Gases and Respiration Flashcards
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
- Ventiation (by bulk flow)
- Gas exchange across respiratory membrane (by diffusion)
- O2 and CO2 transport in the blood (by bulk flow)
- Gas exchange in tissues (by diffusion)
Factors affecting Gas diffusion -> overview (4)
- Law that brings them all together
- 4 conditions where diffusion is greatest
- Surface area
- Diffusion Coefficient
- Partial pressure gradient
- 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
- is proportional to Solubility over square root of molecular weight
-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
- Emphysema
-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
- relationship
- 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
- determined mainly by the radius of airways
- 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
INSPIRATION:
-Muscle contraction expands thoracic cavity, increasing volume
-Lung pressure decreases
-Pressure gradient created, resulting in bulk air flow into lungs
EXPIRATION:
-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)
- concepts
- 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
- to diffuse into cell, must first dissolve in liquid
- 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
- features
- Large surface area for exchange
- Thin - small diffusion distance
- 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
- have all these features plus low metabolic demands
Aquatic Respiration
- features
- Fish Gills -> how they work
-Use gills for gas exchange
-large SA, highly vascularised, thin membranes that are frequently protected by coverings/flaps (Operculum)
FISH GILLS;
-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)
-Solution
- 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
Amphibians
-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
- Air enters pocket of buccal cavity
- Glottis opens, elastic recoil of the lungs and compression of chest will reduce lung volume
- air forced out of lungs and out the mouth
- Mouth and nares close, floor of buccal cavity rises pushing air into lungs
- Glottis closes, gas exchange occurs in lungs
- most adults use skin and simple lungs and use tidal ventilation
*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
INHALATION
- 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
- as cranial air sacs expand, air is drawn through the parabronchi and into the cranial air sac
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
INSPIRATION:
-muscle contraction -> expansion of thoracic cavity
-increased lung volume - decreased pressure in lungs
-air flows in lugs by bulk flow
EXPIRATION:
-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
Functions;
-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;
-Larynx
- epiglottis - voice production
-Intricate framework of individual cartilages, muscle and C.T.
Functions:
-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
-Trachea
2 portions;
1. Conducting zone: continues warming, humidifying and cleaning air
2. Respiratory Zone: gas exchange
TRACHEA
-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
- 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
Features;
-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
- increased work required to overcome surface tension
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
- Atmospheric pressure
- Alveolar Pressure
- Intrapleural Pressure
- 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
- Changes in lung volume
- 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
- value
- 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;
- Inspiration
- Expiration
- 2 each
Inspiration:
External intercostal muscles: pull ribs up and out
Diaphragm: pulls down when it contracts
Expiration:
Internal Intercostal muscles: Pulls ribs inwards when contract
Abdominal muscles: Pull lower ribs inwards when they contract
Inspiration
- process
- 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
- O2
- what it depends on
- poisoning
-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)
Hypoventilation
- 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)
Hyperventilation
- 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)
