Module 10 Flashcards
List the main functions of the respiratory system
Transport of O2 from air into blood Removal of CO2 from blood into air Control of blood acidity (pH) Temperature regulation Forming a line of defense to airborne particles
Describe the path of air into the lungs
Airway starts at nasal cavity and mouth, joining at the pharynx, leading to larynx (voice box), which becomes the trachea, which divides into two main bronchi (left and right) into the lungs, dividing into smaller bronchioles until becoming alveoli, the site of gas exchange
Describe the blood vessels from entering the lungs to leaving the lungs
Pulmonary artery brings deoxygenated blood to the lungs, branches into capillaries around each alveolus, whose structure maximizes gas exchange (thin endothelial walls, large cross-sectional area, low blood velocity). O2 diffuses in, CO2 diffuses out, then pulmonary vein brings oxygenated blood back to the heart
Describe the anatomical relationship of the lungs to the chest wall, pleural membrane, and diaphragm
Lungs are inside the thoracic cavity surrounded by the rib cage (laterally, posteriorly and anteriorly) and the diaphragm (inferiorly), with two thin pleural membranes, one lining the ribs (parietal) and one on the lungs (visceral)
Describe the histological structure of an alveolus (type I vs type II cells)
An alveolus is toughly 0.3mm in diameter, with walls one cell thick made of alveolar epithelial cells (type I cells)
Tyle II cells secrete surfactant, which lines the alveoli
Fibers of elastin and collagen are present in walls of the alveoli and around blood vessels and bronchi
Lots of capillaries surround the alveoli closely
Describe the pleural membranes and intrapleural space, and their functions
Parietal pleura lines and sticks to the ribs, visceral pleura lines and sticks to the lungs
Between them is intrapleural space, containing a small amount of pleural fluid, which reduces friction between the two pleura during breathing
Define alveolar/intrapulmonary pressure
Pressure inside the lungs
Define intrapleural pressure
Pressure in the intrapleural space
Define atmospheric pressure
Pressure outside the body (760mmHg at sea level)
Define transpulmonary pressure
Difference between the alveolar and intrapleural pressures
Explain the significance of a low intrapleural pressure compared to the alveolar pressure
This would be a positive transpulmonary pressure
Important because the difference in pressure holds the lungs open, in healthy lungs, transpulmonary pressure is positive (outwards) to keep the lungs and alveoli open (they want to collapse)
Describe what happens during a pneumothorax
If both alveolar and intrapleural pressures were equal, transpulmonary would be 0, no pressure holding lungs open, causing collapse
Occurs when intrapleural space is punctured, causing the pressures to equalize
Generally only one lung collapses because the intrapleural spaces are isolated from each other
Define Boyle’s Law
When the volume of a container decreases, the pressure inside increases, and vice versa
Important for ventilation
Basically pressure varies inversely with volume
Describe the process of inspiration
To decrease pressure, lung volume must increase, so diaphragm contracts, moving downward, and external intercostal muscles of ribs contract, lifting ribcage up and out
This drops alveolar pressure, pressure gradient now exists (low in lungs, higher outside), so air flows into lungs
This is an active process, requires signals from brain stem to contract muscles
Describe the process of expiration at rest
Diaphragm and external intercostal muscles relax, causing lungs to recoil to original size; volume decreases, alveolar pressure increases above outside pressure, so pressure gradient is now reversed and air flows out
This is a passive process, no muscle contractions
Describe the process of expiration during exercise
Air must be forced out of lungs, requiring contraction of abdominal and internal intercostal muscles. When they contract, decreases volume of lungs, creating larger pressure gradient and forcing air out
This is an active process
Define pulmonary compliance
Stretchability of the lungs (more stretchable is more compliant); the volume change that happens as a result of a change in pressure
Explain the importance of pulmonary compliance
Equation: compliance = volume change / pressure change
Important because it determines the ease of breathing, a lung with decreased compliance is difficult to inflate, but one with high compliance is difficult to deflate
List two major factors that influence compliance of lungs
The amount of elastic tissue found in the walls of the alveoli, blood vessels, and bronchi
The surface tension of film of liquid lining the alveoli
Describe pulmonary fibrosis
