respiratory system Flashcards
why do we breathe?
- maintain blood gas homeostasis
- ensure CO2 and O2 levels in blood are optimal to fuel body
- get rid of waste
- coupled with cellular respiration
what is the partial pressure of oxygen at rest?
PO2=100+-2mmHg
what is the partial pressure of CO2 at rest?
PCO2=40+-2mmHg
what are the two zones that the respiratory system can be split into?
- conducting zones
- respiratory zones
conducting zones
- nose
- pharynx
- larynx
- trachea
- bronchi
- bronchioles
- terminal bronchioles
what type of epithelium do the conducting zones have?
respiratory epithelium = ciliated pseudostratified columnar epithelium
respiratory zone
- respiratory bronchioles
- alveolar ducts
- alveaolar sacs
- alveoli
what type of epithelium do respiratory zones have?
simple squamous epithelium
what muscle is responsible for breathing at rest?
the diaphragm
what are the mechanics of inhaling during quiet breathing / breathing at rest?
- inspiration part is an active process
- diaphragm contracts downward
allows lungs to expand & push abdominal contents downwards - external intercostal muscles pull the ribs outward and upwards -> helps increase space in thoracic cage -> gives lungs more space to expand
what are the mechanics of exhaling during quiet breathing / breathing at rest?
- this is a passive process -> expiration is driven by the elastic recoil of the muscles
- this recoil causes the muscles to force air (CO2) back out of lungs and causes lungs to deflate
- this reduces the space within the thoracic cage & it returns to its resting state
how does exercise affect respiration?
- greater contraction of the diaphragm and the external intercostal muscles
- other accessory muscles also activated during this time
- active: these muscles are activated to help with expiration and the internal intercostal muscles oppose external intercostals
- do this by pushing the ribs downwards and inwards
what is strenuous breathing?
respiration during things such as exercise
both inspiration and expiration are active
by what & where is pulmonary surfacant produced?
by type II epithelial cells
in alveoli
what is the purpose of pulmonary surfacant?
- helps line the surfaces of the alveoli to reduce surface tension
- allows alveoli in lungs to easily expand and deflate as needed for respiration
what happens in the absensce of pulmonary surfacant?
- alveoli struggle to resist surface tension and cannot re-expand easily after expiration
what is oxygen saturation? SaO2
- amout of oxygen molecules bound to haemoglobin relative to the max amount that they can bind
- each Hb can bind 4 O2
how can you measure O2 saturation?
using a pulse oximeter
which nerve(s) innervates the diaphragm?
phrenic nerve
C3, 4 and 5 (roots of phrenic nerve)
what would happen after a decrease in PO2 involving the peripheral chemoreceptors?
- if reduction in arterial blood -> peripheral chemoreceptors are stimulated
- when stimulated -> send neural signals to the nucleus tractus solitarius in brainstem
- these stimulate an increase in ventilation via the rhythm generating neurons in the ventral respiratory group of neurons
- overall: restore PO2 levels
what is a decrease in PO2?
hypoxia
decreased oxygen levels circulating in the bloodstream
where are the peripheral chemoreceptors located?
- carotid sinus
- aortic arch
what receptors are stimulated by a rise in PCO2 levels?
central chemoreceptors of the brain
what is a rise in PCO2 called?
hypercapnia
how is an increase in PCO2 corrected?
- stimulation of central chemoreceptors
- signals processed and info passed to neuronal clusters in brainstem -> involved in breathing
- ventilation increases -> levels restored
parasympathetic nerves effect on upper airways
- nerves derived from Vagus (X) nerve (the bronchioles)
- can cause mild to moderated bronchoconstriction
- also involved in mucus production when stimulated by irritants -> narrowed airways in asthma
which neurotransmitter is involved in the effect of the parasympathetic nerves on the upper airways?
acetylcholine
what changes can asthma cause to the airways?
- smooth muscle cell hypertrophy / hyperplasaía & contraction
- oedema
- mucus hypersecretion
- epithelial damage
- infiltration of inflammatory cells / inflammation
- bronchial hyper reactivity
what is FEV1?
