Foundation Block Flashcards
Explain the principles of preparing tissue for examination under the light microscope.
Requires Fixation: Prevents breakdown of cellular material, antibacterial and toughens tissue - Formaldehyde (formalin) Embedding: Wash with alcohol then replace with xylene which is able to take up paraffin much better (this further stiffens tissue) Sectioning: Involves cutting the sample to the correct size Staining: Different stains used to show the cells (typically H&E)
What does Haemotoxylin stain and what colour is it?
Haemotoxylin binds to acidic or -ve charged compounds (such as phosphate on DNA). The compound is known as basophilic.
It displays as blue/purple colour.
What does Eosin stain and what colour does it show?
Eosin stains positively charged molecules (such as amino group found on amino acids). Mostly stains proteins. The compounds stained by Eosin is known to be acidophilic or eosinophilic.
It is seen as a orange/pink stain
What does amphophilic mean?
This is a compound that is stained by both H&E such as cytoplasm of cells with abundant RER. (DNA and protein)
Priniciple of Immunohistochemistry?
Use antibodies with specific component to target to bind to it. The antibody will then attach to that compound. An enzyme is attached which will change colour when a substrate it added to it.
What are the four basic tissue types?
Connective tissue, Epithelia, Muscle and Neural tissue
What are parenchymal and stroma?
Stroma: Support tissue
Parenchymal: Functional cells
What are the three types of Connective Tissue?
- Embryonic connective tissue
- Connective tissue proper (this is the tissue that supports the parenchymal, blood vessels and epithelial). There are loose, dense, regular and irregular.
Loose connective tissue has more ground substance in it.
3.Specialised connective tissue (found in bones, cartilage, adipose tissue, blood, haemopoietic and lymphatic tissue)
How much blood in a 70kg person?
5L
Function of the Blood?
Tranport nutrients, O2, hormones, heat, cells, immune cells, waste, CO2
What proteins are found in the plasma?
Albumin, Globulins (includes immunoglobulins and antibodies), coagulation proteins
What blood cells are there?
RBC, WBC and platelets
WBC: Granulocytes - Neutrophils, Eosinophils, Basophils
Mononuclear leukocytes: macrophages and lymphcytes
What is haematocrit?
RBC Volume/Blood volume (should be about 45%
Cell charisteristic of RBC?
Biconcave disc, no nucleus or organelles, contains haemoglobulin and transports O2 and CO2
120 days in blood
What are Reticulocytes?
These are immature RBC without nucleus but has some organelles and RNA. This is how they are released into the blood. Normablast are more immature than reticulocytes (still have nucleus).
What are platelets?
Platelets are cell fragments that contain various granules (release factors for blood clotting - thromboxane and attack neutrophils). Involved in haemostasis.
Life span: 8-10 days
What is diapedesis?
Movement of blood cells through intact capillaries (transmigration)
What are neutrophils and its characteristics?
Polymorphonuclear leukocyte, phagocytic, degranulate (myeloperoxidase, lysozyme and colleganse).
Life span of several, cells part of the acute immune system, rarely found in tissue.
Explain Eosinophils and its characteristics
Granular WBC, biloped nucleus, eosinphilic (stains pink), involved in allergy and binding to parasites (IgE).
Explain what basophils are and their characteristics.
Biloped nucleus, basophilic granules (stains blue in cytoplasm), degranulates histamine
What are lymphocytes and it function and charactertics?
These are WBC that include B,T and NK cells. Slightly larger than RBC, round densely stained nucleus with thin cytoplasm.
Immune functions
What are monocytes and its characteristic?
Similar to lymphocytes with eccentric oval or bean shaped nucleus (paler) with more cytoplasm than lymphocytes.
Found in the blood stream as precursor to macrophages
What is the function of bone marrow with blood?
Site of blood cells and platelet generation - specifically immune function (B lymphocyte differentiation)
What is the process of haemopoiesis and explain how it works?
This is generation of Blood Cells that occurs in bones (adult) or liver (fetal).
Begins with haemopoietic stem cell, which proliferates then diffierentiates to either myeloid or lymphoid linage to form cells (depends on different signals).
What is the significance of red and yellow bone marrow?
Red BM is haemopoietic, Yellow is adipose tissue. New borns all bones are red. With age the axial skeleton is red and the proximal femur.
What is erythropoiesis and its process?
Common progenitor cell divides then differentiates.
Haemopoietic stem cell ->Pro-erythroblast -> normalblast -> reticulocytes
As you differentiate the nucleus gets smaller until its gone.
What linage does myeloid precursors lead into?
Myeloid pathway that produces all the blood cells except for B, T and NK cells.
For the four basic tissue types list their corrensponding embryo germ layer that they originate from.
Neural tissue - ectoderm
Muscle - mesoderm
Epithelium - all three
Connective tissue - multipotent mesenchymal stem cells from mesoderm
Explain what connective tissue is and its function?
