Week 2 Pathology - Inflammation, Healing and Repair

Question 1

What are the major features of acute inflammation?

Answer 1

1) Alterations in vascular calibre, leading to increased blood flow
2) Structural changes in microvasculature to permit plasma proteins and leukocytes to leave the circulation
3) Emigration of leukocytes from microcirculation to accumulate at focus of injury and eliminate offending agent

Question 2

What are typical stimuli for acute inflammation?

Answer 2

Infection, necrosis, foreign bodies, immune reactions

Question 3

What is an exudate?

Answer 3

Extravascular fluid high in protein concentration, with cellular debris and high specific gravity

Question 4

What is a transudate?

Answer 4

Extravascular fluid low in protein concentration, with little specific gravity

Question 5

What is oedema?

Answer 5

Excess fluid in the interstitial space, either can be exudative or transudative in origin

Question 6

What inflammatory mediators induce vasodilation?

Answer 6

Nitrous Oxide
Histamine

Question 7

What inflammatory mediators are responsible for increased vascular permeability ?

How long does this occur for?

Answer 7

Histamine, leukotrienes, bradykinin, neuropeptide P

15-30 mins

Question 8

How does inflammation lead to slower blood flow in microvasculature?

Answer 8

Slower blood flow occurs due to loss of fluid, concentration of RBCs in small vessels, and accumulation of leukocytes along endothelium (due to expression of adhesion molecules which facilitate migration into the interstitial fluid)

Question 9

What cells are responsible for the release of cytokines, predominantly TNF, IL-1?

Answer 9

Macrophages
Endothelial cells
Mast Cells

Question 10

What cells are responsible for the release of vasodilatory and permeability mediators prostaglandins, histamine, leukotrienes, platelet activating factor?

Answer 10

Mast cells
Leukocytes

**Basophils also secrete histamine

Question 11

What are the outcomes of acute inflammation?

Answer 11

1) Complete resolution: removal of cellular debris by macrophages and reabsorption of oedema by lymphatics
2) Healing by connective tissue replacement (more substantial tissue destruction) - cells incapable of regeneration
3) Progression to chronic inflammation –> acute inflammatory response cannot be resolved either by persistence of injurious agent or interference with normal healing process

Question 12

What are the key features of chronic inflammation?

Answer 12

1) Infiltration with mononuclear cells (macrophages, lymphocytes, plasma cells)
2) Tissue destruction caused by persistent offending agent
3) Fibrosis and angiogenesis

Question 13

What is the predominant cell type in chronic inflammation?

Answer 13

Monocytes, differentiating into macrophages

Question 14

What are the two key roles of macrophages?

Answer 14

Eliminate injurious agents
Initiate process of repair

Question 15

What other cell types are present in chronic inflammation?

Answer 15

Lymophocytes
Plasma cells
Eosinophils
Mast cells

Question 16

What is the immediate response to a wound?

Answer 16

Rapid activation of coagulation pathways and formation of blood clot on wound surface, forms a scaffold for migrating cells which will participate in repair

Question 17

What occurs within 24 hours of wound?

Answer 17

Neutrophil invasion of incision margin, migrates to fibrin clot

Question 18

What occurs 24-48 hours of wound?

Answer 18

Epithelial cells from both edges begun to proliferate along dermis, and meet in the midline underneath surface scab, forming epithelial layer which bridges the wound

Question 19

What type of collagen is deposited first, and what is it replaced by?

Answer 19

Initially, Type III - but replaced later by type I collagen

Question 20

What occurs by day 3?

Answer 20

Neutrophils largely replaced by macrophages, epithelial cells continuing to proliferate and form a covering nearing thickness of epidermis

Question 21

What occurs by day 5?

Answer 21

Neovascularisation reaches its peak, granulation tissue fills the incisional space, with leaky vessels allowing plasma proteins and fluid into extravascular space. Fibroblasts drawn into wound

Question 22

What occurs in week 2 of a wound?

Answer 22

Continued collagen accumulation and fibroblast proliferation, but reduction in leukocytes, oedema, and vascularity

Question 23

Contrast primary and secondary intention?

Answer 23

Primary = involving epithelial layer, principle mechanism is epithelial regeneration

Secondary = more extensive tissue loss, combination of regeneration and scarring - with greater amount of granulation tissue required, with associated wound contracture of scar to reduce surface area of wound

Question 24

What types of cells are known as ‘labile’ or continuously dividing tissues?

Answer 24

Haematopoetic cells in bone marrow
Stratified squamous epithelia
Cuboid epithelia of endocrine organ ducts
Columnar epithelium of GIT, uterus, fallopian tubes
Transitional epithelium of urinary tract

Readily regenerate as long as pool of stem cells preserved

Question 25

What cells are known as ‘stable tissues’ and have limited capacity to regenerate?

Answer 25

Solid parenchymal organs, ie kidney, liver, pancreas

Question 26

What cells are permanent tissues?

Answer 26

Brain, heart

Question 27

What are the 5 steps to bone healing?

Answer 27

1. Haematoma (hours)
2. Influx of inflammatory cells, fibroblasts, and new blood vessels (24 hours)
3. Procallus formation
4. Ossification (2-3 weeks)
5. Remodelling (6 weeks + )

Question 28

What factors affect wound healing?

Answer 28

Infection
Nutrition (protein and vitamin deficiency)
Glucocorticoids
Mechanical factors
Poor perfusion
Foreign body
Diabetes

Question 29

What are key features on assessment of a fracture?

Answer 29

1) Open vs closed
2) Intra vs extra-articular
3) Neurovascular status
4) Swelling/skin condition