Tissues in ActionClass 9 Science Important Points

A tissue is a group of cells that are similar in structure and work together to perform a specific function in a multicellular organism.

Plant tissues differ from animal tissues as plants are stationary and require structural support (rigid cell walls), while animals are mobile and need tissues for locomotion and complex organ systems.

Meristematic tissue is responsible for plant growth and consists of actively dividing cells. These tissues are located in specific regions where growth occurs.

Apical meristem increases the length of roots and shoots. Lateral meristem increases the girth or diameter of the stem. Intercalary meristem is found at the base of nodes and allows for regrowth in grasses.

Permanent tissues are formed when meristematic cells lose their ability to divide and take on a specific role. This process of specialization is called differentiation.

Simple tissues are composed of one type of cell. Parenchyma provides storage, collenchyma offers flexible support, and sclerenchyma gives rigid strength due to lignin.

Xylem is a complex tissue that transports water and minerals from the roots to all other parts of the plant. It consists of tracheids, vessels, xylem parenchyma, and xylem fibers.

Phloem is a complex tissue that transports food, mainly sugars produced during photosynthesis, from the leaves to other parts of the plant. It is primarily composed of living cells like sieve tubes and companion cells.

Epithelial tissue forms the outer covering of the body and lines internal organs and cavities. It provides protection and is involved in absorption, secretion, and sensory functions.

Connective tissue connects, supports, and binds other tissues and organs. Its cells are embedded in an extracellular matrix, which can be fluid (blood), jelly-like (cartilage), or hard (bone).

Blood transports gases and nutrients. Bone provides a structural framework. Cartilage cushions joints. Ligaments connect bone to bone, and tendons connect muscle to bone.

Muscular tissue is responsible for all types of movement in the body. It is composed of elongated cells called muscle fibers that can contract and relax.

Skeletal muscles are voluntary and striated, attached to bones. Smooth muscles are involuntary and found in internal organs. Cardiac muscle is involuntary, striated, and found only in the heart.

Nervous tissue is responsible for control and coordination, transmitting electrical signals throughout the body. The basic functional unit of nervous tissue is the neuron, or nerve cell.

A neuron consists of a cell body with a nucleus, dendrites that receive signals, and a long axon that transmits signals to other cells.

The musculoskeletal system consists of bones, muscles, cartilage, ligaments, and tendons. It works together to provide support, protect organs, and produce movement under the control of the nervous system.