Connective Tissue -It binds body structures together or provide a framework for the body. - It Supports, binds, and separates specialized structures of body (Act as a packing tissue for the body). -It is derived from mesoderm (embryonic type of tissue)

All connective tissue consists of three main components: 1- Fibers. 2- ground substance (amorphous gel-like substance surrounding the cells). 3- cells.

1-Fibers: (Collagenous, Elastic, Reticular) Collagenous (white) Made of collagen and consist of bundles of fibrils that are coils of collagen molecules.

Elastic (Yellow) Made of elastin and are "stretchable."

Reticular Fiber Consist of one or more types of very thin collagen fibers. They join connective tissues to other tissues.

2- Ground Substance (extracellular matrix). Amorphous gel-like substance surrounding the cells. Form the extracellular matrix (not include fibers). : Ground substance is primarily composed of water, glycosaminoglycans, proteoglycans, and glycoproteins. Usually it is not visible on slides, because it is lost during staining in the preparation process.

3- Cells: Fibroblasts Adipocytes Mast cell Macrophages Leucocytes

Connective Tissues are either loose or dense depending on the proportion of cells and fibers. loose connective tissue: if cells are very numerous. Dense connective tissue : if cells are few and the tissue consists mainly of closely packed fibers

LOOSE CONNECTIVE TISSUE  Is the most common type of connective tissue in vertebrates.  It holds organs in place and attaches epithelial tissue to other underlying tissues. For example, it forms submucosa and subserosa, which connect mucous and serous membranes to the muscular layer.  It also surrounds the blood vessels and nerves.  Cells called fibroblasts are widely dispersed in this tissue; they are irregular branching cells that secrete strong fibrous proteins and proteoglycans as an extracellular matrix.

TYPES OF LOOSE CONNECTIVE TISSUE There are three types of Loose Connective Tissue: 1. Areolar C.T. 2. Reticular C.T. 3. Adipose C.T.

1. Areolar C.T. A common type of loose connective tissue. It is strong enough to bind different tissue types together, yet soft enough to provide flexibility and cushioning. Many adjacent epithelial tissues (which are avascular) get their nutrients from the interstitial fluid of areolar tissue. Its fibers run in random directions and are mostly collagenous, but elastic and reticular fibers are also present.

1- AREOLAR C.T.

2. Reticular C.T. A type of connective tissue with a network of reticular fibers, made of type III collagen (reticulum = net or network). Reticular fibers are not unique to reticular connective tissue, but only in this type are they dominant. Reticular fibers are synthesized by special fibroblasts called reticular cells. The fibers are thin branching structures. It resembles areolar connective tissue, but the only fibers in its matrix are reticular fibers, which form a network along with fibroblasts called reticular cells.

Reticular C. T.

3. Adipose C.T. Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of Adipocytes. Fibroblasts, Vascular endothelial cells Macrophages.  Its main role is to store energy in the form of lipids, although it also cushions and separates the body.  The two types of adipose tissue are white adipose tissue (WAT), which stores energy, and brown adipose tissue (BAT), which generates body heat.

3- Adipose C.T.

DENSE CONNECTIVE TISSUE Also called dense fibrous tissue, is a type of connective tissue with fibers as its main matrix element.  The fibers are mainly composed of type I collagen.  Crowded between the collagen fibers are rows of fibroblasts (fiber-forming cells that generate the fibers).  It forms strong, rope-like structures such as tendons and ligaments.  Tendons attach skeletal muscles to bones; while ligaments connect bones to bones at joints.  Ligaments are more stretchy and contain more elastic fibers than tendons.  Dense connective tissue also makes up the lower layers of the skin (dermis).

1- Dense Regular Connective Tissue Location: Tendons and Ligaments Function: Attaches muscle to bone (tendons) and bone to bone (ligaments).

Dense Irregular Connective Tissue Location: Dermis of skin Function: Stress resistant

White collagenous)) Fibrous C.T.

2. ELASTIC C.T. Elastic fibers (or yellow fibers) are bundles of proteins (elastin) found in extracellular matrix of connective tissue and produced by fibroblasts and smooth muscle cells in arteries. These fibers can stretch up to 1.5 times their length, and snap back to their original length when relaxed. Elastic fibers are found in the skin, lungs, arteries, veins, elastic cartilage,fetal tissue and other structures.

Elastic C.T.