Cardioresp ILOs and Answers PDF

AGEP 1 CARDIORESPIRATORY ILOS AND ANSWERS Mollie Kelly UOB Table of Contents Cardiorespiratory system overview...................................................................... 7 Summarise the structures of the cardiorespiratory system.......................

AGEP 1 CARDIORESPIRATORY ILOS AND ANSWERS Mollie Kelly UOB Table of Contents Cardiorespiratory system overview...................................................................... 7 Summarise the structures of the cardiorespiratory system........................................... 7 Respiratory System Organs/Structures......................................................................................... 7 Cardiovascular System Organs/Structures.................................................................................... 7 Describe the anatomical location of the cardiorespiratory system................................ 7 Describe the key functions of the cardiorespiratory system.......................................... 8 Functions of the Respiratory System........................................................................... 8 Cardiovascular System Functions............................................................................... 8 Describe and explain the physiological considerations of how both systems work together..................................................................................................................... 8 Pulmonary Considerations of Cardiorespiratory System................................................................ 9 Summarise the histology of the cardiorespiratory system............................................. 9 Begin to interpret normal anatomy on diagnostic images such as radiographs and echocardiograms. Recall there are lots of di/erent imaging modalities....................... 10 Magnetic Resonance Image (MRI)............................................................................................... 10 Ultrasound................................................................................................................................ 11 Radiography.............................................................................................................................. 11 Computed tomography (CT)....................................................................................................... 11 Imaging of the thoracic cavity..................................................................................................... 11 Pathogens and the respiratory tract.................................................................... 11 Associate pathogen, disease and animal................................................................... 11 Explain how animals become predisposed to infection.............................................. 11 Characteristics of Shipping fever, Influenza virus infections, cat flu, kennel cough, aspergillus infection, psittacosis, bovine tuberculosis............................................... 12 Shipping Fever........................................................................................................................... 12 Influenza (‘Flu’).......................................................................................................................... 12 Feline and Canine Respiratory Disease....................................................................................... 12 Fungi......................................................................................................................................... 13 Public health implications of respiratory infections in animals................................... 14 Chlamydiosis and Public Health................................................................................................. 14 Avian Chlamydiosis................................................................................................................... 15 Psittacosis – Public Health Concerns.......................................................................................... 15 Tuberculosis and Public Health.................................................................................................. 15 Upper Respiratory Tract Structure and Function 1............................................... 16 Explain the nasal cartilages determine the form of the nostril (cf. brachycephalic dog breeds)..................................................................................................................... 16 Demonstrate the significance of the alar cartilage in relation to the false nostril in the equine patient.......................................................................................................... 16 1  Define the term concha and explain the scrolling for diSerent species........................ 17 Canine...................................................................................................................................... 17 Equine...................................................................................................................................... 17 Bovine....................................................................................................................................... 17 Summarise the meatuses are the spaces between the turbinates, name each meatus, and recall where each meatus leads to...................................................................... 17 Explain what the paranasal sinuses are..................................................................... 18 Explain the paranasal sinuses of the horse................................................................ 18 Upper Respiratory tract Structure and Function 2............................................... 19 Describe the bones of the hyoid apparatus and the anatomical location of the hyoid apparatus................................................................................................................. 19 Explain the function of the hyoid apparatus............................................................... 19 Describe the location of the guttural pouch and their function.................................... 19 Name and explain the structures indenting the guttural pouch and the clinical significance.............................................................................................................. 20 Explain the location of the larynx in relation to surrounding anatomical structures...... 20 State the functions of the larynx................................................................................ 21 Recall the cartilages of the larynx and their articulations to one another, including species diSerences.................................................................................................. 21 Outline the intrinsic muscles of the larynx recalling their location, action, and innervation............................................................................................................... 21 Explain the laryngeal folds, the laryngeal ventricles, and the regions of the larynx....... 21 Describe and explain the origin and path of the recurrent laryngeal nerves................. 22 Appreciate and recall the anatomical diSerences of the larynx of diSerent species..... 23 Appreciate the clinical significance of the larynx in the horse..................................... 23 Pharmacology................................................................................................... 23 Define the terms pharmacokinetics and pharmacodynamics..................................... 23 Describe how drugs cross membranes...................................................................... 23 Define bioavailability"............................................................................................... 23 Outline the general principles of drug absorption....................................................... 23 "Outline the routes of administration for medicines and explain how the diSerent routes influence the absorption of drugs"............................................................................. 23 k. Intravenous....................................................................................................................... 23 l. Intramuscular................................................................................................................... 24 m. Subcutaneous.................................................................................................................. 24 Oral.......................................................................................................................................... 24 n. Inhalation......................................................................................................................... 24 2  o. Epidural/Spinal, Transmucosal (oral and rectal) and transepithelial..................................... 24 Outline the principles of drug distribution.................................................................. 24 Briefly outline general principles of drug metabolism and excretion............................ 25 Explain what receptors and ligands are...................................................................... 26 Summarise the main targets for drugs and identify the time-scale in which drugs exert their eSects via diSerent types of receptor"............................................................... 27 Define the term therapeutic index............................................................................. 