- a measurement of an individuals forced expiratory volume in the first second
- the amount of air that can be forced from the lungs in the first 1 second
- important = helps indicate the health of the airways and if they are very narrowed or not
- those with asthma have lower values
anabolic pathways
- uses energy
- build complicated molecules from simpler ones
catabolic pathways
- release energy
- break complicated molecules down into smaller ones
what is STPD?
standard temperature (273K) and pressure (760mmHg) dry
- refers to step where you standardise conditions of a measurement to accurately measure gas volumes
why is STPD needed to calculate oxygen utilisation during exercise?
- because temperature and pressure of gases can change depending on the environmental conditions
- if standardise them, can be comparable to other values taken at other times
what is the lactate threshold?
- the point where blood lactate starts to accumulate above resting levels during exercise of increasing intensity
- good indicator of an athlete´s potential for endurance exercise
- reflect aerobic and anaerobic energy systems
what happens when an indivdual passes the lactate threshold?
- level of lactate in blood increases (increased H+)
- H+ in blood is buffered by bicarbonte forming carbonic acid -> dissociated into H2O and CO2
- causes increase in pulmonary CO2 whihc can cause minute respiration to rise
how to calculate partial pressure?
= fraction of gas (Fgas) in gas mixture x barometric pressure (Pb)
total pressure
must equal the sum of partial pressures or tensions of gas
what happens to air in airways?
- waremd
- humidified
- becomes saturated with water vapour (at partial pressure & body temp = 47mmHg
role of nasal cavities & paranasal sinuses in air movement
- filter
- warm
- humidify air
- detect smells
role of pharynx
- conducts air to larynx
- chamber shared with digestive tract
larynx role
- protects opening to trachea
- contains vocal cords
trachea & bronchi role
- filters air
- traps particles in mucus
- cartilages keep airways open
lungs
- responsible for air movement through volume changes during movements of ribs and diaphragm
- include airways and alveoli
alveoli
acts as sites of gas exchange between air and blood
muscles of inspiration
- the diaphragm
- external intercostals
- sternocleidomastoid
- pectoralis minor
muscles of expiration
- internal intercostals
- diaphragm
- abdominals
- quadratus lumbroum
diaphragm
major inspiratory, dome shaped muscle
quiet breathing inspiration
- active
- diaphragm contracts downward
- pushes abndominal contents outward
- external intercostals: pull ribs outward and upward
quiet breathing expiration
- passive
- via elastic recoil
strenuous breathing inspiration
- active
- diaphragm contracts stronger
- greater contraction of external intercostals
- insipiratory accessory muscles activated (sternocleidomastoid)
strenuous breathing expiration
- active -> push air out to get air in again
- abdominal muscles involved
- internal intercostal muscles oppose external intercostals -> push ribs down and inwards
pleural cavity
small space between chest and lung wall
functions of upper airways
- humidify -> saturate with water
- warm -> to body temp
- filter air
- conduct air to lungs
filtering air
- lining of upper airways with ciliated epithelium
- particles stick to mucous
- mucous moved towards mouth by beating cilia
- stops foreign particles from entering
what cells line the upper airways to bronchioles?
pseudo-stratified ciliated columnar epithelium
goblet cells
- sit on top of cilia
- produce mucous
the respiratory tree
= conducting airways + respiratory airways
- airways branch into smaller, more numerous bronchioles
- terminate in a group of alveoli
- each division = increase in number, decrease in diameter, increase in s.a.
conducting airways
- bronchi contain cartilage and nonrespiratory bronchioles
- 150mls in volume
respiratory airways
- bronchioles with alveoli
- where gas exchange occurs
- 5mm long
- huge s.a.
- hold up to 2500ml
what is a respiratory unit?
= gas exchanging unit
- basic physiological unit of lungs
- consisting of respiratory bronchioles, alveolar ducts and alveoli
alveoli
- 300-400million alveolar sacs
- polygonal in shape
- composed of T1 and T2 epithelial cells
- air filled
- thin walls
- covered by capillaries
- allow for gas exchange
pulmonary artery
- brings deoxygenated blood from rest of body back to lungs
- blood oxygenated in lungs
pulmonary vein
takes oxygenated blood from lungs to rest of body cells and tissues
type 1 epithelial tissue in alveoli
- 97% of s.a.
- primary site of gas exchange
type 2 epithelial tissue in alveoli
- septal cells
- occupy 3% of s.a.
