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Flashcards in Gases and Respiration Deck (61):

Respiration - 2 parts

-features and what each part is

-Respiration = internal respiration + External respiration
Internal Respiration: aka cellular respiration
-O2 used by mitochondria to generate ATP through oxidative phosphorylation
-CO2 and H2O produced as waste products
External Respiration: exchange of gases between the atmosphere and the cells of the body


How gas exchange occurs

External Respiration - 4 processes

-Relies on diffusion
-O2 and CO2 can simply diffuse across the respiratory membrane

External Respiration - 4 processes
1. Ventiation (by bulk flow)
2. Gas exchange across respiratory membrane (by diffusion)
3. O2 and CO2 transport in the blood (by bulk flow)
4. Gas exchange in tissues (by diffusion)


Factors affecting Gas diffusion -> overview (4)

-Law that brings them all together

-4 conditions where diffusion is greatest

1. Surface area
2. Diffusion Coefficient
3. Partial pressure gradient
4. Thickness of respiratory membrane

*All given by Fick's Law

-Diffusion greatest when surface area, diffusion coefficent and pressure gradient are large, BUT diffusion distance is small.


Surface area and diffusion

-Increased surface area means more oxygen can enter the body over a given time period, and more carbon dioxide can leave

-Alveolar helps increase surface area in humans


Diffusion coefficient and diffusion

-What it is

-CO2 compared to O2

-Diffusion coefficient is a constant for each gas
-is proportional to Solubility over square root of molecular weight
-Highly soluble gases have a large diffusion coefficient and diffuse more quickly

-CO2 is more soluble in water than O2 (20x larger than the larger MW)


Partial Pressure gradient and diffusion

Diffusion distance and diffusion

Partial pressure gradient: -O2 and CO2 will diffuse passively along their individual partial pressure gradient
-move from high partial pressure to low
Diffusion distance: The thinner the respiratory membrane, the faster the rate of diffusion
-respiratory membrane must be thin
-lungs are -0.2-0.8 um thick


Disorders affecting gas diffusion (what it is, how it affects diffusion)

-Pulmonary oedema


-Pulmonary oedema: fluid on the lungs -> increases diffusion distance
-obstruct normal exchange of gases across respiratory membrane
Emphysema: Progressive destruction of the walls of the aveoli
-caused by smoking
-leaks to decreased surface area for gas exchange


Atmospheric Pressure

-what measured in
-atmospheric pressure

-air pressure at high altitudes

-Pressure measured in mmHg
-pressure of atmospheric air can push column of mercury to height of 760mmHg

-Air pressure decreases with increasing altitude
-at higher altitudes, there are less gas molecules in a give volume of air


Dalton's Law of Partial Pressure

-what it is

-In regards to atmospheric pressure

*The total pressure of a mixture of gases is a sum of the partial pressures exerted by each gas
-each gas exerts a partial pressure

-Atmospheric pressure is composed of the partial pressures of the individual gases within it (mainly Nitrogen 78%, Oxygen 21% and CO2 0.3%)
-At high altitude, atmospheric pressure is less (% composition doesn't change)


Bulk Flow

-What it is
-2 things it is related to

-Occurs when all gas molecules move together in the same direction (e.g. wind, ventilation)
-allows rapid movement over long distances
-Is proportional to the pressure gradient and inversely proportional to Resistance


Bulk Flow; Resistance

-what it is


-Airway resistance

-Exception to the rule (relationship)

-Resistance is the frictional force between air and the wall of the airway that opposes airflow
-determined mainly by the radius of airways
-as radius decreases, resistance increases
-Airway resistance: refers to the resistance of the entire system of airways
-airway branching increases total cross sectional area, reducing the total resistance

*Resistance is lowest at the bronchioles -> altho they are smallest, they are numerous!


