B7 - Exchange Surfaces & Breathing

Question 1

What are the two main reasons that diffusion alone is not enough to supply large, active / multi-cellular organisms ?

Answer 1

1) The metabolic rate of the organism is usually quite high, so the oxygen demands & carbon dioxide demands are quite high.
2) The SA:V ration of the organism is small

Question 2

As the organism gets larger, why is there a need for a gaseous exchange system ?

Answer 2

The distance between the cells where the oxygen is needed and the supply of oxygen is too far for effective diffusion to take place, causing there to be a need for a gaseous exchange system.

Question 3

What happens to the SA:V ratio as the organism gets bigger, and what does that mean for the exchange of gases ?

Answer 3

• The SA:V ratio decreases
• This means that gases can’t be exchanged fast enough or in large enough amounts for the organism to survive.

Question 4

What are the 4 reasons for exchange systems ?

Answer 4

1) Large multicellualar organisms have a small surface aria to volume ratio.
2) Cells in the centre of the organism would not receive any materials if multicellular organisms survived on diffusion alone.
3) Metabolic rate - Multicellular organisms have high metabolic rates.
4) There is a need to exchange lots of materials fast.

Question 5

What are the 4 reasons for exchange systems ?

Answer 5

1) Large multicellular organisms have a small surface area to volume ratio.
2) The cells in the centre of the organism would not receive any materials if multicellular organs survived on diffusion alone.
3) Metabolic rate - multicellular organisms have high metabolic rates.
4) There is a need to exchange lots of materials fast.

Question 6

What are the 4 features of efficient gas exchange and how do they contribute to efficient gas exchange ?

Answer 6

1) Large surface area - provides a large area over which the exchange of matericls can occur.
2) Thin layers - this created a short diffusion path for gases, increasing the speed of exchange.
3) Blood supply - good, constant blood supply maintains a large diffusion gradient & ensures the exchanged substances are constantly maving to the area needed.
4) Ventilation - maintains the diffusion gradient, this makes the process faster and efficient.

Question 7

How you you work out the volume and surface area of cuboids ?

Answer 7

• Volume = length x width x height
• Surface area = (4 x length x height) + (2 x height x width)

Question 8

How you you work out the area of a circle, circumference of a circul, volume and surface area of cylinders ?

Answer 8

• Area of a circle = πr2,
• Circumference of a circle - 2πr
• Volume of a cylinder = πr2 x height
• Surface area = (2πr x height) + 2πr2

Question 9

How do you work out the volume and surface area of a sphere ?

Answer 9

• Volume = 4/3 πr2
• Surface area = 4πr2

Question 10

Why are gaseous exchange surfaces moist ?

Answer 10

So that oxygen dissolves in the water before diffusing into the body tissues.

Question 11

Why have mamals eveolved for efficient gas exchange, but minimise the volume of water lost from the body ?

Answer 11

The conditions needed to take in oxygen successfully are also ideal for the evaporation of water.

Question 12

Why do mammals need lots of oxygen for cellular respiration ?

Answer 12

• Small SA:V ratio- very large number of cells.
• High metabolic rate because mammals are active and to maintain their body temperature independant of the environment.

Question 13

What are the 5 key structures of the mammalian gaseous exchange system ?

Answer 13

1) Nasal cavity
2) Trachea
3) Bronchus
4) Bronchioles
5) Alveoli

Question 14

What are the features of the nasal cavity in the gaseous exchange system ?

Answer 14

1) Large surface area with a good blood supply - warms the air to body temperature.
2) A hairy lining - secretes mucus to trap dust and bacteria, protecting lung tussue from irritation and infection.
3) Moist surfaces - increases humidity of the incoming air, reducing eaporation from exchange surfaces.

Question 15

What are the 5 features of the trachea in the gaseous exchange system ?

Answer 15

1) Incomplete rings of cartalige - supports the trachea and stops it collapsing by provding it with strength & flexability. The rings are incomplete so food can move easily down the oesophagus.
2) Lined with ciliated epithelium - the cillia beat & waft the mucus, along with any trapped dirt and microorganisms away from the lungs.
3) Lined with goblet cells - secrete mucus to trap dust & microorganisms that have escaped the nose lining.
4) Lined with epithelial cells
5) Smooth muscle - controlls the airway circumferece and theirefore the airflow of the entire tracheobronchial tree.

Question 16

What are the 5 features of the bronchus in gaseous exchange system ?

Answer 16

1) Incomplete rings of cartilage - supporting the bronchus, providing it flexability and strength.
2) Lined with ciliated epithelium - the cillia beat & waft the mucus, along with any trapped dirt and microorganisms away from the lungs.
3) Lined with goblet cells - secrete mucus to trap dust & microorganisms that have escaped the nose lining.
4) Lined with epithelial cells
5) Smooth mucle - controles the diameter of the bronchus and the airflow through it

Question 17

What are the 2 features of the bronchioles in the gaseous exchange system ?

