Lecture 4

Question 1

How is the skin an excellent physical barrier?

Answer 1

Tthe outer epidermis is principally composed of dead keratinized cells with plenty of tight junctions (see previously) to limit access between them.

Question 2

T or F? Skin secretions principally from hair follicles (sebaceous glands) have a ↓pH and contain lactic and fatty acids which all inhibit bacterial growth (so more susceptible on non-hairy skin).

Answer 2

True

Question 3

Sweat, tears, saliva and some nasal secretions all contain the enzyme ________ which is capable of destroying the cell walls of certain bacteria: salinity in sweat may also help.

Answer 3

lysozyme

Question 4

T or F? Modified sweat and sebaceous glands in the internal auditory canal of the ear secrete cerumen (ear wax) which like mucus traps dust particles but also repels insects.

Answer 4

False, external auditory canal

Question 5

The viscosity of mucus traps many organisms, etc. and prevents adherence prior to expelling (coughing, sneezing, etc.): in addition it contains antimicrobial ________.

Answer 5

peptides

Question 6

What is the function of urine and vaginal secretions in regards to pathogens?

Answer 6

It flushes pathogens away.

Question 7

After menstruation begins the vaginal secretions become slightly ________ which inhibits bacterial growth (but favors fungi/yeasts: infections are common).

Answer 7

acidic

Question 8

What does semen contain that are lethal to some pathogens?

Answer 8

spermine and zinc

Question 9

Blood draining the GI tract filters first through the _____ which is full of immune cells.

Answer 9

liver

Question 10

What is the main defense of the GI tract?

Answer 10

Stomach acid which has a pH ~ 1.5 due to HCl secretion plus the protease pepsin

Question 11

What powerful enzyme does mother’s milk contain?

Answer 11

Lactoperoxidase which is antimicrobial (in addition milk contains antibodies from the mother to confer protection to the suckling child)

Question 12

_______ and ________ caused by some microbial toxins acting on smooth muscle of the GI tract or via the chemosensitive area of the brainstem helps expel the toxins and pathogens also.

Answer 12

Defecation ; vomiting

Question 13

T or F? Mucus trapping microbes operates throughout the upper respiratory system from the nasal cavities down to the bronchioles: cilia sweep the mucus out of these areas to be swallowed.

Answer 13

True

Question 14

In the respiratory tract, what is the first level of filtration?

Answer 14

Nose hairs. we should breath through our noses for this function plus WARMING and HUMIDIFYING inhaled air.

Question 15

_________ actually enter the alveoli of the lungs searching for pathogens to phagocytize

Answer 15

Macrophages, in fact macrophages will travel across moist external bodily surfaces searching for pathogens such as the cornea of the eye

Question 16

T or F? We live in harmony (“symbiotic”) with many microbes (gut flora/fauna producing vitamin K for instance): this normally occurs only throughout the GI tract.

Answer 16

False, occurs on the skin, in the mouth and throughout the GI tract.

Question 17

What happens if you lose all your normal flora?

Answer 17

Disruption of these colonies may make it easier for potentially pathogenic bacteria to grow and colonize these areas for themselves

Question 18

The Innate Response to injury and/or infection is primarily that of ________________.

Answer 18

Inflammation; this includes vasodilation, ↑vascular permeability to important plasma proteins, phagocyte chemotaxis, phagocytosis and/or destruction of the invading pathogen nonspecifically.

Question 19

Innate response: The initial response is mediated by tissue macrophages at the site which phagocytize “foreign” material identified by pattern recognition _____________ (remember this can be the start of the Acquired Response if the macrophage then acts as an APC).

Answer 19

receptors

Question 20

T or F? The complement system can be partially activated (“alternate”) during the Innate Response causing enhanced phagocytosis (opsonization by C3b binding to bacteria) and implementation of the MAC.

Answer 20

True

Question 21

What is the final stage of the innate response and can persist for weeks?

Answer 21

Responding leukocytes secrete various Colony Stimulating Factors which cause the release of stored leukocytes and increased production in the bone marrow

Question 22

____________ produced by cells invaded by viruses stimulate the production of various antiviral proteins (inhibit replication).

Answer 22

Interferons

Question 23

Thromboxane A2 (TXA2) and prostaglandin I2 (PGI2) are synthesized from?

Answer 23

AA via PLA2

Question 24

Activated platelets release?

Answer 24

phospholipids (such as platelet Factor III), Ca2+, ADP (+Fb/Plavix), PG’s and TXA2 (principle ones!).

Question 25

Activated factor X (Xa) combines with phospholipids and factor V in the presence of Ca2+ to form the Prothrombin activator?

Answer 25

true

Question 26

What activates factor V?

Answer 26

thrombin (+Fb)

Question 27

Factor Va is part of what? How is Va inactivated/how is its effect limited?

Answer 27

prothrombin activator +Fb loop; protein C inactivates Va while thrombin is inactivated principally by absorption onto fibrin fibers (separate mechs to stop +Fb loops)