The connective tissue makes up a large continuous compartment of the body.
Compromised of a few cells, large ECM (fibres and ground substance).
It provides structure, strength, metabolic and defensive functions.
What are fibres and the two types?
Fibres of connective tissue are mostly proteins produced by fibroblasts.
The two main types are elastin and collagen (this includes reticulin type 3)
What are collagen fibres and some characteristics?
Collagen fibres are the most abundant, flexible, strong, Wavy under LM.
Consist of three alpha-chains of polypeptide that forms helix.
What are the types of collegens?
There are 27 types but need to know:
I - connective tissue proper
II - cartilage, IV disc
III - forms reticular fibres
IV - basement membrane
VII - anchoring fibrils to BM and ECM
What do tendons and ligaments fall under in the connective tissue types?
It is dense connective tissue proper that has highly organised collagen.
What are reticulin fibres made of and its function?
Collagen type III, thin fibres and provides framework for certain tissues (bone marrow, liver).
- Does not stain H&E, must use silver stain
What is elastin and its function?
Elastin is made up of a core elastin and fibrillin microfibrils. It founds to provide elasticity in areas such as the aorta, lung and skin.
What is ground substance?
Ground substance has high water content which cannot be stained with H&E.
Made up of GAG (glycosoaminoglycans - long unbranched polysaccharides) and glycoproteins.
Hyaluronic acid - GAG but not linked to proteins (most abundant in loose connective tissue) - negatively charged so it attracts Na+ and stains blue.
Glycoproteins involved in deposition and orientation of fibres - links cells and matrix (fibrillin, laminin and fibronectin)
What is the ECM and its function?
The ECM is made up of fibres and ground substance, has various roles in support, metabolic, control of cell differentiation, binding growth factors, scaffold for cell proliferation, continual remodelling, important in haemopoiesis etc
What are the cells found in the connective tissue?
There are fibroblasts found in the connective tissue.
Resident cells: macrophages, mast cells, myofibroblast, adipose cells, haemopoietic cells.
Wandering cells: lymphocytes, eosinophils, plasma cells, basophils etc
What do fibroblasts do and look like?
Fibroblast synthesised the ECM and has an elongated cell nuclei.
What are the cells/organelles shown in the EM?
Nucleus, RER and collagen filaments
What are macrophages and its functions?
Macrophages are phagocytotic cells involved in the immune response and wound healing. Also clears up debris and very important in inflammation.
Oval or bean shaped nucleus which is found towards one side of the cell.
What are mast cells and its function?
These cells are similar to basophils (they are granular), that release histamines, involved in the inflammation pathway
What cells are wandering cells?
Eosinophils, basophils, plasma cells and lymphocytes
What is the function of connective tissue proper?
It links and supports organs and the body, mediates nutrient transfer (must pass through this to reach cells).
What do the different density of connective tissue proper refer to?
The density refers to the density of collagen. It can be loose or dense. The thicker it is the less ground substance there is.
Dense connective tissue regular: tendons and ligaments
What is adipose tissue and its function?
These are cells that specialise in lipid storage. White has one droplet in the cytoplasm. Yellow has multiple droplets.
What is cartilage and its function?
This is specialised connective tissue involved in compression and flexibility. Proteoglycan ground substance is abundant (highly negatively charged - stains very purple).
Collagen type III - the cells are chondrocytes
Main type of cartilage is hyaline.
What are bones made of?
These are rigid and strong support structures of the body.
Collagen type I matrix (osteoid) and the connective tissue cells are osteoblasts and osteoclasts
What is the basement membrane, its location and function?
Lies between the support cells and parenchymal cells (such as epithelia).
Made up of collagen VII (binds BM to underlying tissue) and reticulin.
Also made up of collagen type IV, heparan sulfate and structural glycoproteins (laminin and fibronectin)
Cannot see it under the LM with H&E must use different stain (methamine silver)
Provides structural support, control of epithelial growth, selective barrier to nutrients, links epithelium to tissue.
What are the main differences between eukayrotes and bacteria cells?
Much smaller, no membrane bound organelles, single DNA circle, no nucleus, different ribosome size and binary fission in bacteria.
What are the key components of bacteria?
Cytoplasmic membrane, matrix, ribosomes, genome (chromosome with/without plasmids) and cell wall
Important of cytoplasmic membrane for bacteria
Essential for survival which contains proteins and lipids. Allows selective interaction with environment (entry of nutrients and exit of waste).
Location for many processes because proteins can be located in it (respiration or pseudo ER)
Cytoplasmic matrix and its impact on the bacteria cell?
It is hypertonic (relatively) so water enters the cells and will cause it to burst. But the cell wall protects this from happening.
Packed with ribosomes
Nucleoid of bacteria and its genetic material?
No membrane, chromosome is single circular DNA, looped and super coiled. No introns or exons.
What are plasmids?
These are circular dsDNA supercoiled that is independent of the chromosome.
E.coli and its respository gene pool?
