Infection

Question 1

Infection

Answer 1

Occurs through invasion of body by pathogenic micro-orgnisms
Eg:
Bacteria
Viruses
Fungi
Protozoa
Parasites

Question 2

Invasion (routes of entry)

Answer 2

Skin + Mucous membranes
Ingestion
Inhalation

Question 3

Establishing factors of infection

Answer 3

To cause disease organisms have to overcome body’s defense mechanisms
Infection is aided by
Quantity
Virulence [resistance to phagocytosis, adhesiveness, co-enzyme production]

Question 4

Defence mechanisms against infection

Answer 4

Physical barriers - skin + filtration (nasal cilla)
Secretions - tears, urine + mucin
Chemical actions

Question 5

Chemical defence mech

Answer 5

Acid - stomach + urinary tract
Lysozyme enzymes - dissolve bacterial capsule in tears
IgA - tears and GI
Non-specific - urine, sweat, sebum

Question 6

IgA

Answer 6

Immunoglobulin A
- any of a class of proteins present in the serum and cells of the immune system, which function as antibodies.

Question 7

Lysozyme

Answer 7

enzymes that damage bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages

Question 8

Factors in the course of infection

Answer 8

Acute Inflamm limits spread
Chronic Inflamm (Fibrosis) localize infection
Phagocytosis - can fail with multiplication within phagocyte
Immune response
Interferon production (IFN)

Question 9

Interferons

Answer 9

Interferons (IFNs) are a group of signaling proteins[1] made and released by host cells in response to the presence of several pathogens, such as viruses, bacteria, parasites, and also tumor cells. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten their anti-viral defenses.

Question 10

Immune response

Answer 10

Humoral - antibody reactions

Cell mediated - T-lymphocytes

Question 11

Local reaction to infection

Answer 11

usually inflammatory evoked by cell damage and death

Question 12

Bacterial infection - genesis

Answer 12

Bacterial infections can cause:
Production of toxins - Endo vs ExoToxins
Hypersensitivity reactions - part of immune response resulting in tissue damage
Tissue invasion - lymphocyte spread + bacterial invasion of bloodstream [causes 3-aemias] Primary entry via lymphatic system

Question 13

3-aemias

Answer 13

Bacteraemia - low amt of bact in blood [dental = bact endocarditis]
Septicaemia - more bact in blood - baneful
Pyaemia - clumps of purulence forming bacterial - emboli + septic infarction

Question 14

Pyrexia

Answer 14

Increase in body temp due to imbalance between heat production and heat loss

• increase heat production due to increased metabolism
• increase temp in attempt to kill mico-organisms
• increased heat loss due to vasodilation in skin + perspiration
• changes assoc with increased pulse + dehydration

Question 15

Wound Healing

Answer 15

2 processes

• regeneration = complete [no scar, full function]
• healing = partial [tissue replaced by fibrin]

Question 16

Healing by 1st intention

Answer 16

Occurs with clean sterile wound
No micro-organisms + strong intact edges
No significant cell loss
2-3 hours, early inflamm near edges + epithelial cells move across from wound edges
2-3 days, epithelial growth + macrophages remove clots
10-14 days, epithelial covering complete with weak wound covering
weeks, hyperaemic with good union
months, remodeling with collagen

Question 17

Healing by 2nd intention

Answer 17

Large open wounds (significant tissue loss)
Necrosis + infection
Cavity fills with blood + fibrin clots (acute inflamm)
Scab dries out, mitotic activity in epithelium with fibroblasts, neutrophils + macropahges present. (wound contracts)
Surface debris sheds, epithelium grows across + loose connective tissue formed by fibroblasts
Cappilary loops may form at wound basse
Epithelium recovers + scar tissue forms
Fibrosis may result with chronic inflamm + organization.

Question 18

Factors delaying wound healing

Answer 18

Local:

• Infection
• poor blood supply
• excessive movement
• presence of foreign matter (infectious)

Systemic

• Deficiencies of Vit C, amino acids + zinc
• debilitating chronic disease
• (above factors affect collagen synthesis)