Boyle's Law

-what it is
-what pressure is
-Relationship with volume

*Pressure is inversely related to volume (at a given temperature)
-pressure: force that exerts on the walls of its containers
-When volume decreases, pressure increases


Boyle's Law -> applied to inspiration and expiration

-Muscle contraction expands thoracic cavity, increasing volume
-Lung pressure decreases
-Pressure gradient created, resulting in bulk air flow into lungs
-Muscle relaxation decreases volume of thoracic cavity
-Lung pressure increases
-Pressure gradient created, resulting in bulk air flow out of lungs


The Ideal gas law
-> what it is

-PV=nRT or P=nRT/V
*Is a combo of all the different types of laws


Henry's Law (Solubility)


-why is it important in biology

-comparison of CO2 and O2

-Dissolving gas -> condition

-The amount of gas that will dissolve in a liquid is determined by its partial pressure and solubility
*to diffuse into cell, must first dissolve in liquid
-High solubility = low Partial pressure required to dissolve gas

-CO2 is more than 20 times more soluble in water than O2
-at any given partial pressure, more CO2 molecules will dissolve in water than O2
-Gas will be dissolved if there is a pressure gradient, only until equilibrium is reached
-DOES NOT mean no. of gas molecules in liquid = no. in air


Henry's Law: Gases in liquids

-final concentration of gas in a liquid

-Final concentration of gas in a liquid at equilibrium depends on its solubility
-e.g. CO2 is 20x more soluble than O2, therefore there will be more CO2 dissolved at same pressure


Henry's Law - applied

-The "bends"

-Breathing at atmospheric pressure = little bit of N2 dissolves in blood
-Diving increases pressure in lungs, therefore the amount of N2 dissolved in blood is greater
-The bends occurs when ascend too quickly
-N bubbles form in the blood and lead to pain, skin rash and possible brain damage
*Coming up slowly allows Nitrogen to come out of the blood


Three properties of Respiratory Membranes

-organisms that don't need respiratory structures

1. Large surface area for exchange
2. Thin - small diffusion distance
3. Respiratory membranes remain moist

*many organisms don't need respiratory structures -> rely on diffusion
-have all these features plus low metabolic demands
-e.g. marine flatworm, jelly fish, sea sponges and earthworms


Aquatic Respiration


-Fish Gills -> how they work

-Use gills for gas exchange
-large SA, highly vascularised, thin membranes that are frequently protected by coverings/flaps (Operculum)
-Water flows unidirectionally into fish's mouth, over gills and exits via operculum
-get continuous flow of O2 over gills
-some can push water over gills using muscles of buccal cavity (some rely on swimming to move water)


Challenges of aquatic respiration (2)


-Water contains only 3% of the oxygen molecules that air contains
-Water is much denser than air (means harder to move)

-Solution: continuous unidirectional flow of water and blood in opposite directions in gills -> using countercurrent exchange


Respiration in fish

-4 stages; in terms of mouth, opercular valve, buccal cavity

-Mouth opens, opercular valve closed, buccal cavity expanded -> opercular cavity expands
-low pressure -> water flows in
-Mouth closes, opercular valve closes, buccal cavity expanded, Opercular cavity expanded
-Mouth closed, opercular valve open, buccal cavity compressed and opercular cavity compresses
-pressure inside increases -> water flows out
-Mouth open, opercular valve open, buccal valve expands, opercular cavity compressed
-stays open for a bit so get a little bit of backflow


Respiration in fish -> countercurrent flow of water and blood

-Are two flows of blood -> first flow on lamella is in direct contact with water
-deoxygenated blood at back (afferent vessel -> goes arrives from body)
-blood moves through lamellae to front, where it gets oxygenated in efferent vessel)
-Blood gets oxygenated and moved away, so that constant diffusion occurs


Countercurrent Gas exchange in Fish -> efficiency of the system

-Very efficient, as small constant gradient is maintained
-Equilibrium is not reached, so diffusion continues to take place
-gas exchange maximised



-type of ventilation system young larvae use and adults

-Process of respiration (4)
-glottis, buccal cavity, lungs

-Yong (larvae) uses gills
-most adults use skin and simple lungs and use tidal ventilation
1. Air enters pocket of buccal cavity
2. Glottis opens, elastic recoil of the lungs and compression of chest will reduce lung volume
-air forced out of lungs and out the mouth
3. Mouth and nares close, floor of buccal cavity rises pushing air into lungs
4. Glottis closes, gas exchange occurs in lungs

*Complexity of lungs depend on type of frog


Reptiles (mainly lizards)