Each cell has 4000-6000 genes but the entire ‘pan-genome’ has detected over 25000 genes.
This implies optional genes (accessory) on top of the core.
How does E.coli scavenge so many different genes?
Plasmids can move between bacteria, bacteriophages (viruses that afefct bacteria), pathogenecity islands, transposons, integrons
What is the composition of cell wall in bacteria?
Protects cell lysis
Consist of peptidoglycan (polymer of sugar and amino acid). Many targets for antibiotics and main component of PAMPs
What does the Gram stain show in the two different bacteria cell types?
Gram positive: The outside layer consist of the peptidoglycan
Gram negative: This has three layers instead. It has an outer membrane then followed by the peptidoglycan and finally plasma membrane,
Cell wall for Gram negative includes: Outer membrane and peptidoglycan
What is found in Gram positive bacterial cell wall?
Teichoic acids and large amounts of peptidoglycan
What is found in Gram negative bacterial cell wall?
Major feature is the outer membrane, prevents entry of bile salts and antibiotics. The outer membrane can be washed away by alcohol.
Has passageway for larger molecules to pass.
Contains lipopolysaccharide (LPS) that stabilises outer membrane - also acts as an endotoxin (PAMPs)
What is the structure of LPS?
Consists of Lipid molecule –> core polysaccharide (repeating sugar unit).
The repeating sugar units are known as O-antigens.
What are Acid Fast Bacteria?
These do not respond to Gram stains because of a thick waxy wall. It has a peptidoglycan base layer then many additional layers.
This gives it resistance to harsh environments and antibiotics. (Also leads to slow nutrient uptake - slow growth)
What is cocci?
These are circular bacteria.
What are rod bacteria?
These are bacteria that looks like rods…
Explain the process of Gram staining
Stain blue first then wash with alcohol then stain red.
What is homeostasis?
Constant maintenance of internal body environment
Control systems and homeostasis?
These are systems that cause effect to maintain the environment. Usually uses negative feedback.
Understand the element of control in homeostasis
Regulated variable, sensor, set point, comparator and effector
How do stretch receptors: baroreceptors and osmoreceptors work?
Baroreceptor – physical stretch opens up ion channels so that the influx of ions sends signal about the blood pressure.
Osmoreceptors: found in the brain and if there is more water coming in the difference in osmolality will be detected by the cell enlarging (water enters it).
What are effector signals of chemical and electrical and their impact?
Chemical - hormones
Electrical - nerve impulses
Fast vs slow. General vs localised response.
There are systems that mix the two such as adrenal glands and kidneys (renin - sympathetic)
What are the possible changes in set points?
Set points can change with circadian variation, aging and response to persistent changes in ambient levels
What are the implications of homeostatic clashes?
Sometimes two variables will contradict what the effectors will do. Such as blood pressure and body temperature while running on a hot day. The body will prioritise the blood pressure first because of the brain oxygenation importance.
What can we regulate blood pressure?
Heart rate, stroke volume and total peripheral resistance
What can control glomerular filtration rate?
Pre and post glomerular tone and mesangial cell contraction (structure associated with the capillaries - by contracting it)
Where is human thermoregulation conducted?
This is done in the hypothalamus with separate heating and cooling centres (by integrating both inputs from central and peripheral receptors)
What are the differences between central and peripheral thermo-receptors and where are they located?
Central receptors are used to detect warmth and generally found in the spinal cord.
Peripheral receptors are used for both cold and warmth (typically the skin) for preemptive warning of oncoming changes in ambient temperature.
Places to measure core temperature?
Sublingual, ear canal and rectal (this is the best method - least affected by ambient temperature)
Temperature variation occurs greater in the very young and very old. Diurnal variation (higher temperature in the late afternoon) Menstrual variation is 1 degrees higher post-ovulation.
What the thermal energy balance for the body?
Body heat generation + heat gained by radiation = heat loss by body
What are the different ways that the body can lose heat?
Radiation, conduction, convection, radiation and evaporation.
Many of these are dependent on moving down a thermal gradient.
Thermoregulatory control centres and how it regulates the body core temperature?
Sympathetic outflow to skin arterioles and sweat glands for cooling.
Stimulation of motor nerves to begin shivering for heating
What are the body’s acclimatisation to hot climates?
The sweating occurs sooner, more sweat volume but lower [Na+] in sweat
Describe fever and its how it begins?
This occurs because of the change in set-point temperature induced by pyrogens (whether it may be exogenous or endogenous).
Synthesis of PGE2 which is inhibited by aspirin.
Shivering occurs because the body is trying to increase the temperature by trying to reach the new set point.
Chills:
Heating mechanisms activated as set-point rises (Shivering)
Crisis:
Cooling mechanisms activated as set-point falls (sweating)
What does the immune system need to be effective against pathogens?
- Recognise self/non-self
- Should be present since birth
- Rapid reaction
- Response must be appropriate for the microbe
What are the two types of immunity and do they communicate with each other?
