16. Intro to Respiratory System

Question 1

What are the functions of the respiratory system?

What are the contents of the upper and lower respiratory tract?

Answer 1

Gaseous exchange, acid-base equilibrium, phonation, warming/humidification/filtration of gas (concha bones make air spin), defence (airbourne pathogens)

URT: oropharynx and larynx (non-respiratory)

LRT: 1) conducting airways (trachea and bronchi, non-respiratory) 2) gas exchange tissue (alveoli and terminal bronchioles, respiratory)

Question 2

How many times does the airway tree divide?

Which are the conducting airways, and the respiratory zone?

Roughly how many alveolar ducts are there per lung, and what do they divide to?

Where does gas exchange occur?

How many albeoli in the lungs?

Answer 2

23

CA: first 16, RZ: last 7

8 million, divide to terminal alveolar sacs

Alveolar sacs, ducts and bronchioles

1 billion

Question 3

What happens to the inward velocity of gas during inspiration as you go down the respiratory tree?

What is the volume of the conducting airways?

Define ‘dead space gas’.

What type of epithelial cell is present in the conducting airways?

Answer 3

Becomes very small.

150-200ml

Exhale - have to breathe out volume of conducting airways first before you exhale alveolar gas - this gas = DSG.

Ciliated pseudostratified columnar epithelium

Question 4

Label A-D in a conducting airway.

Answer 4

A: columnar cells

B: cilia

C: goblet cell

D: mucus

NB. in lower condicting airways (bronchioles), simple epithelium only. Epithelium EXCEPT ALVEOLAR is covered with mucus

Question 5

Describe the 2 types of epithelial cells.

What types of mobile cells are also present in high proportions in the alveoli?

Answer 5

Type 1 pneumatocytes: 90%, simple squamous

Type 2 pneumatocytes: 10%, cuboidal cells, secrete surfactant

Macrophages (“dust cells”)

Question 6

Label A-C in the lungs

Answer 6

A: ciliated cell

B: goblet cell

C: connective tissue

Question 7

What is surfactant?

Answer 7

Alveoli lined with water and dissolved surfactant = decreases surface tension and stops alveoli collapsing during exhalation (air pressure decreases)

Question 8

Label A-C in the alveoli

Answer 8

A: Type 1 pneumatocyte

B: Type 2 pneumatocyte

C: Alveolar macrophage (b/c mucus would compromise gas exchange, so no mucus but macrophages instead)

Question 9

What is the formular for partial pressure of gas A?

What is the pO₂ in dry inspired air?

To calculate pO₂ of alveolar gas, what do you need to allow for and why?

What are the rough values of pO₂ and pCO₂ in the alveoli?

Answer 9

pA = total pressure in gas mixture x fractional concentration of A

Total pressure is atm (760mmHg) and fractional conc is 21%, so pO₂ = 760 x 0.21 = 160mmHg

Account for H₂O vapour in inspiration (44mmHg) b/c it decreases partial pressures of other gases, making pO₂ = 155mmHg

pO₂: 100mmHg pCO₂: 40mmHg

Question 10

What are rough values for A and B?

Answer 10

A: pO₂: 40 pCO₂: 46

B: pO₂: 95 pCO₂: 40

Question 11

What happens to pO₂ at altitude and why?

Answer 11

Decreases because:

respiratory rate/depth increases; O₂ fraction stays the same but total pressure decreases

Question 12

What are the 3 most common respiratory diseases?

List some others.

List some infectious respiratory diseases.

Answer 12

Bronchitis, emphysema, pneumonia (fluid build up in alveoli so O₂ diffusion compromised)

Asthma, COPD (chronic bronchitis + emphysema), tumors, pulmonary fibrosis, occupational lung disease, disorders of chest wall, pleura and diaphragm e.g. pneumothorax etc.

Common cold (acute coryza), influenza, pneumonia, pulmonary TB

Question 13

What percentage of all acute illnesses are acute viral respiratory illnesses?

What percentage of GP consultations are respiratory?

What 3 factors are interlinked and affect respiratory disease?

Answer 13

1/2 or more e.g. adenovirus, rhinovirus

>30%

social (housing, smoking, travel, drugs), environmental (pollution, dust mites), occupational (allergies, chemical exposure)