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WHAT TISSUES ARE ? Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning. Organs are then formed by the functional grouping together of multiple tissues.

Study of tissue: 

Study of tissue The study of tissue is known as Histology or, in connection with disease, histopathology. The classical tools for studying tissues are the paraffin block in which tissue is embedded and then sectioned, the histological stain, and the optical microscope.

Types of TISSUES: 

Types of TISSUES

Plant Tissue: 

Plant Tissue A mature Vascular Tissue (any plant other than mosses and liverworts), contains several types of differentiated cells. These are grouped together in tissues. Some tissues contain only one type of cell. Some consist of several.

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Meristematic TISSUE: 

Meristematic TISSUE The main function of Meristematic tissue is mitosis( division of tissues). The cells are small, thin-walled, with no central vacuole and no specialized features.


LOCATION Meristematic tissue is located in:- the apical meristems at the growing points of roots and stems. the secondary meristems (lateral buds) at the nodes of stems (where branching occurs), and in some plants, Meristematic tissue, called the cambium, that is found within mature stems and roots. The cells produced in the meristems soon become differentiated into one or another of several types.

Permanent tissue: 

Permanent tissue The Meristematic tissues that take up a specific role lose the ability to divide. This process of taking up a permanent shape, size and a function is called cellular differentiation. Cells of Meristematic tissue differentiate to form different types of permanent tissue. There are 2 types of permanent tissues: simple permanent tissues complex permanent tissues

TYPES OF Permanent Tissue: 

TYPES OF Permanent Tissue


SIMPLE PERMANENT TISSUE These tissues are called simple because they are composed of similar types of cells which have common origin and function. They are further classified into: Parenchyma Collenchymas Sclerenchyma Epidermis


Parenchyma Parenchyma is the most specialized primitive tissue. It mainly consists of thin-walled cells which have intercellular spaces between them. The cell wall is made up primarily of cellulose. Each parenchymatous cell is iso-diametric, or roughly spherical in shape. This tissue is widely distributed in various plant organs, but it mainly occurs in the cortex, epidermis, and pith, as well as in the mesophyll of leaves. The main function of parenchymatous tissue is assimilation and storage of reserve food materials like starch, fats and proteins. They also store waste products such as gums, resins, and inorganic waste materials.

LOCATION AND Importance: 

LOCATION AND Importance This tissue is found in the palisade and spongy tissues in the green leaves and the stem cortex of the herbs where photosynthesis occurs. Aerenchyma is a forms of parenchyma possessing large air cavities. In aquatic plants the cavities in the intercellular spaces give Buoyancy to the plant and help them float in water.


COLLENCHYMAS Collenchymas is Greek word where "Collen" means gum and "enchyma" means infusion. It is a living tissue of primary body like Parenchyma. Cells are thin-walled but possess thickening of cellulose and pectin substances at the corners where number of cells join together. This tissue gives a tensile strength to the plant and the cells are compactly arranged and do not have inter-cellular spaces. It occurs chiefly in hypodermis of stems and leaves. It is absent in monocots and in roots.


LOCATION AND IMPORTANCE Collenchymatous tissue acts as a supporting tissue in stems of young plants. It provides mechanical support, elasticity, and tensile strength to the plant body. It helps in manufacturing sugar and storing it as starch. It is present in margin of leaves and resist tearing effect of the wind.


Sclerenchyma This tissue consists of thick-walled, dead cells. These cells have hard and extremely thick secondary walls due to uniform distribution of lignin. Lignin deposition is so thick that the cell walls become strong, rigid and impermeable to water. Sclerenchymatous cells are closely packed without inter-cellular spaces between them. Thus, they appear as hexagonal net in transverse section.


LOCATION AND IMPORTANCE Sclerenchymatous cells mainly occur in hypodermis, pericycle, secondary xylem and phloem. They also occur in endocarp of almond and coconut. The main function of Sclerenchymatous tissues is to give support to the plant.


EPIDERMIS The entire surface of the plant consists of a single layer of cells called epidermis or surface tissue. The entire surface of the plant has this outer layer of epidermis. Hence it is also called surface tissue. Most of the epidermal cells are relatively flat. the outer and lateral walls of the cell are often thicker than the inner walls. The cells forms a continuous sheet without inter cellular spaces. It protects all parts of the plant.


COMPLEX PERMANENT TISSUE A complex permanent tissue may be classified as a group of more than one type of tissue having a common origin and working together as a unit to perform a function. These tissues are concerned with transportation of water, mineral, nutrients and organic substances. The important complex tissues in vascular plants are Xylem Phloem


Xylem Xylem is a chief, conducting tissue of vascular plants. It is responsible for conduction of water and mineral ions. Xylem is a very important plant tissue as it is part of the ‘plumbing’ of a plant. It carries water and dissolved substances throughout and consists of a combination of parenchyma cells, fibers, vessels, tracheids and ray cells. These cells are joined end to end to form long tubes. Vessel members and tracheids are dead at maturity.


PHLOEM Primarily, phloem carries dissolved food substances throughout the plant. This conduction system is composed of sieve-tube member and companion cells that are without secondary walls. This usually also includes fibers, parenchyma and ray cells. The end walls, unlike vessel members in xylem, do not have openings. The end walls, however, are full of small pores where cytoplasm extends from cell to cell. These porous connections are called sieve plates.


ANIMAL TISSUE Animal tissues can be grouped into four basic types: connective, muscle, nervous, and epithelial. Multiple tissue types comprise organs and body structures. While all animals can generally be considered to contain the four tissue types, the manifestation of these tissues can differ depending on the type of organism.