There is the innate and adaptive system and yes they do communicate with each other. The variation in innate signalling will shape the adaptive response to particular microbes.
What are main differences between the innate and adaptive immune system?
Innate differences: recognises PAMPs (generalised), rapid response, no memory, components include physical barrier, antimicrobial chemicals, phagocytes, NK cells and others (adaptive components: lymphocytes, antibodies and cytokines)
What is the overall process of the immune system (time flow from the initial exposure to pathogen)
Recgonition > effector function (innate, maybe immunity) > immunological memory > immune system regulation
Sometimes immunopathology due to damage by or failures in the immune system
What are PAMPs and PRR, who uses these?
Pattern recognition receptors bind to PAMPs which are shared molecular patterns found on pathogens. This induces a signal cascade.
These include TLR (toll like receptors) and NOD-like receptors
This is the recognition system used by the innate immune system
What are TCR and BCR and who uses these?
These are antigen receptors used by T and B cells in the adaptive immune system. It also includes antibodies generated.
These receptors recognise very distinct molecular patterns that seperate from self.
What is an antibody and what are their components?
Antibodies are immunoglobulin that binds to specific antigens.
It has a constant region (for isotype - different effector) and variable region (for the specific antigen)
It can be found in soluble form or bound to BCR (is the BCR)
Where do the immune cells originate form and what linage do they belong to?
All immune cells originate from the haemopoietic stem cell which differentiates into the myeloid and lymphoid progenitor.
Lymphoid progenitor produces: NK, B and T cells
Myeloid progenitor produces: Everything else
What are cytokines?
These are proteins secreted by cells that interact and affect behaviour of cells that have the appropriate receptors
What are chemokines?
These are secreted proteins that attract cells who have the appropriate receptors - by binding to cysteine containing receptors (CCR, CXCR)
Some characteristics about Cytokines
May be constitutively produced or only on activation. Different concentrations lead to different effectors. Inhibition or activation of cytokines produces many outcomes.
Where are most of the immune cells located?
Most of them are found in the blood circulation and only a few resident macrophages and dentritic cells are found in the tissues.
Leukocyte migration in the normal body?
Leukocytes are first found in primary lymphoid organ which then circulate into the blood and into the secondary lymphoid organ (spleen, lymph nodes and MALT - mucosal associated lymphoid tissue).
This circulation completes a whole cycle 24 hours for T cells. Some macrophages and dentritic cells move into the tissue.
Leukocyte migration when infection occurs?
Leukocytes from the blood into tissues by interactions with endotheliel cells. Which then bind to PAMPs on the pathogen and activate their effectors.
The lymphatics carry microbes to the secondary lymphoid organs where they bind to specific antigen. Once T and B cells are ready they will re-enter the tissue through the blood circulation.
What are the components of the lymphatic system?
Lymph nodes: sample antigens from skin and internal tissues
Spleen: samples antigens from blood
MALT (Mucosal associated lymphoid tissue): samples antigens from mucosal tissues, about 50% of lymphocytes are here.
Naive T and B cells migrate from the blood through specialised vessels called high endothelial vessels (HEV) to specific areas (paracortex and cortex - the paracortex holds T cells)
What are the roles/functions of each specific immune cell? (Neutrophils, macrophages, NK, eosinophil, basophil and dendritic cells)
What are the roles/functions of the adaptive immune system? (B cells, antibodies secreted, T (helper and cytotoxic) cells)
What is the role of T regulatory cells?
These cells act to suppress the immune system in case the system is activated for too long which may cause damage instead.
What are extra structures that are available to bacteria to use?
Flagella, fimbriae (pili), capsules and endospores
What is the flagellum made up of and its function?
It is composed of thin, long, hollow helical filaments (which contain flagellin protein).
Its function is to provide the bacteria with motility.
It is also the determinant of the H-antigen in E.coli
What the components of fimbraei (pili) and its function?
Made of the protein pilin and its function is to attach to other cells and each other. Sex pili can transfer plasmids between bacteria.
What are capsules that surround bacteria, its components and functions?
These have polysaccharides extending from cell surface. It’s hard to wash off and makes the colonies look shiny.
Seen by negative staining.
It functions to protect the bacteria from dehydration, virulence and protects against phagocytosis.
Bacillus Anthracis
Name, Shape, Gram Staining, Aerobic?
Bacillus are rod shaped bacteria, Gram +ve, produces spores, aerobic, causes Anthrax and is encapsulated
What are endospores and their characteristics?
Endospores are highly resistant dormant structures that do no replicate. They are very resistant to heat, UV and chemicals. Hard to stain and sporulation occurs when growth ceases (lack of nutrients/moisture)
Clostridium tetani
Causes tetanus, strict anaerobe, Gram +ve, Rod, capable of forming spores
Clostridium Perfringens
These fall under the same family as Clostridium tetani - just that the spores are found within the cells instead.
