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VetMed Year 1 > CRS 3 > Flashcards

CRS 3 Flashcards

1
Q

Describe the clinical signs of lower airway disease

A
  • Coughing
  • Tachypnoea
  • Increased depth of breathing
  • Listlessness
  • Dyspnoea
  • Secretions
  • Crackling or wheezing on auscultation
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2
Q

List the diagnostic tools which may be of use in investigating lower respiratory disease

A
  • Ultrasonography
  • Radiography
  • MRI and CT
  • Swabs
  • Endotracheal wash
  • Biopsy
  • Fine needle aspirate
  • Bronchoalveolar lavage
  • Top 3: radiograph, guarded swab, endotracheal wash
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3
Q

Describe how you would carry out a radiograph of the lower respiratory system of a dog or cat

A
  • Left and right lateral
  • Dorsoventral
  • Label, contast, Kv and Mv
  • Hold lungs at full inflation
  • Consider safety of person inflating lungs
  • Must include cranial part of diaphragm
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4
Q

Describe the effects of bronchoconstriction on ventilation/lung parameters including compliance, resistance, tidal volume, work of breathing, gas exchange and arterial oxygenation

A
  • Less air reaching alveoli
  • Compliance reduced
  • Resistance increased
  • Tidal volume decreased
  • Work of breathing increased
  • Gas exchange decreased
  • Arterial oxygenation may be lowered in an attack
  • Closing capacity becomes an active process in an asthma attack
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5
Q

List the effects of restrictive bronchial disease which may increase the risk of general anaesthesia

A
  • Rate of oxygen uptake is reduced
  • Reduction of tidal volume and lumen of small airways
  • Great risk of asphyxiation
  • Reduction in gas exchange rate
  • Greater risk of oxygen starvation
  • Severe reduced arterial oxygen
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6
Q

Explain the effects of recumbency on respiratory function

A
  • In VD, lungs pushed against dorsal side of animal
  • Reduces capacity to inflate
  • Problematic if at risk or already in respiratory distress
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7
Q

Describe the effects of anaesthetic agents on respiratory function

A
  • Airway obstruction (relaxation of muscles)
  • Reduced ventilation (due to reduced tidal volume or rate of respiration)
  • Decreased functional residual capacity (relaxation of diaphragm and intercostal muscles)
  • Increased V/Q mismatch and shunting
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8
Q

State the methods by which anaesthetic risks to threspiratory function can be minimised before and during eh procedure

A
  • Pre-oxygenating to maximise FRC
  • Antimuscarinic drugs before to reduce saliva production
  • Mechanical ventilation
  • Not using 100% oxygen
  • Maintaining perfusion pressure by giving fluids
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9
Q

Describe the relevance of circuit factors for calculating fresh gas requirements under anaesthesia

A

Needed to calculate flow rate for gas, to ensure patient is not breathing in the CO2 it has exhaled

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10
Q

Describe possible radiographic changes associated with feline asthma including air trapping, bronchial pattern and consolidation

A
  • Bronchial thickening - doughnuts on DV view
  • Consolidation and air trapping also common
  • See as flattened diaphragm, increased distance between cardiac silhouette and diaphragm
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11
Q

Outline the pharmacologial therapeutic options for the management of inflammatory restrictive airway disease and how each works

A
  • 2 classes
  • Steroids and bronchodilators
  • Can be used in feline inhaler
  • Steroids: anti-inflammatory, reduce mucus production (prednisolone, dexamethosone and fluticasone)
  • Bronchodilators: stabilise mast cell membrane, inhibit ACh release, promote mucus clearing (albuterol)
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12
Q

Outline non-pharmacological therapeutic options for the management of inflammatory restictive airway disease

A
  • Control weight

- Limit use of pollutants

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13
Q

Explain how the structure of the thorax facilitates breathing

A
  • Air flows from high to low pressure
  • Thorax must have lower pressure than atmospheric to have air flow in
  • Increas lung volum by thoracic expansion
  • Inspiratory muscles
  • Diaphragm contracts - flattens and moves caudally
  • External intercostals contract, ribs cranially and outwards
  • Increases volume of thoracic cavity
  • In expiration, inspiratory muscles relax, dome of diaphragm pushed back by inspiratory pressure, ribs recoil
  • Pleural membranes attach lungs to thoracic wall
  • When thorax expands, pleural membranes expand, lungs expand
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14
Q

