This type of tissue is the most abundant, widespread, and varied of all tissue types in the body. It also has the widest variety of functions.

CONNECTIVE TISSUE

Connective tissue, such as “loose” or aereolar tissue, can function to bind structures together, hold organs in place or separate structures.

Connective tissue such as adipose (fat) tissue serves as a storage site for lipids (fats & oils), surrounds and protects internal organs, and provides an insulating layer to aid in body temperature regulation.

Other connective tissue such as blood helps to “connect” (in a communication sense) one part of the body to another, transport substances, fight infection, or aid in tissue repair.

For our purposes, the connective tissues we examine all function either to provide support, physically connect or anchor one structure to another, or serve as a framework. These tissues will be:

Tendon Ligament

Elastic CartilageFibrous Cartilage or

“Fibrocartilage”

Hyaline Cartilage3 Types of Cartilage

Tissue

2 Types of Bone Tissue

Cancellous or Spongy Bone

Compact Bone or Cortical bone

Spongy Bone Compact Bone

No matter what the tissue, one characteristic common to all connective tissue is that it is composed mostly of an intercellular material called “matrix.”

matrix

matrix

matrix

matrixmatrix

Tissue cells are then contained in this intercellular matrix but are "far" apart, relatively speaking.

matrix

matrix

matrix

matrixmatrix

cells

Cartilage cells or “Chondrocytes”

Bone Cells or “Osteocytes”

Tendon cells or “Fibroblasts”

Examples of cells found in various connective

tissues.

It is actually the composition of this matrix which gives each type of connective tissue its individual characteristics. Matrix itself is actually composed of two different things. These are protein fibres and ground substance.

ground substance

protein fibres

Ground Substance is described as an amorphous (shapeless or formless), extracellular material which serves as a diffusion medium in the spaces around the cells and fibers, and it plays a major role in determining the physical nature of a connective tissue.

ground substance

Ground substance can range in consistency from liquid, as in blood,

where the matrix is “plasma” and the ground substance is actually dilute saltwater,

to “gel-like”, as in cartilage

where the matrix can be collagen or elastic fibers in a ground substance called chondroitin sulfate,

or to solid, as in bone

where the matrix is collagen fibers in a mineral called hydroxyapatite, which is a form of calcium phosphate, Ca3(PO4)2

The fibres consist of long protein molecules that are embedded in the ground substance. They are produced by the tissue cells which are themselves contained within the matrix. There are two types of fibres contained in the connective tissue we will study – collagen fibers made from collagen or “tropocollagen” molecules and elastic fibers made from elastin molecules.

Collagen molecules form protein fibers which have a white color to the unaided eye, so we call them "white fibers." They are the major structural protein in the human body. In tissue the collagen fibers come together to form large bundles. Collagen fibers are only slightly flexible; they have great tensile strength, and are not very elastic.

The collagen molecule is a triple helix formed by three extended protein chains that wrap around one another. Many rod-like collagen molecules are cross-linked together in the extracellular space to form collagen fibrils (top) that have the tensile strength of steel.

Elastin molecules form protein fibers which have a yellowish or ivory color to the unaided eye, so we call them "yellow fibers." In tissue the elastin molecules often form large "web-like" structures. Elastic fibers are highly elastic and more flexible than collagen. However, they have much less tensile strength.

Elastin polypeptide chains are cross-linked together to form rubberlike, elastic fibers. Each elastin molecule uncoils into a more extended conformation when the fiber is stretched and will recoil spontaneously as soon as the stretching force is relaxed.