Chapter 10: Tissue Response to Injury

Question 1

What are the three phases of healing and what are the time frames associated with them?

Answer 1

Inflammatory response (date of injury to day 4), Fibroblastic repair (day 4 to 6 weeks), maturation (week 6 to 2-3 years)

Question 2

What are the chemical mediators and what do they do?

Answer 2

Histamine: released from injured mast cells, causes vasodilation & increases cell permeability, allows swelling and separation of endothelial cells and
Leukotrienes: and prostaglandins are responsible for margination…where leukocytes (neutrophils and macrophages) adhere to the cell walls, increase cell permeability locally, affects fluid passage through cellwalls via diapedesis (move WBC out of small arterial vessels) & form exudate
Cytokines: chemokines & interleukin are primary regulators of leukocyte traffic, help phagocytes to the site of inflammation

Question 3

What is the pattern of blood clotting & how long after the injury does it occur?

Answer 3

Convert fibrogen to fibrin due to release of thromboplastin to create a sticky fibrin clot (2-4 days)

blood coagulation: thromboplastin to prothrombin to thrombin to fibrinogen to insoluble fibrin clot

Question 4

What is granulation tissue?

Answer 4

Fibroblasts, collagen (strong, fibrous protein in connective tissue), & capillaries

Question 5

What is fibroplasia?

Answer 5

The period of scar formation, beginning within the first few days after injury

Question 6

What is the difference between a macro & microtear?

Answer 6

A microtear occurs from overuse with minor damage, a macrotear occurs from acute trauma

Question 7

What are keloids?

Answer 7

Scars that occur when the rate of collagen production exceeds the rate of collagen breakdown during maturation. This leads to hypertrophy of scar tissue.

Question 8

What effect does humidity have on tissue healing?

Answer 8

Influences the process of epithelization. Helps b/c moisture allows necrotic debris to go more easily to the surface to be shed.

Question 9

What affect do Vitamins K, C, and A have on tissue healing?

Answer 9

Vitamin C helps with collagen synthesis and immune system; Vitamin K helps with clotting, and Vitamin A helps with the immune system

Question 10

What is Wolff’s Law?

Answer 10

Bone and soft tissue will respond to the physical demands placed on them, causing them to remodel or realign along lines of tensile force

Question 11

What is metaplasia?

Answer 11

Conversion of one kind of tissue into a form that is not normal for that tissue

Question 12

What is dysplasia?

Answer 12

Abnormal development of tissue

Question 13

What is Hyperplasia?

Answer 13

Excessive proliferation of normal cells in the normal tissue arrangement

Question 14

What is atrophy?

Answer 14

A decrease in the size of tissue due to cell death & reabsorption or decreased cell proliferation

Question 15

What is hypertrophy?

Answer 15

An increase in the size of a tissue without necessarily increasing the number of cells

Question 16

What is the difference between a sclerotome, dermatome, and myotome?

Answer 16

Sclerotome: area of bone or fascia that is supplied by a single nerve root…pain is deep, aching and poorly localized, vasomotor tone changes, blood pressure and sweating may happen
Myotomes: muscles supplied by a single nerve root
Dermatomes: in an area of skin supplied by a single nerve root, sharp, well localized, to thalamus

Question 17

What is the gate control theory?

Answer 17

Pain messages from the nocioceptors are carried along A and C afferent fibers, along with sensory info from AB afferent. Sensory info overrides or inhibits the pain info, thus “closing the gate” to the pain transmission info. Pain info is not transmitted and never reaches sensory centers in the brain. Occurs at the spinal cord level.

Question 18

What is central biasing theory?

Answer 18

The body uses past experiences with pain to judge the intensity/severity of current pain. It is used on sharp chronic pain or severe pathological pain.”

Question 19

What are the four types of soft tissue?

Answer 19

epithelial, connective, muscle, and nervous

Question 20

Cartilage healing

Answer 20

relatively limited. fail to elicit clot formation or a cellular response. healing is dependent on damage to cartilage alone or also to subchondral bone.

Question 21

Ligament healing

Answer 21

immediately after injury and for approx. 72 hours, there is a loss of blood from damaged vessels and an attraction of inflammatory cells into the injured area. bleeding does occur. next 6 weeks, vascular proliferation with new capillary growth begins to occur, along with fibroblastic activity. essential that ends are bridged before healing can begin. scar will initially be soft and viscous but will then become more elastic. maturation may take as long as 12 months to complete.

Question 22

Muscle healing

Answer 22

initially, there will be hemorrhage and edema followed almost immediately by phagocytosis to clear debris. a few days there is a proliferation of ground substance. myoblastic cells (satellite cells) form in the area of injury which will eventually lead to the regeneration of new myofibrils. collagen fibers undergo maturation and orient themselves along lines of tensile force. active contraction of the muscle is critical in regaining normal tensile strength. the time is rather lengthy. the treatment of hamstring strains requires a healing period of at least six to eight weeks. returning too soon will cause reinjury.

Question 23

Tendon healing

Answer 23

pose a problem - requires dense fibrous union of the separated ends and both extensibility and flexibility at the site of attachment. abundance of collagen is required to achieve good tensile strength. unfortunately, collage synthesis can be excessive and cause adhesions that interfere with the gliding of smooth motion. if this occur where the tendon is surrounded by a synovial sheath it can be potentially devastating. second week healing adheres to surrounding tissue. third week, tendon separates. four to five weeks, tensile strength becomes more sufficient.

Question 24

Nerve healing

Answer 24

cannot regenerate once the nerve cell dies. peripheral nerve cells can regenerate significantly if the injury does not affect the cell body though. closer to cell body the more difficult it is. within 3-5 days, the portion of the axon distal to the cut begins to degenerate and breaks into irregular segments. if proximal end does not contact with schwann cells, reinnervation will not occur. regeneration is slow, only 3-4 millimeter per day.

Question 25

Bone healing

Answer 25

somewhat limited, many forces affect healing including torsion, bending, and compression. hemorrhaging from the marrow is contained by the periosteum and the surrounding soft tissue in the region of the fracture. in about a week, fibroblasts have begun to lay down. fibrin strands within the clot serve as the framework for proliferating vessels. chondroblast cells begin producing firbrocartilage, creating a callus between the broken bones. finally callus crystallizes into bone and remodeling begins. immobilization between 3-8 weeks. osteoblastic/clastic activity may continue for 2-3 years after severe fractures

Question 26

acute v chronic paina

Answer 26

acute: less than six months
chronic: longer than six months