Exchange and transport systems: Gas exchange in humans

Question 1

What are the lungs

Answer 1

A major organ of the respiratory system, performing the exchange of oxygen and carbon dioxide with air from the atmosphere

Question 2

What is the trachea (in humans)

Answer 2

Where air enters the lungs through the larynx

Question 3

What prevents the trachea from collapsing, and allows the airway to stay open

Answer 3

A series of ‘c’ shaped cartilage rings on the trachea

Question 4

What are the bronchi

Answer 4

Two tubes that extend downward from the trachea going into each lung

Question 5

What are the bronchioles

Answer 5

Small tubes in the lungs which branch from the larger bronchi

Question 6

What are alveoli

Answer 6

Tiny air sacs at the end of the broncholes, and where blood exchange oxygen and carbon dioxide during ventilation

Question 7

What is ventilation

Answer 7

The movement of air through inspiration (breathing in) and expiration (breathing out) - The scientific word for breathing

Question 8

Why must mammals have a specialised gas exchange system

Answer 8

• Bc they have a low SA:V ratio therefore the diffusion pathway is too long
• AND having a specialised gas exchange system provides a large surface area via the lungs AND short diffusion pathway via the alveoli

Question 9

Name the main features of the human gas exchange system (where the air travels)

Answer 9

• Lungs
• Trachea
• Bronchi
• Bronchioles
• Alveoli

Question 10

What are the main muscles that control ventilation

Answer 10

• The diaphragm
• Intercostal muscles

Question 11

Describe the process of inspiration

Answer 11

• The external intercostal muscles contract, and the diaphragm contracts and flattens
  This causes the volume within the lungs/thoracic cavity to increase, and the pressure within the lungs to decrease
• Therefore movement of air travels in a downward pressure gradient from the surroundings into the lungs (as air pressure is higher in the atmosphere)

Question 12

Describe the process of expiration

Answer 12

• The internal intercostal muscles contract, and the diaphragm relaxes and curves into a dome shape
  This causes the volume within the lungs/thoracic cavity to decrease, and the pressure within the lungs to increase
• Therefore movement of air travels in a downward pressure gradient from the lungs into the surroundings (as air pressure is lower in the atmosphere)

Question 13

Describe how oxygen into the air is transported throughout the different features of the gas exchange system and enters the blood in the capillaries

Answer 13

• Oxygen from air moves down into trachea, bronchi and bronchioles into the alveoli
• This movement happens down a pressure gradient
• Once in the alveoli, oxygen diffuses across alveolar epithelium (down the diffusion gradient) into the capillaries through the capillary endothelium

Question 14

Define inspiration

Answer 14

An active process by which the lungs takes in air from the environment

Question 15

Define expiration

Answer 15

A passive process (if not forced) by where waste gases from the body is exhaled back into the environment

Question 16

How does the alveoli increase the rate of diffusion

Answer 16

• Increased surface area: rapid diffusion of gases
• Short diffusion pathway: the alveolar epithelium is only one cell thick

Question 17

Outline the ways in which the lungs are adapted for efficient gas exchange

Answer 17

• The lungs contain millions of alveoli - creating a large surface area for gas exchange allowing for rapid diffusion rate
• The alveolar epithelium (lining of the alveoli) is only one cell thick - creating a short diffusion pathway
• Dense network of pulmonary capillaries - maintaining a steep concentration gradient also allowing for rapid diffusion rate