Connective tissue

• Is of mesodermal origin.
• Is found throughout the body.
• Is the most abundant and widely distributed tissue.
• Provides structural and metabolic support to the other tissues and organs.

Functions of Connective Tissues

• Forms structural framework.
• Supports and interconnects tissues.
• Transports fluids and dissolved materials.
• Stores energy.
• Defends the body against microorganisms.
• Protects delicate organs.

Structural Components of Connective tissue

Connective tissue consists of :

• Cells and
• Extracellular matrix (ECM) which contains fibers and ground substance.

Cells of Connective Tissue

There are two types of cells

• • Fixed or permanent cells: these cells are native to the  connective tissue in which they are found. These are:
    • Fibroblasts  and fibrocytes
    • Adipose/ fat cells
    • Fixed macrophage
  • Wandering cells: Are immigrant cells usually from blood or bone marrow. These are:
    • Mast cells
    • Plasma cells
    • Wandering macrophages
    • Leukocytes

Fibers of Connective Tissue

• • Collagen fibers :They are tough, thick and non-branching fibers. They have great tensile strength.They are the most abundant type of fibers in the body.T There are many tpes of collagen fibers, them ost common types of collagen fibers are:
    • Type I collagen fibers:  Are most abundant  are found in:
      • Dermis of skin
      • Fascia
      • Ligaments and capsules of joints
      • Capsules of  organs
      • Tendons
      • Bones
    • Type II collagen fibers: They provide resistance to pressure. Are found in:
      • Hyaline and elastic cartilage
      • Vitrous humor of eye.
    • Type III collagen fibers: These are thin delicate fibers that form supporting meshwork in organs such as:
      • Liver
      • Lymph node
      • Spleen
      • Bone marrow
    • Type IV collagen fibers: They are present in the basal lamina of basement membranes.
  • Elastic fibers: They are thin, wavy, small and branching. They have less tensile strength , but are capable of Streching and returning to thier original length.
  • Reticular fibers: They are type III collagen fibers ( see above).

Ground substance

It is a transparent viscous substance like a hydrated gel.It fills the space between cells and contains:

• Adhesion proteins such as fibronectin and laminin.
• Proteoglycans such as hyluronic acid and chondroitin sulfate.

Types of connective Tissue

Connective tissue is classified into following types:

• Connective Tissue proper

  • Loose connective tissue/Areolar tissue: Is composed of loosely arranged network of collagen, elastic fibers with cells embedded in ground substance. e.g. superficial fascia, mesentry.
  • Dense connective tissue
    • Dense regular connective tissue: In this type of tissue, the collagen fibres are densely packed, and arranged in parallel. e.g. ligaments (which link bone to bone at joints) and tendons (connections between bones or cartilage and muscle).
    • Dense irregular connective tissue: It has fibers that are not arranged in parallel bundles as in dense regular connective tissue. It has less ground substance than loose connective tissue. e.g. dermis of skin, periosteum and capsules of various organs.

• Specialized Connective Tissue

Specialized connective tissue are:

• • Bone
  • Cartilage
  • Adipose Tissue