28 Describe the blood-brain barrier................................................................................ 28 Name the major neurotransmitters in the body and state where they are found........... 28 Outline the characteristics of drugs that may cross the blood-brain barrier................. 29 Identify situations that may alter the integrity of blood-brain barrier........................... 29 Nasal and Paranasal sinus anatomy - Lab........................................................... 29 Breathing Systems............................................................................................ 30 State the functions of an anaesthetic breathing system.............................................. 30 Identify the components of a breathing system.......................................................... 31 "Summarise the types of breathing system, identify how they eliminate expired carbon dioxide and explain how to calculate their fresh gas flow requirements"..................... 31 Select the most appropriate breathing system for a clinical case................................ 33 Outline the eSects of: leaving the APL valve closed; excessive resistance; and excessive dead space............................................................................................................... 34 Lower Respiratory Tract Structure and Function 1/2............................................ 34 Name the functions of the respiratory system............................................................ 34 Outline the borders of the thoracic cavity and the importance of the pleura................ 35 Describe the location, composition and innervation of the diaphragm........................ 35 Discuss the location of the trachea and explain the histology of the trachea and bronchial tree........................................................................................................... 35 Explain the branching of the tracheobronchial tree and the segmentations of the lungs................................................................................................................................. 36 Discuss the histology of the alveoli in relation to gaseous exchange............................ 37 Recall the lung lobulation pattern of diSerent species................................................ 37 Explain the blood supply and lymphatics of the lungs................................................. 38 Recall the location and function of the muscles of respiration.................................... 39 3. Explain pleural pressure and transpulmonary pressure....................................... 41 3  Explain how lung compliance, alveolar surface tension and resistance in the airways aSect ventilation...................................................................................................... 42 Explain the term dead space in relation to the respiratory system............................... 43 Explain alveolar ventilation....................................................................................... 43 Oxygen and Carbon Dioxide Transport................................................................ 44 Explain the term partial pressure and what it means.................................................. 44 Outline why oxygen is required by the cell for metabolic processes and why CO2 and H2O are produced..................................................................................................... 45 Describe and explain the respiratory membrane........................................................ 45 2. Use a diagram to explain the partial pressure diSerences that promote gas diSusion during ventilation..................................................................................................... 46 Explain what is meant by ventilation : perfusion mismatching.................................... 47 3. Explain the role of haemoglobin......................................................................... 47 4. Explain the Neural Regulation of respiration....................................................... 48 Voluntary Regulation of Respiration........................................................................... 49 Upper respiratory tract anatomy and clinical techniques - Lab............................ 50 The Heart.......................................................................................................... 50 1. Explain the topographical location of the heart including species diSerences...... 50 Describe the atria of the heart................................................................................... 50 Describe the ventricles of the heart........................................................................... 51 Right Ventricle........................................................................................................................... 51 The Left Ventricle....................................................................................................................... 52 Describe the skeleton of the heart............................................................................. 52 Describe the conduction system of the heart............................................................. 52 Describe the circulatory system in the foetus (i.e. the flow of blood, oxygenation, placenta, foramen ovale, ductus arteriosus, ductus venosus etc.).............................. 52 Describe the changes in foetal circulation after birth................................................. 54 Vascular Tone................................................................................................... 55 The Heart as a Pump.......................................................................................... 55 Explain the events of one cardiac cycle (one heartbeat).............................................. 55 Atrial and Ventricular Diastole.................................................................................................... 55 Atrial Systole............................................................................................................................. 55 Ventricular Systole..................................................................................................................... 56 Aorta Pressure........................................................................................................................... 56 Ventricular diastole.................................................................................................................... 56 Atrial Diastole............................................................................................................................ 56 4  Atrial Systole............................................................................................................................. 56 2. Be able to interpret and explain Wigger’s diagram............................................... 57 Explain the relationship between stroke volume, heart rate and cardiac output........... 58 Explain the factors which influence stroke volume (i.e. end-diastolic volume and end- systolic volume)....................................................................................................... 58 Recall that cardiac defects are the result of abnormal pressures, volumes, and workloads created in the cardiac chambers............................................................... 60 Pharmacology of local anaesthetics.................................................................. 61 Describe the basic pharmacology of drugs used to produce local anaesthesia with reference to crossing the cell membrane, the Na+ channel and membrane electrophysiology..................................................................................................... 61 Give examples of practical applications of the use of local anaesthetics in veterinary species.................................................................................................................... 63 List the unwanted (toxic) eSects of local anaesthetic agents and how they may be treated/managed...................................................................................................... 67 Imaging of the Thorax and Heart......................................................................... 68 The ECG............................................................................................................ 69 Explain the ionic basis of the resting membrane potential and threshold potential in excitable cells.......................................................................................................... 69 "Illustrate the action potential in a myocardial cell and explain the movements of ions at each stage of the action potential. "........................................................................... 70 "Explain how action potentials in the sinoatrial node and skeletal muscle diSer and draw labelled.................................................................................................................... 71 The AP from the SA node propagate through the myocardium where they cause rhythmic contractions diagrams to illustrate each of them. ".................................................... 72 "Describe the anatomical landmarks for attachment of ECG leads to small and large animals for obtaining an electrocardiograph what is meant by the ter meanms Leads I, II and III. ".................................................................................................................... 