Gas Exhange In Humans

Question 1

Why do mammals have a high metabolic and respiratory rate?

Answer 1

Because they need to maintain a constant body temperate and are very active. Absorb large volumes of oxygen for aerobic respiration and remove large volumes of carbon dioxide

Question 2

Why are specialised ventilation mechanisms and exchange surfaces required?

Answer 2

In multicellular organisms, diffusion alone isn’t fast enough to maintain adequate transfer of oxygen and carbon dioxide and the distances are too great

Question 3

Describe the path or air from environment to lungs in a human

Answer 3

1. Air
2. Mouth/nose
3. Trachea
4. Bronchi
5. Bronchioles
6. Alveoli
7. Blood capillaries

Question 4

Label the diagram

Answer 4

Question 5

Describe and explain the structure and function of trachea

Answer 5

• flexible tube supported by C rings of cartilage - prevent trachea from collapsing when the pressure decreases inside during inspiration
• tracheal walls contain muscle and are lined with ciliated epithelial cells and goblet cells that produce mucus

Question 6

Describe and explain structure and function of bronchi

Answer 6

• similar structure to trachea
• contain goblet cells and produce mucus which traps dirt particles and pathogens
• ciliated epithelial cells then waft the mucus and trapped particles to the throat where they are swallowed and digested
• supported by cartilage

Question 7

Describe and explain structure and function of bronchioles

Answer 7

• walls contain smooth muscle which contract to cause constriction which can be used to control air flow ina me out of the alveoli
• lined with epithelial cells and goblet cells

Question 8

Describe and explain the structure and function of alveoli

Answer 8

• small air sacs found at the end of bronchioles
• made from squamous epithelial cells
• one cell think for short diffusion pathway
• collagen and elastic tissue between alveoli which stretches during inspiration to prevent alveoli busting and will recoil during expiration to expel air that has a higher concentration of carbon dioxide

Question 9

What is alveoli’s role in gas exchange?

Answer 9

Epithelium wall of alveoli is site of gas exchange

To ensure effect gas exchange:
• large surface area - allows more molecules to diffuse quickly ( 300 million alveoli in each human lung)
• thin and permeable - provide short diffusion pathway and gas can diffuse quickly and water is lost the walls are moist
• large pulmonary capillary network - carries oxygen away from alveoli and returns carbon dioxide to the alveoli and helps maintain a steep concentration gradient
• surfactant is produced - reduces surface tension and prevents the alveoli walls sticking together

Question 10

Label diagram

Answer 10

Question 11

Why is diffusion of gases between alveoli and blood very rapid?

Answer 11

• red blood cells are slowed as they pass through the pulmonary capillaries allowing more time for diffusion
• short distance between alveolar air and red blood cells as red blood cells are flattened against capillary walls
• walls of alveoli and capillaries are very thin and give a small diffusion pathway
• alveoli and capillaries have a very large total surface area for diffusion
• breathing movements ventilate the lungs and maintain a step concentration gradient for faster diffusion
• action of the heart pumping blood through the pulmonary capillaries maintains a steep concentration gradient for faster diffusion

Question 12

Look at table of percentage composition by volume

Answer 12