Explain how the calibre of the airways affects air flow

A
  • 2 factors to increase resistance to flow in airways: calibre of airways and turbulence
  • Calibre decreases as go down, maintains resistance to flow at a constant level
  • Combined cross sectional area of 2 daughter airways always exceeds that of parent airways
  • Air flow remains constant
  • Laminar or turbulent air flow
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15
Q

Explain how laminar and turbulent air flow occur

A
  • Laminar: resistance is directly proportional to length of tube and inversely proportional to internal radius of tube
  • Increased resistance means pressure must be increased to maintain flow
  • Turbulence can also occur
  • Is greatest in trache and bronchi
  • Increasing branching along airway increases overall diameter and therefore turbulence decreases
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16
Q

Define anatomical dead space

A

An airway in which no appreciable gas exchange can occur

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17
Q

Describe how smooth muscle in airways regulates dead space and resistance to flow

A
  • Bronchial muscle consists of spiral bands of smooth muscle
  • Criss cross left and right around bronchi and bronchioles
  • Particularly well developed in wall of bronchioles
  • Sympathetic system relaxes smooth muscle and spiral design allows reduction of airway length and diameter
  • Enables normal lung to balance dead space against resistance to air flow
  • Internal radius of conducting airways must not be too small
  • Increases resistance to air flow and turbulence
  • Volume of CAs must not be too great
  • Would enlarge anatomical dead space and lead to unecessary energy expenditure
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18
Q

Explain the role of the pleura in ventilation of the lungs

A
  • Pleura connects lungs to thoracic wall
  • When thorax expands so do pleura and lungs
  • Draws in air
  • When thorax collapses, so do pleura and lungs pushing air out
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19
Q

Outline the importance of complaince and surface tension in lung function

A
  • Compliance = change in volume of a structure for each unit change in pressure
  • Elastance is retractive force that distension of structure generates
  • All tubes within lung are subject to transverse and longitudinal traction
  • Increases volume of airways
  • Compliance must be great enough to allow maximum passage of air
  • Surface tension increases in smaller spheres
  • Reduced by production of surfactant
  • More surfactant in smaller alveoli so pressure is same between smaller and larger alveoli
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20
Q

Describe the structural defence mechanisms of the pulmonary system

A
  • Branching airways: turbulence, irritant receptors, cough reflex initiated
  • Bronchi surrounded by cartilaginous rings and smooth muscle: bronchi constrict, held open a little
  • Intimate relationship between blood and airways: rapid resopnse to particle deposition, lymphocytes adjacent to site of deposition
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21
Q

Describe the functional defence mechanisms of the pulmonary system

A
  • Mucociliary escalator
  • Secreteory fluid: mucin and surfactant ensure lungs stay inflated, mucociliary escalator
  • Cough reflex: expel particles
  • Bronchoconstriction and dilation: entrance of particles, more open in exercise
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22
Q

Describe the cellular components of host defencesystem in teh lungs

A
  • Intraepithelial lymphocytes: adjacent to site of particle deposition, fast response
  • MALT/BALT: located in areas where fast drainage is importat
  • Drainage lymph nodes: 4 lymphoid centres, important sites of drainage
  • Bronchoalveolar lymphocytes: destroy pathogens on site, prevent infection
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23
Q

Describe how inflammatory mediators interact with mechanisms of bronchiolar spasm

A
  • Inappropriate release of inflammatory mediators causes bronchiolar spasm
  • Inflammaory mediators: histamine, prostaglandins, leukotrienes, bradykinins, cytokines
  • Simulate CNS to react and cause bronchiolar spasm
  • CNS excites vagus
  • Innervated from trachea to bronchioles
  • NTs released
  • Excite SMCs
  • Excitation results in bronchoconstriction
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24
Q

Describe the broad mechanisms of action by potential therapeutic targets to resolve bronchospasm

A
  • Intervene in efferent response with drugs
  • Binding of catecholamines to beta adrenergic receptors on smooth muscle cells = bronchodilation
  • Clenbuterol: agonistic for beta adrenergic receptors
  • INhibit Ach receptors
  • Anti-inflammatory drugs
  • Cholinergic to stimulate mucus and ciliary motility
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25
Q

Describe the suspencion of the larynx and articualtion with hyoid apparatus

A
  • Larynx suspended by hyoid bones
  • Articulate with base of skull - temporal bone
  • Lies below pharynx behind mouth
  • Suspended from cranial base
  • Thyrohyoid bone (hyoid apparatus) and thyroid cartilage (larynx) articulate to hold up larynx
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26
Q

