Module 3 - Exchange Surfaces and Breathing

Question 1

How to use a Spirometer?

Answer 1

• its a chamber full of air floating in a tank of water
• the person has to breathe in causing the lie of the chamber to go down which is noted by the pen attached to the lid marking the rotating drum
• person exhales and co2 is absorbed by the soda lime at the bottom of the chamber to prevent build up of co2

Question 2

/\/\/

Answer 2

Tidal volume

Question 3

/\/\/\ x2 (bigger)

Answer 3

Vital capacity

Question 4

What 3 factors affect the need for an exchange system?

Answer 4

• Size (single-celled cytoplasm close to environment lived in) (multicellular orgs may have several layers of cells - longer diffusion pathway)
• SA:V (small animals, even sa:v and large animals have small sa:v)
• Level of Activity (metabolic activity means animal needs nutrients and good oxy supply)

Question 5

Features Of A Good Exchange Surface

Answer 5

• Large SA: provides more space for mols to pass through
  Folding walls/membranes
• Thin barrier to reduce the diffusion distance (permeability)
• Good blood supply.
  Brings fresh mol supply, keeps concentration high and removes mols
  Maintains steep conc gradient so diffusion occurs rapidly

Question 6

What is the Gaseous Exchange System?

Answer 6

• lungs (inflatable sacs)
• air passes into lungs through the nose and along the trachea, bronchi and bronchioles. Finally reaching tiny air-filled sacs called alveoli
• lungs protected by rib cage, held together by INTERCOSTAL muscles. Actions of these muscles and the DIAPHRAGM helps to produce breathing movements (VENTILATION)

Question 7

Gas exchange in the lungs

Answer 7

• gases pass by diffusion through thin walls of the alveoli
• oxygen passes from the air in alveoli to blood in capillaries
• Carbon D passes from blood to air in alveoli
• lungs must maintain a steep conc gradient in both directions in order to ensure diffusion can continue

Question 8

adaptation to reduce gas diffusion distance

Answer 8

• alveolus wall is one cell thick
• Capillary wall is one cell thick
• Both walls consist of squamous cells (flattened)
• capillaries are in close contact with the alveolus walls
• barrow capillaries are so narrow that the RBC are squeezed against the capillary walls, making them closer to air in alveoli

Question 9

What does a good blood supply do?

Answer 9

• carries CO2 to lungs so conc of CO2 is higher in the blood so it moves into the air in the alveoli
• carries Oxy away from the lungs so conc of Oxy is lower in the blood so it moves into the blood from the air in the alveoli

Question 10

Ventilation

Answer 10

• replaces used air with new air
• conc of Oxy in the air of the alveolus remain higher than blood
• conc of Carbon D in alveoli remains lower than that in the blood

Question 11

Ventilation (Inspiration)

Answer 11

• diaphragm contracts to MOVE DOWN and become FLATTER
• EXTERNAL INTERCOSTAL muscles contract to RAISE RIBS
• VOLUME of chest cavity INCREASES
• PRESSURE in chest cavity DROPS BELOW ATMOSPHERIC PRESSURE
• air is moved into the lungs

Question 12

Ventilation (expiration)

Answer 12

• DIAPHRAGM RELAXES and is pushed UP by the displaced organs underneath
• EXTERNAL INTERCOSTAL MUSCLES relax and the ribs FALL; the INTERNAL INTERCOSTAL MUSCLES contact to push air out more forcefully
• VOLUME of chest cavity is DECREASED
• the PRESSURE in the lungs INCREASES AND RISES ABOVE ATMOSPHERIC PRESSURE
• air is moved out of the lungs