1 Internal Surfaces Of The Body Flashcards
State the meaning of the term tissue.
A group of specialised cells from the same origin that perform a specific function.
State the relationship between milli, micro and nanometers.
Mili = 10-3m Micro= 10-6m Nano= 10-9m
Explain the value of histology in diagnosis.
Histology is the gold standard of diagnosis. It is used to check and give absolute proof of what doctors believe to be true often via a biopsy. A biopsy can also advise as to what treatment to give e.g. In the case of lung cancer.
Describe common biopsy techniques giving examples of tissues which can be sampled by each method.
Smear - swab of tissue is taken e.g. Cervix
Curette - a rigorous smear involving a spoon like tool. Used to take a biopsy of the uterus.
Needle e.g. Brain, breast, liver, kidney, muscle
Endoscopic - a camera with ‘jaws’ e.g. Lungs
Transvascular - X-ray guided via veins e.g. Heart
Explain why tissues need to be fixed and state which fixatives are commonly used.
Tissues are fixed using formaldehyde or glutaraldehyde. Fixing occurs to preserve the biopsy (as macromolecules develop cross links) and to prevent autolysis and putrefaction.
Describe how tissue processing can lead to the formation of shrinkage artefacts.
Tissue processing evolves continued dehydration and clearing by treatment with alcohol and the xylene/toluene, embedding in wax, the rehydration again through treatment of xylene/toluene and alcohol to be stained and the dehydration once more so it can be studied.
The overall loss of water leads to the shrinkage.
Discuss the value of histological staining and state the components of tissue stained by the periodic acid schiff reaction (PAS) and haematoxylin and eosin (H&E) staining.
Histological staining allows us to see clearly the components of cells/ tissues that we wish to observe.
Haematoxylin stains negative molecules/ acidic compounds such as DNA and RNA purple/blue. Eosin stains basic cell components pink e.g. Most cytoplasmic proteins and extra cellular fibres.
PAS stains carbohydrates and glycoproteins magenta.
Outline the advantages conferred by phase contrast, dark field. Fluorescence and confocal light microscopy
Phase contrast microscopy takes advantage of interference effects produced when two sets of waves combine. These are used to see details in living organisms.
Darkfield microscopy shins light from on side. The refractive and reflective properties of the section produce an image. Can be used on live and unstained biological samples. It almost entirely free of artefacts (structures that interfere with examination).
Fluorescence gives the image of only components given a fluorescent marker. This allows specific viewing of these components which is especially useful if there are dynamic.
Confocal light microscopy. One or more focused beams of light are shone across the specimen which often contains flourescent markers. This removes the disruption the flourescence causes of viewing other structures. It also creates optical sections, like individual ‘frames’ of sample, which allows it to be viewed in 3D as there are so many with the help of a computer.