Explain the innervation and function of the larynx and its effects on conduction of air to lungs and deglutition

A
  • 2 nerves either side
  • Cranial laryngeal nerve = sensory of laryngeal mucus membrane, motor innervation of cricothyroideus
  • Caudal laryngeal = innervates all laryngeal muscles except cricothyroideus
  • Larynx is connection of nasal part of pharynx and trachea
  • Involved in breathing, protection of lower airways, swallowing and phonation
  • Protected by epiglottis
  • Inhibited respiration during swallowing
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27
Q

Name the 4 cartilage structures of the larynx

A
  • Epiglottic
  • Arytenoid
  • Thyroid
  • Cricoid
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28
Q

Describe the thyroid cartilage of the larynx

A
  • Largest
  • 2 lateral plates that fuse ventrally to varying degrees
  • Most rostral part is thickened = Adam’s apple
  • Rostral and caudal extremities of dorsal edge of each lamina articualte with thyrohyoid and arch of cricoid respectively
  • Cartilage is hyaline
  • Susceptible to aging
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29
Q

Describe the cricoid cartilage

A
  • Expanded dorsal lamina
  • Narrow ventral arch
  • Signet ring
  • Dorsal carries median crest and on rostral rim 2 facts on each side for arytenoid cartilages
  • Arch carries facet on each side for articulation with thyroid cartilage
  • Hyaline
  • Subject to aging
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30
Q

Describe the arytenoid cartilages

A
  • Irregular shape
  • Caudal facet articulates with rostral margin of cricoid lamina
  • From this radiate vocal process ventrally into laryngeal lumen to which vocal fold attaches, muscular process that extends laterally, corniculate process that extends dorsomedially
  • Forms caudal margin of laryngeal entrace
  • Mostly hyaline
  • Corniculate is elastic
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31
Q

Describe the epiglottic cartilage

A
  • Most rostral
  • Stalk and leaf
  • Stalk embedded between root of tonge, basihyoid and body of thyroid cartialge
  • Attached to all
  • Can be tilted backward to partially cover entrance to larynx when animal swallows
  • Elastic cartilages
  • Flexible
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32
Q

Describe the cartilaginous structures of the larynx and their articulation in birds

A
  • Only cricoid and arytenoid
  • No vocal folds = no creation of sound
  • Sound created in syrinx
  • Glottis can be closed to prevent food particles entering larynx or trachea
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33
Q

Explain how ventilation is regulated

A
  • Distribution regulated by pleural pressure gradient
  • Lower portions ventilated more than upper
  • Lung easier to inflate at lower volumes
  • Apex has large expanding pressure
  • Big resting volume
  • Small change in volume on inspiration
  • Regional differences in ventilation are equal to change in volume per unit resting volume
  • Also applies to lower most section of lung
  • High CO2 concentration detected incrased respiration rate and volume to increase gas exchange and remove waste from body
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34
Q

Outline the mechanisms that limit ventilation regionally

A
  • Resistance to flow in airways
  • Lung compliance
  • Alveolar tension
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35
Q

Explain how perfusion of the lung is affected by posture.

A
  • Half volume of lung is dorsal to pulmonary trunk
  • Pulmonary systolic arterial pressure is only 20-40mmHg
  • Dorsal parts less well perfused and reduction in ventilation of dorsal parts
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36
Q

Explain how perfusion if affected by cardiac function

A
  • If obstruction of blood vessel then that area will not be perfused
  • Less blood returing to heart but blood returning is normal
  • Muscle mass of heart is smaller on RHS - if cardiac pressure falls may not be able to perfuse lungs properly
  • Gaseous exchange will not be able to take place
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37
Q

Explain how perfusion of the lung is affected by lung disease

A
  • Alveoli not function due to infection or mucus blocking alveolis
  • No ventilation in that area
  • Gas exchange cannot take place
  • Drop in blood oxygen concentration
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38
Q

Describe the effects of ventilation perfusion mismatching in animals

A

Impairs gas exchange and can lead to hypoxia, hypercapnia and costs energy

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39
Q

How is tidal volume calculated?

A

Volume of air fowing through airways each inspiration and expiration

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40
Q

How is minute volume calculated?

