Exam 4: Body Defenses 1st and 2nd

Question 1

What is species resistance?

Answer 1

Chemical receptors required by many pathogens do not exist in the human body.

Question 2

What is an example of a pathogen that cannot infect humans?

Answer 2

T4 bacteriophages or the tobacco mosaic virus.

Question 3

What is the physical or chemical basis for species resistance?

Answer 3

pH or temp of the human body is incompatible with the requirements of many pathogens.

Question 4

In raw numbers, how many bacteria are present in an on the human body?

Answer 4

100-700 trillion.

Question 5

How many bacteria do we have in and on our bodies as compared to human cells? How many viruses?

Answer 5

Bacteria outnumber human cells tenfold.&raquo_space;100 trillion viruses.

Question 6

Do most of the microbes housed by the human body cause harm?

Answer 6

No, most don’t cause harm but some do.Many have the potential to cause harm in specific situations.

Question 7

Through what means do the microbiomes of human skin and mucous membranes protect against pathogens?

Answer 7

Consumes nutrients making it unavailable to pathogens.

Change pH in a way that is unfavorable to pathogens.

Block attachment site for potential pathogens

Stimulate the body production of antimicrobial substances.

They themselves can generate antimicrobial substances.

Question 8

In no more than one sentence each, briefly describe the three lines of body defenses.

Answer 8

First line is skin and mucous membrane, second line is generalized responses involving cells and chemicals, and third line is specific responses to specific pathogens “adaptive immunity”

Question 9

Which of the three lines of body defenses are part of innate immunity?

Answer 9

First and second lines of defense (skin/mucous membrane and generalized response) are part of innate immunity.

Question 10

What three characteristics are features of innate immunity?

Answer 10

Nonspecific, operates with virtually no “lead time”, protects the body against a wide range of pathogens.

Question 11

Briefly describe the cellular structure and arrangement in each of the two layers of skin.

Answer 11

Outer layer is epidermis and inner is dermis. Dermis is thicker than epidermis but both are involved in body defenses. Epidermis’ lowest layers divide and force cells upward to replace cells sloughed off. Outermost cell layers are dead and filled with resin-like keratin. B

Epidermis acts as a physical barrier to microbes, most microbes cannot penetrate these closely packed dead skin cells unless it has been compromised by a burn, cut, etc. Able to clear microbes that colonize its surface. Bacteria are sloughed off with these outermost cells. 
Dermis cells are living and not packed tightly together. Tissue fluid (extracellular matrix; ECM) lies between these cells. Contains nerves, muscles, blood vessels, jair, follicles, sweat, glads, oil glands, protein fibers and more.

Question 12

How do humans benefit from the microbes normally present on their skin?

Answer 12

Microbes normally on the epidermis can provide protection. Prevents pathogenic bacteria from growing on the skin in their place. Staphepidermadis “normal flora” on skin does fermentation that produces some acid making skin slightly acidic which reduces other pathogens from being able to grow.

Question 13

What is phagocytosis? What cells in the epidermis are capable of phagocytosis?

Answer 13

Phagocytosis is the process by which a phagocyte (a type of white blood cell) surrounds and destroys foreign substances (such as bacteria) and removes dead cells. Dendritic cells in the epidermis can “eat” pathogens through phagocytosis

Question 14

Why isn’t it necessary for most of the cells in the skin’s epidermis to have access to a blood supply?

Answer 14

Because they are primarily dead skin cells not living skin cells.

Question 15

Aside from cells, what other components are present in the skin’s dermis?

Answer 15

Collagen fibers: fibrous proteins that confer strength and liability and prevent many jabs and scrapes from penetrating the skin.
Hyaluronic acid: polysaccharide that makes fluids in the dermis viscous, which impedes the spread of pathogens.

Question 16

What is tissue fluid, and what is its relevance to skin?

Answer 16

Tissue fluid lies between the dermis cells. It facilitates substance exchange between cells and the blood by helping bring oxygen and nutrients to cells, and removing waste products from them as well.

Question 17

How is collagen important to the function of skin? What ability have some bacteria evolved as a means of circumventing a protective function of collagen?

Answer 17

Confer strength & flexibility to dermis. Some bacteria produce enzyme collagenase which hydrolyzes peptide bonds in collagen allowing microbes to penetrate deeper into the host. e.g. clostrdium histolyticm.

Question 18

How is hyaluronic acid important to the function of skin? What ability have some bacteria evolved as a means of circumventing a protective function of hyaluronic acid?

Answer 18

Makes the dermal ECM viscus. Some bacteria produce enzyme hyaluronidase which hydrolyzes hyaluronic acid and reduces ECM viscosity. Reduced viscosity allows microbes to spread faster. e.g. staphylococcus aureus.

Question 19

What are defensins? Are all defensins identical? Explain.

Answer 19

Defensins are antimicrobial peptides secreted by dermal cells. 20-50 amino acids in length. Hundreds identified and different peptides act through different mechanisms.

