Gas Exchange in Humans

Question 1

what are the lungs?

Answer 1

they are specialised organs for gas exchange

Question 2

describe how air reaches the lungs

Answer 2

• air enters the trachea as you breath in
• the trachea splits into the bronchi, one bronchus per lung
• each bronchus splits into bronchioles
• the bronchioles lead to the alveoli
• the ribcage, intercostal muscles and diaphragm work to move air in and out

Question 3

define ventilation

Answer 3

the process of breathing in and out

Question 4

whats inspiration and expiration?

Answer 4

inspiration= breathing
expiration= breathing out

Question 5

how is ventilation controlled?

Answer 5

through the movement of the:
-External and internal intercostal muscles
-diaphragm
-ribcage

Question 6

describe the process of inspiration

Answer 6

1. the external intercorstal muscles and diaphragm muscle contract, moving the ribcage up and outwards, flattening the diaphragm and increasing the volume of the thoracic cavity
2. as the volume of the thoracic cavity increases, the pressure in the lung decreases,
   air moves down a pressure gradient from high to low meaning:
3. air flows down the trachea into the lungs

Question 7

what kind of process is inspiration?

Answer 7

Active process

Question 8

describe the process of expiration?

Answer 8

1. external intercostal and diaphragm muscles relax
2. the ribcage moves downwards and inwards, the diaphragm becomes curved again
3. thoracic cavity decreases in volume, causing the air pressure to increase
4. air is forced down the pressure gradient and out of the lungs

Question 9

what process is normal expiration?

Answer 9

its a passive process

Question 10

can expiration be forced? give an example

Answer 10

yes
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Question 11

where specifically does gas exchange happen in, in the human body?

Answer 11

the alveoli

Question 12

what are alveoli made from?

Answer 12

a single layer of thin, flat cells called alveolar epithelium

Question 13

what are alveoli surrounded by?

Answer 13

a network of capillileries

Question 14

what is a cappilery endothelium?

Answer 14

the epithelium formed at the capillary wall

Question 15

describe the gas exchange within alveoli

Answer 15

1. O2 diffuses out the alveoli across the alveolar epithelium and capillary endothelium, into haemoglobin and therefore blood
2. CO2 diffuses into the alveoli from the blood and is breathed out

Question 16

describe the adaptations alveoli have to increase the rate of diffusion

Answer 16

• thin exchange surface, short diffusion pathway
• large surface area,
• steep concentration gradient, from the blood and oxygen via the alveoli and capilleries.