Unit 6 - Respiratory System Flashcards
What are the two membranes of the pleura?
- Parietal pleura
2. Visceral pleura (against the lungs)
What is the space called between the parietal and visceral pleura?
Pleural space
- contains a little fluid
What is each lung surrounded by?
Pleural cavity
What are the functions of the pleurae and pleural fluid (3)?
- Reduction of friction
- Creation of pressure gradient
- Compartmentalization
Regarding the atmospheric, pleural and alveolar pressures, which is greatest? which is lowest?
P(atm) > P(alv) > P(pl)
Why is it important that atmospheric pressure is greater than alveolar pressure?
So we can breathe in!
- pressure goes from HIGH to LOW
Why doesn’t the atmospheric pressure collapse the lungs?
Because of pleural pressure
- pleural pressure is lower than alveolar pressure and keeps the alveoli INFLATED
Why might breathing become impossible if there is inflammation of the pleura?
This would increase the pressure of the pleura, collapsing the alveoli
What is the benefit of compartmentalization of the lungs?
Helps to prevent/reduce the spread of infection
What does the upper respiratory tract consist of (3)?
- Nasopharynx
- Oropharynx
- Larynx
(Sometimes trachea is included too)
What does the lower respiratory tract consist of (4)?
- Trachea
- L and R primary bronchi
- Bronchioles
- Lungs
What is extrathoracic? (Where is it?)
Trachea and UP!
What is intrathoracic?
Where is it?
Bronchi and DOWN!
What are the 3 functions of the upper respiratory tract?
- Filters incoming air
- Humidifies incoming air
- Warms incoming air
Why is it important that air is humidified on the way INTO the lungs?
So that when you exhale air from the lungs, you don’t lose any more moisture
What does the tracheobronchial tress consist of?
- Trachea
- Bronchi
- Terminal bronchioles
- 23-28 branches of conducting tubes
How are conducting tubes different than alveoli?
Conducting tubes cannot exchange air between the blood and the airway
Where along the respiratory tract is smooth muscle present?
Wall of the bronchi and bronchioles
- amount of smooth muscles increases distally to the small bronchi then decreases and is eventually absent at the respiratory bronchioles
Where along the respiratory tract is cartilage present?
In the wall of the trachea and bronchi
- amount of cartilage decreases distally and disappears in the terminal bronchioles
What does smooth muscle in the wall of the bronchi and bronchioles help to control?
Airway conductance
What is the functional role of the smooth muscle around the airways?
Prevent inhalation of toxic, pollen, dust, etc.
- If there is an irritant in the air (smoke, dust, glass particles), if the airways don’t constrict, the person will suffer a lot of damage to the airways
What is the role of tracheobronchial epithelium?
Mucus-secreting ciliated epithelium
- Traps particles
- Cilia beat to expel trapped particles
What happens to tracheobronchial epithelium if you are a chronic smoker?
Metaplasia: epithelium
- stratified squamous epithelium (cannot produce mucus)
- higher risk of respiratory infections
- ability to filter is reduced
Where does gas exchange take place?
- Respiratory bronchioles
- Alveoli
What is the function of elastic and collagen fibers in alveoli?
Collagen = restricts stretch (can't over-inflate) Alveoli = ability to recoil
What happens to the connective tissue of alveoli in COPD (emphysema)?
Fibers are getting destroyed
- ability to prevent over-inflation is lost as well as ability to recoil
- alveoli get BIG!
Describe the relationship between alveoli and blood vessels.
When an alveoli is open, there is blood flow.
When an alveoli is closed, the blood vessels collapse (poor blood flow through lungs)
What facilitates gas exchange between the alveolar lumen and the blood?
Thin membrane
- intimate contact with a rich network of capillaries
What do Type 1 alveolar cells do? What do they look like?
Simple squamous epithelium (FLAT CELLS)
- facilitates diffusion of gases between bloodstream and alveoli)
What do Type 2 alveolar cells do? What do they look like?
Cuboidal (septal) cells
- secrete surfactant
What do alveolar macrophages do? What is another name for them?
Engulf foreign particles in the lungs
- also called dust cells
How thick is the endothelium of the capillaries and the alveolar epithelium combined?
- 1 - 1.5 MICRO meters
- allows for optimal diffusion of oxygen and carbon dioxide
How does pneumonia affect diffusion across the alveolar epithelium?
Fluid is in alveoli
- increases thickness of the membrane
- makes it harder for gases to diffuse across
What are the 4 normal respiratory functions?
- Alveolar ventilation
- Alveolar perfusion
- Alveolar-capillary diffusion
- Gas transport in circulation
What is ventilation?
The act of driving air in and out of the lungs
What is perfusion?
Adequate blood supply to the alveoli
What is diffusion?
Gas movement (down concentration gradients) from alveolar space to blood
Lung ventilation is dependent on which two things?
- Lung compliance
2. Action of respiratory muscles - (chest compliance)
What is chest compliance?
