biol121- week 2

microorganism

tiny living organisms, can reproduce independently (viruses and prionons aren’t living), they are everywhere, essential for decomposition and recycling of nutrients, affects our everyday lives

prokaryote

small, unicellular, organelles have no membrane & lack a nucleus, asexual reproduction - cell divisions - binary fission

• benefit: clinically these cells are so fundamentally different, these drugs have selective toxcity and are effective on killing these cells

• don’t damage eukaryote cells in a large manner - harder to kill cells

eukaryote

large (over 5 millionths of a metre), multicellular, organelles have a membrane, sexual reproduction (can be asexual), cell division - mitosis/meiosis

viruses

not living, no cellular structures, protein capsule around DNA or RNA, can mutate, antibiotics are ineffective (therefore we use antivirals), size = billionths of a metre

bacteria

prokaryote, mostly uni-cellular, different shapes, have a cell wall (this thickness is important)

• salmonella, golden staph, syphillis

protozoa

eukaryotic cells, unicellular, usually motile, 1-150 microns

• giardia, malaria, cryptosporidium

fungi

eukaryote, uni or mult-cellular, has a cell wall, produces spores, 2-10 microns

• tinea, ringworm, aspergillus

helminths

eukaryote, uni-cellar, large (organ systems), eggs/larva/adult, don’t proliferate in host

• cestodiasis

• (tape worm infestation)

• ascarsias

• guniea worm

growth requirements - temp

thermophile (60) - heat-loving

mesophiles (25-30) - moderate temps

psychrophiles (10) - cold loving

growth requirements - pH and 02

pH - most close to neutral, again variable depending on organisms

examples

heliobacter pylori (gastric ulcers) - able to survive at pH 3.5 found in stomach antrum (area closest to small intestine) - this enables them to survive and potentially cause ulcers

obligate aerobes: can ONLY grow in the presence of 02

• mycobacterium tuberculosis

obligate anaerobes: can NOT grow in the presence of 02

• clostridium perfingens (significant drop in blood supply)

facultative anaerobes: in the presence (prefer) and absense of oxygen

• e-coli

• salmonella

gram positive

thick layer of peptidlygan - holds the stain in, but also easier to kill

• capable of forming spores - survive in extreme conditions, common for reinfection

• pneumococci

gram negative

gram negative - reinforced with a second membrane

• more difficult to kill

• produce endotoxins - released when bacteria die and can cause sepsis

microbiota

• bacteria cells: 10 x more than human cells - 5kg worth of

• resident/normal flora - big role in our lives

• outcompeting pathogenic bacteria

• colonised/transient

• hygiene

• normal flora getting into a wound and growing - infection & inflammatory response

• skin, mouth, throat, large intestine & gut - make vitamin K

benefits and harmal effects of microbiota

benefits:

skin: reduce pH, change environmental conditions and thus not ideal for other species and they can’t grow

oral & vagina: competes and inhibits - pathogens and yeasts

intestine: excrete antibacterial chemicals, vitamins, stimulate local immunity

harmful effects

• compete for nutrients

• bacterial synergism: normal flora and pathogen - antibiotic resistance

• endogenous disease: fever, inflammation

transmission

contact: between people, either directly (touch) or indirectly (two people toyching the same inanimate object)

vehicle: transmission of pathogens via vehicle such as air, water or food

vector: via an animal (mosquitos)

chain of infection

chain of infection:

• infectious agent - how does it transmit and affect patients, what can we do to stop that, what can we give?

• reservoir - a population of organisms which the infections agents sit - pass it on

• portal of entry - how does the agent end up into the patient, if we can block the portal of entry, the agent may likely not get into the patient

• mode of transmission - how does it transmit from person to person

• portal of exit - how it escapes the patient

• susceptible host - lack an immune response - people who are likely to develop disease - children, elderly patients, immuno-compromised patients = protect through isolation or vaccination

sterlilisation

destruction/elimination of ALL microbes (including every single bacteria, virus and spore)

• heat - dry (burning) & moist (boiling)

• heat & pressure

• radiation

• filration

• chemical - bleach & hydrogen peroxide

disinfection

elimination of most pathogens from inanimate objects (but not bacterial spores)

• chemical (alcohol, chlorine)