73 3. Identify the parts of an ECG............................................................................... 74 Thoracic Wall Practical - Lab.............................................................................. 75 Regulation of blood pressure............................................................................. 76 Outline the limits of these regulatory systems........................................................... 78 Short Term Regulation................................................................................................................ 78 Long Term Regulation................................................................................................................. 79 Briefly summarise the concepts of renal and cerebral perfusion autoregulation.......... 80 Define how to identify hypo and hypertension and list possible consequences........... 80 5 Monitoring the Cardiovascular and Respiratory Systems using equipment........... 81 "Outline how each of the techniques works and explain how to attach and obtain readings from each of the monitoring modalities "..................................................... 84 Interpret the outputs from each of the monitors at a basic level.................................. 84 Lungs and Mediastinum Practical...................................................................... 85 BuYers and acid base balance........................................................................... 85 Define the term pH and state the normal pH of the body............................................. 85 Define the terms acidosis and alkalosis..................................................................... 86 Synthesise a homeostatic regulatory model for pH regulation.................................... 86 Explain what a buSer is and state the main compounds which act as buSers within the body......................................................................................................................... 89 Describe the bicarbonate carbonic acid buSer system – the most important buSer system..................................................................................................................... 89 Outline how proteins (Hb and albumin) and phosphates act as buSers........................ 90 "Investigate how to obtain and handle venous and arterial blood samples for blood gas analysis and outline the diSerences that you would expect between each type of sample"................................................................................................................... 90 The Heart and Great Vessels Practical - Lab........................................................ 90 ANS.................................................................................................................. 90 State ‘normal’ heart rate, respiratory rate and temperature ranges in dogs and cats..... 93 "Identify specific ANS targets for pharmacological intervention; give indications and examples of drugs that may be used in this regard".................................................... 94 Define the term ‘syncope’......................................................................................... 94 Explain pathophysiologic processes that lead to sudden collapse in dogs and cats. Create a logical diSerential diagnosis list for patients with episodic collapse.............. 94 Vasculature of the neonate – Practical............................................................... 95 IV Fluid therapy and IV techniques – Practical..................................................... 96 Exotics -............................................................................................................ 96 1. Describe the anatomy of the reptile respiratory system....................................... 96 Explain the control of respiration of reptiles............................................................... 97 Describe the anatomy of the avian respiratory system................................................ 98 Explain the respiration cycle of birds......................................................................... 98 Explain how fish breath under water......................................................................... 100 End of System Quiz.......................................................................................... 101 6 Cardiorespiratory system overview Summarise the structures of the cardiorespiratory system. Respiratory System Organs/Structures i. Pharynx – Passageway for air and food ii. Larynx – Regulates Air Flow and Produces Voice iii. Nasal Cavity – Turbinate Bones iv. Oral Cavity v. Trachea – Open conducting tube, Cartilaginous rings vi. Bronchial Tree – Open conducting tubes, Mucociliary escalator vii. Bronchiole – Bronchi branch to bronchiole viii. Lungs ix. Alveoli – Gas Exchange Cardiovascular System Organs/Structures x. Heart xi. Blood–fluid connective tissue xii. Vessels 1. Arteries 2. Veins 3. Capillaries Describe the anatomical location of the cardiorespiratory system. b. Lungs and heart and associated tubes for each system are in the thorax c. Tubes of lung extend to the neck d. Tubes leaving and entering the heart extend to the rest of the body e. The heart is located within the mediastinum between the two lungs within its serous membrane lining (pericardium) f. Lungs covered in visceral pleura and pleura covering the lungs sit in the pleural cavity – lungs don’t sit directly in the cavity because they are covered in pleura 7 Describe the key functions of the cardiorespiratory system. Functions of the Respiratory System i. To conduct oxygen rich inspired air along the respiratory passages to the alveoli of the lung ii. To allow gaseous exchange to take place iii. To conduct the expired air containing carbon dioxide out of the body iv. Olfaction (smelling) v. Speech/noise production Cardiovascular System Functions vi. Systemic and Pulmonary Circulation vii. Transport to tissues and organs: 1. Oxygen 2. Nutritive Substances 3. Immune Substances 4. Hormones 5. Chemicals necessary for normal functions viii. Carries away waste products and carbon dioxide ix. Regulates blood pressure and supply of blood to tissues x. Helps regulate body temperature Describe and explain the physiological considerations of how both systems work together. xi. Schematic to explain the relationship xii. Veins = away from an organ xiii. Arteries = to an organ 1. Oxygenated blood from the lungs goes to left side of the heart (left atrium) 2. The oxygenated blood is them ejected from the left side of the heart (left ventricles) through the aorta (an artery) to supply the organs of the body 3. The organs then use the oxygen and the veins drain the deoxygenated blood back to the right side of the heart 4. The right side of the heart then ejects the blood into the pulmonary artery (going to the lungs) to be re-oxygenated. The process then starts again. 8 Pulmonary Considerations of Cardiorespiratory System xiv. Air flows into the lungs due to pressure gradients, which are mainly created because of the negative pressure of the pleural cavity xv. Blood gets to the lungs because of the pumping of blood around the body by the heart 1. Mammals have two pumps and two circulations. While amphibians have one pump and one circulation xvi. The negative pressure of the thorax also ‘pumps’ the venous return back to the heart (known as the thoracic pump) xvii. The two pumps of mammals (left side of heart and right side of heart) must pump the same volume of blood to ensure the flow to the lungs equals the flow to the rest of the body. xviii. The cardiovascular system vessels must also perfuse the parts of the lungs ventilated for gas exchange xix. Thus, there must be a matching of ventilation and perfusion between the two systems (ventilation: perfusion matching) xx. Both are linked in maintaining gaseous exchange which is vital to homeostasis xxi. Both are essential for varying levels of activity with body size and exercise xxii. Both were influenced in major ways by the laws of physics 1. Flow through tubes 2. Gravity 8𝑣𝑙 𝑉𝑎𝑠𝑐𝑢𝑙𝑎𝑟 𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒 = 𝜋𝑟 ! xxiii. Both are controlled by the autonomic nervous system Summarise the histology of the cardiorespiratory system. g. Pseudostratified ciliated columnar epithelium with Goblet cells (Respiratory Epithelium) h. Epiglottis, vocal cords, and vestibular folds lined in stratified squamous epithelium. Rest lined in respiratory epithelium i. Trachea composed of (inside to outside) i. Respiratory epithelium ii. Fibrocartilaginous layer of c-shaped cartilage iii. Outer advenitia j. Bronchi is similar to trachea but plaques of cartilage and a muscular layer k. Bronchioles, similar to bronchi but Clara cells instead of Goblet Cells 9  l. Alveoli comprised of inner squamous epithelium (pneumocytes type I and II), surrounded in elastic tissue, and endothelial cells from surrounding capillaries. Structure of capillaries a. All blood vessels have an internal lining of endothelial cells (epithelial tissue) b. Capillary walls are thin and consist of a single layer of endothelial cells supported by a basement membrane General Structure of Blood Vessels c. Tunica adventitia = supportive tissue layer d. Tunica media = muscular layer e. Tunica intima = endothelial cell, basement membrane, and connective tissue layer (lamina propria) Cardiac Histology f. Three basic layers of the heart wall are (outside to inside): i. Epicardium ii. Myocardium iii. Endocardium g. Myocardium is composed of cardiac muscle cells h. Endocardium is a single layer of flattened endothelial cells Begin to interpret normal anatomy on diagnostic images such as radiographs and echocardiograms. Recall there are lots of di/erent imaging modalities Magnetic Resonance Image (MRI) ii. Magnets are spun around the patient creating an electromagnetic field which the H+ of the body respond to. 10 Ultrasound iii. Soundwaves (ultra high frequency soundwaves) are directed at the patient and are either absorbed or reflected back to the probe producing an image on the screen Radiography iv. Created by directing x-ray beams at patient and producing a shadowgraph of the area Computed tomography (CT) v. Essentially a radiograph but rather than the x-ray beam being static it spins around the patient and moves along in slices to build a 3D image Imaging of the thoracic cavity vi. In first opinion practice the main imaging modality you will most likely have access to is radiography, ultrasound is another common imaging modality in first opinion practices. 