ch7 - exchange surfaces & human gas exchange system

2 reasons why organisms have to exchange substances

to deliver oxygen to cells so aerobic respiration can occur - releasing energy for cellular processes

to remove waste products e.g. CO2 from cells - build up can be dangerous and toxic

> build up of CO2 reduces pH which can denature enzymes

small organisms are ..

single celled

large organisms are …

multicellular

small organisms have a .. sa:v ratio & explain what this means and the diffusion that takes place

large sa:v ratio meaning there is a short diffusion distance between the outside to the middle of organism

> hence simple diffusion through surface of their body can take place because it is sufficient to meet metabolic demands of oxygen

large organisms have a .. sa:v ratio & explain what this means

small sa:v ratio meaning there is large distance between outside to middle of organism

> require specialised exchange surfaces to meet high metabolic demands of oxygen because simple diffusion would be too slow

what are the 4 features of an efficient gas exchnage system

-large surface area

-thin layers

-good constant blood supply

-ventilation

explain why each of these features is useful

large surface area = large area for exchange of gases

thin layers = provides short diffusion distance

good constant blood supply = maintains steep concentration gradient

ventilation = maintains steep conc gradient by ensuring o2 is higher in alveoli and co2 is lower in alveoli = faster diffusion

what is the journey of the human gas exchange system

nasal cavity > trachea > bronchus > bronchioles > alveoli

a features of the nasal cavity

-lined with ciliated epithelium which has:

ciliated epithelial cells with cilia, hair like projections, that move mucus produced by goblet cells which trap dust and pathogens

2 features of the trachea

-c shaped rings of strong flexible cartilage to:

keep trachea open prevent it collapsing

-lined with ciliated epithelium which has :

ciliated epithelial cells with cilia, hair like projections, that move mucus away from lungs produced by goblet cells which trap dust and pathogens

trachea divides to form 2 ..

bronchi

difference between bronchus and bronchi

bronchus is plural for left and right lungs

bronchi refers to individual left or right lung

a features of bronchus

-c shaped rings of strong flexible cartilage to:

keep bronchi open and prevent it from collapsing

difference between the c shaped rings of cartilage in trachea and bronchus

in the bronchus the cartilage is much smaller

each bronchi divides to form many …

bronchioles

3 features of bronchioles

-very thin 1mm thick

-lined with squamous epithelium which has squamous epithelial cells which provide short diffusion pathway

-lined with smooth muscle that relaxes and contracts allowing lumen to dilate when lots of air is needed and constrict when little air is needed

where is the alveoli found

at the end of the bronchi

what is the function of the alveoli

site of gas exchange

-O2 diffuses from alveoli across the capillaries into the blood

-CO2 diffuses from blood across the capillaries into alveoli

5 features of alveoli

-thin walls 200-300micrometers thick = provides short diffusion pathway

-lined with squamous epithelium made of flattened squamous epithelial cells = provide short diffusion pathway

-made of elastic fibres which contain elastin allowing alveoli to stretch and recoil as air moves in and out so alveoli don’t burst

-network of capillaries around each alveoli = provides good blood supply to maintain steep conc. gradient

-huge amounts of alveoli = provide large SA for diffusion of gases