Connective Tissue Notes

Connective Tissue 1 – Tissue Characteristics

Embryonic Origins of Connective Tissue

  • Connective tissue (CT) is derived from the mesoderm.

  • Ectoderm develops into the epidermis (epithelium) of the skin and nervous tissue (i.e., the nervous system).

  • Mesoderm forms muscle, connective tissue, and the epithelium of reproductive, cardiovascular, and renal systems.

  • Endoderm forms the epithelial lining of the GI and respiratory systems.

  • The first connective tissue formed is mesenchyme, which contains: Primitive mesenchyme cells, abundant amorphous ground substance (AGS), and few fibers (mainly reticular fibers).

  • Primitive mesenchyme cells give rise to CT cells and stem blood cells.

Components of Connective Tissue

Connective tissue has three main components:

  1. Cells: Few cells are present.

  2. Fibers: Much intercellular material in the form of fibers (collagen, elastic, and reticular fibers).

  3. Amorphous Ground Substance (AGS): Also known as the matrix.

Different types of CT are formed by differences in:

  • Types of cells

  • Types of fibers

  • Ratio of fibers: cells & AGS

Cells

  • Structural Cells:

    • Synthesize (e.g., fibroblasts)

    • Store (e.g., adipocytes)

  • Immature cells: Known as “blasts” are builders that synthesize and secrete the extracellular matrix (ECM) and divide and differentiate into mature cells.

  • Mature cells: Known as “cytes” are caretaker cells that maintain and monitor the quality of the ECM.

  • Defense Cells: Protect the body against invasion. Main types seen are macrophages, mast cells, plasma cells, and WBCs (lymphocytes, neutrophils, and eosinophils).

Amorphous Ground Substance (AGS)/Matrix

  • Located between cells & fibers.

  • Functions to provide a medium for substance exchange.

  • Variations in AGS/Matrix:

    • Fluid (Blood)

    • Semifluid (Cartilage)

    • Gelatinous (most loose & dense CTs)

    • Hard (Bone)

  • Secures CT cells & fibers within the ECM.

Fibers

Three main fiber types:

  1. Collagen: Provides strength.

  2. Reticular fibers: Provide a net-like framework.

  3. Elastic fibers: Provide strength & elasticity.

Functions of Connective Tissue Components

  • Connects & binds tissues & organs & transmits forces – fibers (collagen).

  • Gives support, shape & flexibility - fibers (collagen, reticular & elastic fibers).

  • Provides mechanical protection – fibers (collagen).

  • Stores energy & acts as insulation – cells (adipocytes).

  • Transports nutrients/ waste products between blood & epithelium etc. - AGS.

  • Protects body from infections – involved in inflammation, immunity, healing – cells (macrophages, leukocytes, plasma cells, mast cells).

Basis for Classification of Connective Tissues

  • Proportions of cells to fibers to AGS

    • If the proportion of cells + AGS/matrix > the proportion of fibers, the CT is a loose CT.

    • If the proportion of cells + AGS/matrix < the proportion of fibers, the CT is a dense CT.

  • Organization/orientation of fibers

    • Dense Regular – fibers run parallel.

    • Dense Irregular – fibers run in all directions.

Functions of Connective Tissue Types

Functions are related to the components that are present in the greatest quantity.

  • Connects & binds other tissue types & organs - dense irregular CT.

  • Transmits force or provides strength in a single direction - dense regular CT, e.g., tendons, ligaments.

  • Gives support & shape - dense irregular CT or special CT, e.g., cartilage, bone.

  • Provides mechanical protection – dense irregular CT.

  • Stores energy & acts as insulation – loose CT.

  • Transports nutrients/ waste products between blood & epithelium etc. – loose CT.

  • Protects body from infections – involved in inflammation, immunity, healing – loose CT.

Embryonic Origins of Connective Tissue

  • Connective tissue (CT) is derived from the mesoderm.

  • Ectoderm develops into the epidermis (epithelium) of the skin and nervous tissue (i.e., the nervous system).

  • Mesoderm forms muscle, connective tissue, and the epithelium of reproductive, cardiovascular, and renal systems.

  • Endoderm forms the epithelial lining of the GI and respiratory systems.

  • The first connective tissue formed is mesenchyme, which contains: Primitive mesenchyme cells, abundant amorphous ground substance (AGS), and few fibers (mainly reticular fibers).

  • Primitive mesenchyme cells give rise to CT cells and stem blood cells.

Components of Connective Tissue

Connective tissue has three main components:

  1. Cells: Few cells are present.

  2. Fibers: Much intercellular material in the form of fibers (collagen, elastic, and reticular fibers).

  3. Amorphous Ground Substance (AGS): Also known as the matrix.

Cells

  • Structural Cells:- Synthesize (e.g., fibroblasts)

    • Store (e.g., adipocytes)

  • Immature cells: Known as “blasts” are builders that synthesize and secrete the extracellular matrix (ECM) and divide and differentiate into mature cells.

  • Mature cells: Known as “cytes” are caretaker cells that maintain and monitor the quality of the ECM.

  • Defense Cells: Protect the body against invasion. Main types seen are macrophages, mast cells, plasma cells, and WBCs (lymphocytes, neutrophils, and eosinophils).

Amorphous Ground Substance (AGS)/Matrix

  • Located between cells & fibers.

  • Functions to provide a medium for substance exchange.

  • Variations in AGS/Matrix:-

    • Fluid (Blood)

    • Semifluid (Cartilage)

    • Gelatinous (most loose & dense CTs)

    • Hard (Bone)

  • Secures CT cells & fibers within the ECM.

Fibers

Three main fiber types:

  1. Collagen: Provides strength.

  2. Reticular fibers: Provide a net-like framework.

  3. Elastic fibers: Provide strength & elasticity.

Functions of Connective Tissue Components

  • Connects & binds tissues & organs & transmits forces – fibers (collagen).

  • Gives support, shape & flexibility - fibers (collagen, reticular & elastic fibers).

  • Provides mechanical protection – fibers (collagen).

  • Stores energy & acts as insulation – cells (adipocytes).

  • Transports nutrients/ waste products between blood & epithelium etc. - AGS.

  • Protects body from infections – involved in inflammation, immunity, healing – cells (macrophages, leukocytes, plasma cells, mast cells).

Basis for Classification of Connective Tissues

  • Proportions of cells to fibers to AGS

    • If the proportion of cells + AGS/matrix > the proportion of fibers, the CT is a loose CT.

    • If the proportion of cells + AGS/matrix < the proportion of fibers, the CT is a dense CT.

  • Organization/orientation of fibers

    • Dense Regular – fibers run parallel.

    • Dense Irregular – fibers run in all directions.

Functions of Connective Tissue Types

Functions are related to the components that are present in the greatest quantity.

  • Connects & binds other tissue types & organs - dense irregular CT.

  • Transmits force or provides strength in a single direction - dense regular CT, e.g., tendons, ligaments.

  • Gives support & shape - dense irregular CT or special CT, e.g., cartilage, bone.

  • Provides mechanical protection – dense irregular CT.

  • Stores energy & acts as insulation – loose CT.

  • Transports nutrients/ waste products between blood & epithelium etc. – loose CT.

  • Protects body from infections – involved in inflammation, immunity, healing – loose CT.