A disease causing decrease in compliance, caused by constant inhalation of fine particles (asbestos, air pollution, coal dust). Immune cells can’t destroy them, so they form large inelastic collagen deposits that form fibrous scars
List two factors that cause an increase in pulmonary compliance
Normal aging and pulmonary emphysema
Describe pulmonary emphysema
A chronic condition from smoking, destroys elastin fibers in the lungs (elastin decreases compliance), so without them compliance increases, inhalation is easy, but without elastin its hard to recoil the lungs, exhalation requires muscular contraction even at rest
Describe the two elastic tissue components in the lungs
Fibers of elastin and collagen are arranged in special geometric arrangements where elastin are easily stretchable but collagen are not, contributes to 1/3 of total compliance of healthy lungs
Elastin - adding more makes lungs less compliant because it takes energy to stretch, inspiration becomes more difficult, expiration becomes less difficult
Collagen - inelastic, forms deposits in pulmonary fibrosis, decrease in collagen causes increase in compliance
Define surface tension
Force developed at the surface of a liquid due to attractive forces between water molecules
Explain how surface tension affects lung compliance/elastic behaviour
2/3 of elastic behaviour of lungs is attributed to surface tension of the liquid film lining alveoli, which tends to collapse alveoli, decreasing compliance and making inflation difficult
The majority of forces between water molecules are inward in a drop, no outward balancing force on surface, so the inward forces would cause alveoli to collapse
Define pulmonary surfactant
A lipoprotein substance produced by type II alveolar cells, consisting mostly of phospholipids (hydrophilic head, hydrophobic tail)
Explain the function of pulmonary surfactant
When surfactant is added to water, it lies on the surface. Phospholipid head groups are attracted to water, and balance the inward forces of the water drop with an outward one. Forces now equal in every direction, water drop will flatten due to decreased surface tension, so alveoli won’t collapse.
Surfactant is released during deep breathing, so important to breathe deeply after surgeries in thoracic cavity to stimulate production
List the four basic lung volumes
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume
Define tidal volume
The volume of air entering or leaving the lungs during one breath at rest
Usually 500mL
Define inspiratory reserve volume
The maximum amount of air that can enter the lungs in addition to the tidal volume
2500mL
Define expiratory reserve volume
The maximum amount of air that can be exhaled beyond the tidal volume
1000mL
Define residual volume
The remaining air in the lungs after maximal expiration
1200mL
List the four basic lung capacities
Inspiratory capacity
Functional residual capacity
Vital capacity
Total lung capacity
Define inspiratory capacity
The maximum amount of air that can be inhaled after exhaling the tidal volume
= tidal volume + inspiratory reserve volume
Define functional residual capacity
The amount of air still in the lungs after exhalation of the tidal volume
= expiratory reserve volume + residual volume
Define vital capacity
The maximum amount of air that can be exhaled after a maximal inhalation
= inspiratory reserve volume + tidal volume + expiratory reserve volume
Define total lung capacity
The maximum amount of air lungs can hold
= vital capacity + residual volume
Describe a spirometer
A device used to measure lung volumes and capacities, useful in helping diagnose pulmonary diseases like asthma, bronchitis, and emphysema
Normally an air filled chamber with attached hose, as air is drawn out during inhalation, chamber falls, pulls chain attached to a pen that rises, then during exhalation, chamber fills, rises, and pen falls, so pen marks the path on a paper that indicates lung volumes
Define pulmonary ventilation (VE)
The amount of air that enters all of the conducting and respiratory zones in one minute
Define conducting zone
The anatomical dead space, the area of the lungs where no gas exchange occurs because there’s no alveoli
Define respiratory zone
The region of the lungs with alveoli, where respiration/gas exchange will take place
Explain the equation for pulmonary ventilation (VE)
VE = tidal volume (mL) x respiratory rate (breaths/min)
At rest, VE is roughly 7500mL/min, which is the amount of air entering the entire pulmonary system, conducting and respiratory zones
Explain the difference between pulmonary ventilation and alveolar ventilation
Pulmonary ventilation is the amount of air entering all of the pulmonary system
Alveolar ventilation (VA) is the volume of air entering just the respiratory zones, the air available for gas exchange
Alveolar ventilation is included in pulmonary ventilation