- produce pulmonary surfactant (reduces surface tension)
alveolar macrophages
removal of debris
why are alveoli perfect for gas exhange?
- large s.a.
- v thin walls
- good diffusion characteristics for faster gas exchange
2 blood supplies to the lungs
- pulmonary circulatuion
- bronchial circulation
(- lymphatic system)
pulmonary circulation
- brings deoxygenated blood from heart to lungs
- oxygenated blood from lung to heart & rest of body
- total blood vol = 500mls (10%)
- blood volume increases with exercise
pulmonary circulation
brings deoxygenated blood to lung parenchyma
lymphatic system
defense and removal of lymph fluid
arteries
- thin walled
- highly compliant
- larger diamter
- low resistance
alveolar capillary network
- gas exchange between dense mesh-like network of capillaries and alveoli
- type 1 alveolar epithelial cell, capillary endothelial cell & basement membrane
- ideal environment for gas exchange
- rbc pass through capillaries in less than 1 second -> enough time for CO2 and O2 exchange (O2 binds to haemoglobin)
gas gradients
- gases move down their concentration gradients
- similar volume of CO2 and O2 move each minute
- O2 has a greater pressure gradient than CO2
- CO2 more diffusible
pulmonary circuit
O2 enters blood
CO2 leaves
systematic circuit
O2 leaves blood -> into cells & tissues
CO2 enters blood
O2 and CO2 transport
- respiratory & circulatory systems function together
- CO2 from tissues to lungs
- O2 from lungs to tissues
gas diffusion
- movemnet of gas via diffusion
how does the respiratory system facillitate gas diffusion
- large s.a
- large partial pressure gradients (high to low)
- gases with advantageous diffusion properties
- specialised mechanisms for O2 and CO2 transport between lung and tissues
how is oxygen transported?
- dissolved in blood
- bound to haemoglobin (Hb)
dissolved O2
- measured clinically in arterial blood sample
- only small % dissolved
- amount of O2 dissolved in blood proportional to partial pressure
- not adequate for body requirements even at rest
haemoglobin
- major O2 transport molecule
- found in red blood cells
- made of 4 heme groups joined to globin protein
- each heme group has iron in reduced ferrous form -> site of O2 binding
- 280 million
- binding & dissociation of O2 with Hb in milliseconds -> so short bc rbc only in capillaries for 1 second
- O2 binding to Hb is reversible
oxygen saturation
- each Hb can bind 4 O2
- O2 saturation = amount of O2 bound to Hb relative to max amount that can bind
- 100% sat = all heme groups of Hb bound to O2 (4O2)
how to measure O2 saturation
- pulse oximeters
-> measure ratio of absorption of red and infared ligt by oxyHb and deoxyHb
CO2 production
- 200ml CO2/min
- 80 molecules of CO2 expired by lung for every 100 molecules of O2 entering
respiratory exchange ratio
ratio of expired CO2 to O2 uptake
normal = 0.8
CO2 transport
- 7% dissolved in blood
- 23% bound to Hb
- 70% converted to bicarbonate
bicarbonate
- The bicarbonate ion present in the blood plasma is transported to the lungs
- there it is dehydrated back into CO2
- CO2 released during exhalation
what can affect breathing?
- sleep
- phonation
- emotion
- cardiovascular
- temp
- exercise
chemoreceptors
- sensory receptors that detect chemical changes in surrounding environment
- in respiratory system: detect changes in PO2, PCO2, pH in blood
peripheral chemoreceptors
- small & highly vascularised
- region of aortic arc & corticoid sinuses
- info sent via glossopharyngael & vagus nerves to nucleus in brainstem (NTS)
what do peripheral chemoreceptors detect?
