CRS 1 Flashcards
1
Q
Explain the maturation of the lung in utero.
A
- originates from the endodermal layer
- first forms digestive tube, respiratory tube grows from this then bifurcates into 2 lungs
- there are 5 stages of development:embryonic, pseudoglandular, canalicular, saccular and alveolar
2
Q
Explain the production, composition and role of surfactant in utero.
A
- surfactant is needed to keep the lungs inflated in utero by reducing surface tension and increasing lung compliance
- Consists of sphingomyelin and lecitin
- Secreted late in gestation by Type II pneumocytes
- 4 proteins in surfactant: SPA, SPB, SPC adn SPD
3
Q
Explain the role of SPA in surfactant.
A
Is most abundant. Main role is to prevent lung infection
4
Q
Describe SPB and SPC in surfactant, including their role and biochemical nature.
A
- Have the classical role of surfactant
- Are lipid soluble, hydrophobic and essential for the production of the surfactant film
- Regulate spreading and organisation of phospholipids over the alveolar surface
- Are important during dynamic inflation and deflation of the lungs
5
Q
What is the role of SPD in surfactant?
A
The role of SPD is unknown.
6
Q
What factors can modulate lung development?
A
4 main factors
- Intra-thoracic space
- Intra-uterine space
- Foetal breathing movements
- Lung liquid production
7
Q
Outline how intra-thoracic space can modulate lung development.
A
- The lung needs space to grow
- Can be impaired by congenital diaphragmatic hernia which is relatively common
- Gut fills thoracic space by passing thorugh a hole in the diaphragm
- This impairs lung growth
- Animals can adapt but will usually die
8
Q
Outline how intra-uterine space can modulate lung development.
A
- Adequate space is needed
- Can be impaired by oligohydraminos (lack of amniotic fluid)
- Leads to uterine compression and changes teh foetal posture
- Common cause of pulmonary hypoplasia
9
Q
Outline how foetal breathing movements can modulate lung development.
A
- The must be a negative pleural pressure in order to train the lungs to breath once born
- If no negative pressure is developed during development then the animal will be unable to breath
10
Q
Outline how lung liquid production can modulate lung development.
A
- Liquid inside the lungs (for example surfactant) causes the lungs to blow up
- this stretches the lungs, mimicking breathing expansion and training the lungs for breathing
11
Q
Describe the embryonic stage of lung development.
A
- First stage of development
- Starts as outgrowth of foregut
- Simple epithelial tubes branch out into the mesenchyme and then branch into primitive bronchi
- The right bronchus gives off 3 diverticula, the left gives off 2
- These become lobar and indicate the right lung will have 3 lobes while the left will have 2
- Each bronchus will then develop into smaller bronchi
- bronchioles begin to form
- 17 divisions until the 6th foetal month
- Laryngotracheal groove forms and further budding may be unequal
- creates bronchi and bronchioles
12
Q
Descibre the differences between cardiac and skeletal muscle cells.
A
- Cardiac muscle is not a true syncitium
- Nuclei are centrally located in cardiac muscle cells
- Cardiomyocytes have sarcoplasmic reticula and T-tubules
- Cardiomyocytes have more mitochondria and glycogen
- Cardiac muscle has richer vascularisation
- Cardiac muscle is myogenic
- Cardiac muscle is not innervated by motor neurons
- Cardiac muscle generates is own action potentials
13
Q
Define absolute refractory period.
A
The period following the firing of nerve firbre when it cannot be stimulated no matter how great a stimulus is applied.
14
Q
Outline the psuedoglandular stage of embryonic lung development.
