vagina.
Define Dysplasia.
The abnormal maturation of cells within a tissue. It is
potentially reversible but is often a pre-cancerous condition
Define regeneration.
When cells multiply to replace loses.