What form of replication does bacteria use and what does the Bacterial Growth Curve include?
Bacteria uses binary fission. The curve consists of lag phase, log phase, stationary phase (toxic substances released by the bacteria itself)
What are the typical means of acquiring nutrients through the cell wall?
Passive diffusion, facilitated diffusion and active transport
Different classification of bacteria based on final electron acceptor (energy generation)
Respiration: oxygen
Anaerobic respiration: Inorganic compound (not O2) - such as sulfur oxidising bacteria
Fermentation: organic compound (often when oxygen is used up)
Different types of bacteria relationship with oxygen
Strict anaerobes, strict aerobes, facultative anaerobes, aerotolerant anerobes and microaerophiles (best in O2)
Explain the principle of some biochemical testing for bacteria
Top row is before the tubes are inoculated. Bottom row has been inoculated. The particular tube is looking for specific characteristics. The middle tube went from purple to yellow because acid has been produced. Gas is also trapped. This looks at the ability of bacteria to ferment glucose to produce formic acid (HCOOH). Formic dehydrogenase HCOOH —> H2 + CO2, this gas is trapped in the tube.
What is the principle behind MALDI-TOF (Bacteria identification by Mass Spec)
Bombard the bacteria till it breaks down then measure the masses of the components using MS
Use of Genome sequencing in bacteria identification
Can genome the bacteria DNA to identify the exact species to allow for proper treatment
What are the classification methods of Bacteria?
Phenotype - Morphology, biochemical behaviour, surface antigens
Genetic make up
Defined as species if >97% related and genera if >95% related
Techniques used to identify Bacteria listed
- Microscopy
a) Unstained - darkground (e.g., syphilis), phase contrast (e.g., cholera)
b) Stained - Gram, Ziehl-Neelsen, capsule, spores. - Culture
a) Indication of growth requirements, e.g. atmosphere (anaerobes); temperature; nutritional
requirements; resistance to inhibitory compounds, e.g., bile salts
b) Colony morphology - size, shape, pigment, texture (smooth or rough), haemolysis (e.g.,
Streptococcus), swarming. - Proteomics
Identification of species-specific proteins by using mass spectrometry on intact or lysed cells - Genomics
Determination and analysis of 16S rDNA or other sequence, including whole genome - Detection of structural antigens
a) For rapid diagnosis: by immunofluorescence, direct agglutination or latex agglutination
b) To determine serotype - Susceptibility to bacteriophages and bacteriocins
Mainly used by reference labs to subtype certain bacteria. Will be superceded by sequencing - Production of toxins and other virulence determinants
Mostly done by testing for virulence-associated genes. Can be determined from whole
genome sequence - Pathogenicity for animals.
Seldom done, but may be required for forensic testing.
What are the two types of epithelial tissues?
There are surface epithelium (lines surfaces and lumina - e.g. skin, GI, respiratory system, kidney and reproductive tract) and glandular epithelium (involved in secretion - single cells, invagination of multiple cells forming glands, solid organs).
What is the function of the epithelium?
It is for protection, secretion, absorption, barrier and receptors (smell and taste)
What are the characteristics of epithelial cells?
The cells have a polarity: apical, lateral and basal domains. They are connected by a cell junctions and supported by a basement membrane. It is avascular (nutrients must diffuse from surrounding tissue)
How are surface epithelium classified?
Number of layer (simple and stratified - type is determined by top layer cells), shape of cells (squamous, cuboidal, columnar) and surface specialisation (cilia or keratinisation)
What are simple squamous cells good for and where are they found? What do they look like?
They are flat cells which are good for selective diffusion of nutrients in specific regions.
Found in the mseothelium (lining of body cavity), endothelium, lining of alveoli, glomeruli
What are simple cuboidal cells and where are they found?
These are cells that look like cubes found in the thyroid follicles and renale tubules. These types of cells are generally used for secretion and absorption (used in many ducts).
What are simple columnar and where is it found?
These are tall cells (but not as wide) with an oval nucleus at the base. There are non-ciliated (stomach, small and large intestines, gall bladder and bile ducts, endocervix).
There are also ciliated ones (fallopian tubes and bronchioles - used to move mucus around with)
They mostly cover the digestive system and upper respiratory system
What are pseudostratified ciliated columnar and where is it found?
These look like if multiple cell layers are present but in reality it is just a single layer of columnar cells with cilia. This is found in the respiratory tract.
- If it is non-ciliated it would be found in the epididymis and vas deferens
Also involved in secretion and absorption
What are stratified squamous and where is it located?
These have multiple layers of cells typicall with cuboidal cells at the base and squamous cells at the top.
Keratinising: skin
Non-keratinising: found oral cavity, oesphagus, anus, vagina, ecto cervix
What are stratified cuboidal and where are they found?
These are multiple layers of cuboidal and are found on ducts
Surface columnar layer overlying myoepithelial
This is found in glands because the myoepithelial contraction forces the contents to come out.
