M3- Chapter 7 - Exchange surfaces and breathing

Question 1

Why can microscopic animals exchange gases through diffusion

Answer 1

They have a low metabolic activity and a low demand for oxygen. Even then, their walls are thing enough that gases can travel through quick enough.
They have a large SA:V ratio

Question 2

Why can’t larger animals exchange gases through just diffusion

Answer 2

They have more cells, tissues and organs that all need more energy, hence a higher demand for oxygen. This is because they have a higher metabolic activity. The bigger the organism, the smaller their SA:V ratio, hence diffusion can’t handle the pressures of such demands.

Question 3

What are the 4 things that make an effective exchange surface?

Answer 3

1. Increased SA
2. Thin layers
3. Good blood supply
4. Ventilation to maintain concentration gradient

Question 4

How does good blood supply help create an effective exchange surface?

Answer 4

Having a steeper concentration gradient created faster diffusion. Having constant good blood supply allows that there is always a good concentration gradient.

Question 5

How does ventilation to maintain a concentration help create an effective exchange surface?

Answer 5

It makes the process more efficient overall.

Question 6

What are the main features of the nasal cavity

Answer 6

• Large SA: V ratio
• Good blood supply (warms the air to body temperature)
• Hairy lining (mucus)
• Moist surfaces (increasing humidity of the incoming air)

Question 7

Main features of trachea

Answer 7

• It carries the air from the nose down to the chest
• It has incomplete ‘C’ shaped, cartilage rings that provide support and flexibility
• It’s lined with ciliated epithelium cells and goblet cells that secrete mucus. Also has cilia

Question 8

Bronchus features

Answer 8

The trachea then splits into 2 to form 2 bronchi. They have c-shaped cartilage.

Question 9

Bronchioles

Answer 9

Don’t have cartilage

They have smooth muscle.

Question 10

When the smooth muscle in bronchioles relax what does that do to the air flow

Answer 10

Bronchioles open up

Question 11

When the smooth muscle in bronchioles constrict what does that do to the air flow

Answer 11

Bronchioles close up

Question 12

What is inside bronchioles

Answer 12

A layer of flattened epithelium and goblet cells.

Also smooth muscle

Question 13

Alveoli

Answer 13

They are like tiny air sacks, each with a diamete of 200–300 ym.
Each alveoulus contains:
thin flattened epithelial cells
collagen and elastic fibres.

Question 14

What is elastic recoil

Answer 14

Elastic tissues allow alveoli to stretch as air is drawn in .
When they return to their resting size, they squeeze the air out.

Question 15

How have alveoli adapted?

Answer 15

Large SA:V ratio 
Thin layers (less distance to travel)
Good blood supply 
Good ventilation 
The inner surface of alveoli is covered in a thin layer of water, salts and a lung surfacant. The surfacant allows the alveoli to remain inflated.

Question 16

What is ventilation

Answer 16

The movement of air

Question 17

What is the main rule about gases to remember

Answer 17

They move from an area of high pressure to low pressure.

Question 18

What is inside the pleural cavity

Answer 18

A thin layer of lubricating fluid so the different membranes can slide over each other as you breathe,

Question 19

Inspiration

Answer 19

The diaphragm and external intercoastal muscles contract.
Ribs move up and out
Increasing the interpulmonary volume
Decreasing the pressure
The interpulmonary pressure is now lower than atmospheric pressure, so air moves in.

Question 20

Expiration

Answer 20

The diaphragm and external intercoastal muscles relax.
Ribs move inside
Decreasing the interpulmonary volume
Increasing the pressure
The interpulmonary pressure is now higher than atmospheric pressure, so air moves out.

Question 21

What are the 3 ways to measure lungs etc.

Answer 21

1. Peak flow meter
2. Vitalographs
3. Spirometer

Question 22

Peak flow meter

Answer 22

measures the rate at which air can be expelled from the lungs

Question 23

Vitalographs

Answer 23

A more sophisticated version of a peak flow meter. The instrument produces a graph of how quickly and how much amount of air is breathed out. The volume of air is called the forced expiratory volume in 1 second.

Question 24

Spirometer

Answer 24

Investigates breathing patterns

Different aspects of the lung volume.

Question 25

Tidal volume

Answer 25

Volume of air that moves into and out of lungs

Question 26

Vital capacity

Answer 26

Volume of air that can be let out after the maximum inhalation.

Question 27

Inspiratory Reserve volume

Answer 27

The max volume of air you can breathe in over and above the inhalation.

Question 28

Expiratory Reserve Volume

Answer 28

The extra amount of air you can force out of your lungs over and above the normal tidal volume of air.

