Avian Pulmonology Flashcards
Discuss the location of the nares in various avian groups.
- Nares
- Perforated – Gruiformes, Cathartiformes
- Closed – Pelecaniformes
- Tip of Beak – Kiwi
- Tubular – Procellariformes
- Operculated – Psittaciformes, Galliformes
- Nasal Valve – aquatic birds – diverts water from olfactory chamber
- Nasal Gland – salt excretion
Reference: CT EPP & Samour Respiratory
What birds have a sense of smell?
- Sense of smell – kiwis, turkey vultures, petrels, albatrosses
Reference: CTEPP, Samour Respiratory
Describe the anatomy of the avian nasal cavity?
What type of epithelium is present at the various sites?
What are the functions and componenets of the nasal concha?
Are any visible through the nares?
- Nasal cavity is divided successively into nasal vestibule with squamous epithlium, (rostral nasal concha), respiratory region with mucociliary epihtlieum (middle nasal concha), and olfactory chamber (olfactory epithelium).
- Concha – Cartilaginous structures that increase SA, limit heat and water loss during ventilation.
- Rostral concha visible through nostrils in falconiformes.
- Rostral and middle conchae communicate with nasal cavity through common meatus nasalis. Caudal concha only connects to the infraorbital sinus.
Describe the sinus anatomy of birds.
What is the only paranasal sinus in birds?
How many diverticula are present?
What is the largest diverticulum?
- Sinuses
- Infraorbital sinus – Only paranasal sinus in birds. Communicates dorsally with nasal cavity and caudal concha and pneumatizes most structures of the head and neck.
- Quadrate bone, articular bone, and most bones of the braincase are pneumatized by diverticula arising from the tympanic cavity (opening is the infundibular cleft) with no connection to the upper resp system.
- Infraorbital sinus diverticula absent in cormorants.
- Amazon parrots:
- One rostral unpaired diverticulum
- Six paired diverticula
- Macaws:
- Two rostral unpaired diverticula (including transverse canal)
- Eight paired diverticula
- Psittacines – R and L sinuses communicate through transverse canal (not present in most other birds).
- Largest diverticulum of the psittacine paranasal sinus – Cervicocephalic diverticulum.
- Reaches as far as the shoulder, not connected to the lower respiratory system (not an air sac!).
- Infraorbital sinus – Only paranasal sinus in birds. Communicates dorsally with nasal cavity and caudal concha and pneumatizes most structures of the head and neck.
Why does teh infraorbital sinus not drain well?
Describe avian laryngeal anatomy.
What are the cartilages of the avian larynx? How does that differ from mammals?
Which species have a crista ventralis?
What are the primary muscles controlling the larynx?
- Larynx
- 4 cartilages – cricoid, procricoid, 2 arytenoid
- DO NOT have epiglottic, thyroid cartilages or vocal cords
- Crista ventralis
- Pelicans, hornbills, kiwis, penguins, some ducks
- Median crest inside larynx and cranial trachea
- Dilator and constrictor muscles of the larynx control the glottal opening.
- 4 cartilages – cricoid, procricoid, 2 arytenoid
Reference: M&T CTEPP, Samour, Speer - Respiratory
Describe avian tracheal anatomy, including taxonomic differences between groups.
What species have multiple loops? Where do these loops occur?
What species have tracheal sacs?
What species of bulbous expansions?
What species have double tracheas?
How do birds compensate for increased tracheal length and the associated deadspace?
- Trachea
- High variability in length and anatomy
- Lines by ciliated columnar epithelium
- Starts on midline, passes slightly to the right side of the neck and enters the thoracic inlet.
- May have multiple loops:
- In keel – Trumpeter Swans and Whooping Cranes
- Subcutaneous – curassows, Magpie Geese, Trumpeters, some birds of paradise.
- Tracheal Sacs – Emu, Ruddy Duck
- Bulbous expansions – Males of certain duck species; Rosy Billed Pochard.
- Double Trachea – Penguins, petrels.
- Septum extends from bronchial bifurcation.
- Mynahs and toucans have a slight ventral kink to trachea before entering the thorax.
- Tracheal cartillages are complete but asymmetric with broader half part usually overlapping narrow parts of two adjacent rings.
- Increased tracheal diameter to compensate for increased tracheal length.
