WK 2 BIOL Microbiology

Includes Topic 2A, 2D,2B,2C

What is a microorganism?

• Tiny living organisms

• Living meaning it can produce independently

• Viruses and prions are not ‘living’

• Essential for decomposition and recycling

• Affect everyday life

Prokaryotes have/are

Are small (<5mm)

Always unicellular

Organelles

NO MEMBRANE

Asexual reproduction

NO NUCLEUS

Eukaryotes have/are

Larger (>5mm)

Multicellular often

Organelles have membrane

Sexual reproduction or Asexual

Nucleus

Cytoskeleton

No cell wall (Human)

Viruses (microorganism)

• Not ‘living’

• No cellular structure

• Protein capsule around DNA or RNA

• Can mutate, therefore antibiotics can become ineffective

Bacteria

• Prokaryotic

• Mostly unicellular

• Have cell wall (THICK)

  e.g. Salmonella, golden staph, syphillis

Protozoa

• Eukaryotic

• Usually motile

  e.g. Giardia (GI), Malaria, Cryptopur

Fungi

• Eukaryotic

• Uni or multicellular

• Cell wall

• Produce spores

  e.g. Tinea, Ringworm, Aspergillus (enjoy dark places with moisture)

Helminths

• Eukaryotic

• Multicellular

• Large (seen by naked eye)

• Eggs, larva, adult - can’t lay eggs in human must escape

  e.g. guinea worm (tape worm infestation)

Bacterial requirements

Temperature 10c - 39c (variable)

• Pathogenic bacteria love ¬37c, will often infect humans (induces fever)

• Thermophile = 60c

• Mesophiles = 25-30c

• Psychrophiles = 10c

Oxygen

• Aerobes = only O2

• Facultative aerobes = do either

• Anaerobes = no O2 (can enter when blood is low)

What does a grain stain mean?

It is a tool to expose and visualise bacteria

Gram positive

• Thick layer of peptidulgyncan

• Can form spores

• Reinfect

Gram negative

• Reinforced with 2nd membrane = harder to kill

• Produce endoxtins (harmful to natural cells)

Some antibiotics can work on both = initial trials of antibiotics are given when unsure with type

What is normal flora?

This is beneficial bacteria that is on the skin, mouth, throat and large intestines.

While this is beneficial it becomes an issues when flora escapes its usual area

How to manage the transmission of microbes?

• Break the chain of infection

• Slow down transmission

How do microbes get around?

• Contact - directly/indirectly

• Vehicle - air, water, food,

• Vector - via animal (mosquitos, ticks)

• Vertical - intervene + post partum (mum + baby)

What is the chain of infection?

1. Infectious agent (tells us: it transmits, infects patients)

2. Reservoir (where it sits)

3. Portal of exit

4. Mode of transmission

5. Portal of entry

6. Susceptible host

How to break a link in the chain of infection?

• Sterilisation - destruction/elimination of ALL microbes

  e.g.

  • Heat - dry/burning, moist/ boiling

  • Heat + pressure e.g. autoclave

  • Radiation

  • Filtration

  • Chemical e.g. bleach, hydrogen peroxide

• Disinfection - elimination of MOST pathogens from inanimate objects (not bacterial spores)

  • Chemical e.g. alcohol, chlorine

  • Gas e.g. formaldehyde

• Sanitation - safe disposal of human urine + faeces

The skin

• Covers the entire body

• Largest organ in the human body

• A major component of the integumentary system (skin, glands, nails, hair)

The skin: structure

3 prominent layers

1. Epidermis - outer exposed to external environment

2. Dermis - deep tissue, sweat glands, hair

3. Hypodermis - deeper drugs given to, subcutaneous fat cells, not really apart of the skin

What are the cell types of the epidermis?

1. Keratinocytes- abundant, produce keratin

2. Melanocytes - produce melanin

3. Langerhans cells - macrophage cells activate immune system, originate from bone marrow

4. Merkel cells - nerve endings, function as sensory receptors in strata layers

What are the two general types of skin?

