Introduction The body’s cells need a constant supply of oxygen to produce energy. Carbon dioxide is a waste product of these energy-producing reactions and must be eliminated.
Types of Respiration External- occurs in the lungs and is the exchange of O2 and CO2 between the air in the lungs and the blood flowing through the pulmonary capillaries. Internal- occurs all over the body. It is the exchange of O2 & CO2 between the blood and the cells & tissues. Both types of respiration are constantly taking place.
Secondary Functions **Voice Production- “phonation” The process begins in the **larynx (voice box). Vocal cords stretch across the lumen of the larynx and vibrate as air passes over them.
Secondary Functions… Body Temperature Regulation- A network of superficial blood vessels just under the epithelium of the nasal passages helps warm inhaled air before it reaches the lungs. The respiratory system prevents over- heating by panting.
Secondary Functions… Acid-base Balance Regulation- For normal chemical reactions to occur, the relative acidity or alkalinity of their environment must be controlled carefully. The unit used to express acidity or alkalinity is pH. The respiratory system uses its ability to influence the amount of CO2 in the blood. The more CO2 there is in the blood, the lower the blood pH.
Nose Begins with the nostrils (nares) which lead to the nasal passages. The nasal passages are located between the nostrils and the **pharynx (throat). A midline wall separates the right from the left nasal passage called the nasal septum. The hard & soft palates separate the nasal passages from the mouth.
Nose Turbinates- Thin, scroll-like bones that help warm and humidify inspired air. They also filter particulate matter, such as dust and pollen, before it can reach the lungs.
Nose Paranasal Sinuses- Contained within the spaces of the maxillary and frontal bones of the skull.
Pharynx The nasal passages lead back into the pharynx . It is the common passageway for the respiratory and digestive systems. The soft palate divides the pharynx into the dorsal nasopharynx (respiratory passageway) and the ventral oropharynx (digestive passageway).
Pharynx… At the caudal end, the pharynx opens dorsally into the esophagus and ventrally into the larynx. The larynx & pharynx work together to prevent swallowing from interfering with breathing.
Larynx “Voice box” A short, irregular tube that connects the pharynx with the trachea. The larynx is supported in place by the hyoid bone.
Larynx…Contents… Vocal folds- the most lateral structures, located on the lateral edges of the glottis. Epiglottis- a triangular flap of tissue that covers or protects the glottis when in the “up” position. Glottis- the most ventral opening of the larynx.
Larynx…Functions Voice production Keeps foreign material out of the lungs by the trapdoor action of the epiglottis. It controls airflow to the lungs by adjusting the diameter of the glottis.
Glottis Closure of the glottis even aids in non- respiratory functions that involve straining such as: urination, defecation, and parturition. Straining begins with the animal holding the glottis closed while applying pressure to the thorax with the breathing muscles.
Glottis… This stabilizes the thorax and allows the abdominal muscles to effectively compress the abdominal organs when they contract. Without the closed glottis, contraction of the abdominal muscles merely forces air out of the lungs.
Trachea A short, wide tube that extends from the larynx to the thorax where it divides into the two main bronchi that enter the lungs. This division is called the bifurcation of the trachea and it occurs at the level of the base of the heart.
Trachea The trachea is composed of fibrous tissue and smooth muscle held open by hyline cartilage rings. If nothing held the trachea open, it would collapse each time the animal inhaled as a result of the partial vacuum created by the inhalation process. Each tracheal ring is C-shaped with the open part of the C facing dorsally. The gap of each ring is bridged by smooth muscle.
Lower Respiratory Tract Starts with the bronchi, ends with the alveoli, and includes all the air passages in between. Most of the structures in the lower respiratory tract are located within the lungs.
Bronchial Tree The air passages that lead from the bronchi to the alveoli. After it enters the lungs, each main bronchus divides into smaller and smaller bronchi until they become tiny bronchioles.** The smallest air passageways are called alveolar ducts.**
Bronchial Tree… The alveolar ducts end in groups of alveolar sacs. The diameter of each bronchi can be adjusted by smooth muscle- Bronchiodilation Bronchioconstriction
Alveoli External respiration takes place in the alveoli. They are tiny, thin- walled sacs that are surrounded by networks of capillaries. The wall of each alveoli is composed of thin epithelium.
