Chapter4b

Tissue: The Living Fabric

Four Types of Tissues

• Epithelial

• Connective

• Muscle

• Nervous

Connective Tissue

Overview

• Most abundant and widely distributed tissue type.

• Four major classes:

  • Connective tissue proper

  • Cartilage

  • Bone tissue

  • Blood

Common Embryonic Descendants

• Mesenchyme gives rise to:

  • Fibroblast (connective tissue proper)

  • Chondroblast (cartilage)

  • Osteoblast (bone)

  • Hematopoietic stem cell (blood)

Subclasses of Connective Tissue

1. Connective Tissue Proper

   • Loose: Areolar, Adipose, Reticular

   • Dense: Regular, Irregular, Elastic

2. Cartilage

   • Hyaline

   • Fibrocartilage

   • Elastic

3. Osseous (Bone)

   • Compact

   • Spongy (Cancellous)

4. Blood

Functions of Connective Tissue

• Binding and Support: e.g., cartilage, bone, ligaments, and tendons.

• Protection: e.g., cartilage, bone.

• Insulation: e.g., adipose tissue.

• Transportation: e.g., blood, lymph.

Characteristics of Connective Tissue

• Cells separated by nonliving extracellular matrix, which includes:

  • Ground substance (gel-like substance)

  • Fibers (collagen, elastic, reticular)

• Mesenchyme as common tissue of origin.

• Varying degrees of vascularity.

Structural Elements of Connective Tissue

1. Cells

   • Types include fibroblasts, chondroblasts, osteoblasts, hematopoietic stem cells, and various blood cells.

2. Matrix

   • Non-living extracellular matrix:

     • Ground substance fills space, medium for solute diffusion.

     • Fibers provide strength and elasticity.

Types of Fibers in Connective Tissue

• Collagen: Strongest, most abundant, provides tensile strength.

• Elastic: Allows stretch; found in larger arteries and lungs.

• Reticular: Fine, branched fibers supporting cellular structures.

Types of Connective Tissue

1. Loose Connective Tissue

   • Areolar: Wraps/cushions organs, retains tissue fluid.

   • Adipose: Stores fat, provides insulation.

   • Reticular: Supports other cell types in lymphoid organs.

2. Dense Connective Tissue

   • Dense Regular: Provides unidirectional tensile strength; found in tendons and ligaments.

   • Dense Irregular: Provides multidirectional strength; found in dermis and organ capsules.

   • Elastic: Allows recoil; found in arterial walls and ligaments.

3. Cartilage Types

   • Hyaline: Supports and reinforces, found in embryonic skeleton.

   • Elastic: Flexible support, found in ear and epiglottis.

   • Fibrocartilage: Provides tensile strength, found in intervertebral discs.

4. Bone Tissue

   • Supports and protects vital organs, store minerals, site for blood cell formation.

5. Blood

   • Transports gases, nutrients, and waste through its fluid matrix, plasma.