Human Gas Exchange

Question 1

How do humans face large organism problems?

Answer 1

• They reduce water loss by:
• making gas exchange surfaces occur inside the body and air have contact with exchange surfaces inside the body
• having water proof coating on the outside of the body
• having a breathing system to allow a high rate of gas exchange

Question 2

What are lungs?

Answer 2

A pair of lobed structures made of highly branched bronchioles

Question 3

What is a broncus?

Answer 3

Divisions of the trachea that each lead to one lung

Question 4

What is the function of broncus?

Answer 4

they produce mucus to trap dirt and cilia to move this mucus to the throat

Question 5

What supports the broncus?

Answer 5

cartilage

Question 6

Describe the structure of a cartilage.

Answer 6

• inner wall = layer of glandular and connective tissue, elastic fibres, smooth muscle and blood vessels
• outer wall = ciliated epithelium and goblet cells

Question 7

What are broncheoli?

Answer 7

A series of branching subdivisions of the bronchi

Question 8

Describe the structure of broncheoli.

Answer 8

They consist of walls made of muscle lined with epithelial cells

Question 9

What is the function of broncheoli?

Answer 9

their muscles enable constriction in order to control airflow through the alveoli

Question 10

Describe the alveoli.

Answer 10

• Small air sacks
• located at the end of the bronchioles
• Some collagen and elastic fibres are locate between the alveoli
• lined with epithelial cells
• alveolar membrane is the gas exchange surface
• surrounded by capillaries
• one cell thick

Question 11

How are the alveoli adapted for gas exchnage?

Answer 11

• the walls of both alveoli and capillaries are very thin and therefore the distance over which diffusion takes place is very short
• alveoli and pulmonary capillaries have a very large total surface area
• constant blood flow through the pulmonary capillaries which maintains a concentration gradient

Question 12

Describe the process of inhalation.

Answer 12

• During the process of inspiration, the external intercostal muscles contract, while the internal intercostal muscles relax
• The ribs are pulled upwards and outwards which increase the volume of the thorax
• The diaphragm muscles contract
• The increased volume of the thorax results in the reduction of pressure in the lungs
• Atmospheric pressure is now greater than the pulmonary pressure, so air is forced into the lungs