Respiratory System Flashcards
What are the functions of the respiratory system?
resp function:
- gas transport for metabolism
- move o2 from air into pulmonary blood
- clearance of co2
non-resp function
- lungs receive 100% of cardiac output from right heart
- filter blood, chemical processing, maintenance and defences (first line)
- facilitate venous return
Definition of respiration vs ventilation?
respiration: interchanges of gases between the atmosphere and the cells of the body
ventilation: transport of air to and from the lungs
What are the 5 steps to overall gas transport?
- ventilation: movement of bulk airflow, delivering air to the respiratory zone where gas exchange occurs
- gas exchange/lung diffusion: gas exchange btwn resp zone and blood - O2 moves across to blood and RBCs; reverse for CO2
- circulation/transport: blood to/from tissues, requires adequate function of the pulmonary and systemic circulations
- tissue diffusion: erythrocyte/plasma to/from tissue cells
- internal respiration: metabolism using O2 and producing CO2
What are the five airways?
- nasal/oral cavities
- pharynx and larynx
- trachea
- bronchi
- bronchioles
What airway connects to alveoli?
bronchioles
What are four functions of the airways?
- delivering gas to the respiratory zone
- air warmed to core body temperature
- gas humidification (saturation with vapor to prevent dehydration of the respiratory epithelium in alveoli)
- filtration/cleansing: prevents foreign objects/microorganisms to enter the lungs (reduces risks of injury and infection)
What are the three structures of the nasal/oral cavities?
- inner surface - mucous membrane that warms/humidifies air
- hair in nostrils (filter)
- epithelium contains ciliated cells and mucus cells (goblet) which trap foreign objects and move the mucus towards the pharynx
What is the function of the pharynx
connection between nasal/oral cavity and the larynx
What is the function of the larynx?
connects pharynx and the trachea: glottis and epiglottis (cartilage that prevents food to enter the trachea)
Which airway structure contains the vocal cords?
larynx
What is the trachea kept open by?
cartilage rings
What is a characteristic of the trachea?
inner surface lined with ciliated and mucus cells, mucus traps particles, and coordinated cilia movements push the trash back towards pharynx
What are some characteristics of the bronchi?
- possess cartilage plates to maintain shape
- branch off into narrower tubes with less cartilage
What are the primary bronchi?
part of the bronchi, the very beginning where the bronchi split into two tubes into each lung
Do bronchioles have cartilage?
lack cartilage - depends on lung recoil to maintain potency (possess smooth muscle)
Do bronchi and bronchioles have ciliated and mucus cells?
yes
Why doesn’t the bronchi need to be as sturdy as the trachea?
ribs protect thoracic cavity
What is a bronchiospasm?
muscle layers that control constriction of bronchiole can compress it when inflammed
Does airway cross sectional area increase or decrease as you move from the trachea to the respiratory zone?
increases dramatically moving from trachea to resp zone
- geometric increase in small airways
- reduces veocity of airflow to zero
- movement of gas through diffusion only
What are the two methods of airway clearance?
- cilia and goblet cells work to move thin sheets of mucus from lower parts of the lungs to the throat region
- defensins: airway defensin destroys bacteria
What happens in the airways during inflammation?
accumulation of mucus and pus in the trachea caused by cells inability to move it up creates restriction of airflow/turbulence
Where are alveoli located?
clusters around terminal bronchioles
What are alveoli formed by?
single layer of epithelial cells
What are alveoli surrounded by?
capillary network
How many layers of cells are air and blood separated by?
two layers (epithelium and endothelium)
What do type 2 epithelial cells produce?
fluid (surfactant which reduces surface tension) - maintains opening of the alveoli
What happens if small particles reach the alveoli?
phagocytized by macrophages
What are the two types of epithelial cells?
type 1: squamous
type 2: epithelial
type 1 becomes type 2 eventually
What is the thoracic cavity?
space within the thoracic cage between: thoracic vertebras, ribs and intercostal muscles, sternum
What is the diaphragm?
separate from the thoracic and abdominal cavity, sheet of skeletal muscles and tendon
What is the mediastinum?
divide the thoracic cage in 2 halves (from spine to sternum)
connective tissue containing vessels, nerves, trachea, esophagus and the heart
each lung fills 1 half
What is the pleural membrane?
cover lungs, wet epithelium, contains parietal and visceral pleura
What is the intrapleural space?
filled with fluid, lubrication for friction free movements
What is a rule about ventilation?
flows from high to low pressure
resistance of flow (R) due to friction of air particles with each other and with the ducts
What is the formula for flow?