A
- Epithelial tubes invade further into the mesencyme, as well as capillaries
- The epithelium and mesenchyme interact which stimulates budding
- Rapid growth and proliferation of primitive airways and coincides with the formation of pulmonary vasculature
- Diffusion barrier is 60mm compared to 0.2mm at birth
- Bronchi divide into bronchioles
15
Q
Outline the canalicular stage of embryonic lung development
A
- Canaliculi branch out of the terminal bronchioli
- Canaliculi are the respiratory part of the lungs/pulmonary parenchyma
- All air spaces form an acinus (bronchioli, alveolar duct and alveolar sacculi)
- Alteration of epithelium and surrounding mesenchyme along the acinus
- Capillaries surround acini, form foundation for later exchange of gases
- Lumen become wider and some epithelial cells flatten
- Type II pneumocytes differentiate into type I
- Type II produce surfactant, Type I make up difusio surface
- Lungs become more vascular and capillaries organise themselves around epithelind epithelial tubes into a double layered network
16
Q
Outline the saccular stage of embryonic lung devlopment
A
- Sacs form on terminal branches, represent last subdivision of passages that supply air
- Further division will form ducts and saccules (to form alveolar ducts and sacs)
- Primary septa are thick, become invaded by capillaries
- Number of capillaries increases and approach respiratory epithelium
- Future air spaces more dilated
- Elastic tissue appears in sacular walls
- Birth is end of the saccular phase
17
Q
Outline the alveolar stage of embryonic development.
A
- Starts at varying times depending on species
- Around end of pregnancy, overlaps with saccular phase
- New sacculi develop into alveoli due to formation of secondary septa
- Influenced by ECM
- Matrix is mixture of collagen, elastin, proteoglycans and glycoproteins
- provide structural support, influence cell division, differentiation and migration
- Secondary septa growth decreases diffusion distance
- Not complete at birth
- Leads to major increase in surface area
- double capillary network in alveolar wall remodels as single layer
18
Q
Identify the features of external nares present in all speceis and explain their role in airway resistance.
A
- The meatus - hole
- Surrounded by hairless skin (sometimes highly modified depending on species)
- Supported by nasal cartilages (lateral nasal cartilages, vartiery of accessory cartilages, attached to nasal septum, forms opening of nostril)
19
Q
Identify the features of external nares of bovidae and explain their role in airway resistance.
A
- Nostrils surrounded by a smooth hairless nasolabial plate (reduces airway resistance)
- Stratified cornified epithelium
- Serous glands create moisture (nasolabial glands) (allows particles to stick to walls of nares)
20
Q
Identify teh features of external nares of equidae and explain their role in airway resistance.
A
- No ventral nasal cartilages - incomplete cartilaginous ring (distensible nostrils)
- Alar cartilages (plate and horn - form comma shpaed nostril)
- Ventral true nostril and dorsal false nostril
- Skin lined diverticulum within nasoincisive notch
21
Q
Identify the features of external nares of carnivoridae and explain their role in airway resistance.
A
- Nasal plate (divided by median groove, philtrum secretions from lateral nasal gland)
- dry nose suggest illness as are not displaying normal behaviour
22
Q
Identify the features of external nares of suidae and explain their role in airways resistance.
A
- small nostrils on snout
- Highly sensitive
- Contaisn rostrale (use nose to dig so need hard surface)
23
Q
Identify the features of external nares of aves and explain their role in airway resistance.
A
- Slit like openings (not in diving birds)
- Operculum (overhanging bony flap)
- Wide communication between nasal cavity and pharynx - choana
24
Q
Describe and overview of the structures of nasal cavities and the division created by the turbinates.
A
- Nasal cavity extends from nostril to cribriform plate of ethmoid bone
- Divided by nasal septum
- further divided into nasal meatuses by nasal concae (increase nasal surface area and are highly vacularised)
- Turbinates form the nasal concahe
- 1st endodermal turbinate = dorsal concha
- 2nd endodermal turbinate = middle concha
- Maxillary turbinate = ventral concha
25
Define the term concha.
Concha are turbinates covered by nasal mucosa
26
Define the term turbinates.
Turbinates are delicate scrolls of bone. There are 3 groups -maxillary, endodermal and ethmoidal
27
Define the term meatus.
Meatus simply means hole. There are many meatuses in the body.
28
Define the role of the nostrils.
