week 2 LSB421 lecture 4

Introduction to Connective Tissue

• Connective tissue serves several vital purposes in the body:

  • Provides strength to withstand external forces such as gravity.

  • Protects internal organs from injury or damage.

  • Maintains the shape and structure of organs for optimal function.

  • Offers a rigid framework that allows muscles to generate movement.

Major Classes of Connective Tissue

• Connective tissue consists of several main types:

  • Connective Tissue Proper

  • Cartilage

  • Bone

  • Blood

Functions of Connective Tissue

• Establishes connections between distant body regions via blood circulation.

• Carries nutrients and waste products throughout the body.

• Composed of cells and an extracellular material known as the extracellular matrix (ECM).

• Composition and characteristics of the ECM vary among different classes of connective tissue.

Components of the Extracellular Matrix

• Extracellular fibers are vital for the mechanical properties of connective tissue:

  • Collagen Fibers:

    • Formed from interconnected tropocollagen proteins.

    • Provide tensile strength and resistance to stretching.

  • Reticular Fibers:

    • Thinner and more delicate than collagen fibers.

    • Contribute to the structural framework that anchors cells.

  • Elastic Fibers:

    • Allow for extensibility and quick return to original form when stretched.

    • Impart elasticity and springiness to tissues.

Connective Tissue Proper

Subtypes of Connective Tissue Proper

• Divided into two main subtypes:

  • Loose Connective Tissue:

    • Comprised of a gel-like matrix interwoven with fibers.

    • Supports, strengthens, and provides elasticity to epithelia.

    • Plays an important role in inflammation and immune responses.

    • Types include:

      • Areolar Connective Tissue:

        • Located under epithelial tissues; retains water.

      • Reticular Connective Tissue:

        • Contains reticular fibers; supports blood-forming cells in lymph nodes and spleen.

      • Adipose Tissue:

        • Composed mainly of fat cells; stores energy and provides insulation.

  • Dense Connective Tissue:

    • Contains fewer cells and a matrix primarily made of fibers.

    • Types include:

      • Regular Dense Connective Tissue:

        • Collagen fibers arranged in parallel; found in tendons and ligaments.

      • Irregular Dense Connective Tissue:

        • Collagen fibers run in various directions; provides resistance to stretching forces.

      • Dense Elastic Connective Tissue:

        • Rich in elastic fibers; found in the walls of airways and large arteries.

Cartilage

• Located at the ends of bones and between joints, cartilage provides support and minimizes friction.

• Produced by specialized cells called chondroblasts.

• ECM of cartilage consists of collagen fibers and water-retaining proteoglycans.

• Types of cartilage include:

  • Hyaline Cartilage:

    • Most common; smooth covering on bone ends and connection points between ribs and sternum.

  • Elastic Cartilage:

    • Contains more elastic fibers; found in the external ear and epiglottis.

  • Fibrocartilage:

    • Contains more collagen fibers; provides tensile strength; found in intervertebral discs and knee joint menisci.

Bone (Osseous Tissue)

• Protects organs and offers structural support.

• Provides a framework for muscle attachment and force generation.

• Produced by osteoblasts, the extracellular matrix consists of:

  • Collagen fibers for tensile strength.

  • Calcium salts for hardness and compressive strength.