Connective Tissues Notes

Epithelial Tissues

• Structural and Functional Characteristics

  • Protective barrier

  • Selectively permeable

  • Secretory functions

  • Sensory reception

• Classification of Epithelium

  • Types: Simple, Stratified

  • Shapes: Squamous, Cuboidal, Columnar

  • Functions: Protection, Absorption, Secretion, Filtration

  • Locations: Skin, Lining of cavities, Glands

• Glands

  • Definition: Group of cells specialized for secretion

  • Types:

    • Exocrine Glands: Secrete onto body surfaces or into cavities

    • Endocrine Glands: Secrete hormones into blood

    • Multicellular vs. Unicellular glands

• Classification of Multicellular Exocrine Glands

  • By mode of secretion: Merocrine, Holocrine, Apocrine

Connective Tissues

• Overview

  • Most abundant and widely distributed primary tissue

  • Major functions:

    • Binding and support

    • Protection

    • Insulation

    • Storage of reserve fuel

    • Transport (e.g., blood)

• Main Classes:

  • Connective Tissue Proper

  • Cartilage

  • Bone

  • Blood

• Characteristics

  • Arises from embryonic tissue called mesenchyme

  • Composed mainly of nonliving extracellular matrix

  • Most connective tissue is vascularized except tendons and cartilage

Structure of Connective Tissue

• Main Elements:

  • Ground substance

  • Fibres

  • Cells

• Cells of Connective Tissue

  • Immature "blast" cells secrete ground substance and fibres (e.g., fibroblasts, chondroblasts, osteoblasts)

  • Mature "cyte" cells maintain the health of the matrix (e.g., fibrocytes)

• Other Cell Types

  • Fat cells: Store nutrients

  • White blood cells: Respond to injury

  • Mast cells: Initiate inflammatory response

  • Macrophages: Phagocytes that digest dead cells and pathogens

Ground Substance

• Definition: Unstructured gel-like material that fills space between cells

• Composition:

  • Interstitial fluid

  • Adhesion proteins

  • Proteoglycans

  • Water content affects viscosity

Connective Tissue Fibres

• Types of Fibres:

  • Collagen: Strong, high tensile strength

  • Elastic: Stretchable and strong

  • Reticular: Forms branching networks; supportive

Cartilage

• Characteristics

  • Resilient, mainly water, and lacks blood vessels

  • Extracellular matrix secreted by chondroblasts and maintained by chondrocytes in lacunae

  • Perichondrium: Dense irregular connective tissue surrounding cartilage

• Types of Cartilage

  • Hyaline: Most abundant; found at ends of long bones, nose, trachea

  • Elastic: Flexible; found in external ear and epiglottis

  • Fibrocartilage: Strong; found in knee and intervertebral discs

Bone

• Definition: Type of connective tissue with exceptional hardness

• Composition: Collagen fibres and calcium salts in extracellular matrix

Blood

• Classification: Considered connective tissue as it develops from mesenchyme

• Components: Blood cells and plasma protein fibres, with soluble proteins that precipitate during clotting

Key Learning Outcomes

• Identify common characteristics and structural elements of connective tissue

• Describe types and functions of connective tissue in the body