Respiratory System: Anatomy and Physiology

• Study notes on the respiratory system.

Learning Objectives

• List the components of the upper respiratory tract and describe their structure and functions.
• Discuss the main issues of animals with brachycephalic obstructive airway syndrome.
• List the components of the lower respiratory tract and describe their structure and functions.
• Describe the avian respiratory system – structure and function.
• Describe the events that occur during inspiration and expiration.
• List the muscles involved in inspiration and expiration.
• Define the terms tidal volume, minute volume, and residual volume.
• Describe the processes of oxygen and carbon dioxide exchange between the alveoli and the blood.

Upper Respiratory Tract

• Includes the frontal sinus, nasal cavity, turbinates, hard palate, pharynx, tongue, soft palate, epiglottis, larynx, trachea, and esophagus.
• The Gutteral Pouch is lined with resp. epith'm
• Found in odd-toed mammals, and bats
• The Gutteral Pouch is surrounded by parotid and mandibular salivary glands.
• Viborg's Triangle: Is where the Ramus of the mandible is rostrally. Also, the Sternomandibulari s m and Linguofacial vein
• Viborg's Triangle is important, it offers surgical access to the guttural pouch for scoping

Clinical issues with the upper respiratory tract

• These issues can include bacteria or viruses, tumors, foreign bodies, parasites, and anatomy variations.
• Rhinitis or rhinotracheitis affect the upper respiratory tract

Brachycephalic Obstructive Airway Syndrome (BOAS)

• Issues in brachycephalic dogs and cats include elongated soft palate and stenotic nares, hvpoplastic trachea.
• Aberrant rostral nasal turbinates can be usually less branched and hypertrophic.
• Enlarged alar folds fall medially onto the nasal septum.
• Stenotic nares
• Caudal aberrant turbinate tissues protrude into the nasopharynx.
• The oversized tongue could displace the soft palate dorsally further obstructing the nasopharynx.
• An elongated and thickened soft palate could cause pharyngeal and nasopharyngeal obstructions.
• Hypoplastic larynx, everted laryngeal saccules, collapse of the laryngeal cartilages
• Hypoplastic trachea, tracheal collapse
• Stenotic nares surgery can be performed on French bulldogs to widen nostrils.

Larynx

• Includes the Right arytenoid, Left arytenoid, Glottis, Epiglottis, Left vocal fold
• Laryngeal folds can become paralyzed in cats
• Arytenoid cartilage/fold, vocal fold (cord), epiglottis, and glottis are key structures to know

Trachea

• Can experience tracheal collapse
• Intubation which is the insertion of a tube into the trachea, lidocaine spray prior for cats to avoid spasm of larynx

Bronchial Tree - Lower Respiratory Tract

• Is the lower respiratory airway and the bronchial tree.
• Includes the trachea, main bronchus, bronchioles, terminal bronchiole and alveoli in a pulmonary lobule
• Bronchitis is a lower airway disease.
• Pneumonia is an alveolar disease
• 1 alveolus, 2 alveoli

Mammalian Lungs

• Most domestic animals have 2 lobes on left, 4 on right.
• Horses have 2 lobes on left and 2 on right.

Avian Respiratory System Differences

• Air sacs (5 cranial, 4 caudal) exist in addition to lungs
• One way flow
• No soft palate
• Choana closes when swallowing
• No epiglottis
• No vocal cords
• Syrinx
• Tracheal cartilages complete rings
• No diaphragm
• Syrinx: An enlargement of the trachea where it bifurcates and has vibrating walls. Each side can vibrate independently creating 2 toned calls

Inspiration and Expiration

• Inspiration: Is aka inhalation, the Diaphragm contracts – from dome to flat and External intercostal muscles - contraction lifts
• Expiration: aka exhalation and the Diaphragm relaxes, Internal intercostal muscles - contraction rotates ribs back and down, Abdominal muscles may be needed
• Breathing is controlled by both brain function and subconscious responses

Control of breathing involves :

• The pons (part of brainstem) serves as a center to control rate of breathing.
• The medulla houses separate centers for inspiration, expiration, and breath holding.
• Efferent messages are sent by the subconscious to respiratory muscles
• Conscious mind can override the breathing controls
• Mechanical control involves stretch receptors in the lungs, a normal breathing pattern, and preset points

Chemical Control

• Is about Homeostasis
• Monitors CO2, pH, and O2 in arterial blood
• Involves Chemoreceptors in heart, medulla and carotid arteries and aorta

Explore the structure and function of the respiratory system. Learn about the upper and lower respiratory tracts, including the nasal cavity, pharynx, larynx, trachea, and lungs. Understand the mechanics of breathing, gas exchange, and avian respiratory adaptations.