7.2 Mammalian Gaseous Exchange System

Question 1

Define ventilation

Answer 1

The process in which air is constantly moved in and out of the lungs to maintain diffusion of gases across the alveolar epithelium

Question 2

Label this image of the human gaseous exchange system

Answer 2

Question 3

What is the pathway of air into the lungs?

Answer 3

1. Air enters theorugh the mouth and the nose then down the trachea
2. The trachea splits into two bronchi, one bronchus leading to each lung
3. Each bronchus then branches off into small tubes called bronchioles
4. The bronchioles end in small ‘air sacs’ called alveoli where gases are exchanged
5. The ribcage, intercostal muscles and diaphragm all work together to move air into and out of the

Question 4

What is each lung surrounded by?

Answer 4

Pleural fluid

Question 5

What is the role of pleural fluid?

Answer 5

Lubricates the lungs and helps the lungs to adhere to the walls of the thoracic cavity by water cohesion, this allows the lungs to expand with the chest during inhalation

Question 6

What are the important features of the nasal cavity?

Answer 6

-A large surface area with a good blood supply, which warms the air to body temperature
-A hairy lining, which secrets muscles to trap dust and bacteria, protecting the lung tissue from irritation and infection
-Moist surfaces, which increase the humidity of incoming air, reducing evaporation from the exchange surfaces

Question 7

What cells and tissues does the trachea contain?

Answer 7

C shaped cartilage, Smooth muscle, Elastic fibres, Goblet cells, Ciliated epithelium

Question 8

How does cartilage benefit the trachea?

Answer 8

Provide support which stops the trachea from collapsing. Rings are incomplete so that food can move down the oesophagus behind it easily

Question 9

What are the properties of cartilage?

Answer 9

Strong, flexible

Question 10

How do goblet cells benefit the trachea?

Answer 10

Secrete mucus onto the lining of the trachea, to trap dust and microorganisms that have escaped the nose lining stopping them from reaching the alveoli

Question 11

How do ciliated epithelial cells benefit the trachea?

Answer 11

Cilia beat and move the mucus along upwards away from the alveoli towards the throat

Question 12

What cells and tissues does the bronchus contain?

Answer 12

Smaller rings of cartilage, smooth muscle, elastic fibres, goblet cells, ciliated epithelium

Question 13

What cells and tissues does the bronchioles contain?

Answer 13

larger bronchioles - Smooth muscle, Elastic fibres, Goblet cells, Ciliated epithelium
smaller bronchioles - Smooth muscle, Elastic fibres, Ciliated epithelium
smallest bronchioles - Smooth muscle, Elastic fibres

Some larger bronchioles contain cartilage

Question 14

How does smooth muscle benefit the bronchioles?

Answer 14

Allows their diameter to be controlled to change the amount of air reaching the lungs

Question 15

What cells and tissues does the alveoli contain?

Answer 15

Elastic fibres, So collagen

Question 16

How do elastic fibres benefit the alveoli?

Answer 16

Allow the alveoli to stretch so more air can be drawn in, and recoil to help squeeze air out known as elastic recoil

Question 17

What is the definition of elastic recoil?

Answer 17

The ability of something to return to its original shape and size following stretch

Question 18

Where in the human body does elastic recoil particularly occur?

Answer 18

Alveoli, arteries

Question 19

What is the function of cartilage?

Answer 19

Provide structural support, holding structure open

Question 20

Where in the mammalian gaseous exchange system is cartilage found?

Answer 20

Trachea, Bronchi, Some larger bronchioles

Question 21

What is the function of smooth muscle?

Answer 21

Controls the diameter of tissues and cells, cosntrusts to restrict the flow of air, dilates to increase the flow of air

Question 22

Where in the mammalian gaseous exchange system is smooth muscle found?

Answer 22

Trachea, Bronchi, Bronchioles

Question 23

What is the function of elastic fibres?

Answer 23

Recoil and stretch to help take air in and breathe air out

Question 24

Where in the mammalian gaseous exchange system are elastic fibres found?

Answer 24

Trachea, Bronchi, Bronchioles, Alveoli

Question 25

What is the function of goblet cells?

Answer 25

Secrete mucus to trap microorganisms dust particles stopping them form reaching the alveoli towards

Question 26

Where in the mammalian gaseous exchange system are goblet cells found?

Answer 26

Trachea, Bronchi, Larger bronchioles

Question 27

What is the function of ciliated epithelium?

Answer 27

Beat in a synchronised pattern to waft muscular up the airway to the throat away from the alveoli towards prevent irrition and infection

Question 28

Where in the mammalian gaseous exchange system is ciliated epithelium found?

Answer 28

Trachea, Bronchi, Larger and Smaller bronchi but not the smallest (terminal) bronchi

Question 29

What type of epithelium does alveoli contain?

Answer 29

Squamous

Question 30

How are the alveoli adapted for efficient gas exchange?

Answer 30

-Large surface area, large number of alveoli increase the space available for gas exchange -Thin layers, only one epithelium cell thick so diffusion distance is short allowing for rapid diffusion -Good blood supply, surrounded by millions of capillaries bringing CO2 and carrying off oxygen, this maintains a steep concentration gradient between the alveoli and capillaries -Good ventilation, breathing moves air in and out of the alveoli helping maintain a steep diffusion gradient

Question 31

What is the purpose of lung surfactant in the alveoli?

Answer 31

Ensures alveoli remain inflated

Question 32

What is lung surfactant?

Answer 32

A chemical mixture containing phospholipids and both hydrophilic and hydrophobic proteins, which coat the surfaces of the alveoli and prevent them form collapsing

Question 33

Label this diagram of the lungs

Answer 33

Question 34

What are the mechanisms of breathing for inspiration?

Answer 34

-Active process, requires energy -External intercostals contract moving ribs upwards and outwards -Diaphragm contracts and flattens -Volume of thoracic cavity increases -Pressure of thoracic cavity decreases below pressure of atmospheric air so air is drawn inwards

Question 35

What are the mechanisms of breathing for expiration?

Answer 35

-Passive process -Diaphragm relaxes and returns to dome shape -External intercostals relax moving ribs downwards and inwards -Elastic fibres in alveoli return to normal stretch -Volume of thoracic cavity decreases -Pressure in thoracic cavity increases above atmospheric pressure so air moves out of the lungs

Question 36

What happens when expiration is forced?

Answer 36

-The internal intercostals contract moving, to pull the ribcage down and in harder and faster -Abdominal muscles contract forcing the diaphragm up to increase the pressure in the lungs rapidly

Question 37

Label this diagram of the bell jar model of ventilation

Answer 37

Question 38

What are the limitations of the bell jar model of ventilation?

Answer 38

-The bell jar is a rigid structure, which is unable to move in the same way as a ribcage -Model shows lungs as empty scars whereas in reality the lung is composed of many alveoli -The rubber sheet needs to be pulled down for the ballon’s to inflate whereas the diaphragms only flattens to cause air to enter the lungs -The bell jar is filled with air, whereas the chest cavity is filled with pleural fluid -Does not include structures such as the alveoli