Question 29

Residual volume

Answer 29

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

Question 30

Total lung capacity

Answer 30

sum of the vital capacity and the residual capacity

Question 31

Breathing rate

Answer 31

number of breaths per minute

Question 32

Ventilation rate

Answer 32

Tidal volume x breathing rate

Question 33

Explain the basics of insects’ gaseous exchange system

Answer 33

They have a high oxygen demand
But, because they have their exoskeleton on the outside, they can’t allow gases and liquid to diffuse in or out of them.
They also don’t usually have a blood pigment that carried the oxygen for them.

Question 34

How can insects’ exchange gases?

Answer 34

They have small opening called spiracle along the thorax and their abdomen.
They also have spiracle sphincters to control the spiracles.
The spiracles lead to trachea, which lead to tracheoles.

Question 35

Trachae

Answer 35

They are tubes lined with spirals of chitin (to keep it open). Chitin is relatively impermeable to gases, so gaseous exchange doesn’t happen.

Question 36

Tracheole

Answer 36

They don’t have chitin, so permeable to any gaseous exchange.
They run next to the cells to allow gas exchange.
A large number of these, gives a large surface area.

Question 37

Trachea Fluid

Answer 37

This limits the penetration of air for diffusion.
The oxygen dissolves in moisture along the walls of tracheoles.
However, when the oxygen demands build up, lactic acid also builds up inside the tissues. This means that the water moves out of the trachea through osmosis, allows gases to move.

Question 38

What about bigger insects

Answer 38

Then need even more oxygen.
So:
when the muscles move, they pump the thorax and the abdomen, changing the volume and pressure in the trachea and tracheoles forcing the air in or out.
And:
There are air sacks which act as reservoirs. They increase the amount of air moved. They are inflated and deflated by the movement of tte thorax and the abdomen.

Question 39

Gaseous exchange in bony fishes

Answer 39

they have such a SA: V ratio that doesn’t allows diffusion to happen. So, instead they have gills.
In these gills they have gill filament, which have gill lamellae on them. The lamella consists of a network of blood vessels. It comes deoxygenated and then gains oxygen from the water and then returns oxygenated,

Question 40

What about bigger insects

Answer 40

They rely on pure movement to allow the water to move through them. This is called Ram Ventilation.

Question 41

What happens when the buccal cavity is open

Answer 41

It increases the volume at the mouth, decreasing the pressure. Hence the operculum closes.

Question 42

What happens when the buccal cavity is closed

Answer 42

The pressure builds up and then the operculum opens.

Question 43

How are fishes made for gas exchanges

Answer 43

1. Large surface
2. Rich blood supply
3. Thin layers for diffusion
4. Tips of adjacent filaments overlap, to increase resistance, giving more time for oxygen to move through the water.
5. Water and blood are countercurrent flows in opposite direction. This ensures a steep concentration gradient is maintains in comparison to if the system is parallel.
   It removes 80% of oxygen rather than 50%.

Question 44

Explain how the alveoli creates a surface for efficient gaseous exchange

Answer 44

Walls are 1 cell thick.
Constant blood supply - maintains the blood supply.
A large number of alveoli provides a large surface area: volume ratio.
Alveoli are quite small so it provides a large surface area: volume ratio.
Lung surfacant prevents it from collapsing.
Elastic recoil helps to expel the air (from elastic fibres)

Question 45

Explain how the different cells and tissues enable the effective exchange of gases.

Answer 45

Thin squamous epithelium cells, so that there is a shorter diffusion distance.
Lung surfacant prevents the alveoli from collapsing.
Ciliated epithelium and goblet cells trap dirt and bacteria.
Cartilage or smooth muscle keeps the airways open and changes the size of the airways.
Elastic fibres for elastic recoil and ventilation.

Question 46

Explain how a spirometer works

Answer 46

The person would have to breathe out through their mouth normally, at rest. Then, the lid of the spirometer would go down when the person breathes in, and then back up when they breathe out. This creates a wave on a trace. They should measure the height of the waves created, and measure at least 3 waves, then calculate the mean of those.

Question 47

How can you measure the volume of oxygen in a spirometer?

Answer 47

Measure the decrease in the trace, such as from the height of the first peak to the height of the last peak.

Question 48

How does having a good ventilation allow a fast gaseous exchange

Answer 48

It increases the pressure of in the air sack, so that it is greater than the oxygen concentration in the blood. So it constantly moves into the blood down the concentration gradient that has been set up, because there had been a high concentration of oxygen in the alveoli.