Question 20

List at least four mechanisms by which defensins protect the human body.

Answer 20

• Punching holes in cytoplasmic membranes of pathogens
• Interrupting internal signaling of pathogens
• Interrupting enzymatic action in pathogens
• Neutralize bacterial exotoxins
• Recruit leukocytes (white blood cells) to the site
• Assemble to form nets to ensnare pathogens

Question 21

What components of perspiration help protect the human body from pathogens? How do each of these components function?

Answer 21

Contains salt, antimicrobial peptides, and the enzyme lysozyme. Salt osmotically removes water from invading cells. Lysozyme destroys bacterial cell walls by cleaving peptidoglycan.

Question 22

In what two ways do the secretions from oil glands protect the human body from pathogens?

Answer 22

Sebum secreted by oil glands keep skin pliable and less prone to tearing. Contains fatty acids that reduce the ph of the skin’s surface.

Question 23

Where in your body are mucous membranes present?

Answer 23

Eyes, nose, mouth ,urethra, vagina, anus, and the lumens of the related body cavities.

Question 24

Describe the two layers present within mucous membranes, including the cellular structure and arrangement within these two layers.

Answer 24

Epithelium- thin outer layer of living cells (often 1 cell thick), packed close together like the skin’s epidermis. Barrier to the entry of microbes though less efficient than the skins epithelium. Continually shed and replaced by stem cells, microbes are shed with these cells. Dendritic cells extend pseudopods into the epithelium. Function varies depending on location; protection, absorption, and/ or secretion.

Connective tissues- termed lamina propria deeper, layer that provides mechanical and nutritive support to the epithelium. Thicker than epithelium, contains numerous collagen and elastin filaments. Contains numerous cells of the immune system, contains phagocytic dendritic cells.

Question 25

How are mucous membranes similar to skin?

Answer 25

Consists of two layers one thicker and one thin. The epithelium is packed close together like the skin’s epidermis.

Question 26

How do mucous membranes differ from skin?

Answer 26

All cells are living, no layer of dead skills in the mucous membrane like with skin. Environment is moist instead of dry.

Question 27

List three features of mucous membranes that help protect the human body from pathogens.

Answer 27

Goblet cells: cells secrete sticky mucous. Traps microbes which are then shed, propelled away from the lungs by cilia. Mucous also contains antimicrobial peptides. The effectiveness is drastically reduced in tobacco smokers.

Lacrimal apparatus: produces and drains away tears. Blinking spreads tears and washes the surface of eyes. Tears contain the enzyme lysozyme. 

Epithelium layer is continuously shed and replaced, microbes are shed along with it.

Question 28

Where is the enzyme lysozyme produced, and how does it protect against pathogens?

Answer 28

Lysozyme in tears protects pathogens from entering the body via the eyes.

Question 29

What feature of the stomach’s mucous membranes help protect against pathogens in a way that other mucous membranes do not? How are cells of the stomach’s mucous membranes themselves protected from this defense mechanism?

Answer 29

Parietal cells in the stomachs epithelium secrete hydrochloric acid (HCL). pH 1-3 aids in protein denaturation and digestion. Kills most ingested bacteria. Some bacteria have evolved defenses against this acid.

Question 30

What characteristics of Helicobacter pylori allow it to circumvent defenses of the stomach? What enzyme does it excrete?

Answer 30

Powerful flagella allow helicobacter pylori to burrow into the mucous covering the surface of the stomach epithelial cells. Inhibits a microenvironment with neutral pH. Secretes the enzyme urease to further neutralize the pH. Can expose epithelium to HCl and cause peptic ulcers.

Question 31

Does the second line of body defense adapt to specific pathogens? Explain.

Answer 31

No, it responds similarly to all pathogens. Response does not become increasingly effective against specific pathogens, this response does not adapt.

Question 32

What components make up blood?

Answer 32

Blood is made of ~55% volume plasma (water, ions, dissolved gasses, nutrients, proteins.). ~45 volume formed elements (erythrocytes -RBC, platelets, and leukocytes). Blood clotting occurs in response to injuries to the vascular system.

Question 33

What is the relationship between the proteins fibrin and fibrinogen? Where is it located?

Answer 33

Clots are formed of the protein fibrin. A non-clotting precursor (fibrinogen) present in the blood plasma is converted into fibrin, which clumps together. Stimulated by platelets.

Question 34

What is the function of fibrinogen and fibrin? How does this protect against pathogens?

Answer 34

Blood loss is reduced and risk of infection is reduced. Blood clots imprison bacteria in the area and prevent their spread.

Question 35

What specific defense have some bacteria evolved in response to the normally protective function of fibrin?

Answer 35

Some bacteria produce enzymes that can break down blood clots. e.g. streptokinase, staphylokinase digest the protein in the clot and promote invasion of damaged tissues.

Question 36

How does blood clotting protect against pathogens?

Answer 36

Blood clots imprison bacteria from moving along the bloodstream and block new bacteria by closing the wound.