They warm and humidify the air during inspiration and capture particles and pathogens
29
Define the role of conchae in the head.
- Defence mechanism (as they capture pathogens and small particles)
- Warm and moisten the air
30
Define the role of turbinates in the head
- Generate turbulence as air passes through the head
- Maximise capture of particles on epithelium
- Caudal regions are covered by olfactory epithelium
31
Define the role of the nasal meatus in the head
- Pathway for air to flow through
32
Explain the of airflow along the nasal chambers.
- Resistance to airflow is present (nasal cavity, pharynx and larynx make up 60% of resistance)
- Resistance = length/radius^4
- Drawn into nostrils/mouth
- through nasal cavities to pharynx
- Through larynx and into trachea (sits ventral to oesophagus)
- Horses obligate nose breathers
33
Describe the histological appearance of structures of the nasal cavity
- Respiratory epithelium is pseudostratified
- Covers most parts of nasal cavity
- Mucosa = eptihelium + lamina propria
- olfactory epithelium is pseudostratified, ciliated and has olfactory cells
34
Explain the structure of the paranasal sinus, their drainage and interconnections in the horse and dog.
- Frontal and maxillary sinuses present in all species
- Frontal sinus is between nasal and cranial cavities, drain into ethmoidal meatus (different in horse). 3 compartments in dogs, may include zygomatic process. In the horse is continuous with part of dorsal concha (frontoconchal sinus and drains into maxillary sinus through frontomaxillary opening)
- Maxillary sinus is in caudolateral aspect of upper jaw around cheek teeth, drains into middle meatus. Largest sinus in horses, divided into rostral and caudal sinus by oblique bony septum. Drain through nasomaxillary opening dorsally.
- Rostal maxillary sinus is in horses only, divided into lateral and medial compartment. Medial compartment enclosed by ventral concha and infraorbital canal
- Frontal sinus (frontoconchal) -> frontomaxillary opening ->caudal max. sinus -> nasomaxillary opening -> middle meatus
- Sphenopalatine sinus -> caudal max. sinus -> nasomaxillary opening -> middle meatus
- Rostral max sinus -> nasomaxillary opening -> middle meatus
35
List the differences in anatomy of the sinuses in cattle, dogs and pigs.
Frontal sinus of cattle: 5 compartments, one larger caudal compartment leads to the cornual process and pneumatises the horn
Frontal sinus of dogs: 3 compartments, lateral compartment is the largest, may include zygomatic process
Frontal sinus of pigs: very extensive cavity
36
Describe the relationship between the paranasal sinuses and the nasolacrimal duct.
- Nasolacrimal duct drains from medial canthus of the eye to the nasal cavity
- Ends at nasal punctae
- Runs with maxilla and maxillary sinus
- In horses ends at the nares, and in dogs ends within nasal cavity
37
Describe the relationship between the paranasal sinuses and horns.
- Horns are continuous with sinuses, made of bone
- Frontal sinus communicates with horn (caudal in cattle)
- Most nerves arise from trigeminal nerve and all innervated by cornual nerve
38
Describe the vascular supply to the horns of cows and goats.
- Branch of macillary artery (superficial temporal artery and cornual artery)
- Very vascular
39
Describe the neural supply to the horns of cows and goats.
- Most nerves from trigeminal nerve
- All species innervated by cornual nerve
- 90% of animals from cornual branch of infratrochlear nerve
- 15% also have frontal nerve and 5% have frontal sinus nerve
- Cutaneous branches from 1st and 2nd vertebrae caudally
40
Describe the limits of the oropharynx.
- ventral to soft palate
- Extends from oral cavity (last molar) to epiglottis
- Bordered by tongue, palate and palatoglossal arches
- Lined with stratified squamous epithelium
41
Describe the limits of the nasopharynx.
- Dorsal to soft palate
- Extends from choanae to intrapharyngeal opening
- Bordered by base of skull, soft palate and cranial cervial vertebrae
- Lined with respiratory epithelium
42
Describe the limits of the laryngopharynx.
