How to study histology: learn to read a slide, not to memorise pictures

The short answer

Study histology as learning to see, not as memorising pictures. For each tissue, learn the few features that identify it and what each one is for: the shape and layers of its cells, its nuclei, what lies between the cells and any special structures, such as cilia or striations. Then train your eye the way a slide exam tests it: look at many different images of each tissue, put look-alikes side by side, such as skeletal and cardiac muscle, mix tissues up instead of going through one chapter’s slides in a row, and name every image before you check, saying out loud the features that gave it away.

Spread that practice out, and keep earlier tissues in the mix while you learn new ones. Mixing categories helps people learn to tell them apart: medical students who practised reading ECGs with the categories mixed diagnosed new tracings correctly 46% of the time, against 30% for those who practised one category at a time (Hatala, Brooks & Norman, 2003). Drawing helps too: in a randomised study of 384 students, those who drew histological images remembered more than those who didn’t, still four and six weeks later (Balemans and colleagues, 2016).

Why histology is hard

A histology exam rarely shows you the picture from your book. The slide is cut at another angle, stained a little differently, seen at another magnification, and it may come from a different organ that happens to share the same tissue. A tube cut across looks nothing like the same tube cut along its length. So memorising pictures fails on the day: what carries over to a slide you’ve never seen is knowing the features that make a tissue what it is, and the habit of looking for them.

That’s a different kind of learning from remembering facts: it’s learning a category from its examples, as a doctor learns to read an X-ray. Nate Kornell and Robert Bjork (2008) had people learn painters’ styles from their paintings, either one artist’s paintings in a row or the artists mixed together. Mixing them was better for identifying new paintings by the same artists, yet the participants rated seeing one artist at a time as more effective, even after their own results had shown the opposite. Going through one chapter’s slides in a row feels like learning for the same reason that rereading does: it’s fluent. Roediger and Karpicke (2006) found that students who reread a text felt more confident than those who practised recalling it, but remembered less a week later, and a review by Dunlosky and colleagues (2013) rated practice testing and spreading study out as the most useful techniques, rereading and highlighting as of low use.

The method, a step at a time

Every organ is built from four basic tissues: epithelium, connective tissue, muscle and nervous tissue. Learn those well first, because the first question on any slide is which of them you are looking at, and where. Then study the organs a system at a time, as combinations of tissues you already know.

1. For each tissue, write its identifying features as a short list: the shape of its cells and how many layers they make, the shape and position of the nuclei, what lies between the cells, and special structures such as cilia, microvilli, goblet cells or striations.
2. Next to each feature, write what it’s for. Many layers where a surface is rubbed, as in the oesophagus and the skin; microvilli where the gut absorbs; cilia where mucus has to be moved, as in the trachea. A feature you can explain is one you’ll look for.
3. Look at many examples, not one: the textbook’s images, the atlas, virtual slides and the slides from your practical sessions, at low and high magnification and cut different ways.
4. Put look-alikes side by side and write down what tells them apart, as in the next section.
5. Test yourself on unlabelled images, mixed from different chapters: name each tissue or organ before you check, and say which features told you. A right answer with the wrong reasons counts as wrong.
6. Draw what you’ve seen from memory, a quick sketch with the key features labelled, then compare it with the image and correct it.
7. Describe a slide out loud in the order an examiner expects, as below, and come back to each tissue the next day and at growing gaps, mixing in the earlier ones every time.

Train your eye: many examples, look-alikes side by side

Mixing works because it makes you compare. Sean Kang and Harold Pashler (2012) repeated the paintings study and found that showing one artist’s paintings further apart in time, without mixing in other artists, did no better than showing them in a row, while showing paintings by different artists at the same time, side by side, worked as well as mixing them. What helps is the contrast between categories. In medicine the effect is the same: in the study by Rose Hatala, Lee Brooks and Geoffrey Norman (2003), medical students who practised ECGs with the categories mixed diagnosed new ones correctly 46% of the time, against 30% for those who practised one category at a time.

So make a page of look-alikes and learn them in pairs. Skeletal and cardiac muscle are both striated, but skeletal muscle fibres are long, unbranched and have many nuclei at the edge, while cardiac cells branch, have one or two nuclei in the centre and are joined by intercalated discs. Smooth muscle and dense regular connective tissue can both look like pink fibres: look at the nuclei, cigar-shaped and inside the cells in smooth muscle, flat and squeezed between bundles of collagen in a tendon. An artery has a thick muscular wall and a round lumen; the vein beside it has a thinner wall and a lumen often flattened or irregular. In the kidney’s cortex, the proximal tubules have a brush border and pinker cytoplasm, the distal tubules a clearer lumen and no brush border.

