Gas Exchange Flashcards
What are the two types of respiration?
Internal
- biochemical processes
- make energy available to cells
External
- exchange of gases (oxygen to tissues and cells and removal of CO2)
Which physical factors influence the rate of diffusion?
- partial pressure gradient
- diameter of gas molecules
- temperature (warmer = faster diffusion)
- solubility of gas in liquid (atmospheric gases need to dissolve into the body)
- thickness of the gas exchange surface (thinner = faster diffusion)
- surface area of the gas exchange surface (larger SA = faster diffusion)
How to work out the rate of diffusion
Fick’s law
Q = D A [(Pe - Pi)/L]
Q = rate of diffusion D= diffusion coefficient (diameter of gas molecule, temp, solubility of gas in liquid) Pe-Pi = partial pressure difference L = thickness of interface
Partial pressure
Pressure of a single gas in a mixture
What environment conditions affect O2 availability
- decreases with increased altitude
- air is better respiratory medium than water: more O2 per unit volume and diffuses faster
- decreased solubility of O2 with increased temp
- turbulent water increases O2 availability
What are the 3 main parts to a respiratory system in an animal?
- specialised body surfaces for gas exchange
- mechanisms to ventilate environmental face of surface
- mechanisms to permeate internal face of surface
How can org have no respiratory system (+e.g.)
- all cells of org must be in direct contact with cell surface (or very close)
- only effective in simple, small orgs
E.g. sponges
What are the 4 types of respiratory organs?
- external gills (aquatic enviro..many have protective case that prevents harm)
- internal gills
- lungs
- trachea
(Last 2 kept in body which keep moisture)
How is gas exchange maintained in liquid environments
- gills highly branched and folded extensions of the body.. evaginations = maximised SA
- thin tissue to minimise diffusion path length
- new medium flows continuously over surfaces (e.g. water over gills = O2 supply)
How is gas exchange maintained in gaseous environments
- invaginations for protection of respiratory surface = increased internal surface area
- thin tissue to minimise diffusion path length
- lungs are elastic = increased capacity
- kept moist inside the body
Describe the main structures of the human respiratory system
Upper respiratory tract = nosal cavity, pharynx, larynx
- trachea = branches to form primary branches (these branches repeat 23): bronchi, bronchioles, terminal bronchioles, respiratory bronchioles
- lungs = spongey mass: contains air sacs with single cell walls (alveoli) alveolar ducts, alveolar sacs
- ribs = protect lungs and gives structure to thorax
- intercostal muscles = change shape of thorax and move ribs
- diaphragm = separates abdomen from thorax: controls volume of thorax
Respiratory zone
Where gas exchange takes place in respiratory system (O2 to blood, CO2 taken from blood)
- respiratory bronchioles, alveolar ducts, alveolar sacs
Dead zone/ conducting zone
Area of no gas exchange in respiratory system
- trachea, bronchi, bronchioles, terminal bronchioles
- no alveoli = no gas exchange
- brings air in from atmosphere: warmth, humidity, filters = facilitates respiration still
Tidal volume
Normal breathing
- can very between people
Vital capacity
Largest in and out breath
Inspiratory reserve volume
The difference between tidal and vital when breathing in
Expiratory reserve vol
Difference between tidal and vital when breathing out
Residual volume
- Air that always remains in the lungs
- prevents lungs collapsing
- reservoir of O2
- mixes with incoming gas
Functional residual capacity
Air remaining after normal tidal expiration
Alveolar ventilation rate
Vt = Vd + Va Vt = tidal volume Vd = dead space ventilation Va = alveoli ventilation (tidal - dead space x breathing rate) : can be increased by increasing tidal volume or respiratory frequency - dots over them = rate
Primary role of respiratory system
Meet metabolic demands of organism
How does ventilation occur?
- active muscle force is applied to relaxed respiratory system
- convection of respiratory medium over gas exchange surfaces (active or passive)
- movement maintains partial pressure gradient at respiratory interface
- fresh O2 delivered, CO2 removed
Interpleural space
- Lung encased in plural membranes including the inside cell wall creating a closed space around the lungs
- binds lungs together and keeps them open
Describe inspiration
- active process
- volume of thorax increases
- diaphragm contracts = flattens (tidal breathing may flatten by 1cm vs exercise may be 10cm)
- external intercostal muscles contract
Intrapleural pressure
Pressure around alveoli
- inside alveoli is atmospheric pressure
- if pressure outside alveoli becomes more negative they expand further
Boyle’s law
P1V1 = P2V2
P=pressure
V=volume
Pressure and volume is constant
What happens when the volume of the thorax increases
-intrapleural pressure falls
-alveoli expand
-alveolar pressure < atmospheric pressure
-air flows into the lungs until alveolar pressure = atmospheric pressure
Passive process
Describe expiration
Passive process
- elastic recoil of lungs and chest wall reduces volume of thorax
- intrapleural pressure rises
- alveoli recoil
- alveoli pressure > atmospheric pressure
- air expelled from lungs
At which 2 points is respiration static
- functional respiratory capacity (just before breathing in)
- peak of inspiration (just before breathing out)
What is compliance and its equation
Compliance is how stretchy the lungs are
Compliance = change in volume/change in pressure
What happens to compliance curve during inspiration
- deviates right
- due to airflow resistive forces
What airflow resistive forces take place during inspiration
- airflow tubes getting narrower
- plural membranes rub against each other causing friction..when lungs expand friction has t be overcome (pleural fluid lubricates.. but if inflamed membranes then friction increases)
- goes from static to dynamic which requires inertia (coughing/sneezing requires even greater inertia)
What happens to the compliance curve during expiration
- deviates left
- resistive forces assist airflow
How do resistive airflow forces assist expiration?
