Lecture 4

• What are the two different types of cells that are found in different connective tissues?


  • fundamental cell type
  • resident cell type
• What are cells in the immature form (connective tissue)?


  • -blast ("builder")
  • Actively dividing cells that secrete the ground substance and the fibers characteristic of their particular matrix.
  • e.g. osteoblast
• What are cells in the mature form (connective tissue)?


  • -cyte ("monitors")
  • Once they synthesize the matrix, the "blast cells" assume their less active mature mode.
  • Maintain health of matrix
  • If the matrix is injured they can revert back
  • e.g. osteocyte
• What other type of cells can be found in connective tissue?

  • Mast cells : inflammation
  • WBC: immune response
  • Macrophages: large phagocytising cells
  • *all part of immune system
• What are the 7 types of connective tissues? How are they classified?

  • Areolar connective tissue
  • Adipose connective tissue
  • Dense connective tissue
  • Elastic connective tissue
  • Cartilage
  • Bone tissue
  • Liquid connective tissue (blood tissue and lymph)
  • They are classified depending on the type of cells and of ECM BUT they all have similar function and build type
• What are areolar connective tissues?

  • Most widely distributed connective tissue in body
  • Contains several types of cells and all 3 types of fibers
  • Location: subcutaneous layer deep to skin, around blood vessels, nerves and organs
  • Functions: strength, elasticity, and support (maintain shape)
• What are adipose connective tissues?


  • Consists of adipocytes (store fat)
  • Adipose tissue is found wherever areolar tissue is located
  • Location: subcutaneous layer deep to skin, around heart and kidneys, padding around joints
  • Functions: insulation, energy storage, supports and protects (no bone for pelvic cavity)
• What are dense connective tissue?

  • Contains more numerous, thicker and denser fibers (mainly collagen) with fewer cells (fibroblasts)
  • Fibers arranged in patterns that provide tissue with great strength
  • Location: tendons (muscle to bone), ligaments (bone to bone)
  • Function: Provide strong attachment between structures
• What are elastic connective tissue?

  • Mostly elastic fibers and some fibroblasts
  • Strong and can recoil to original shape after stretching
  • Location: lung tissues, arteries
  • Functions: Allows stretching of various organs

  
• What are cartilage?

  • Dense network of collagen fibers and elastic fibers
  • Has no blood vessels
  • Stronger than dense con. tis. but not as strong as bone tis.
  • Location: joints between bone ("bumper"), rib cage, nose, ear
  • Function: provides smooth surface for movement of joints, gives support
• What are bone tissues?

  • Strongest tissue formed with collagen fibers embedded with mineral deposits and osteocytes (calcium and phosphorous salts)
  • Forms most of skeleton
  • Function: supports and protects, allows movement (attachment of muscle), storage of calcium and phosphorous, site of blood formation (bone marrow)

  
• What is blood?

  • Liquid ECM is the plasma (water, salts, dissolved proteins)
  • Contains no ground substance or fibers
  • Contains erythrocytes (RBC), leukocytes (WBC), platelets
  • Functions:
  • Transportation: water, gases, nutrients, hormones, enzymes, electrolytes, wastes, heat
  • Regulation: pH, temp. water balance
  • Protection: blood clotting, defense
  • Components
  • Plasma (55%): soluble material, top tube
  • Formed elements (45%): RBC and buffy coat (WBCs and platelets), bottom tube

  
• What are muscle tissue?

  • Tissues that are responsible for most types of body movement
  • Consists of long cells called muscle fibers that contract in response to nerve signals
  • Highly cellular
  • Well vascularized
  • Three types: smooth, cardiac, skeletal
• What are skeletal muscle tissue?

  • Skeletal muscle tissue is packaged by connective tissue sheets into organs called skeletal muscles
  • Voluntary movement
  • Attached to bones by tendons
  • Made of numerous muscle cells called muscle fibers
  • striated appearance from overlapping myosin and actin filaments

  
• What are cardiac muscle tissue?

  • Also striated but with branched cells that are joined together
  • Found in contractile wall of the heart
  • the darkly staining bands that join cardiac muscle cells together are called intercalated disks
  • the gap junctions of the intercalated disks allow direct communication between all of the cells in the heart so that the interconnected cells may contract in unison
  • INvoluntary movement

  
• What are smooth muscle tissues?

  • Lacks cross striations
  • Spindle shaped cells
  • Found in walls of bladder, digestive tract, arteries, and other internal organs
  • It acts to squeeze substances through these organs by alternatively contracting and relaxing
  • under non-voluntary rather than voluntary nervous control

  
• What are nervous tissues?

  • Functions: coordinate the body activities via nerve impulses
  • 2 types of nervous tissues:
  • Neurons: nerve cells (receive input and send output to other neurons, muscle fibers or glands)
  • Neuroglia: do not generate nerve impulses (responsible for maintenance)
• What are the 3 types of neuroglia?

  • Astrocytes: support neurons, remove waste, help maintain environment
  • Microglia: WBC of brain (clear away infection or dead cells)
  • Schwann cells: produce and maintain myelin sheath around axon of neuron (insulation of neurons)

  A) Myelin sheath

  B) astrocytes

  C) Microglia

  
• What is tissue repair?

  • process that replaces worn out damaged or dead cells
  • Epithelial cells originate from STEM cells
  • Bones regenerated readily
  • Cartilage does not regenerate easily (poor blood supply)
  • Muscular tissue can replace cells but slowly: skeletal does not divide rapidly enough, cardiac fibers can be produced by stem cells in lab, smooth fibers can regenerate but slowly
  • nervous tissue are the worst a repair (lab results show some stem cells present)