1. THICK

   • Five layers, cover palms, fingertips, soles of feet

2. THIN

   • No stratum lucida

   • All layers thinner than thick layers

   • Covers rest of body

Dermis

• Makes up bulk of skin

• Composed of connective tissue (collagen + elas)

• Highly vascularised

• Highly innervated

What are common cell types of the ‘dermis’?

• Fibroblasts

• Macrophages

• Some macrophages

• White blood cells

What are the layers of the ‘dermis?’

1. Papillary

   • Thinner, superficial to reticular layer

   • Sits directly underneath stratum basal of epidermis

2. Reticular

   • Thicker

   • Deep to papillary layer

   • Lots of collagen to stop penetration

Hypodermis

Subcutaneous layer (not really apart of skin)

• Lies beneath dermis

• Also know as ‘Superficial fascia (band)

• Anchors the skin to underlying structures + stores fat

Skin: What are its functions?

• Protection (exposed to bacteria, abrasions, temperature, chemicals)

  = barrier

• Body temperature regulation

• Cutaneous sensation (sensory receptors allow to feel touch, pressure)

• Metabolic (produce vitamin D for calcium + phosphorus absorption)

• Blood reservoir (Dermis highly vascularised - blood can be redistributed)

• Excretion + absorption (removal of nitrogenous wastes, e.g. urea, ammonia, uric acid, salts in sweat) & (absorbs vitamins ADEKO2)

Chemical barriers

Skin secretion, melanin

Physical barriers

Continuity of skin, waterproof

What does the lymphatic system do?

1. Drain excess fluid and proteins from all tissues back to blood circulation

2. Defend the body against external and interna threats (immunity resistance to disease)

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

Who is contributing to this process? (lymphatic system)

1. Immune cells

2. Lymph fluid

3. Lymph vessels

4. Lymph organs and tissues

5. Lymph nodes

   Lymphocytes - key

   • Produced in bone marrow

What’s lymph?

“Fluid’ in the connective tissue that contains lymphocytes + macrophages

How does lymph get around?

Flowing through special tubes from tissues to venous system and heart

(lymphatic capillaries + lymphatic vessels, trunks, ducts)

Who are capillaries?

They have thin walls resembling veins, but have more valves

They have lymph nodes at intervals and respiratory and muscular pumps to promote flow of lymph towards large veins/heart

Heart

• Vessels unite to form 2 thoracic ducts

  • R side head, arm + chest empty into R lymphatic duct

  • L side lower body empties into main thoracic duct (largest vessel)

  • Lymph from ducts flow into L & R subclavian veins

Lymphatic tissues + organs: what are the layer

• Primary lymphatic organs

  • red bone marrow

  • thymus

• Secondary lymphatic organs

  • Spleen

  • Lymph nodes

• Diffuse lymphatic tissue

  • tonsils, adenoids & Peyer’s patches

Where is red bone marrow found?

• In flat bones

• At the end of long bones (contains haemopoietic stem cells)

• Produce and mature B cells and pre-T cells (lymphocytes)

What is the thymus gland?

• Largest in infancy and reduces in size throughout the lifespan

• T-cells mature here

• Thymus makes thymosin hormones for development and maturation of T cells

What are lymph nodes and there role in the lymphatic system

• guards/check points

• They filter lymph - bring foreign material to the node (gets trapped in fibres, destroyed by macrophages, B+T cells - this results in efferent vessels leave the node with cleaner lymph

• Reside along lymphatic vessels (*neck)

• Multiply lymphocytes “finishing for B cells”

What is the spleen and its role in the lymphatic system

• Between the stomach and diaphragm

• Macrophages remove worn-out or defective RBC’s, WBC’s and platelets

• Stores and releases blood cells

  • Site of production of blood cells during pregnancy 2nd trimester

MALT

Mucosa - Associated - Lymphoid Tissue

• Nodules scattered in connective tissue layer in mucous membranes

  e.g. tonsils, Peyer’s patches (in small intestine + appendix)

Oedema what is she?

The excessive accumulation of interstitial fluid in tissue spaces due to

• Elevated BP

• Obstruction of lymph flow