NCERT Solutions for Class 9 Science Chapter 6 Tissues

Short Note:

• Definition of Tissue: A group of cells that are similar in structure and work together to achieve a particular function.

• Meristematic Tissue: Dividing cells responsible for growth in plants.

  - Apical Meristem: Present at growing tips of stems and roots (increases length).

  - Lateral Meristem (Cambium): Increases girth/girth thickness of stem or root.

  - Intercalary Meristem: Located at the base of leaves or internodes.

• Simple Permanent Tissues: Non-dividing cells derived from meristematic tissues by differentiation.

  - Parenchyma: Living cells with thin walls; provides support and stores food. Contains chlorophyll in Chlorenchyma and air cavities in Aerenchyma.

  - Collenchyma: Living cells with irregularly thickened corners; provides flexibility and mechanical support.

  - Sclerenchyma: Dead, narrow cells with thick lignin walls; makes plants hard and stiff (e.g., husk of coconut).

Short Note:

• Complex Permanent Tissue: Made of more than one type of cell working together as a unit.

• Xylem: Conducts water and minerals vertically upward from roots to leaves.

  - Constituents: Tracheids, Vessels, Xylem Parenchyma (stores food), and Xylem Fibres (supportive).

• Phloem: Translocates organic food (sucrose) from leaves to other plant parts in both directions.

  - Constituents: Sieve tubes, Companion cells, Phloem Parenchyma, and Phloem Fibres (only dead phloem component).

Short Note:

• Epithelial Tissue: Protective covering or lining tissue in animal bodies.

  - Squamous Epithelium: Flat cells for lining blood vessels, alveoli, and skin.

  - Cuboidal Epithelium: Cube-like cells in kidney tubules and salivary glands for mechanical support.

  - Columnar Epithelium: Pillar-like cells in intestine lining for absorption/secretion (Ciliated if hair-like projections are present).

• Connective Tissue: Connects, binds, and supports different organs.

  - Blood: Fluid matrix (plasma) containing RBCs, WBCs, and platelets.

  - Bone: Hard, rigid matrix rich in calcium and phosphorus.

  - Ligament: Connects bone to bone.

  - Tendon: Connects muscle to bone.

  - Cartilage: Smooths bone surfaces at joints (nose, ear, trachea).

  - Areolar Tissue: Fills space inside organs, supports internal organs, and repairs tissues.

  - Adipose Tissue: Stores fat beneath skin and around internal organs; acts as an insulator.

Short Note:

• Muscular Tissue: Elongated cells (muscle fibres) responsible for movement containing contractile proteins.

  - Striated / Skeletal Muscles: Voluntary, multinucleate, unbranched, with dark and light bands.

  - Smooth / Unstriated Muscles: Involuntary, spindle-shaped, uninucleate, present in stomach, intestine, iris.

  - Cardiac Muscles: Involuntary, branched, uninucleate, rhythmic contraction/relaxation in heart throughout life.

• Nervous Tissue: Specialized for receiving and transmitting stimuli rapidly.

  - Neuron: Basic unit of nervous tissue. Consists of a cell body (cyton), axon (long single process), and dendrites (short branched processes).