F = change in P/R
What is the relationship between R and deltaP?
if R increases, deltaP increases
if R decreases, deltaP decreases
What controls deltaP?
compression/expansion of the lungs by resp muscles
Inspiration vs expiration passive or active mechanisms?
Inspiration - active mechanism
Expiration - passive mechanism
What are the steps to inspiration?
diaphragm contracts -> expands thoracic volume -> creates negative pressure -> lung expands -> increase in alveolar volume -> negative pressure gradient facilitates flow down airways
What are the steps to expiration?
end of inspiration -> inspiratory muscles relax -> allows lung to spontaneously recoil -> increase pressure in alveoli -> create pressure gradient from alveoli to atmosphere
At rest, which muscle of the respiratory system is the most important muscle?
diaphragm
What is Boyles law of gases?
for a gas at a set temperature, pressure and volume are linked P1V1 = P2V2
What is the relationship between V and P?
- if volume increases pressure decreases
- if volume decreases pressure increases
What happens to the P during inspiration and expiration?
Inspiration: Palveolar < P atmosphere
- propels air through the airway until P alveolar = P atmos
Expiration: P alveolar > P atmosphere
- airflow outward until equilibrium reached
What are some special cases of pressure movement in the airways?
horses: end of expiration active - beginning of inspiration passive
locomotion (walk/run): more than just diaphragm and intercostal muscles, muscles take active part in expiration to speed it up, galloping synchronization with breathing
diving mammals: voluntary apnea, strong conducting airways, when under water, compressed gas pushed towards airways (no gas exchange) - prevents gas entry into blood
What are two factors influencing ventilation?
airway resistance
lung compliance
alveolar surface tension
Where does airway resistance occur mostly?
nasal cavity
Does more turbulence create more airway resistance?
yes
What influences airway resistance in the anatomy of airways?
reduced diameter with branching increases the resistance, parallel branches results in increased SA which compensates for increased resistance
as well as constriction of smooth muscle in bronchioles
What controls the constriction of smooth muscle in the bronchioles?
ANS, sympathetic relaxes cells and parasympathetic contracts cells
What is lung compliance?
ability of the lung to distend followed by the ability to recoil
How does lung compliance occur?
through elastic fibers in the lung, muscle tissue in the intercostal muscles
What does lung compliance depend on?
- depends on the elasticity of the tissues in the lung and the thoracic cage
- depends on the surface tension in the alveoli
How does alveolar surface tension occur?
hydrogen bonds in water molecules when in contact with air
What does alveolar surface tension reduce?
SA
What does the moisture lining in the alveoli create?
surface tension against distension
What reduces the surface tension in the alveoli?
surfactant
What is surfactant made of?
mixture of phospholipids, Ca2+ and proteins, which reduce the surface tension between hydrogen molecules
What is barker syndrome?
in piglets, inadequate production of surfactant, increase in surface tension, increase in resistance to distension, decrease in ventilation
What is a spirometer?
measure volumes of air inhaled and exhaled, also monitors the respiratory frequency
What is tidal volume?
volume flowing through airways (CVt)
Describe the graph of the wave of volume of air passage/draw
yellow - rest
blue - what we measure
purple - goes beyond regular distension, during exercise
if you add all three together you get vital capacity (max one can breathe)
green - volume of air that will always remain in lungs
refer to resp I slides
What are the various volumes of air during respiration?
