ANIMAL TISSUE

       Ø  Tissue: In the body of multi-cellular animals some cells remain together and performa particular function. These cells are either formed from the ectoderm, mesoderm or endoderm of the embryo and remain close together. Inter-cellular materials or matrix are present between these cells. These cells may be similar or of different types. Arising from the embryonic cell layer when certain types of cells when remain in a particular place of the animals' body and collectively perform a common function, those cells and the inter-cellular materials or matrix secreted by them are collectively called the Tissue. That is to say, cells of a particular tissue are similar in its, origin, function and structure. The subject in which the different types of tissue are discussed is called Histology.

      Ø  Differences between Tissue and Cell:

Tissue: Originating from a same place when more than one cell with similar structure and function performs a common function, then those groups of cells are called Tissue. For example, blood is a kind 'of fluid connective tissue. In the liquid matrix or plasma of blood there are red corpuscles, white corpuscles and platelets. Blood is developed from the mesoderm of the embryo.

Cell: Cell is the structural and functional unit of tissue. For example, Red blood corpuscles (Erythrocytes), White blood corpuscles (Leucocytes) and Platelets (Thrombocytes) are various types of blood cells. Of these the red courpuscles transport oxygen and carb.on dioxide, white corpuscles take part in the defense of the body and the platelets take part in blood clotting at the site of injury and stop unwanted blood loss. Blood cells and the plasma together form the blood tissue. Blood generally takes part in the internal transportation of the body.

      Ø  Types of Tissues :

On the basis of number of cells, characteristic and the presence or absence of the intercellular materials or matrix secreted by cells, the tissue is mainly divided into four categories.

1. The Epitherlial Tissue.

2. The Connective Tissue.

3. The Muscular Tissue.

4. The Nerve Tissue.

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General discussion of Cell division

Every living body is consist of cell. Some living bodies are made of only one cell. They are called unicellular organism, e.g. Bacteria, Ameba, Plasmodium, some Fungi and some Algae. Some living bodies are made of more than one cell. These are called multicellular organism. There are many living bodies, which are made of millions of cells. Living bodies like human, Beings or mango tree etc. are composed of millions of cells.

Unicellular organisms increase their number  by cell division. In this process one cell divides into two, two to four and so on.

In multicellular organisms, a large body consisting of millions of cells develops by cell division from the embryo, which also develops from a single fertilized egg. A young seedling developed to a large tree by cell division. Again new generation is created from male and female gametes formed by cell division.

But all these divisions are, not same. The processes of division are of different types and the results are also different. 

Ø Types of cell division: 

There are three types of Cell division:

1.  Amitosis

2.  Mitosis and

 3.  Meiosis. 

Ø Amitosis: In this division, at first the nuclear materials are directly splitted into two portions and then the cell divides into two from the middle region. As a result, from one cell there' develops two. This type of cell division occurs in unicellular prokaryotic organisms like Bacteria, Yeast etc. 

Ø Mitosis: Mitosis is a type of cell division by which a eukaryotic cell divides into two by a special method. In this process, the nucleus and chromosome are divided once and the number, structure and properties of chromosome in the newly formed cell remain just alike the mother. cell. Mitosis is also termed as equational division. Normally this division occurs in somatic cell. As a result of this division, the plantand animal increases in length and breadth. Mitosis occurs in all meristamatic cells of plants. 

ØMeiosis: Meiosis is a type of cell division by which a Eukaryotic cell divides into four cells by a special method. In this process the nucleus divides twice but the chromosome divides once. The number of chromosome in the newly formed daughter cell reduces to the half the number of mother cell. As the number of chromosome reduces to half this process is also termed as reduction division. In Greek `Meiosis' means `to reduce' and from this the term Meiosis comes in use. This division occurs in reproductive mother cells of diploid organisms. As a result haploid gametes develop. In haploid organisms, this. Division occurs in the zygote, as a result of which the organism becomes haploid again.

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Kind of cell

There are two kinds of cell on the basis of Nuclear Structure :

Ø  Prokaryotie cell : Nucleus is not well organized in these cells;nuclear membrane and nucleolus are absent here. In these cells Chromosomecontains only DNA. Generally no other organelles are present except Ribosome. Cell division happens here through Amitosis process.

Ø Eukaryotic cell: There are well-organised nucleus in these cells with membrane and nucleolus. Chromosome contains DNA, proteins Chloroplasts, Mitochondria and other organelles. Cell division happens throughmitosis process.

There are two kinds of cell on the basis of Function:

Ø  Somatic cell : These cells construct the living body but do not take part in reproduction. In the lower group of living objects they are haploid i.e. only one set of chromosomes are present, but in higher groups they are diploid i.e. there are two sets of chromosome in the nucleus.

Ø  Reproductive cell: These cells take part in sexual reproduction but do not construct the main body. These cells are also haploid. Sperm and ovum are examples of reproductive cell.

Size, shape and Structure of Living cell: It is normal to have some diversity in size, shape and structure of cells. The size, shape and structure of a eukaryotic cell (eucell) are described below in brief.

Ø Size : A cell may be 0.1 ì (micron) to 55cm (centimeter) or even more.[1 Millimeter = 1000 Micron]

Ø  Shape: Cells are of different shapes. Mainly they are spherical, oval, rectangular, barrel shaped or polygonal.

 Ø  Structure of typical cell :Structurally cells are of various types. For that in a certain cell all the organelles or structural ingredients may not be present. For that reason, considering the presence of all the organelles in a certain cell, it may be termed as a Generalized Cell. A generalized cell has mainly two parts- Cell wall and protoplasm.

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What is Cell

    Ø  Definition of cell:

Cell is the unit of structure and function of all living organisms .It is the smallest unit of organisms. Bacteria and some other organisms contain single cell. Major organisms contain hues cell.

Human contain 10 trillion cells.

The cell was discovered by Robert hook in 1665.

    Ø  Kinds of cell: There are mainly two kinds of cell;

1) Prokaryotic cell

2) Eukaryotic cell.

    Ø  Variation of human cell and plant cell: There are some important variation between human cell and plant cell. The main variation is there is an inert cell in a plant which has not in an animal.

    Ø  Specialty  of animal cell:

1) There is no any cell well.

Fig: Animal Cell 

2) There is no any plastid.

3) There is present centrism all time.

4) Some of lowest animal have central vacuole.

5) Golgi body seen by microscope.

6) Collected food of animal cell is mainly glycogen.

    Ø  Specialty  of plant cell:

1) There are present cell well which is made of cellulose.

2) There are present varieties kinds of plastid.

3) There is no centrism in plant cell.

4) There is present one more central vacuole.

 Fig: Plant cell

5) Golgi body seen by microscope rear.

6) Collected food of plant cell is starch.

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