Topic: Skin

Target group

Students of the 7th grade of an elementary school.

Core curriculum

III. The human body.

2. Skin. Student:

1) presents the functions of the skin,

2) recognizes the elements of the skin structure (on the model, drawing, as described, etc.) and defines the relationship between the structure of these elements and the functions performed by the skin.

The general aim of education

The students describe the structure and function of the skin and show its sensitivity in experiments.

Criteria of success

• You will provide three examples proving that: o the skin protects against external factors, o the skin maintains contact with the surroundings;

• formulate a hypothesis for the problem and a conclusion based on experiments.

Key competences

• communication in foreign languages;

• communication in the mother tongue;

• mathematical competence and basic competences in science and technology; 

• learning to learn.

Methods / techniques

Problem strategy, methods: laboratory work, work with text, workshop - problem solving.

Individual work, work in groups.

Teaching aids

• abstract;

• interactive or traditional board;

• tablets/computers;

• rubber glove;

• bowl with hot water;

• indicator paper;

• coloured sheets.

Lesson plan overview (Process)

Introduction

1. The teacher asks the students to read the text:

„The skin is the largest organ of the body. It is a barrier that separates the body from the environment, and at the same time ensures contact with it. How does it happen that it can perform mutually exclusive functions?”

and look for three keywords. The teacher explains what are the keywords in relation to the analysed text.

2. The teacher informs that the students will solve two problems on this lesson:
   I. How does the skin protect against external factors?
   II. How and why does the skin provide contact with the surroundings?

3. The teacher gives the topic, the goals of the lesson in a language understandable for the student, and the criteria of success.

Realization

1. The teacher displays the skin structure diagram on the interactive whiteboard. The teacher asks the students to try to name skin elements. They can use the abstract and other sources (interactive map - Skin structure). The students sign the skin structure elements on the board.

2. The teacher asks which skin layer is responsible for collecting information from the environment, and which protects against external factors and asks for justification of the answer. When it is difficult for the students to find the right answer, the teacher asks one of the students to put on a rubber glove, and put his hand in hot water. The teacher explains that the glove is a model of the epidermis. The teacher asks the students to reconsider the question asked earlier. When the correct answer is given, the teacher divides the table vertically into two parts. On one, the teacher writes the problem: “How does the skin protect against external factors?”, and on the other: “How and why does the skin provide contact with the surroundings?” The teacher asks the students how to solve these problems. The students name the experiments, model experiments (as the one with the glove), search for information in sources.

Problem I.

3. The teacher divides the students into groups of 5‑6 people. The students formulate hypotheses. After consulting the teacher, the students write them on the board under the problem.

4. The students think how to verify the hypotheses. They can search in the e‑textbook and other online sources. Then, based on the replacement observation (images showing the skin structure) and the verbal text and the video recording „Exfoliation of the epidermis”, they write the conclusions on the board. The teacher pays the attention to the fact that they need to consider the relationship between the structure and function of tissues, and apply to both the epidermis, hair, nails, and the functions of the glands.

Problem II.

5. The students analyse the structure of the subcutaneous tissue, name the structures present therein, formulate hypotheses for the problem. Some groups perform experiment 1, other groups make observation 1. They can also check the sweat reaction with an indicator paper. The teacher explains that a slightly acidic reaction is not conducive to the development of pathogenic microorganisms. The students write their conclusions. The teacher pays attention to taking into account the relationship between tissue structure and function.

Summary

11. The students do interactive exercise 1.

12. Using coloured sheets, they assess the extent to which they have met the criteria of success.

Homework

Using different sources, look for information about melanoma. Prepare a short note and read it to your neighbour on the bench.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Skin

Skin consists of three layers of a different thickness – the epidermis, the dermis and the subcutaneous tissue. Epidermis is made of the epithelial tissue. Its tightly arranged cells create a barrier for bacteria, fungi and other harmful factors. The cells of the epidermis are arranged in layers. In the deepest part there is the reproductive layer, on the outside there is the horny layer of the skin. The cells of the reproductive layer divide all the time, and the newly formed generations of cells move outside and die over time. They are filled with keratin, protein that is impermeable to water and pathogens.

Dead epidermal cells constantly peel off, and microbes, sebum and dust are removed from the skin surface along with them. The thickness of the horny layer depends on its location. It is the thickest where it is more exposed to mechanical factors and greater friction, e.g. on the underside of the foot's surface.

Between the cells of the epidermis pigmented cells are located, which contain a brown dye – melanin. The greatest amount of this dye is found in indigenous people in environments where solar radiation is very intense. Its presence determines not only the colour of the skin, hair and eyes, but it also protects the genetic material of deeper cells against the harmful effects of UV radiation. However, complete skin isolation from sun is not recommended. Sunlight plays an important role in the synthesis of vitamin D3, which is responsible for calcium management of the body and a proper development of the skeletal system.

The dermis contains protein fibres that give it elasticity and mechanical strength. Numerous blood vessels supply skin cells with nutrients, discharge cell metabolism products and participate in processes of thermoregulation.

In this layer there are cells that receive the stimuli of pain, touch, pressure and temperature from the external environment. Their largest clusters are on the fingertips and on the lips. The subcutaneous layer is made of fat cells. Its thickness depends on the position in the body, the way of eating, lifestyle, gender. It protects deeply located tissues against mechanical injuries. It is also a thermal insulation layer, and a storage of chemical compounds.

Products of the epidermis are, among others, hair and nails. The hair consists of two parts: a shaft protruding above the skin surface and a root immersed in the subcutaneous tissue. The shaft is formed of dead cells filled with keratin and water. In the root there are reproductive cells responsible for the growth of the hair and dye cells. The hair root adheres to the hair erector muscle, which, when contracting, causes goose bumps and stiffening (putting up) of hair. Raised hair together with the layer of air between them reduce the loss of heat from the body. The hair covers the scalp most abundantly protecting it against heat loss and overheating.

On the outer surface of the fingers the epidermis produces hard plates – nails that protect the fingertips against injury.

Sebaceous glands occur in the close vicinity of the hair. Sebum that is produced by the glands contains fatty substances that protect the hair against drying and breaking, provide elasticity of the skin and prevent the penetration of pathogenic microorganisms into the body.

Sweat glands give off sweat, which mainly contains water. This, having high evaporation heat, rises from the surface of the skin and cools it. Sodium chloride present in the secretion of sweat glands gives the skin a salty taste. Along with sweat, some unnecessary metabolic products, such as uric acid, are removed from the body, which gives the skin an acid reaction. Thanks to this, some pathogenic microorganisms for which such an environment is unfriendly do not pose a threat to humans.

Mammary glands are activated in women after childbirth. Their secretion is milk containing protein, sugars and fats, immune substances, vitamins and other ingredients necessary for a proper growth and development of a child in the first months of life.

• The skin is the body’s coating.

• Cells of the external layer (epidermis) constantly exfoliate and help to remove dirt and pathogenic germs from the skin surface.

• Melanin contained in epidermal cells forms a natural protective filter against harmful UV radiation.

• Epidermis products – hair, nails and glands support the protective function of the skin