Disorders of Growth and Differentiation Flashcards
What is hyperplasia?
An increase in the number of cells
What is hypertrophy?
An increase in the size of cells
Name some examples of physiological hypertrophy and hyperplasia
Hypertrophy - Athletes muscles. Hyperplasia - the adaptation to high altitudes (increased number of RBC’s), increase in the number of cells in the mammary glands during pregnancy to produce milk.
Name some examples of pathological hypertrophy and hyperplasia
Hypertrophy - Right ventricular hypertrophy which can eventually lead to heart defects.
Hyperplasia - Psoriasis which is an autoimmune disease of the skin where cells are stimulated to proliferate.
Name some examples of hyperplasia in tissue repair
Angiogenesis (formation of new blood vessels). Wound healing (but too much leads to overgrowth of scar). Liver regeneration (too much proliferation leads to cirrhosis) and in the heart.
What is decreased growth and what does it involve?
It is atrophy and may involve the reduction in cell size or the number or cells or both! Can involve apoptosis,
Give examples of physiological atrophy
Atrophy in the thymus over life as it decreases in size and in ageing as you shrink in size with age.
Give examples of pathological atrophy
Disuse atrophy, paraplegics (nerves), circulatory problems can cause atrophy, pressure which can cause bedsores and diet which can cause anorexia.
What is Turner’s Syndrome?
A female genetic disease where they lack an X chromosome, this causes them to be short
Why does the genetic mutation in turner syndrome cause shortness?
This is due to the lack of the second SHOX gene. This gene escapes X-inactivation and you need both genes for normal height.
Where is SHOX expressed?
By chondrocytes in the hypertrophic zone of the growth plate. It works here by stimulating an increase in cell size.
What is beckwith-Wiedemann Syndrome?
Where two parental copies of a chromosome are inherited, causing increased expression of IGF-II and decreased expression of H19. Leads to overgrowth in early childhood
What is pituitary gigantism?
Increased IGF-I and increased growth hormone, often from pituitary tumours.
What is achondroplasia?
An inherited defect in FGFR3 gene (fibroblast growth factor receptor 3) which causes dwarfism. It is an autosomal dominant mutation.
How does the FGF receptor work?
Receptor tyrosine kinase - once FGF binds, the receptor dimorise, the TK domain becomes autophosphorylated activating it.