-How it works

-what can interfere with it

-Suction pump ventilates lungs
-2 phases; Inspiration and expiration
-uses intercostal muscles to control -> sometimes exercise interferes with breathing

*low surface area in lungs, but also low metabolic rates


Mammals and Birds

-extra requirements that contribute to structure

-Increased metabolic rate leads to increased demand for O2 and increased CO2 to be removed
-SA of respiratory membrane in lungs increased dramatically
-in mammals: numerous small alveoli
-in birds: parabronchi w/ numerous air capillaries


Avian Respiration

-features -> air sacs
-their purpose
-where gas exchange occurs

-Avian lungs are still w/ constant volume
-lungs connect with air sacs (most have 7-9 sacs)
-gas exchange does NOT occur in sacs -> expand and contract to move air through lungs
-Gas exchange occur at the parabronchi (w/in air capillary)
-fresh air flows unidirectionally
-air capillaries intertwine with blood capillaries to enable exchange to occur (is v. efficient) -> carry air from one parabronchus to another, passing blood capillaries


Avian Respiration -> Inhalation

-air sacs, caudal air sacs and cranial air sacs

-Air sacs expand due to muscles moving ribs and sternum out -> expands body cavity
-As caudal air sacs expand, air is drawn down the airways and into caudal air sac
-as cranial air sacs expand, air is drawn through the parabronchi and into the cranial air sac
-cranial airsacs draw O2 across the lungs for gas exchange


Avian Respiration -> Expiration

-Air sacs contract due to muscles moving ribs and sternum back in -> reduces size of body cavity
-Contraction of caudal air sacs pushes air out and into the parabronchi
-contraction of cranial air sacs pushes air out through the trachea

*Takes two cycles for a single breath of air to pass through the system


Mammalian Respiration

-where gas exchange occurs

-Pleural membranes -> features
-what fluid does (2)

-Gas exchange occurs in lower respiratory tract (alveoli)
Pleural membranes: each lung encased in its own double-walled pleural sac
-pleura made of single layer of squamous epithelial cells and C.T.
-space in between is intrapleural space -> contains fluid that;
1. Lubricates to permit frictionless movement
2. Prevents separation of pleurae (surface tension), holding lungs against thoracic cavity in a semi-inflated state (easier to inflate)


Ventilation in mammals (during inspiration and Expiration)

-What ventilation is

-Process of inspiration and expiration

Ventilation: Movement of air in and out of lungs
-muscle contraction -> expansion of thoracic cavity
-increased lung volume - decreased pressure in lungs
-air flows in lugs by bulk flow
-Muscle relaxation allows elastic recoil of thoracic cavity
-Decreased lung volume = increased pressure -> air flows out of lungs by bulk flow


Structures of Upper respiratory Tract;

-Nasal Cavities (4)
-3 functions

-Pair nasal cavities, separated by bony nasal septum
-hairs in nostrils
-ciliated epithelium w/ mucus-producing goblet cells
-Turbinate bones (conchae) increase surface area

-Clean air, warm air and moisten air (saturation with water vapour)


Structures of Upper Respiratory Tract;

-Oral cavity

-can by pass the nasal passages to breathe
-important during nasal obstruction and exercise
-but has limited heating, humidification and particle trapping


Structures of Upper Respiratory Tract;


-voice production

-Intricate framework of individual cartilages, muscle and C.T.
-Provides patent (open) airway, Prevents food and liquid entering trachea during swallowing, initiates cough reflex if food or liquids enter and voice production
-Epiglottis: Closes entrance to larynx during swallowing -> directs food to oesophagus
-Voice production: vocal cords or vocal folds housed in the arytenoid cartilages of larynx


Lower Respiratory Tract - 2 general portions


2 portions;
1. Conducting zone: continues warming, humidifying and cleaning air
2. Respiratory Zone: gas exchange
-Flexible tube of C-shaped cartilage rings -> keeps airway open
-lined with ciliated epithelium (function as mucus escalator to rid debris
-initiates cough reflex


Conducting zone: Bronchi/Bronchioles

-Terminal Bronchioles

-Bronchi: Trachea branches into primary bronchi
-contains supporting cartilage plates and mucus escalator
-Bronchioles: small airways, walls of smooth muscle -> contain NO cartilage
-mucus escalator
-Terminal Bronchioles: last anatomical structure in the conducting zones


