The science of the cells is called cytology. It is a young science which originated only in the 19th century. Since thas time more advanced microscopes and other devices have been built with which the cells and tissues can be examined more carefully.

In multicellular living beings the size, the structure and the form of cells have are different because cells perform different functions. If one compares all cell kinds, one finds the same components. These are the nucleus and the cytoplasm. They are the living substance of the cells.

The nucleus is very important because it leads metabolism and the division of the cell.

Metabolism takes place in the cytoplasm. The cytoplasm consists primarily of the cell membrane, the basic plasma and the organelles.

The cell membrane surrounds the cell and can transport materials from the surrounding to the cell and from the cell back to the surrounding. Other membranes divide the cell into different parts with different functions. All membranes are built up primarily from protein.

The basic plasma is situated between the organelles. The movement of the materials takes place in the basic plasma during metabolism. It is not hard. The basic plasma is a mixture which consists primarily of water, protein, fat, carbohydrate and gases (oxygen and carbon dioxide). Protein is the most important because life is impossible without protein.

The organelles are components of the cytoplasm which differ by their functions. Examples: the mitochondria serve for the respiration, the ribosome build up protein. There are mitochondria and ribosome in all cells. The centrosome is found only in the animal cells. It participates in the cell division. Chloroplasts are only in green herbal cells. They are important for the photosynthesis. In many herbal cells the basic plasma also surrounds vacuole which contains the enchylema.

2.1 Animal cell (a) аnd plant cell (b)

Most herbal cells have a thick cell wall around the thin cell membrane. It consists primarily of cellulose. It is hard and gives the shape to the cell.

The cells of the plants differ from the cells of the animals. The animal cells are similar to the human cells. The cells are small living units, because the cell components work together.

1. Answer the questions using the information from the text:

1. What do all cells consist of?

2. Which three components is the cytoplasm divided into?

3. Which chemical materials does the basic plasma contain?

4. Which functions does the nucleus perform?              

2. Distinguish important concepts

Cell membrane – cell wall

Use: plant cell, animal cell: surround, consist of; protein, cellulose: thick, thin

Organ – organelle

Note the explanations of the concepts which you read in the text.

Carbon dioxide – carbohydrate

Carbon dioxide (CО2) is a gas which is delivered by the lungs.

A carbohydrate is C_n(H₂O)_m. This is a sugar which is contained in different fruits.

3. Complete the gaps in the text with the following words: protein, fat, carbohydrate, carbon dioxide, oxygen, water

The living cells need different materials for metabolism. If we breathe, we take air from the environment. Our organism gets …. … … … from butter,  … … …. from rice, … … … … from meat and … …. from tea, coffee, milk and wine. These and other materials are brought to the cells. During metabolism the mitochondria carry out the respiration of the cell and form, besides, … … … … which is delivered later in the lungs. The ribosomes form for the cells their own … … ….

The tissues of organism originate from division, growth and development of cells.

With humans and animals four main groups of tissues can be distinguished: epithelum tissue, connective tissue and supporting tissue, muscular tissue and nervous tissue.

Epithelial tissues cover the body and form internal and external surfaces.

Connective tissues and supporting tissues connect the organs or support them.

Muscular tissues serve for the movement of the body or its parts.

Nervous tissue serves for the processing of the signal from irritators.

Epithelial tissue

Epithelial tissues are mostly thin tissues without intercellular substance. Epithelium can be divided into surface epithelium, glandular epithelium and sensory epithelium.

Surface epithelium covers the surface of the body. The multilayer surface epithelium is the external layer of our skin. It protects the body from bacteria and too big water loss. Monolayer surface epithelium is located, e.g., in the heart and in the lungs. It takes up dissolved materials and delivers them to other tissues.

Glandular epithelium is in the glands. It forms secretions. The secretion of glandular epithelium in nose and in bowel is called mucus.

Sensory epithelium is in the senses organs (e.g., eye, nose, ear) and serves for the perception of irritants from the environment of the living being.

a

b

2.2 Epithelium

a - monolayer surface epithelium, b - multilayer surface epithelium

Connective and supporting tissues

All connective and supporting tissues originate from a tissue type – the connective tissues of the embryo. They develop to different tissues which connect the organs, support or protect.

Fatty tissue has many cells, i.e. it is rich in cells and poor in intercellular substance. Every cell of the tissue is filled with fat. Therefore, the cytoplasm and the nucleus lie only in the cell membrane. As the fatty tissue is soft, it serves as a protection against big pressure. It also protects the body against too big loss of heat. It is located between the organs and in the skin.

Loose connective tissues and the taut connective tissues have many fibrils in the intercellular substance. In loose connective tissues the fibrils lie loosely, it is elastic. It surrounds the organs and connects them. Moreover, it is also found in skin. In taut connective tissues, on the contrary, fibrils lie tightly, it is inelastic. It forms tendons which connect bones with muscles. Cartilaginous tissues and bone tissues are especially rich in intercellular substance. Cartilaginous tissue has cells which aren’t connected. Intercellular substance is elastic, therefore, the whole cartilaginous tissue is elastic. It serves as a protection against too big pressure. It forms the cartilages which are in nose, ear and also at the end of many bones.