Salivary glands, Mammary glands (breasts), sweat glands
Surface columnar layer overlying basal layer
These are found on prostate
Transitional/Urothelium
These have a basal layer of columnar and the top layer is umbrella cells (which is able to accomodate for changing sizes) this is found on the renal pelvis, ureter and bladder.
What are the structures found on the apical surface of epithelia and their contents?
Microvilli, cilia
Microvilli - increase surface area by 20 times and contain cytoskeletal element
Cilia - are longer finger projections of microtubules that allow movement (found in the respiratory tract or fallopian tube)
What are the three components to intercellular junction (junctional complex)?
From apex to base of cells
Zonula occludens > Zonula adherens > Macula adherens (Desmosome)
The function of Zonula occludins as tight junctions?
They act to limit the passage way for what goes between cells
The components of adheren junctions and its functions?
There is the zonula and the macula adherens, cadherin is a transmembrane protein where the cadherin protudes from the two cells into the gap. In the plaque there are catenins that links the cadherins to the actin (cytoskeleton). Defects in these two proteins means that the cells do not adhere well. Cancer cells dissociate and invade other parts of the body, this is why the two proteins are so important
-Mechanically strong attachment between cells (links cytoskeleton)
What are gap junctions?
These are communicating junctions (allow selective movements of molecule between cells)
What are hemidesmosome?
These are modified desmosomes that links epithelial to underlying basement membrane (not cadherins it is integrins which act as TM protein)
What are Cell adhesion molcules (CAM) and role do they have?
TM proteins that link to other CAMs on other cells. Functions in cell adhesion, communication, cell movement and differentiation.
What are the four main groups of CAMs?
Cadherins, integrins, selectins and immunoglobulin superfamily (ICAM, CCAM, PECAM - for homotypic cell-cell adhesion)
What are the functions of the basement membrane?
Structural support, control of epithelial growth, links epithelium to underying tissue and selective barrier to nutrients.
Underlying basement membrane
What are mucosa membrane, where are they located?
Found on the body that is exposed to the external environment (resp and GI)
Has epithelium, underying connective tissue (lamina propria) and sometimes SMC (muscularis mucosae).
Has glands to secrete mucus
What are serous membranes and its location?
These are found in the body cavity and lines the peritoneal cavities, pleural, pericardium
It has surface mesothelium and supportive connective tissue.
What are glandular epithelial cells and the difference bteween endocrine and exocrine?
Exocrine secretes on the epithelium or into a duct.
Endocrine secretes into the blood.
These glandular epithelia can be single celled, invaginations or solid organs.
What are the three types of exocrine gland structures?
Simple tubular - colon
Simple coiled - sweat glands
Simple branched tubular - stomach
What do exocrine glands secrete?
Lipids, proteins, mucous (glycoprotein) and serous (protein)
What are goblet cells and their functions?
They secrete mucus from mucus droplets. Unicellular glands.
What are serous acini and its function?
Serous cells are secretory units (cuboidal) which are called acini. Secretes into a lumen.
What are myoepithelial cells and what are they a part of?
These are epithelial cells that can contract usually found on glands that require extra release.
Mammary, salivary and sweat glands.
Difference between labile and stable cells?
Labile cells are continuous going through the cell cycle and dividing.
Stable cells are outside the cycle waiting for signals to divide.
What does rotavirus cause?
It causes diarrhoea and only recent have been able to put forth a vaccination.
Why is it difficult to develop vaccination for some viruses?
The virus may target the T-cells themselves which are essential (HIV).
Viruses that incorporate their genome into our DNA also makes it very complicated to vaccine against when they go dormant
What are viruses are what aren’t they?
Viruses are strands of genetic elements which are obligate parasites. They are not cells. They are unable to self-replicate on their own or have motility (no metabolism)
What are the components to a viral particle?
Genome, capsule (protective protein shell), nucleocapsid (capsid most closely associated with the viral nucleic acid), envelope (lipid membrane), matrix (protein layer that connects the capsid and envelope glycoproteins).
Genome + capsid (core component) = virus
Viruses cannot be seen by normal LM so we need to use…?
Electron microscopy or use of light that have a much smaller wavelength (such as X-rays)
The capsid is a very important component of viruses, how is it arranged from capsomers?
Capsids are actually icosahedral capsids which means they are made up of 20 planes. The capsomers are different sized so give particles a different look.
Or it can be made up of a helical capsule (which is also enclosed by an envelope) usually found as the nucleocapsid.
What are complex symmetry virus particles?
These are not like the standard icosahedral and helical structures. These are much larger and complex out of all the viruses.
Multiple shelled capsid confer…?
A very hardy virus because of the thick layer that allow them to survive harsher environments. Such as rotavirus surviving in the GI tract.
How does influenza virus acquire a lipid membrane?
Some viruses acquire a lipid capsule by budding it off from the host cell membranes.
What are the benefits of using X-ray crystallography to see the viruses?
