Exchange Surfaces

Question 1

Why are specialised exchange surfaces needed

Answer 1

If there is low surface area to volume ratio organisms can’t rely on diffusion alone.

Larger multicellular organism have higher metabolic activity meaning they require more o2 and CO2 which diffusion alone can’t provide efficiently

Question 2

Features of an efficient exchange surface

Answer 2

Increased surface area - root hair cells
Thin layer - alveoli
Good blood supply/ventilation to maintain gradient

Question 3

Steps of inhalation

Answer 3

• Diaphragm contracts and flattens
• External Intercostal muscles contract which lifts the rib cage
• This leads to an increase volume and lowers pressure, as air pressure is lower than the out side air rushes in across a pressure gradient.

Question 4

Steps for exhalation

Answer 4

• As diaphragm relaxes, it lifts
• External intercostal muscles relax losing the rib cage
• This decreases volume and increases pressure to air is pushed out as pressure inside is greater than pressure outside

Question 5

Features in a Trachea

Answer 5

-c shaped cartilage reduces resistance in air flow but also prevents it from collapsing. It also allows flexibility and stops it from bursting.
-ciliated epithelium cells with goblet cells
Goblet cells secrete mucus and ciliates epithelial cells waft the muscles with trapped dirt up so it can be swallowed
-has smooth muscle, elastic fibres as well.

Question 6

Features of bronchi

Answer 6

The trachea divides into bronchi leading to the left lung and right lung.
They have c shaped cartilage like the trachea but are smaller.
Has smooth muscle, elastic fibres and goblet cells as well.

Question 7

Features of bronchioles

Answer 7

They have no c shaped cartilage but the walls contain smooth muscle.
When smooth muscle contracts the bronchioles constrict. When it relaxes bronchioles dilate and open up. This controls the diameter and the volume of air reaching the lungs.
Has elastic fibres

Question 8

Features of the alveoli

Answer 8

Are tiny air sacks where gases are exchanged.
They contain elastic fibres which inflate and stretch breathing in and when breathing out the fibres recoil to help push air out.
They have a large surface area to volume ratio, good blood supply for steep gradient and thin layers.

Question 9

What is tidal volume

Answer 9

Volume of air in each breath

Question 10

Vital capacity

Answer 10

Maximum volume of air that can be breathed in or out

Question 11

Breathing rate

Answer 11

How many breaths are taken per unit time

Question 12

Oxygen uptake

Answer 12

The rate at which a person uses up oxygen

Question 13

Residual volume

Answer 13

Is volume of air left in your lung when you have exhaled

Question 14

What is total lung capacity

Answer 14

Is vital capacity + residual air

Question 15

What does soda lime do

Answer 15

It absorbs carbon dioxide from expelled air

Question 16

Ventilation in insects

Answer 16

• there are spiracles along the thorax and abdomen, these are opened and closed by sphincters.
• leading away from the spiracle are trachea which are lined with spirals of chitin. Chitin is relatively impermeable to gas.
• trachea branch off into tracheoles, they have no chitin lining and gas is exchanged
• at the end of tracheols there is tracheal fluid which prevents diffusion. When there is a build up of lactic acid tracheal fluid moves out leaving a greater surface area for gas exchange. Lactic acid creates a steep gradient as well.

Question 17

How do insects ventilate

Answer 17

Insects use movement to change volume in the abdomen and thorax to change pressure. When pressure is Low air rushes in across a pressure gradient.

Question 18

How do fish ventilate

Answer 18

Fish constantly open and close it operculum to act as a pump lowering the bucal cavity increasing and decreasing pressure.

Question 19

How does counter current exchange work

Answer 19

• high oxygen blood meets high oxygen water
• low oxygen blood meets low oxygen water
• this maintains a constant concentration gradient so diffusion occurs across the entire length

Question 20

Adaptation to gills

Answer 20

Each gill consist of rows called gill filament and each gill filament have second lamellae. This increases surface area.

Question 21

Adaptations for effective gaseous exchange in fish

Answer 21

Counter current
Tips of adjacent gills overlap which increase resistance to the flow of water. This gives more time for gaseous exchange.