The Respiratory System Flashcards
What are the 4 main functions of the respiratory system?
- Ventilation
* The movement of air into and out of the lungs - External Respiration: Exchange of oxygen (O2) and carbon
dioxide (CO2) between the air in the lungs and the blood - Transport of O2 and CO2 in the blood
- Internal Respiration: Exchange of O2 and CO2 between the
blood and the tissues
What are the “other” functions of the respiratory system?
- Regulation of blood pH
- Altering blood CO2 levels
- PaCO2 35-45mmHg
- Voice production
- Air movement past the vocal cords
- Olfaction
- Airborne molecules are drawn into the nasal cavity
- Innate immunity
- Protects against certain microorganisms and other pathogens - preventing them
from entering the body and by removing them from respiratory surfaces
What are the parts of the respiratory system + their functions?
- Upper respiratory tract
- Nose and nasal cavity
- Air enters (also through mouth)
- Pharynx (throat)
- Larynx
- maintains an open airway
- protects the airway during swallowing (epiglottis)
- produces the voice
- Lower respiratory tract
- trachea
- bronchi
- lungs
What are the structures + functions in the lungs?
- Within the thoracic cavity
- 2 lungs
- separated by the mediastinum in which the
heart is situated - Each lung is divided into lobes
- Left lung – 2 lobes (upper and lower)
- Right lung – 3 lobes (upper, middle and lower)
- Heart sits within the ‘cardiac notch’
- so the left lung slightly narrower
- Each lung: Surrounded by
a pleural cavity - formed by 2 pleural
membranes - the visceral and parietal
pleurae - Passages branch
- Decrease in size
- Increase in number
What goes on in the conducting airways/zone?
- Strictly for ventilation
- The trachea (wind pipe)
- Cartilage
- splits into:
- Left and right bronchi
- When an airway divides it always
divides into 2 ( bifurcation)
What are the structures + functions of the bronchial tree?
- Left and right bronchi (one bronchus)
or primary bronchi divide - Secondary bronchi (in lobes of lung) -
divide - Tertiary bronchi - divide
- Bronchioles – divide (several times)
- Terminal bronchioles
- Top of tree
- Lots of cartilage some smooth muscle
- Keep airways open
- Bottom of tree
- Lots of smooth muscle less cartilage
- Change diameter of airways
What structure is in the respiratory zone + what is does?
- respiratory bronchioles
- (few alveoli) attached
- become
- alveolar ducts
- 2/3 alveolar sacs
- Alveoli
- Air filled sacs
- Membrane v elastic
- Expand / contract
- Surrounded by a capillary network to provide
efficient gas exchange - The respiratory membrane
- where gas exchange between the air and blood takes
place - Very very thin
What are the different types of alveoli + functions?
- Type I alveolar cells (95%) form
the alveolar wall, - permit gas exchange
- Type II alveolar cells secrete
surfactant - Defence
- Role in breathing and stabilises
alveoli (lowers surface tension) - Increases compliance
- Reduces Recoil of lungs
- Alveolar macrophages
- defence against foreign
particles/infectious
microorganisms that reach the
alveoli
What do cilia dO?
- Ciliary lining of the lower
respiratory tract - Beats upwards and drives the
debris-laden mucus to the
pharynx
What is ventilation composed of?
- Two Phases
- Inhalation (inspiration)
- Exhalation (expiration)
- Regulated by
- Changes in thoracic volume (drives)
- pressure changes
- Air flow is driven by
- the pressure difference between
- the atmosphere (barometric pressure)
- inside the lungs (intrapulmonary pressure)
Describe airflow and pressure changes in respiration?
- Changes in volume result in changes in
pressure
* As the volume of a container increases, the
pressure within the container decreases
* Same for lungs
* Respiratory muscles change volume of
thorax - Air flows from an area of higher
pressure to an area of lower pressure
* The greater the pressure difference, the
greater the rate of airflow
* Intra pulmonary / alveolar pressure
* Respiratory Muscles: change volume of
thoracic cavity
* Air flow into and out of lungs
What are the respiratory muscles?
- Diaphragm
- Intercostal muscles
- External
- Internal
- Scalene muscles
- Sternocleidomastoid
muscles - Pectoral muscles
- Abdominal muscles
What does the diaphragm do?
- 70 % ventilation
- Dome shaped
- Contracts
- Downwards and flattens
- (increasing thoracis cacvity)
- Relaxes
- Recoils upwards
- (reducing thoracic cavity)
- Only respiratory muscle working when lying flat and sleeping
Where are the intercostal muscles located + what do they do?
