Shared Flashcard Set


Chapter 4 Healing

Additional Physiology Flashcards




Define healing

Replacement of injured or dead tissue


Body must do this to survive

What is the difference between regeneration and repair

Both are healing processes.


Regeneration: Uninjured parenchymal (functional) cells may replicate to replace injured cells if stroma (connective tissue and blood vessels) is not injured.  Function is restored, no scarring, can occur if parenchymal cells can replicate.


Repair: When lost parenchymal cells cannot replicate and be replaced.  Replacement by fibrous connective tissue called repair by fibrosis.  Scar formation occurs with possible impairment of tissue function.

labile/mitotic cells

continously dividing


examples: bone marrow, epithelia of skin, mucosa of GI tract


these can usually replace lost cells

healing by regeneration can usually occur

stable/quescient/facultative cells

replicate at slow rate


examples: most glands, liver, smooth muscle, osteoblasts, vascular endothelial cells


these can usually replace lost cells

healing by regeneration can usually occur

permanent/nondividing cells

do not divide after birth


examples: neurons, cardiac muscle, skeletal muscle


healing by regeneration cannot occur

healing is by repair and fibrosis

Describe healing by repair and fibrosis
  1. tissue damage, bleeding, clot formation
  1. around clot, formation of exudate, which becomes organized, new blood vessels form, resulting in granulation tissue
  1. phagocytes eliminate clot
  1. fibroblasts in granulation tissue make procollagen which is organized into collagen fiber bundles outside of cell
  1. ECM strengthens collagen

removal of clot and replacemtn by fibrous scar tissue is called reorganization


Describe the process of revascularization/angiogenesis

Regeneration of blood supply to injured area, whether healing by regeneration or by repair.


endothelial cells from undamaged vessels form buds that elongate.-may contact parent vessel to form new channel

-may contact bud from another parent to form new channel

-may become isolated and degenerate.


new blood vessels are slowly modified into arterioles, venules, capillaries


healing region needs more blood vessels, after healing reabsorption of blood vessels and paler appearance of tissue 


Innervation by vasomotor neurons


Lymphatic vessels similarly regenerate

Describe the process of surface restoration for a skin or organ wound

zone of active mitosis of epithelial cells develops at edge of wound


these cells migrate across surface of granulation tissue or in case of minor skin abrasion, across surface of intact dermis


these cells secrete new basement membrane


after closing of gap, new cells move vertically to surface to restore normal arrangement

Describe healing of a wound by primary intention

This occurs where wound is clean and edges are close together (e.g. surgical incision).


Healing by repair and fibrosis, angiogenesis and restoration occurs.


Additionally, granulation tissue appears in 2-3 days, fibroblasts in granulation tissue make procollagen organized into collagen fiber bundles outside of cell, ECM strengthens collagen, and there is realignment of collagen fibers after about 6th day, increasing strength.


Surface restoration is occurring.  If a skin wound: keratinocytes of epidermis produce new keratin, which loosens scab, melanocytes of epidermis do not regenerate, scar area is pale


By 2nd week, changes in granulation tissue, fewer phagocytes, reabsorpion of blood vessels


Continued remodeling of collagen for about 3 months to maximal strength of scar, about 70-80% of normal.

How does healing of wound by secondary intention differ from healing by primary intention?

Healing by secondary intention occurs with larger wounds with edges not close together or infection presence of foreign bodies in wound.


examples: Lage, dirty, or infected skin wounds, peptic ulcer in GI tract


Healing is similar to primary intention but healing is slower, much more inflammation and formation of granulation tissue, many more fibroblasts are involved to close defect.


Since wounds must contract, myofibroblasts attach to edges of wound and contract, begins 2-3 days after injury


Shape of final scar is different than original wound due to this contraction.  Circular wound does not fully close.

Describe healing of a bone fracture

Bone is a connective tissue, therefore, prolonged healing due to limited blood supply


Medical intervention for reduction and immobilization of fracture site.


1st stage of healing: 4-5 days after fracture

-removal of blood and debris between bone ends

-formation of granulation tissue, blood vessels, activation and migration of osteoblasts to fracture area


2nd stage of healing: occurs over next 3 weeks

-osteoblasts make collagen and cartilage, stabilizes fracture, tissue is called osteoid/soft callus

-osteoid is ossified by osteoblasts to form hard callus (healing area is now enlarged but structurally weak)


3rd stage of healing: extends over months - years

-osteoblasts and osteoclasts remodel hard callus to restore normal bone structure

What type of tissue are cartilage and adipose tissue and how does healing occur in these tissues?

Connective tissue and healing is prolonged due to limited blood supply.


cartilage: healing by fibrous repair, fibroblasts of perichondrium produces scar tissue, some loss of function


adipose tissue: cells cannot divide, but precursor cells produce new adipose cells, fibrosis does not occur

Why do epithelial tissue quickly heal by regeneration

Mostly made up of labile cells


examples: epithelia of epidermis, mucous membranes, respiratory surfaces, other body surfaces


Regarding respiratory/lung surfaces: epithelia can regenerate with superficial injury but fibrosis and scarring if basement membrane and ECM are damaged

How do most grandular tissues, such as liver and kidney heal with minor injury, more extensive injury and with even more sever, sustained injury?

Most glands are made up of quiescent/stable cells, therefore can readily regenerate with minor injury.


More extensive injury: regeneration with some loss of normal structure and function


Severe, sustained injury: 

-loss of parenchymal, stroma, ECM

-contracted scar tissue

-loss of function with irregular surface depressions


Which grandular tissue cannot heal by regeneration?
  • Parathyroid
  • Adrenal Medulla
  • Posterior pituitary
How does healing occur in the brain?

No mitosis is possible in nervous tissue.


Replacement of damaged neurons by neuroglia called gliosis, which can block axon regeneration

How does regeneration of peripheral nerves occur?

In peripheral nervous system: regeneration of cut nerve process (axon/dendrite) can occur if supporting connective tissue and Schwann cells are intact


After cut: degeneration of process and myelin sheath distal to cut, injured Schwann cells are replaced and follow original path


New sprout from process finds canal formed by Schwann cells and connective tissue, grows along this path to reinnervate muscle or other structure

What is a traumatic neuroma

If larger nerve is severed and if ends remain seperated, THEN regenerating processes may grow into new scar tissue to form traumatic neuroma.

How does healing occur in the 3 types of muscle tissue?

Cardiac and skeletal muscle cells: Cannot regenerate, fibrous repair with injury, possible compensation with hypertrophy


Smooth muscle cells: Some regeneration is possible, sometimes healing by fibrous repair

List factors that may delay healing and repair
  • large size of wound
  • tension
  • infection
  • poor blood flow
  • advanced age
  • poor nutrition
  • movement
  • diabetes
  • corticosteroid use
List 5 complications of wound healing

deficient scar formation: opening of healing wound


excess scar formation: exuberant granulation, keloids


contractures:large scars can interfere with movement


adhesions: union of 2 membranes that normally move freely against each other

exuberant granulation

"proud flesh"

too much granulation tissue


protrusion of irregular scar tissue from skin surface due to overproduction of collagen


excessive production or sensitivity to TGF-B


What are requirements for proper healing?

clearance of debris


adequate blood supply


Supporting users have an ad free experience!