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.)