- The intrapharyngeal opening to opening of the oesophagus and larynx
- Includes epiglottis
- Opening is formed from free edge of soft palate and palatopharyngeal arches
- Common pharynx is between the soft palate and epiglottis
43
Describe the structure of the soft palate.
- Divides the pharynx
- Covered by respiratory epithelium and squamous epithelium
- Palatinous muscle shortens the palate
- Soft palate divides food and air
- Allows eating and breathing to occur simultaneously (suckling)
- controlled by 2 muscles
- Tensor veli palatine causes lateral traction and tension (innervated by mandibular branch of the mandibular branch of the trigeminal nerve)
- Levator veli palatine which raises soft palate, allows swallowing and mouth breathing to occur
44
Describe the muscular control of pharyngeal function.
- Controlled by striated muscles
- Constriction and shorterning controlled by rostral, middle and caudal muscles
- All insert on roof of pharynx (dorsal and lateral arches)
- Dilation is controlled by only the stylopharyngeus caudalis
45
Describe the neuronal control of pharyngeal function.
Innervated by the vagus and hypoglossal nerves
46
describe the muscular control of palatine function.
- Palatinus muscle shortens the palate
- Tensor veli palatine causes lateral traction and tension
- Levator veli palatine raises the soft palate (swallowing and breathing) and constricts palatopharyngeal arch
47
Describe the neuronal control of palatine function.
- Tensor veli palatine innervated by mandibular branch of the trigeminal nerve
48
Outline the changes in the pharynx during inhalation and deglutition.
- Soft palate elevated
- Palatopharyneal arch constricts (levator veli palatine)
- Hyoid apparatus pullls the larynx forward and the epiglottis is pulled back
- Protects larynx
49
Identify the cutaneous landmarks of the guttural pouch.
- Sits in Viborg's triangle
- Only useful if distended
- Borders of triangle are caudal border of the mandible, the tendon of sternocephalicus and linguofacial vein
50
Describe the relevance of structure passing through and over the guttural pouch.
- Lymph nodes important for drainage
- If burst are likely to burst into pouch
- Causes persistent infection in pouch
- Fungal and bacterial disease can occur in pouch
- Close to lymph nodes so infection can spread easily
51
Discuss the microbial definition of a pathogen.
- Must be found in all animals suffering from disease, not in healthy animals
- Must be able to be grown in pure culture and cause disease when introduced into a healthy animal
- Must be able to be re-isolated from the experimentally infected animals
52
Rationally define the microbial disease process.
- Infection, produce toxins and poison host
- Cause a reaction
- Can be a combination of both
- Can also be endogenous or exogenous (transferred vertically, horizontally, sexually, sharps, blood transfusions etc.)
- Is a balance between health and disease
53
Define commensal.
A pathogen that exists on teh host without causing disease
| Often only exists as a commensal in one area, will cause disease when in another
54
Define an opportunistic pathogens.
An organism that causes infection when given the chance (e.g. commensals in wrong location)
55
Define a pathogen
An organism that causes disease
56
Describe the separation of microoganisms between fungi, bacteria, viruses, TSEs (prions)
Fungi: hyphal form, chitin cell wall, largest, eukaryotic, 2 forms (yeasts and moulds), some dimorphic, a few cause disease
Bacteria: next in size, many variatons, cellular structure, prokaryote, few cuase disease
Viruses: smaller than bacteria, no celluar strucure, can only be cultivated within living organisms, most cause disease
Prions: single proteins with sugar decorations, smallest, non-living pathogen, no cellular structure, only cultivated within living organism, all cause disease, no cure
57
Discuss the general features of fungi.
- Grow anaerobically at 25degrees
- Tolerate high osmolarity and low pH
- Secrete potent enzymes
- Some are pathogenic (mostly saphrophytes)
- Opportunistic, some produce mycotoxins
- Dematophytes cause ringworm
- Hyphal form
- Some are dimorphic (will grow as yeast or mould depending on temperatures)
- Non-photosyntehtic
- Cell wall contains chitin and other polysaccharides
- heterotropic nutrition
- Can reproduce sexually and asexually
58
Describe how to differentiate between fungi.