- Between ribs
- Two planes of muscular and tendinous fibres
occupying each intercostal space - Internal beneath external
- The external intercostal muscles
- slope downwards and forward
- Contract: ribs upwards and outward
- Elevates ribs and sternum
- The internal intercostal muscles
- Opposite direction
- Contract: lower ribs
- Stability
How do the muscles differ in inspiration? (quiet + forced breathing)
- Quiet breathing
- Diaphragm contracts
- External intercostals
- Contract
- Forced breathing
- Contract more forcefully
- Others contract
- Scalene muscles
- Sternocleidomastoid
- Pectoral muscles
Describe what happens in the active process of inspiration
signals from the respiratory centre in the medulla oblongata (brain stem) →contraction of the intercostal muscle and diaphragm leading to the diaphragm moving downward
option 1: transverse expansion of thoracic cavity
option 2: vertical expansion of thoracic cavity
↓ both lead to:
lung volume increases and the intra-alveolar pressure decreases
↓
air sucked in (inhalation)
What happens with the muscles in expiration: quiet + laboured?
- Quiet breathing
- Relatively passive
- Elastic tissue (lungs thorax)
- Lung recoils
- When…..
- Diaphragm relaxes
- Domes (decreases volume)
- External intercostals relax
- Downwards and inwards (decreases
volume) - Laboured exhalation
- Internal intercostals contract
- Abdominal muscles contract
Airflow and pressure changes: end of expiration
- Alveolar/ intra pulmonary pressure =
atmospheric pressure - No air movement
Airflow + pressure changes inspiration
- Increased thoracic volume
- Increased alveolar volume
- Decreased alveolar pressure
- Atmospheric pressure > alveolar
pressure - Air moves into lungs
Airflow + pressure changes end of inspiration
- Alveolar pressure = atmospheric
pressure - No air movement
Airflow + pressure changes expiration
- Decreased thoracic volume
- Decreased alveolar volume
- Increased alveolar /
intrapulmonary pressure - Alveolar pressure > atmospheric
pressure - Air moves out of lungs
Describe what pleural pressure is + what happens as it changes
- Pleural Pressure ( the pressure in the pleural cavity)
- Normally lower than alveolar pressure.
- Suction effect - fluid removal by the lymphatic system
- Negative pressure difference (lower pleural pressure
than alveolar pressure) keeps the alveoli expanded - Pulls the pleura away from the outside of the alveoli
- Pressure on the alveoli is lower
- Expansion is opposed by the tendency of the lungs to
recoil
*stops the lungs collapsing
What happens during exhalation? (outline)
- A passive event due to elastic recoil of the
lungs - Relaxation of diaphragm and external
intercostal muscles - During forced expiration, ONLY there is
contraction of abdominal, internal
intercostal (accessory muscles)
What are some details + functions of respiratory muscles (fun fact vibes)
- No inherent rhythm
- Generate tension due to rhythmic pattern of neuron-induced action
potentials activating them - Muscles attempt to overcome the resistance to airflow within the
airways - When at rest, the thorax assumes the FRC (Functional Residual capacity)
position
What is the way respiratory function is measured?
- Spirometry is the process of measuring volumes of air that move into
and out of the respiratory system - Measurements of the respiratory volumes can provide information
about the health of the lungs - Peak Flow
- Many more
- Static Lung Volumes
- Volumes/capacities
- Dynamic Lung Volumes
- How quickly air can be inspired/expired
What is meant by respiratory volumes + capacities?
- Respiratory volumes:
- measures of the amount of air
movement during different
portions of ventilation, - Respiratory capacities
- Sums of two or more respiratory
volumes. - The total volume of air
contained in the respiratory
system ranges from 4 to 6 L
What is tidal volume (VT)?
- the volume of gas expired/ inspired in one breathing cycle
*also known as ‘resting’ or quiet breathing
What is the inspiratory reserve volume?
- amount of air that can be inspired forcefully beyond the resting tidal volume
What is the expiratory reserve volume?
- amount of air that can be expired forcefully beyond the resting tidal volume
What is the residual volume?
*volume of air still remaining in the respiratory passages and lungs after maximum expiration
*without a residual volume, the lungs would completely collapse and the pressure required to generate inflation would be high
What is the total lung capacity?
- volume of gas in the lungs and airways at a position of full inspiration - therefore measuring how much air lungs can hold
*lung expansion is limited at a point which defines TLC
What is the vital capacity?