Answer 17

1) Smooth muscle - when the smooth muscle contracts, the bronchioles constricts and when the muscles relax, the bronchioles dilate.
2) Lined with flattened (squamous) epithelium - allows for rapid gas exchange.

Question 18

What are the features of the alveoli in the gaseous exchange system ?

Answer 18

1) Flattened (squamous) epithelium - allows for rapid exchange of gases.
2) Collagen & elastic fibres - allows the alveoli to strech as air is drawn in during insperation. During expiration they allow for the elastic recoil, expelling the carbon dioxide rich air out of the lungs.
3) Large SA:V ratio - allows for a fast diffusion rate, large area for diffusion to take place
4) Capillaries - maintains the diffusion gradient allowing for fast & efficient diffusion.
5) Inner surface covered in a thin layer of a solution of water, salta & lung surfactant - makes it possible for the alveoli to remain inflated, oxygen disolves in the water before diffusing into the blood.

Question 19

During ventilation, what is the result of pressure changes in the thorax (chest cavity) ?

Answer 19

Air moving in and out

Question 20

What does the rib cage provide ?

Answer 20

Semi-rigid case within which pressure can be lowered with respect to the air outside it

Question 21

What is the diaphragm ?

Answer 21

Broad, domed sheet of muscle, whcich forms the floor of the thorax

Question 22

Where are the external intercostal muscles and intercostal muscles found ?

Answer 22

Between the ribs

Question 23

What is the thorax lined with, and what does it surround ?

Answer 23

• Lined with the pleural membranes
• Surrounds the lungs

Question 24

Which one of inspiration & expiration is a passive process, and which one is an active process ?

Answer 24

• Inspiration is an active process (energy is being used)
• Expiraation is a passive process (unless forcibly exhailing - coughing)

Question 25

Describe the process of inspiration :

Answer 25

• The diaphragm contracts and moves down.
• The external intercostal muscles contract causing the ribs to rise up and out.
• The thoratic volume increases and the thoratic pressure decreases.
• Air than flows into the lungs (equalising the pressure).
• You breath in.

Question 26

Describe the process of expiration :

Answer 26

• The draphragm relaxes and moves up.
• The internal intercostal muscles contract, pulling the ribs down and fast (exhaling forcibly - coughing).
• The thoratic volume decreases and the thoratic pressure increases.
• Air flows out of the lungs.
• You breath out.

Question 27

What is a peak flow metre and what is it often used to monitor ?

Answer 27

A simple device that measures the rate at which air can be expelled from the lungs. People who have asthma often use these to monoitor how well their lungs are working.

Question 28

What is a vitalograph and what does the patient do and how does it record the results ?

Answer 28

• It is a more sophisticated version of the peak flow meter.
• The patient being tested breathes out as quickly as they can through a mouthpiece.
• The instrument produces a graph of the amount of air they can breath out and how quickly it is breathed out.

Question 29

What is a spirometer and what is it used to measure and what should you make sure before it is used ?

Answer 29

Commonly used to measure different aspects of the lung volume or to investigate breathing patterns.
- You shouldn’t use if you have anny pre-existing lung conditiions e.g asthma.
- The soda lime canister should be full in-order to absorb the carbon dioxide.
- Make sure the water in the tank isn’t at a too high, or a too low volume.
- Make sure the patient isn’t ill and is healthy.
- Make sure the medical grade oxygen is being used.

Question 30

What are the 6 components of the lung volume ?

Answer 30

1) Tidal volume
2) Vital capacity
3) Inspiratory reserve volume
4) Expiratory reserve volume
5) Residule volume
6) Total lung capacity

Question 31

What is tidal volume ?

Answer 31

Volume of air that moves into and out of the lungs with each resting breath.

Question 32

What is vital capacity ?

Answer 32

The volume of air that can be breathed in when the strongest possibl exhalation is followed by the strongest possible intake of breath.

Question 33

What is inspiratory reserve volume ?

Answer 33

The maximum volume of air you can breathe in over and above a normal inhalation.

Question 34

What is expiratory reserve volume ?

Answer 34

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

Question 35

What is the residual volume ?

Answer 35

The volume of air that is left in your lungs when you have exhales as hard as possible (dead air - stops your lungs collapsing). This can’t be measured directly.

Question 36

What is the total lung capacity ?

Answer 36

The sum of the vital capacity and the residual volume.

Question 37

What is the breathing rate ?

Answer 37

The number of breaths taken per minute.

Question 38

What is the ventilation rate ?

Answer 38

The volume of air inhaled in one minute.

Question 39

What is the equation for the ventilation rate ?

Answer 39

Ventilation rate = Tidal volume x breathing rate (per minute)

Question 40

What does having a tough exoskeleton mean for the gaseous exchange in insects ?

Answer 40

Little to no gaseous exchange can take place through it.