Colonial characteristics:
- Moulds and characteristics
- size/appearance after set time
- colour both sides
- surface elevation/depression or other patterns
Examination of spore structure (moulds only):
- From culture
- Clinical ssample
Features of vegetative hyphae (moulds only):
- presence/absence of septa
- Hyaline (colourless) or dematiceous (pigmented)
- Hyphal structures (spiral, racket shape etc)
59
Describe the methods used to identify fungi.
Biopsy and histopathology- identification of tissue invading fungi
Microscopy - infeced tissue mounted on KOH on slide and examined under microscope, chitin cell wall is resistant to KOH, cells are not, flourescent microscopy may be used for identification even on non-viable cultures or on fixed tissue sections (common HE tissue stain does not always stain organism)
Serology - may be helpful but similar problems to any serology
60
Describe the yeast formation of spores and germination.
- May or may not form spores
- Spores are more like gametes
- Yeast is diploid and can reproduce asexually by budding
- If stressed (e.g. runs out of food) then can exist as haploid and will sporulate
- Haploid spores are formed in an ascus
- 2 'a' spores and 2 alpha spores (defined by pheromone secreted)
- Attract spores of oposite mating types
- Haploid spores can reproduce via budding as well
- Can also shmoos to form a diploid and start diploid process again
61
Name the 3 methds of hyphal fungi spore formation.
- Fragmentation of the mycelium (hyphae) into small pieces (arthrospores)
- Formation of conidia spores
- Formation of sporangiospores
62
Name the different types of conidial spores.
- Conidia spores covers blastoconidia, macroconidia, microconidia, blastospores
63
Describe the formation of sporangiospores.
- Cleavage of cytoplasm around individual nuclei in a multinucleate sporangium
- Sporangium is a specialised structure formed on vegetative colony
- Shape and form can be seen under a microscope and can help cornfirm fungal infection
- Method used depends on phylum
64
Describe how bacterial biochemsitry can differ.
- Differences between genera
| - Break down different sugars, secrete different enzymes, require different nutrients etc.
65
Explain how differing bacterial biochemistry can be used for selective culture.
- Differnt bacteria do different things
- Can make selective culutres
- Assess survival on a variety of cultures and collate information to identify one species
- Can not differentiate between strains of a species
- Catalase,oxidase, urease, coagulase, oxidation-fermentation tests
66
Explain how susceptibility to antimicrobial compounds can be used for selective media.
- Selective antibiotics can allow certain strains of bacteria to grow while inhibiting others
- The desired bacterium must be the only resistant strain in order to get an effective result
- Can be used in combination with other factors such as bile salts or deoxychlorate
- Allows only one strain to grow even if more than one strain are resistant to the antimicrobial
67
Explain how haemolysis assays work.
- Are a type enriched medium (with blood)
- The ability of some to lyse the blood cells in order to acquire iron can be used to identify the bacteria
- This leads to different colours on the plate
68
Describe how to interpret bacterial strains on a haemolysis assay.
- 3 different types of bacteria
- Alpha - not able to lyse the blood and so produce and incomplete green zone
- Beta - able to completely lyse the blood cells to produce a clear zone
- Gamma - unable to lyse the blood cells so there is an absence of haemolysis
69
Outline the key points about selective media.
- Have an agent that allows one bacterial strain to grow and not others
- Add something bacteria are intrinsically resistant to or sensitive to
- E.g. bile salts, deoxychlorate, selective antibiotics
70
Outline the key points about indicator media.
- Addtion of substrates that one group of bacteria can use but not others
- Use substrates that lead to pH change and add pH indicator to media
- Add colour e.g. homologous substrate
- When metabolised leads to a change in colour
- Substrate must be take up by 1 strain
- Often combined with sleective media
- End up with small group when ony one strain is coloured
71
Outline the key points about MacConkey media.