Expiratory Reserve volume (ERV) - after normal expiration, it is possible to force more air out
Residual volume (RV) - after ERV forced out, there always remains air in the lungs
Vital capacity (VT) - max air that can be inhaled/exhaled
Total lung capacity = RV + VT
What is a property of gases?
gas molecules constantly moving
What is total pressure determined by?
the total number of gas molecule per volume unit
What is the partial pressure of gases?
in a mixture - total pressure % of that gas, independent of other gases present in the mixture
At equilibrium what happens to the relative amount of dissolved gas?
constant
What is diffusion in gas exchange
passive movement of gas molecules from regions of high concentration (partial pressure) to regions of low concentration (partial pressure)
What is the air velocity in alveoli?
0
What is the atmospheric partial pressure in the alveoli?
constant
What does diffusion across the alveoli depend on?
alveolar and blood partial pressures
- ventilation for alveoli (how much air replaced in alveoli)
- tissue consumption for blood
At higher altitudes, what happens to the pO2 in the atmosphere?
it is lower as the altitude increases
is the pCO2 in the atmosphere higher or lower than alveoli and blood?
pCO2 in the atmosphere is much lower than alveoli/blood
Draw out the diagram for the pO2 and pCO2 exchange between alveoli and blood resp II
refer to slides
- partial pressure of O2 must be higher in alveoli than blood so it can oxygenate blood
- goal is to maintain partial pressure of 100mg Hg
- lower partial pressure of CO2 in alveoli than blood but higher than atmosphere to force CO2 out of lungs
- if we obstruct the airways, partial pressure of O2 will gradually decrease and CO2 will gradually increase, therefore cannot oxygenate the blood = asphyxiation
where does gas exchange occur?
between alveoli and blood capillary network
Where does the blood from the capillaries flow from?
from the right ventricle
Are there capillaries from the left side of the heart and if so why?
yes, its to bring oxygen to lung tissue
What is the journey of pO2 as it diffuses across the alveoli?
blood entering alveolar capillaries has low pO2, O2 diffuses from alveoli to the blood, at the end of capillary, pO2 is the same in blood and alveoli, for CO2 pCO2 higher in blood returning capillary then diffuses out toward alveoli
What are the main determinants of diffusion of O2 across the alveoli? Factors of the equation?
- driving partial pressure gradient (PalveoO2-PcapO2)
- surface area available for diffusion (A)
increased area, more exchange, capillaries can open during exercise to increase exchange - thickness of the air-blood barrier (X)
deep inspiration during exercises reduces the distance between alveoli and capillary epithelium - physical properties of the gas (D)
What is the equation to determine the volume of O2?
VO2 = DA(PAO2 - PcapO2)/X
What is perfusion?
blood entering the lung
What needs to happen in terms of perfusion for optimal gas exchange?
need to match ventilation with the blood flow
What is the optimum ventilation/profusion for bipeds at rest?
gravity - perfusion (blood flow) lowest at the top of the lung (capillaries can collapse), not so pronounced for ventilation
What is the equation used for ventilation/perfusion?
V/Q
When does V/Q become more uniform?
during exercise (more blood pump throughout the lung)
How can diseases affect ventilation/perfusion in the alveoli?
cause a V/Q inequality
What is hypoxic vasoconstriction?
natural mechanism to minimize the impact of diseases against ventilation/perfusion on the alveoli
- closing of the poorly ventilated alveoli
- redirecting blood towards the well ventilated
How is hypoxic vasoconstriction initiated?
reduction of pO2 and/or increase in pCO2 in the interstitial fluid of affected areas
What are some examples of impaired pulmonary gas exchange?
- thickening of alveolar capillary membrane: increases the time for diffusion across the membrane and decreases rate of diffusion
- high altitude or low air pO2: decrease alveolar oxygen pressure, hence decrease driving pressure
- hypoventilation: inadequate ventilation of lung
- ventilation-perfusion inequality: ventilated alveoli with no blood supply or vice versa
How does gas exchange in tissue work?
diffusion driven by difference in partial pressure
- cells consume O2/produce CO2
- blood from left heart loaded with O2, diffusion of O2 will occur from blood to interstitial fluid to the cells, diffusion of CO2 will occur from the cell to the interstitial fluid in the blood
How much of oxygen in blood is bound and what is it bound to?
over 97% is bound to hemoglobin
What happens to the rest of the oxygen not bound to hemoglobin in blood?
circulates dissolved in blood
What is henry’s law?
amount of gas dissolved is directly proportional to partial pressure of that gas
What is the structure of hemoglobin?