Question 37

How is iron important to the human body?

Answer 37

Iron is a key part of hemoglobin, transports O2 through the body and is present in all globins. Enzyme cofactor assists enzymes in their function. Component of all cytochromes in electron transport chains, helps extract energy from the “burning” of food molecules .

Question 38

How is the iron in our bodies made unavailable to microbes?

Answer 38

Relatively insoluble in water. Most of the iron is bound to proteins. E.g hemoglobin-RBC, transferrin-plasma,ferritin-stored in liver. Binding makes iron unavailability to microorganisms however iron is critical to their metabolism.

Question 39

Coevolution

Answer 39

The reciprocal evolutionary change in a set of interacting populations over time resulting from the interactions between those populations. Cases where two (or more) species reciprocally affect each other’s evolution.

Question 40

Iron sequestration

Answer 40

iron binding proteins make iron unavailable to microorganisms.

Question 41

What is a hemolysin? How do bacteria benefit from hemolysins?

Answer 41

Virulence factor produced by proteins that damages red blood cells causing them to release iron for bacteria to use.

Question 42

What is a siderophore? How do bacteria benefit from siderophores?

Answer 42

Iron-binding proteins, complex molecules much smaller than proteins. Higher affinity for ions than that of human proteins. Give bacteria the ability to “steal” iron from the human body.

Question 43

Some bacteria produce transferrin receptors. How does this benefit such bacteria?

Answer 43

Enables the bacteria to have close access to transferrin protein, gets them close enough to remove iron from the blood plasma.

Question 44

What is a leukocyte?

Answer 44

White blood cells. Able to exit the blood and enter tissues, squeeze between cell lining capillaries (small blood vessels). Able to phagocytize pathogens, engulf and destroy these invaders. Release inflammatory chemicals involved in inflammatory response.

Question 45

What is phagocytosis?

Answer 45

The process by which a phagocyte (a type of white blood cell) surrounds and destroys foreign substances (such as bacteria) and removes dead cells.

Question 46

Inflammation can be either acute or chronic. Which is beneficial and which is problematic? Give characteristics of both.

Answer 46

Acute inflammation is typically beneficial while chronic inflammation is not beneficial.

Acute inflammation- develops quickly, short-living, results in elimination or resolution of precipitating conditions. 

Chronic inflammation- long lasting, causes damage (even death) to tissues, and results in disease.

Question 47

What are the four signs and symptoms of inflammation?

Answer 47

Redness- in light colored skin, results from increased blood flow through capillaries.

Localized heat- blood is naturally warmer so increased blood increases heat. 

Swelling (edema)- leukocytes and fluids exiting the capillaries and entering the tissue.

Pain- swelling causes pressure on nerves resulting in pain.

Question 48

What is vasodilation?

Answer 48

Early response to injury. Increased diameter of blood vessels in affected region. Increased blood flow to the area, increases delivery of O2, phagocytes, and nutrients. Cells lining the veins contract and pull apart. Phagocytes squeeze through the gaps created, delivery of antimicrobial chemicals also enhanced like fibrinogen. Pus is formed from dead tissue cells, leukocytes, and pathogens.

Question 49

How does the dilation and increased permeability of blood vessels benefit the human body?

Answer 49

leukocytes and thus phagocytes are able to leave the blood vessels and move to the site where needed.

Question 50

How does the dilation and increased permeability of blood vessels lead to the signs and symptoms of inflammation?

Answer 50

Increased blood flow causes redness and increases heat. Fluid accumulates surrounding tissue causing swelling which put pressure on the nerves causing pain.

Question 51

Through what mechanism do antihistamines reduce inflammation?

Answer 51

Antihistamines block histamine receptors, histamine is a chemical that triggers vasodilation.

Question 52

Through what mechanism do aspirin and ibuprofen reduce pain from inflammation?

Answer 52

Prevents prostaglandin synthesis,prostaglandins are chemicals that promote inflammation. Reduction in prostaglandins reduces fever and pain.

Question 53

Inflammation leads to tissue repair by?

Answer 53

Supplying O2 and extra nutrients. Tissues can be fully restored if they contain undifferentiated stem cells. Scar tissue formed when the stem cell is not the same cell type as what is being replaced. Some tissue such as cardiac muscle and parts of the brain do not replicate and thus cannot be repaired, damage remains.

Question 54

What is a pyrogen? What is its function?

Answer 54

Chemicals that can trigger the hypothalamus to reset at a higher temperature. Causes a fever.

Question 55

What sorts of molecules function as pyrogens?

Answer 55

Bacterial toxins, components of bacterial cells, antigen-antibody complexes, chemicals released by phagocytes.

Question 56

In what ways can a fever be beneficial?

Answer 56

• Inhibits the growth of some microbes.
• Enhances performance of phagocytes.
• Increases the rate of tissue repair.
• Increases activity of lymphocytes involved in adaptive immunity.