A

Volume of air inhaled or exhaled in one minute. Tidal volume x breathing rate

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41
Q

Describe the passage of carbon dioxide from the atmosphere to the tissues

A
  • CO2 enters RBCs
  • Reacts with water to form carbonic acid
  • Carbonic acid dissociates to bicarbonate ions and hydrogen ions
  • Diffuse into plasma
  • H+ buffered by Hb (HHb)
  • carbon dioxide carried to lungs in plasam as bicarbonate ions
  • Diffuse into lungs as CO2 again
  • Ventilation stimulated by drop in blood pH, due to high blood concentration of H+ and HCO3- ions
42
Q

Define the driving forces for oxygen and carbon dioxide transport

A
  • O2 tension in pulmonary capillaries (normally = PAO2)
  • Haldene effect: deoxygenation of blood increases ability of Hb to carry CO2. More effective buffer of H+ than HbO, has protective effect
  • Affinity for Hb is inversely related to the P50
43
Q

Explain the principles of diffusion and the factors affecting pulmonary perfusion of respiratory gases

A
  • For oxygen to pass through respiratory membrane must first dissolve then diffuse in to plasma
  • Oxygen then diffuses into the RBCs and combines reversibly with iron atoms of Hb
  • Deoxyhaemoglobin +O2 = oxyhaemoglobin
  • PAO2 in pulmonary capillary is higher than PO2 in pulmonary artery
  • Therefore oxygen will diffuse into pulmonary blood
  • Dissolves in plasma and binds to Hb
44
Q

What is Fick’s Law of Diffusion?

A

Rate of transfer of a gas through a tissue sheet is directly proportional to tissue area and difference in partial pressure between the 2 sides

45
Q

List the changes in oxygen in carbon dioxide composition between inspired and expired gas and arterial and mixed venous blood

A
  • PO2 decreases through system, PCO2 increases
  • Inspired gas has more oxygen and less CO2 than expired gas
  • pO2 = barometric pressure x fraction of oxygen present
46
Q

List the factors governing diffusion at tissues

A
  • Partial pressure of oxygen
  • Partial pressure of carbon dioxide
  • Ventilation/perfusion ration
  • Carboxyhaemoglobin (carbon monoxide has a higher affinity and binds irreversibly to Hb, removes proportion of Hb)
47
Q

Distinguish between hypo- and hyperventilation and describe the effects of these on blood acid-base balance

A
  • Hypo: reduced ventilation, increases blood CO2 as is triggere by reduced CO2 in CSF
  • Hyper: increased ventilation, decreases blood CO2, triggered by increase in CO2 in CSF
  • Ensures blood acid-base balance changes around set point between set limits
48
Q

Describe how blood acid-base balance affects the ventilation rate

A
  • Central chemoreceptors in ventral surface of medulla
  • Sensitive to H+ ion concetration in CSF
  • Indirect as charged ions to not cross BBB
  • CO2 highly soluble and does cross barrier
  • Hydrated to carbonic acid -> H+ and HCO3-
  • Increase in CO2 in CSF causes chemoreceptors to stimulate respiration while fall in CO2 would inhibit respiration
49
Q

Describe the mechanism of bronchodilation

A
  • Sympathetic stimulation
  • Beta2 adrenoceptors stimulated by agonist
  • NE causes dilation by increasing cAMP
50
Q

Describe the mechanisms of bronchoconstriction

A
  • Parasympathetic stimulation
  • Muscarinic receptors stimulated (M1 and M3)
  • Stimulation of M3 receptors decrease cAMP
  • Increased mucus secretion and causes contraction of bronchial smooth muscle
  • Stimulation of M1 increases mucus secretion
51
Q

Explain how the function of the normal lung can be altered by inappropriate release of NTs or inflammatory mediators

A
  • Inappropraite release of NTs: muscarinic mediated bronchospasm, feline asthma, equine recurrent airway obstruction
  • Overstimulation of PSNS: excessive bronchoconstriction
  • Inflammatory mediators: excessive mucus, oedmea and fibrosis, increase resistance, narrow airways
  • All reduce respiratory function
52
Q

Describe the neurological control of lungs and ventilation

A
  • Medulla oblongata
  • Due to CO2/H+ concentration
  • Regular intervals action potentials in inspiratory neurons of MO
  • Excitatory synapses with motor neurons innervating inspiratory muscle = contraction
  • Forced inspiration
  • Expiratory neurons stimulate motor neurons to expiratory muscles
  • Rhythm influenced by central pattern generator
  • Stretch sensitive sensory cells located on surface of bronchial smooth muscle respond to increase with transpulmonary pressure
  • When activated by stretch, inhibit impulse generation
53
Q

What are the non-respiratory function of the lungs?