1. Air causes a lot of reverberation of of sound waves and thus the air filled lungs are dificult to image, but the fluid filled heart can be imaged (Echocardiography) Pathogens and the respiratory tract Associate pathogen, disease and animal a. Endogenous – animals own flora (bacteria) i. Disease requires predisposition ii. Known as ‘commensal organisms’ iii. Tricky to diagnose b. Exogenous – from another animal (obligate) or the environment i. Obligate pathogens (can only reproduce inside a host) c. Types of Respiratory Pathogens i. Viruses (Influenza, Parainfluenza, Coronavirus, Herpesvirus) ii. Bacteria (Mannheimia spp., Bordetella spp., Pasturella spp., Chlamydia spp.) iii. Fungi (Aspergillus spp., Mucor spp.) Explain how animals become predisposed to infection d. Animal age/nutritional status/stress/pregnancy/crowding 11  e. Immunosuppressive drugs f. External factors – temperature, air quality, cleanliness i. AND/OR efort from the pathogen (virulence factors) 1. Toxins Characteristics of Shipping fever, Influenza virus infections, cat flu, kennel cough, aspergillus infection, psittacosis, bovine tuberculosis Shipping Fever ii. Transportation à Stress à Hormonal Efects (Corticosteroids e.g. cortisol) à Primary Respiratory Viral Infection (e.g. Parainfluenza virus) à Damage to alveolar macrophages à Secondary bacterial infections (E.g. commensal Mannheimia haemolytica) à Pneumonia iii. Consequences; Severe bacterial (broncho)pneumonia Influenza (‘Flu’) iv. Influenza A viruses (i.e. H1N1) 1. Hemagglutinin (H) Binds to host cell 2. Neuraminidase (N) Allows exit of virus from host cell v. Pathogenesis 1. Viral binding to host cell and invasion 2. Cell death 3. Release inflammatory mediators (cytokines and chemokines) 4. Macrophage damage 5. Opportunistic bacterial infection vi. Strains and Public Health 1. Equine influenza (H3N8) 2. Swine influenza (H1N1, H3N2) a. Pigs have human and avian influenza cell receptors b. > ‘Mixing Vessels’ > New influenza pandemic strains vii. Influenza A viruses 1. Avian Influenza (H5N1, H7N7) can present in diferent pathogenic strains – Low and High Feline and Canine Respiratory Disease viii. Cat “Flu” – Feline Respiratory Disease Complex 1. Viruses; Feline herpes virus 1, Feline calicivirus 12  2. Bacteria; Chlamydophila felis, Brodetella bronchiseptica, Other opportunistic bacteria. ix. Infectious tracheobronchitis ‘Kennel Cough’. Multifactorial disease 1. Viral Challenge; Canine parainfluenza virus, Canine adenovirus 2 2. Secondary Bacterial Infection; Bordetella bronchiseptica, Other opportunistic bacteria 3. Diseases associated with Bordetella; a. B. bronchiseptica (zoonosis) i. Pigs. Atrophic rhinitis (Bronchopneumonia) ii. Dogs. Kennel Cough (Bronchopneumonia) iii. Cats. Feline Respiratory Disease Complex (Bronchopneumonia) b. B. pertussis/B. parapertussis i. Humans. Whooping cough (children) x. Pathogenesis of Bordetella 1. Obligate parasites: URT commensals 2. Dogs, pigs, cats, horses, rodents 3. Endogenous (commensal) or exogenous infections (inhalation) 4. Attach to ciliated epithelium + afinity for mucus 5. No further invasion but produce toxins a. Cillostatic b. Cillotoxic 6. Damage to innate immune system > secondary infection Fungi xi. Mycotic respiratory infections – Aspergillosis 1. Aspergillus fumigatus Pathogenesis. Infectious, non- contagious fungal disease of birds and mammals 2. Pathogenesis (similar in all species) a. Inhalation of spores b. Germination of spores in the respiratory tract c. Formation of fungal hyphae d. Immunocompromised animals unable to destroy and clear hyphae e. Hyphae invade tissue causing inflammation and extensive damage xii. Types of Aspergillosis – 1. Avian (Usually associated with chronic stress, unsanitary conditions, overcrowding or malnutrition) 13  a. Acute – Young Birds b. Chronic – Adult Birds 2. Chronic Aspergillosis – Mammals a. Canine nasal aspergillosis b. Invasive aspergillosis c. Chronic Aspergillosis – Equine Nasal Granuloma Public health implications of respiratory infections in animals Chlamydiosis and Public Health The Chlamydiaceae – Pathogensis 3. General Disease Trends a. Mucus Membrane associated – respiratory, gastrointestinal, conjunctival, urinogenital b. More systemic – arthritis, encephalomyelitis c. Asymptomatic infection d. Variable routes of infection Elementary body (EB) 4. Infectious Form 5. Inactive Reticulate body (RB) 6. Active intracellular form 7. Environmental stress: RB > AB’s (Aberrant Bodies) Life Cycle 14 Avian Chlamydiosis xiii. Psittacosis – psittacines (Budgies and Parrots) xiv. Ornithosis – sparrows, fowl, pigeons 1. High mortality 2. Survivors = subclinical carriers 3. Subclinical persistence + clinical flares 4. Stress à EB shed in faeces 5. à Acute Systemic Disease (Young Birds) à Adults Birds à Ocular/nasal discharge, diarrhoea à Inhalation of EBs. Psittacosis – Public Health Concerns xv. Zoonotic infectious disease in humans usually contracted from infected birds xvi. Human Infection (‘Parrot Fever”/ “Grannies Disease”) 1. 70% from pet birds 2. Turkeys (increasing) Pathogenesis 3. Inhalation of dried faeces/discharges 4. Pneumonia (contagious) 5. Death in 20% of untreated human cases Tuberculosis and Public Health xvii. Bovine Tuberculosis (Mycobacterium bovis) 1. Gram Positive Bacteria 2. Mycobacterium bovis (zoonotic) 3. M.bovis and M.tuberculosis can afect wide range of species Public Health Implications 4. Over 60% of human infectious disease originates from animals (zoonotic pathogens) many of which are respiratory 5. Respiratory pathogens can be transmitted easily between species 15 Upper Respiratory Tract Structure and Function 1 Explain the nasal cartilages determine the form of the nostril (cf. brachycephalic dog breeds). a. The external nose is the cartilaginous part of the muzzle covered in skin b. The cartilaginous part of the external nose can vary in i. Form ii. Size iii. Number c. The cartilages attach to the nasal septum forming the lateral and dorsal margins/boundaries of the nostril d. The cartilages determine the form of the nostril opening: i. Pig = round ii. Horse = Comma shaped, due to large alar cartilage e. The nostrils (nares) vary between species in terms of i. Form ii. Size iii. Orientation iv. The skin surrounding the nostrils f. The external nose is divided into two separate left and right vestibules (space/cavity) which are entered via the nostrils leading to the nasal cavities. Demonstrate the significance of the alar cartilage in relation to the false nostril in the equine patient. g. Because of the large alar cartilage in the horse, the nostril is divided into: i. Ventral – the true nostril leading to the nasal cavity ii. Dorsal – the false nostril leading to a skin pouch (located in the nasoincisive notch on the skull) 1. Important to known when ‘passing a stomach tube’ in the horse i.e nasogastric intubation h. In the horse, the nasolacrimal duct opening can be easily seen on the floor of the vestibule on clinical exam 1. The nasolacrimal duct is a tubular structure running from the lacrimal sac and opening on the floor of the nasal vestibules a. Fluorescein Test 16 Define the term concha and explain the scrolling for diKerent species. i. Choana = Opening at the back of nasal passage j. Chonchae are delicate scrolls that run the length of the nasal cavity Canine Equine Bovine Summarise the meatuses are the spaces between the turbinates, name each meatus, and recall where each meatus leads to. k. The turbinates project into the nasal cavity from the dointl and lateral walls l. The conchae comprise of i. Dorsal Concha – Rostral System ii. Ventral Concha – Rostral System iii. Ethmoidal Conchae – Caudal System – Involved in olfaction m. The space between the conchae (i.e. the remaining air passages within the nasal cavity) are called the nasal meatuses n. The nasal cavities are openly connected to the paranasal sinuses. o. 17  2. "Apply your knowledge of nasal anatomy to visualise the passage of a nasogastric tube in the equine patient." Explain what the paranasal sinuses are. a. The Paranasal sinuses are diverticula (extensions) of the nasal cavity b. The sinuses are air filled cavities in the bones of the skull c. The openings between the nasal cavity and sinuses are generally narrow allowing slow exchange of air d. Lined with mucosa which can become thickened due to inflammation and congestion i. Combined with the narrow openings between sinuses and the nasal cavity they are prone to blockage e. Functions of paranasal sinuses i. Provide some thermal and mechanical protection to the orbit and, nasal and cranial cavities ii. Increase the surface area of the skull for muscular attachment without increasing weight (because they are hollow) iii. Afect the resonance of the voice Explain the paranasal sinuses of the horse. f. Clinically important i. Paranasal sinuses in dog are poorly developed g. On each left and right side of the skull, the horse has: i. Frontal sinus – sinus in the frontal bone of the skull. Continuous with the closed cavity of the dorsal conchae. Drains into the caudal maxillary sinus. ii. Rostral maxillary sinus – Sinus with the maxillary bone of the skull. Dorsal to the 3rd and 4th cheek teeth iii. Caudal maxillary sinus – Sinus within the maxillary bone of the skull. Dorsal to the 5th and 6th teeth 1. (Caudal Maxillary Sinus and Rostral Maxillary Sinus are divided by an oblique bony septum between about the 4th and 5th cheek teeth) iv. Dorsal conchal sinus v. Ventral conchal sinus vi. Sphenopalatine sinus and ethmoidal sinus (less important) h. Frontomaxillary opening – opening between frontal sinus and caudal maxillary sinus i. The infraorbital canal is a bony tube carried on a bony plate and runs the length of the cavity of the maxilla bone of the skull. 