Biology Notes on Plant and Animal Tissues
Tissue is a group of structurally similar cells performing a specific function.eg- blood, muscles, xylem, phloem, etc.
plants are made up of mostly dead tissues. They provides strength and support to the plant.
on the basis of the structure and function plant tissues can be categorized as -
Meristematic TissuesThese Tissues are a group of actively dividing cells, which remain in continuous state of division throughout their life.
These tissues are generally found in growing parts of the plants like sepal and stigma of flower, apex of root, receptacles axis of stem, etc.
Permanent TissuesThese are the tissues made up of non-dividing mature cells. Meristematic Tissues when lose the ability to divide(cell-division) transform to permanent tissues. The permanent tissue may be dead or living, thick or thin cellular wall.
These tissues can be classified as -
Protective TissuesThis tissues found at the surface of the root, steam and leaves. It is made up of thick cell that protect underlying tissues in plant body.
Supportive TissuesThese tissues made up of similar type of cells, which have common origin and function.The main work of these type of tissue is to provide support to the plant. these are mainly three -
Parenchyma :- These tissues are made up of large and thin cell wall. cells, equally expand on all sides with intercellular space among them, which allows the exchange of gases.
These tissues are made up of living cells of oval, round, polygon or elongated shape. It is found in mesophyll tissues of leaves, pulp of the fruits, endoderm of seeds. These tissue cells also store the food stuff in the protoplasm of the cells as in potato. The main function of these tissues are to provide temporary support to the plant.
Collenchyma :- These are the tissues made up of living cell which are elongated and the cell wall is thickened at the corners. It is the basically a mechanicnical tissue which provides mechanical support and elasticity to the plants. It is found in outer region of cortex. eg- angles of stems, midrib of leaves, etc.
Sclerenchyma :- These tissues composed of long, narrow cells which have became dead. Cell wall of such cell are greatly thickened due to lignin or cellulose or both. It gives mechanical strength, support and rigidity to the plant body. These are found in the components of hard coating of several seeds and nuts, eg- husk of a coconut.
Conducting TissuesThese are the permanent tissue, composed of more than one type of cell working together. These are mainly two types -
Xylem :- Xylem consists of dead cell hollow cell(wood) in the form of fibers and sclereids, cell are elongated and thick-walled. Its main function is to provide mechanical strength and rigidity to the plant. It is the chief conducting tissue of vascular plants responsible for the conduction of water and dissolved material from roots to the apical part of the plant.
Annular rings formed in tree are made up if xylem. Number of rings indicate the age of the Tree.
Phloem :- It is the chief conducting tissue of vascular plants. They provide a passage for the downward movement of manufactured foods in the leaves. Phloem consists of sieve tubes, companion cells, phloem parenchyma and phloem fibres.
Animal TissuesAnimal tissues consist of similar cell of common embryonic origin and function. All animals consist of four basic type of tissues. They are -
Epithelial TissuesIt is composed of one or more layers of closely packed cells covering the external surface of the body and lining of the body organ including blood vessels. eg- skin, lining of mouth, lining of blood vessels, kidney tubules, etc.
It helps in the absorption of water and nutrients. It protects the underlying cells from injury, drying, infection and also from harmful effects of chemicals. It also help in the elimination of waste products from the body.
Connective TissuesThese tissues link and support other tissues or organ of the body. These are most abundant and widely distributed in the body of complex animals. The cells of connective tissues are loosely packed, living, embedded in an intercellular matrix. The matrix may be jelly-like fluid, dense or rigid nature.
These tissues attach one tissue to another , support cartilage and bone, store and transport materials, etc.
Muscular TissuesMuscle Cells are made up of myocytes which can shorten considerably and return to the original relaxed state. Structurally, they consist of long, narrow cells called muscle fibers and the cytoplasm which is known as sarcoplasm.
It brings about movement of the body parts and locomotion of the organisms. These muscles support bones and other structures. They are responsible for the heart beat, flow of blood and lymph, movement of food through alimentary canal.
There are three types of muscle tissue -
Striped MuscleThe cell of this tissue are long, cylindrical, unbranded having multi nucleate. They have light deep coloured stripes on their outer surface therefore this muscle tissues is called striped or striated muscle tissue.
The striped muscles contract rapidly but not for long time. The contraction of striated muscle is under the control of person’s conscious will. Hence, called Voluntary Muscles. Most of the striped muscles are joined to the bones by tendons.