Exchange surfaces and breathing

Question 1

Why is diffusion alone suitable for single celled organisms?

Answer 1

Metabolic activity of a single celled organism is usually low, O2 demands and CO2 production is low

They have a large surface area to volume ratio

Small distance for substances to travel

Question 2

Why do exchange surfaces have large surface areas?

Answer 2

Provides the area needed to overcome SA:V ratio, eg. villi

Question 3

Why do exchange surfaces have thin layers?

Answer 3

Diffusion distances are short, making process faster

Question 4

Why do exchange surfaces have a good blood supply?

Answer 4

The steeper the concentration gradient, the faster diffusion takes place. Good blood supply ensures that substances constantly delivered and taken from exchange surface, maintain steep conc gradient

Question 5

Why do exchange surfaces have ventilation to maintain diffusion gradient?

Answer 5

Same concept as good blood supply

Question 6

3 features of the nasal cavity?

Answer 6

Large surface area, with good blood supply, warms the air to body temp

Hairy lining, which secretes mucus to trap dust and bacteria, protecting lungs from infection

Moist surfaces, increasing humidity of incoming air, reducing evaporation from exchange surfaces

Question 7

Features of the trachea?

Answer 7

Carries air into chest

Supported by incomplete rings of strong flexible cartilage, stopping it from collapsing, but also allows food to move down oesophagus behind the trachea

Lined with ciliated epithelium with goblet cells, goblet cells produce mucus, and cilia beat it away from lungs

Question 8

Features of the bronchus?

Answer 8

each bronchus splits of from trachea into each lung

Question 9

Features of bronchioles?

Answer 9

The bronchi divide into lots of smaller bronchioles

They have no cartilage, and have smooth muscle instead. When it contracts they close, and when it relaxes they open

Lined with flattened epithelium

Question 10

Features of alveoli?

Answer 10

Tiny air sacs, have thin layer of epithelial cells, with collagen and elastin allowing them to stretch when air is drawn in, and return to resting size (elastic recoil)

Question 11

Main adaptations of alveoli for effective gas exchange?

Answer 11

Large surface area

Thin layers, (also capillaries)

Good blood supply

Good ventilation

Question 12

What is lung surfactant?

Answer 12

Solution of water and salts covering inner surface of alveoli, allows alveoli to remain inflated

Question 13

What occurs in inspiration?

Answer 13

Diaphragm contracts, flattening and lowering

External intercostal muscles contract, moving ribs upwards and outwards.

Volume of thorax increases, so pressure is reduced so air is drawn in

Question 14

What occurs in expiration?

Answer 14

Diaphragm relaxes, moving up into dome shape, 
intercostal muscles relax
Ribs move down and inwards
Volume of thorax decreased
Pressure increased
Air forced out

Question 15

What does a spirometer do?

Answer 15

Measures the amount of oxygen in the lungs

Question 16

What’s the tidal volume?

Answer 16

Volume of air that moves in and out of lungs with each resting breath (around 500cm^3)

Question 17

What’s the vital capacity?

Answer 17

Volume of air that can be breathed in when strongest exhalation is followed by strongest inhilation

Question 18

What’s the inspiratory reserve volume?

Answer 18

Maximum volume of air you can breathe in over and above a normal inhalation

Question 19

What’s expiratory reserve volume?

Answer 19

Extra amount of air you can force out of you lungs above normal tidal volume

Question 20

what is Residual volume?

Answer 20

Volume of air left in lungs when you have exhaled as hard as possible

Question 21

What is total lung capacity?

Answer 21

Sum of vital capacity and residual volume

Question 22

What is the ventilation rate?

Answer 22

tidal volume x breathing rate per min = total volume of air inhaled in one min

Question 23

Features of spiracles in insects?

Answer 23

Along the thorax and abdomen of insects there are small openings known as spiracles

Air enters and leaves the system through the spiracles, but water is also lost

Spiracle sphincters open and close spiracles, but keep them closed most of the time to reduce water loss

Spiracles lead into trachea

Question 24

What are trachea in insects?

Answer 24

Tubes which carry air into the body

Lined by spirals of chitin, keeping them open

Splits into tracheoles

Question 25

What are tracheoles in insects?

Answer 25

Smaller diameter than trachea

No chitin so gas exchange can take place, as the tracheoles pass through the tissues

When there’s higher oxygen demand a lactic acid build up in the tissues results in water moving out of tracheoles via osmosis, exposing more surface area for gas exchange

Question 26

What’s mechanical ventilation?

Answer 26

Air is actively pumped into the system or out by muscular pumping of thorax/abdomen

Question 27

What are collapsible enlarged trachea or air sacs?

Answer 27

They act as air reservoirs, and increase the amount of air moved through gas exchange system

Question 28

Advantages and disadvantages a fish’s respiratory system faces?

Answer 28

ADV:
Don’t need to worry about water loss
DIS:
Water has much lower oxygen content, and harder to move throug

Question 29

What are gills?

Answer 29

Water flows in one direction over the gills, allowing Oxygen to be taken in and CO2 removed

Contained in a gill cavity and covered by a protective operculum

Question 30

What are gill lamellae?

Answer 30

Main site where gas exchange takes place in gills

Question 31

What are gill filaments?

Answer 31

Need water flowing through them to expose large surface area for gas exchange

Question 32

How do bony fish maintain water flow over gills when they stop moving?

Answer 32

Mouth opens increasing volume of buccal cavity, pressure drops, so water moves into it

Same time operculum valve shuts and cavity containing gills expands lowering pressure

Buccal cavity moves back up, increasing pressure so water flows over gills

Question 33

Gills extra adaptations which allow good gas exchange in water?

Answer 33

Tips of adjacent filaments overlap, increases the resistance against the flow of water, so longer for gas exchange to occur

Water flowing over gills and blood in gill filaments move in opposite directions, meaning that the steep concentration gradient is maintained as much as possible

Question 34

What does tracheal fluid do?

Answer 34

Limits the penetration of air for diffusion

Question 35

What’s a counter current system?

Answer 35

Blood and water move in opposite directions

Question 36

What’s a parallel system?

Answer 36

Blood and water move in same direction