Human Gas Exchange

Question 1

How do humans face reduced surface area to volume ration, caused by them being a large organism?

Answer 1

they change their shape to increase it and they develope breathing systems that:

• reduces the long diffusion pathway
• maintains a steep concentration gradient

Question 2

What is the function of broncus?

Answer 2

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

Question 3

What supports the broncus?

Answer 3

cartilage

Question 4

What are broncheoli?

Answer 4

A series of branching subdivisions of the bronchi

Question 5

Describe the structure of broncheoli.

Answer 5

They consist of walls made of muscle lined with epithelial cells

Question 6

What is the function of broncheoli?

Answer 6

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

Question 7

Describe the alveoli.

Answer 7

• 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 8

How are the alveoli adapted for gas exchnage?

Answer 8

• 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 9

Describe the process of inhalation.

Answer 9

• diaphram contracts and therefore flattens
• the external intercostal muscles contract, while the internal intercostal muscles relax
• The ribs are pulled upwards and outwards
• volume increases and pressure decreases in the thoratic cavity
• Atmospheric pressure is higher than that in the lungs therefore so air is moves into the lungs down the pressure gradient

Question 10

Describe the process of exhalation.

Answer 10

• diaphram relaxes and therefore moves upwards
• the internal intercostal muscles contract, while the external intercostal muscles relax
• The ribs are pulled downwards and inwards
• volume decreases and pressure increases in the thoratic cavity
• Atmospheric pressure is lower than that in the lungs therefore so air is moves out of the lungs down the pressure gradient

Question 11

How does air travel between the blood and the alveoli?

Answer 11

it diffuses down the concentration gradient through the epethium lining the alveoli and the endothelium lining the capillaries

it occurs the otherway round if CO2