Module 4: Tissue Regeneration & Repair

Parenchymal Cells

the functional parts of a tissue (mucosa in the stomach)

Stromal Cells

the supportive structural cells of a tissue or organ, usually underlying connective tissues

Tissue Regeneration

refers to the replacement of injured dead cells with the same type of cell to re-establish normal cellular conditions

Labile Cells

multiply constantly, always going through the cell cycle (skin, respiratory tract, bone marrow)

Stable Cells

will only multiply when they receive an external stimuli. Mostly not active in the cell cycle (liver, kidney tubular, endocrine gland)

Permanent Cells

don’t have the ability to multiply in the adult, incapable of regeneration (RBC, nervous tissue, cardiac muscle)

Epithelialization

epithelial cells proliferate along wound edges to form a new surface layer, can be stopped by dry/necrotic tissue and won’t be successful until there’s a layer of granulation tissue

Scab

hardened coagulated blood that fills the spaces between the wound edges

Primary Intention

no tissue loss, closed with stapes and sutures

Secondary Intention

tissue loss, no sutures or staples

Tertiary Intention

tissue loss, closed with sutures or staples after being left open for days

Phases of wound healing

inflammatory phase, proliferative phase, wound contraction & remodeling phase

Inflammatory phase

blood clot formation is the first priority when there’s a wound that penetrates beyond epithelium. 1-5 days in this phase. invasion of phagocytic cells (neutrophils) followed by macrophages. production of growth factors. attract fibroblast and induce blood vessel formation from other blood vessels (angiogenesis).

Proliferative phase

2-3 days after injury. fibroblasts secrete collagen, proteoglycans, growth factors. formation of granulation and vascular tissue. epithelialization. scab forms.

Wound contraction and remodeling phase

3 weeks-6+ months depending on size of the wound. continual remodeling of fibrous scar tissue (granulation tissue that’s hardened with collagen). constant turnover of collagen tissue to increase tensile strength of wound. this is done by the secretion of collagen by fibroblasts & lysis of collagen by collagenous enzymes. over time scar shrinks.