Connective Tissue

• What is the most abundant and widely distributed tissue in the body?

  Connective tissue
• What are the main functions of connective tissue?


  • Binds structures
  • Supports organs
  • Site of immunological reactions
  • Protects organs
  • Envelopes structures
• What are the characteristic features of connective tissue (CT)?

  1. Abundant matrix with few cells
  2. Cells are scattered, not bound
  3. Does not usually occur on free surfaces
  4. Has a nerve supply (except cartilage)
  5. Highly vascular (except cartilage, tendons, ligaments)
• What are the main components of connective tissue (CT)?


  1. Cells
  2. Extracellular matrix

  • Ground substance
  • Fibers
• What is the composition of the ground substance in connective tissue?

  • Proteoglycans (main constituent)
  • Gelatinous characteristic
  • Core protein and glycosaminoglycans (GAGs)
• What are the five types of glycosaminoglycans (GAGs)?


  1. Hyaluronic acid (most abundant)
  2. Keratan sulfate
  3. Chondroitin sulfate
  4. Dermatan sulfate
  5. Heparan sulfate
• What are the types of connective tissue fibers?

  1. Collagen
  2. Reticular
  3. Elastin
• What is the primary function of connective tissue fibers?


  To provide strength and support
• What are the characteristics of collagen fibers?


  • Resemble microscopic ropes (in bundles)
  • Acidophilic (pink)
  • Flexible and tough
  • Made of type 1 collagen
  • Present in all connective tissue
• What are the characteristics of reticular fibers?


  • Fine, short collagen (type 3) fibers
  • Coated with glycoprotein
  • Branch to form a supporting network
• What are the characteristics of elastic fibers?


  • Resemble fine coiled metal bed springs
  • Yellow in fresh tissue
  • Basophilic (blue/black)
  • Made of elastin
• What are the resident cells of connective tissue?

  1. Fibroblast
  2. Fibrocyte
  3. Macrophages
  4. Mast cells
  5. Reticular cells
  6. Adipocytes
• What is the function of fibroblasts in connective tissue?


  They make ground substance and fibers
• What is the role of macrophages in connective tissue?


  They destroy microorganisms
• What do mast cells release in connective tissue?


  Histamine that promotes inflammation
• What are the visiting cells in connective tissue?


  1. Inflammatory macrophages
  2. Plasma cells
  3. Leukocytes
• What is the function of plasma cells in connective tissue?


  They produce antibodies
• Where are mesenchymal cells found?


  In bone marrow, capillaries, and umbilical cord
• What are the types of connective tissue proper?


  1. Dense (regular, irregular, elastic)
  2. Loose (areolar, adipose, reticular)
• What are the characteristics of areolar (loose) connective tissue?


  • Highly vascular
  • Abundant extracellular substance
  • Haphazard fiber arrangement
  • More cellular than dense connective tissue
• What are the functions of adipose connective tissue?


  1. Energy storage
  2. Thermal insulation
  3. Shock absorption
• What are the characteristics of dense regular connective tissue?


  • Closely packed and parallel collagen fibers
  • Few cells and scanty extracellular substance
• What are the functions of dense irregular connective tissue?


  1. Provides tensile strength in many directions
  2. Supports various organs
• What is the function of elastic connective tissue?


  1. Allows stretching of organs
• What are the characteristics of cartilage?


  1. Few cells
  2. Large quantities of extracellular matrix
  3. Avascular
  4. Aneural
  5. (+) Perichondrium
  6. Strong, firm material that resists tension, compression, and shear
• What are the components of cartilage?

  1. Chondroblasts
  2. Chondrocytes
  3. Cartilage matrix (water, fibers, proteoglycans, GAGs)
• What are the types of cartilage formation?


  1. Interstitial (endogenous) growth
  2. Appositional (exogenous) growth
• What is the perichondrium?


  • Envelops almost all cartilages (except articular cartilage)
  • Dense irregular connective tissue
  • Contains two layers
• What is chondroitin sulfate?


  A type of glycosaminoglycan (GAG) found in cartilage
• What are the three types of cartilage?


  1. Hyaline
  2. Elastic
  3. Fibrocartilage
• What are the characteristics of cartilage?


  • Few cells
  • Large quantities of extracellular matrix
  • Avascular
  • Aneural
  • (+) Perichondrium
  • Strong, firm material that resists tension, compression, and shear
• What are the components of cartilage?


  Chondroblasts, chondrocytes, and cartilage matrix
• What is the function of chondroblasts?


  They synthesize the organic constituents of the cartilage matrix and precursors of fibers
• Where are chondrocytes located?


  They are lodged in lacunae
• What is the composition of the cartilage matrix?


  Water, collagen fibers, elastic fibers, proteoglycans, and GAGs
• What are the two types of cartilage formation?


  Interstitial (endogenous) growth and appositional (exogenous) growth
• What is the perichondrium?


  • Envelops almost all cartilages (except articular cartilage)
  • Dense irregular connective tissue
  • Contains two layers: outer fibrous layer and inner chondrogenic layer
  • Contains stem cells (chondroblast or osteoblast)
• What are the characteristics of hyaline cartilage?


  • Most abundant cartilage
  • Contains type II collagen
  • Fresh specimen: glistening, smooth, and pearly white
  • H & E prep: collagen fibers indistinguishable from ground substance
• Where can hyaline cartilage be found?


  Epiphyseal plate, fetal skeleton, articular cartilage, trachea, bronchi, and ribs
• What are the characteristics of elastic cartilage?


  • More flexible than hyaline cartilage
  • Made of elastin and type II collagen
  • Fresh specimen: yellowish