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Growth abnormalities
Organisation of the Body
| Question | Answer |
|---|---|
| Decreased growth | Developmental Progressive |
| Increased growth | Hypertrophy Hyperplasia Neoplasia |
| Agenesis | Complete failure of structures to develop E.g. renal or pulmonary agenesis |
| Hypoplasia | Partial failure of structures to develop E.g. testes in Klinefelter's syndrome (47,XXY) Ovaries in Turner's syndrome (45,X) |
| Unilateral pulmonary Agenesis | Developmental lack of one lung The other lung will increase in size to compensate for the lack of function Can be asymptomatic |
| Renal hypoplasia | Incomplete development of the one kidney The other kidney is larger that normal to allow for normal functioning 1 in 750 live births Often asymptomatic |
| Progressive decreased growth | Physiological e.g. involution of thymus at puberty Pathological e.g. general (cachexia due to malignancy) or local atrophy |
| Involution of the thymus | Structures of the thymus change overtime As you age the cortex and medulla are gradually replaced by fat. This reduces the ability to produce mature T-cells, meaning the immune system weakens Studied by looking at conc of immature thymocytes |
| Cachexia | Weight loss in patients with advanced pancreatic cancer Gradual loss of body weight due to inflammatory responses to the tumour A characteristic feature of pancreatic cancer - 85% of patients report having lost weight |
| What is local atrophy due to | Disuse e.g. muscle and bone of a limb in a cast Pressure from a cyst, tumour or aneurysm Ischaemia - lack of blood supply due to vascular disease Neuropathy - nerve damage e.g. polio Idiopathy - unknown cause e.g. brain atrophy in Parkinsons |
| Increased growth - hypertrophy and hyperplasia | Increase in tissue/organ size by increased cell size (hypertrophy) or increased cell number (hyperplasia) Response to external stimulus Histology is often normal Often provides extra function Usually self limiting; often reversible |
| Hypertrophy | Characteristic of permanent tissue (normally muscle) Increase in cell size without increase in cell number E.g. skeletal muscle in response to exercise - cells get larger but do not divide |
| Hypertrophy in diseased tissue | Myocardial hypertrophy - increase in cardiac muscle volume May be an adaptive response to pressure or volume stress Underlying genetic cause in some cases - when not associated with vascular disease Elevated risk of arrhythmia and sudden cardiac death |
| Hyperplasia | Typical of renewing tissues Increase in cell number while maintaining mean cell size (balanced growth) E.g. liver regeneration after partial resection Increased erythropoiesis at high altitude |
| Hyperplasia in diseased tissue | Normal thyroid has thin layers of epithelium In Grave's disease these epithelia are tiggered to divide by auto-immune antibodies against the TSH receptor This causes the lumen to be squashed and increases hormone secretion - hyperthyroidism |
| Increased growth - neoplasia | Excessive proliferation of one cell type Results from cumulative genetic and epigenetic changes A clone results from a single progenitor Abnormal, unbalanced histology No useful function Progressive - spontaneous regression is rare |
| Main benign tumour types | Epithelial surface - papilloma Epithelial glands - adenoma Mesenchymal - Fibroma, lipoma, haemangioma Haematological lymphoid - lymphoproliferative disorders Haematological bone marrow - myelodysplasia |
| Main malignant tumour types | Epithelial surface - carcinoma Epithelial glands - adenocarcinoma Mesenchymal - fibrosarcoma etc Haematological lymphoid - lymphoma Haematological bone marrow - leukaemia |
| Neoplasia - benign papilloma | Cells are normally shed from epithelia - these are not shed leading to a build up of differentiated cells Relatively normal differentiation but too many cells present |
| Neoplasia - benign adenoma | Colorectal adenoma-inherited mutation in APC tumour suppressor triggered by random mutation of the second allele Tumour has a complex structure broadly similar to normal epithelium Blood is present in the tumour but not normal tissue |
| Benign tumours | Grow by local expansion Do not invade adjacent tissue, transverse basement membrane or spread to distant sites Differentiation usually resembles the normal tissue May cause harm through pressure, obstruction or hormones May lead to malignancy |
| Neoplasia - malignant carcinoma | Does not look like the adjacent normal tissue - disordered differentiation Large nuclei - lots of mitosis Darker stained - more metabolically active Cells show many differentiation sites - pleomorphism |
| Adenocarcinoma of the colon | Lack of differentiated structures Accumulation of inflammatory cells (darker staining) attracted to the tumour - leads to the cachexia Wide variety of differentiation states - pleomorphism Tumour invades muscle boundary - can spread Blood in tumour |
| Malignant tumours | Grow by invasion on adjacent tissue, transverse basement membrane and spread to adjacent sites Differentiation incomplete and shows pleomorphism/anaplasia Large nuclei - aneuploid- mitotic abnormalities Cause harm through destruction of normal function |
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