2.3 Сonnective tissues

a - fatty tissue, b - cartilaginous tissue, c - bone tissue

1- intercellular substance; 2 - cells

Bone tissue consists of cells which are connected with cytoplasmic membrane. These are necessary for the metabolism of cells. The intercellular substance consists primarily of calcium salts which give the firmness to bones. Bone tissue is located in the bone. With old people and animals the amount of the calcium salts grows in intercellular substance, the bones thereby become inelastic and break easier.

Muscular tissue

Muscular tissues can contract. This is possible because their cytoplasm consists of parallel recumbent fibrils, which can contract.

Muscular tissues are divided into two types: cross-striped and smooth muscular tissue. Smooth muscular tissue consists of cells, and cross-striped tissue of longer and thicker fibres which have appeared from several cells during the development.

The thick and long fibres of the cross-striped muscular tissue contain fibrils from two different proteins, so that it can be seen as crosswise recumbent stripes with the help of the microscope in muscle fibre.

2.4 Muscular tissue

a - Cells of smooth muscular tissue

b - Fibres of cross-striped muscular tissue

In smooth muscular tissue the fibrils consist only of protein, so that these cells look smooth in the microscopic picture.

Moreover, the fibres of cross-striped muscular tissue have several cell nuclei in the membrane, but the smooth muscle cells have only one nucleus which is situated in the middle of the cell.

Cross-striped muscular tissue forms the muscles in bones. Smooth muscular tissue can be found, e.g., in stomach and in bowel. Heart primarily consists of the third kind of the muscular tissues.

If the muscle gets stimulation from the nervous tissue, the fibrils contract (become shorter), and thereby the muscular tissue contracts itself. The muscle thereby moves the organ or the body part. After the contraction the muscle grows tired, i.e. he becomes long and soft and then is in rest.

The muscles in the bone can work fast or slowly, with a lot or with little strength, as we want it. Other muscles work mostly evenly and do not become tired. We have almost no influence on their work.

Nervous tissue

Nervous tissue serves for the management and processing of the information taken from the environment. This is possible due to its special construction.

2.5 Nervous tissue

       The nerve cells seem are primarily located in the brain and in the spinal cord. They mostly have many short processes and a long process. The short processes of nerve cells are connected with many other nerve cells (e.g., in the brain). The long processes begin in a sensory cell and end in nerve cell, or they begin in her nerve cell and end in a muscle or in a gland. Several long processes which run in parallel form a nerve.

       The environment of the living beings changes constantly, that’s why every living being can live only if it can ascertain these changes and react to them. Animals and humans take percieve slightest irritators with the help of the sensory cells in eyes, chemical irritators with the help of the sensory cells in nose and temperature irritators by sensory cells in skin. Stumilation originates in the sensory cells from the irritators.

       Stimulation is fast escorted by the nerves. Information is processed in the nerve cells of the brain; i.e. they are compared to stored information, are stored themselves, and the body answer is formed.

       From the nerve cells stimulation reaches the certain organs which work then: muscles move body parts, glands deliver secretions. The movement or the delivery of secretions are examples of reactions of the organism to irritators.

1. Answer the questions using the information from the text:

1. Which main groups of the human and animal tissues are distinguished?

2. Which function does nervous tissue perform?

3. Which connective and supporting tissues are distinguished in the text?

4. Which tissue has many cells?

5. Which tissues are rich in intercellular substance?

6. Where do the cytoplasm and the nucleus of a fat cell lie?

7. Where is loose connective tissue located?

8. Which functions does the fatty tissue have?

9. Which parts of the muscle cells or muscle fibres carry out the contractions?

10. What are fibrils? Where are they located?

11. Where is smooth muscular tissue located?

12. How is the muscular tissue changed by the contraction?

13. On which muscles do we have influence?

14. To which irritants of the environment do animals and people react? Give examples!

15. Where are the nerve cells located?

16. Which processes take place in the brain?

17. What is a nerve? What does it do?

18. Where do nerves begin? Where do they end?

2. Describe the construction of different cells:

The animal cell, the herbal cell, the fat cell, the bone cell, the cross-striped muscle fibre

3. Compare different cells and different tissues:

- the structure of the herbal and animal cell

- the structure smooth and cross-striped muscular tissue

- the structure and the functions of cartilaginous and bone tissue

4. Define concepts from the area: doctrine of cell and tissue:

Mitochondria, ribosome, fibrils, tissues, intercellular substance, nerve

5. Complete the gaps with the first the names of the tissues:

The tissues of skin

A job of skin is to cover the body outside. Therefore, the upper layer of the skin, the epiderm, consists of … … …. tissues. It is a thin layer which contains no blood vessels. The body must be protected against injurious environmental factors, that’s why the epiderm consists of several cell layers. It is ……….

The middle skin layer connects tightly the upper and lower layer. This is … tissue. In the middle skin layer one recognises in the microscopic picture many glands it consists of. Moreover, many cells there for the irritant admission belong to ………………

They are connected by nerves with the brain and spinal cord which are formed from … … …. tissue. The blood in the blood vessels carries the necessary materials.