VE is easy to measure, while VA is difficult because conducting zone volume must be taken into account
Define alveolar ventilation (VA)
The volume of air entering only the respiratory zone each minute, represents the volume of fresh air available for gas exchange
Describe the equation for alveolar ventilation (VA)
VA = VE - VD
VD is the dead space ventilation
As a rule of thumb, dead space volume is a healthy person’s body weight in lbs as a number in mL
To get VD, multiply dead space volume by respiration rate, and use this estimation to calculate VA
Define partial pressure
The pressure exerted by one gas in a mixture of gases
Describe the equation for partial pressure of a gas
Partial pressure = total pressure of all gases x fractional concentration of one gas
Explain why atmospheric partial pressures aren’t a good estimation for the air in the lungs
Gas exchange is taking place in the lungs, so O2 is immediately taken up into blood and CO2 is given into lungs. This mixing of “new inhaled” with “old” gas being removed affects the actual value of partial pressures of gases
PO2 will be lower than in the atmosphere and PCO2 will be higher than in the atmosphere
Atmosphere: PO2 = 159mmHg, PCO2 = 0.3mmHg
In lungs: PO2 = 105mmHg, PCO2 = 40mmHg
Explain the importance of partial pressures for gas exchange
O2 and CO2 move down partial pressure gradients to move through the respiratory system, moving from areas of high partial pressure to low partial pressure
They can both also dissolve in water, so partial pressures describe amounts dissolved in blood plasma
Describe the diffusion of gases across the respiratory membrane
Blood enters the lungs at PO2 40mmHg and PCO2 46mmHg
Alveoli have PO2 105mmHg and PCO2 40mmHg
As blood moves past the alveoli, O2 and CO2 diffuse down their partial pressure gradients, O2 moves from alveolar space to blood, CO2 moves from blood to alveolar space
As blood leaves the alveolus, PO2 and CO2 will have equilibrated with alveolar air
Describe the partial pressure changes throughout the circulatory system
Blood leaves the lungs: PO2 100mmHg and PCO2 40mmHg
Blood returns to the heart and is pumped into circulation, entering tissue beds with these partial pressures
Cells have PO2 40mmHg and PCO2 46mmHg
As blood flows through capillaries, both move down their partial pressure gradients, O2 into cells and CO2 into blood
Blood leaving tissues will have equilibrated with cells: PO2 40mmHg and PCO2 46mmHg
Blood returns to the heart to be pumped into the lungs, cycle repeats
Describe the transport of O2 in the blood
O2 can be dissolved in plasma or carried by RBCs attached to hemoglobin (Hb can carry much more O2 than plasma)
Plasma carries only 1.5% of the O2 in blood, very little
RBCs and Hb carry 98.5% of O2 in blood, and each Hb molecule can carry 4 O2 molecules
Describe the process of erythropoeisis (RBC production)
Takes place in bone marrow, requires amino acids (component of Hb), iron (component of Hb), folic acid (for formation of new DNA and normal cell division), and vitamin B12 (needed by folic acid to function)
RBCs are destroyed and removed by the spleen and liver after a lifespan of about 120 days. 250 million RBCs are produced and die each day
Describe the function of erythropoietin
Controls erythrocyte (RBC) production, 90% secreted by kidneys and 10% by liver, stimulates bone marrow to produce RBCs. Normally secreted in low amounts to keep up with daily losses
List factors that increase secretion of erythropoietin
Decreased O2 levels reaching the kidney (caused by decrease in cardiac output, lung disease, high altitudes, or decrease in number of RBCs or total Hb content)
Testosterone levels, more testosterone means more erythropoietin
Describe blood doping
Anything increasing RBC numbers to increase performance of athletes
Removes blood, stores it, allows RBC numbers to return to normal, then re-infuse removed blood
Can lead to increased blood viscosity, increase in resistance, decreased blood flow, and possibly death
Describe the structure of hemoglobin
4 subunits, each contains a single heme molecule (disk shaped) attached to a polypeptide (long strand). Combined, the 4 polypeptides are globin. Each heme molecule can carry one O2 atom attached to a central iron atom (iron gives RBCs the red colour)
Explain what an oxyhemoglobin curve is
Shows the dissociation (unloading) of O2 from Hb at different blood PO2 levels, where higher PO2 leads to more loading of O2 onto Hb (forming HbO2), and low PO2 leads to O2 unloading from Hb
Explain the effects of PO2, pH and temperature on the oxyhemoglobin curve
High PO2 means more loading of O2, low PO2 means more unloading of O2
When exercising, body temp rises, working muscles produce lactic acid, increasing acidity of blood. Both increase in temp and lower (more acidic) pH will increase unloading of O2 from Hb, changing the shape of the curve
