Disorders of Growth and Differentiation Flashcards
What are the different kinds of growth ? Can growth be a mixture of these ?
A. Multiplicative growth (increased number of cells)
B. Auxetic growth (enlargement of an existing cell)
C. Accretionary growth (Growth of extracellular matrix)
Yes.
What are possible types of increased growth ?
A. Hyperplasia (increased growth in cell number)
B. Hypertrophy (increased growth in cell size)
What is physiological hypertrophy ?
Temporary increase in size of cells to provide for a natural increase of function.
Give examples of physiological hypertrophy.
Walls of the uterus
Athlete’s muscle
Give an example pathological hypertrophy.
in heart
Right ventricular hypertrophy (if something is reducing blood flow to the lungs and the body needs to compensate which enlarges size of cells in right ventricles)
Give examples of physiological hyperplasia.
Adaptation to altitude (high altitude training, increased number of RBCs in blood)
Mammae during pregnancy
Tissue repair (angiogenesis, wound healing)
Give examples of pathological hyperplasia.
Psoriasis (Abnormal epidermis, with lots of proliferation of cells, especially keratinocytes)
Tissue repair (keloid scar, scarring of liver in cirrhosis)
What is atrophy ?
Decrease in the number or volume of cell or both
may require apoptosis
What is one possible way for cells numbers to decrease ?
Apoptosis
Give examples of physiological atrophy ?
-Thymus gland, increases in size until age 10.
Later on in life, generation of T cells transfers more to bone marrow, and regression of thymus (loss of cortex and medulla).
-Ageing
What are examples of pathological atrophy ?
- Muscle – fractures (causes muscle wasting)
- Nerves - paraplegics (causes muscle wasting)
- Blood supply – circulatory problems (e.g. diabetic foot)
- Pressure – bedsores (loss of tissue)
- Diet - anorexia (loss of tissue)
What are possible causes of systematic growth disorders ?
- Hormones and growth factors
- Genetics
- Nutrition
- Environmental factors (pollution, housing, alcohol)
- Secondary consequence of disease (cystic fibrosis, kidney disorder)
What is Turner’s Syndrome ?
- Only 45 chromosomes, XO chromosomes (not XX or XY)
- Always female
- Short stature
What is the genetic basis of Turner’s Syndrome ?
- One copy of SHOX gene on each of X and X chromosome in females
- In affected individuals, only one X chromosome so half the number of copies of gene
- Protein encoded by the gene is a homeodomain protein, acting as a transcription factor
- SHOX is expressed in chondrocytes of the human growth plate (in hypertrophic zone of the cartilage plate)
- Without SHOX, not able to stimulate cells to increase in size so much
What is Beckwith-Wiedemann Syndrome ?
- Overgrowth in early childhood, especially large tongues