Skin Cells

The skin cover the entire body and is our largest organ. It functions to protect the internal organs from mechanical, thermal, and chemical exposure as well as prevent evaporation of body liquids and of course also act as a barrier for pathogens. The outermost layer of the skin is called the epidermis. This layer varies in thickness depending on the location, but in general it is about 0.2 mm - 0.5 mm, or 200-500 microns thick. The epidermis can be subdivided into five (actually six) individual layers all made up mostly of skin cells, called keratinocytes. In fact 90-95% of the cells in the epidermis are keratinocytes.

You need a unique sample for your teaching lesson? Have a look into your rain gutter.

It’s real life: Sometimes the good things are closer than expected. Your rain gutter not only disposes the water from your roof, but also collects detritus from its colonizers such as mosses and lichens. It’s an extreme biotope: wet and cold in winter, even freezing, dry and hot in summertime. Only few microorganisms survive this extreme change.

One of them just recently came into spotlight. In April 2019 the Israeli space probe Beresheet* crashed onto the surface of the moon; 585kg of weight caused a small caldera. Aboard there were several thousands of Tardigrada, also known like Water Bears. As they had been transported in dried condition, and apparently no water seems to be available on the moon by fog or rain, the probability of life on the moon in 2020 still is quite low.

No need to travel so far to meet this astonishing group of animals. Take a sample of detritus from your rain gutter, if dry, first let it soak in rainwater. After a few days at room temperature it is time to check the water sample. Tardigrada may be fixed on the surface of moss leaves, so it makes sense to place a moss stem on the glass slide and to strip off the leaves by using two tweezers, one fixing the stem, one stripping off the leaves against the direction of growth.

A dead Tardigrada: Sectoral structure of body clearly visible.

Volvox bloom

Volvox is a popular alga among microscopists because of the beautiful images it produces under the microscope. The volvox in the video was unexpectedly found in a pool in Eindhoven, the Netherlands in early November 2019. There were so many of these species present that one could speak of a bloom.

The green alga Volvox is a colony of cells that have started to work together. Some cells catch the light, others provide movement or reproduction. They have become so dependent on each other that you can speak of a multicellular organism.

Colorful microscopic crystals

Vitamin C (ascorbic acid) | Motic BA310E 4X | Moticam Pro S5 Lite | © My Microscopic World

A crystal is a solid where the individual molecules are arranged in a highly ordered three-dimensional structure like we see in grains of sugar and table salt. This is compared to when a substance is dissolved in a liquid and all the individual molecules are floating randomly around. If a liquid with a crystallizable substance is left to evaporate. The individual molecules will rearrange themselves and get bound to one another in a crystalline structure. Depending on which substance it is, both the micro- and macroscopic crystal structure will vary greatly.

Found on cow parsley

Thrips (order Thysanoptera) are very small creatures that are almost invisible to the naked eye. Without magnifying glass they look like small black stripes on the leaf. Thrips is a very feared plague among growers. They are very difficult to control, even though the damage to the plant is not too bad. They are so feared because these insects have wings, so they can spread rapidly to other plants.