Lecture 33 - Respiratory System

Question 1

What are the 2 processes of respiration?

Answer 1

External respiration - the exchange of oxygen and CO2 between blood, lung tissue, and the external environment

Internal respiration - the exchange of oxygen and CO2 between blood and other body tissues

Question 2

Which respiration is the primary function of the respiratory system?

Answer 2

External respiration - airway allow air to reach gas exchange surfaces in lungs. Inhaled air is conditioned

O2 in, CO2 out

Question 3

What is pulmonary ventilation?

Answer 3

It’s external respiration, aka breathing. It physically moves air into and out of the lungs

Question 4

Function of respiratory system, pulmonary circuit, and thoracic and abdominal muscles (and thoracic cage)

Answer 4

Respiratory - series of air-filled tubes and spaces

Pulmonary - brings blood to lungs for oxygenation

Thoracic and abdominal - produce movements for ventilation

Question 5

What are the secondary functions of the respiratory system?

Answer 5

1. Protective barrier - keeps foreign substances in the air from entering the body
2. Sensory - neurons in the nasal vacity detect volatile odorants
3. Communication - airflow is manipulated to allow for production of speech and other sounds

Question 6

Name 3 upper tract functions of the respiratory system

Answer 6

1. Air conditioning (and conduction)
2. Olfaction
3. Sound articulation

Question 7

Name 3 lower tract functions of the respiratory system

Answer 7

1. Air conduction
2. Phonation
3. (External) respiration

Question 8

What are the 2 compartments of the lower respiratory tract and what are their portions?

Answer 8

Conducting portions:
- Larynx
- Trachea
- Bronchi (3 types)
- Bronchioles (3 types)

Respiratory portions:
- Pulmonary lobules (respiratory bronchioles and alveolar sacs)
- Alveolus - a capillary-wrapped gas exchange structure

Question 9

Function of the respiratory mucosa

Answer 9

It’s a mucous membrane that covers the respiratory tract and conditions/filters air by trapping particles and pathogens. Cilia motion constantly sweep secreted mucous towards the pharynx

Question 10

Where do the respiratory epithelium no longer possess mucous or ciliated cells? What replaces it instead?

Answer 10

Terminal bronchioles

Mobile macrophages (a type of phagocytic WBC) take over the protective functions performed by mucus

Question 11

What are the 2 types of epithelium that are specialized for rapid gas exchange?

Answer 11

1. Type I alveolar cells - a single thin (squamous) layer of cells that lines the inner surface of the alveoli
2. Type II alveolar cells - secrete surfactant, a detergent which reduces the surface tension at the air-water interface

Question 12

Where does external respiration only occur?

Answer 12

In the alveoli

The rest of the respiratory tract is for pathways to flow within

Question 13

When does gas exchange occur?

Answer 13

It only occurs when air is in close proximity with capillaries of the pulmonary circuit

Question 14

How does the body constantly get fresh air to reach the alveoli?

Answer 14

The body evolved a pump that creates pressure gradients to move air for pulmonary ventilation

Question 15

What is the pleura and how is it stuck to the thoracic wall?

Answer 15

It is a double-layered membrane. The lungs are stuck to the thoracic wall by the surface tension of fluid within the pleural cavity

Question 16

What is the function of the pleural cavity in terms of pressure gradients?

Answer 16

Changes in the size of the pleural cavity create pressure gradients which drive airflow into and out of the lungs

Question 17

Describe inhalation and exhalation in terms of pressure gradient

Answer 17

Inhalation - movements of inspiratory muscles expand the lungs, creating a negative pressure gradient

P_outside > P_inside; pressure inside decreases, so air flows in

Exhalation - when the muscles relax, the pressure gradient and air flow reverse

P_outside < P_inside; pressure inside increases, so air flows out

Question 18

Which muscles are active during quiet breathing?

Answer 18

Only primary inspiratory muscles are active. It allows:

• The ribs to swing up and out through the contraction of the external intercostal muscles
• The diaphragm to depress the floor of the thoracic cavity

NOTE: exhalation is passive - it involves the relaxation of inspiratory muscles and the elastic recoil of the thoracic cavity

Question 19

What occurs during active (forced) breathing?

Answer 19

Accessory inspiratory and expiratory muscles are recruited to amplify movements - they increase the speed and magnitude of thoracic cage movements

Question 20

What does respiratory movement depend on?

Answer 20

Skeletal muscles, therefore, on somatic motor neurons

Phrenic motor neurons (found in C3-C5) send their axons in the phrenic nerve and innervate the myofibres of the diaphragm

Question 21

What does the respiratory cycle depend on?

Answer 21

Neural activity generated within the medulla

The rate and pattern of breathing movements is generated by activity in respiratory centres in the medulla

No medullary respiratory center activity = no breathing

Question 22

Explain spirometry

Answer 22

It measures airflow in and out of the respiratory system

Measurements:
1. Volume of air moving into or out of the respiratory system
2. How fast that air is moving

It involves periods of quiet breathing and a forceful inhalation and exhalation

Question 23

What is tidal volume and what is resting tidal volume?

Answer 23

It is the air moving in a single quiet breath and it is a small fraction of the total volume of air in the lungs. Resting tidal volume is a quiet breath that moves ~500 mL of air into and then out of the lungs

Question 24

What is inspiratory capacity and inspiratory reserve?

Answer 24

They both relate to the maximum volume of air that can be breathed into the lungs

These measurements are made when a subject is asked to breathe in as deeply as possible

Question 25

What is expiratory reserve and vital capacity?

Answer 25

They both relate to the amount of air that can be breathed out in a maximal exhalation

These measurements are made when a subject is asked to breathe out as completely as possible

Question 26

What is the residual volume?

Answer 26

It is what remains after maximal exhalation - it is a considerable fraction of total lung capacity

This CANNOT be measured directly with spirometry