Notes on Connective Tissue
Introduction to Connective Tissue
- Connective tissue is the most abundant tissue type in the body.
- Its functions include:
- Binding
- Support
- Protection
- Insulation
- Storage
- Transportation of substances
Types of Connective Tissue
The four main types of connective tissue are:
- Connective tissue proper
- Cartilage
- Bone
- Blood
Common Features
- All connective tissues are derived from mesenchyme (embryonic tissue).
- Comprised of:
- Cells
- Extensive extracellular matrix (ECM)
Components of Connective Tissue
-
Ground Substance
- Fills space between cells and connects fibers
- Made up of:
- Interstitial fluid
- Cell adhesion proteins
- Proteoglycans
-
Fibers
- Collagen Fibers
- Strongest fibers, made of collagen
- Strands are stronger than steel
- Elastic Fibers
- Long and thin, made of elastin
- Form networks for elasticity
- Reticular Fibers
- Similar to collagen but form networks
-
Cells
- Can be mature (ending in "cyte") or immature (ending in "blast")
- Immature cells secrete ground substance and fibers
- Examples:
- Connective tissue proper: fibroblasts
- Cartilage: chondroblasts
- Bone: osteoblasts
- Blood: hematopoietic stem cells
Types of Connective Tissue Proper
1. Loose Connective Tissue
- Areolar
- Abundant, wraps around structures, stores tissue fluid
- Adipose
- Composed of fat cells, stores nutrients, insulates
- Reticular
- Similar to areolar but consists only of reticular fibers
2. Dense Connective Tissue
- Regular
- Collagen fibers packed tightly, resists tension (tendons, ligaments)
- Irregular
- Random arrangement of collagen fibers, resists tension in multiple directions
- Elastic
- Similar to regular but more elastic
Cartilage
- Intermediate between dense connective tissue and bone
- Lacks nerve cells and blood vessels
- Nutrients diffuse from nearby tissues
- Contains tissue fluid for compression resistance
- Types of Cartilage:
- Hyaline Cartilage
- Most abundant, firm yet amorphous, reinforces structures
- Elastic Cartilage
- More elastic fibers, found in ear
- Fibrocartilage
- Alternates rows of chondrocytes and collagen fibers, found in vertebral discs
Bone
- Osseous tissue, harder than cartilage
- Matrix contains collagen and inorganic calcium salts
- Contains blood vessels, unlike cartilage
Blood
- Fluid connective tissue, does not connect/support but develops from mesenchyme
- Composed of blood cells surrounded by plasma
Conclusion
- Two additional tissue types: muscle tissue and nervous tissue
- These will be discussed later when detailing the muscular and nervous systems.