Chapter 16 Non-specific defenses of the host

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Describe the role of the skin and mucous membranes in nonspecific resistance

the skin and mucous membranes are the first line of defense: non- specific mechanical barriers to infection. composition- physical/mechanical defenses of the skin and mucous membranes. Innate immunity, nonspecific
skin= great physical barrier, oils (sacks of keratin on epidermis lubricate, metabolized by microbes as a food source) keratin is a tight water proof barrier that is like armor and is hard to digest , natural flora (staph, strep, candida albicans) occupies niches that make it difficult for pathogens to take hold. , pH (4-6) discourages the growth of many pathogens, sweat contains salt, urea and lysozyme, .
mucous membranes= respiratory system (nasal, throat, trachea, bronchii, alveoli, mucus, hair, sneeze, cilia) GI tract (saliva, protects from tooth decay, mucous membranes, pH extremes, peristalsis) UG tract (urigenital tract, urine system, acidic pH (4.3-4.9) Mucus membranes line the GI, respiratory and genitourinary tracts. The epithelial lay secretes a fluid called mucus, a slightly viscous glycoprotein produced by goblet cells of a mucous membrane. It prevents the tracts from drying out and serves as a mechanical barrier to microbes.

Differentiate mechanical from chemical factors, and list examples of each.

a physical barrier relies on the material it is made of to block the passage of "whatever" in and out or through the barrier. What can or cannot pass through is dictated by the size of the spaces between the molecules, or holes, in the physical barrier. A chemical barrier is made up of chemicals, or enzymes, and more, than do not allow certain chemicals to pass through, For example, the chemical kills the germ before it can pass into a cell, or the barriers of the cell, and parts inside the cell , dictate what can and cannot penetrate the cell, if all works well.
examples: skin (epidermis, dermis) mucous membranes, hairs, cilia, peristalsis, defecation, vomiting.
chemical factors- vaginal secretions, gastric juice, perspiration, sebum, urine

Describe the role of the normal flora in nonspecific resistance

Normal flora organisms may keep pathogen numbers under control by:
1. Competing with them for nutrients
2. Producing substances harmful to the pathogens
3. Altering environmental conditions so that pathogens are inhibited (pH and oxygen availability)

Define phagocytosis and phagocyte

phagocytosis- the ingestion of solids by eukaryotic cells. Cell eating, ingestion of m/o, dirt debris by WBC
phagocyte- a cell capable of engulfing and digesting particles that are harmful to the body

Describe the process of phagocytosis and include the stages of adherence and ingestion.

chemotaxis and adherence of microbe to phagocyte- adherence is the attachment of the phagocytes plasma membrane tot eh surface of the microorganism or other foreign material.
ingestion of microbe by phagocyte
formation of phagosome
fusion of the phagosome with a lysosome to form a phagolysosome
digestion of ingested microbe by enzymes
formation of residual body containing indigestible material
discharge of waste materials
phagocytes migrate to a site of infection and can destroy the infecting bacteria. The phases of phagocytosis are chemotaxis, adherence, ingestion, and digestion.

List the stages of inflammation

1) redness
2) swelling
3) heat
4) pain
5) loss of function
damage to otherwise healthy tissue- in this case skin
vasodilation and increased permeability of blood vessels
ohagocyte migration and phagocytosis of bacteria and cellular debris by macrophages and neutrophils. Macrophages develop from monocytes
the repair of damage tissue

Describe the cause and effects of fever

fever- an abnormally high body temperature, a third component of the second line of defense. the most frequent cause of fever is infection from bacteria (and their toxins) or viruses. Fevers help fight off infection High temperatures speed up the bodies reactions it may help the body repair tissues more quickly

identify at least one physical and one chemical factor that prevent microbes from entering the body through each of the following:
urinary tract:
reproductive tract:

urinary tract: chemical= lysozome; acids mechanical =movement out
reproductive tract: chemical= vaginal secretions acidic environments in females mechanical= movement out.

define inflammation and list its characteristics

inflammation is usually characterized by redness, swelling, loss of function, pain and heat and is defined as a host response to tissue damage.

what are interferons? Discuss their roles in innate immunity

a specific group of cytokines. are antiviral proteins produced by certain animal cells in response to a viral infection. stimulates macrophage activity
would inhibit bacteria
would prevent adherence of N. gonorrhoeae
S. pyogenes would not be able to attach to host cells and would be more susceptible to phagocytosis

how can the complement system cause endotoxic shock?

endotoxin binds C3b, which activates c5-c9 to cause cell lysis. This can result in free cell wall fragments which binds more C3b resulting in c5-c9 damage to host cell membranes

patients with x-linked chronic granulomatous disease are susceptible to infections because their neutrophils dont generate an oxidive burst. What is the relation of the respiratory burst to infection?

toxic oxygen products can kill pathogen

Why does hemolysis of RBC occur when a person receives a transfusion of the wrong type of blood?

the recipients antibodies combine with donor antigens and fix complement; the activated complement causes hemolysis

Give several examples of how microbes evade the complement system

inhibit formation of C3b; prevent MAC formation; hydrolyze C5a.

are the following involved in innate or aaptive immunity? Identify the role of each in immunity:
a) TLR's
b) tranferrins
c) antimicrobial peptides

a) Innate. Facilitate adherence of phagocyte and pathogen
b) Innate; bind iron
c) Innate. Kill or inhibit bacteria

Legionella uses C3b receptors to enter monocytes. This
a) prevents phagocytosis
b) degrades complement
c) inactivates complement
d) prevents inflammation
e) prevents cytolysis

d

In 1884, Elie Metchnikoff observed blood cells collected around a splinter inserted in a sea star embryo. This was the discovery of
a) blood cells
b) sea stars
c) phagocytosis
d) immunity
e) none of the above

c

Helicobacter pylori uses the enzyme urease to counteract a chemical defense in the human organ in which it lives. This chemical defense is
a) lysozyme
b) hydrochloric acid
c) superoxide radicals
d) sebum
e) complement

b

Why do serum levels of iron increase during an infection? What can a bacterium do to respond to high levels of transferrin?

serum levels of iron increase during an infection because
Higher levels of tranferrin decrease the iron levels available to microbes and most pathogenic bacteria require adequate amounts of iron for their vegetative growth and reproduction.

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