Gas Exchange Humans 3

Question 1

What is the main site of gas exchange in mammals?

Answer 1

The site of gas exchange in mammals is the epithelium of the alveoli

Question 2

What are alveoli?

Answer 2

Minute air sacs that are within the lungs

Question 3

What is required to ensure a constant supply of oxygen to the body?

Answer 3

A diffusion gradient must be maintained at the alveolar surface

Question 4

What is required for efficient transfer of materials?

Answer 4

• Thin partially permeable surfaces

* large surface area to volume ratio

Question 5

What is required to maintain a diffusion gradient?

Answer 5

Movement of both the environmental medium and internal medium

Question 6

Why are exchange surfaces located inside an organism?

Answer 6

Because they are thin, they can be damaged easily, they are within the organism for protection.

Question 7

Why is mass transport required in mammals?

Answer 7

• Diffusion alone is not fast enough to maintain adequate transfer of oxygen and carbon dioxide along the various components of the lungs.What
• Breathing is mass transport

Question 8

Why is diffusion of gasses between alveoli and blood very fast?

Answer 8

• Red blood cells are slowed as they pass through pulmonary capillaries, allowing more diffusion time
• Distance between alveolar air and red blood cells is small, as red blood cells are flattened against the capillary walls
• Walls of both alveoli and capillaries are very thin, this decreases the distance over which diffusion takes place
• Alveoli and pulmonary capillaries have a very large surfaces area
• Breathing constantly ventilates the lungs, and the heart constantly circulates blood around the alveoli, this ensure a steep concentration gradient of the gases to be exchanged is maintained
• Blood flow through the pulmonary capillaries maintains a concentration gradient

Question 9

Why is there a big surface area for exchanging oxygen and carbon dioxide?

Answer 9

There are many alveoli in the lungs

Question 10

What are the alveoli surrounded by?

Answer 10

Network of capillaries

Question 11

How does gas exchange occur in the lungs?

Answer 11

• Oxygen from the air moves down the trachea > bronchi > bronchioles and the alveoli
• This movement occurs down a pressure gradient
• In the alveoli, the oxygen diffuses across the alveolar epithelium, then the capillary endothelium ending up in the capillary
• This movement occurs down a diffusion gradient

Question 12

What maintains a concentration gradient?

Answer 12

Blood flow through the

capillaries

Question 13

What features of the lungs speed up rate of diffusion?

Answer 13

• Thin Exchange Surface, only one cell thick, short diffusion pathway
• Large Surface Area, large number of alveoli means there is a large surface area

Question 14

What does lung disease affect?

Answer 14

• Ventilation

* Gas exchange

Question 15

What is tidal volume?

Answer 15

Tidal volume is the volume of air in each breath

Question 16

What is ventilation rate?

Answer 16

Number of breaths per minute

Question 17

What is forced expiratory volume?

Answer 17

Maximum volume of air that an be breathed out in 1 second

Question 18

What is forced vital capacity?

Answer 18

Maximum volume of air it is possible to breathe forcefully out of the lungs after a deep breath

Question 19

How does the immune system respond to TB in the lungs?

Answer 19

• Immune system cells build a wall around the bacteria in the lungs, to form small hard lumps called tubercles

Question 20

How does TB affect the lung?

Answer 20

• Infected tissue within the tubercles dies, and gas exchange surface is damaged, so tidal volume is decreased
• TB will also cause fibrosis, which reduces tidal volume even further

Question 21

What are the effects of a reduced tidal volume?

Answer 21

• Less air can be inhaled with each breath
•In order to take in enough oxygen, patients have to breathe faster, ventilation rate is increased
Common symptoms include:
• persistent cough
• coughing up blood and mucus
• chest pains
• shortness of breath
• fatigue