Lecture 33 - Respiratory System Flashcards
What are the 2 processes of respiration?
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
Which respiration is the primary function of the respiratory system?
External respiration - airway allow air to reach gas exchange surfaces in lungs. Inhaled air is conditioned
O2 in, CO2 out
What is pulmonary ventilation?
It’s external respiration, aka breathing. It physically moves air into and out of the lungs
Function of respiratory system, pulmonary circuit, and thoracic and abdominal muscles (and thoracic cage)
Respiratory - series of air-filled tubes and spaces
Pulmonary - brings blood to lungs for oxygenation
Thoracic and abdominal - produce movements for ventilation
What are the secondary functions of the respiratory system?
- Protective barrier - keeps foreign substances in the air from entering the body
- Sensory - neurons in the nasal vacity detect volatile odorants
- Communication - airflow is manipulated to allow for production of speech and other sounds
Name 3 upper tract functions of the respiratory system
- Air conditioning (and conduction)
- Olfaction
- Sound articulation
Name 3 lower tract functions of the respiratory system
- Air conduction
- Phonation
- (External) respiration
What are the 2 compartments of the lower respiratory tract and what are their portions?
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
Function of the respiratory mucosa
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
Where do the respiratory epithelium no longer possess mucous or ciliated cells? What replaces it instead?
Terminal bronchioles
Mobile macrophages (a type of phagocytic WBC) take over the protective functions performed by mucus
What are the 2 types of epithelium that are specialized for rapid gas exchange?
- Type I alveolar cells - a single thin (squamous) layer of cells that lines the inner surface of the alveoli
- Type II alveolar cells - secrete surfactant, a detergent which reduces the surface tension at the air-water interface
Where does external respiration only occur?
In the alveoli
The rest of the respiratory tract is for pathways to flow within
When does gas exchange occur?
It only occurs when air is in close proximity with capillaries of the pulmonary circuit
How does the body constantly get fresh air to reach the alveoli?
The body evolved a pump that creates pressure gradients to move air for pulmonary ventilation
What is the pleura and how is it stuck to the thoracic wall?
It is a double-layered membrane. The lungs are stuck to the thoracic wall by the surface tension of fluid within the pleural cavity
What is the function of the pleural cavity in terms of pressure gradients?
Changes in the size of the pleural cavity create pressure gradients which drive airflow into and out of the lungs
Describe inhalation and exhalation in terms of pressure gradient
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
Which muscles are active during quiet breathing?
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
What occurs during active (forced) breathing?
Accessory inspiratory and expiratory muscles are recruited to amplify movements - they increase the speed and magnitude of thoracic cage movements
What does respiratory movement depend on?
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
What does the respiratory cycle depend on?
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
Explain spirometry
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
What is tidal volume and what is resting tidal volume?
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
What is inspiratory capacity and inspiratory reserve?
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
What is expiratory reserve and vital capacity?
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
What is the residual volume?
It is what remains after maximal exhalation - it is a considerable fraction of total lung capacity
This CANNOT be measured directly with spirometry