- Selective + indicator
- Base media: peptone (peptides), NaCl (optimum osmolarity), agar
- Inhibitor = bile salts (inhibits many non-enteric bacteria)
- Inhibitor component: lactose (fermented by some), neutral red pH (reacts when lactose fermented)
- Non-lactose fermenting use peptone, raise pH = white/colourless colonies
- Some modifications add crystal violet dye, reduces some unwanted gram -ve bacteria
72
Outline the key points about XLD media
- Yeast, NaCL, agar
- Inhibitor: sodium deoxychlorate
- Indicator component: phenol red (pH indicator), xylose/lactose/sucrose, lysine (target for decarboxylase producing bacteria), sodium thiosulphate and ferric ammonium sulphate (reacts with thiosulphate reduction products)
- Selective and differential medium for recovery of Enterobacteriaceae
- Low in nutrients
- Indicator for pHand hydrogen sulphide production leads to black colony centre for some colonies
73
Outline the key points about blood agar.
- Haemolysis test
- Not all bacteria able to lyse blood
- Colour of colony shows degree of haemolysis
74
Outline the key points about CAMP tests.
- test strain produces enhancer
- Acts with beta-haemolysin produced by S. aureus to increased effect
- distinguished S. agalactiae from other species of Streptococcus
- Positive results can also be obtained for discrimination of Rhodococcus equi, Actinobacillus pleuropneumoniae, Listeria monocyogenes
75
Discuss the sterilisatino of media and other substances.
- Flamed
- Most can be autoclaved (some compounds may react when autoclaved together)
- If cannot be autoclaved, components filtered and mixed or lightly heated to 100degrees or above
- Will not get rid of prions
76
What methods can be used to identify bacteria.
- Using known information and comparing with media
- Biochemical tests
- Appearance under a microscope
- API strips
- Also based on clinical signs and symptoms presented with
77
Name the common biochemical tests and state why they are useful
- Useful for supporting diagnoses
- Catalase test
- Oxidase test
- Fermentation assays
- Specific media tests
78
Outline the catalase test.
- Detects catalase enzymes
- Enzyme catalyses breakdown of H2O2 to water and oxygen
- H2O2 can damage cell components so ability to remove it rapidly is important in many aerobic organisms
79
Outline the oxidase test.
- Measure the ability of an organism to clot rabbit plasma
- Positive ability to cause coagulation in serum
- 2 variations: slide test (clumping) or tube test (clotted plasma)
80
Outline fermentation assays.
- Enzymes asses
- Either assay product or ability to break down something in media
- Indole prodution or urease test
81
Outline specific media tests.
- Pitting of Loeffler's serum slope (proteolysis)
- haemagglutination
- Nagler test (biochemical test that used to identify organisms that liberate phospholipases/lecithinases)
82
Explain teh basis for labroatory diagnosis.
Identify bacteria in order to prescribe specific antibacterial, in order to reduce the risk of antibiotic resistance
83
Describe phage typing to differentiate bacteria.
- Uses lytic bacteria
- Pattern of susceptibilty of bacterial isolate establishes phage type
- Most commonly used on Staph. aureus, Salmonella typhimurium and S. enteritis
- Strain specific binding and killing using plaques with specific viruses
- Phage attach to surface structures which can vary subtly between different isolates of same species
- May be absent or present
- Multiple pahge assessed for ability to infect bacteria
84
Describe serotyping to differentiate bacteria.
- Antibodies attach to surface structures e.g. O-antigen (lipopolysaccharide of gram -ve bacteria)
- Very specific interaction so subtle changes can lead to change in binding
- Some O-antigen core structures considered and can be used to identify genera/species of related gram -ve bacteria
- define lineages within the same species
- other targets useful for other groups of bacteria
- Can be simple agglutination tests, ELISA and can be used with immune-histology
85
Explain the difference between serology and serotyping.
Serotyping is the defining of closely related bacteria using antibodies which bind to known agents of those bacteria.