A
  • Vascular reservoir
  • Recruitment and distension
  • Postural and ventilator cahnges
  • Filter for blood born substances
  • Physical filtration
54
Q

Describe the lungs as a vascular reservoir

A

Blood not used for gas exchange is held within pulmonary vasculature

55
Q

Describe the lungs’ funtion in recruitment and distension

A
  • Able to alter lung blood volume to accomodate ncreased blood flow due to posture, exerciser and increased intravascular volume
56
Q

Explain how the lungs can act as filters for blood borne substances

A
  • Ideally positioned
  • particulate matter such as clots, fibrin clumps and other endogenous and exogenous material from systemic circulation
  • Prevents ischaemia and infarction
57
Q

Explain how the lungs can carry out physical filtration

A
  • Act as physical barrier to blood borne substances
  • Not completely efficient in protecting systemic circulation
  • Pulmonary microcirculation designed to maintain alveolar perfusion
  • Prevents exo and endogenous emboli accessing systemic circualtion
58
Q

Describe respiratory clearance and identify cell types responsible for this function

A
  • Mucociliary escalator
  • Reflex responses
  • Head position important in respiratory clearance
  • Goblet cells and ciliated epithelial cells
  • Tiny particles breathed out
  • Sensory cells detect particles and stimulate coughing and sneezing
59
Q

Describe the air flow through the upper respiratory system, the lungs and the air sacs or the avain lung

A
  • Air inhaled through nose
  • Passes through larynx into trachea
  • Past syrinx
  • Into lungs and air sacs
  • Half passes into caudal air sacs, half into lungs for gas exchange
  • Air in cranial air sac expired, lung air into cranial air sac, caudal air into lungs
  • Ensures there is alwyas fresh air on gas exchange surfaces
60
Q

Describe the structure of the avian lung

A
  • Stiff and non-complaint
  • Unidirectional flow of air
  • 8 or 9 air sacs
  • Highly vascularised
  • Lung branches into primary bronchus (runs through lung), 4 sets of secondary bronchi and parabronchi
  • Are for gas exchange
  • Paleopulmonic bronchi make up most of parabronchi, parallel tubes
  • Neopulmonic bronchi are fewer in number irregularly branched, bidirectional flow
  • Number of parabronchi depends on how much gas exchange is needed
  • Parabronchi have hexagonal shape
  • Connect to air capillaries
  • Constant volume
61
Q

Describe the structure and function of the avian air sac system

A
  • Ensure always fresh gas on exchange surfaces
  • Act as bellows
  • 8 or 9 sacs (depends)
  • 3 pairs and 2 singles or 4 pairs and 1 single
  • Divided into cranial and caudal
  • Cranial: cervical (pair), thoracic (pair) and interclavicular (single)
  • Caudal: thoracic (pair) and abdominal (pair)
  • Also used for evaporative heat loss and sound protection
62
Q

Describe the role of the skeletal system in avian respiration

A
  • Pneumatic
  • Connected to respiratory system
  • Fracture can decrease efficiency of respiration
63
Q

Describe the function of the nasal cavity in the bird, including water and thermoregulation

A
  • Filtration of air
  • Humidification
  • Olfaction
  • Thermoregulation
  • Nasal conchae act as heat exchangers by evaporative cooling
  • As temperature increases, so does water saturation of air exhaled
  • During exhalation and as temperature decreases, water condenses
  • Leads to reclaiming of water
64
Q

Describe the counter current exchange system and gas exchange in the avian lung

A
  • Blood and gas flow in opposite directions (both unidirectional)
  • Always higher concentration of O2 in the air than in the blood, so diffusion into blood will always occur
  • Gas exchange is continuous due to continuous supply of fresh gas on exchange surfaces
65
Q

Describe the structure of the primitive heart and contortional changes during early development