Question 41

Why do insects need a different way of exchanging gases ?

Answer 41

They don’t usually have blood pigments that can carry oxygen and have instead evolved to deliver the oxygen directly to the cells and to remove the carbon dioxide in the same way.

Question 42

What is along the thorax & abdomen of most insects, and what do they do ?

Answer 42

• Small openings known as spiracles.
• Air enters and leaves the system through the spiracles, but water is also lost through them.

Question 43

Why in many insects can the spiracles be opened or closed by sphincters ?

Answer 43

To reduce the volume of water lost and to maximise the efficiency of gaseous exchange.

Question 44

What happens when an insect is inactive ?

Answer 44

• The oxygen demands are very low.
• The spiricles will be closed most of the time.

Question 45

In insects, what leads away from the spiracles and what does it do ? (4 points)

Answer 45

• The trachea leads away from the spiracles.
• They are the largest tubes of the insect respiratory system.
• They cary air into the body.
• Lined by spirals of chitin.

Question 46

In insects, why are the tubes lined by spirals of chitin ?

Answer 46

• Keeps the tubes open if they are bent or pressed.
• Chitin is relativly impermeable to gases and so little gaseouse exhange takes place in the trachea.

Question 47

What is a tracheole ?

Answer 47

• A single, greatly elongated cell with no chitin lining so they are freely permeable to gases.
• Because of their small size, they spread throughout the tissues of the insects, running between the air and respiring cells.

Question 48

What is towards the end of the tracheoles, and what does it do ?

Answer 48

• Tracheal fluid.
• Limits the penetration of air for diffusion.

Question 49

What happens when oxygen demand builds up ?

Answer 49

• A lactic acid builds up in the tissues results in water moving out of the tracheoles by osmosis.
• This exposes more surface area for gaseous exchange.

Question 50

Where is all of the oxygen needed by the cells of an insect supplied from ?

Answer 50

It is supplied by the tracheal system.

Question 51

Some insects have a very high energy demands. To supply the extra energy demands they have alternative methods of increasing the level of gaseous exchange. What are these 2 alternative methods ?

Answer 51

1) Mechanical ventilation of the teacheal system.
2) Collapsible enlarged tracheae or air sacs which acts as air reservoirs.

Question 52

What is mechanical ventilation of the tracheal system ?

Answer 52

• Air is activly pumped into the system by muscular pumping movements of the thorax and/or the abdomen. These movements change the volume of the body and this changes the pressure in the tracheae and tracheoles.
• Air is drawn into the tracheae and tracheoles, or forced out, as the pressure changes.

Question 53

What is the collapsible enlarged tracheae or air sacs, which acts as air reservoirs ?

Answer 53

• They are used to increase the amount of air moved through the gas exchange system.
• They are usually inflated and deflated by ventilating movements of the thorax and abdomen.

Question 54

Where and how does gaseous exchange occour in fish ?

Answer 54

• In the gills
• The oxygen from water flowing over the gills diffuses into the blood stream and vis versa.

Question 55

What 3 features does fishes gills have for successful gaseous exchange ?

Answer 55

1) Large SA:V ratio.
2) Good blood supply.
3) Thin layers.

Question 56

What is the operculum and what is its function ?

Answer 56

• Operculum (a bony flap) covering the gill cavity.
• Active in maintaining a flow of water over the fills.

Question 57

What do fish need to maintain to allow for efficient gas exchange ?

Answer 57

They need to maintain a continuous flow of water over the gills, even when they are not moving.

Question 58

How do fish keep a current of water flowing over their gills while swimming ?

Answer 58

Oppening their moth and operculum.

Question 59

How do fish keep water continuously flowing over their gills when they are not swimming ?

Answer 59

• The mouth is opened and the floor of the buccal cavity is lowered.
• This increases the volume and decreases the pressure of the buccal cavity, causing water to move into it.
• At the same time the opurcular valve shuts and the opercular cavity containing the gills expands.
• This lowers the pressure in the opercular cavity containing the gills.
• The floor of the bucal cavity starts to move up, increasing the pressure there so the water moves from the bucal cavity over the gills.
• The mouth closes, the operculum opend and the sides of the opercular cavity moves inwards.
• All of these actions increases the pressure in the opercular cavity and forces water over the gilld and out of the operculum.
• The floor of the bucal cavity is steadily moved up, maintaining a flow of water over the gills.

Question 60

What 2 extra adaptations do the gills have to ensure the most effective possible gaseous exchange ?

Answer 60

1) The tips of asjacent gill filaments overlap - increases the resistance to the flow of water over the gill surfaces and slows down the movement of the water. As a resuly there is more time for gaseous exchange to take place.
2) The water moving over the gills and the blood in the gill filaments flow in different directions - a steep concentration gradient is needed for fast, efficient diffusion to take place. This ensures that steeper concentration gradients are maintained than if blood and water flowed in the same direction.