Pathology Flashcards
What are the 4 primary defense mechanisms of the respiratory tract?
- Particle deposition (air turbulence,warm, humid nasal turbinate air)
- Mucociliary escalator
- alveolar mø
- inflammation and pulmonary immune response
What is the number one cause of congestion/edema?
Increased capillary hydrostatic pressure
What is the main reason why horses get sick?
Because of transportation and stress
What is Hypostatic Congestion?
NO SIGNIFICANCE! Dead animal in prolonged lat recumbency -> gravity causes blood to go into side closest to ground -> post-mortem change
know its normal b/c lungs are still soft
What are other causes of edema?
- increased permeability
- injury of epithelial cells (toxic gases, 100% O2, virus infection)
- injury of endothelial cells (Virchow’s triad)
- decreased plasma oncotic pressure (chronic nephritis, cirrhosis)
- lymphatic obstruction (e.g., metastatic malignant melanoma in lung)
What is an embolus and embolism?
Embolus: Any foreign body circulating in the blood or lymphatic
Embolism: an embolus gets stuck in a smaller caliber vessel
embolism more common than thrombosis
What causes thrombus to form?
Parsites (e.g., heartworms), hypercoag. disorders, endothelial damage
Why are renal infarcts much more common than lung infarcts?
One renal artery versus a dual artery system in the lungs
need ~60% of pulmonary vasculature to be affected to have clinical signs (there are millions of vessels in the lungs!)
What is a consequence of pulmonary thrombi or emboli?
Pulmonary infarct (super rare)
What are two abnnormalities of inflation in the lungs?
Atelectasis and Emphysema
What is the defintion and causes of Atelectasis?
Atelectasis: too little air in the lung/incomplete expansion of the lung
- Congenital: fetal
- Acquired: Obstructive v. Compressive
What are cases of Congenital-caused Atelectasis?
Fetal: stillborne
Neonatal and dystocia: aspirate colostrum, hypoxic conditions
What is collateral ventilation and what species lack it?
Ventilation of alveoli via pathways that bypass normal airways; beneficial in disease states of obstructed or restricted airways as it serves as a back-up system. Bovine, swine and marine mammals lack this.
What is Obstructive - Acquired Atelectasis?
Inflammatory exudates obstructing bronchioles (or parasites, neoplasia)
What is Compressive - Acquired Atelectasis?
blood, pus or air in the lungs that causes the pleural cavity to lose its negative pressure -> lungs collapse
hemothorax, chylothorax, pneumothorax
Interstitial Emphysema
- Most common type in ruminants
- forced expiration (pneumonia, agonal breaths) causes bronchiolar collapse -> alveolar rupture -> air leaks into interlobular septa
- Remember: bovines have NO collateral ventilation! The trapped air in the distal alveoli is what causes the alveoli to rupture
Emphysema: tissue expansion by air or gas
fibrin = damage to vasculature = damage to coag cascade
Common sequela = pulmonary abscess
Granuloma: a focal cluster of macrophages/inflammatory cells that form in response to infection.
NO PUS!
What is bronchlectasis
Rupture and dilation of bronchial wall due to enzymatic effect of neutrophils and macrophages; is an irreversible lesion!
occurs in cows with mycoplasma bovis infection
Pathogenesis of fibrinous inflammation in bronchopneumonia
severe lung injury -> fibrinogen leaks out of vessels & is converted into fibrin via thrombin (clotting enzyme) -> fibrin deposits in the pulmonary tissue
Distributiom of aspiration pneumonia
cranioventral unilateral!
texture of interstitial pneumonia
elastic- alveolar walls become inflammed/thickened
embolism pneumonia
abscesses all over the lung = origin is not the lungs
Sequel to embolic pneumonia
Pulmonary abscesses
Granulomatous pneumonia in foal with Rhodococcus equi
Rhodococcus equi is a bacterium that lives in the soil and can cause pneumonia in young (1 to 6 months old) foals.
Infection progresses slowly and foals often do not begin to show clinical signs until the disease has become severe.
R. equi can infect immunocompromised humans and cause lung infections.
Many foals infected with R. equi recover, but those that are severely affected may not survive.
Good foal management, regular screening, and early detection are the best approaches to prevent R. equi infection.
Verminous pneumonia (small ruminants) – by parasites // lung worms
Protostrongylus, Neostrongylus