18  i. Contains the infraorbital nerve 1. Branch of the trigeminal nerve which is cranial nerve V ii. This is the bony tube that runs through the system, separating the rostral maxillary sinus from the ventral conchal sinus. j. Drainage i. The rostral and caudal maxillary sinus drain through the nasomaxillary opening into the middle meatus ii. The conchofrontal sinus drains through the frontomaxillary opening to the caudal maxillary sinus and then through the nasomaxillary opening of the caudal maxillary sinus iii. The sphenopalatine and ethmoid sinuses drain to the caudal maxillary sinus and then through the nasomaxillary opening of the caudal maxillary sinus. Upper Respiratory tract Structure and Function 2 Describe the bones of the hyoid apparatus and the anatomical location of the hyoid apparatus. a. The hyoid apparatus is made up of five bones all of which are paired except for one: i. Stylohyoid (paired) ii. Epihyoid (paired) iii. Ceratohyoid (paired) iv. Basihyoid v. Thyrohyoid (paired) Explain the function of the hyoid apparatus. b. Provides attachment for both tongue and the larynx. Important during swallowing muscles inserting onto the hyoid apparatus pull the hyoid apparatus rostrally and with it the larynx. Thus, preventing food entering the larynx/trachea Describe the location of the guttural pouch and their function. c. Unique to the horse (and Perissodactyla) and is located deep within the head d. A diverticulum/sac of the auditory tube mucosa e. Capacity of 300-500ml f. Two, one on the LHS and one on the RHS of the head (i.e. one for each auditory tube) 19  g. The auditory tube connects the tympanic cavity (middle ear) to an opening in the wall of the nasopharynx i. Boundaries of the Gutteral Pouch 1. Dorsally – base of skull and atlas 2. Ventrally – Pharynx and start of oesophagus 3. Laterally – pterygoid muscles (muscles of mastication, paired) 4. Medially – the dorsal parts of the guttural pouches are separated by muscles of the head, ventrally two pouches meet and form a thin median septum ii. The floor of the pouches lie mainly on the pharynx, but also cover over part of the stylohyoid bone iii. The stylohyoid bone creates a ridge within the sac, dividing the pouch into lateral and medial compartments (the medial is larger than the lateral) Name and explain the structures indenting the guttural pouch and the clinical significance. h. Structures touching/indenting the wall of: i. Medial compartment 1. Glossopharyngeal nerve (CN IX) 2. Vagus nerve (CN X) 3. Accessory nerve (CN XI) 4. Hypoglossal nerve (CNXII) 5. Sympathetic trunk 6. Internal carotid artery 7. Medial retropharyngeal lymph nodea ii. Lateral Compartment 1. Facial nerve (CNVII) 2. External carotid artery 3. Maxillary vein Explain the location of the larynx in relation to surrounding anatomical structures. i. Located ventral and caudal to the pharynx and cranial to the start of the trachea/tracheobronchial tree j. Cranially the hyoid apparatus suspects the larynx (meaning it shifts during swallowing) k. The larynx is made up of i. Cartilages of diferent shapes 20  ii. Articulations (joins) between the cartilages iii. Ligaments and folds iv. Muscles State the functions of the larynx. l. Provide protection to the airways m. Production of voice n. Regulation of airflow through the glottis e.g. straining o. Close the airway Recall the cartilages of the larynx and their articulations to one another, including species diKerences p. The main shell of the larynx is made up of four main cartilages (from rostral to caudal) i. Epiglottic Cartilage – Most rostral, consists of small stalk and leaf like blade ii. Arytenoid Cartilage (paired) – Pyramidal shaped, contains vocal, muscular, and corniculate processes iii. Thyroid Cartilage – Largest cartilage, trough shaped, deep ventral notch in horse and caudally cricothyroid ligament iv. Cricoid Cartilage – signet ring shaped, most caudal Outline the intrinsic muscles of the larynx recalling their location, action, and innervation. q. Cricothyroideus m. Innervation = cranial laryngeal nerce (CN X) – Tense vocal cords r. Cricoarytenoideus lateralis m. = Abduct vocal cords (i.e. widens glottis) s. Cricoarytenoideus dorsalis m. = Adduct vocal cords (i.e. narrows glottis) t. Arytenoideus transversus m. = Close the glottis u. Thyroarytenoideus m. = Adjust the tension of the vocal folds. Give rise rostrally to the ventricularis muscle and caudally to the vocalis muscle. v. B,c,d,e,f innervation = caudal (recurrent) laryngeal nerve (CN X ). All insert on arytenoid cartilage Explain the laryngeal folds, the laryngeal ventricles, and the regions of the larynx. w. Aryepiglottic folds (mucosal) – Extends between the epiglottis and the arytenoid cartilages x. The larynx also has many other mucosal folds running between the cartilages 21  i. Vocal fold/cord 1. Extends from the vocal process (arytenoid cartilage) to the thyroid cartilage ventrally 2. Contains the vocalis muscles and the vocal ligament 3. When vibrates produces vocalisation ii. Vestibular fold (aka ventricular fold) 1. Extends from muscular process (arytenoid cartilage) to ventral thyroid 2. Runs rostrolateral to the vocal fold 3. Contains the ventricularis muscle 4. Not present in ruminants (tends to be less well distinct) iii. Laryngeal Ventricle 1. Between the vocal fold and the vestibular fold there is a diverticulum (sac) called the laryngeal ventricle – not present in ruminants iv. Regions of the larynx 1. Internal cavity can be divided into regions a. Aditus larynges – entrance to larynx b. Laryngeal vestibule – space between the entrance and the glottis (longitudinally) c. Rima glottidis/glottic cleft – the space within the glottis (transversely), diamond shaped d. Infraglottic cavity – the space after the rima glottidis (i.e. the cavity of the cricoid cartilage) i. Glottis = vocal folds and arytenoid cartilages ii. Infra = beneath, further on Describe and explain the origin and path of the recurrent laryngeal nerves. y. The left and right recurrent laryngeal nerves branch from the left and right vagus nerves (CN X) in the thorax at the level of the heart and travel cranially back up to the larynx z. At the level of the heart i. The left recurrent laryngeal nerve wraps around the aorta to travel cranially ii. The right recurrent laryngeal nerve wraps around the right subclavian artery to travel cranially. 22 Appreciate and recall the anatomical diKerences of the larynx of diKerent species. Appreciate the clinical significance of the larynx in the horse. Pharmacology Define the terms pharmacokinetics and pharmacodynamics a. Pharmacokinetics – studying the efect the organism has on the drug b. Pharmacodynamics – studying the action of the drug on the organism Describe how drugs cross membranes. c. Transport across membranes essential – site of action i. Aqueous difusion ii. Passive lipid difusion – important iii. Facilitated difusion (transport proteins) iv. Pinocytosis v. Active Transport Define bioavailability" d. The fraction of a dose reaching the systemic circulation after administration compared to the same dose administered intravenously e. The term ‘bioequivalence’ relates to comparisons between products and generic alternatives and is used by regulatory authorities Outline the general principles of drug absorption f. Drug molecules are usually small weak acids or weak bases g. Ionization determined drugs cross biological membranes by passive difusion h. Ionized drug molecules cross by specific selective transport mechanisms, facilitated difusion or pinocytosis i. Tissue pH can change e.g., infection j. Absorption influenced by route of administration and drug formulation "Outline the routes of administration for medicines and explain how the diKerent routes influence the absorption of drugs" k. Intravenous – Fastest route, IV access may be challenging, IV administration à right heart à lungs à systemic circulation, peak 23  concentration influences by rate of injection, can use constant rate infusions (CRIs) and target controlled infusions (TCI) to maintain plasma concentrations. l. Intramuscular – Absorption variable (local blood flow, diTusion through tissue), May produce an aversive response – painful, care with injection site in production animals, aspirate before injection m. Subcutaneous – Absorption may be slower than IM and unpredictable, less painful than IM injection, injection site influences absorption as do the temperature of skin, dehydration and shock, species variability in the amount of SC tissue Oral n. Inhalation – drugs that can be vaporized (e.g. inhalation anaesthetics) or aerosolised (e.g. salbutamol, steroids for treatment of respiratory conditions), uptake