Lower temp and decreased acidity (higher pH) increase loading of O2 onto Hb
List the 3 forms of CO2 transport
Dissolved and carried directly in plasma
Carried as a bicarbonate ion (HCO3-)
Attached to proteins in blood, forming carbamino compounds
Describe CO2 transport dissolved in plasma
7-10% of all CO2 transport, CO2 is more soluble in plasma than O2
Moves from area of high partial pressure (in tissues) to low partial pressure (in blood), then in lungs from area of high partial pressure (in blood) to low partial pressure (in air)
Describe CO2 transport as a bicarbonate ion
70% of total CO2 transportation
Reaction: CO2 + H20 (carbonic anhydrase) H2CO3 HCO3- + H+
CO2 and H2O react to make carbonic acid with help of enzyme carbonic anhydrase, then acid dissociates into bicarbonate and hydrogen ions
Direction of reversible reaction driven by concentrations of CO2 (in plasma) and HCO3- (more CO2 drives reaction right, more HCO3- drives reaction left)
Describe CO2 transport as carbamino compounds
20-23% of CO2 transportation
CO2 in blood attached to proteins, most often Hb which has unloaded some of its O2
CO2 attaches to globin part of Hb
CO2 + Hb HbCO2
Direction of reaction driven by concentration of CO2 (in plasma) and HbCO2
Describe the chloride shift
After CO2 converts to HCO3-, most H+ bind with Hb inside RBCs (because otherwise blood would become very acidic), and as HCO3- diffuses out, acts as buffer to stabilize pH of blood
Leads to RBC becoming more positive, to balance this charge, chloride ions diffuse in, occurs quickl because RBCs are very permeable to negative ions
Describe the origin of respiration
Breathing can be spontaneous or voluntary
Spontaneous originates in medullary respiratory center of medulla oblongata, and is produced by rhythmic activity from neurons (like pacemaker of heart)
Voluntary originates in voluntary center in cerebral cortex, capable of overriding the medullary respiratory center
Describe the origin of respiration for inhalation
Medulla respiratory center contains the inspiratory center, which activates the inspiratory muscles during inhalation, and is active for roughly 2 seconds
Inspiration is always an active process requiring contraction of the diaphragm and external intercostal muscles
The inspiratory center stimulates contraction of these muscles and inhibits the expiratory center
Describe the origin of respiration for exhalation
Exhalation is a passive process involving only the relaxation of inspiratory muscles and the lung’s own elastic properties and recoiling at rest
Forceful exhalation requires contraction of abdominal muscles and internal intercostal muscles of the ribs
Signals to the muscles originate in expiratory center of the medulla, which inhibits inspiratory center when active
Describe the apneustic and pneumotaxic centers
Centers of regulation for respiration, ensure sufficient O2 and not too much CO2, and are both in the pons (above the medulla), can modify spontaneous signals from medulla
Pneumotaxic center regulates the rate of breathing
Apneustic center controls depth of inhalation and exhalation
Work together to ensure ventilation is a smooth, coordinated event
Describe the origin of respiration for voluntary respiration
Site of voluntary ventilation is the cerebral cortex, can modify ventilation by affecting signals originating in the apneustic or pneumotaxic centers in the pons
Describe the regulation of respiration
Ventilation is mostly spontaneous, but needs regulation; if holding breath too long, lack of O2; if hyperventilating, decrease in CO2 causes blood vessels to constrict, decreasing blood flow (metabolic theory), could cause constriction in brain
Regulation is a negative feedback loop, using chemoreceptors as sensors to detect gas levels
Define chemoreceptors
Special receptors that detect the concentration of O2, CO2, and H+ in the blood, divided into two groups: peripheral (in aortic arch and carotid sinus) and central (in medulla of brain stem)
Explain the function of peripheral chemoreceptors
Sensitive to O2 concentrations, only slightly sensitive to CO2 levels in blood, so small drop in O2 will be detected, sending signals to respiratory centers in the brain, which compares the signals with the set point value and will initiate an increase in ventilation to return levels to normal (or vice versa)
Explain the function of central chemoreceptors
Sensitive to H+ ion levels in the interstitial space of the brain, located in the medulla, so gases must diffuse into interstitial space, crossing the blood brain barrier
The barrier is permeable to CO2 but not H+, so CO2 must cross, react with water in the interstitial space of the brain to produce bicarbonate and H+, which will be detected
