Structural Organisation in Animals - Notes | Class 11 | Animal Tissues | Connective Tissues

II. Connective Tissue

• It links and supports other tissues/organs.
• They are most abundant in complex animals.
• All connective tissues except blood have fibroblast cells. They secrete structural fibrous proteins called collagen & elastin. They give strength, elasticity & flexibility to tissue.
• The cells also secrete modified polysaccharides (matrix), which accumulate between cells and fibres.
• Types of connective tissues: Loose, Dense & Specialised.

1. Loose Connective Tissues

In this, cells (fibroblasts, macrophages, mast cells etc.) and fibres are loosely arranged in a semi-fluid matrix.

It is of 2 types:

Areolar tissue:

• Present beneath the skin.
• It serves as a support framework for epithelium.

Adipose tissue:

• Seen mainly under skin.
• Its cells (adipocytes) store fats.
• Excess nutrients which are converted into fats are stored in this tissue.

2. Dense Connective Tissues

In this, fibres and fibroblasts are compactly packed.

It is of 2 types:

Dense regular connective tissues:

• Show regular pattern of fibres.
• Collagen fibres are present in rows between many parallel bundles of fibres.
• E.g. tendons & ligaments.
• Tendons: Attach muscles to bones.
• Ligaments: Attach one bone to another.

Dense irregular connective tissues:

• Irregular pattern of fibres.
• Fibroblasts & fibres (mostly collagen) are oriented differently.
• This tissue is present in skin.

3. Specialized Connective Tissues

Cartilage:

• In this, intercellular material (matrix) is solid and pliable (due to chondroitin salts) and resists compression.
• Cartilage cells (chondrocytes) are enclosed in small cavities within the matrix secreted by them.
• Most of the cartilages in vertebrate embryos are replaced by bones in adults.
• Cartilage is present in the tip of nose, outer ear, joints in the vertebral column, limbs and hands in adults.

Bone:

• It has hard and non-pliable matrix rich in calcium salts and collagen fibres which give bone its strength.
• Bone cells (osteocytes) are seen in spaces called lacunae.
• Functions:
• It provides structural frame to the body.
• Support and protect softer tissues and organs.
• Limb bones serve weight-bearing functions.
• Take part in locomotion and movements.
• Blood cells are produced in bone marrow.

Blood:

• A fluid connective tissue containing plasma, red blood cells (RBC), white blood cells (WBC) and platelets.
• Helps in the circulation of various substances.

Select a Topic 👇

1. Animal Tissues (Epithelial Tissues) 2. Animal Tissues (Connective Tissues) 3. Animal Tissues (Muscle and Neural Tissues) 4. Cockroach- Morphology 5. Cockroach- Anatomy 6. Earthworm- Morphology 7. Earthworm- Anatomy 8. Frog- Morphology & Anatomy

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