Chap 22: Respiratory System Flashcards

Structures of the Respiratory System

  • Overview: The respiratory system consists of the upper and lower respiratory systems, each containing various significant structures.

    • Upper Respiratory System: Includes the nasal cavity, pharynx, larynx, and trachea.

    • Lower Respiratory System: Comprises the bronchi, bronchioles, and lungs (right and left), as well as the diaphragm.

Normal Microbiota of the Respiratory System

  • Upper vs. Lower Respiratory System:

    • Lower respiratory system typically devoid of microorganisms.

    • Upper respiratory system hosts normal microbiota which help limit pathogenic growth and may act as opportunistic pathogens (e.g., Hemophilus, Streptococcus, Staphylococcus).

Bacterial Diseases of the Upper Respiratory System

  • Streptococcal Respiratory Diseases:

    • Signs and Symptoms: Sore throat, difficulty swallowing, potential progression to scarlet or rheumatic fever.

    • Pathogen: Caused by Group A Streptococcus (S. pyogenes).

    • Virulence Factors: Includes M proteins, hyaluronidase capsules, streptokinases, pyrogenic toxins, and streptolysins.

    • Pathogenesis: Infections occur when normal microbiota are depleted or when body’s immune responses are impaired.

    • Epidemiology: Spread via respiratory droplets, more frequent in winter and spring.

    • Diagnosis and Treatment: Often confused with viral pharyngitis; treated with penicillin or erythromycin for resistant strains.

  • Diphtheria:

    • Signs and Symptoms: Sore throat, fluid oozing, pseudomembrane obstructing airways.

    • Pathogen: Corynebacterium diphtheriae, which produces diphtheria toxin leading to cell death.

    • Transmission: Person-to-person via respiratory droplets; carriers may be asymptomatic.

    • Diagnosis and Treatment: Identification of pseudomembrane, treated with antitoxin and antibiotics. Prevention via vaccination (DPT).

  • Common Cold:

    • Signs and Symptoms: Sneezing, congestion, sore throat, malaise. Duration 7-12 days.

    • Pathogens: Primarily rhinoviruses, with other viral infections contributing.

    • Transmission: Coughing/sneezing, fomites, person-to-person.

    • Treatment: Supportive and palliative; pleconaril may reduce duration of symptoms.

  • Sinusitis and Otitis Media:

    • Signs and Symptoms: Sinusitis involves pain and pressure in sinuses; otitis media presents as ear pain.

    • Pathogens: Various bacteria (e.g., S. pneumoniae, S. aureus).

    • Pathogenesis: Infections follow after colds; sinusitis common in adults, otitis media in children.

    • Treatment: Symptoms are often diagnostic; managed with antibiotics.

Bacterial Diseases of the Lower Respiratory System

  • Bacterial Pneumonias:

    • Signs and Symptoms: Inflammation of lungs with fluid-filled alveoli and bronchioles, typically severe. Can be lobar pneumonia affecting whole lobes.

    • Virulent Agents: Include Streptococcus pneumoniae (Pneumococcal pneumonia), Mycoplasma pneumoniae (Atypical pneumonia), Klebsiella pneumoniae, and others.

    • Pathogenesis: Involves inhalation or blood transmission; pneumonia can be fatal, particularly in adults.

  • Pneumococcal Pneumonia:

    • Signs and Symptoms: Fever, cough, chest pain, rapid breathing.

    • Pathogen: S. pneumoniae with virulence factors like a capsule and pneumolysin.

    • Diagnosis and Treatment: Treated with vancomycin; vaccination is preventive.

  • Tuberculosis (TB):

    • Pathogenesis: Mycobacterium tuberculosis remains viable in aerosol drops; causes primary, secondary, and disseminated TB.

    • Symptoms: Persistent cough, weight loss, fever; can lead to severe complications.

    • Diagnosis: Tuberculin skin test, chest X-ray, etc.

    • Treatment: Combination therapy with isoniazid, rifampin, etc.

Viral Diseases of the Respiratory System

  • Influenza:

    • Signs and Symptoms: Sudden fever, cough, body aches.

    • Pathogen: Influenza viruses (types A and B), which undergo antigenic drift and shift.

    • Diagnosis and Treatment: Often diagnosed via symptoms; antiviral medications available; yearly vaccination critical for prevention.

  • COVID-19:

    • Causative Agent: SARS-CoV-2, an emerging mutated coronavirus.

    • Signs and Symptoms: Persistent dry cough, fever, malaise, respiratory distress.

    • Transmission: Person-to-person via aerosols, droplets.

    • Treatment and Prevention: Supportive care, use of remdesivir, vaccines like Pfizer and Moderna now available.

  • Respiratory Syncytial Virus (RSV):

    • Signs and Symptoms: Fever, rapid breathing, cough in infants; mild in adults.

    • Pathogen: RSV, common childhood respiratory disease.

    • Treatment: Supportive and medication such as ribavirin; preventive measures critical.

    • Epidemiology: Most prevalent in late winter, affecting infants and the immunocompromised.

Mycoses of the Lower Respiratory System

  • Histoplasmosis:

    • Causative Agent: Histoplasma capsulatum.

    • Symptoms: Often mild unless in immunocompromised individuals.

    • Treatment: Managed with antifungal medications.

  • Pneumocystis Pneumonia:

    • Causative Agent: Pneumocystis jirovecii.

    • Symptoms: Difficulty breathing and hypoxia; common in AIDS patients.

    • Treatment: Trimethoprim and sulfamethoxazole, though prevention is challenging.