Chapter 4 Cell Proliferation, Tissue Regeneration and Repair

Pre Lecture Quiz True/False 1. Stem cells are undifferentiated cells that have the capacity to generate multiple cell types. 2. DNA synthesis takes place during the G0 phase of the cell cycle. 3. The inflammatory phase of wound healing prepares the wound environment for the healing process. 4. The formation of granulation tissue involves the creation of new capillaries. 5. A large surface wound is likely to heal by the process of primary intention.

Fill-in-the-Blank growth keloids matrix Scar Stable 1. _____________ tissues contain cells that normally stop dividing when growth ceases. 2. The extracellular _____________ is secreted locally and assembles into a network of spaces surrounding tissue cells during the process of tissue regeneration. 3. When regeneration cannot occur, healing by replacement with a connective tissue occurs, a process that terminates in ______________ formation. 4. The term _____________ factor is generally applied to small hormonelike proteins that increase cell size and cell division. 5. An abnormality in healing by scar tissue repair is the formation of _____________, which are benign tumorlike masses caused by excess production of scar tissue. growth keloids matrix Scar Stable

Cell Proliferation and Tissue Regeneration Parenchymal tissue Stromal tissue The working part The binding part

Cell Proliferation Versus Differentiation Cell proliferation-process of increasing cell numbers by mitotic division Cell Differentiation-process whereby a cell becomes more specialized in terms of structure and function

The Cell Cycle 4 distinct phases

Proliferative Capacity of Tissues Varies with tissue and cell type 3 divisions of body tissues: Continuously doubling Stable Permanent tissues

Stem Cells Incompletely differentiated throughout life 3 Properties: Self-renewal Asymmetric replication Differential potential (potency)

Influence of Growth Factors Small hormonelike proteins that increase cell size and cell division PDGF, FGF, TGF, and EGF

Extracellular Matrix and Cell-Matrix Interactions ECM is secreted locally and assembles a network of spaces surrounding tissue cells Components of ECM: Fibrous structural proteins Water-hydrated gels Adhesive glycoproteins

Components of the ECM

Healing by Connective Tissue Repair

Phases of Repair Angiogenesis and ingrowth of granulation tissue Emigration of fibroblasts and deposition of extracellur matrix Maturation and reorganization of the fibrous tissue (remodeling) Usually begins within 24 hours of injury; evidenced by the migration of fibroblasts and the induction of fibroblast and epithelial cell proliferation

Angiogenesis and Ingrowth of Granulation Tissue

Maturation and Remodeling of the Fibrous Tissue

Cutaneous Wound Healing The transition from granulation to scar tissue shifts in the modification and remodeling of the ECM

Healing by Primary and Secondary Intention Primary intention –sutured surgical incision Secondary intention- larger wounds which have a greater loss of tissue and contamination

Phases of Healing Inflammatory Phase Proliferative Phase Maturational or Remodeling

Keloids

Factors that Affect Wound Healing Nutritional Status Blood Flow and Oxygen Delivery Age

Nutritional Status Local and systemic factors influence wound healing Vitamin C and A play an essential role in the healing process Vitamin C is needed for collagen synthesis Vitamin A functions in stimulating and supporting epitheilial

Blood Flow and Oxygen Delivery For healing to occur, wounds must have adequate blood flow to supply the necessary nutriients and to remove waste, local toxins, bacteria and other debris.

Wound Healing in the Elderly Age-related changes: A decrease in dermal thickness A decline in collagen content Loss of elasticity Elderly are more vulnerable to chronic wounds, such as pressure, diabetic, and ischemic ulcers as compared to younger persons