Specialised Exchange Surfaces

Question 1

why do single celled organisms not require specialised exchange systems?

Answer 1

• usually low metabolic activity so low oxyge demand and low carbon dioxide production.
• smaller organisms have a larger surface area to volume ratio.

Question 2

what are the features of effective exchange surfaces?

Answer 2

• increased surface are.
• thin layers.
• good blood supply.
• good ventilation.

Question 3

how does a larger surface area aid gas exchange?

Answer 3

it provides the area needed for exchange. For example, villi in small intestines of mammals allows molecules to diffuse over a larger surface.

Question 4

how do thin layers aid gas exchange?

Answer 4

short diffusion distances mean that substances don’t have to move as far. this makes the process fast and efficient.

Question 5

how does a good blood supply aid gas exchange?

Answer 5

having a good blood supply ensures that substrates are constantly delivered to and removed from the exchange surface. this maintains a steep concentration gradient for diffusion.

Question 6

what are the key structures present in the human gaseous exchange system

Answer 6

• nasal cavity
• trachea
• bronchus
• bronchioles
• alveoli

Question 7

what are the important structures in the nasal cavity?

Answer 7

• large surface area with a good blood supply which warms the air to body temperature.
• a hairy lining which secretes mucus to trap dust and bacteria, protecting lung tissue from bacteria.
• moist surfaces. increases humidy of incoming air, reducing evaporation from exchange surfaces.

Question 8

why does the trachea contain incomplete rings of strong, flexibile cartilage.

Answer 8

stops the trachea from collapsing. they are incomplete so food can eaily move down the oesophagus behind the trachea.

Question 9

what is the trachea lined with?

Answer 9

ciliated epithelium, with goblet cells between them.

Question 10

what do goblet cells do?

Answer 10

secrete mucus onto the lining of the trachea to trap dust and bacteria.

Question 11

what does the cilia do?

Answer 11

beats and moves the mucus with dirt and bacteria away from the lungs.

Question 12

where do the bronchus lead to?

Answer 12

the left bronchus leads to the left lung, the right bronchus leads to the right llung.

Question 13

does the bronchus contain cartilage rings?

Answer 13

yes, but they are smaller.

Question 14

do bronchioles contain rings of cartilage?

Answer 14

small bronchioles do not but some do.

Question 15

what happens when the smooth muscle in bronchiole walls contracts?

Answer 15

brochioles constrict. to reduce amount of air entering lungs.

Question 16

what happens when smooth muscle in bronchiole walls relax?

Answer 16

bronchioles dilate to increase the amount of air entering lungs.

Question 17

are bronchioles lined with flattened epithelium?

Answer 17

yes - a small layer.

Question 18

what are the main gas exchange surfaces in the body?

Answer 18

alveoli

Question 19

what is the diameter of an alveolous?

Answer 19

200-300 micrometres.

Question 20

what are alveoli composed of?

Answer 20

• thin flattened epithelial cells.
• collagen

-elastin fibres

Question 21

what do elastic tissues allow alveoli to do?

Answer 21

stretch as air is drawn in.

Question 22

what is the elastic recoil of the lungs?

Answer 22

elastic tissues allow alveoli to stretch as air is drawn in. and squeeze air out as it returns to normal size.

Question 23

what are the adaptations of alveoli?

Answer 23

• large surface area
• thin layers (one single epithelial cell thick.)
• good blood supply ( 280 million capillaries surround them.)
• good ventilation (breathing maintains concentration gradient.)

Question 24

how many alveoli per adult lung?

Answer 24

300-500 million.

Question 25

what is the inner surface of the alveoli covered in?

Answer 25

a thin layer of a solution of water, salts and lung surfactant.

Question 26

what is the purpose of lung surfactant?

Answer 26

allows alveoli to remain inflated

Question 27

what happens during inspiration?

Answer 27

• diaphragm contracts (moves downwards, flattened shape.)
• external intercostal mucles contract.
• ribs move upwards and outwards
• volume of thorax increases.
• pressure of thorax decreases.
• air moves in as there is relatively lower pressure inside lungs than in the atmosphere.

Question 28

why is inspiration an active process?

Answer 28

inspiration is the result of mucle contraction.

Question 29

what happens during expiration?

Answer 29

• diaphragm relaxes (moves upwards dome shape)
• external intercoast mucles relax.
• ribs move down and inwars under gravity
• volume decreases.
• pressure increases so air moves out of thorax to surroundings.

Question 30

what are people with asthma triggered by?

Answer 30

• house dust mites
• cigarette smoke
• pollen
• stress

Question 31

what happens during an asthma attack?

Answer 31

cells lining bronchioles release histamines. these stimulate the goblet cells to make excess mucus and the smooth muscle in the walls to contract. Airways narrow and fill with mucus so it is harder to breathe.

Question 32

what are histamines?

Answer 32

chemicals that make the epithelial cells become inflammed and swollen.

Question 33

what are the two main ways of treating asthma?

Answer 33

• relievers
• preventers

Question 34

what do relievers do (asthma)?

Answer 34

• give immediate relief from symptoms.
• attach to active sites on the surface membranes of smooth muscle cells in the bronchioles, making them relax and dilating the airways.