7- exchange surfaces and breathing

Question 1

why is diffusion alone enough to supply for a unicellular organism?

Answer 1

• its metabolic activity is usually ↓, ∴ O2 demands & CO2 prod = ↓
• SA:V = ↑

Question 2

why can’t multicellular organisms rely on diffusion alone?

Answer 2

• greater metabolic activity, ∴ O2 and CO2 need to be prod/removed at a faster r8
• small SA:V ∴ gases can’t be xΔed fast enough or in ↑
  quants 4 the org 2 survive

Question 3

what 4 features do all effective xΔ SAs have in common? + examples

Answer 3

1) increased SA
- root hair cells & villi in sm intestine
2) thin layers
- alveoli in lungs & villi in sm intestine
3) good blood supply
- above & gills on fish
4) good ventilation
- gills on fish

Question 4

how does an increased SA help xΔ?

Answer 4

it overcomes the ↓ SA:V in ↑ orgs

Question 5

how do thin layers help xΔ?

Answer 5

they ↓ diffusion dist ∴ it = a ↑ fast & efficient process

Question 6

how does a good blood supply help xΔ?

Answer 6

maintains a steep concgrad (=↑ r8) 4 diffusion thru the quick supply & removal of gases

Question 7

how does good ventilation help xΔ?

Answer 7

maintains a steep concgrad (=↑ r8) 4 diffusion thru the quick supply & removal of gases

Question 8

why do mammals have a ↑ metabolic r8?

Answer 8

• they’re active
• they maintain their body temp indep fr/ the environ
  ∴ they need lots of O2 (4 cellular resp) & prod CO2 wh/ needs removing–> the xΔ of these gases occurs in the lungs

Question 9

what are the 5 cell and tissue structures involved w/ the lungs & where are they found?

Answer 9

1) ciliated epithelium– trachea walls, bronchi, bigger bronchioles
2) goblet cells- trachea, b/w the epithelial cells
3) smooth muscle- trachea cells, bronchi, larger bronchioles
4) elastic fibres (composed of elastin)- trachea walls, bronchi, all bronchioles, alveoli
5) squamous epithelial cells- capillaries, alveoli

Question 10

what does the ciliated epithelium do?

Answer 10

the cilia beat & move mucus away from the lungs

Question 11

what do the goblet cells do?

Answer 11

they secrete mucus on2 the trachea lining wh/ traps dust & microbes wh/ escape the nose lining

Question 12

what does the smooth muscle do?

Answer 12

when it contracts–> broichioles constrict (close) & when it relaxes, the bs dialate (open) wh/ Δs the am of air entering the lungs

Question 13

what do the elastic fibres do?

Answer 13

• allow alvs to stretch as air = drawn in

- when they return to their resting size, they squeeze the air out = the elastic recoil of the lungs

Question 14

what do the squamous epithelial cells do?

Answer 14

↑ diffusion r8 bc they’re v/ thin, also making diffusion ↑ efficient

Question 15

what are the 5 key structures of the lung system ?

Answer 15

1) nasal cavity
2) trachea
3) bronchus
4) bronchioles
5) alevoli

Question 16

what are the key features & functions of the nasal cavity?

Answer 16

• ↑ SA wh/ a good blood supply
• warms air 2 body temp
• hairy lining wh/ secretes mucus
• traps mucus & bacteria, protecting the lungs fr/ irritation & infection
• moist SAs, ↑ing the humidity of incoming air
• ↓ing evap fr/ the xΔ SAs

Question 17

what are the key features & functions of the trachea?

Answer 17

*supported by incomplete rings of cartilage
- cartilage= strong & flex = stops trachea fr/ collapsing
-incomplete rings= so food can move w/ ease ↓
the oesophagus behind the trachea
*trachea & its branches = lined w/ cilliated epi + goblet cells

Question 18

what are the key features & functions of the bronchus?

Answer 18

• sim in struct 2 the trachea, w/ the same supporting rings of cartilage
• smaller than trachea tho

Question 19

what are the key features & functions of the bronchioles?

Answer 19

• walls contain smooth msucle – no cartilage rings

* lined w/a layer of flattened epithelium

Question 20

what are the key features & functions of the alveoli? (LONG)

Answer 20

• consists of a alyer of thin, flattened epi cells w/ some collagen
• • elastic fibres (composed of elastin)
• large SA
• lots of O2 req 2 diff in the body
• thin walls- onlya cell thick
• ↓ diffdist b/w air in alveoli & the blood in the capillaries
• good blood supply from the network of over 200 mill capillaries
• constant flow of blood thru capils ∴ maintains a steep concgrad 4 O2 & CO2 b/w air in alvs and capils
• good ventilation via breathing, wh/moves air in and out of the alv
• maintains a steep concgrad 4 O2 & CO2 b/w air in alvs and capils