Lower Respiratory Tract: Respiratory zone

-what it is the site of
-structures included
-2 things facilitate function

-site of gas exchange
-Includes respiratory bronchioles and alveoli
-Gas exchange maximised by;
large surface area and thin walls


Alveoli - types (3)

-Type 1 alveolar epithelial cells: form structure of alveoli; site of gas exchange
-Type 2 alveolar epithelial cells: Synthesizes surfactant
-Alveolar Macrophages: Patrol the inner surface of alveoli and ingest small foreign particles

*are millions of alveoli in each lung


Respiratory membrane

-Separates air from blood
-Comprised of; Type 1 alveolar epithelial cells, basement membrane and capillary endothelial cell
-Membrane is VERY thin!
-means very efficient gas diffusion


Surface tension and surfactant

-features of surfactant (5)

-Alveoli are lined with fluid that creates surface tension: Surfactant
-Detergent-like substance, disrupts cohesive forces between water molecules, reduces surface tension, prevents collapse of alveoli and reduces work of breathing
-made by type 2 alveolar cells


Surfactant deficiency w/ premature birth

-Production begins later during gestation
-babies born prematurely, they have insufficient surfactant
-increased work required to overcome surface tension
-difficulty breathing, may stop breathing


Avian vs Mammalian Respiration

-Avian lungs communicate w/ air sacs
-Avaian lungs rigid; volume changes
-air capillaries replace alveoli
-unidirectional flow of air (no dead ends); mammalian is tidal
-fresh air continuously flowing through avian lungs

*all enables birds to have adequate oxygen uptake at high altitudes


4 Pressures important in ventilation

1. Atmospheric pressure
2. Alveolar Pressure
3. Intrapleural Pressure
4. Transpulmonary Pressure (alveolar + intrapleural)


Alveolar Pressure

-what it is
-pressure when at rest
-when it varies (2)

-alveolar pressure at atmospheric during inspiration and expiration

AKA intra-alveolar pressure
-Represents the pressure of air w/in alveoli
-at rest (when not breathing in or out) = 760mmHg
*varies with phases of respiration due to
1. Changes in lung volume
2. Airflow into or out of lungs
*is the pressure that determines air flow into and out of lungs
-inspiration: alveolar pressure atmospheric


Intra-Pleural pressure

-what it is
-why it is what it is

-is the pressure inside the intra-pleural space
-Varies w/ phases of respiration
*is 756mmHg at rest (is negative relative to atmospheric pressure)
-arisies due to the opposing forces of chest wall and lungs

-Is always elastic because;
-Lungs and chest wall both elastic
-at rest, chest wall is compressed and wants to recoil outwards
-lungs are semi-inflated and want to recoil inward
*surface tension keeps them together


Transpulmonary Pressure

-Difference between alveoli and Intra-pleura pressure (+4mmHg)
-Represents the force that keeps the lungs distended
-increase in Ptp = larger distending force across the lungs and the lungs expand

*always positive under normal conditions -> alveoli expanded

Pneumothorax = when Ptp is zero
-leads to collapsed lung


Pulmonary Ventilation

-Muscles change volume of thorax -> Change in intrapleural pressure and transpulonary pressure -> Change in lung volume -> Change in alveolar Pressure -> Airflow


Muscles of Pulmonary Ventilation;



*2 each

External intercostal muscles: pull ribs up and out
Diaphragm: pulls down when it contracts

Internal Intercostal muscles: Pulls ribs inwards when contract
Abdominal muscles: Pull lower ribs inwards when they contract




-Changes in pressure that accompany process

Increased Neural input to inspiratory muscles -> diaphragm and external intercostal muscls contract -> Diaphragm moves down, sternum/ribs move up and out -> thorax expands, increasing volume

-Decrease in Pip leads to Increased transpulonary pressure -> lung volume increases (suction pulls lungs outwards) -> Decreased Palv creates pressure gradient, air flows into alveoli down gradient


2 types of expiration

-Passive Expiration: Does not require energy: involves relaxation of muscles
-occurs during quiet breathing
-Active Expiration: Requires energy, involves contraction of internal intercostal and abdominal muscles
-produces stronger, faster contraction
-important in exercise and disease


