DLA - Basics Respiratory Tract and Its Infections

Question 1

Which airway segments comprise the upper respiratory tract (URT) and the lower respiratory tract (LRT)?

Answer 1

URT - Nose/Mouth to larynx

LRT - Trachea down

Question 2

List the key differences between the URT and LRT that are relevant to pathology.

Answer 2

• URT - 33C-35C and LRT - 37C
• URT normally harbors an ecosystem of probiotic microflora. LRT is more sterile
• URT consists of cilliated, pseudostratified columnar cells. As you work your way into the LRT the epithelium becomes nonciliated
• URT consits of mucus and IgA secreting cells. As you work your way into the LRT the cells secrete primarily IgG and IgA

Question 3

Describe the ways in which the URT and LRT filter out particulate matter in the air. What happens to particulate matter that makes it to the alveolus?

Answer 3

• >10 microns - captured by nasal hairs
• >5 microns - captured by mucus
• 2-5 microns - likely captured by mucus can make it all the way to the alveolus
• <2 microns - likely to make to the alveolus but can be captured by mucus

Particulate matter that makes it to the alvelus is digested by alveolar macrophages.

Question 4

What are the three primary secretory substances in the URT and LRT that protect against infections? How do they do this?

Answer 4

• Secretory IgA (S-IgA) - IgA recognizes, binds to, and immobilizes pathogens until they can be destroyed
• Lactoferrin - primary purpose is to sequester free iron
• Lysozyme - has β-lactamase activity

Question 5

Describe the important functions URT probiotic bacteria serve.

Answer 5

• They occupy the receptors pathogens would use to infect the URT
• They secrete substances that have antimicrobial activity against microbes similar to themselves. For example, a harmless streptococcus probiotic bacteria may secrete substances that can kill harmful streptococcus bacteria

Question 6

What are the five primary portals of entry for infectious agents?

Answer 6

1. RT
2. GIT
3. UGT (urogenital tract)
4. Skin
5. Placenta

Question 7

What pathogen causes infectious pharyngitis?

Answer 7

Many different pathogens cause this. The point of this question was to drive home the point that diseases can be caused by many different pathogens.

Question 8

What 7 families of pathogens cause the most RT infections? List in order. What types of genomes do these viruses have? Are these viruses relatively small or large?

Answer 8

• Adenoviruses - linear dsDNA - small
• Rhinoviruses - (+) RNA - small
• Coronaviruses - (+) RNA - large
• HPIV (human parainfluenza virus) - (-) RNA - large
• RSV (respiratory syncytial virus) - (-) RNA - large
• Influenza - segmented RNA - medium
• Picornaviruses - (+) RNA - small