into systemic circulation/local efect o. Epidural/Spinal, Transmucosal (oral and rectal) and transepithelial (e.g. skin, cornea, nasal mucosa, intramammary. Both are direct to site of action – doses may be lower than systemic administration. Remember systemic uptake. i. Absorption primarily in small intestine ii. Low lipid soluble and strong acids and bases are usually poorly absorbed iii. Factors afecting gastrointestinal absorption 1. Gastrointestinal motility 2. Splanchnic blood flow 3. Particle size and formulation 4. Physicochemical factors iv. First pass metabolism (enzymes in GIT wall and liver) Outline the principles of drug distribution p. Apparent volume of distribution = amount of drug administered/plasma concentration – Theoretical concept q. Five important factors determining drug distribution i. Protein binding ii. Tissue binding iii. Organ blood flow iv. Membrane permeability v. Drug solubility r. Drug Distribution: Protein Binding 24  i. Plasma protein binding – Albumin binds weak acids, a1-acid glycoprotein binds weak bases ii. Plasma protein binding doesn’t elicit a response – unbound or ‘free’ fraction can interact with receptors/difuse across membranes iii. Tissue binding can be specific or non-specific s. Organ blood flow, membrane permeability and drug solubility i. Drugs initially distributed to organs with high blood flow 1. Fat and bone poorly perfused – long time for drugs to reach equilibrium ii. Membrane permeability 1. Previously covered iii. Highly lipid soluble drugs can accumulate in fat iv. Assume most drugs can cross the placenta and be secreted into milk Briefly outline general principles of drug metabolism and excretion t. Clearance and half life (single compartment model) i. Clearance – defined as the volume of plasma from which drug is completely removed per unit time ii. Half life – the time taken for the plasma concentration to fall 50% of its initial value 1. Rate constant K = clearance / volume of distribution u. Drug Metabolism i. Termination of drug efects – primarily biotransformation then excretion ii. Most drugs are lipophilic and highly plasma protein bound – not easily filtered by kidneys iii. Kidney excretes polar water soluble compounds most easily – Lipid soluble drugs metabolised to water soluble drusg before renal excretion iv. Liver is primary organ of metabolism – Gastrointestinal tract, lungs, kidney, skin and plasma have some metabolic activity v. Hepatic Metabolism i. Phase I convert drug to more polar metabolite 1. Oxidative, hydrolytic or reductive reactions 2. Cytochrome p450 pathways ii. Phase II conjugation with substrates 1. Requires energy 2. Resultant more polar compound more readily ecreted 3. May involve a subsequent reaction 25  4. Glucuronidation (not cats) 5. Acetylation (not dogs) 6. Methylation or conjugation with sulfate or glycine groups iii. Drugs may be activated by metabolism e.g. suxibuzone to phenylbutazone iv. Drugs may have active metabolites e.g. ketamine and nor- ketamine v. Drugs may have toxic metabolites e.g. paracetamol vi. Enzyme involved in metabolism may be inhibited or induced w. Drug Excretion i. Renal excretion most common 1. Biliary excretion 2. Exhalation via lungs 3. Gastrointestinal tract ii. Renal – may be active via tubular secretion or passive by glomerular filtration iii. May need to alter dose in animals with renal compromise x. How do drugs work i. Non-cellular Mechanisms 1. Physical eTects e.g. lacrilube applied to eyes 2. Chemical reactions e.g. ranitidine on gastric HCl 3. Physicochemical mechanisms e.g. poloxalene for frothy bloat in cattle 4. Modification of body fluid composition e.g. mannitol, hypertonic saline ii. Cellular Mechanisms 1. Physicochemical/biophysical mechanisms e.g. sevoflurane, polmyxin B 2. Cell membrane structure and function modification e.g. insulin 3. Enzyme inhibition e.g. NSAIDs 4. Receptor mediated eTects e.g. opioids Explain what receptors and ligands are y. Ligand – Substance that forms a complex with a biomolecule to serve a biological purpose z. Receptors – Proteins interacting with extracellular physiological signals and converting them to intracellular efects i. Receives a signal ii. Transduces the signal to iii. An efector mechanism 26  Summarise the main targets for drugs and identify the time-scale in which drugs exert their eKects via diKerent types of receptor" aa. Molecular targets for drug action i. Receptors – transduce signal from drug 1. Ionotropic (receptor-operated channel) – fast (msecs) e.g. nicotinic acetylcholine receptor 2. Metabotropic (G-protein coupled) – medium (secs to mins) e.g. histamine receptor 3. Tyrosine kinase receptors – medium (secs to mins) e.g. insulin receptor 4. DNA-linked receptors (intracellular) – slow (hours) e.g. glucocorticoid receptor ii. Enzyme – activate or switch of iii. Transporters – carry molecule across membrane iv. Ion channels – open or close v. Nucleic acids – afect gene transcription vi. Miscellaneous – lipids, metal ions etc. 1. Rang and Dales Pharmacology 2. "Define the terms: agonist; partial agonist; antagonist; and inverse agonist and state an example of each" a. Afinity – how well/avidly a drug binds to its receptor b. Intrinsic Acitvity/Efcacy – magnitude of efect once bound c. Full Agonist i. Able to generate maximal response after binding to the receptor ii. High afinity and high intrinsic activity iii. E.g. morphine, methadone, fentanyl all full agonists at the mu opioid receptor, a G- protein coupled receptor in CNS d. Partial Agonist – Drug that has intrinsic activity of less than 1. Receptor occupancy produces a submaximal efect i. E.g. buprenorphine binds the mu opioid receptor though doesn’t produce a maximal efect even if the dose is increased. e. Inverse Agonists – drug binds and exerts an opposite efect to the endogenous agonist i. E.g. antihistamines acting at H1 and H2 receptors f. Antagonist – Exhibits afinity but no intrinsic activity i. E.g. naloxone, an opioid antagonist or atipamezole which antagonises the a2-adenoreceptor against dexmedetomidine g. Potency – relates to the dose of drug required to produce a response 27 Define the term therapeutic index h. Maximum non-toxic dose/minimum efective dose i. LD50/ED50 j. Very crude measure of drug safety i. Based on data that may not be clinically relevant ii. Efective dose can be extremely variable depending on what is being treated e.g. pain severity can vary significantly iii. Doesn’t account for idiosyncratic drug reactions Describe the blood-brain barrier k. Anatomical and function barrier between the systemic circulation and the CNS l. Highly selective membrane i. Enable passage of essential nutrients e.g. glucose ii. Prevent entry of foreign substances m. Blood vessels lined with densely packed endothelial cells with tight junctions n. Contains enzymes e.g. monoamine oxidase – converts monoamine to non-active metabolites Name the major neurotransmitters in the body and state where they are found o. Nicotinic i. Ligand gated ion channel ii. Two Ach molecules cause ion channel to open and increase cation conductance iii. Causes depolarisation iv. Response time is less than 1ms v. Located in neuromuscular junction, autonomic ganglia and adrenal meduall p. Muscarinic i. G protein-coupled receptor ii. One Ach molecule binds and activates second messenger pathways iii. Response time is about 400ms iv. Located on parasympathetic postganglionic synapses and sympathetic postganglionic synapses (sweat glands) 28 Outline the characteristics of drugs that may cross the blood-brain barrier q. Active transport and facilitated difusion predominant method of molecular transfer r. Active transport i. Glucose and hormones s. Facilitated difusion i. Low molecular weight, lipid soluble drugs e.g. inhalation anaesthetics ii. Large polar molecules e.g. muscle relaxants cannot cross iii. E.g. glycopyrrolate (containing quaternity charged nitrogen molecule) cannot readily cross through atropine, a tertiary amine, can. Identify situations that may alter the integrity of blood-brain barrier t. Inflammation i. Meningitis, abscesses ii. Permeability to drugs increases e.g. therapeutic efect of penicillin u. Physical disruption i. Head injury/haemorrhage ii. Central neurotransmitters released into circulation. Nasal and Paranasal sinus anatomy - Lab 1. Describe the bones of the hyoid apparatus and the anatomical location of the hyoid apparatus. 2. Explain the function of the hyoid apparatus. 3. Describe the location of the guttural pouch and their function. 4. Name and explain the structures indenting the guttural pouch and the clinical significance. 5. Explain the location of the larynx in relation to surrounding anatomical structures. 6. State the functions of the larynx. 7. Recall the cartilages of the larynx and their articulations to one another, including species diMerences 8. Outline the intrinsic muscles of the larynx recalling their location, action, and innervation. 29  9. Explain the laryngeal folds, the laryngeal ventricles, and the regions of the larynx. 10. Describe and explain the origin and path of the recurrent laryngeal nerves. 11. Appreciate and recall the anatomical diMerences of the larynx of diMerent species. 