FUNCTIONS OF ANIMAL TISSUE This tissue covers all organismal surfaces that come in contact with the external environment such as the skin, the airways, and the digestive tract. It serves functions of protection, secretion, and absorption, and is separated from other tissues.

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EPITHELIAL TISSUE The epithelial tissues are formed by cells that cover organ surfaces such as the surface of the skin, the airways, the reproductive tract, and the inner lining of the digestive tract. The cells comprising an epithelial layer are linked via semi-permeable, tight junctions; hence, this tissue provides a barrier between the external environment and the organ it covers. In addition to this protective function, epithelial tissue may also be specialized to function in secretion and absorption. Epithelial tissue helps to protect organisms from microorganisms, injury, and fluid loss.


SQUAMOUS TISSUE Squamous cells have the appearance of thin, flat plates. The shape of the nucleus usually corresponds to the cell form and help to identify the type of epithelium. Squamous cells tend to have horizontal flattened, elliptical nuclei because of the thin flattened form of the cell. They form the lining of cavities such as the mouth, blood vessels, heart and lungs and make up the outer layers of the skin.


CUBOIDAL TISSUE As their name implies, cuboidal cells are roughly square or cuboidal in shape. Each cell has a spherical nucleus in the centre. Cuboidal epithelium is found in glands and in the lining of the kidney tubules as well as in the ducts of the glands. They also constitute the germinal epithelium which produces the egg cells in the female ovary and the sperm cells in the male testes.


COLUMNAR TISSUE These are simple columnar epithelial cells, but in addition, they posses fine hair-like outgrowths, cilia on their free surfaces. These cilia are capable of rapid, rhythmic, wavelike beatings in a certain direction. This movement of the cilia in a certain direction causes the mucus, which is secreted by the goblet cells, to move (flow or stream) in that direction. Ciliated epithelium is usually found in the air passages like the nose. It is also found in the uterus and Fallopian tubes of females. The movement of the cilia propels the ovum to the uterus.


STRATIFIED SQUAMOUS TISSUE Where body linings have to withstand wear and tear, the epithelia are composed of several layers of cells and are then called compound or stratified epithelium. The top cells are flat and scaly and it may or may not be keratinized (i.e. containing a tough, resistant protein called keratin). The mammalian skin is an example of dry, keratinized, stratified epithelium. The lining of the mouth cavity is an example of an unkeratinisied, stratified epithelium.


CONNECTIVE TISSUE Connective tissues are fibrous tissues. They are made up of cells separated by non-living material, which is called extracellular matrix. Connective tissue gives shape to organs and holds them in place. Both blood and bone are examples of connective tissue. As the name implies, connective tissue serves a "connecting" function. It supports and binds other tissues. Unlike epithelial tissue, connective tissue typically has cells scattered throughout an extracellular matrix.


AEROLAR TISSUE Aerolar Connective Tissue is found between skin and muscles, around the blood vessels and nerves and in the bone marrow. It fills the space inside the organs, supports the internal organs and helps in the repair of tissues.

Adipose tissue: 

Adipose tissue Adipose Tissue is found below the skin and between internal organs. These are fat storing tissues. The cells of these tissues are filled with fat globules. Storage of fats also lets it act as an insulator.


COMPACT BONE Bone is an another example of a connective tissue. It forms the framework that supports the body. It also anchors the muscles and supports the main organs of the body. It is the strong and non-flexible tissue. Bone cells are embedded in a hard matrix i.e. composed of calcium and phosphorus compounds.

Hyaline cartilage: 

Hyaline cartilage Hyaline Cartilage has a widely spaced cells. The solid matrix is composed of proteins and sugars. Cartilage smoothens the bone surfaces at joints and is also present in the nose, ears, trachea, and larynx.


TYPES OF BLOOD CELLS Blood has a fluid matrix called plasma, in which red blood cells, white blood cells and platelets are suspended. The Plasma contains proteins, salts and hormones, Blood flows and transport gases, digested foods, hormones and waste materials to different parts of the body.


MUSCULAR TISSUE Muscular Tissue consists of elongated cells also called muscle fibres. This tissue is responsible for movement in our body. Muscle contains special proteins called Contractile proteins, which contract and relax to cause movement.

striated MUSCLES: 

striated MUSCLES The cells of this tissue are long, cylindrical, unbranched and multinucleated. They are called Striated Muscle. These muscle are under our conscious will when want to them to move and stop. These muscles are also called Voluntary Muscles. Another name of these muscles are skeletal muscles because they are mostly attached to the bones and help in body movement.


SMOOTH MUSCLE The cells are long with pointed ends and uninucleate. The are also called unstriated muscles. They are called involuntary muscles .We cannot really start them or stop them .They are also found in the iris of the eye ,in ureters and in the bronchi of the lungs.

Cardiac MUSCLES: 

Cardiac MUSCLES The muscles of the heart show rhythmic contraction and relaxation throughout life. These involuntary muscles are called cardiac muscles. Heart muscle cells are cylindrical, branched and uninucleate.


NERVOUS TISSUE The brain, spinal cord and nerves are all composed of the nervous tissue. The cells of this tissue are called Nerve cells or “Neurons”. A Neuron consist of a cell body with a nucleus and cytoplasm, from which long thin hair like parts arise. Each Neuron has a single long part, called the ‘Axon’ and many short, branched parts called dendrites. Nervous Tissue are highly specialized for being stimulated and then transmitting the stimulus very rapidly from one place to another with in the body. A individual Nerve cell may be up to a meter a long. Many Nerve fibres bound together by connective tissue, make up a nerve.

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