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Biomed investigation
| Question | Answer |
|---|---|
| What information do you get from a venous blood sample? | Information on prothtombin time and partial thromboplastin time, used to test clotting time, can be obtained from a venous blood sample. |
| What information do you get from an arterial blood sample? | Partial O2 and CO2 pressures can be obtained from an arterial blood sample. |
| What information do you get from an capillary blood sample? | Glucose analysis, blood group information tests and the Guthrie test can all be carried out using capillary blood. |
| What is total leucocyte count? | Total leucocyte count is the total number of white blood cells found in blood that has had all red blood cells removed. |
| What is differential leucocyte count? | A differential leucocyte count identifies the relative proportions of the different types of leucocytes. |
| What diseases are characterised by altered differential leucocyte count? | AIDS-Decreases helper T cells. Autoimmune Disease-Increased helper T cells. B cell leukemia-Increased B cells. T cell leukemia-Increased T cells. |
| What conditions increase total leucocyte count? | Total leucocyte count can be increased during and after acute and chronic infections, leukaemias, tissue necrosis, and also a result of normal situations such as exercise, child birth and menstruation. |
| What conditions decrease total leucocyte count? | Total leucocyte count can be decreased due to ionising radiation, some blood diseases, malaria, some drugs and prolonged rest. |
| How does an X ray work? | A low dose of X ray is passed through the area of the body under investigation. Any rays passing right through the body darken photographic film placed under the body. The image formed on the film depends on how many X-rays pass through the tissue. |
| Which tissues appear lighter on an X-ray and why? | As X-rays darken the film underneath the area to be investigated, areas where least X-rays hit the film appear lighter, because of this, bones, which absorb more of the X-rays than any other body tissue, appear brightest. |
| What is an advantage of ultrasound compared to X-ray? | Because ultrasound uses sound waves instead of the radiation that X-ray machines produce, they are much less harmful towards DNA. |
| What are the four steps of tissue biopsy sample preparation? | The four steps of tissue biopsy preparation are fixation, embedding, slicing and staining. |
| What is the purpose of the fixation steps? | Fixation is carried out to minimise the destruction of tissue by enzymes or bacteria, The biopsied material is placed in fixative which preserves the tissue morphological and molecular structure. |
| What is the purpose of the embeddment step? | Tissues are embedded in a substance that makes it rigid enough to be thinly sliced. |
| What is the purpose of the slicing step? | Small blocks of tissue, either frozen or embedded in plastic or paraffin, are sliced using a steel blade attached to a microtome and cut to a thickness of 1-12 micrometers, to obtain tissue sections that are thin enough to be viewed under a microscope. |
| What is the purpose of the staining step? | Staining of colourless tissues is carried out in order to observe them under a light microscope. Most common dye combination is haematoxylin and rosin. |
| What do you need to do if you need to examine a tissue sample quickly? How would you do this? | If you need to examine a tissue sample quickly, the tissue can be looked at in its native state. Instead of fixing and embedding, the tissue is hardened by freezing it and cut using a microtome that is kept at -20C. |
| What are the rules for examining infectious agents? | The general rules for sampling infectious agents are: Quantity of material must be adequate. Sample should be representative of infectious process (swab from death not surface). Avoid contaminating samples. Take sample before drugs given. |
| How does DNA hybridisation work? | DNA probes have been developed to identify specific micro-organisms. The probes are radiolabelled and specifically hybridise to complimentary DNA sequences in the sample. |
| How can you use DNA hybridisation to identify an infectious agent? | A specific probe for a pathogen is created with a fluorescent marker, when the probe meets complimentary DNA and forms a double helix with the pathogen DNA, the fluorescent marker allows the shape of the double helix to be examined. |
| What is a reference range and why is it necessary? | A reference range is the range of physiological variables in which 95% of the population will be deemed healthy. It is necessary to have a reference range so that comparisons can be made between a patients results and the range that would be expected. |
| What factors cause analytical variation? | The laboratory performing the test, including equipment. The personnel performing the test. The type of test being carried out. The laboratory conditions on the day of the experiment, i.e. temperature. |
| What factors introduce variability in diagnostics test results of one individual? | The posture of the person, whether or not the patient fasted before the exam and the time of day that the exam is carried out can all introduce variability in the diagnostic test results of one individual. |
| Define the term accuracy of a diagnostic test. | Accuracy defines how close the measured value is to the actual value, the mean of a set of repeated results will be close to the true value, even if the spread of results gathered is large. |
| Define the term precision of a diagnostic test. | Precision is a measure of the reproductability of an analytical method, a precise method has results spread much closer together than a non-precise one, even though the mean may not lie close to the actual value. |
| Describe the thyroid signalling pathway. | The thyroid signalling pathway, or HPT axis, starts with the release of thyroid releasing hormone (TRH) from the hypothalamus, TRH stimulates the pituitary gland, releasing thyroid stimulating hormone (TSH), TSH stimulates the thyroid hormone production. |
| How is the HPT axis deactivated? | The HPT axis is deactivated via a negative feedback loop, when the hypothalamus detects high levels of the T3 and T4 hormones produced by the thyroid, it stops secretion of TRH, eventually causing the whole pathway to stop. |
| Explain the thyroid signalling pathway in health and disease? | The thyroid gland produces the hormones triiodothyronine (T3), thyroxine (T4) and calcatonin, these hormones control homeostasis of body temperature, skin moisture and levels of oxygen, calcium and cholesterol |
| What causes Hashimoto's disease? | Hashimoto's disease is an autoimmune disorder affecting the thyroid gland, it may be caused by either a humeral attack by antibodies or a cell mediated attack. |
| What happens to thyroid hormones during Hashimoto's disease? | As antibodies are produced against the thyroid tissue, TSH receptors on the tissue surface, and the T4 binding thyroglobulin, production of thyroid hormones is reduced. |
| How is Hashimoto's disease treated and monitered? | Thyroxine tablets can be given orally starting at a low dose and gradually increasing the dose until plasma levels of thyroxine reach normal and become stable. Thyroxine therapy is monitered by measuring plasma levels of TSH2. |
| During thyroxine treatment, how often are thyroxine levels tested? | Thyroxine levels in the blood are tested every 6 weeks until normal steady state levels of thyroxine and TSH are achieved and there after test annually. |
| Why is the regular examination of thyroxine and TSH levels in the blood important during thyroxine treatment? | Regular check ups on the levels of thyroxine and TSH in the blood are important during thyroxine treatment as too much thyroxine or TSH can induce the symptoms of hyperthyroidism. |
Created by:
MushetJ
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