12. Appreciate the clinical significance of the larynx in the horse. Breathing Systems 1. "Define the terms: dead space; tidal volume; minute volume; metabolic oxygen requirements; and re-breathing" a. Dead Space – Volume of gas that does not eliminate carbon dioxide b. Tidal Volume – Volume of gas entering the lung at each inspiration c. Minute Volume – Volume of gas entering the lungs in each minute d. Metabolic Oxygen Requirements – Amount of oxygen required each minute for metabolic processes e. Re-breathing – ‘Rebreathing occurs when the inspired gas/es reaching the alveoli contain more CO2 than can be accounted for by mere re- inhalation from the patients dead space gas (should be negligible) State the functions of an anaesthetic breathing system f. Provide O2 +/- anaesthetic agent g. Enable IPPV or spontaneous ventilation h. Enable scavenging of expired gases i. Remove CO2 1. Adrenaline release 2. Tachycardia 3. Tachypnoea ii. Remove waste anaesthetic gases 30 Identify the components of a breathing system i. Non-rebreathing system (Ayres T-Piece) j. Circle "Summarise the types of breathing system, identify how they eliminate expired carbon dioxide and explain how to calculate their fresh gas flow requirements" k. Non-rebreathing Breathing Systems i. T-Piece, Bain and Lack (Magill rarely used) ii. Fresh gas flow removes expired carbon dioxide iii. Higher fresh gas flow 1. Increased pollution risk 2. Heat and moisture lost 3. More expensive to run iv. Inspired agent should be same as that on the vaporiser 31  v. Low resistance and lightweight vi. Some suitable for IPPV – T-Piece and Bain vii. Cheap to purchase l. Rebreathing Systems i. Soda lime removes expired carbon dioxide ii. Circle (and To and Fro though this is rarely used now) iii. Lower fresh gas flow 1. Lower pollution risk 2. Heat and moisture retained (soda lime) 3. Less expensive to run iv. Slow changes in inspired anaesthetic agent concentration v. Can be used for ventilation vi. Higher resistance vii. Can be used for ventilation (IPPV) m. Breathing system calculations are estimates only and give you a starting point n. Non-rebreathing systems i. Minute volume = tidal volume x respiratory rate ii. Tidal volume – use 10mL/kg as a starting point (variation in textbooks 10-20mL/kg in dogs and 7-9-15mL/kg in cats) iii. Fresh Gas Flow (ml/kg/min) = minute volume x circuit factor 1. Circuit factors – multiple minute volume, T-piece and Bain 2-3 and Lack 1) o. Rebreathing Systems i. Minimum FGF = metabolic oxygen consumption (large animals 5mL/kg, small animals 10mL/kg) 1. The closer the flow is to these values the lower the margin for error 2. Accurate flow meters and vaporiser required at low flows ii. Semi-closed FGF>metabolic oxygen consumption and the valve is open to allow excess gas to pass into the scavenging system iii. In practice we use a high FGF initially and then reduce to 1L/min in small animals up to 100kg 2. "State the main characteristics of and identify: T-Piece; Bain & Lack (Non-rebreathing) and Circle (Rebreathing)" a. A T-Piece with Jackson Rees Modification i. 8-10kg with valve, smaller bain without valve and may be suitable for smaller animals ii. FGF = Minute volume x 2-3 iii. Can be used for IPPV iv. Low drag and dead space v. Easy to scavenge c. Lack i. Patients > 10kg (mini versions available) ii. FGF = minute volume x 0.8-1 (remember 1) iii. Not suitable for prolonged IPPV iv. Moderate drag, resistance and dead space v. Valve position facilitates scavenging and operation d. Circle i. Variety of sizes 1. Human adult circles >20kg 2. Small animal veterinary systems patients >15kg 3. Even smaller ones are available for cats and small dogs with paediatric tubing 4. Large animal versions for horses, cattle etc. ii. Unidirectional valves, soda lime canister and APL valve – resistance iii. FGF set at more than metabolic oxygen requirement 1. 1L/min oxygen adequate for most small animals up to 100kg 2. Horses and cattle – 0.5-1L oxygen per 100kg Select the most appropriate breathing system for a clinical case e. How do you select a breathing system for a clinical case? i. Size of animal – resistance, dead space, economy ii. Valve position and IPPV requirement iii. Ease of scavenging iv. Cleaning and sterilisation v. Whether you’re using nitrous oxide vi. Heat and moisture retention 33 Outline the eKects of: leaving the APL valve closed; excessive resistance; and excessive dead space f. APL Valve accidently left closed i. Reservoir bag distends ii. Reduced thoracic movements iii. Possibly leaked round ET tube cuf iv. Tachycardia, hypoxia v. Potential for pneumothorax/pneumomediastinum – rupture of lung tissue or trachea vi. Potentially fatal g. How do you recognise excessive resistance in the breathing system> i. Altered respiratory rate – low or occasionally fast ii. Decreased tidal volume iii. Hypoventilation and hypercapnia – increased end-tidal CO2 iv. Hypoxia v. Reduced alveolar ventilation may lead to “light” plane of anaesthesia vi. Altered respiratory pattern – paradoxical ventilation, increased efort vii. Unpredictable! Remember that weight ranges for breathing systems are only guidelines and an animal may not be able to cope with the resistance in a system despite being in the “correct” weight range. h. Apparatus Dead Space i. May be an integral part of the breathing system or an excessively long endotracheal tube protruding from an animals mouth ii. In small animals increasing the dead space to tidal volume ratio 1. Increases PaCO2 2. Increases the work of breathing as minute volume needs to increase to maintain PaCO2 at normal levels Lower Respiratory Tract Structure and Function 1/2 Name the functions of the respiratory system. a. To conduct oxygen-rich inspired air along the respiratory passages to the alveoli of the lung b. To allow the gaseous exchange to take place (i.e. the exchange of oxygen into the blood for carbon dioxide into the airways) c. To conduct the expired air containing carbon dioxide out of the boy 34  d. Olfaction (smelling!) e. Speech/noise production f. Temperature regulation. g. In addition to the functions mentioned before the respiratory system also: i. Regulates blood pH, by changing blood CO2 levels ii. Produces angiotensin-converting enzyme (ACE) – Important for blood pressure regulation Outline the borders of the thoracic cavity and the importance of the pleura. h. Dorsal – Thoracic vertebrae and hypaxial muscles i. Ventral – Sternum j. Lateral – Ribs, costal cartilages, intercostal muscles k. Cranial – Thoracic inlet (1at thoracic vertebrae, 1st pair of ribs, manubrium) l. Caudal – diaphragm m. Pleura and Pleural Cavity - to cushion the lung and reduce any friction that may develop between the lung, rib cage, and chest cavity. Describe the location, composition and innervation of the diaphragm. n. The diaphragm is dome-shaped in the cranial direction and reaches the level of the 6th/7th rib which is caudal of the olecranon (point of the elbow) o. The diaphragm has a tendinous centre which is the most cranial part p. The periphery is muscular (skeletal) which arises from the caudal ribs (medial surface from last rib to 8th rib), the first 3-4 lumbar vertebra, and dorsal surface of sternum q. It is innervated by the phrenic nerve (C5-C7) which arises from the brachial plexus r. Contains 3 openings for vessels, nerves and lymphatics to pass through Aortic hiatus – aorta, azygous vein, thoracic duct Oesophageal hiatus – oesophagus, and dorsal and ventral vagal nerves Caval foramen – caudal vena cava Discuss the location of the trachea and explain the histology of the trachea and bronchial tree. s. The cervical trachea keeps a median position through the neck, however the location of the oesophagus changes at diferent levels along the length of the neck 35  t. Canine Left Lateral Thorax – The thoracic trachea is bordered dorsally by the oesophagus and mediastinal lymph nodes, and bordered ventrally by the aortic arch and cranial vena cava u. Canine Right Lateral Thorax – The thoracic trachea is bordered dorsally by the oesophagus and mediastinal lymph nodes, and bordered ventrally by the aortic arch and cranial vena cava v. What is it made of? The trachea is a flexible tube of fibroelastic tissue and cartilage rings allowing it to expand (both in diameter and length) during inspiration and to passively recoil during expiration without compromising patency w. Wall of Trachea is made up of three layers i. Inner = mucosa of respiratory epithelium (remember tubes are lined in epithelium) ii. Middle = fibrocartilaginous layer composed of c-shaped cartilages that are incomplete dorsally. The ends of the c-shaped cartilages are joined by the smooth trachealis muscle (internally in large animals and externally in small animals). Between the c-shaped cartilages are sheets of elastic connective tissue iii. Outer = adventitia in the neck and serosa (mediastinal pleura) in thorax x. Explain the branching of the tracheobronchial tree and the segmentations of the lungs. y. The trachea and the bronchi form a continuous system of tubes conducting air between the larynx and the bronchioles z. The trachea and bronchi have a very similar structure and are known collectively as the tracheobronchial tree aa. At the tracheal bifurcation two primary bronchi branch serving a lung each (left and right) i. The internal ridge at the bifurcation is known as the carina 36  bb.The bronchi then repeatedly divide to form airways of decreasing diameter i. Primary bronchi ii. Secondary bronchi iii. Tertiary bronchi cc. The cartilage rings become less and less forming irregular plates with the branching until the cartilage is absent dd.The tertiary bronchi then branch into bronchioles which is marked by the absence of the cartilage rings ee. The bronchioles divide several times to become terminal bronchioles and are the last of the conducting tubes M. The terminal bronchioles then branch to form respiratory bronchioles with buds of alveoli and these are involved in gaseous exchange gg. The respiratory bronchioles give rise to alveolar ducts i. The alveolar