Alveoli… The capillary walls are composed of the same thin epithelium. These two thin layers allow oxygen and carbon dioxide to diffuse back and forth.
Lungs The base of each lung lies directly on top of the diaphragm. Between each lung is an area called the mediastinum, which contains: Heart Large blood vessels Nerves Trachea Esophagus Lymphatic vessels & lymph nodes
Lungs… **The left lung has 2 lobes- Cranial and Caudal **The right lung has 4 lobes- Cranial, middle, caudal, & accessory. Each lung has a well-defined area on its medial side called a hilus where blood, lymph, and nerves enter and exit the lung.
Lungs… Physically the lungs are very light and have a spongy consistency. If a piece of lung from an animal that has taken one breath was placed under water, it would float.
Thorax A thin membrane called pleura lines the thoracic cavity and its organs. Organs- visceral pleura Cavity- parietal pleura The diaphragm is the thin sheet of skeletal muscle that forms the caudal boundary of the thorax.
Physiology… The process of respiration requires effective movement of air in and out of the lungs at an appropriate rate and sufficient volume.
Negative Intrathoracic Pressure The pressure within the thorax is negative with respect to the atmospheric pressure. A partial vacuum exists within the thorax. That partial vacuum pulls the lungs against the thoracic wall and aids in the return of blood to the heart.
Inspiration The basic mechanism for inspiration is enlargement of the thoracic cavity by the inspiratory muscles. The main muscles of inspiration are the diaphragm and the external intercostals.
Expiration The main muscles of expiration are the internal intercostals and the abdominal muscles. When abdominal muscles contract, they push abdominal organs into the diaphragm. Expiration does not require as much work because gravity pulls the ribs down helping to decrease the thoracic cavity volume.
Respiratory Volumes Tidal Volume- the amount of air inspired and expired in one breath. Minute Volume- the amount of volume inspired and expired in one minute.
Gas Exchange Occurs in the alveoli. Gas exchange follows the laws of simple diffusion. Basically, gas molecules from areas of a high concentration like to move to areas of low concentration.
Control of Breathing Breathing is controlled by an area of the brain stem known as the respiratory center. The body has two main systems that control breathing: Mechanical system Chemical system
Sinusitis Usually involves the frontal or maxillary sinus in the dog. It can manifest as a collection of pus in the area, resulting in a swelling over the sinus. It can be a result of the openings of the nasal passages swelling shut or becoming plugged. This results in the fluid from the sinuses having nowhere to go.
Sinusitis… A common cause of this problem is a tooth root abscess.
Kennel Cough Infectious Canine Tracheobronchitis Caused by the bacteria Bordatella bronchiseptica. The disease is characterized by a dry, hacking cough that can be stimulated by palpating the throat.
Tracheal Collapse This defect involves tracheal rings that lose their ability to remain firm, subsequently collapsing during respiration. ***Obese toy and miniature breeds of dogs are predisposed. The usually narrow space between the ends of several of the C-shaped tracheal rings is wider than normal.
Tracheal Collapse… When the animals inhales, the widened area of the smooth muscle gets sucked down into the lumen of the trachea and partially blocks it. This can cause a dry, honking cough and difficulty breathing (dyspnea).
Tracheal Collapse… Therapy includes: Weight loss for obese animals Exercise restriction Reduction of excitement & stress Surgical therapy
Feline Asthma p. 255 A disease characterized by spontaneous bronchioconstriction & airway inflammation. Clinical signs include: Coughing Wheezing Labored breathing
Feline Asthma… Airway epithelium may hypertrophy, goblet cells and submucosal glands may produce excess mucus, and the bronchial mucosa can become infiltrated with inflammatory cells.
Feline Asthma… All these changes result in decreased air flow. A 50% decrease in the lumen of the trachea is possible.