Expiration (quiet)

Decrease neural input to inspiratory muscles -> diaphragm and external intercostals relax -> volume of thorax reduces -> leads to increase in Pip and decreased transpulmonary pressure

Lung volume reduces by elastic recoil -> alveolar pressure increases -> air flows out down pressure gradient until Palv = Patm


Emphysema and expiration

-Destruction of alveolar walls due to chronic exposure to cigarette smoke
-elastic recoil of lung lost
-lungs easy to distend by difficult to empty
*patients must actively expire to prevent chronic over-inflation of lung


Dead space

-what it is

-3 types

-Dead space: Volume of inspired air that does not participate in gas exchange
*happens in tidal flow because a proportion of air doesn't get into alveoli
3 types;
1. Anatomical
2. Alveolar
3. Equipment or mechanical


Anatomical Dead Space

Alveolar Dead Space

Equipment Dead space

Anatomical: Air in URT and conducting zone that does not participate in gas exchange
-approx. 150ml in adult humans
Alveolar dead space: dead-space that exists within alveoli
-occurs when ventilated alveoli have no blood supply in adjacent capillaries
-negligible in healthy individuals, increased in lung disease
Equipment: Additional dead space added by breathing through equipment (e.g. face masks, snorkels, scuba gear)


Gas exchange in the lungs

-Primary driver of O2 and CO2 exchange is partial pressure gradient
-Each gas diffuses along its individual partial pressure gradient
-O2 diffuses into blood because PO2 is lower in blood (opposite is true for CO2)

*equilibrium is reached between air in alveoli and blood in lung capillaries


Gas exchange in tissues

-in terms of O2 and CO2

-Partial pressure in the vasculature -> where it changes

-PO2 in blood is greater than cells, so O2 diffuses from blood to cells
-PCO2 in cells is greater than in blood, so CO2 diffuses out of cells into blood

*Partial pressure remains the same until it gets to the cells


Gas transport in blood

-what it depends on

-3 ways CO2 transported

-Oxygen poorly soluble in blood - most is bound to haemoglobin inside RBCs
-amount bound depends on partial pressure of O2
-carbon monoxide competes with O2 (can happen with nitrate in cattle too)

-CO2 transported in blood via 3 ways;
1. Dissolved directly in blood (5-6%)
2. Bound to Hb in RBCs as carbaminohemoglobin (5-8%)
-binds to different part of Hb molecule so doesn't compete w/ O2
3.. As HCO3 in blood (86-90%)
CO2 + H2O -> H2CO3 + H + HCO3
-formation of bicarbonate ions occurs within RBC
-in lungs, reaction reverses (CO2 exhaled)


Changes in Ventilation

-Hyperventilation and Hypoventilation

-What they are
-What happens to O2 and CO2

-Hyperventilation: Too much breathing
-ventilation exceeds cell's requirements
-O2 builds and CO2 is depleted
Hypoventilation: too little breathing
-Insufficient ventilation to meet demands of cells
-O2 is depleted and CO2 builds up


CO2 and Acid-Base disturbances

-CO2 in blood leads to formation of H ions
*H determines pH of body

-Increased H ions leads to acidosis (low pH)
-Decreased H ions leads to alkalosis (high pH)



-what is it in terms of ventilation
-CO2 and O2 balance

-e.g. of what can cause it

-Condition it leads to

-Alveolar ventilation is insufficient to meet tissue's demands
-Cells continue to produce CO2 and consume O2
-Arterial PO2 falls below normal levels
-Arterial PCO2 increases above normal levels

e.g. Asthma and overdose on sleeping pills

*leads to acidosis (more CO2 = more H ions)



-what it is in terms of ventilation

-CO2 and O2 balance

-e.g. in what can cause it

-what it leads to

-Alveolar ventilation exceeds demands of tissues
-Excess CO2 is removed and excess O2 inspired for body's requirements

-Arterial PO2 increases above normal levels; artierial PCO2 falls below normal levels

e.g. fever, anxiety

-Leads to Alkalosis
*CO2 levels stimulates breathing (CO2 regulates respiration)