Respiratory System Flashcards
Structure and Function: Conducting Systems
includes:
- nostrils
- nasal cavity
- paranasal sinuses
- nasopharynx
- larynx
- trachea
- bronchi
Structure and Funciton:
Transitional Systems
bronchioloes
serve as a transition zone between the conducting system (ciliated) and the gas exchange system
Structure and Function:
Gas Exchange System
formed by alveolar ducts and numerous alveoli
Normal Flora of the Respiratory Tract
Trachea and alveoli are sterile. Normal flora is restricted to the proximal conductive systems and involves many types of pathogens that vary among species and by geographic regions
Defense mechanisms:
Physical
Force high pressure exhaled air
coughing, sneezing
Defense mechanisms:
Mucociliary apparatus
- comprised of goblet and pseudostratified columnar ciliated epithelial cells
- Function in concert to move material often adherent to the mucus from the lung toward the oropharynx
- mucus gets coughed up and expelled in sputum
Defense Mechanisms:
Innate Immune System
- Neutrophils, Mast cells, Cytokines, antimicrobial peptides
Defense Mechanisms:
Adaptive Immune System
- Local lymphoid affrefates that provide cell-mediated immunity as well as immunoglobulin production
- IgA
Defense mechanisms:
Alveolar Space Defense
- Surfactants, Alveolar Macrophages, iron-binding proteins, lymphocyte-derived IgG, Lysozyme
Nasal Cavity:
Function
- Conduct and “condition” inwardly and outwardly moving air
- Condition:
- trap particulate material
- hydrates and humidifies incoming air and dehydrates or dehumidifies out-going air
- Warms incoming air and cools outgoing air
- Ambient temperature and relative humidity dependent
Nasal Cavity:
Congenital Defects:
Choanal Atresia
- Unilateral or bilateral lack of communication between nasal cavity and nasopharynx → failure of rostral and caudal nasopharynx to unite into a continuous conduit due to persistence of buccopharyngeal septum
- Seen in:
- horses
- camelids
- dogs
- sheep
Nasal Cavity:
Congenital Defects:
Paranasal Sinus Cysts
- Expansive, fluid-filled, epithelial-lined space occupying lesion of unknown cause that remains clinically silent until there is facial distrotion or compression of the ipsilateral nasal passage.
- Can lead to sinusitis, nasal discharge, boney and conchal atrophy and remodeling
- Seen in:
- Horses of any age
Nasal Cavity:
Congenital Defects:
Palatoschisis (Cleft Palate)
- depending on severity, may be compatible with life
- Direct communication between respiratory and digestive systems
- Primary consequence → Aspiration Pneumonia
- In all mammalian Species
- in horses, most often only affects the soft palate
- In cattle, typically hard and soft palate affected
Nasal Cavity:
Inflammation:
Inflammation of the nasal cavity = Rhinitis
Nasal Cavity:
Inflammation:
Serous
- Regardless of the cause, often initial discharge
- Definition:
- clear or slightly translucent discharge attributable to leaky vessles
- Mucosa is edematous and congested → narrowed passages → chonic, recurrent irritation
- Clinical Signs:
- snuffling or sneezing
- Represents the mildest form of inflammation.
Nasal Cavity:
Inflammation
Catarrhal (mucoid)
- In response to the insult, goblet cell hyperplasia and hypersecretion of mucus lead to a mucoid exudate often mixed with other inflammatory cells
- Epithelial surfaces of the upper respiratory tract initially produce more mucus as a protective response
Nasal Cavity:
Inflammation:
Suppurative
- Discharge or exudate that is neutrophil-rich
- Variable in color, but tends to be tan to green to red and is often quite thick due to mixtures of mucous and sloughed epithelium
- Typically a bacterial cause
Nasal Cavity:
Inflammation:
Fibrinonecrotizing
- Seen when the injury is more severe, reflective of the underlying cause
- Destructive, ulcerative lesions become overlayed by thick, fibrinous exudate mixed with necrotic debris and degenerate neutrophils
- Surface coverings can be divided into pseudodiphtheritic and diphtheritic membranes.
