Human gaseous exchange system - Key features

Question 1

Name all the parts of the human gaseous exchange system:

Answer 1

• Trachea
• Rings of cartilage
• Right lung
• Bronchus
• Bronchioles
• Ribs
• Intercostal muscle
• Diaphragm
• Pleural cavity fluid
• Larynx
• Clavicle (collar bone)
• External intercostal muscle
• Internal intercostal muscle
• Sternum

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Question 2

What does the nasal cavity (key structure) have? And why are they there?

Answer 2

• Large SA with good blood supply, warms air as enters body
• Hairy surface which secretes mucus, to trap dust + microbes, protecting lung tissue from irritation + infection
• Moist surface, which increases humidity of inhaled air

Question 3

What structures does the trachea have?

Answer 3

Main aurway from nose to chest

Supported by C-shaped rings of strong, flexible cartilage which keep it open + allow food to pass along oesophagus

Question 4

What is the trachea lined with and what do they do?

Answer 4

Lined with ciliated epithelial cells + goblet cells

Goblet cells produce mucus, which traps dust + microbes, whilst cilia beats rhythmically to move mucus from lungs

Question 5

What are the structural features of the bronchi?

Answer 5

• First division of trachea
• Flexible cartilage
• Smaller in diameter
• Epithelium
• Larger lumen width than bronchioles

Question 6

What are the structural features of the bronchioles?

Answer 6

• Further divisions of bronchus
• No cartilage compared to bronchi
• Narrower lumen
• Thin layer of flattened epithelium
• Smooth muscle layer (bronchi dont)

Can constrict + relax bronchioles + change lumen width due to muscle

Question 7

What is the main site of gas exchange within the lungs + whats its diameter?

Answer 7

Alveoli, 200-300um

Are microscopic air sacs

Question 8

What are the structural features of alveoli?

Answer 8

• Very thin walls
• Composed of single layer of thin, flattened squamous epithelium cells
• Walls contain collagen + some elastic fibres (composed of elastin), allows for elastic recoil so air can be forced out during exhaustion

Question 9

What are the main adaptations of the alveoli?

Answer 9

• Large surface area
• Thin layers/walls, 1 cell thick
• Good blood supply = network of capillaries wrap around alveoli, maintains conc gradient
• Good ventilation = inhalation + exhalation, constant flow of air, maintain conc gradient

Question 10

What does the alveolus produce?

Answer 10

A lung surfactant, which covers its surface

Keeps alveoli from collapsing when filled with air

Question 11

What is the function of the lung surfactant?

Answer 11

Keeps alveoli inflated + allows O2 to dissolve into it before diffusing into blood

However does allow for water loss, but theres adaptations in gas exchange system to reduce this