• gas (formaldehyde)

epidermis

• composed of epithelial cells, keratinised stratified squamous epithelium

• thinner portion of the two

• avascular - no blood vessels

keratinocytes: most abundant, creates keratin (provides for the resistant to water - and water isn't lost through the skin as easily), arises from the deepest layer of epidermis

melanocytes: spider-shaped cells, produces melanin, found in the deepest layer of the epidermis

langerhan’s cells: star-shaped macrophage cells, activate immune systems, origniate from bone marrow

merkel cells: present at the epidermeris-dermis junction, associated with nerve ending, function as sensory receptors

strata = layers

dermis

deep to the epidermis

• makes up the bulk of the skin

• composed of connective tissue: mainly collagen and elastin

• highly vascularised and innervated

• nerve supply = heaps, for sensation (touch, pain, temp)

cell types: fibroblast, macrophages, some mast cells, white blood cells

• papillary: thinner of the two layers, superficial to the reticular layer, sits directly underneath the stratum basale of the epidermis, help supply the epidermis and for stability

• reticular: thicker of the two layers (80% of the dermis), deep to the papillary layer, lots of collagen to stop penetration

hypodermis

deep to the dermis, not really part of the skin

hypo = under

• subcutaneous layer - important to protect this layer - due to pathogens

• lies beneath the dermis

• also called the superficial facia

• anchors the skin to underlying structure

• stores fat

factors to skin colour

melanin, carotene, haemoglobin, redness, palour, jaundice, blue/black

nails

what: modifications of the epidermis, densely packed epithelial cells containing fibres of hard keratin

where: located distally on the posterior surface of the fingertips and distally superior surface of the toes

why: protection of the underlying nerves aids in picking things up, scratching, digging

glands

what: clustered of specialised epithelial cells that secrete substance - oil, sweat, wax, milk

where: sweat glands: whole body expect nipples and parts of the external gentalia, sebaceous glands: whole body expect palms and soles

why: sweat glands; regulated body temp, remove wastes, sebaceous glands: softens skin and hair, decrease bacterial growth and water supply

hair

what: shaft: slender filaments of fertilised cells, root: below the surface, embedded within the skin, follicle: ground of cells that surround the root and holds hair in place

where: whole body expect palms, soles, nipples and parts of the external gentalia

why: warmth, protection against physical trauma, heat loss, sunlight, detect insects on the skin and keeping out foreign particles

functions

PROTECTION: chemical (skin secretions and melanin), phsyical - continuity & biological

BODY TEMP REGULATION: sweating

• 500ml/day at rest - unnoticeable

• up to 12L/day during vigorous exercise

CUTANEOUS SENSATION: sensory receptors to the skin allows us to feel touch, pressure, vibration, tickling, temp, pain, hair follicle receptors

METABOLIC FUNCTION: produces vitamin D - when exposed to UV for calcium phosphorus absorption (bone development)

BLOOD RESERVIOR: dermis - highly vascularised, blood can be temporily shunted from the skin and relocated to another part of the body that requires it

EXCRETION AND ABSORPTION: removal of nitrogenous wastes such as urea, ammonia, uric acid and salts - in sweats

absorbs vitamins A D E and K and oxygen

lymphatic system

1. drain excess fluid & proteins from all back to blood circulation

2. defends the body against external and internal threats (immunity/resistance to diseases)

3. transports fats and vitamins from gut to liver (digestion)

consists :

• immune cells, lymph fluid, lymph vessels, lymphatic organs and tissues

• lymphocytes - key players

• produced from the same precursor cell in the bone marrow

• mature in the bone marrow or thymus

lymph

LYMPH: means fluid

• fluid connective tissue

• contains lymphocytes and macrophages - enemies they seek out and destroy

• lymph flows through special tubes from tissues to the venous system and heart

lymph/atic capillaries , vessels, trunks and dunks

lymph cont

blood plasma (from capillaries) - interstitial/tissue fluid - lymphatic capillary = lymph vessels, trunks & ducts - blood plasma (vein at the base of the neck)

• capillaries that begin as blind ended tubes

• structure similar to blood capillaries - one layer of epithelial cells supported by basement membrane

• structure helps to let fluid in, but not out = overlapping endothelial cells open when tissue fluid is high (one-way valve)

• lymph capillaries in the inessential villi = lacteals

• thin walls

• resemble veins; have more valves

• have lymph nodes at intervals

• respiratory and muscular pumps promote flow of lymph towards large veins/heart

1. vessels unit to from 2 thoracic ducts

2. right side head, arm, chest and empty into right lymphatic duct

3. left side and lower body empties into main thoracic duct (largest vessel)

primary lymphatic organs

• red bone marrow: in flat bones, at the end of bones, contains haemopoietic stem cells, produces &matures B cells and make pre-T cells (lymphocytes)

• thymus gland: in the mediastinum - large in infancy, max size (70g) at puberty, atrophied (3g) but functional in adulthood, T cells mature here, thymus makes thymosin hormones for development and maturation of T cells

secondary lymph organs

• spleen: between stomach and diaphragm, macrophages remove worn out or defective RBC, WBC and platelets, stores and releases blood and blood cels, site of production of blood cells during the second trimester of pregnancy

