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Respiratory System
Respiratory System
• Includes a series of tubes and sacs that function together with the cardiovascular system to provide the body with the exchanges of carbon dioxide and oxygen required for cellular metabolism and life – Oxygen is essential for
cellular metabolism – Cells use oxygen and
produce carbon dioxide
Respiratory System
• Nose/Nasal Cavity & Mouth/Oral Cavity– Air is warmed and
filtered
• Pharynx (throat), Larynx (voice box) & Trachea (wind pipe)– Carry air to lungs,
communication/ vocalization
Respiratory System
• Bronchi– trachea splits into two bronchi,
one leads to the left lung and the other to the right
• Bronchioles– once within the lungs the
bronchi continue to divide into these smaller tubes
• Lungs/Alveoli – the bronchioles end in small
sacs called alveoli. This is where the gas exchange takes place
Gas Exchange
• the passing of oxygen from the alveoli into the blood and the excess carbon dioxide within the blood flow passing back into the alveoli to be breathed out– each alveoli is
surrounded by capillaries
Gas Exchange
• Oxygen passes through the alveoli walls to the capillaries
• The red blood cells take up the oxygen (hemoglobin) and carry it throughout the body (organs and muscles)
• Simultaneously, carbon dioxide (waste product) is collected from organs and muscles
• Blood carries the carbon dioxide to the lungs where it passes into the alveoli to be breathed out
• What would happen if the body did not get rid of carbon dioxide?
Breathing
• Breathing IN = Inspiration• Breathing OUT = Expiration
• Main Breathing Muscles:– Intercostal
• positioned between the ribs
– Diaphragm • sheet of muscle; under ribs
and lungs
Breathing
Inspiration• The volume of the
thoracic cavity (chest) increases to draw air into the lungs – intercostal muscles and the
diaphragm contract– rib cage moves up and out
and diaphragm flattens• increases the space• decreases lung air
pressure causing air to rush in from outside
Breathing
Expiration • At the end of a
breath, the intercostal muscles and diaphragm relax– thoracic cavity volume
decreases– lung pressure
increases– Air forced out
Lung Capacity
• Tidal volume – amount of air breathed in
or out with each breath
• Inspiratory capacity – maximum amount that can
be breathed in (after a normal breath out)
• Expiratory reserve volume – additional amount you can
breathe out after breathing out normally
Lung Capacity
• Vital capacity – maximum amount of
air one can possibly breathe in or out in one breath
• Residual volume– amount of air left in the
lungs after one has breathed out as much as possible
9Lung Volumes (ml) for Normal Young Adult
Male Female
Tidal Volume 500 500
Inspiratory Reserve Volume 3100 1900
Expiratory Reserve Volume 1200 800
Total Lung Capacity 6000 4200
Functional Residual Capacity (FRC)
2400 1800
Inspiratory Capacity 3600 2400
Vital Capacity 4800 3200
Humans
Diseases/Disorders
Collapsed Trachea• trachea supported by
tough rings of cartilage
• trachea loses its rigidity and collapse while the dog is breathing (idiopathic)
• mostly seen in toy breeds– obese dogs more prone to
it
Diseases/Disorders
• Clinical Signs– Difficulty breathing,
especially during exercise– Coughing (attempt to clear
airway)– Blue gums and tongue
(severe cases)
• Treatment/Management– Limited exercise– Harness instead of collar– Diet (if obese)– Cough suppressant
(Torbutrol)– Surgery (rare)
Diseases/Disorders• Laryngeal Paralysis
– disorder in which the nerves that control the muscles and cartilage that open and close the larynx (voicebox) do not function properly, causing voice changes and difficulty with eating or breathing
– normally, the laryngeal cartilages (arytenoid cartilages) are pulled open during breathing, but with laryngeal paralysis, these cartilages do not open and close properly, making it difficult for the animal to take in air normally
Diseases/Disorders
• Etiology– Idiopathic (common)
• older, large breed dogs (Labs, Goldens, Saint Bernards, and Siberian Huskies)
• over time, the nerves and muscles that control the laryngeal cartilages lose function
– Hereditary (rare)• Dalmatian, Bouvier des Flandres, Siberian Husky and English
Bulldog• signs of breathing difficulty usually be seen by 2-6 months of age
– Injury• Trauma, such as a bite wound
Diseases/Disorders
• Clinical Signs– voice change (bark sounds
hoarse)
– noisey breathing
– gag or choke during eating
– Severe: animal cannot take in sufficient air (potentially fatal)
• Diagnosis– Under light anesthesia the
larynx is examined
Diseases/Disorders
• Treatment– Surgery (“arytenoid lateralization” or “laryngeal tie-back”)
• involves putting one or more permanent sutures to hold the arytenoid cartilage open
• usually successful
Diseases/Disorders
• Feline Viral Respiratory Diseases– highly contagious– spread rapidly – few adult cats die of
upper respiratory disease
– death rate among young kittens ~ 50%
Diseases/Disorders
• Etiology– 80-90% caused by the
herpesvirus group and the calicivirus group
• Clinical Signs– Sneezing– Conjunctivitis– Fever (pyrexia) – Eye and nasal discharge – Decrease in appetite
(anorexia)– Low energy– Depending on virus: stomatitis
and ulceration in oral cavity
Diseases/Disorders
• Diagnosis– Clinical signs– Throat cultures– Blood tests
• Treatment– Isolate affected cat– Disinfect any fomites– Antibiotics (treat secondary
bacterial infections)– Immune supplements
(vitamins, amino acids, etc.)