Respiratory Functions

Question 1

Primary function of respiratory system

Answer 1

-absorb oxygen
- remove CO2

Question 2

Secondary functions of respiratory system

Answer 2

-phonation (sound)
-olfaction
- acid-base balance
-humidification and temperature control
- pulmonary fluid exchange
- pulmonary defense

Question 3

Key Steps of gas exchange

Answer 3

1. Oxygen enters the body through conducting airway to alveoli
2. Deoxygenated blood enters the lung from pulmonary artery
3. CO2 and O2 exchange at the pulmonary capillaries
4. CO2 is exhaled, oxygenated blood in the pulmonary vein enters the left side of the heart then into systemic circulation
5. O2 diffuse into peripheral tissues for metabolism, and CO2 diffuses out of peripheral tissues from metabolism

Question 4

How does gas move?

Answer 4

Simple diffusion from high to low concentrations drive gas movement
- Use partial pressures (P CO2 or P O2)

Question 5

What is partial pressure referring to in respiration?

Answer 5

The amount of gas dissolved in plasma (Does not include any amount within hemoglobin)
- Most O2 is on hemoglobin so actual content is higher than what appears

Question 6

Pressure difference of O2 and CO2

Answer 6

• Oxygen pressure differences between different areas (alveolus, arteries, veins, tissues) is much higher than that of CO2
• BUT CO2 has a 20x higher solubility which increases diffusion rate (and is important in controlling acid and bases

**Therefore both diffuse in similar manner even though greater differences occur

Question 7

Acid-base regulation in respiration

Answer 7

• Regulated through control of CO2
• CO2 changes do not change dramatically, but slight changes are detected by chemoreceptors and leveled out through changes in respiration rate (neural control)

Question 8

Increase in ventilation

Answer 8

• Increase in CO2 expiration, results in left shift and an increase in pH
• Alkalosis

Question 9

Decrease in ventilation

Answer 9

• Decrease in CO2 expiration, results in right shift and a decrease in pH
• Acidosis

Question 10

Humidification and temperature control (through respiration)

Answer 10

Mucosa of the nose, nasal turbinate, nasopharynx have large surface area for airflow
- Leads to air being humidified by evaporation of water from epithelial surface and warmed by the time it reaches the trachea towards the alveoli

Question 11

Purpose of humidification and temperature control of air

Answer 11

Protects alveoli from damage effects of cold and/or dry air

Question 12

Pulmonary fluid and its function

Answer 12

• Fluid in the interstitial space and inside the alveoli that comes from the capillaries

Function:
- protective barrier and prevents alveoli desiccation
- Environment for alveolar macrophages
- Creates surface tension leading to elasticity

Question 13

Pulmonary fluid exchange

Answer 13

Hydrostatic pressure (typically driving fluid out) and osmotic pressure (typically drawing fluid in) leads to a +1 net pressure in capillary and fluid is pushed out into interstitial space by lymphatic pump and recirculated

• If no net pressure in the alveoli, then the excess fluid moves into the interstitial fluid and goes through the lymphatic pump BUT a small amount will evaporate into the alveoli to maintain moisture

Question 14

Pathologies related to pulmonary fluid exchange

Answer 14

1. Heart failure resulting in increases blood volume in capillary, increased hydrostatic pressure and excess fluid building up in lymphatics leading to pulmonary edema
   - Edema increases gas diffusion distance and blocks gas exchange… resulting in respiratory acidosis
2. Alveoli inflammation (pneumonia) can cause fluid buildup inside the alveoli that can cause edema and blocked gas exchange

Question 15

Pulmonary defense

Answer 15

• Animals are constantly exposed to foreign respiratory particulates (dust, pollen, fungal pores, bacteria) that deposit themselves at various different locations of the respiratory tract
• Defense includes mucociliary clearance system and macrophage defense

Question 16

Deposition methods

Answer 16

• Impaction
• Sedimentation
• Brownian movement
• Interception

Question 17

Impaction

Answer 17

• Deposit based on impact (fast)
• Particles greater than 10 micrometers: deposit in nasal passages
• Particles between 2-10 micrometers: nasal pharynx, trachea, bronchi

Question 18

Sedimentation

Answer 18

• Deposit small particles at low speeds, based on gravity
• Particles between 0.2-2 micrometers: deposit in distal airways

Question 19

Brownian movement

Answer 19

• Deposit nanoparticles by random motion
• Particles less than 0.2 micrometers
• Deposit in smaller airways and alveoli

Question 20

Interception

Answer 20

• Elongated particles; intercept at distal tip
• Slow movement
• Eg. Asbestos

Question 21

Physiological response to foreign particulates

Answer 21

1. Mucociliary clearance- includes sneezing (nose), coughing (pharynx, trachea, bronchi, bronchioles), bronchoconstriction (bronchi, bronchioles)
2. Alveolar macrophages

Question 22

Purpose of sneezing, coughing, bronchoconstriction and alveolar macrophages

Answer 22

• Expulsion (sneezing, coughing)
• Minimize airflow (bronchoconstriction)
• Clearance (macrophages)

Question 23

Where are mucociliary clearance found?

Answer 23

Found in conducting airway to trap and remove inhaled particulate

Question 24

Key components of mucociliary clearance

Answer 24

• Cilia
• Mucous gel layer
• Mucous sol layer (periciliary fluid)

Question 25

Mucociliary escalator

Answer 25

Particulates are trapped on the mucus gel layer whereas the watery periciliary fluid (sol layer) allows the cilia to establish an upward flow to clear particulates from the lung through the pharynx

• ~250 cilia/cell @ 1000 strokes/min
• Mucous is expelled or swallowed

Question 26

Pneumonia risk in horses

Answer 26

Gravity plays a large role in large animals at speeding up the mucociliary clearance
- If a horse is prevented from lowering its head, the rate of the clearance from the lungs decreases which leads to an increased risk of bacteria in the trachea and chances of developing pneumonia

**Reason why long distance transport is the greatest predisposing risk factor for pneumonia development in horses

Question 27

Alveolar macrophages

Answer 27

First line of defence in terminal bronchioles and alveoli (for the particles that escaped mucociliary clearance)
- Phagocytosis by resident macrophages (enzymatic digestion and breakdown into small microparticles). Then absorbed into the lymphatic system and cleared.

Macrophages can also migrate to conducting airways to be cleared via mucociliary clearance