Connective Tissue Part II

Study Notes

Connective tissue (CT) consists of fibers and ground substance forming the extracellular matrix (ECM).
Major fiber types: white collagenous fibers, reticular fibers, yellow elastic fibers.

Collagen Fibers:
- Most abundant protein, constituting 30% of the body's dry weight.
- More than 25 types exist, including types I, II, II, IV.
- Synthesized by fibroblasts, chondroblasts, osteoblasts, and odontoblasts.
- Precursor called tropo-collagen, built from glycine, proline, hydroxyproline, and hydroxylysine.
- Vitamin C essential for normal collagen synthesis.
- Characteristics: strong, resistant, flexible, white in fresh state.
- Functions include providing strength and resisting stretch. Common in ligaments and tendons.
Elastic Fibers:
- Comprised of elastin and fibrillin.
- Synthesized by fibroblasts and other cells (e.g., smooth muscle, chondroblasts).
- Characteristics: stretchable, elastic, yellow in fresh state.
- Functions: provide elasticity; found in some ligaments and the walls of large arteries (e.g., aorta).
Reticular Fibers:
- Formed from collagen type III.
- Synthesized by reticular cells.
- Characteristics: branched, forming a network, stained black with silver.
- Functions: supportive framework, forming the stroma of organs.

Extracellular material embedding CT cells and fibers.
Colorless, transparent, produced by fibroblasts.
Composed of glycosaminoglycans (GAGs), proteoglycans, glycoproteins, and tissue fluid.
Functions include acting as a medium for transport and as a physical barrier against infections.

General Connective Tissue: Soft, gel-like matrix.
Specialized Connective Tissue: Includes:
- Cartilage (rubbery matrix)
- Bone (solid/hard matrix)
- Blood (fluid matrix)

Loose Connective Tissue (more cells than fibers):
- Areolar CT: Most common, gel-like matrix, supports epithelial cells.
- Adipose CT: Primarily fat cells; two types:
  - White (uni-locular): Stores and mobilizes fat; found in subcutaneous tissues and around organs.
  - Brown (multi-locular): Involved in energy and heat production; found in newborns around the neck and thorax.
- Reticular CT: Comprised of reticular fibers and cells; provides structural support in bone marrow and various organs.
- Mucoid CT: A type of loose connective tissue with a gelatinous matrix.
Dense Connective Tissue (more fibers than cells):
- Regular Fibrous CT: Well-organized fibers; found in tendons and ligaments.
- Irregular Fibrous CT: Fibers arranged randomly; provides strength in multiple directions.
- Yellow Elastic CT: Contains elastic fibers; found in certain ligaments and elastic tissues.

Collagen fibers offer strength and resist stretching, prevalent in ligaments and tendons.
Elastic fibers provide elasticity, notably in large arterial walls.
Reticular fibers create supportive frameworks in organs and bone marrow.
Loose connective tissues serve as supportive structures beneath epithelium and around blood vessels.