- elastic recoil of lungs and chest wall
- surface tension in alveoli
- expiration can be active (internal intercostal and abdominal muscles contract)
Describe avian ventilation process
- First breath drawn into posterior air sacs
- Exhalation causes air to cross lungs
- Air pushed from lungs into anterior air sacs during second inhalation
- Air released during second exhalation
How is air birds specialised four avian respiration
Unidirectional flow
Lots of capillaries = increased SA
Little dead space = can fly at high altitudes
Short trachea
How does avian respiration differ from mammals?
Little change in lung volume
Lungs are inelastic
Lungs are surrounded by air sacs that dont play a role in gas exchange
Wing movement compresses lungs (however not crucial for respiration)
Describe frog ventilation
- Air enters the frog
- Glottis closes and forces air into the lungs
- Mouth opens
- Mechanical contraction forces air out of the lungs
There is a positive pressure gradient = air forced into the lungs
Describe insect ventilation
- Open airway system
- Each segment has a spiracle
- Air moves passively by diffusion
- Abdominal muscles pump air through the trachea
Describe fish ventilation
- operculum cavity opens and the opercular flaps expand
- Water is pushed over the gills when the buccal cavity closes
- Uses pressure gradient and active process to close mouth
Counter current mechanism
What is pouseuillies law
V= P pi r ^4 / 8nl v = flow rate P = pressure gradient R = airway radius Nl = airway length
Describe laminar flow
Slow flow rate
Parallel stream lines
Describe turbulent flow
High flow rate
Disorganised stream lines
Happens with narrow airways and a high flow rate
Describe transitional flow
Happens when airway dividing
Intermediate flow rate
Edgy currents
What can affect airway resistance
Radial traction Inflammation and mucus Dynamic compression Bronchiole constriction Bronchiodilation
Describe radial traction
When the lungs expand
Describe inflammation and mucus of airways
Infection can increase Raw by:
- inflaming the tissue linings of the upper airway has
- over/under production of mucus
Describe dynamic compression
If there is a low lung volume or if the intrathoracic pressure > alveolar pressure = airways may close and compress
Describe bronchioconstriction
Increases Raw Irritant = reflex constriction Parasympathetic stimulation Fall in Pco2 Asthma
Describe bronchiodilation
Decreases Raw
Autonomic stimulation
Sympathomimetic stimulation
Drug = bronchiodilators
Describe surface tension in the alveoli
Alveoli filled with liquid, they have attractive forces that oppose expansion by inspired air = smaller alveoli collapse
Fluid moves into the alveoli from the capillaries
Problems minimised by surfactant
Describe pulmonary surfactant
Surfactant = phospholipoprotein
Secreted by type 2 alveolar cells
Low surface tension
Prevents alveolar collapse at low pressures
Describe systemic circulation.
Blood supply to all body expect lungs
- returns to heart co2 rich and o2 poor
Describe pulmonary circulation
Goes to lungs
Pulmonary artery blood the same as in the RA
Pressure and vascular resistance low
Vascular resistance equation
(Input pressure - output pressure) / blood flow
Describe gravity’s affect on ventilation of the lungs
Intrapleural pressure is greater at the apex (alveoli bigger)
Atmospheric pressure remains constant
Describe gravities affect on perfusion of the lungs
blood pressure is greater at the base of the lungs
At the apex Palv> Pa> PV
At the bottom Pa>PV>Palv
How can the ratio of ventilation:perfusion optimise gas exchange
V:Q
=0: blood not in contact with alveolar air
= infinite: anatomical dead space/ventilated alveoli not perfused
How can an equal ventilation:perfusion ratio be maintained
Through vasoconstriction:
- blood directed away from poorly ventilated areas
- in systemic circulation = airways relax and allow blood to flow, taking away the o2
Keep airways and blood vessels in close proximity: composition of gases between them stay constant
Describe myoglobin
O2 reservoir
Only released when levels are low
Describe haemocyanin
Same as haemoglobin but with copper instead of iron
What are the 4 main lung receptors
Stretch receptors
J receptors (juxta-pulmonary)
Irritant receptors
Proprioreceptors
Describe stretch receptors
Mechano-sensitive (is lung inflated)
In bronchiole wall
Regulates length of inspiration
Important in baby’s first breath
Describe j receptors
In alveoli wall
Changes pulmonary circulation e.g. flow rate, pressure
Stimulation = contraction
Describe irritant receptors
In airways
Causes cough = expels irritant
Relaxes diaphragm
Describe proprioreceptors
Sensitive to position in space
Info of chest wall sent to brain stem
= inspiration
What’s hypoxia
Reduced Po2
What’s hypercapnia
Reduced Pco2
Described the diving reflex in mammals
Diving mammals have o2 reserves in muscles And increased red blood cell count (have increased haemoglobin in RBCs as well) = greater o2 carrying capacity
Cold water on face triggers reduced heart rate, increases peripheral vasoconstriction and causes lactate to accumulate in muscle
Where do neurons fire for inspiration
Pre-botzinger complex
Where do neurons fire for pre inspiration/expiration
Neurotrapezoid nucleus / para facial respiratory group