Vary the examples, too. Look at each tissue in more than one organ, cut across and along, at low and high magnification, and in more than one stain if your course uses others besides haematoxylin and eosin, in which nuclei stain blue to purple and most cytoplasm and collagen pink. Always start at low magnification: the overall layout of an organ, its layers and its lumen, often tells you more than any single cell.

Virtual slides, atlases and the microscope

Virtual microscopy, whole slides scanned so you can pan and zoom on a screen, lets you see far more examples than a few practical sessions. A meta-analysis by Anthony Wilson and colleagues (2016), pooling 12 studies, found a small but significant advantage in learners’ performance for virtual over optical microscopy, with high variation between studies, and learners preferred virtual slides by a large margin. Many universities publish their virtual slide collections free online, and your course may have its own.

If your exam is at a real microscope, practise with one before the day: finding the section, moving from low to high power, focusing, and finding a good field quickly. Recognising a tissue on a screen and finding it under the lens are not quite the same skill.

Use one atlas and one textbook, ideally those your course uses: Ross and Pawlina’s Histology: A Text and Atlas, Junqueira’s Basic Histology and Wheater’s Functional Histology are widely used. Use the atlas as a test, as you would in anatomy: cover the labels, name what you see, then check.

In Breef, you can keep a note for each tissue with images from your practical sessions or screenshots of virtual slides attached, its features and what they’re for written beside them, and “question :: answer” lines for the facts you need, such as “Which epithelium lines the trachea? :: Pseudostratified ciliated columnar, with goblet cells”. Each note comes back for review at growing gaps, with three questions written from it, and the cards can be exported to Anki.

Draw it, then describe it out loud

Drawing makes you look for the features rather than glance at the whole. In a randomised crossover study by Martijn Balemans and colleagues (2016), 384 medical and biomedical sciences students learned epithelia, and then heart muscle cells, either drawing histological images or not; on free-recall tests one, four and six weeks later, the drawing groups remembered significantly more. You don’t need to draw well: a sketch with the layers, the cell shapes and the key structures labelled is enough, made from memory first and then corrected against the image.

Describing a slide out loud is what most practical and oral exams ask for, and many want the reasons, not just the name. Practise a fixed order, so that nothing is left out under pressure: first what you see at low magnification, such as a hollow organ, a solid organ or a single tissue, and its overall layout; then the layers from the inside out, or from the surface down; then the cells and structures at high magnification; then what it is, with the features that prove it; and last, how its structure fits its function.

For example: “At low magnification this is a hollow organ with four layers. The lining is a stratified squamous epithelium, not keratinised, over a lamina propria and a thin muscularis mucosae; the submucosa has mucous glands, and the muscular layer has an inner circular and an outer longitudinal layer. A non-keratinised stratified squamous lining with glands in the submucosa makes this the oesophagus, lined to withstand the friction of food.” Practise with a classmate who picks images at random, and swap roles.

A plan for the weeks before the exam

Space your reviews from the start, and keep earlier tissues in every session. Cepeda and colleagues (2008), in a study of more than 1,350 people, found that the best gap between reviews grows with how long you need to remember: about 20 to 40% of the time until the test when that was a week, about 5 to 10% when it was a year. In practice: recall a tissue the next day, again a few days later, then about a week later and every week or two until the exam, sooner for what you confused. Breef can keep that schedule for you: give the course its exam date, and every note that would fade by then gets a last review in the days before.

If your course includes embryology, give it its own days in the plan: it’s learned as a sequence of events in time, better drawn as a timeline than recognised on slides.

1. Six weeks out: list every tissue and organ on the syllabus, and mark each by whether you can recognise it on an image you haven’t seen and say why, partly can, or can’t. Give the weakest the most days.
2. Weeks six to three: a group of tissues or an organ system a day, with the method above. Start each day with a mixed set of unlabelled images from the days before.
3. Week two: look-alikes and mixed sets only. If your course shares past exam slides, use them; if the exam is at a microscope, spend some of these days at one.
4. The last week: mock exams. A classmate picks slides at random and you identify and describe each one out loud, in the time your exam allows; look things up only to fix what you got wrong.
5. The day before: a light pass over the look-alikes you still confuse, and a full night’s sleep.

Common mistakes

Memorising the atlas’s pictures. The exam slide will be a different one: learn the features, and test yourself on images you haven’t seen.

Going through one chapter’s slides in a row and feeling sure. Mix the tissues up: it feels harder, and it’s what makes you able to tell them apart.

Naming a slide without saying why. Many examiners want the features that prove it, and a lucky guess won’t survive the next question.

Jumping straight to high magnification. Start low: the layout of an organ often gives it away before any cell does.

Learning structure without function. Knowing why a lining has many layers or cilia is what makes you look for them.

Leaving the microscope until the end. If the exam is at one, practise finding and focusing a field well before the day.