Overview of Respiratory Tract

Overview of Respiratory Tract

• Respiratory tract encompasses both the upper and lower respiratory tracts
• Upper respiratory tract (URT) includes the pharynx and epiglottis
• Lower respiratory tract (LRT) includes the trachea, bronchi, and lungs

Innate Defenses

• Respiratory tract includes innate defenses to combat pathogens
• Mucous membranes, including goblet cells, cilia, and the mucociliary escalator, trap and expel pathogens
• Mucosa-associated lymphoid tissue (MALT), including adenoids and tonsils, provides immune protection
• Alveolar macrophages engulf and destroy foreign invaders
• Normal microbiota competes with pathogenic microbes, limiting their colonization

Respiratory Tract Microbiota

• Similar to skin and mouth flora, may include opportunistic pathogens in low numbers
• Microbiota varies from person to person, influenced by factors like immune status and antibiotic use

Common Cold

• Caused by over 200 different viruses, including rhinoviruses and coronaviruses (40-60%)
• Rhinoviruses and coronaviruses are the most common culprits
• Transmission occurs through respiratory droplets and contact with fomites
• Symptoms include runny nose, sneezing, fatigue, coughing, stridor, dyspnea
• Severe infections can lead to pneumonia, inflammation of the alveoli
• Diagnosis is based on clinical symptoms or nasal/nasopharyngeal swabs
• Treatment is primarily supportive including rest, fluids, and over-the-counter medications
• RSV and ADV vaccines help protect against some forms of the common cold

RSV

• Respiratory syncytial virus (RSV) is an RNA, enveloped virus
• Can cause severe infections, especially in infants and the elderly
• Can lead to bronchiolitis, pneumonia, and respiratory distress
• Diagnosis is typically based on clinical presentation and nasal swab
• Treatment includes supportive care, oxygen therapy, and respiratory support in severe cases

Respiratory System Overview

• The respiratory tract is divided into the upper respiratory tract (URT) and the lower respiratory tract (LRT).
• The URT includes the pharynx and epiglottis.
• The LRT includes the trachea, bronchi, bronchioles, and alveoli.

Innate Defenses of the Respiratory Tract

• The respiratory tract has several innate defenses, including:
  • Mucous membranes: Goblet cells secrete mucus, which traps pathogens.
  • Ciliated epithelial cells: These cells beat rhythmically to move mucus and trapped pathogens up the respiratory tract (mucociliary escalator).
  • Mucosa-associated lymphoid tissue (MALT): This tissue includes adenoids and tonsils, which are important for immune responses.
  • Alveolar macrophages: These cells reside in the alveoli and phagocytize pathogens.
  • Normal microbiota: The presence of normal microbiota helps to prevent the growth of harmful pathogens.

Respiratory Tract Microbiota

• The normal microbiota of the respiratory tract varies between individuals, depending on factors such as immune status, antibiotic use, and smoking.
• The upper respiratory tract and mouth contain similar microbiota to the skin.
• The lower respiratory tract is usually sterile, with transient microbes only.

Common Cold

• The common cold is caused by over 200 different viruses, including rhinoviruses, coronaviruses (40-60%), HPIV, RSV, and ADV.
• Transmission occurs through respiratory droplets and contact with fomites.
• Symptoms include runny nose, sneezing, fatigue, coughing, stridor, dyspnea.
• Severe infections can lead to pneumonia, which is inflammation of the alveoli.
• Diagnosis is based on clinical symptoms and can be confirmed with a nasal or nasopharyngeal swab using a NAAT (Nucleic Acid Amplification Test).
• Treatment is supportive care, aiming to manage symptoms.
• There are vaccines available for RSV and ADV.

RSV

• Respiratory Syncytial Virus (RSV) is an RNA, enveloped virus.
• It can cause more serious infections in children and infants.
• It causes bronchiolitis and pneumonia.