- decreases in PO2 (hypoxia)
- stimulated by a reduction in aterial PO2 -> neural signals sent from carotid and aortic bodies to NTS -> ventillation increases to restore PO2 levels
central chemoreceptors
- clusters of neurons in brainstem
- activated when PCO2 increased or pH decreased
action of central chemoreceptors
- increase in arterial PCO2 -> cc stimulated -> signal processed -> info passed to neural clusters in brainstem involved in breathing -> increase ventilation to restore PCO2 levels
hypoxia
a state in which oxygen is not available in sufficient amounts at the tissue level to maintain adequate homeostasis
hypercapnia
- when you have too much carbon dioxide (CO2) in your bloodstream
- can be result of hyperventilation
mechanoreceptors
- sensory receptors
- detect changes in pressure, movement and touch
- respiratory system: movement of lung and chest wall
action of mechanoreceptors
- inflation of lung -> activated -> neural signal sent via vagus nerve to NTS in bainstem -> ventilation adjusted
integration of info about breathing in brainstem
NTS: gets info from mechanoreceptors & chemoreceptors -> info processed by brainstem respiratory neurons -> generate rhythm of breathing -> rhythmic signal sent to respiratory muscles
respiratory neurons in brainstem
- inspiratory neurons: active during inspiration
- expiratory neurons: active during expiration
- fire at certain phase each time in respiratory cycle
respiratory rhythm
- generated in brainstem
- pontine respiratory group
- ventral respiratory group (rhythm generating neurons)
- dorsal respiratory group (NTS)
output from brainstem to respiratory muscles
- brainstem neurons produce rhythmic output -> neural signals sent to spinal cord -> phrenic nerve exits spinal cord at C3-5
- phrenic nerve innervates diaphragm
- nerve exiting thoracic spinal cord innervate intercostal muscles
function of the lungs
- oxygenate blood
- by bringing inspired air in close contact to oxygen-poor blood in the pulmonary capillaries
- promotes efficient gas exchange
bronchia
distribute air within lungs
control of airway function
regulation of musculature, blood vessles & glands
- afferent pathways: sensory stimuli from lungs -> CNS
- efferent pathways: regulation of muscle contraction
afferent pathways
- chemoreceptors and nicireceptors
- respond to exogenous chemicals, inflammatory mediators and physical stimuli
efferent pathways
- parasympathetic nerves -> bronchoconstriction (upper airways) & mucous secretion (acetlycholine)
- sympathetic nerves -> dont innervate airway smooth muscle (blood vessels and glans, noradrenaline)
- inhibitory non-adrenergic non-cholinergic (NANC) nerves relax airway smooth muscles
- excitatory NANC nerves -> cause neuroinflammation bc of tachykinin release
NANC - non-adrenergic non-cholinergic nerves
- regulate airway function
- intervene in secretion of gases and ions
- relaxons in airways
regulation of mucus secretion
- goblet cells & mucous glands
- lowered by smpathetic NS
- increased by parasympathetic NS -> inflammatory mediators & chemical/physical stimuli
necessity of mucous
- line lungs
- protect epithelial cells
- capture pathogens
- provide liquid - fluid interface that would help exchange of O2 between blood vessels and air
- in asthma = overproduction
asthma
- obstructive lung disease
- chronic inflammatory condition with acute exacerbation
- thickening of airways
asthma treatment
include bronchodilators & anti-inflammatory agents
structural changes in asthma
- smooth muscle cell hypertrophy / hyperplasia & contraction
- thickening of airways
- infiltration of inflammatory cells
- hypersecretion of mucous
- epithelial damage
triggers for asthma
- pet dander
- dust mites
- moulds
- pollens
- respiratory infections
- asthma
- cold air
- smoke
- stress
- alc
- aspirin / other dugs
asthma diagnosis
- spirometry
FVC: forced (expiratory) vital capacity -> persons maximal expiration following full inspiration
FEV1: forced expiration volume in 1 second
FEV1: > 75% normal
< 3 seconds in people without asthma
asthma effect on FEV1
- reduced FEV1
- many cells and mediators play part in this
early asthma phase
- bronchospasm
- drugs targetting bronchoconstriction
late asthma phase
- inflammation
- drugs targetting inflammatory response
what are anti-asthmatics
- bronchodilators / relievers
- anti-inflammatory agents / preventors
bronchodilators
- relieve muscles surrounding narrowed airways
- beta-2 antagonists e.g. salbutamol
- muscarinic antagonists e.g. ipratropium
- methxlanthines e.g. theophylline
anti-inflammatory agents
- glucocorticoids -> inhibit prostanoids, leukotrienes and cytokines
- momntelukast -> cysteinyl leukotriene receptor
- sodium cromoglicate