ducts are like long corridors with many open doorways hh. The alveolar ducts open into the alveolar sacs and then open into the alveoli Discuss the histology of the alveoli in relation to gaseous exchange. ii. Alveoli are small sacs where gaseous exchange occurs between the air in the alveoli and the blood capillaries surrounding the alveoli jj. The alveolar wall consists of three tissue compartments i. Epithelium – consisting of type I (large squamous epithelial cells) and type II pneumocytes (rounded in shape and produce surfactant) ii. Connective/Supportive tissue – surrounding the alveolar wall is an elastic issue allowing the alveoli to expand during inspiration but recoil during expiration iii. Blood vessels – the basement membrane of the endothelial cells can be directly next to the basement membrane of the surface epithelium allowing rapid exchange between alveolar air and capillary blood. Recall the lung lobulation pattern of diKerent species. kk. Dog, Cat, Pig = LHS; Cranial Lobe (Cranial Part and Caudal Part) RHS; Cranial Lobe, Caudal Lobe, Middle Lobe and Accessory Lobe ll. Cow, Sheep, Goat = LHS; Cranial Lobe (Cranial Part and Caudal Part), Caudal Lobe. RHS; Cranial Lobe = Cranial Part and Caudal Part, Middle Lobe, Caudal Lobe and Accessory Lobe 37  mm. Horse = LHS = Cranial Lobe and Caudal Lobe and RHS = Cranial Lobe and Caudal Lobe + Accessory Lobe Explain the blood supply and lymphatics of the lungs. nn. The lungs have a double blood supply i. Pulmonary vascular system ii. Bronchial vascular system oo. This is because the respiratory system functions to provide oxygenated and deoxygenated blood to the whole body, as well as provide oxygen for itself. pp.The Pulmonary Vascular System i. The bronchial vascular system 1. Provides lung structures such as bronchi, airway walls, and pleura with oxygenated blood 2. The oxygenated blood branches from the aorta through bronchial arteries and continues branching along the bronchial tree to the respiratory bronchioles 3. At the respiratory bronchiole level, the arterioles anastomose with the pulmonary vascular system 4. The bronchial veins and venules also anastomose with the pulmonary veins and venules 38  5. Also a small portion of the bronchial system drains into the azygous vein which drains into the cranial vena cava, and this is the right side of the heart qq.Lung Lymphatics i. The lymphatic drainage follows the bronchi and pulmonary vessels and drains into the lymph nodes at the hilus Recall the location and function of the muscles of respiration. rr. Inspiration i. Diaphragm (most important) 1. Flattens and caudally moves domed diaphragm – when the diaphragm contracts the dome is pulled caudally and thus enlarges the thoracic cavity ii. External intercostal muscles 1. Pulls ribs cranially and outwards – during rest the diaphragm is the most important of these muscles. During physical exercise both the diaphragm and external intercostal muscles contract more forcefully along with other muscles of the neck. ss. Expiration i. Passive at rest and caused by the elastic recoil of the lungs and the thoracic cage. Always passive and only becomes active during disease exercise, excitement, stress, fever and other circumstances that increase O2 demand. ii. Internal intercostal muscles 1. Pulls ribs caudal and inward iii. Abdominal muscles 1. Accelerates forward push of diaphragm. Contraction of the abdominal muscles increases abdominal pressure, forcing the relaxed diaphragm cranially, decreasing the thorax volume. 2. "Apply your knowledge of the pleura and the thoracic cavity to explain how volume and pressure diKerences are created during ventilation." a. The lungs are covered in visceral pleura b. The thoracic wall is covered in parietal pleura c. Between two pleural surfaces is a thin layer of pleural fluid i. This provides adhesive forces meaning the lungs slide easily along the chest wall but resist being pulled away 39  1. I.e. like two moist glass slides sliding away but resist being pulled apart ii. Therefore, as the thorax expands during inhalation the lungs expand as well. 1. The thorax and lungs behave as one function unit d. The pleural cavity is maintained in a slight negative pressure (i.e. sub- atmospheric pressure) due to: i. Lymphatics continually absorb pleural fluid, creating a suction efect ii. Lung recoil pulls the visceral pleura from the parietal pleura decreasing the pressure. e. Ventilation i. Process of moving air into and out of the lungs ii. For air to move into or out of the lungs a pressure gradient is required. iii. The pressure gradient is between atmospheric pressure (the air we breathe) and alveolar pressure (the pressure inside the alveoli) 40  iv. The alveolar pressure = atmospheric pressure in the pause between inspiration and expiration v. During inspiration the thorax expands, increasing lung volume and decreasing alveolar pressure below atmospheric pressure and air enters the lungs vi. During expiration, the thorax and lungs decrease in volume, this results in alveolar pressure rising above atmospheric pressure and air moves out of the lungs vii. In dogs, expiration at rest also has an active phase viii. In horses, inspiration and expiration both have an active and passive phase ix. Factors which afect ventilation 1. Lung compliance 2. Alveolar surface tension 3. Resistance to air flow in the airways 3. Explain pleural pressure and transpulmonary pressure. a. Transpulmonary pressure represents the pull that keeps the lungs distended b. Transpulmonary pressure is a measure of the elastic forces of the lungs c. This pressure prevents the bronchioles from collapsing during inspiration d. The lung volume is determined by the balance between transpulmonary pressure and the elastic recoil of the lungs e. The transpulmonary pressure decreases and increases with lung volume i. Lung volume increases with the increased transpulmonary pressure 41 Explain how lung compliance, alveolar surface tension and resistance in the airways aKect ventilation f. Compliance is the measure of the distensibility of a structure g. The normal lung is very compliant and will readily increase the volume h. It is a measure of how much the lung volume increases for each unit increase in transpulmonary pressure i. The compliance of the lungs depends on i. How elastic the tissues of the lungs and thoracic cage ii. The surface tension on the inside of the alveoli j. Alveolar Surface Tension i. The inside of the spherical alveoli are lined with fluid ii. The fluid faces the inspired air and thus creates surface tension. 1. Surface tension is the tendency of fluids to shrink to the minimum surface area iii. Surfactant produced by type II pneumocytes reduces the surface tension k. Surfactant i. Produces by the type II pneumocytes and contains phospholipids, proteins and ions ii. Surfactant is a critical factor underlying the high compliance of the normal lung iii. Surfactant reduces the surface tension on the inside of the alveolar walls. 1. I.e. it acts like a detergent l. Airflow in tubes i. The principles of airflow are very similar to the principles of blood flow ii. Resistance to airflow – the resistance to airflow is primarily determined by the cross-sectional area and the radius of the airways 1. Similar to how we discussed with blood flow. As the radius increases the airflow increases four-fold, resistance 1/r4 2. However, with the respiratory tree there is much branching and the branching is through many parallel paths 3. Because of all the parallel branching it is the cross- sectional area rather than the diameter of the individual passages that determines the overall resistance in diferent sections of the respiratory system 4. The upper airways are a major source of airway resistance 42  5. The nasal cavity, pharynx and larynx provide about 60% of respiratory resistance in a resting animal 6. Some species, such as the horse, are obligate nose breathers 7. Horses accomplish a decrease in nasal resistance by flaring the nostrils and constricting blood vessels to shrink the nasal mucous. iii. Smooth muscle of the airways 1. There is a smooth muscle in the airways from the trachea to the alveolar ducts 2. In the trachea this in the form of the trachealis m. 3. In the bronchi and bronchioles, it encircles the airways 4. When the smooth muscle contracts it results in a narrowing of the passages (bronchoconstriction) 5. Regulation of airway diameter is by neural and other stimuli a. Neural control – i.e. the nervous system, specifically the sympathetic and parasympathetic systems b. Inflammatory mediators (e.g. histamine and some leukotrienes) Explain the term dead space in relation to the respiratory system. m. Dead space is the inhaled air that does not participate in gas exchange n. Anatomic dead space is the conducting airways from the nares to the bronchioles o. Physiological dead space is the sum of the anatomic dead space and any alveoli not involved in gas exchange (because of absent or poor blood flow) p. Generally, in the healthy individual, the anatomic and physiological dead space are the same Explain alveolar ventilation. q. The main importance of pulmonary ventilation is to renew the air in the gas exchange areas of the lungs, the alveoli, alveolar sac, alveolar ducts and respiratory bronchioles r. The rate at which airs reach these areas is called alveolar ventilation 43  s. Alveolar ventilation is the volume of air available for gas exchange per minute t. Why dogs pant – Enables increased airflow over moist surfaces in the upper respiratory tract due to rapid, shallow breathing. The increase in air flow (and contact with larger surf