Lecture 2 - Pathophysiology of Acute Soft Tissue Injury

Question 1

Name the 3 initial results of injury.

Answer 1

Damage to cells (Mechanicsl, Chemical, Thermal etc)
Damage to extracellular structures
Damage to small blood vessels (triggers vascular responses and clotting response, drives inflammation)

Question 2

What is the cells response to injury?

Answer 2

Reversible - If injurious environment removed, cell returns to normal or the cell/s may be able to adapt to stress.
Irreversible - the cell dies and the clean up and inflammatory process is triggered.

Question 3

What determines whether injury is reversible or irreversible?

Answer 3

Type, severity and duration of injury, and the ability of the cells to adapt over time.

Question 4

What is hypoxia?

Answer 4

The lack of O2 present.

Question 5

What are the resultant effects of hypoxia?

Answer 5

Decreased aerobic production of ATP in mitochondria

Failure of NA+/K+ pump in membrane

Question 6

What are the mechanisms in which cells adapt to stress (structurally or functionally)?

Answer 6

Atrophy - reduced size/function
Hypertrophy - increased size/function or output
Hyperplasia - increased number

Question 7

What is the first line of defence to Injury and Infection?

Answer 7

Barriers - i.e. body surfaces such as skin, epithelial lining cells, mucous, perspiration, saliva, tears.

Question 8

Why do we have Inflammation as a reaction to injury?

Answer 8

It limits and controls damage, creates an influx of fluid and cells (i.e. WBCs/plasma proteins), initiates drainage into lymphatic vessels and initiates healing. Is good as long as its not ‘out of control’.

Question 9

Why do we have clotting as a reaction to bleeding?

Answer 9

A fast and local response to STOP bleeding - triggers inflammatory processes

Question 10

What are the 5 stages of Clotting?

Answer 10

1. Vessel spasm/Vasoconstriction - opposing cell walls contact and adhere
2. Platelet plug formation - platelets aggregate and adhere to each other
3. Blood coagulation
4. Clot retraction - clot hardens and becomes smaller
5. Clot dissolution - new cells grow to repair wound site, clot dissolves

Question 11

What is the Vascular Response to Injury?

Answer 11

1. Initial brief Vasoconstriction (allows clotting to commence)
2. Prolonged Vasodilation and increased blood flow
3. Increased Vascular permeability - fluid/plasma leaks into tissues where required.
   Results in:
   Increased concentration of RBCs and O2 within the vessel and increased WBCs in surrounding tissue

Question 12

What is Oedema?

Answer 12

Swelling - increased fluid in the tissues

Question 13

What is Chemotaxis (in regards to the chemical response to Injury)?

Answer 13

Where phagocytic cells are attracted to the injured area by chemical mediators. Makes the surrounding cells ‘sticky’ so WBC’s and platelets accumulate on vessel walls.

Question 14

What are the two WBCs that infiltrate in response to injury?

Answer 14

Neutrophils - predominant in the first 6-12 hours

Macrophages (from Monocytes) - after 24 hours

Question 15

What are the three Plasma Protein Systems that are key to an effective inflammatory response?

Answer 15

Complement System
Clotting System
Kinin System
All highly interactive

Question 16

What are Mast Cells?

Answer 16

They are a type of leucocyte found in most tissues of the body - when they recognize a pathogen they mediate an inflammatory response.

Question 17

Stimulation of Mast Cells causes what?

Answer 17

Degranulation - release of granules such as histamine

Synthesis - production of slower-acting histamine-like mediators of inflammation

Question 18

Name the different systems designed to initiate, moderate and complete the inflammatory process?

Answer 18

Vascular responses
WBC responses
Mast Cell Activation
Plasma Protein System Activation (incl Clotting)

Question 19

Cell death leads to Acute Inflammation, as well as clotting & Vascular Responses - True or False?

Answer 19

True

Question 20

Name 2 local effects of inflammation?

Answer 20

Calor (Hot)
Rubor (Red)
Tumour (Swollen)
Dolor (Painful)
Loss of function