Serology is using sera from the patient in assays with a known antigen to show that the antibody has been generated in the patient against that pathogen
86
List the methods that can be used to identify and differentiate bateria.
Serotyping, phage typing, molecular typing (RFLP, restriction typing, multilocus sequence typing)
87
List common molecular methods used to differentiat bacteria in epidemiology and explain why these can be used.
rNA molecular diagnostics, multilocus sequence typing, presence of specific genes, hybridisation based methods, DNA probes
Mutations accumulated during replication of DNA can be used to separate closely relaed bacteria. Genes may be lsot or gained and directly relate to properties of bacteria.
88
Describe how rNA molecular diagnostics work.
- Ribosomes - variable + conserved regions
- Within genera different regions conserved
- Sequencing of these regions can be determined and aligned to consensus
- Able to place isolates into a known group
89
Describe how multilocus sequence typing works.
- housekeeping genes in each sequence (needed so cannot change or be lost)
- using DNA sequences able of multiple housekeeping genes able to characterise isolates
- for each gene, different sequence aligned with others in species
- matching of alleles at loci defines allelic profile or Sequence Type (ST)
- MLST works well to distinguish bacteria in same species
90
Describe how testing the presence of specific genes works.
- Genes specific to that pathogen present
- Can be detected with PCR
- Ampplify DNA using DNA primers specific to gene
- Can show if pathogen present to species level only
- Can be used with MLS to separate groups
91
Describe how hybridisation based methods of typing work.
- DNA double stranded
- DNA target fixed on solid support
- Labelled test DNA washed over fixed samples
- Look for binding
- PCR quicker and easier if detecting unique gene sequence
- Good for screening for a lot of genes
92
Describe how DNA probes can be used to differentiate bacteria.
- Splice target base sequence
- Attach marker
- Add to single stranded DNA
- Allow to bind
- When bound will be able to see marker
93
What type of microorganism is foun din the normal respiratory tract of veterinary species and what are of the respiratory tract will these be found on.
- Upper respiratory mucosal surface
- Only bacteria can be commensals here
- Viruses and fungi will always cause disease
94
Explain how some respiratory organisms act as commensals and others are pathogenic.
- Some commensals are latent and cause infectino if conditions change in its favour e.g. Equine Herpes virus (not a commensal but will only cause disease if favourable conditions)
- Phase variationin bacteria can also do this e.g. Pasteurella haemolytica in cattle
- Some are specific to body system e.g. E. coli is commensal of GI but pathogen of respiratory
- Some may be opportunistic - commensal when no other infection but can produce secondary infection
95
Explain the clinical significance of commensal organisms in the diagnosis of respiratory disease.
- Commensals will be seen if swab done
- Important to not mistake for primary infection but not discount as secondary infection
- Commensal for one body system may be virulent pathogen for another
96
Describe the anatomy and innervation of the external intercostal muscles.
- Externals superficial, fibres caudoventrally between ribs
- Not between costal cartilages
- Inspiratory action
- Supplied by intercostal nerves (ventral rami of thoracic spinal nerves)
97
Describe the anatomy and innervation of the internal intercostal muscles.
- Run craniodorsally
- Have 2 compartments: interosseus (expiratory) and interchondral (inspiratory)
- Supplied by intercostal nerves (ventrla rami of thoracic spinal nerves)
98
Describe the anatomy of the ribs.
- Dorsal bony part, cartilaginous ventral part articulating at costochoondral junction
- Heads with 2 articular facets (articulation with vertebrae)
- Tubercles with facet for articualtion with transverse processes of more caudal vertebrae
- True ribs articuate directly with sternum, false ribs indirectly via cartilage connection with that in front
- Last rib may not connect to neighbour
99
Describe the anatomy of the thoracic wall.
Walls formed by thoacic vertebrae dorsally, ribs and costal cartialges laterally
100
What is the order of the intercostal vessels and nerves going caudally.
Vein
Artery
Nerve
(VAN)
