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Development, Ageing + Repair (Disorders of Development (Congenital Disease…
Development, Ageing + Repair
Resolution
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If the liver is damaged every day, it will lose the ability to regenerate and go into repair mode. It will undergo fibrosis and cirrhosis.
Cells that can regenerate:
Hepatocytes (stable)
Pneumocytes
All blood cells
Gut epithelium (labile)
Skin epithelium (labile)
Osteocytes
Stem cells are found in:
Basal layer of epidermis - hair follicles + sebaceous glands
Intestinal mucosa - bottom of crypts
Hepatocytes
Bone marrow
Resolution: This is where the initiating factor is removed and the tissue is undamaged and able to regenerate
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Healing by 2nd intention
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Tissue loss, traumatic wound
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Repair
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Wound contraction can lead to stenosis, contracture (permanent shortening of muscle) and impaired mobility
Repair = initiating factor still present and there is replacement of damaged tissue by fibrous tissue
In the brain, fibrosis is called gliosis
Disorders of Development
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Being extremely tall can be caused by:
GH excess produced by pituitary adenoma
Mutation in COL2AI (type II collagen) gene
Mutation in fibroblast growth factor receptor 3 gene
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Hypertrophy = Increase in size of a tissue causes by increase in size of constituent cells e.g. ventricular hypertrophy
Hyperplasia = Increase in size of a tissue caused by an increase in the number of the constituent cells by mitosis e.g. hyperplasia of prostate
Atrophy = Decrease in size of tissue caused by a decrease in the number of constituent cells OR decrease in their size e.g. dementia, muscle atrophy from being in a cast
Metaplasia = Change in differentiation of a cell from one fully differentiated type to a different fully differentiated type e.g. ciliated columnar epithelium in bronchi changes to squamous epithelium in smokers. Squamous epithelium changes to columnar in Barrett's oesophagus due to acid
Dysplasia = Imprecise term for the morphological changes seen in cells in the progression to becoming cancer
Ageing
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Dividing cells have a limit due to telomeres. Telomeres get shorter every time the chromosome duplicates until the cell cannot divide any more
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Affects of aging
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Osteoporosis - weakening of bones, fracture risk
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Dementia - atrophy of brain tissue, neurones do not replicate
Sarcopenia - degenerative loss of skeletal muscle, decreased GH and testosterone
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Apoptosis + Necrosis
Apoptosis
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Bc12 protein, Fas receptor and Fas ligand all stimulate
caspases
Abnormal apoptosis:
Using angiotensin II inhibitor drugs for hypertension
Post bone marrow transplant
Parkinson's
Necrosis
Events: venom, frostbite, cerebral infarction, pancreatitis
Types of necrosis:
- Coagulative
- Liquifactive
- Caseous
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