• lymph nodes: 1-25mm, along lymphatic vessels, multiply lymphocytes (finishing school for B cells), filter lymph: afferent vessels bring lymph with foreign material into the node, foreign matter trapped in fibres, destroyed by macrophages, B and T cells, efferent vessels leaves node with cleaner lymph

first line of defence

antigen: anything capable of inducing an immune response, anything foreign to you as a host

• microbes or their parts

• protein from other species - rabbit serum, dust mite, cat hair, pollen

• transplanted tissue from other humans/pollen

non-specific - INNATE

• general defence- attack on all antigens

• inborn

• first and second line defences

• don’t distinguish between threats, reacts same each time as first time, present at birth (& before)

• second line defences respond to tissue damage caused by pathogens or ‘mechanical’ means

portals of entry: eyelashes, tear duct, eyelid, kidney, ureter, urethra

AIM: to keep every invader out/deny entry the SAME way via chemical and physical barriers, protect against portals of entry

1. skin: epidermis, sebum, sweat

2. mucous membranes - mucous, hairs, cilla

3. fluids that protect these surfaces - tears, saliva, nasal secretions and etc

4. defecation, vomiting , couching and sneezing

second line

antimicrobial chemicals

interferon: interfers with viral replication and activates immune cells, made by infected host cells and WBC, effective against bacteria as well

complement: is a set of plama protiens that complements all aspects of the immune response, promote phagocytosis and cell lysis

• these ‘support’ immune cells

• phagocytes

cell eating

• fixed or free, attracted to the affected site by chemotaxis, destory bugs and clean up dead tissue, and this occurs in connective tissue

• natural killer cells

immune surveillance, targets large abnormal cells (bacteria in interstitial fluid, virus infected cells, cancer cells)

fever

• systemic response

• temperature regulator in hypothalamus is rest

• body tries to attain temperature above 37.2 degrees

• help by destroying bugs whose enzymes cannot work at high temperatures

• higher metabolic rate to help healing

inflamattion (second line)

localised response

• damaged cells send out chemical messages: histamines

• body responds with inflammation and this process is supported by phagocytosis

• destroys and removes antigens: immune response

• limits effects of injurious agent

• cleans up dead tissue and debris

• promotes healing

5 key signs: redness (needing to get more blood to site, vasodilation), heat (blood carrying a lot of warmth), swelling (vessels are dilating and capillary permeability - more immune cells are travelling and limits pathogen that can get out and get into the bloodstream) & pain

5th - loss of function - considered variable

third line

specific - ACQUIRED OR ADAPTIVE

• specialist/targeted defence against one type of antigen

• acquired during life - through exposure - need immunity

• third line defence

third line defences

• develops an exposure to a particular antigen

• antigens from microbes

• uses B and T lymphocytes made in bone marrow

• B cells mature in bone marrow

• T cells mature in the thymus

• specific: 1 antigen = 1 response

• versatile: many threats

• memory formed after first exposure

• tolerance must exist towards own cells (antigens)

HUMORAL IMMUNITY: b lymphocytes

• b cells produce antibodies that fight against antigen, these antigens can inactivate or target antigens for destruction

  activation of these b cells is via phagocytosis or antibodies attached to the surface of b cells

  • in the fluid (extracellular enviornmment), thus targets extracellular pathigens (bacteria)

TWO WAYS TO ACTIVATE B-CELLS:

1. phagocytes (antigen present cells), engulfs bacteria and presents the antigens to a helper T cells

2. antigen attached to the antibodies on the surface on B-cells

CELL MEDIATED IMMUNITY - t lymphocytes

t cells come and find the pathogen and kill it directly by cytotoxic t cells releasing cytokines

cells involved - cytotoxic t cell, t helper cells ( these cells aid in maturing B cells and the activation of other T cells and macrophages), t memory cells

• in the cell (intracellular) - thus target intracellular pathogens - viruses

antigens

ANTIGENS:

• made against antigens

• stay in blood and lymph nodes or attached to B-cells

• can be measure in blood: titre

• 1 antibody type for each antigen = match

• inactivate and/or target antigens for destruction

four key properties of adaptive immunity

versatility: a small number of lymphocytes are ready to confront any antigen at any time, even though there are millions of possible antigens out there, & many threats possible

memory: formed after first exposure - ability to remember past injections by generating memory cells

specificity: the immune response is unique to the antigen it encounters

tolerence: ability to distinuish between self and non-self, and understands what not to attack and what to destory/attack

• if the immune system attacks self cells this is known as autoimmune disease