A
  • From cardiogenic plate of mesodermal tissue at head of embryonic disc
  • Rapid development and flexion lead to cardiac disc lying below head and mouth, but cranail to foregut (will become lungs, endoderm)
  • Primitive cardiac tube made of 2 lateral extensions of cardiac discs, hollowed out, fold laterally
  • Primitive tube has 5 zones: truncus arteriosus, bulbus cordis, ventricle, atrium, sinus venosus
  • Folds and falls to right = d-looping
  • Atria migrate to left and right and fuse to ventricle
  • Sinus venosus still connected to atria
  • Chambers form due to blood pressure and flow
  • Heart partitions in order: atria, AV canal, bulboventricular loop, truncus arteriosus, aorticopulmonary septum
  • Blood to heart from sinus venosus into atria
  • Into common ventricle then out via truncus arteriosus
  • Right horn os SV incorporated into atrial wall, left horn = coronary sinus
  • AV endocardial cushion develops between left and right AV orifices
  • Atria and ventricles divided by proliferation of atrial cushions
  • Fuse
  • Interventricular septum and setpum primum of atria develop
  • Septum secundum forms foramen ovale
  • Right to left shunting continues
  • Do not fuse until increase presure in LA and reduced pressure in RA
  • Secondary interventricular forament closes due to further growth of muscular interventricular septum , endocardial cusions tissue and spiral rides from septation of truncus and pulmonary arches
  • Plugs hole
  • Blood enters right atrium from sinus venosum via septum spurium
66
Q

Explain the importance of the endocardial cushions in heart development

A
  • Provide basis for division of heart into chambers
  • To divide atria septum primum grows down towards cushion, septum secundum grows up out of cushion, to meet in the middle
  • Forms foramen ovale
67
Q

Explain how the bulbus cordis divides to for the aorta and pulmonary artery, and how vessels communicate with the ventricles

A
  • Bulbus cordis and truncus arteriosus need to split
  • True septation
  • Bulbar cushions in bulbus cordis and truncal cushions in TA fuse to form aorticopulmonary septum, move up TA
  • Forms a sprial, rotates down clockwise to form truncal septum
  • From middle of bulbus cordis to 6th aortic arch and 3rd and 4th arches
  • Vessel lumens enlarge, truncus expands and 2 cahnnels completely separate into pulmonary trunk and aorta
  • Aorta arches over pulmonary artery
  • Aorta is from LV, pulmonary artery is from RV
68
Q

Describe the process of trabeculation in cardiac embryology and its importance

A
  • Occurs due to mesencymal and myocardial cells dividing
  • Endocardial cells undergo apoptosis
  • Give rise to uneven surface of ventricles
  • Important for retention of muscular and tendinous cords including papillary muscles
  • Support AV-valves
69
Q

Describe the formation of the AV valves

A
  • Reshaping and tissue loss within ventricular walls
  • Ventricle dilates and walls hypertrophy
  • Trabeculation occurs
  • Strands of cardiac wall mesenchyme from AV cushions to ventricle wall remain
  • Form cusps of AV valve and chorda tendinae
70
Q

Describe the formation of the pulmonary artery and aorta

A
  • True septation of bulbus cordis and truncus arteriosus
  • Following formation of truncal ridges get 3 swellings in walls of aorta and pulmonary artery trunks
  • Expand into lumen of each vessel
  • Very broad then become thin with cellular degradation
71
Q

Describe the cardiac anatomy of fish

A
  • One atrium, one ventricle
  • Rudimentary valve between the 2
  • Conus arteriosus runs to gills
  • Sinus venosus remains in fish
72
Q

Describe the cardiac anatomy of amphibia

A
  • Single ventricle (funtionally but not anatomically divided), 2 atria
  • Sinoatrial valves and sinus venosus reamians
  • Also possess rudimentary semilunar valves
  • Flap of tisse separating right and left TA
73
Q

Describe the cardiac anatomy of reptiles

A
  • Heart position dependent on breed
  • Iguanids heart in thoracic inlet
  • Monitors more conventional heart position
  • 2 atria, right and left ventricle
  • Sinus venosus remains
  • Blood enters from 2 anterior vena cava, hepatic veins and coronary arteries
  • Right and left aortic archa and 1 pulmonary vein
74
Q

Describe the cardiac anatomy of chelonians

A
  • Single venticle (functionally but not anatomically divided), 2 atria
  • 2 large carotid and subclavian arterial trunks
75
Q

Describe the cardiac anatomy of birds

A
  • Larger than mammals
  • Larger left ventricle
  • Atrioventricular valve is muscular flap
76
Q

