Human Gas Exchange Flashcards
Describe the structure of the human gas exchange system.
- pair of lungs: where gas exchange occurs
- trachea: airway supported by rings of cartilage (prevents collapsing from pressure changes) + lined w ciliated epithelium + goblet cells (trap + remove dust/bacteria). Splits into 2 bronchi
- bronchi: similar structure to trachea + splits into bronchioles
- bronchioles: narrow tubes w alveoli at end
- alveoli: tiny air sacs surrounded by capillaries that have thin walls + a large SA
Describe how to prepare a slide (for observation under an optical microscope) using a solid specimen.
- cut a thin layer of cells from a tissue sample using forceps + place on a slide
- add drop of a stain if needed to make structure visible
- place a coverslip on top + press down to remove any air bubbles
Describe how to use a graticule to take measurements of cells.
- place graticule into eyepiece of a microscope
- calibrate graticule using a stage micrometer
- use both scales to work out NO° of micrometers in each graticule unit
What is the purpose of a 3-way tap?
- allows repeat readings to be taken easily when using potometers (air bubble returned to start of tube) + respirometers (bead of liquid returned to start)
Describe how the alveoli are adapted to facilitate rapid gas exchange.
- large NO° of alveoli inc SA so O2 can diffuse out of alveoli into blood + CO2 can diffuse into alveoli from blood
- alveoli epithelium cell walls are 1 cell thick to create a short diffusion distance
- alveoli surrounded by capillary network w constant blood flow that removes exchanged gases to maintain conc gradient
Describe inspiration/inhalation of air into the lungs.
- when external intercostal muscles contract + internal intercostal muscles relax, the ribs are pulled upwards + outwards
- the diaphragm muscles also contract, causing it to flatten, inc. volume of thorax
- this dec. pressure in lungs, forcing air into lungs as atmospheric pressure is > lung pressure
Describe expiration/exhalation of air out of the lungs.
- when internal intercostal muscles contract + external intercostal muscles relax, the ribs are pulled downwards + inwards
- the diaphragm muscles also relax, causing it to return to its dome shape, dec. volume of thorax
- this inc. pressure in lungs, forcing air out of lungs as atmospheric pressure is < lung pressure
What is the tidal volume?
- volume of air that enters + leaves lungs when at rest (0.5cm3)
What can be used to measure lung capacity?
- spirometer
What is the vital capacity?
- max volume of air we can inhale + exhale
What is the residual volume?
- volume of air left in lungs after strongest exhalation
What is the pulmonary ventilation rate?
- total volume of air moved into lungs during 1 minute (dm^3min^-1)
How do you calculate the pulmonary ventilation rate?
- PVR = tidal volume (dm3) x ventilation/breathing rate (min-1)
Why do diseases such as bronchitis + asthma dec gas exchange?
- bc it causes narrowing of lumen so less air can enter + leave alveoli = lower conc gradient so less O2 is delivered to alveoli for gas exchange
How does smoking affect gas exchange?
- tar helps break down alveoli walls so dec the SA:V ratio, dec gas exchange so less O2 diffuses into blood
- tar can form a layer on alveoli, inc diffusion distance for gas exchange
What should be taken into account when analysing data from studies on health risk factors?
- sample size: larger sample size = more reliable results
- individuals in sample: male/female or age
- lvls of exposure: high exposure may have diff effect to low exposure
- if a statistical test has been carried out to test significance of results
- influence of other factors: genetics/secondary exposure to risk factor/exercise (correlation doesn’t prove causation)
