Chapter 7

Question 1

What is the need for a specialised exchange surface?

Answer 1

For larger multi-celled organisms diffusion of gases would take too long otherwise .
Larger organisms have a higher metabolic demand which normal diffusion cannot meet .

Question 2

What are the characteristics of a specialised exchange surface?

Answer 2

Large surface area for a higher rate of diffusion .
Thin to reduce distance of the diffusion pathway .
Good blood supply for larger concentration gradient.
Good ventilation for a larger concentration gradient.

Question 3

What are the features of the naval cavity?

Answer 3

Large surface area with a good blood supply.
Hairy lining which secretes mucus , preventing dust or pathogens damaging tissue.
Moist surfaces - less evaporation from the exchange surfaces .

Question 4

What is the trachea ?

Answer 4

Wide tube supported by incomplete rings of cartilage . Rings are incomplete to allow food down the oesophagus.
Lined with ciliated epithelium and goblet cells. Mucus is secreted by goblet cells trapping dust and pathogens which the cilia then waft away from the lungs. Smoking stops this wafting .

Question 5

What is the bronchus ?

Answer 5

Branch of from trachea to the lungs. Smaller but same structure .

Question 6

What are the bronchioles ?

Answer 6

The bronchi divide into smaller bronchioles in the lungs with a diameter of 1mm or less. No cartilage rings but contain smooth muscle which contracts to constrict the bronchioles and relaxes to open them up. Have a thin layer of flattened epithelium .

Question 7

What are the alveoli ?

Answer 7

Tiny air sacs. Only on mammalian lungs. Diameter or around 200 to 300 micro meters. Contain layers of thin flattened epithelial cells as well as collagen and elastic fibres . Which recoil when exhaling

Question 8

What are the adaptions of the alveoli ?

Answer 8

Large surface area .
Thin layers
Good blood supply
Good ventilation 
Inside surface covered in solution of water salt and surfactants which allow the alveoli to remain inflated

Question 9

How does inspiration/ inhalation work?

Answer 9

Diaphragm contracts flattening.
External intercostal muscles contract moving the rib cage upwards and outwards. Thorax volume increases so pressure is reduced to below atmospheric pressure so air is drawn in until pressure is equalised .

Question 10

Expiration normally

Answer 10

Diaphragm relaxes so it moves up to a dome shape.
External intercostal muscles relax . Ribs move down and in . Pressure increases as thorax volume decreases. Air is forced out until pressure inside is equal to pressure outside.

Question 11

Forcible exhalation

Answer 11

Internal intercostal muscles contract pulling the rib cage down quickly and the abdominal muscles contracts forcing the diaphragm up . Rapidly increase the pressure.

Question 12

Different ways to measure air drawn into and out of the lungs

Answer 12

Peak flow meter, measures rate at which air can be expelled.
Vitalographs. Breathe out quick through a mouthpiece . Produce a graph of how much they breathed out and how fast.
Spirometer.

Question 13

Components of lung volume

Answer 13

Tidal volume. Amount of air into and out of the lungs
Vital capacity. Maximum amount of air that can be breathed in after the strongest possible exhalation.
Inspiratory reserve volume . Max volume of air over the normal inhalation.
Expiratory reserve. Volume of air you can forcibly breath out above the normal amount you breath out .
Residual volume . How much air is left in your lungs after maximum exhalation .
Total lung capacity. Vital capacity plus residual volume .

Question 14

Breathing rate.

Answer 14

Number of breathes per minute

Question 15

Ventilation rate

Answer 15

Volume of air drawn in per minute .

Tidal volume X breathing rate = Ventilation rate

Question 16

What are the spiracles ?

Answer 16

Small openings along the side of the thorax and abdomen of an insect which can be opened and closed by sphincters .
When an insect is resting the spiracles are closed but when they are active and they need more oxygen then they are opened.

Question 17

Tracheae in insects.

Answer 17

Lead away from spiracles . 1mm in diameter
Run into and along insects bodies. Lined with chitin which is mostly impermeable to gases. Which means very little gas exchange occurs there. Air travels down by diffusion alone.

Question 18

Tracheoles in insects

Answer 18

Branch of from tracheae. 0.6 - 0.8 micro meters in diameter. Single elongated cells which run between tissues and even between cells. No chitin.

Question 19

Tracheal fluid.

Answer 19

At the end of tracheoles . Reduces permeability for oxygen .
During exercise when lactic acid builds up in tissues water leaves the tracheoles via osmosis which increases the surface area for diffusion .

Question 20

Mechanical ventilation

Answer 20

Larger insects may need even more oxygen so they change the volume of their thorax and abdomen using muscular pumping movements . This changes the volume and therefore the pressure which draws more air in or pushes more out .

Question 21

Collapsible air sacs.

Answer 21

collapsible enlarged tracheae or air sacs, which act as air reservoirs these are used to increase the amount of air moved through the gas exchange system. They are usually inflated and deflated by the ventilating movements of the thorax and abdomen.

Question 22

Respiration in fish

Answer 22

The mouth is opened and the floor of the buccal cavity (mouth) is lowered. This increases the volume of the buccal cavity. As a result the pressure in the cavity drops and water moves into the buccal cavity. At the same time the opercular valve is shut and the opercular cavity containing the gills expands. This lowers the pressure in the opercular cavity containing the gills. The floor of the buccal cavity starts to move up, increasing the pressure there so water moves from the buccal cavity over the gills. The mouth closes, the operculum opens and the sides of the opercular cavity move inwards. All of these actions increase the pressure in the opercular cavity and force water over the gills and out of the operculum. The floor of the buccal cavity is steadily moved up, maintaining a flow of water over the gills.