- total volume of gas that can be expired from the lungs from a position of full inspiration/ the total volume of gas that can be inspired from a position of residual volume
What is the inspiratory capacity?
*tidal volume plus inspiratory reserve volume
* amount of air a person can inspire maximally after a normal expiration
What is the functional residual capacity?
- volume of gas in the lungs and airways at the end of a tidal breath
- this is the point at which the inward pull of the lungs and the outward pull of the chest wall are in equilibrium
What are the limits of spirometry?
*cannot measure TLC,FRC,RV
What is peak expiratory flow (PEF)?
a measure of
how quickly you can blow air out of
your lungs.
* Measured in litres/minute (l/min)
What is PEF determined by?
- “Normal” will depend on age, height
and gender - Record in a peak flow diary and
compare against “best” - Can be used for diagnosis of asthma or
to predict oncoming asthma attack
What is the forced expiratory vital capacity?
Rate at which lung volume changes during direct measurement of the vital
capacity.
* FEV1 forced expiratory volume amount of air you can force from your lungs in one
second
* It is a simple and clinically important pulmonary test.
* The individual inspires maximally and then exhales maximally as rapidly as
possible into a spirometer.
* The spirometer records the volume of air expired per second.
* help identify conditions where vital capacity might not be affected but the
expiratory flow rate is reduced
* Asthma - contraction of the smooth muscle in the bronchioles increases the resistance
to airflow
* Emphysema - changes in the lung tissue result in the destruction of the alveolar walls,
collapse of the bronchioles, and decreased elasticity of the lung tissue.
* increase the resistance to airflow
key parameters for FEV1 - forced exhaled volume in 1 second?
Amount of air exhaled in 1 second
Affected by airway diameter
Predict ‘healthy’ values by age, gender and height
key parameters for FVC - forced vital capacity definition ?
Total amount of air that can be exhaled
FVC + Residual Volume = Lung Capacity
Predict ‘healthy’ values by age, gender and height
key parameters for FEV₁/FVC ratio?
Does not require tables, FEV1 values adjusted to FVC
Ratio <0.7 indicates airway obstruction
What is a part of basic gas exchange?
- Ventilation – we need to be able to get air to the alveoli for gases to
exchange - Perfusion – the circulatory system needs to ensure blood gets to the
alveolar
What surfaces does gas exchange occur in?
- Between air and blood occurs at the respiratory membranes
- Alveoli
- Some in the respiratory bronchioles and alveolar ducts
- Not in conducting zone - the bronchioles, bronchi, and trachea.
- The volume of these = anatomical dead space
- Pathology such as emphysema can increase this
What factors impact gas exchange + how?
- Thickness of the membrane
- O2 exchange affected before CO2
- O2 diffuses through the respiratory membrane less easily
than does CO2 - Total surface area of the respiratory membrane
- Reducing reduces gas exchange
- Partial pressure of gases across the membrane
- Pressure exerted by a specific gas in a mixture of gases
- PO2, PCO2
- Gases in the air dissolve in the liquid
- Until partial pressure in liquid = to the partial pressure in air
- Gases in liquid and air diffuse from areas of higher partial
pressure toward areas of lower partial pressure until equal
What is Fick’s law of diffusion calculation?
Vgas = kA/t x (p1 - p2)
describe step 1 in gas exchange
- Blood from tissues has a lower
Po2 and a higher Pco2 compared to
alveolar air
* O2 diffuses from the alveoli into
the pulmonary capillaries
* Po2 in the alveoli > in the pulmonary
capillaries
* CO2 diffuses from pulmonary
capillaries into the alveoli
* Pco2 pulmonary capillaries > alveoli
describe step 2 in gas exchange
- Venous ends of the capillaries:
* Pressures equal because of diffusion
* The blood carries O2 away by bulk flow
to the tissues where O2 is required
describe step 3 in gas exchange
- Mixing with deoxygenated blood =
lower PO2 than in capilaries
describe step 4 in gas exchange
- Oxygen diffuses out of the blood and
into the interstitial fluid then into cells
* Po2 in interstitial fluid < capillary
* Po2 in cells < than interstitial fluid
* Carbon dioxide diffuses from cells into
the interstitial fluid and from the
interstitial fluid into the blood
what is step 5 in gas exchange?
- Equilibrium
What are the 4 forms oxygen is stored as in the body?
