Connective tissue

Connective tissue

The most abundant and widely distributed of primary tissues

• Binding and support

• Protecting

• Insulating

• Storing reserve fuel

• Transporting substance (blood)

Characteristics of connective tissue

• Common embryonic origin: all arise from mesenchyme tissue

• Cells are embedded in extracellular matrix (ECM)

• Support cell so that they can bear weight, withstand tension, endure abuse

• Composed of ground substance and fibers

• Varying degrees of vascularity (cartilage is a, bone is highly vascularized)

Mesenchyme

A type of loosely organized embryonic connected tissue of undifferentiated cells

Structural elements of connective tissue

Ground substance, interstitial fluid, cell adhesion proteins for attachment, proteoglycans

• Fibers

• Collagen

• Elastic fibers

• Reticular

• Blast cells

• Cyte cells

Ground substance

Gel like material that fills space between cells, medium through which solutes diffuse

Interstitial fluid

Varying amounts, affecting viscosity of ground substance

Proteoglycans

Protein core with polysaccharides

Collagen

Strongest and most abundant, provides high tensile strength

Elastic fibers

Networks of long, thin, elastin fibers that allow for stretch and recoil

Reticular

Short, fine, highly branched collagenous fibers, offers more “give”

Blast cells

Immature form of cell-secretes ground substance and fibers

• Fibroblasts found in connective tissue

Cyte cells

Mature, less active form of blast cell that now becomes part of and helps maintain health of matrix

Other types of cells in connective tissues

• Adipocytes

• Leukocytes

• Mast cells

• Macrophages

Adipocytes

fat cells, store nutrients

Leukocytes

white blood cells

• neutrophils, eosinophils, lymphocytes

• tissue response to injury

Mast cells

Initiate local inflammatory response against foreign microorganisms they detect

Macrophages

Phagocytic cells that eat dead cells, microorganisms; function in immune system

Connective tissue proper

Have variety of cell types and protein fibers suspended in viscous ground substance

• Loose connective tissues (fibers loosely organized, highly vascularized)

• Dense connective tissues (fibers tightly organized-provides strength)

• Poorly vascularized

Areolar connective tissue

Supports, cushions, and binds other tissues. Act as a water reservoir holder interstitial fluid. Loose arrangement of mostly collagen fibers, some elastic and reticular fibers. Location: most widely distributed, universal packing material

• Loose fibers allow for increased ground substance

• Macrophagesand fat cells are contained in spaces

Clinical homeostatic imbalance

During infection or injury, areolar tissue in the area soaks up the excess fluid as a sponge

• Affected area swells and becomes puffy, a condition called edema

• Other causes include heart failure cirrhosis of the liver, venous insufficiency, and kidney disease

Adipose Tissue

Matrix similar to areolar but very sparse, fat droplet (mostly triglycerides) occupies most of Adipocytes volume

• Nucleus pushed to the side

Adipose tissue functions

• Shock absorption

• Insulation

• Energy storage

• White & Brown fat

Adipose tissue location

Subcutaneous tissue, around kidneys & eyeballs, within abdomen & breast

Reticular Connective Tissue

Resembles areolar tissue, but fibers are thinner reticular fibers (fibroblast)

• Secrete reticular fibers

Reticular fibers

Form a mesh like stroma: support for white blood cells, mast cells, and macrophages

Reticular Connective Tissue Location

• Lymphoid organs

• Lymph nodes

• Spleen

Dense regular connective tissue

Closely packed bundles of thick collagen fibers, Great resistance to pulling

Dense regular connective tissue location

• Tendons (attached muscle to bone)

• Ligaments (attaches bone to bone)

• Aponeuroses (attaches muscle to muscles or other tissues)

Dense Irregular Connective Tissue

Same structure as dense regular, but bundles of collagen are thicker and irregular arranged

• Form sheets

• Resists tension

Dense Irregular Connective Tissue Location

• Dermis

• Fibrous join capsules

• Fibrous Covering for some organs

Elastic Connective Tissue Location

• Walls of large arteries

• Ligaments associated with the vertebral column

• Walls of bronchial tubes