Exchange surfaces Flashcards
1
Q
reasons for exchange systems
A
- large multicellular organisms have a small surface area to volume ratio
- cells in the centre of organisms wouldn’t receive any materials if they relied on diffusion alone
- multicellular organisms have a high metabolic rate so they need to exchange lots of materials fast
2
Q
features of an efficient gas exchange system
A
- large surface area
- thin layers
- good blood supply - maintains conc. gradient and ensures substances are constantly moving to area needed
- ventilation - maintains diffusion gradient
3
Q
pleural cavity
A
- each lung is enclosed in a double membrane known as a pleural membrane
- space between 2 membranes is called pleural cavity and is filled with pleural fluid
- fluid lubricates lungs and adheres outer walls of lungs to the chest cavity by cohesion so the lungs expand with the chest when breathing
4
Q
functions of nasal cavity
A
- larger surface area and good blood supply - warms the air as it passes into the body
- hairy lining - taps dust and bacteria in mucus to prevent them reaching lungs
- moist surfaces - increases humidity of incoming air - reduces evaporation of water in lungs
5
Q
how is the trachea adapted to be efficient in gas exchange?
A
- supported by layer of cartilage holding it open and preventing it collapsing
- rings of cartilage are incomplete to allow it to bend when food is swallowed in the oesophagus behind
- lined with ciliated epithelial (beat regularly moving bacteria along with mucus) and goblet cells (secrete mucus) that prevent dust and bacteria entering
6
Q
bronchus
A
- extensions of trachea that split into 2 for each lung
- similar structure to trachea but smaller
- cartilage rings hold pipe open
7
Q
bronchioles
A
- bronchus split into much smaller tubes - 1mm or less diameter
- no cartilage - held open by smooth muscle
- muscle contracts and bronchioles contract - dependent on air flow
- lined with thin layer of epithelial tissues making some gas exchange possible
8
Q
how are alveoli adapted to function?
A
- little air sacs about 200-300 micrometers diameter
- made of thin layer epithelial cells and some collagen and elastic fibres
- elastic fibres cause recoil helping air move out of alveoli
- lung surfactant - a phospholipid coating surface of lungs preventing alveoli from collapsing from the surface tension
9
Q
inspiration
A
- diaphragm moves down
- intercostal muscles move up and out
- thoracic volume increases
- thoracic pressure decreases
- air flows into lungs to equalise pressure difference
- active
10
Q
expiration
A
- diaphragm moves up
- intercostal muscles move down and in
- thoracic volume decreases
- thoracic pressure increases
- air flows out of lungs to equalise pressure differences
- passive
11
Q
how do you use a spirometer?
A
- lower half of tank filled with water
- upper half full of oxygen
- breathe out into tank and upper half will rise
- breathe in from the tank and upper half will fall
- trace marker attached to mobile upper half
12
Q
why does the overall volume of the tank decline over time?
A
- sod lime absorbs carbon dioxide
- when breathing we use up oxygen from tank while carbon dioxide we breathe out is absorbed by soda lime
- gas volume of tank decreases because oxygen is used up by ppt
13
Q
precautions when using spirometer
A
- patient free from asthma and healthy
- soda lime fresh and functioning
- check for air leaks in apparatus
- sterilise mouthpiece
- don’t overfill water chamber
14
Q
tidal volume
A
- amount of air moving in and out of lungs during breathing at rest (smallest wave)
15
Q
inspiratory reserve volume
A
- how much extra air breathed in during forced inspiration (large wave going down)
- measure inspiratory capacity above tidal volume
- uses extra muscles