Nasal Cavity:
Inflammation:
Fibrinonecrotizing:
Pseudodiphtheritic Membranes
Fibrinous exudate taht easily separates / peels away form the mucosal surface
CAN be removed, leaving an intact underlying mucosa
Nasal Cavity:
Inflammation:
Fibrinonecrotizing
Diphtheritic Membranes
- Firmly adherent exudate
- fibrin
- necrotic debris
- inflammatory cells
- Difficult to remove and tears away underlying tissue resulting in raw and ulcerated surfaces
- Possible causes include:
- bacteria
- herpes viruses
- Fusobacterium necrophorum
Nasal Cavity:
Inflammation:
Granulomatous
- With chronicity or depending on the type of pathogen involved
- inflammatory response is more granulomatous
- Can be observed as plaques forming
- epithelial changes in response to fibrosis and distortion of the normal tissue
- With chronicity and increased depth of invasion:
- can lead to lacalized osteomyelitis and once in the bone, treatment can be very difficult
Rhinitis:
Idiopathic Lymphoplasmacytic Rhinitis
- Dogs:
- 1.5-14 years
- Chronic mucoid to mucopurulent nasal discharge
- Most common histologic diagnosis for nasal biopsies
- goal is to rule out specific causes
- Cause is not yet known, but turbinate destruction and a localized inflammatory response may set up a repeating response cycle
- In people,
- establishing links to allergens
- same link not established in animals
Rhinitis:
Allergic (Atopic) Rhinitis
- seen in DOGS, cats, horses, cattle
- Sporadic, somewhat seasonal, oculo-nasal discharge, sneezing, nose rubbing, head shaking, +/- epistaxis
- Diagnostics:
- nasal exudate contains abundant eosinophils mixed with mucous
- will be diagnosed as eosinophilic rhinitis
- Cattle:
- some develop seasonal allergic rhinitis, most often in the summertime when pastures are in bloom and pollen antigens are plentiful
- nasal discharge, lacrimation, sneezing, pruritis of nose
- Chronically:
- develop nasal granulomas comprising a granular or nodular appearance to the mucosa that is hyperplastic and thickened due to granulation tissue infiltrated by eosinophils, mast cells, lymphocytes
- Type 1 hypersensitivity mechanisms
Rhinitis:
Atrophic Rhinitis
- Progressive condition in young pigs that leads to gradual destruction of the nasal turninates
- Progressive atrophic Rhinitis
- Co-infection of Bordetella bronchiseptica and toxigenic pasteurella multocida
- Signs:
- sneezing, sniffling, nasal discharge
- Many intensive operations have eliminated this condition
Rhinitis:
Mycotic Rhinitis:
Feline Cryptococcosis
Cryptococcus neoformans
- Any tupe of cat at any age, or gender
- Often present as ulceratied and possibly deformed nose
- Immunodeficiency
- Organisms found in pigeion guano
- Lesions start out small, but can spread into the brain
Rhinosporidiosis
used to be considered a mycotic infection - investigations suggest it i an aquatic protistan parasite
May affect dogs, cats, horses and to a lesser extent cattle
Nasal discharge with nasal masses observed by rhinoscopy; histopathology depicted the microorganisms
Aural inflammatory polyps
- polypoid masses arising form the middle ear and enter the nasopharynx via the auditory tubes
- This condition most commonly affects young cats, and dogs
- Clinical signs depend on growth extension
- gagging
- dysphagia or dyspnea
- sneezing
- nasal discharge
- ataxia
- horner’s syndrome
- facial nerve paralysis
Benign Nasal Neoplasia:
Enzootic Nasal Tumor of Sheep
- unique neoplasm of sheep and goats that is virally induced
- Retroviruses induce the development of either adenomas or adenocarcinomas
- Multiple animlas can be affected in a single herd
- Locally invasive but not know to metastasize
Most common epithelial neoplasm of dogs
Nasal Carcinoma or Adenocarcinoma
Most common epithelial nasal neoplasm in Horses and Cats
Squamous Cell Carcinoma
Most common mesenchymal neoplasm dogs
Chondrosarcoma
Most common mesenchymal neoplasm in cats
lymphosarcoma
Pharynx:
Congenital Defects
Epiglottic Hypoplasia
in horses can lead to epiglottic entrapment within the aryepiglottic folds.
A short epiglottis can also lead to dorsal displacement of the soft palate.
