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The LiVing CEllS

Biologist have classified, living organism into single-celled and many-celled, organisms. Bacteria, amoebae and many of the small animals and plants are single-celled, while insects, fish, and most of the larger organisms are many-celled. Intracellular processes form the basis of life of all multicellular organisms.

In almost all multicellular organisms (plants and animals) the individual cells have the work divided up among them: each cell specializes in certain functions.

This leads to thy development of groups of cells, sometimes compact as in muscle, sometimes diffuse as in the blood cells. Each of these groups together with the intercellular substance is called a tissue, and one or more of these tissues are arranged to form organs. Thus, nervous, muscular, epithelial and connective tissues are combined to form the heart. Cells possess all the principal characteristics of life – they eat drink, digest food, curry away wastes, grow, mul­tiply and respond to stimuli.

For many years, the structure of cell was thought to be relatively simple. The cell was believed to be a mass of protoplasm enclosed in a membrane and containing a nucleus, very small granules, fibres and other cytoplasmic organoids and inclusions. But the electrone microscope changed our ideas (concepts) about the structure of the living cell. We were able to observe numerous membranes usually consisting of two layers of molecules of one type with one or two layers of molecules of another type between them. A number of new organoids performing vitally important functions have been discovered. Various parts of the cell were found to be connect­ed with one another by endless numbers of previously invi­sible canals, the walls of which, are made up of one or two layers of large molecules. By means of these canals the cell nucleus is connected with the multi-membraneous structures of the cytoplasm.

The protoplasm of cells contains proteins, nucleus acids, fats, carbohydrates, vitamins, pigments, salts, and water. As to its activities, the cell may be compared to an automatic factory where different departments perform different functions but operate as a single unit producing only one thing – life. And life, as Engels once defined it, is a mode of existence of protein bodies.

Translate the following words with the suffixes multi-, inter-, intra-.

multi (много):

multicellular, multimembraneous, multicoloured, multinational;

inter (меж-, между-):

intercellular, international, interaction, interstinal;

intra (внутри-):

intramuscular, intravenous, intramolecilar, intracellular.

Memorize the plural forms of the following nouns of foreign origin.

Change the following underlined nouns into plural forms.

1. A (bacterium) produces spores. 2. A (stimulus) can be physical, chemical or electrical in nature. 3.The (nucleus), situated in the centre of the cell, is spherical. 4. A (vertebra) consists of a body and an arch (дуга). 5. An (amoeba) reproduces by simple division. 6. A (Fungus) enters the animal body through food and water.

Give English equivalents of the following words and word combinations.

это приводит к развитию, кровяная клетка, живые организмы, электронный микроскоп, однокле-точный, межклеточное вещество, способ существования, многоклеточный, мышечная ткань, вну-триклеточные процессы, определенная функция, многоклеточные организмы, масса протоплазмы, жизненно важная функция, невидимый канал, относительно простое вещество, посредством.

Find in the text English equivalents of the Russian sentences.

1. Структура клетки, как раньше считали, была относительно простой. 2. Каждая клетка выполняет определенную функцию. 3. Электронный микроскоп изменил наше представление о строении живой клетки. 4. Протоплазма клетки содержит белки, жиры, углеводы, витамины, соли и воду. 5. В живой клетке существует более 100000 химических веществ. 6. Жизнь – это способ существования белковых тел.

Answer the following questions.

1. What is single-celled (many-celled) organism? 2. What single-celled (many-celled) organisms do you know? 3. What is tissue? 4. What characteristics of life do cells possess? 5. What do you know of the structure of living cell? 6. What does the protoplasm of cell contain?

Lesson 2. Tissues

Word List А

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TISSUES

There are four major groups of tissues: epithelial tissues, connective tissues, muscle tissues and nerve tissues.

Epithelial tissues. This tissue has the shape of cellular membranes which cover the surface and the internal caviti­es of the body.

Morphologically epithelia are classified according to the shape of the cells, and their arrangement. According to the shape of the cells, there are flat, columnar, cubical epithelia. According to arrangement of the cells there are simple and stratified epithelia.

Connective tissues. They are subdivided, into trophic tissues and supporting tissues.

There are two categories of connective tissues: the connective tissues (fibrous tissues concerned primarily with connecting one part of the body to another) and the supporting connective tissues (cartilage and bone). Unlike epithelium, the various connective tissues are characterized by the enormous development of the intercellular substance.

Muscle. Muscle tissue is differentiated into three types: smooth (or visceral), skeletal (or striated), and cardiac. The shape of smooth muscle varies according, to the organ containing the muscle; for example, very long and slender in the walls of the intestine, or short and thick in the walls of small arteries.

Smooth muscle is not is richly supplied with blood vessels as skeletal or cardiac muscle.

Skeletal muscle in attached to the skeleton. The at­tachment may be by a thin layer of periosteum or by longer cords the tendons.

Skeletal muscle tissue forms the "flesh" of the body. Cardiac muscle tissue composes the wall of the heart and resembles skeletal muscle in structure. Its action, however is involuntary.

Nerve tissues. This tissue functions to conduct nerve impulses. Each nerve cell or neuron consists of an enlarged portion, the cell body, from which two or more fibres extend. These fibres are of two types: dendrites which conduct impulses toward the cell body, and exons, which conduct impulses away from the cell body. Neurons occur in many sizes and shapes.