- Oxygen is stored in the body in four forms -
- As a gas in the lungs
- Dissolved in tissue fluids
- As oxyhaemoglobin in blood
- As oxymyoglobin in muscle
Describe haemoglobin + bindings with O2
*Ability of hemoglobin to bind to O2
depends on the PO2
*oxy-Hb dissociation curve
*High PO2, haemoglobin binds to
O2
*Low PO2, hemoglobin releases
O2
*lungs, PO2 normally high
*hemoglobin holds as much O2 as it
can
*In the tissues, PO2 is lower
*hemoglobin releases O2
How is CO2 transported?
- Carbon dioxide diffuses from cells into the blood.
- Transported by:
1. 7% is transported as CO2 dissolved in the plasma
2. 23% is transported bound to blood proteins, primarily haemoglobin
3. 70% as bicarbonate ions
How is CO2 exchanged in tissues?
- CO2 diffuses into plasma and RBC
- Forms carbonic acid
- catalysed by carbonic anhydrase found
inside RBC and on capillary epithelium - promotes the uptake of CO2 by red
blood cells.
Describe CO2 gas exchange in the lungs
- Capillaries of the lungs
- the process is reversed
- CO2 diffuses from RBC to alveoli
- HCO3−dissociates to produce H2CO3
- The CO2 diffuses into the alveoli and is expired
How does CO2 have an effect on pH of blood?
- Carbon dioxide has an important effect on the pH of blood
- As CO2 levels increase, the blood pH decreases (becomes more acidic)
because CO2 reacts with H2O to form H2CO3 - The H+ that results from the dissociation of H2CO3 is responsible for
the decrease in pH. - Conversely, as blood levels of CO2 decline, the blood pH increases
(becomes less acidic, or more basic)
Describe the control of respiration
- Normal rate of breathing in adults
- Between 12 and 20 breaths per minute
- rate of breathing determined by the number of times respiratory muscles are
stimulated - Breathing is spontaneously initiated within the central nervous system (CNS)
- Medulla oblongata (brainstem)
- An increased depth of breathing results from
- stronger contractions of the respiratory muscles caused by recruitment of muscle
fibres - increased frequency of stimulation of muscle fibres
What 3 key functions must be performed for the control of respiration?
- The system must perform three key functions:
1. Maintain, through involuntary controls, a regular rhythmic breathing
pattern
2. Adjust the tidal volume (VT) and breathing frequency (fb) such that
alveolar ventilation is sufficient to meet the demands for gas exchange at cellular level
3. Adjust the breathing pattern to be consistent with other activities using
the same muscles, such as speech - Some conscious control
What are the nervous respiratory control centres?
Pons
* Pontine respiratory group
* Controls switches between inspiration
and expiration
Medulla
* Dorsal respiratory group (DRG)
* Diaphragm (inspiratory)
* Ventral respiratory group (VRG)
* Intercostals
* Abdominals
* Inspiratory and expiratory muscles
Describe what happens in the chemical control of breathing
- Level of CO2 (not O2), in the blood is the major driving force
- Even a small increase in the CO2 level (hypercapnia) results in a powerful urge to
breathe - Breathing is controlled so finely that the PaO2 and PaCO2 are kept within normal
limits - To achieve this, the system has a number of control pathways –
- The PCO2 is the principle pathway, controlling the rate and depth of breathing
on a breath-by-breath basis
What does an increase in H+ do?
increases ventilation as follows:
PaCO2 rises causing a
rapid increase in H+
ions. ↓
This causes pH to fall
(increase acidity)
↓
This causes the
central
chemoreceptors to
transmit a signal to
increase ventilation
↓
In doing so, PaCO2
and CO2 decrease and
when balance is
restored, ventilation
will decrease
What do chemoreceptors consist of?
Centrally
* Medulla oblongata
Peripherally
* Carotid bodies
* Aortic bodies
chemical control
- pH that accompanies an increase in
CO2 levels - Chemoreceptors
- Medulla oblongata
- chemoreceptors H+ concentration
- pH CO2
- If blood CO2 levels decrease, pH increase
→ medullary chemoreceptors signal a
decreased breathing rate → retains CO2
in the blood - More CO2 in the blood causes H+ levels to
increase, → blood pH to decrease to
normal levels - Carotid and Aortic bodies:
- pH, ↑ Co2, ↓O2
- Increased breathing
global inervation: nervous
Airways
* Innervated by the vagus nerve –
Parasympathetic
* Dominant
* Bronchoconstriction
* Innervated by the Sympathetic nerve chain
Respiratory Muscles
* Innervated by the intercostal (motor) nerves
* Phrenic nerve innervates the diaphragm
