Topic 2.1: Ventilatory System Flashcards
2.1.1
List the principal structures of the ventilatory system.
The Nose
- Nostrils lined with coarse ‘guard hairs’ that block dust, insects etc entering the nose.
- Ensure the air makes contact with the mucous layer of the nasal cavity
- Allows the nose to warm, humidify (moisten) and cleanse the air
Pharynx
- Located at the back of the nasal cavity involved in both respiration and digestion
- Made up of 3 parts
- Continues to warm and filter air
Larynx
- The voice box situated at the top of the trachea.
- Continues to warm and filter air.
- The epiglottis blocks the trachea during swallowing, preventing food entry and halting breathing momentarily
Trachea
- Delivers air into the lungs
- The cartilaginous trachea, branches into the two main bronchi
Bronchi
Branches delivering air into each of the lungs (one bronchus into each lung)
Bronchioles
- Bronchioles further divide delivering air to alveolar ducts
- Cilia carry mucus with trapped dust to back of the throat where it is swallowed.
Alveoli
Responsible for gaseous exchange which takes place between alveoli and pulmonary capillaries.
Diaphragm
- Primary muscle used in respiration
- Dome-shaped muscle is located just below the lungs and heart
Outline the functions of the conducting airways
- Low resistance pathway for airflow
- Defence against chemicals, foreign and harmful substances
- Warming and moistening the air
Pulmonary ventilation
Inflow and outflow of air between the atmosphere and the lungs (also called breathing)
Total lung capacity
Total amount of air that the lungs can
hold
TV + IRV + ERV + RV
Tidal volume
volume of air breathed in and out in any one breath
Expiratory reserve volume
The reserve amount that can be exhaled beyond what is normal
Inspiratory reserve volume
additional amount of air that can be inhaled after a normal inhalation
Residual volume
volume of air still contained in the lungs after a maximal exhalation
Vital Capacity
max. amount of air that can be exhale after a max. inhale
VT + IRV + ERV
2.1.5. Describe nervous and chemical control of ventilation during exercise.
- Ventilation increase as a result of increase on blood activity level (low pH) due to increase CO2 content of blood detected by the respiratory center.
- Increase rate and depth of ventilation
- Neural control of ventilation include lung stretch receptors, muscle proprioreceptors and chemoreceptors.
2.1.6. Outline the role of hemoglobin in oxygen transportation.
- Most (98.5%) of oxygen in the blood is transported by hemoglobin as oxyhemoglobin within red blood cells
- Transports oxygen from the lungs to the rest of the body
2.1.7. Explain the process of gaseous exchange at the alveoli.
- We inhale oxygen and exhale CO2
- Oxygen enters into our lungs and into alveoli
- Alveoli wall is very thin so gas can enter and exit
- Oxygen diffuses from the site of higher pressure (alveolar air) to the site of lower pressure (capillary blood)
- CO2 from blood diffuses from site of higher pressure to lower pressure
- Oxygen binds with red blood cell by hemoglobin = oxyhemoglobin
Outline the mechanics of the diaphragm when breathing
- Prime mover of pulmonary ventilation
- In a relaxed state, bulges upward pressing against the base of the lungs, making the thoracic cavity smaller
- When contracts, enlarges the thoracic cavity and lungs creating an inflow of air
- When relaxes, bulges upward again, compresses the lungs and expels the air
- Responsible for 2/3 of airflow
Describe the role of the Intercostal Muscles during respiration.
There are two intercostal muscles:
- External and Internal
External Intercostal Muscles:
- Contract during inhalation - increases the width of the chest cavity. More volume = less pressure. Result in airflow into the lungs.
Internal Intercostal Muscles:
- Don’t contract during normal expiration.
- Only contract during forced exhilation or exercise to push air out faster
Name the accessory muscles during exercise (inspiration)
Small muscles attached to ribs and sternum that aid in increasing thoracic volume.
During max. efforts:
- trapezius, back, neck extensors contract to increase thoracic cavity
Name the accessory muscles during exercise (expiration)
- Internal Intercostal muscles and abdominals muscles contract to force air out of the lungs.
- Abdominal muscles pull the ribs down and force the diaphragm upward pushing air out.
What is the relationship between volume and pressure in the thoracic cavity?
Inverse relationship:
- Volume increase, pressure decrease
- Volume decrease, pressure increase
Inspiration Mechanism at Rest
- External Intercostal Muscles contract –> increases the width of the chest cavity
- Diaphragm contracts at the same time pulling the muscle downwards
- Both actions increase the volume capacity of the lungs, decreasing the air pressure inside the lungs.
- Atmospheric air is forced into the lungs equalizing air pressure
Expiration Mechanism at Rest
- Diaphragm and external intercostal muscles relax to their original position.
- Volume is decreased, air pressure inside the lungs is increased and air is forced out to equalize pressure
Explain the difference between hyperventilation and hypoventilation in relation to PO2 and PCO2
What causes ventilation to increase during exercise?
A. High pH
B. Decreased blood acidity level
C. Increased carbon dioxide level
D. Lower carbon dioxide level
c.
Increased carbon dioxide level
How does the Respiratory Centre know when to increase the breathing depth and rate?
If co2 levels in the blood are too high (low pH/high acidity) –> brain’s respiratory center signals the respiratory muscles to increase breathing rate to expel excess co2
Muscle proprioreceptors
Sensors that tell CNS about joint angles, muscle stretch, and body balance
Chemoreceptors
Detect changes in blood acidity levels (pH), carbon dioxide (pCO2) and oxygen (O2) content of the blood
Lung stretch receptors
Prevents overexpansion by signaling the respiratory center to stop inspiration and start expiration.
