Class 9 Science Chapter 6 Notes Tissues
→ Tissue : A group of cells with similar structure, working together to perform a common function.
→ Meristematic Tissue : Tissue made up of actively dividing cells present in the growing area of the plant body.
→ Apical meristems : Meristems present at the growing tips of stems and root that cause the stem and root to increase in length.
→ Lateral meristems : Meristems located on the lateral position of the plant and responsible for the girth of the stem and the root increases.
→ Intercalary meristems : Meristems found between already differentiated tissue in locations such as the base of leaves or internodes.
→ Permanent tissue : A well-differentiated plant tissue derived from meristematic tissue which has lost its ability to divide.
→ Differentiation : The process by which a cell attains a permanent shape, size and function.
→ Simple permanent tissue: A permanent tissue composed of only one type of cells.
→ Complex permanent: A permanent tissue composed of more than one type of tissue cells which co-ordinated to perform a common function.
→ Chlorenchyma : Parenchyma whose cells contain chloroplasts and hence perform photosynthesis.
→ Aerenchyma : Parenchyma containing large air cavities providing buoyancy to aquatic plants and allowing the circulation of gases.
→ Xylem : The complex tissue that conducts water and minerals in vascular plants and composed of tracheids, vessels, fibres and parenchyma.
→ Phloem : The food conducting tissue of vascular plants consisting of sieve tubes, companian cells fibres and parenchyma.
→ Epidermis : The outermost protective layer of cells covering the surface of a plant.
→ Stratified epithelium : An epithelium compound of multiple layers of cells, with only the basal layer being in contact with the basement membrane.
→ Ligament : A fibrous connective tissue that connects bones to bones.
→ Tendon : A fibrous connective tissue that connects bones to bones.
→ Voluntary muscles : Muscles which can be controlled according to our will.
→ Involuntary muscles : Muscles which are not under the control of our will.
→ Multi nucleated cells : Cell containing more than one nucleus.
→ Uninucleate cell : Cell containing only one nucleus.
→ Neuron : A cell of the nervous system specialised to conduct nerve impulses and made up of cell body axon and dendrites.
→ Impulse : An electrical signal transmitted along a nerve fibre in response to a stimuli.
→ Group of cells having common origin and similar functions are termed as tissues.
→ On the basis of dividing capacity, plant tissues are of two types –
- Meristematic tissues
- Permanent tissues
→ Meristematic tissues comprises actively dividing cells.
→ Meristematic tissues are of three types –
- Apical meristem
- Intercalary meristem
- Lateral meristem
→ Permanent tissues formed from meristematic tissues.
→ Parenchyma comprises unspecialised living cells with relatively thin cell walls, intercellular space present in soft parts of the plant.
→ Main function of parenchyma is storage.
→ Collenchyma comprises living and elongated cells with cell walls irregularly thickened at the corners without intercellular spaces.
→ Collenchyma provides mechanical support and elasticity to plant and helps in bending of leaves and stems.
→ Sclerenchyma composed of long, narrow and thick walled cells and made up of dead cell without intercellular spaces.
→ Sclerenchyma cells are present in seeds, nuts, the husk of a coconut, fibres of jute etc.
→ Complex permanent tissue made up of more than one type of cells.
→ Xylem conducts water and minerals from the roots to different parts of the plant.
→ Xylem comprises trachieds, vessels, xylem parenchyma and Xylem fibres.
→ Phloem conducts food material from the leaves to the different parts of the body.
→ Phloem comprises sieve tubes, companion cells, phloem parenchyma and phloem fibres. of the animal body.
→ Simple squamous epithelium comprises single layer of flat cells.
→ Simple squamous epithelium present at lining of mouth, oesophagus, lung, alveoli etc.
→ Cuboidal epithelium consists of cube like cells.
→ Cuboidal epithelium present at lining of the kidney tubules and ducts of the salivary glands. Its function is to secretion and absorption.
→ Columnar epithelium specialised to connect various body organs.
→ Areolar tissyees found in the skin and muscles, around the blood vessels, nerves etc.
→ Adipose tissue acts as the storage site of fats found between the internal organs and below the skin acts as an insulator for the body.
→ Dense regular connective tissue comprises tendons and ligaments.
→ Tendons connect muscles to bones while ligaments connect two bones together.
→ Skeletal tissue comprises cartilage and bone.
→ Bone forms the frame work supports the body. It also anchors the muscles and supports the main organs of the body.
→ Bone cells are embedded in a hard matrix that is composed of calcium and phosphorous compounds.
→ Ligaments are elastic and contain very little matrix and connect bones with bones.
→ Tendons are fibrous tissue with great strength but limited flexibility.
→ Cartilage smoothens bones surfaces at joints and is also present in the nose, ear, trachea and larynx.
→ Blood has a fluid matrix called plasma in which RBCs, WBCs and platelets are suspended.
→ Plasma contains proteins, salts and hormones.
→ Blood flows and transport gases, digested food, hormones and waste materials to different parts of the body.
→ Muscular tissue consists of elongated cells, also called muscle fibres.
→ Muscular tissue responsible for movement in our body.
→ Muscles contain special proteins called contractile proteins which contract and relax to cause movement.
→ We can move some muscles by our conscious will. Such muscles are called voluntary muscles.
→ These cells of muscle tissue are long, cylindrical unbranched and multinucleate.
→ The muscles have striations or bands in them, hence they are called striated muscles.
→ The movement of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary movements. Such muscles are called involuntary are smooth muscles.
→ In voluntary muscles are found in the iris of the eye, in ureters and bronchi of the lungs.
→ In smooth muscles the cells are long with pointed ends (spindle shaped) and uninucleate.
→ The smooth muscles are also called as unstriated 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.
→ Cells of the nervous tissue are highly specialised for being stimulated then transmitting the stimulus very rapidly from one place to another with in the body.
→ The nervous tissue comprises the brain, the spinal cord and nerves.
→ The cells of the nervous tissue are called nerve cells or neurons.
→ A neuron comprises a cell body with a nucleus and cytoplasm from which long hair like parts arise.
→ Each neuron has a single long part called the axon, and many short branched parts (processes) called dendrites.
→ An individual nerve cell may be upto a metre long.
→ The signal that passes along the nerve fibre is called a nerve impulse.
→ The functional combination of nerve and muscle tissue is fundamental to most animals. This combination enables animals to move rapidly in response to stimuli.
→ Division of Labour : Different cells in different organs carry out different functions. This makes working more efficient.
→ Cell differentiation : The process by which cells become specialised to do specific functions and form permanent tissues is called differentiation.
→ Pits : Oblique thin areas (unlignified) found in the walls of sclerenchyma cells tracheids and vessels of xylem are called pits.
→ Corpuscles : The cells found in the blood plasma are called corpuscles.These are two types :
- Red Blood Corpuscles (RBC) and
- White Blood Corpuscles (WBC)
→ Matrix : It is a medium in which cells are dispersed. It may be solid as in bone and cartilage or fluid in the blood.
→ Cyton : The part of neuron which has a nucleus and cytoplasm. It is also called cell body.
→ Dendrites : The fine fibres arising from the cell body of a neuron.
→ Axon : The single elongated fibre also called nerve fibre, which arises from the cell body of a neuron.