- Tracheal dead space still ~4x mammals.
- Compensated by a larger tidal volume.
- Lower resp rate vs mammals.
Discuss avian syringeal anatomy including taxonomic differences.
What air sac surrounds the syrinx?
What are the two types of syrinx?
- Tracheobronchial (most common)
- Bronchial
- Syringeal bulla – Anatidae
- Psitaciformes – two syringeal muscle groups (superficial & deep)
- Passeriformes – five muscles
- Syrinx – Voice production.
- At bronchial bifurcation, surrounded by interclavicular air sac.
- Variations are categorized into tracheobronchial (most common) and bronchial.
- Main structures of syrinx:
- Tympanum (structural body of organ), pessulus (Divides the airway vertically), paired medial and lateral tympaniform membranes (vibrate).
- Left dilation of the tympanium (syringeal bulla) frequently present in males of Anatidae.
- Syrinx of psittaciformes lacks pessulus.
- Two unique pairs of short syringeal muscles: superficial and deep.
- Passeriformes may have up to five pairs of intrinsic syringeal muscles.
Reference - CTEPP, Samour, Speer Respiratory
Describe the unique anatomy of the avian lung.
Where are the lungs located anatomically?
Describe the branching of the bronchi from the two primary bronchi caudally.
What are the two structural units of the avian lung?
How do these differ in flow and function?
The neopulmo parabronchi are absent in what group? What group has them most well developed?
- Lung-Air Sac System:
- Lungs:
- Avian lungs are dorsal, do not enclose the heart.
- Lungs are not lobed, indented dorsally by ventral ribs.
- Caudal border of lungs may extend as far as hip joints (storks, geese).
- Lungs bordered ventrally by horizontal septum.
- Two primary bronchi -> intrapulmonary primary bronchi -> abdominal air sac.
- Four groups of secondary bronchi arise from primary bronchi:
- From cranial to caudal:
- Medio-ventral, medio-dorsal, latero-ventral, latero-dorsal secondary bronchi.
- Multiple parabronchi branch off the secondary bronchi.
- Anastomosed parabronchi carry atria -> infundibula and air capillaries (site of gas exchange).
- Parabronchial lungs divided into two structural units:
- Paleopulmo – Ventilation is unidirectional, formed by the medioventral-mediodorsal system of bronchi and parabronchi. Characterized by layers of hooplike parallel parabronchial connections between secondary bronchi.
- Neopulmo – Ventilation is bidirectional. Formed by anastomosing network of parabronchi connecting the lateroventral-laterodorsal system of bronchi to each other and other secondary bronchi. Located caudally, less than 1/3 pulmonary parenchyma. Absent in Sheniciformes, most developed in Passeriformes.
- Lungs:
What are air capillaries?
How do they differ from mammalian alveoli?
- Air capillaries anastomose (unlike mammalian alveoli which are dead-end).
- Air and blood capillaries are in cross-current pattern – Blood-gas barrier is much thinner vs mammals. Air capillaries also much smaller vs alveoli.
- This arrangement + greater surface exchange area and thinner blood-gas barrier makes avian lung more efficient gas exchange mechanism vs other vertebrates.
Describe the avian lung-air sac system including taxonomic differences.
How many air sacs do birds have?
What species are exceptions to this rule?
What structures do the various air sacs pneumatize?
How are air sacs connected to the lungs?
What is the saccobronchus?
- Air Sacs – Generally 9 total.
- 2 cervical
- 1 interclavicular
- 2 cranial thoracic
- 2 caudal thoracic
- 2 abdominal air sacs
- Exceptions
- Passerines – 7 (cranial thoracics fused to interclavicular)
- Chickens – 8 (fused cervicals)
- Storks – 11 (caudal thoracic divided in 2)
- Turkeys – 5 (no caudal thoracic, cervical fused with two primordial clavicular air sacs, one small pair of clavicular air sacs)
- Air sac diverticula pneumatize various anatomical structures.
- Cervical air sacs – Vertebral and large subcutaneous diverticula (ganets, ostriches).
- Interclavicular air sac – Many intra- and extrathoracic diverticula including two large axillary diverticula; surrounding the heart, pneumatizing the sternum, coracoids, humerus.
- Cranial and caudal thoracic air sacs below lungs.
