9. human gas exchange

Question 1

describe the features of gas exchange in humans

Answer 1

1. large surface area - allow faster diffusion of gasses
2. thin surface - ensure diffusion distances remain short
3. good blood - maintain high concentration gradient so diffusion occurs faster
4. air supply - diffusion gradients can be maintained

Question 2

state the percentage of nitrogen in atmospheric air

Answer 2

inspired air : 79%
expired air : 79%

Question 3

state the percentage of oxygen in atmospheric air

Answer 3

inspired air : 21%
expired air : 16%

Question 4

state the percentage of carbon dioxide in atmospheric air

Answer 4

inspired air : 0.04%
expired air : 4.0%

Question 4

identify and label the breathing system

Question 5

State the characteristics of, and describe the role of, the exchange surface of the alveoli in gas exchange

Answer 5

• provide large surface area for gaseous exchange
• very think wall provide short distance for easy and fast diffusion of gasses through it
• walls are covered with layer of water to dissolve gasses for diffusion to occur in solution
• Surface is richly supplied with blood capillaries for rapid transport of gasses away from lungs, maintaining a diffusion gradient for efficient gas exchange

Question 6

explain the role of ribs, the internal and external intercostal muscles and the diaphragm in producing volume and pressure changes in the thorax, causing the movement of air into and out of the lungs

Answer 6

in order for air to move into lungs
pressure inside thorax must be lower than atmospheric pressure of the air outside

in order for air to move out of the lungs
pressure inside thorax must be higher than outside

when volume of the thorax increases, pressure decreases and vice versa

Question 6

Identify on diagrams and images, the ribs, internal and external intercostal muscles and the diaphragm

Question 7

what happens during inspiration

Answer 7

ribs - move upwards

internal intercostal muscles - relax

external intercostal muscles - contract

diaphragm - contracts + flatten

Question 8

what happens during expiration

Answer 8

ribs - downwards + inwards

internal intercostal muscles - contract

external intercostal muscles - relax

diaphragm - relax + dome-shape

Question 8

explain the role of goblet cells, ciliated cells and and mucus in protecting the gas system from pathogens and particles

Answer 8

goblet cells - secrete mucus

ciliated cells - move germ particles away from airways by beating of cillia

mucus - trap germ and dust