NCERT Solutions for Class 11 Biology Chapter 7 Structural Organisation in Animals

Short Note:

• Epithelial tissue forms protective coverings and inner linings of body surfaces, cavities, and organs with tightly packed cells and minimal intercellular matrix.

• Simple Epithelium: Single layer of cells functioning in absorption, secretion, and filtration.

  - Squamous Epithelium: Flattened cells with irregular boundaries (e.g., blood vessel walls, air sacs of lungs).

  - Cuboidal Epithelium: Cube-like cells (e.g., ducts of glands, nephrons of kidneys for secretion/absorption).

  - Columnar Epithelium: Tall and slender cells with basally located nuclei (e.g., lining of stomach and intestine).

  - Ciliated Epithelium: Columnar/cuboidal cells bearing cilia on free surface to move particles/mucus in a specific direction (e.g., bronchioles, fallopian tubes).

• Compound Epithelium: Multi-layered epithelium providing protection against mechanical and chemical stress (e.g., skin surface, pharynx, esophagus lining).

• Cell Junctions: Tight junctions (prevent leakage), Adhering junctions (cement neighboring cells), Gap junctions (facilitate rapid intercellular transport).

Short Note:

• Most abundant and widely distributed tissue in complex animals; binds, supports, and connects body organs.

• Loose Connective Tissue: Cells (fibroblasts, macrophages, mast cells) and fibers arranged loosely in ground substance.

  - Areolar Tissue: Serves as a support framework beneath the skin.

  - Adipose Tissue: Specialized for fat storage beneath skin and around internal organs.

• Dense Connective Tissue: Compactly packed fibers and fibroblasts.

  - Dense Regular: Parallel bundle fibers, e.g., Tendons (connect muscle to bone) and Ligaments (connect bone to bone).

  - Dense Irregular: Fibers oriented in various directions, found in the skin dermis.

• Specialized Connective Tissue:

  - Cartilage: Solid, pliable matrix containing chondrocytes (e.g., tip of nose, outer ear, intervertebral joints).

  - Bone: Hard, non-pliable matrix rich in calcium salts and collagen fibers containing osteocytes in lacunae.

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

Short Note:

• Muscular Tissue: Made of long, contractile muscle fibers containing myofibrils (actin and myosin filaments) that enable movement.

  - Skeletal Muscle: Striated, voluntary, multinucleated; attached to skeletal bones.

  - Smooth Muscle: Non-striated, involuntary, spindle-shaped (fusiform); found in walls of internal organs like gut and blood vessels.

  - Cardiac Muscle: Striated, involuntary, branched cells joined by intercalated discs; found exclusively in the heart wall.

• Neural Tissue: Exerts greatest control over body response to changing environments.

  - Neurons: Excitable functional units that transmit electrical impulses.

  - Neuroglial Cells: Non-excitable supporting cells that protect, nourish, and form more than half the volume of neural tissue.

Short Note:

• Morphology: Amphibian adapted for water and land. Body divided into Head and Trunk (neck and tail absent). Skin is smooth, moist, and scaleless with cutaneous respiration capability.

• Anatomy & Systems:

  - Digestive System: Complete alimentary canal; short intestine (carnivorous diet); liver produces bile, pancreas produces digestive enzymes.

  - Respiration: Cutaneous (skin) in water; Pulmonary (lungs) and Buccopharyngeal cavity on land.

  - Circulatory System: Closed, 3-chambered heart (2 atria + 1 ventricle) with Sinus Venosus and Truncus Arteriosus. RBCs are nucleated.

  - Excretory System: Pair of kidneys, ureters, urinary bladder, opening into Cloaca. Ureotelic animal.

  - Reproduction: External fertilization in water. Development includes a indirect larval stage (Tadpole larva undergoing metamorphosis).