Allows the chest to be expanded
What is lung compliance?
Allows the lungs to be expanded
What are the two main muscles of ventilation?
- Diaphragm
2. External Intercostal muscles
What happens when the diaphragm contracts?
It pulls DOWNWARD
- increasing the volume of the chest
- pressure in chest decreases
What are the accessory muscles of inhalation (forced inhalation)?
- Scalene
2. Sternocleidomastoid
What are the accessory muscles of exhalation (forced exhalation)?
- Internal intercostals
2. Abdominal muscles
True or False:
During quiet breathing only inhalation requires energy
True
- muscles that assist in exhalation are only used during FORCED exhalation
Describe the mechanics of ventilation
- Contraction of diaphragm increase volume of thoracic cavity (pulled downwards)
- Contraction of external intercostals raises ribs
What is tidal volume?
Normal breath in and out
= approx 500 mL
Describe inspiratory reserve volume
Volume you can force IN at the end of the normal inhalation
= approx 3100 mL
Describe expiratory reserve volume
Volume that you can force OUT at the end of a normal exhalation
= approx 1100 mL
What is the residual volume?
Volume that is leftover inside the lungs after a forced exhalation
What is the vital capacity? How is it calculated?
Maximum capacity that you can inhale and exhale (tidal volume + inspiratory and expiratory reserve volumes)
What is the total lung capacity?
Maximum amount of air that the lungs can contain
What is the forced expiratory volume (FEV) used for?
Used to determine if a patient has an obstructive pulmonary disorder
How is FEV calculated (forced expiratory volume)? In a healthy adult, what should this number be?
% of vital capacity exhaled over time
- 75%-85% in 1 sec
How is the minute respiratory volume (MRV) calculated?
Amount of air drawn into the lungs in 1 minute
= Tidal volume x RR
What is the ratio between ventilation and perfusion?
1: 1
- maintained even if we are exercising
- IF there is a mismatch in the ration, there is a problem with ventilation or circulation
How easy it is for the lungs to inflate is dependent on what 3 things?
- Elastin and collagen fibres
- Water content
- Surface tension
What do elastin and collagen fibres do for the lungs?
Elastin = ability to recoil Collagen = prevent over inflation
What happens if there is too much water content in the lungs?
More water = harder to breathe
- it is easier to inflate a lung that is NOT filled with water
Why does water have a high surface tension?
Because of the hydrogen bonds between the molecules
What does surfactant do in the lungs? How?
Reduces surface tension
- acts as a mechanism to break apart some of the hydrogen bonds in H2O
Why is it that babies who are born prematurely have a hard time breathing?
Because surfactant is developed VERY late in pregnancy
- preemies don’t have a lot of it (or ANY!)
True or False:
Anything that increases the thickness of the membrane of the alveoli will decrease diffusion
True
- compromises gas exchange
What factors affect alveolar-capillary diffusion (3)?
- Permeability
- Surface area
- Concentration gradient of the gas
What is the normal partial pressure of oxygen in the blood?
80 mmHg (arterial blood)
What is the normal range for the amount of oxygen that is bound to hemoglobin (oxyhemoglobin levels)?
97 - 99%
- 95% saturation is acceptable in subjects with normal hemoglobin levels
What happens to the binding of oxygen to hemoglobin as partial pressure of oxygen increases?
Binding levels increase too
when partial pressure is low, oxygen saturation and binding is low
As partial pressure increases, will oxygen saturation level ALWAYS increase?
NO!
= there is a maximum level of oxygen saturation (100%)
What is easier to measure, oxygen saturation or partial pressure of oxygen?
Oxygen saturation
If the oxygen saturation level is 98%, what SHOULD the partial pressure of oxygen be?
80 mmHg
What is the normal partial pressure of carbon dioxide in arterial blood?
35 - 45 mmHg
What is the most common form that carbon dioxide is transported in, in the body?
Bicarbonate ion
Carbonic acid Bicarbonate ion + H+ ion
What happens to carbon dioxide levels as you breathe out?
- decrease levels of CO2
- decrease levels of carbonic acid, raising your blood pH
What is the function of CENTRAL chemoreceptors?
- measures partial pressure of CO2 and pH in cerebrospinal fluid
When do the central chemoreceptors increase respirations?
- When PCO2 increases OR
2. pH decreases (more acidic)
What happens if chemoreceptors are exposed to the same stimulus over an extended period of time?
They adapt
- become less sensitive to the stimulus
What is the function of PERIPHERAL chemoreceptors?
Measure partial pressure of oxygen in the arterial blood
When do periopheral chemoreceptors increase respirations?
When partial pressure of oxygen is < 60 mmHg
What is more influential in affecting/regulating breathing - CO2 or O2?
CO2 (central chemoreceptors)
- if there is an adaptation of central chemoreceptors, peripheral receptors will take over
Which receptors (central or peripheral) are FASTER but not as strong at regulating breathing?
Peripheral