Describe the cardiac anatomy of snakes

A
  • 3 chambered heart
  • 2 atria, one ventricle with partial septation
  • Caudal ventricle and 2 cranial VC drain into sinus venosus
  • Sinoatrial valve between SV and RA
  • Paired AV valves
  • 2 aortic arches
  • Right goes to bicarotid trunk then fuses with left aortic arch caudally in midline
77
Q

Define the functional role of the heart in the mammmalain circulatory system

A
  • Transport (oxygen, CO2 nutrients, waste, heat, hormones)
  • Homeostasis (pH, osmolarity, electrolytes, infection)
  • Other (generate pressure - renal filtration and reproduction), protection as transport WBC and Ig
78
Q

Describe the principal functions of a cardiorespiratory system and appreciae how the various components of such a system are structure to fulfil these function

A
  • Pump blood, provide oxygen, remove waste
  • Deoxygentated blood pumped through RHS of heart to lungs to be oxygenated
  • Oxygenated then passes through LHS of heart to be pumped into the body
  • Here capillaries perfuse tissues and provide a large surface area for exchange of nutrients
79
Q

Describe the structures of the cardiorespiratory system and how these are integrated

A
  • Heart: main pushing force for blood to move around body
  • Lungs: site for gas exchange in order to remove waste gases such as CO2 and re-oxygenate the blood
  • Veins: carry blood back to heart once gas exchange has taken place in tissues
  • Arteries: carry blood to the tissue from the heart in order to provide the oxygen
  • Capillaries: increase surface area for maximised diffusion in tissues
  • Portal veins: run between 2 capillary beds
80
Q

Describe the basics of the cardiac cycle

A
  • Systole: contraction of ventrilces. Cardiac output and produces “lub” sound by blood hitting valves = S1
  • Diastole: relaxation of ventricles and ventricular filling, “Dub” sound, involves semilunar valves at base of PA and aorta, loudest over base = S2 (closure of semilunar valves)
  • S3 = sound made by ventricular filling
  • ## S4 = sound made by atrial contraction
81
Q

Describe the necessity for a dual circulatory system in the adult mammal

A
  • Prevents mixin go f oxygenated and deoxygenated blood

- Ensure highest concenration possible of oxygenated blood pumped into systemic circulation

82
Q

Desribe the structure and function of the cardiac skeleton

A
  • Separates atria and ventricles from one another
  • Insulates the heart so only AV bundle can get through
  • Means contraction is synchronised
  • Maximises pumping ability
  • Called ossa cordis
83
Q

Describe the structure and function of the atrioventricular valves

A
  • Tricuspid on right, mitral on left
  • Prevent leakage of blood into ventricles before atrial contraction
  • Prevents back flow of blood into atria during ventricular systole
84
Q

Describe the structure and function of the semilunar valves

A
  • Sit at base of PA and aorta
  • Prevent backflow into ventricles during diastole
  • Pause where pressure in ventricles great enough to close AV valves but not high enough to open semilunar valves
85
Q

Describe the flow of blood through the adult mammalian heart

A
  • Into RA from body via cranial and caudal vena cava
  • Atria contract
  • Blood into RV through tricuspid valve
  • Contract
  • Blood into PA through semilunar valve
  • Blood into LA from lungs through pulmonary veins
  • Atria contrac
  • Blood into LV through mitral valve
  • Ventricles contract
  • Blood into aorta to body via semilunar valve
86
Q

Compare structure and function of cardiomyocytes with skeletal muscle cells

A
  • Cardiomyocytes cylindrical and striated
  • Short branched fibres with many mitochondria
  • At Z-lines have intercalated discs which are gap junctions
  • Desmosomes for force transfer
  • Functional syncitium
  • Facilitates fast AP passage due to presence of T-tubules and sarcoplasmic reticulum
  • Cannot regenerate if damaged
  • Myogenic
87
Q

Describe coronary circulation

A
  • Right and left coronary arteries
  • Left bigger
  • Coronary arteries arise from coronary sinus above aortic valve
  • Perfusion occurs during ventricular diastole
  • Great cardiac vein is coronary sinus
88
Q

Describe the landmarks of the heart

A
  • Ventral border of lungs at cardiac notch (which is bigger on the left)
  • Lungs also lateral with thymus cranially
  • Diaphragm caudally
89
Q

Describe the relative positions of the heart

A
  • LA sits in back and in the middle
  • Aorta out of middle of heart
  • RA right side of heart
  • RV in front of LV
  • LV is bigger
  • PA is on left side of animal
90
Q