- Abdominal air sacs largest except penguins.
- Perirenal diverticula dorsal to kidneys and femoral diverticula pneumatizing the femurs arise from abdominal air sacs.
- Air sacs connected to lungs through ostia
- Cervical, caudal thoracic, abdominal air sacs have one ostium.
- Cranial thoracic and interclavicular air sacs have two ostia (medial and lateral).
- Large number of parabronchi may form a funnel-like tubular structure (Saccobronchus, present with caudal thoracic and abdominal air sacs).
- Caudal thoracic air sacs lack connection with pneumatic bone (only one).
Describe avian respiratory mechanics including air flow through the lung-air sac system.
How do the neoplumo bronchi function differently?
Are inspiration and expiration active or passive processes?
What are the primary muscles of respiration?
Respiratory Mechanics
- Trachea 🡪 caudal air sacs (bypassing secondary bronchi through inspiratory valving) 🡪 paleopulmonic lungs through secondary bronchi 🡪 cranial air sacs 🡪 trachea
- Neopulmo connected with caudal air sacs
- Wingbeats assist ventilation
- Respiratory Mechanics and Regulation:
- Avian lung does not participate in ventilation (unlike mammals).
- Ventilation performed by air sac system.
- Bellows to ventilate lungs.
- Lungs are pracitically rigid, vary minimally in volume.
- Ventilation is both tidal (bidirectional in neopulmo, as in mammals) and through-flow (unidirectional in paleopulmo).
- Air sacs functionally divided into two groups:
- Cranial – Cervical, interclavicular, cranial thoracic.
- Receive expiratory air.
- Caudal – Caudal thoracic, abdominal air sacs.
- Receive inspiratory air.
- Inspired air -> caudal air sacs, bypassing the medioventral secondary bronchi (ispiratory aerodynamic valving).
- Expiratory air from caudal air sac -> Paleopulmonic lungs through mediodorsal seoncary bronchi by expiratory aerodynamic valving terminating in cranial air sacs.
- Crnaial air sacs -> Medioventral secondary bronchi, intrapulmonary primary bronchi, and trachea.
- Flow is bidirectional in the neopulmo, inseries with caudal air sacs.
- Two respiratory cycles necessary for a given volume of inspired air to move through the avian respiratory system.
- Both expiration and inspiration are active processes.
- Thoracic cavity is not at subatmospheric pressure as in mammals.
- Intercostal and abdominal muscles are main resp muscles, others also.
- All abdominal muscles are expiratory!
- Cranial – Cervical, interclavicular, cranial thoracic.
- Wingbeats may assist respiratory ventilation during flight in some spp.
- Volume of air sac system varies.
- Position during anesthesia may influence the air sac.
- Tidal volume lowest in dorsal recumbency.
Reference: CTEPP, Speer, Samour - Respiratory
What are the phsyiologic drivers of avian respiration?
Where are avian chemoreceptors located?
- PaCO2 – increased ventilation
- Intrapulmonary chemoreceptors – stimulated by decrease in PCO2
- Respiratory rhythm originates from brainstem, modulated by reflexes.
- Central chemoreceptors initiate increase in ventilation when PaCO2 increases.
- Arterial chemoreceptors at carotid bodies near parathyroid glands modulate ventilation in response to changes in PaO2, PaCO2, pH. Innervated by vagus nerve.
- Intrapulmonary chemoreceptors – Unique to birds and reptiles, also innervated by vagus nerve.
- Stimulated by decrease in PCO2, contrast to arterial chemoreceptors.
- Air sac mechanoreceptors also present.
- Changes in ventilation occur in response to changes in PaCO2, intrapulmonary PCO2, PaO2, and pH.
Reference: CTEPP, Speer, Samour - Respiration
List four reasons why avian species are much more sensitive to airborne toxins than mammalian species.
What are the major anatomical and physiologic differences of avian respiration compared to mammalian respiration?
Compare and contrast the clinical signs of upper, middle, and lower airway disease in avian species.
Descrbie some of the clinical implications of the advanced avian respiratory system.
How does it affect anesthesia?
What about surgery?
What about disease pathogenesis?
What about diagnostics?
What about therapeutics?
Discuss clinical sampling techniques of the avian respiratory system.
