IB biology: topic 6: Gas Exchange

what is the direction of oxygen from the air to the blood?

trachea,

bronchus (left/right),

alveoli

bronchioles (branches),

arterioles

what make up the ribs?

internal/external intercostal muscle, ribs

what maintains the concentration gradient in gas exchange?

ventilation

how does oxygen enter the blood?

1. air moves in/out of alveolus, gases dissolve in mucus lining
2. blood (low O2, high CO2) passes the alveolus,
3. carbon dioxide diffuse from red blood cells to be exhaled,
4. oxygen diffuses into red blood cells (diffuses through alveolus wall and capillary wall.

what happens to the diaphragm/ribcage in inspiration?

diaphragm contracts, moves downwards, flattens.

ribcage moves upwards and outwards

what happens to the diaphragm/ribcage in expiration?

diaphragm relaxes, moves upwards, becomes more domed.

\
ribcage moves downwards and inwards

what happens to volume in thorax/pressure in inspiration?

volume inside thorax increases and consequently the pressure decreases

what happens to volume in thorax/pressure in expiration?

volume inside thorax decreases and consequently the pressure increases

what causes the ribcage to move?

intercostal muscles (internal and external)

how do the intercostal muscles change during inspiration?

the external intercostal muscles contract, pulling the ribcage upwards and outwards,

internal intercostal muscles relax and are pulled back into elongated state

how do the intercostal muscles change during expiration?

the external intercostal muscles relax and are pulled back into elongated state,

internal intercostal muscles contract, pulling the ribcage inwards and downwards

how do the abdomen wall muscles change during inspiration?

the muscles in the abdomen wall relax, allowing pressure from the diaphragm to push it out

how do the abdomen wall muscles change during expiration?

muscles in the abdomen wall contract, pushing abdominal organs and diaphragm upwards

what is total lung capacity?

the total volume that can occupy the lungs - around 5 litres (including residual volume)

what is the residual volume?

the volume which we cannot remove from our lungs - 1.25 litres

what is the difference between inspiratory reserve volume and inspiratory capacity?

inspiratory reserve volume is the excess volume we can inhale when not at rest (e.g taking a deep breath),

inspiratory capacity is the total volume we can breath in to our lungs (around 2.5 litres)

why can we not remove the residual volume in the lungs?

as otherwise the lungs will collapse

what is vital capacity?

the volume of air that we can remove from the lungs (vital capacity + residual volume = total lung capacity)

what is the difference between expiatory reserve volume and functional residual capacity?

expiatory reserve volume is the maximum volume of air we can exhale from our lungs,

functional residual capacity is the air that remains in our lungs at rest (around 2.5 litres)

what is tidal volume?

the difference in volume of the lungs when at rest, inspiring and expiring (around 0.5 litres)

how many types of pneumocytes are there?

two (type I and type II)

what % of pneumocytes are type I?

95%

what % of pneumocytes are type II?

5%

what is the role of type I pneumocytes?

gas exchange

what is the shape of type I pneumocytes?

flattened

what is the shape of type II pneumocytes?

rounded

what is the role of type II pneumocytes?

secrete fluid which creates a film of moisture for O2 to dissolve and CO2 to evaporate from

how do type II pneumocytes stop the lungs from collapsing?

fluid has surfactant which reduces surface tension and so prevents alveoli walls adhering (sticking together) on exhalation and lung collapsing.

what are the causes of emphysema?

smokers’ phagocytes in the lungs start to produce more elastase (a digestive enzyme).

genetics can means that the quantity and effectiveness of the enzyme inhibitor and so more elastase are produced.

together this results in the alveolus walls being weakened/destroyed by the increased production of elastase

what are the consequences of emphysema?

low oxygen saturation in the blood,

higher carbon dioxide levels in the blood,

lack of energy,

shortness of breath,

laboured/rapid ventilation

what are the causes of lung cancer?

smoking (87% of cases),

passive smoking,

air pollution (diesel exhaust fumes, smoke from burning matter),

radon gas,

asbestos/silica

what are the consequences of lung cancer?

difficulties in breathing,

persistent coughing/coughing up blood,

chest pain,

fatigue/loss of appetite/weight loss,

high mortality rate