Organisms Exchange Substances with their Environment: Gas Exchange - Humans (Structure)

Question 1

List the features of the human gas exchange system

Answer 1

• Trachea
• Bronchi
• Bronchioles
• Alveoli
• Lungs
• Internal intercostal muscles
• External intercostal muscles
• Diaphragm

Question 2

Describe how the different structures of the gas exchange system are connected

Answer 2

• During inhalation, the air enters the trachea
• The trachea splits into two bronchi - one bronchus leading into each lung
• Each bronchus branches off into smaller tubes called bronchioles
• Bronchioles end in small ‘air sacs’ called alveoli
• Ribcage, intercostal muscles and diaphragm work together to move air in and out

Question 3

Describe the structure and function of the trachea

Answer 3

• Function
- Trachea enables flow of air into and out of lungs

• Structure
- Wide airway with many C-shaped rings of cartilage to provide support and flexibility

• Tracheal walls are lined with ciliated epithelium and goblet cells - produce mucus to trap dirt and pathogens
• Cilia cells move mucus to throat, down oesophagus and into stomach so pathogens can be destroyed

Question 4

Describe the structure and function of the bronchus

Answer 4

• Function
- Bronchus allow flow of air into the bronchioles

• Structure

• Narrower than trachea
• Two bronchi, one for each lung
• Supported by rings of cartilage for strength - has less cartilage, more smooth muscle than trachea
• Smooth muscle allows them to constrict to reduce air flow
• Lined by ciliated epithelium and goblet cells to trap dirt/pathogens

Question 5

Describe the structure and function of the bronchioles

Answer 5

• Function
- Allow passage of air into the alveoli

• Structure

• Walls lined with epitheilial cells
• No cartiliage, more muscle
• Walls made of muscle and elastic fibres
• Elastic fibres stretch during expiration; recoil during inhalation
• Muscle allows walls to constrict to control air flow
• Muscle and elastic fibres allow bronchioles to contract and relax easily during ventilation
• Cilia and goblet cells

Question 6

Describe the structure and function of the alveoli

Answer 6

• Function
- Exchanges gases between lungs and blood

• Structure

• Minute air sacs
• Alveoli have one cell thick squamous epithelium
• Surrounded by blood capillaries that have one cell thick endothelium - reduces diffusion pathway
• Constant blood supply means steep concentration gradient is always maintained
• Elastic fibres (elastin) allowing them to stretch during inhalation and recoil during exhalation

Question 7

What does epithelium mean?

Answer 7

• Epithelium tissue consists of epitheilial cells that line organs, cavities within the body, and the surface of the body

Question 8

What does endothelium mean?

Answer 8

• The inner lining of a blood vessel

- Endothelial cells are the cells that make up the endothelium

Question 9

What does cartilage do and where is it found?

Answer 9

• Found in trachea and bronchi
• Offers support
• Prevents lungs from collapsing if pressure drops during exhalation

Question 10

What is the ciliated epithelium and where is it found?

Answer 10

• Found in bronchi, bronchioles and trachea
• Moves mucus along to prevent lung infection by moving it towards the throat where it can be swallowed so pathogens can be destroyed in stomach

Question 11

What are goblet cells and where are they found?

Answer 11

• Found in trachea, bronchi and bronchioles

- Involved in mucus secretion to trap bacteria and dust to reduce risk of infection

Question 12

How does smooth muscle help structures of gas exchange system function?

Answer 12

• They can contract to constrict the airway, and thus controlling the flow of air to and from the alveoli

Question 13

How do elastic fibres help structures of gas exchange system function?

Answer 13

• They stretch when we inhale and recoil when we exhale thus controlling the flow of air

Question 14

What are the intercostal muscles?

Answer 14

• The intercostal muscles are found between the ribs
• There are three layers of intercostal muscles (need to know 2): internal and external
• Internal found on inside
• External found on outside