4 heme groups, each with 1 iron atom that can bind 1 molecule of O2
How many O2 can hemoglobin bind?
4 molecules of O2 to 1 hemoglobin
What is oxygen saturation?
amount of O2 carried divided by the total oxygen capacity of blood
What is the formula for % saturation?
amount O2 bound/max capacity of Hb for O2
What is the relationship between Hb and O2 at equilibrium?
Hb+O2 <-> HbO2, can be bound or not and change at will
What happens if the concentration of either Hb or O2 changes?
equilibrium is displaced and everything will be off
O2 saturation in the blood is directly linked with?
pO2
How does saturation occur in the lungs and tissues?
blood in lung capillaries = dissolved O2 increases = more HbO2
blood passes through tissue capillaries = dissolved O2 decreases = dissociation of HbO2 occurs
What does the O2 saturation curve follow?
sigmoid shape
What is the percent saturation normally out of the lungs and out of the tissues?
100% saturation out of the lung
75% saturation out of the tissues
What happens to the Hb at high altitudes?
pO2 in air decreases, the body compensates by increasing the number of erythrocytes and Hb
What are 3 factors affecting Hb saturation?
- pH
- temperature
- 2,3 DPG
How does pH affect Hb saturation?
increase in metabolism = increase in H+ which decreases affinity of hB for O2, curve will be shifted to the right, need higher pO2 for saturation
How does temperature affect Hb saturation?
increased metabolism = increased heat
How does 2,3 DPG affect Hb saturation?
result from glycolysis in erythrocytes, binds to Hb
Draw the graphs for DPG, temp and acidity affect on Hb saturation
refer to resp III
What are the three forms that CO2 can be carried in the blood?
- physical solution (5-10%)
- carbamino compounds (bound to proteins) (15-20%)
bind to NH groups on proteins, especially Hb - bicarbonate (70-75%)
reaction in erythrocytes
Do respiratory muscles contract rhythmically?
yes, medulla oblongata (brain stem)
How are respiratory muscles contracted?
skeletal muscle needs APs from motor neurons
Is ventilation automatic?
yes and is constantly adjusted to needs
Where is the respiratory center?
network of synchronized neurons within the brainstem
What are inspiratory neurons?
part of resp center, stimulate motor neurons in the spinal cord, contraction of respiratory muscles
What are inspiratory neurons controlled by?
another network in the brain stem: central pattern generator (CPG)
also under influence of stretch receptor in the lung, bronchiole and muscles
What is the respiratory center under influence from?
pO2, pCO2, and H+ concentrations
What detects O2 CO2 and H+ in the brainstem?
chemoreceptors
What is the type of chemoreceptor in the brainstem?
central chemoreceptors
How do central chemoreceptors detect chemicals in the brainstem?
indirectly detect changes in pCO2 in the blood to the brain, CO2 enters CSF by diffusion from the blood across the blood-brain barrier, transformed into H+ which is the trigger
Where are peripheral chemoreceptors located?
carotid and aorta
What do peripheral chemoreceptors do?
detect direct arterial changes in pO2 pCO2 and H+
What is the role of chemoreceptors?
detect O2, CO2 and H+
information sent to the respiratory centers
Draw the diagram of the chemoreceptors regulation
refer to resp III slides
What is hypoxia?
deficit in O2 supply to the cells
What are the symptoms of hypoxia?
confusion, hallucination, loss of consciousness
What are the 4 potential causes of hypoxia?
- low arterial pO2 from pulmonary diseases/failure high altitude
- reduced transport capacity = problem with Hb
- reduced blood flow to tissues
- impaired cell metabolism (cyanide poisoning)
What is the remedy for hypoxia?
inhalation of pure O2