This allows us to analyse the specific shape of receptors found on viruses. Help us develop virus-receptor-antibody interactions that may lead to vaccines.
How do we classify viruses and why do we do so?
Classification by: type of genome, mode of replication, morphology of virion - determines family
For species we look at: arrangement of genes, sizes of proteins, serological reactions and the disease it produces
Useful to classify so we can predict how new viruses may behave.
All helical viruses must have a lipid envelope.
They are also only found in RNA there are NO helical DNA viruses.
What are the pathological/epidemiologic groupings of viruses?
Enteric viruses - intestinal stract
Respiratory viruses
Arboviruses - through insect bites
Sexually transmitted viruses
Hepatitis virus
What are some ways we can detect viruses?
- Use EM
- Grow viruses on culture - gold standard (this is actually quite hard because of the large variations)
- Detect specific virus proteins
- Host serological response
- Viral gene detection
How do emerging infections come about and why are viruses are adaptable?
Emerging infections generally are infections that appear in a population or had previously appeared but are increasing in frequency.
Viruses have a very high mutation rate (Esp RNA).
Zoonose (species jumping) also introduces a lot of new viruses
The rules to diagnosing infections in a clinical settings…
- Make clinical diagnosis based on history and examination
- Confirm with tests
- Never blindly order tests
What steps are involved in making a specific aetiological diagnosis of infection?
- Demonstrate organism, component or product
- Isolate the micro-organism (gold standard) –> since presence does not imply causality (normal flora)
- Demonstrate a serological response (immune response to that microbe)
Explain how the use of microscopy can be used to demostrate infectious agents
Microscope can be used to identify the agents by using different stains such as: phase contrast, darkground, gram, Ziehl-Neelsen (acid fast bacteria)
Explain the use of electron microscopy to identify organisms and components
When the component or organism is too small to detect with microscopy, EM can be used to very small particles such as viruses.
Principle of using antigen to detect fine microbial presence and detection of organisms.
Antigens are first in the solution > latex particles are attached with known antibodies> once it recognises the antigen it will cross link it
The latex particle causes clumping
This process must have a particular antigen in mind.
Principles of antigen detection with solid phase assay
This time the sample is in a solid state with antigens on it. The antibody will attach to it whilst having a label attached (the label will visual fluorescent - immunofluorescence)
Treponema. pallidum
This causes syphilis
Immunofluorescence is not limited to viruses and bacteria…
It can also be used in anatomical pathology for many biopsies.
The use of immunohistochemistry to identify specific antigen by using indirect immunohistochemistry
This is done by identifying a known antibody that binds to our target antigen. Then the typical labelling occurs.
How do we use capture assay to identify antigens
In this case we use the an antibody to first clean up the sample then wash it. Then use another tagged antibody to make it fluorescent.
What are the techniques that we can use to detect nucleic acids?
Hybridisation and PCR
Explain the principle of DNA hybridisation.
There will be a target DNA. It must be sDNA (by melting) which is allowed to be re-anneal with a probe. The probe has a particular sequence (complementary base pairing) and labelled with a fluorescence or radioactive element.
Explain the principles of PCR in depth.
The target DNA will be melted, a primer of complementary strand is attached to it. DNA polymerase is then used to extend that DNA strand until a new dsDNA is created. This process is repeated multiple of times then it is ran on a gel electrophoresis (to confirm identity).
- Each strand created are of the same length. Despite a longer strand thats created, each time the primer attaches it’s always at the same location. Therefore creating the same length.
After detection of organism has been done, it needs to be isolated - list the steps required for this process.
It is important to attemp to isolate the organism before the patient has been medicated. These are then grown on a culture media.
What are the three types of specimen?
Sterile site: no microbiota
Site with normal microbiota
Sterile site with abutting site with microbiota (sterile passes through non-sterile area)
In order to demonstrate an immune response against a target microbiota - what test is needed?
(Demonstrating an antibody response)
Tube agglutination test (Widal test)
Heat kill the bacteria so they will not infect people in the labs. The heating gets rid of many rubbish on the surface so that the O-antigen is showing easily. The tubes are diluted. Add the bacteria to each tube, there is also a control. When the bacteria binds to the antibody they clump and fall to the bottom so that you can now see the lines in the background. The first tube is a control where the bacteria is in suspension (hanging in the middle) so that we cannot see the lines)
Explain the assay for the patient’s specific antibody IgM
Morphology of necrosis in renal infarct
Well defined demarcation because of the defined blood supply. Necrotic tissue is yellow.
What are the characteristics of skeletal muscles?
These are somatic, striated, multinucleated peripherally muscles that stretch the entire length of muscle.
What are the characteristics of cardiac muscles?
Also striated, works like skeletal muscles, network of single cells instead and can spontaneously contract.
Single nuclei located centrally
What are the characteristics of smooth muscles?
These are NOT striated, spindle shaped (fusiform), these are very good at sustaining long contractions.
