Histology, microscopy, anatomy and disease
Histology, microscopy, anatomy and disease

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Histology, microscopy, anatomy and disease

3.3 Put it into practice

In the next activity, you are invited to investigate, identify and comment on two slides drawing on what you’ve learned.

When reporting on sections it is important to clearly distinguish observations and interpretations. You might want to make a short written report on these two sections, before responding to the questions. Then compare your observations and conclusions with the answers.

Activity 6

Slide 19

Open the virtual microscope [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] in a new window or tab. Find Slides 19 and 20 in the ‘Week 4’ category.

Look at Slide 19. Identify:

  • the tissue shown in Slide 19
  • whether the section is normal or abnormal.
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Interactive feature not available in single page view (see it in standard view).

Discussion

The tissue shown in Slide 19 is from a lung and it is not normal. You can compare this section with Slide 6 from Week 2, which is from a normal lung. In particular, the area near the upper right of the section (8000, 4000), does not look like the normal tissue. Navigate to these coordinates in the Virtual Microscope to see them for yourself.

Now try to identify what kind of pathological reaction can be seen in the tissue on this slide. What might cause this type of change?

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Answer

The section of lung shows areas of low grade inflammation (8480, 2904) with some thickening of the walls of the alveoli (7285, 2903).

This biopsy came from a patient with cytomegalovirus infection. Some macrophages (6637, 1215) in the alveoli have dark-staining intra-nuclear inclusions (6475, 802). Although the virus itself cannot be seen with the light microscope, its appearance on infected cells is characteristic. Navigate to these coordinates to make sure that you can identify these features.

You would probably not be able to identify the type of infection from the histology alone. However, you might have worked out that an infectious agent is one likely cause of inflammation in the lung.

Slide 20

Look at Slide 20. Identify:

  • the tissue shown in Slide 20
  • whether the section is normal or abnormal.
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Interactive feature not available in single page view (see it in standard view).

Discussion

The tissue shown in Slide 20 is from a thyroid and it is not normal. You can compare this section with Slide 1 from Week 3, which comes from a normal thyroid. Slide 20 comes from a patient with a goitre, i.e. an enlarged thyroid. The changes are seen throughout the section.

Compare Slide 20 with Slide 1 from Week 3. Make notes about:

  • what type of reaction you can see in the tissue on this slide
  • what might have caused this type of change, which has resulted in enlargement of the thyroid.
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Answer

The tissue shows hyperplasia of the thyroid, which is typically produced by a lack of iodine in the diet and/or abnormally high production of thyroid-stimulating hormone (TSH) by the pituitary.

The thyroid epithelial cells are dense and form clumps within the acini (2421, 3842), but the overall anatomy appears normal, so there is no evidence that the cells are neoplastic. Moreover, hyperplasia has occurred throughout the gland.

Neoplasia generally arises in one area of a tissue (due to gene mutation in one cell or group of cells), and there is usually some relatively normal tissue still present, which may have been included in the histological section. Notice also that the acini in Slide 20 have scalloped edges in some places, caused by the active removal of stored colloid to release the thyroid hormones.

All of these observations indicate hyperplasia, rather than neoplasia. This section illustrates how understanding the normal function of a tissue can shed light on the histological changes that have occurred.

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