Feline Viral Rhinotracheitis A highly contagious disease that is extremely severe in young kittens. Infections occur year-round in both vaccinated and un-vaccinated cats. Transmission occurs through aerosolization (sneezing) and direct contact. Queens may transmit the disease to their kittens during grooming.
Pleural Effusion The build-up of fluid in the pleural space which results in respiratory distress. Right-sided CHF is the principal cause of pleural effusion in both canine & feline patients.
Pleural Effusion… As systemic venous hypertension increases, significant amounts of the fluid accumulates in the pleural space, causing respiratory difficulty.
Pleural Effusion… All pleural effusions produce symptoms of respiratory distress, dyspnea, cough, & circulatory compromise.
Pneumothorax & Lung Collapse p. 258 Pneumothorax: the presence of free air in the pleural space.
Pneumothorax & Lung Collapse… Without negative intrathoracic pressure, normal breathing cannot take place. If air leaks into the pleural space, that negative pressure is lost. This results in the lung falling away from the thoracic wall.
The dark black region on the right side of this CT image clearly shows where the lung has separated from the chest wall. Note the difference between the two lungs. One is fully expanded and fills up the chest cavity, the other is shrunken (i.e. collapsed) and only fills up part of the chest cavity.
Pneumothorax & Lung Collapse… The general cause is the air comes either from the outside, as in the case of a penetrating wound, or from the lung itself due to the rupture of the alveoli as a result of lung disease or injury.
Pneumothorax & Lung Collapse… Treatment consists of re-establishing the partial vacuum within the pleural space by: Sucking out the air with a needle. Placement of a chest tube.
Coughs, Sneezes, Yawns, Sighs, & Hiccups p. 262 All Are temporary interruptions in the normal breathing pattern. They can be: Responses to irritation (coughs & sneezes) Attempts to correct imbalances (yawns & sighs). Or they may occur for unknown reasons (hiccups).
Coughs, Sneezes, Yawns, Sighs, & Hiccups A cough is a protective reflex that is stimulated by irritation of foreign matter in the trachea or bronchi. It consists of a sudden, forceful expiration of air.
Coughs, Sneezes, Yawns, Sighs, & Hiccups A sneeze is similar to a cough, but the irritation originates in the nasal passages. The burst of air is directed through the nose and mouth in an effort to eliminate the irritant. A yawn is a slow, deep breath taken through a wide-open mouth. It may be stimulated by a slight decrease in the oxygen level of blood, or it may just be due to boredom, drowsiness, or fatigue.
Coughs, Sneezes, Yawns, Sighs, & Hiccups A sigh is a slightly deeper than normal breath. It may be a mild corrective action when the blood level of oxygen gets a little low. It may also serve to expand the lungs more than the normal breathing pattern does.
Coughs, Sneezes, Yawns, Sighs, & Hiccups Hiccups are spasmodic contractions of the diaphragm accompanied by sudden closure of the glottis, causing the characteristic “hiccup” sound.
Other Respiratory Pathology Aspiration pneumonia (p. 253)- An inflammatory condition of the lungs produced by inhalation of foreign material. Reverse Sneeze- Asthmatic symptoms, usually from post nasal drip.
Other Respiratory Pathology… Emphysema- The alveoli sacs loose elasticity, remain stretched and full, CO2 bulids up in the blood and can lead to cardiac arrest.
Other Respiratory Pathology… Pulmonary Hypertension- Left CHF, the left side of the heart can’t pump fast enough, Pressure rises, no gas exchange can occur. Pulmonary Edema- Increase in fluid in the alveoli resulting in compromised gas exchange.
Other Respiratory Pathology… Diaphragmatic Hernia A break in the diaphragm allows the protrusion of abdominal viscera into the thorax.
Collection- Tracheal Wash Orotracheal- directly through an endotracheal tube Nasotracheal- Via the nasal passages Transtracheal- Through the skin and trachea Infuse sterile saline as a wash solution May collect tracheal, bronchial or bronchioalveolar washes Collect into RRT and LTT
Analysis Record cell numbers during smear evaluation Little mucous- Decreased cell numbers Prepare smear from sediment Heavy mucous- Increased cell numbers Don’t centrifuge, make an impression smear