Algonquin College
2.5 - Connective Tissue
In multicellular organisms cells of similar structure and function come together to create tissues. Complex organisms have many different cell types that fulfill different structural and physiological needs of the organism. There are four basic tissue types: epithelial, connective, nervous and muscle.

Connective tissue is the most common of the major tissue types. Its primary function is to support other tissues by joining them together, protecting them physically and by supporting their physiological needs by supplying substances like ions and nutrients.

All connective tissue types have three basic characteristics:
  • An extracellular matrix (a network of fibers and another substance that is either solid, jelly-like or liquid)
  • Cells of a specific type
  • Varied amounts of vascularization (blood supply)
There are five major classes of connective tissue: loose connective tissue, dense connective tissue, blood, cartilage and bone.

Loose connective tissue

A sparse network of fibers and a soft extracellular matrix are two common characteristics of all types of loose connective tissue. There are three common types of loose connective tissue:

Areolar loose connective tissue
  • Cells - fibroblasts
  • Matrix - fluid with sparse collagen and elastin fibers forming a three-dimensional "web"
  • Functions - lamina propria of mucous membranes, universal "packing" tissue, absorbs excess fluid during swelling to cause edema
Areolar tissue from LUMEN Histology



Source: LUMEN Histology at Loyola University

Adipose loose connective tissue
  • Cells - adipose cells (filled with oil droplets)
  • Matrix -fluid with sparse reticular and collagen fibers
  • Functions - padding, insulation and energy storage
Adipose tissue from LUMEN Histology



Source: LUMEN Histology at Loyola University

Reticular loose connective tissue
  • Cells - reticular cells
  • Matrix - fluid with loosely packed reticular fibers
  • Functions - storage site for blood cells of organs of the lymphatic system
Reticular tissue from LUMEN Histology



Source: LUMEN Histology at Loyola University

Dense (fibrous) connective tissue
  • Cells - fibroblasts
  • Matrix - dense collagen fibers
  • Functions - tendons (connect muscle to bone) and ligaments (connect bones together)
Dense connective tissue from LUMEN Histology



Source: LUMEN Histology at Loyola University

Bone
  • Cells - osteocytes
  • Matrix - dense collagen fibers and hard matrix containing calcium salts
  • Functions - rigid structural support and protection (skeletal system)
Bone from LUMEN Histology



Source: LUMEN Histology at Loyola University

Cartilage
  • Cells - chondrocytes
  • Matrix - collagen fibers in a semi-solid matrix; elastic cartilage also contains elastin fibers
  • Functions - flexible structural support and protection (hyaline cartilage, fibrocartilage and elastic cartilage)
Cartilage at LUMEN Histology



Source: LUMEN Histology at Loyola University

Blood
  • Cells - blood cells
  • Matrix - plasma (fluid) and soluble protein fibers
  • Functions - transport fluid for the cardiovascular system (carries nutrients, gases, ions and wastes and other soluble substances)
Blood from LUMEN Histology



Source: LUMEN Histology at Loyola University