Chapter 22: gas exchange

Question 1

What are the three processes of gas exchange in humans?

Answer 1

Gas exchange: the exchange of O2 and CO2 between organism and its environment:
1. Breathing (ventilation)
2. Transport O2 and CO2 in blood
3. Exchange of gases with body cells

Question 2

What features of respiratory surfaces are important for gas exchange

Answer 2

The respiratory surface must be:
* Moist, gases must be dissolved in water to diffuse.
* Thin, to facilitate diffusion.
* High surface area, to maximize exchange.

Question 3

What path does air take when its inhaled?

Answer 3

Air is inhaled into nasal cavity, then pass through:
Pharynx
Larynx (contain vocal chords)
Trachea (tube of rings of cartilage)
From trachea, air travels in 2 direction via bronchi into lungs
Bronchi narrows into bronchioles
At end of bronchioles are sacs called alveoli

Question 4

Describe the structure of alveoli and how their structure reflects their function

Answer 4

Alveoli are clusters of air sacs at ends of small bronchioles and are the site of gas exchange (O2 diffuses into blood, CO2 diffuses out of blood):
* High SA
* Close contact with extensive network of blood capillaries
* Inner surfaces coated with surfactant, which prevents alveolar walls from sticking together

Question 5

Explain the toxic effects of smoking on the respiratory system

Answer 5

Air pollutants can cause damage to alveoli and other lung structures.
Smoking can lead to chronic obstructive pulmonary disease:
Breakdown of alveolar walls → alveoli lose elasticity → inability to exhale .

Question 6

Explain how inhalation and exhalation work in terms of air pressure

Answer 6

Inhalation:
* During inhalation (inspiration), the combined actions of the diaphragm and external rib muscles contracting causes the volume of the lungs increase, which causes the pressure to decrease (become more negative). This results in air flowing into the lungs. Diaphragm and rib muscle contract (moves down); ↑ chest cavity volume and ↓ air pressure inside alveoli.
* Gas moves from an area of relatively high pressure (outside) to an area of relatively low pressure (lungs).

Exhalation:
* Diaphragm and rib muscles relax; ↓ chest cavity volume and ↑ air pressure inside alveoli.
* Gas moves from an area of relatively high pressure (lungs) to an area of relatively low pressure (outside).

Question 7

How is breathing controlled by the nervous system?

Answer 7

Usually controlled by autonomic nervous system:
* Breathing control centers in brainstem detect changes in blood pH that signal dissolved CO2 in blood and regulate breathing accordingly.

Question 8

How does gas exchange happen at lung capillaries?

Answer 8

Right side of heart pumps (oxygen-poor) blood lung capillaries:
* CO2 moves from an area of high partial pressure (capillaries) to an area of low partial pressure (alveoli).
* O2 moves from an area of high partial pressure (alveoli) to an area of low partial pressure (blood).

Question 9

How does gas exchange happen at tissue capillaries?

Answer 9

Left side of heart pumps (oxygen rich) blood to tissue:
* Oxygen moves from area of high partial pressure (capillaries) to low partial pressure (tissue).
* CO2 moves from area of high partial pressure (tissue) to low partial pressure (capillaries).

Question 10

Describe the structure of hemoglobin and how its structure reflects its function

Answer 10

Hemoglobin: protein in red blood cells that consists of 4 polypeptide chains and iron-containing heme groups.
* Oxygen diffuses from lungs and binds to iron.