3.1.1c) The structures and functions of the components of the mammalian gaseous exchange system

Question 1

Nasal cavity

Answer 1

Large SA with a good blood supply - warms the air to body temperature
Hairy lining - secretes mucus to trap dust and bacteria protecting delicate lung tissue from irritation and infection
Moist surfaces - increases the humidity of the incoming air, reducing evaporation from the exchange surfaces

Question 2

Trachea

Answer 2

Main airway carrying clean, warm, moist air from the nose down the chest
Supported by incomplete rings of cartilage- stop trachea from collapsing
Lined with ciliated epithelium with goblet cells between and below

Question 3

Goblet cells

Answer 3

Secrete mucus onto the lining of the trachea - trapping dust and microorganisms

Question 4

Cilla

Answer 4

Beat and move the mucus along with trapped dirt and microorganisms away from the lungs
Goes into the throat, is swallowed and digested
Cigarette smoke can stop the cilia from beating

Question 5

Bronchus

Answer 5

2 bronchi divide off from the trachea
Similar in structure to the trachea with supportive rings of cartilage, but they are smaller

Question 6

Bronchioles

Answer 6

Bronchi divide off into the bronchioles
1mm or less
Have no cartilage
Walls of the bronchioles contain smooth muscle which allow them to constrict and dilate
Lined with a thin layer of flattened epithelium - making some gas exchange possible

Question 7

Alveoli

Answer 7

Tiny air sacs where main gas exchange occurs
Diameter of 200-300um
Layer of thin epithelium cells
Contain elastic fibres- allow the alveoli to stretch and recoil when air is drawn in and out (elastic recoil)

Question 8

Alveoli adaptations - large surface area

Answer 8

300-500 million alveoli per adult lung
Combined alveolar surface area for gaseous exchange 50-75m²

Question 9

Alveoli adaptations - thin layers

Answer 9

Alveoli and capillary walls are only 1 cell thick
Short diffusion distance - more efficient diffusion

Question 10

Alveoli adaptations - good blood supply

Answer 10

The alveoli are surrounded by a network of around 280 capillaries
Constant flow of blood helps to maintain a steep concentration gradient for both carbon dioxide and oxygen between the air in the alveoli and the blood in the capillaries

Question 11

Alveoli adaptations - good ventilation

Answer 11

Breathing moves air in and out of the alveoli - maintains steep diffusion gradients for oxygen and carbon dioxide between the blood and the air in the lungs