Micro test 4

pathogens only cause disease if…

1. it gains access via skin penetration or portals of entry

2. attaches itself to host cell

3. evades the host body mechanism

Humans naturally resist some pathogens because…

1. our cells dont have the cellular receptors for a pathogen to attach to

2. conditions in our body arent suitable for pathogen to grow

3. Our body temperature and pH levels make it hard for pathogen to survive

First line of defense

skin

mucous membrane

secretions

reflexes

normal microbiota

Second line of defense

inflammation

phagocytes

fever

complement system

interferon

Third line of defense

T cell lymphocytes

B cell lymphocytes

antibodies

Physical aspects of skin that prevent pathogen entry

epidermis acts as physical barrier

continuous shedding of epidermal cells

dendritic cells in the epidermis

collagen fibers in dermis

Chemical aspects of skin that prevent pathogen entry

antimicrobial peptides

dermcidin in sweat

lysozyme in swat

sebum from sebaceous gland

Location of mucous membranes

respiratory tract

digestive tract

urinary tract

salivary glands

lactating breast

lacrimal glands

tonsils and adenoids

Physical protection by mucous membranes

tightly packed epithelial cells

shedding of epithelial cells

goblet cells and mucus secretion

ciliated columnar cells in trachea

dendritic cells beneath epithelium

chemical protection by mucus membrane

antimicrobial peptides (defensins)

acidic environment in mucus membrane

lysozyme in nasal mucus

What is the lacrimal apparatus

a system of structures that produce and drain tears to maintain moisture and cleanliness

what does the lacrimal apparatus do

secrete tears and the tears travel through the ducts on to the surface of the eye

where do tears go?

-they either evaporate or drain into lacrimal canals

-they flow into nasolacrimal ducts which empty into nose

-tears mix with nasal mucus and flow into the pharynx where they are swallowed

Normal microbiota in the skin

staphylococcus epidermis, bacterium acnes, micrococcous luteus

Normal microbiota in the oral and respiratory tract

streptococcus salivarius, streptococcus mutans

Normal microbiota in the gastrointestinal

E. coli, lactobacillus, bacteroids species

Normal microbiota in the urogenital tract

lactobacillus, staphylococcus saprophyticus

Normal microbiota in the intestinal tract

bifidobacterium enterococcus

How do microbiota protect against disease

competition for nutrients

pH modification

stimulation of immune response

antimicrobial production

vitamin production

antimicrobial peptides (defensins) do what

help the body fight infections by targeting microorganisms

antimicrobial peptides are found where

mucus membranes, skin, and neutrophils

antimicrobial peptides are activated how

triggered by sugar and protein molecules on the surface of microbes

antimicrobial targets..

gram positive, gram negative, protozoa, fungi, or enveloped viruses

antimicrobial peptides mechanisms of action

membrane disruption

immune system activation

bacterial capture

components of blood

plasma, WBC, RBC and platelets

what is blood

a complex liquid tissue composed of cells and portions of cells within a fluid called plasma

what is plasma

liquid component of blood, composed of water, electrolytes, dissolved gases, nutrients and proteins

types of plasma proteins

transferin, ferritin, siderophores, lactoferrin, complement proteins, antibodies/immunoglobins

functions of plasma proteins

clotting

iron binding

complement protein

antibodies

Hematopoiesis (begins and branches)

begins in bone marrow with stem cell

branches into 3 pathways: erythroid, myeloid, or lymphoid cells

Erythroid branch

produces erythrocytes, focuses on gas transportaion

Myeloid branch

makes platelets, basophils, neutrophils, eosinophils, and monocytes

Lymphoid branch

includes cells for adaptive immunity: B, T and NK cells

cells of hematopoiesis

erythrocytes: most numerous—carries oxygen and carbon dioxide

platelets: pieces of megakaryocytes: involved in blood clotting

What are neutrophils

(granulocyte) phagocytic pathogens perform diapedesis allowing them to exit the bloodstream and attack invading microbes in tissues

What are eosinophils

(granulocyte)phagocytic pathogens defend against parasitic worms, present in large numbers during allergic reactions

what are basophils

(granulocyte) can leave blood via diapedis. do not phagocytize but do release inflammatory chemicals contributing to immune response

what are lympocytes

(agranulocytes) most are involved in adaptive immunity: B, T and NK cells

what are monocytes

(agranulocytes) leave blood via diapedesis and mature in macrophage

types of macrophages

wandering

fixed

types of second line of defense

phagocytosis, non-phagocytic killing by leukocytes, nonspecific chemical defenses, inflammation and fever

Phagocytosis

1. chemotaxis: phagocytes are chemically attracted to the site of infection

2. adhesion: phagocytes attaches to the surface of the microorganism

3. Ingestion: phagocyte extends pseudopods to surround the microbe. Pseudopods fuse internalizing the microbe into a food vesicle called the phagosome

4. phagosome maturation and microbial killing: lysosome fuses with phagosome creating a highly acidic, toxic environment that kills most pathogens

5. Elimination: once microbe is digested, phagocyte gets rid of debris. phagolysosome fuses to cell membrane and releases waste material out of the cell

death by eosinophils

1. adhesion: they attach to the surface of the parasite. (triggered by presence of antibody IgE

2. degranulation: releases content of its internal granules onto parasites surface

3. chemical weapons: granules contain highly toxic and enzymes

4. membrane damage: the chemicals work together to weaken and poke holes in the parasites tough outer membrane, killing it

NK perforin/granzyme pathway

1. NK cell releases perforins which punch holes in tumor cell’s membrane

2. granzyme B enters through the holes, activating enzymes that force the cell to undergo apoptosis or necrosis

NK death receptor pathway

1. FasL: Nk cell has a ligand (FasL) on its surface

2. Fas is a receptor on tumor cell

3. when the two connect, it triggers a death signal inside tumor cell, apoptosis occurs

NK antibody-dependent cellular ecotoxicity

1. Ab: if antibodies have already attached to an antigen (Ag) on the tumor cell then the NK cell can recognize them

2. the NK cell uses FcR to latch onto tail end of antibody

3. connection triggers NK cell to release deadly perforins and granzymes at the targer

death by neutrophils

1. degranulation: neutrophils vomit granules with toxic chemicals and antimicrobial proteins into extracellular space which destroy the bacteria’s cell walls or neutralize toxins before the enter the cell

2. phagocytosis: neutrophils wrap its membrane around the bacteria swallowing it into a phagosome, toxic granules fuse with phagosome creating a stomach filled with digestive enzymes and acids that dissolve the bacteria instantly

3. NETosis: neutrophil ejects DNA into the environment, DNA is coated in sticky proteins that look like nets. These nets act like a spiderweb and trap bacteria in place so they can’t spread while enzymes kill them.