Connective Tissues

CONNECTIVE TISSUE

•         Development of connective tissue

-Connective tissue develops from mesenchyme, a derivative of mesoderm.

-To a large extent, connective tissue consists of the nonliving intercellular substances produced by certain of its cells.

-Cartilage & bone, as well as ligaments, tendons & fasciae develop from mesenchyme & represent types of connective tissue that consist chiefly of intercellular substances.

•         Connective tissue groups

1. Loose connective tissue,
2. Adipose tissue (fat tissue),
3. Blood cells,
4. The blood cell forming tissues,
5. Dense connective tissue,
6. Cartilage &
7. Bone

•         Basic components of general connective tissue

1. Cells
2. Ground substance
3. Fibers

•         Cells in general connective tissue

1. Cells that are intrinsic components of connective tissue:
1. Fibroblasts,
2. Undifferentiated mesenchymal cells,
3. Pigment cells &
4. Fat cells (Adipocytes)
2. Cells that belong to the immune system:
1. Macrophage cells (or histocytes),
2. Mast cells,
3. Lymphocytes,
4. Plasma cells,
5. Monocytes &
6. Eosinophils

•         Cells of connective tissue

•         Connective Tissue

•         Fibers of connective tissue

1. Collagen fibers:
1. Type I: connective tissue, tendons, ligaments, fascia, aponeuroses, dermis of skin & in meninges.
2. Type II: hyaline cartilage
3. Type III: reticular fibers
4. Type IV: basal lamina of basement membranes, lense capsule.
2. Reticular fibers:
1. Collagen fiber type III
3. Elastic fibers:
1. Ligamentum nuchae, Ligamenta flava

•         Three types of arrangement of collagen fibers in: (A) dense irregular connective tissue; (B) a ligament; (C) a tendon.

•         Loose connective tissue in the mesentery, viewed as a whole mount preparation stained to show the interwoven collagen fibres (red) and network of thin elastic fibres, with interspersed cells. Van Gieson/ Verhoeff’s stain.

•         T. S. of a tendon showing fibrocytes enclosed between bundles of collagen fibres.

•         Connective tissue

Ø  Intercellular substances or matrix:

Ø  Ground substance:

Ø  Biochemically complex & highly hydrated semisolid gel.

Ø  Glycosaminoglycans.

Ø  Numerous blood capillaries & lymphatic capillaries.

Ø  Decreases with age.

Ø  Classification of connective tissue

•         Types

1. Ordinary connective tissue:
1. Irregular connective tissue:
1. Loose connective tissue
2. Dense irregular connective tissue
3. Adipose tissue
2. Regular connective tissue

            Fasciae, ligaments, tendons & aponeurosis

1. Special connective tissue:
1. Mucoid tissue
2. Pigmented connective tissue
3. Bone &
4. cartilage

•         Types

1. Areolar tissue
2. Adipose tissue
3. White fibrous tissue
4. Elastic tissue
5. Reticular tissue
6. Mucoid tissue
7. Areolar tissue:

Distribution:

• Subcutaneous tissue where fat is absent: eye lid, scrotum, penis.
• Submucous coat of alimentary tract
• Subserous coat
• Interior of the viscera

2. Adipose tissue:

Distribution:

• Subcutaneous tissue as panniculus adiposus
• Around the kidney, in the mesenteries & omenta.
• In the bone marrow & as localized fat in synovial membrane.

3. White fibrous tissue:

Distribution:

• Ligaments
• Tendons
• Fascial sheaths

4. Elastic tissue:

Distribution:

• Ligamenta flva,
• Vocal folds & crico-vocal membrane,
• Mucous membrane of trachea, bronchi & lung alveoli,
• Coats of larger blood vessels.

5. Reticular tissue:

Distribution:

• Lymph nodes, spleen, liver, kidneys, lungs, bone marrow etc.

6. Mucoid tissue:

Distribution:

• Wharton’s jelly of the umbilical cord,
• Pulp of developing teeth,
• Vitreous body of eye ball.

•         Loose connective tissue

•         Fibrous tissue

1. Regular fibrous tissue or regular connective tissue: tendons, deep fascia, intermuscular septa, aponeuroses, central tendon of diaphragm, fibrous pericardium & dura mater.
2. Dense irregular tissue: dermis, connective tissue sheaths of muscles & nerves, capsules of glands, sclera, periosteum & adventitia of blood vessels.

•         Dense irregular connective tissue

•         Dense irregular & loose Connective Tissue

•         Dense Irregular Connective Tissue & Adipose Tissue

•         Dense regular connective tissue (L.S.)

•         L. S. through a tendon, showing the parallel organization of its collagen fibres. A few long, flattened Fibrocyte nuclei are also visible

•         Tendon L.S.

•         Dense regular connective tissue (T.S.)

Elastic tissue:

Ø  Bulk of connective tissue is formed by elastic fibers.

Ø  E.g. ligamentum flava, vocal ligaments of larynx.

Reticular tissue:

Ø  Made up of reticular fibers.

Ø  E. g. lymph nodes, glands, bone marrow, spleen.

•         Embryonic connective tissue

•         A section of fetal mesenchyme showing mucoid tissue sparsely populated with cells

•         Adipose Tissue

Structure:

Ø  An aggregation of fat cells, also called adipocytes.

Ø  Each fat cell contains a large droplet of fat that fills it.

Ø  Cytoplasm of the cell forms a thin layer just deep to the plasma membrane

Ø  Nucleus is pushed against the plasma membrane & is flattened.

•         Adipose Tissue

Distribution:

Ø  In superficial fascia over most of the body- panniculus adiposus, except superficial fascia of eyelids, scrotum & penis.

Ø  Fills several hollow spaces in the body, e. g. orbits, axilla & ischiorectal fossae. In adult much of the space in marrow cavities of long bones is filled by fat in the form of yellow bone marrow.

Ø  Around abdominal organs, specially the kidneys (perinephric fat).

Ø  In greater omentum & in other peritoneal folds.

•         Adipose tissue in intestine

•         EDEMA

Other causes:

1. Venous return may become impaired.
2. Lymphatics may become obstructed.
3. Permeability of capillaries may be increased.