Centrally located elongated nuclei
Ultrastructure of myofibres and sarcomeres
The myofibres are made up of repeating sarcomeres. The sarcomeres are made up of the overlapping of actin and myosin.
The Z band anchors the thin filament in the sarcomere (actin)
What are the characteristics of smooth muscle and its ultrastructure
These are spindle shaped cells, with central nucleus but no sarcomeres, myofibrils or t-tubules.
Instead of myofibrils they have dense bodies (which act as Z discs) that bind to myosin and actin
Not as organised as striated muscle - but very similar
What are the contractile and metabolic characteristics of Type I, IIa and IIb muscle fibres?
The different chemistry in each type allows for differential staining.
What the body surfaces’ first line of defense against infection?
There are physical, chemical and biological barriers that prevent pathogens from colonising.
Describe the process of classical pathway activation of the complement cascade
IgM and IgG bound to microbes attract C1q > recruit C1r > forms enzyme to bind C1s which forms the complex that can then initiate the breakdown of C4,2,3.
Now C4b and C2b form a C3 convertase. It produces C3b. If C4b, C2b and C3b come together it produces C5 convertase - MAC
How does macrophages and neutrophils affect leukocyte migration, also name the receptors of all the adhesion molecules involved.
Where is the demarcation of the back area?
T1 vertebra - coccyx, medial border of the scapula, posterior surface of the ribs and the iliac crest.
Describe the typical lumbar vertebra and its boundaries and parts.
Vertebra body with an epiphyseal ring around it. There is the vertebral canal (neural arch) made up of the pedical (root) and lamina (found near the spinous processes) - The shape of the canal is distinctive for lumbar.
There is the spinous process and transverse process (for muscle and ligament attachment).
There is the superior and inferior vertebral notch.
Superior and Inferior articular processes.
What are the two types of ossification, when and where do they begin?
3 primary centres in the body (and each neural arch) begins about 8 weeks.
5 secondary centres at the tip of spinous and tranverse procceses and the upper and lower margins of the body (annular epiphysis).
Secondary centres normally close late adolescence (begins at puberty) when vertebral growth is done.
- May be source of mistake of fractures in young children.
What are the nerve and blood supply to the disc?
Common spinal nerve comes from the posterior and anterior roots joining together.
Posterior is always sensory. Ventral root is effector. The block is the dorsal root ganglia with sensory cell bodies.
Anterior horn of the spinal cord has the cell body of motor neuron.
Cell bodies of sympathetic neurons in the T1-L2
Anterior ramus contains both sensory and motor neurons (goes to the front of the body wall and upper and lower limbs)
Posterior ramus has sensory and motor neurons and it goes to the back and supplies to the intrinsic muscles, skin, joints (fasic).
Outer third of an intervertebral disc is innervated and it can be a direct source of pain. (Also supplied with blood 1/3)
What are the contents found in the vertebral canal?
Spinal cord which is protected by the meninges. From inside out: Pia mater, subarachnoid space, arachoid mater then dura mater. There is the extradural space with extradural fat and venus plexus (anterior internal vertebral)
What is the process of making the large array of diverse BCR?
Diversity is achieved by gene rearrangement of the:
Heavy chain V region: V, D and J.
This V region connects to a constant (C) gene.
Light chain V region: V and J
Which then also connects to constant gene.
- This is all done through enzyme RAG
There are many checkpoints along this process to make sure this process will work where are they?
How does the antibody isotype and affinity look after the primary and secondary exposure to the pathogen?
What are the outcomes of invasion?
Stages of phagocytosis
What are the targets of Extracellular acting toxins?
Intact host cells, ECM and other host molecules (lipids,fibrin, nucleic acids,etc)
What is the structure of TCR made of?
It is an heterodimer of an a and B chain. Encoded by rearrangement of genes (similar to Ig)
TCRa - VJ C
TCRb - VDJ C
NO somatic hypermutation after antigen
Checkpoint - autoreactive cell removed (negative selection) and it receptor can bind to MHC (positive)
What is the structure of MHC I?
Bound to a3 to a2 to a1 then B2m which is not covalently bound to the cells. a2 and a1 groove forms MHC binding cleft for proteins
How does T-dependent B-cell activation work?
Once the T-cell is activated with CD40L and releasing cytokines it drives the proliferation and differentiation of B cells (produces IgD and IgM). Without the CD40 you would only produce IgM.
- T cell very important in isotype switching as long as the associated cytokine is present too
So where does the B and T cell actually meet?
This meeting occurs in the lymph nodes (but the cells are held in separate segments.
B cells - follicles
T cells - paracortex
Macrophages and plasma cells found in the medulla
In chronic inflammation do macrophages have multiple nucleis?
Yes they fuse together to form a giant cell
What do germinal centres and what happens there?
This is the structure where B cells differentiate into plasma cells. The germinal centres are the paler areas. This is a secondary follicle where the B cells are activated and begin to differentiate.