Give the key points about the right atrium

A
  • Blood enters via cranial and caudal vena cava
  • Intervenous tubercle on roof of atrium causes blood to be diverted into atrium
  • Contains SAN and coronary sinus
  • Azygous vein transports deoxygenated blood from posterior walls of thorac and abdomen into the superior vena cava
  • Foramen ovale present in RA
91
Q

Give the key points about the left atrium

A
  • Dorsal and caudal to right atrium
  • Under tracheal bifurcation
  • Blood enters via groups of pulmonary veins in 2 or 3 sites
  • In septal wall scar of valve of foramen ovale
92
Q

Give the key points about the right ventricle

A
  • In front of left ventricle
  • Cresenteric in section
  • Wraps around left ventricle cranially and to the right
  • Pulmonary artery is cranial and to left of aorta
  • 1/3 of size of LV
  • Lower pressure than in LV
  • Volumes roughly equal
93
Q

Give key points about the left ventricle

A
  • Circular in section
  • Occupies entire apex
  • Prominent papillary muscles
  • Aorta is ventral
  • Most easily seen when ultrasounding heart
94
Q

Describe the sequence of valve positions in the four pahses of the cardiac cycle and the corresponding changes in volume and presure in each chamber

A
  • Atrial systole: AV open, semilunar closed
  • Isovolumetric contraction: AV closed, semilunar closed
  • Ventricular systole: AV closed, semilunar open
  • Isovolumetric relaxation: AV closed, semilunar closed
95
Q

Describe the distribution of ions across the membranes of excitable cardiac cells

A
  • Cell has negative charge - protein anions
  • Permeable to K+ at rest, enters down electrical gradient
  • Results in efflux of potassium
  • Negative resting membrane potential
  • Draws K+ back into cell (1K+ enters as 1K+ leaves)
  • Na+ also attracted down electrical gradietn
  • Active transport keeps Na+ low
  • Na+/K+ ATPase pump (3Na+ out for 2K+ in)
  • Na+/Ca2+ antiporter removes calcium from cytosol
  • Energy obtained from sodium passing down electrochemical gradient
  • High conc of anions, moderate K+, low Na+, low Ca2+ in cell
  • Low K+, moderate Na+ and high Ca2+ outside cell
96
Q

Define the term transmembrane potential

A

Potential difference between the interior of a cell and the intersittial fluid beyong the membrane

97
Q

Name the types of gateed channels in the cardiac cell membrane and describe how they exert their effects

A
  • Voltage gated K+ channels: activated by specific depolarising voltage change. Allow efflux of potassium to repolarise cell
  • Voltage gated Na+ channels: activated by localised depolarisation from neighbouring cells, allow rapid influx of NA+ to depolarise and cause AP
  • L-type calcium channel: long lasting, maintain AP, respond to higher membrane potentials, open more slowly, allow influc of Ca2+
  • T-type calcium channel: transient voltage gated calcium channels, shorter time open, initiation of AP, found in pacemaker cells, SAN and AVN primarily
98
Q

Outline the cellular and ionic events leading to cellular depolarisation

A
  • Pacemaker cells spontaneously depolarise
  • Occurs when cations enter polarised cell
  • AP in contractile cells initiated when AP from SAN reaches them
  • Occurs rapidly due to an increase in membrane permeability of Na+
  • Opening of voltage gated Na+ channels
  • Closing of voltage gated K+ channels
  • First sodium, then calcium, then repolarised with potassium
  • 5 phases
  • Rapid depolarisation, incomplete repolarisation, plateau phase, rapid repolarisation, electrical diastole
99
Q

Describe what occurs during rapid depolarisation (phase 0) of the cardiac action potential

A
  • At threshold potential of ~-60mV voltage sensitive fast Na+ channels open quickly
  • More Na+ in
  • Overcomes outward current through K+ channels = rapid upstroke
  • T-type Ca2+ channels open at membrane potentials between -70mV and -40mV
  • Calcium influx
  • Influx of Na+ has positive feedback effect and more Na+ channels open
100
Q

Describe what occurs during incomplete repolarisation (phase 1) of the cardiac action potential

A
  • Depolarisatio of ~0.5mx inactivates Na+ channels
  • No inward current of Na+
  • K+ ions leave cell via transient outward channels
  • Cell dows not repolarise as Ca2+ channels still open

VetMed Year 1 (13 decks)

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