The two lesions can occur simultaneously
Pharynx:
Inflammation:
Lymphoid hyperplasia, laryngeal, epiglottis
This is common in younger horses
Presumably due to continual antigenic stimulation associated with inhaled/ingested antigens
Is not a lesion but is considered a common finding in the epiglottal mucosa
Pharynx:
Inflammation:
Guttural Pouch Inflammation:
Gutteral Pouch Empyema
- Bacterial infection that ascends up the auditory tube resulting in suppurative or fibrinosuppurative exudate
- Most commonly, these animals will either have persisent rhinitis or sinusitis or may have dysfunctional auditory tubes, or some combination
- Streptococcus equi subsp. equi or Streptococcus equi subsp. zooepidemicus are likely the most common bacteria involved
- Concretions of inspissated guttural pouch exudate may form hard aggregates taht are radiographically evident and termed “chondroids”
Pharynx:
Inflammation:
Guttoral Pouch Mycosis
- Fungal infections, typically due to Aspergillus fumigatus,
- result in plaques that form along the mucosal surfaces
- since this pathogen is “attracted to” or throphic towards blood vessels, these plaques tend to form or migrate towards regions that overly internal carotid arteries
- Over time and as the infections worsens, fungi will invade teh artery → suppurative arteritis
- Without treatment, invaded and inflamed arteries will become necrotic and rupture → life-threatening, rapid exsanguinating hemorrhage and death
Larynx / Trachea
Congenital Defects:
Brachycephalic Airway Syndrome
- Breed-associated respiratory impairment
- stenotic nares
- Excessive length of soft palate – Elongated soft Palate
- Tracheal hypoplasia
- Severe, long-standing negative pressure at larynx → Everted laryngeal saccules
Larynx / Trachea
Congenital Defects
Tracheal collapse
Breed associated defect of tracheal cartilage rings that will progressively flatten over time
Miniature dog breeds are most commonly affected; minimal manipulation of the trachea leads to an eaily induced cough in affected animals
Collar pressure easily induces coughing when on a leash
Cartilage rings are shallow, dorsal tracheal membrane is widened resulting in dorsoventral collapse of the trachea
Larynx / Trachea
Laryngeal Paralysis
Laryngeal hemiplegia
- Paralysis of the larynx is the most common cause of abnormal respiratory noise in the horse, often called “roaring”
- Typically a left-sided phenomenon and is due to Degeneration of the left recurrent laryngeal nerve - cause is often not determined
- Nerge degeneration → denervation atrophy of intrinsic laryngeal muscles, responsible for laryngeal opening during inspiration → roaring
- Potential causes of unilateral paralysis include guttural pouch nycosis, severe bronchopneumonia, thoracic granulomatous/neoplastic disease affecting the LRN
- Bilateral paralysis is sometimes a feature of the hepatic encephalopathy and a rare post-anesthesia anomaly
Larynx / Trachea:
Inflammation:
Necrotic Laryngitis (Calf diphtheria)
- Sequelae to viral infections, bacteria Fusobacterium necrophorum
- Associated with chronic cough and this cough results in the formation of contact ulcers on mucosa of the arytenoid cartilages → focal areas of necrosis
- Recall form earlier, this is reffered to as diphtheria becuase of the typical formation of diphtheritic membranse that overlie thses areas of necrosis
- Affected calves often have noticable, severe halitosis due to these necrotic lessions
Larynx / Trachea
Inflammation
Intratracheal Fibrin Clot
Occasionally seen in aborted fetal foals
VIRTUALLY PATHOGNOMONIC for EQUINE HERPESVIRUS-INDUCED ABORTIONS
Concurrent lesions: interstitial pneumonia, may be associated with an abortion storm on the affected farm
Larynx / Trachea
Inflammation
Viral Laryngitis / Tracheitis
- Tracheitis / laryngitis due to an underlying viral infection, bacteria, and possibly inhaled gasses
- Cattle:
- disease name:
- infectious bovine rhinotracheitis (IBR)
- Cause:
- Bovine Herpesvirus-1
- disease name:
- Chickens:
- Disease name:
- infectious laryngotracheitis (ITL)
- Cause:
- Avian Alpha-Herpesvirus
- Disease name:
Larynx / Trachea
Inflammation:
Tracheal edema and Hemorrhage Syndrom in Feedlot cattle
AKA: Bovine Honkers
- Typically, a summertime disease, but uncertain pathogensis
- Segmental severe edema, mural hemorrhage of hte dorsal region of the distal 50% of the trachea
- Can lead to death by asphyxiation
Prominent Interlobular Septa
Normal
Interlobular septa are distinct and prominent in cattle and pigs
Visceral and Parietal Pleural Fusion
Normal
visceral and parietal pleural fusion is normal in elephants and Malayan Tapirs
Visceral and Parietal Pleural Fusion:
Abnormal
fibrous pleural adhesions or visceral and parietal fusion is not normal in most species
CHRONIC inflammation within the pleural space leads to FIBROUS adhesions
When the chronic inflammation is more severe, the cords of fibrous connective tissue can be replaced by broad sheets of fibrosis and leads to visceral and parietal pleural fusion
Rib impression in the lungs:
Normal
- bird lungs are anchored in the intercostal space with rib impressions and ~85% of the pleura is fused in birds
- most of the visceral and parietal pleura are fused with the dorsal most portions depicting a pleural space. Therefore, pleuritis is possible but is mostly localized to that dorsal 15%
- Since the lungs are fixed in the rib cage, movement of air is via coelomic movements that move air into and out of the air sacs
- Bird lung nomenclature:
- lung sections depict numerous parabronioles that open into thin-walled, sac-like structures called air capillaries.
- Air capillaries interstitial space contains numerous blood-filled capillaries
Rib impressions in lung
Abnormal
- Rib impressions in mammalian lungs indicates failure to collapse due to expansion of the interstitium by edema, congestion, hemorrhage, inflammation or some combination ← confirmation of underlying process always requires histologic evaluation
- Under negative pressure, expnaded interstitium by edema and inflammation compressed agianst the chest wall is more expanded ataisnt the intercostal muscles but compressed when expanded against the rib cage.
- Once the chest cavity is opened, air-filled protions of the lung deflate and leave behind an imprint of the rib cage
