connective tissue

• Connective Tissue


  • Most diverse group of tissues
  • Supports and binds tissues for all organs
• Proper connective tissue


  • General
• Mesenchyme


  • Loose and fluid type of embryonic tissue
  • Common origin of all connective tissue
• Mesenchymal cells


  • Small spindle shaped cells with large nuclei (multi potent stem cells)
  • Can be situated in any way and can move from place to place
• Multi potent stem cells


  • Common origin
  • Can differentiate
• Progenitor Cell


  • Origin of specific cells
  • Can develop for specific cells
• Unlike the epithelial cells which have fixed and neatly arranged in sheets
• Connective Tissue


  • Different degrees of vascularity (blood flow)
  • Its cells are separated by a large amount of intercellular space
• Extracellular Matrix (ECM)


  • Non-living component of connective tissues
  • Inert matrix (lacks the ability to move)
  • Transparent and colorless (because of water)
• Components of Extracellular Matrix

  • Ground Substance
  • Fibers
• Ground Substance


  • Watery, rubbery, unstructured material that fills the spaces between cells
  • Protects the cells in the extracellular matrix
  • Flexible – made of starch, protein molecules and water
• Components of Ground Substance

  • GAG or Glycosaminoglycans
  • Proteoglycans
  • Multi adhesive glycoproteins
• GAG or Glycosaminoglycans


  • Sprouts from proteoglycans
  • Mucopolysaccharides
  • Hyaluronan - largest most ubiquitous, molecular diffusion, lubrication
• Proteoglycans


  • Anchors this framework
  • Perlecan: basal laminae
  • Aggrecan: articular cartilage and most abundant; most important
• Fibers


  • Collagen
  • Elastic fibers
  • Reticular fibers
• Collagen fibers


  • Strongest and most abundant type, tough and flexible
  • Most abundant protein in the human body
• Elastic fibers


  • Longer and thinner which form a branching framework within the matrix
  • Made of protein elastin, allows them to stretch and recoil
  • Found in the skin, lungs and blood vessel walls
• Reticular fibers


  • Short, finer collagen fibers with an extra coating of glycoprotein
  • Forms a delicate, sponge-like networks that cradle and support the organs
• Collagen fibers appear neat and smooth "white, flexible" structures under the microscope
• Elastic fibers form a branching framework and stretch and recoil like rubber bands
• Reticular fibers are short, finer collagen fibers and form sponge like networks
• Blast


  • Literally means "forming"
  • Stem cells or immature cells
  • Undergoes mitosis to replicate themselves
  • Has different types with different functions
  • Once they mature, they transition from "–blast to –cyte"
• Chondroblast


  Blast cells of cartilage
• Osteoblast


  Blast cells of the bone tissue
• Macrophages


  • Provide immune defense for connective tissues, phagocytize bacteria, foreign materials and dead cells
  • More on the blood
  • Histiocytes - phagocytosis
• Connective Tissue Proper


  • Loose
  • Dense
• Loose Connective Tissue


  Have fewer fibers, and more cells and more ground substance
• Types of Loose Connective Tissue

  • Mesenchyme
  • Mucoid
  • Adipose
  • Reticular
• Mesenchyme


  Found in embryo, fetus
• Mucoid


  • Wharton's jelly or umbilical cord
  • Principle components of the umbilical cord
  • Ground substance: hyaluronan
• Adipose


  Subcutaneous tissue (dermis)
• Reticular


  Found in bone marrow, lymph node, spleen
• Types of Dense Connective Tissue

  • Regular
  • Irregular
  • Elastic
• Regular Dense Connective Tissue

  Collagen fibers are stacked neatly in regular rows
• Irregular Dense Connective Tissue

  • Collagen fibers are not stacked regularly in rows
  • Fibers are thicker and arranged erratically
  • Found wherever tension might be exerted in lots of different directions such as the leathery dermis under the skin
• Elastic Connective Tissue


  • Collagen with interwoven elastic fibers
  • Found in places in the body that requires more elasticity and rigidity such as around the joints, connecting the vertebrae so the spine can curve and twist, component of arteries – to provide support and flexibility
• Areolar Connective Tissue is the most common loose connective tissue, found all over the body under the epithelial tissues and wrapped around the organs, has a loose and random arrangement of fibers, few fibroblast cells, has a lot of open space, and is effective in holding the watery, salty ground substance
• Adipose Connective Tissue is fat tissue, the average person's weight is about 18% adipose tissue or fat stores, provides insulation against heat loss, provides fuel storage and keeps us alive during starvation or fastings, is mostly cells – adipocytes – which store lipids for later use
• Reticular Connective Tissue holds your blood cells in place in many of the blood forming organs, is similar to areolar tissue but with a woven mass of reticular fibers instead of collagen and elastin fibers, provides the soft internal framework or stroma of the spleen, lymph nodes and bone marrow, supports developing blood cells and holds your blood in place inside the organs