Connective Tissue

Connective Tissue Overview

• Definition: A tissue mostly made of extracellular matrix, primarily secreted by connective tissue cells.

• Function: Provides and maintains the body’s structural form.

Functions of Connective Tissue

1. Mechanical Support:

• Supports the internal structure of organs.

• Has regenerative capacity for tissues that can’t regenerate (e.g., cardiac muscle), by replacing damaged areas with connective tissue.

2. Nutritional Support:

• Contains blood vessels for nutrient, metabolite, and waste exchange.

3. Defense:

• Contains immune cells (macrophages, plasma cells, leucocytes) for protection against infections.

Components of Connective Tissue

1. Cells:

• Fibroblasts: Main cells, synthesize fibers and healing substances.

• Undifferentiated Mesenchymal Cells: Stem cells that can repair tissue.

• Plasma Cells: Produce antibodies for immune response.

• Macrophages: Engulf foreign particles, also present in various forms (e.g., Kupffer cells in the liver).

• Mast Cells: Contain granules like heparin and histamine, which aid in defense and allergic reactions.

• Fat Cells (Adipocytes): Store fat, provide insulation and support.

2. Fibers:

• Collagen Fibers: Provide strength, located in skin, bones, and tendons.

• Reticular Fibers: Form networks in organs like the spleen and liver.

• Elastic Fibers: Found in the lungs and arteries, they stretch and recoil.

3. Ground Substance:

• Fills spaces between cells and fibers, helping bind them together.

• Types include soft (viscid, like synovial fluid) and firm (like cartilage).

Types of Connective Tissue

1. Connective Tissue Proper:

• Loose (Areolar): Most common, allows movement, found in cavities.

• Dense: Provides mechanical strength, found in skin and tendons.

2. Special Connective Tissues:

• Elastic: High in elastic fibers, in places needing flexibility (e.g., aorta).

• Mucous: Jelly-like, found in the umbilical cord.

• Adipose: Stores fat; includes yellow/white fat and brown fat, mainly formed after birth.

3. Supporting Connective Tissues:

• Includes cartilage and bone for structural support.