6.4 - Respiratory System

Question 1

Gas exchange in humans

Answer 1

Oxygen is absorbed into the blood in capillaries from the air in the alveoli
- oxygen concentration in fresh air > capillaries
CO2 is released into the air in alveoli from the blood in capillaries
- CO2 concentration in capilaries > air

Ventilation: maintains concentration gradient for gas exchange by pumping fresh air into alveoli and removing stale air

Question 2

Alveoli

Answer 2

• sacs in lungs to increase surface area for gas exchange
  - single layer cell wall: decrease distance for diffusion
  increasing rate of gas exchange
• type I pneumocytes: flat and thin epithelium cells for efficient gas exchange
• type ii pneumocytes: epithelium cells that secrete surfactant to provide moisture (surface for dissolved oxygen and co2) prevent adhesion and collapse of alveoli (when air is exhaled)

Question 3

Air trajectory

Answer 3

1. Mouth/nose
2. trachea: cartilage rings preventing collapse when pressure inside is low (exhale)
3. 2 bronchi: branching off to each lung made of cartilage rings
4. bronchioles: branches made of smooth muscle fibres to vary in size
5. alveoli: site for gas exchange, single-cell layer, high SA

Question 4

Ventilation process

Answer 4

Ventilation: repeating inspiration and exhalation to maintain concentration gradient for gas exchange

inhalation:
- external intercostal muscles + diaphragm contract expanding ribs
- lung volume increase, pressure decreases
- pressure gradient: pressure in lungs < outside environment
- air flows into lungs, from high to low pressure

exhalation:

• internal intercostal muscles + abdomen contracts
• lung volume decreases, increasing pressure
• pressure gradient: pressure in lungs > environment
• air flows out of lungs, from high to low

Question 5

Antagonistic muscles

Answer 5

pairs of muscles that cause opposite movements, one contracts while the other relaxes

external + internal intercostal muscles
abdomen + diaphragm

Question 6

Causes + consequences of lung cancer

Answer 6

causes:

• smoking
• air pollution
• dust from mining/ construction sites
• second-hand smoke
• gas leaks

consequences:
- death
- removal of lung or parts
- chest pain
shortness of breath/ difficulty breathing
- weightloss
- fatigue
- coughing up blood

Question 7

Causes and consequences of emphysema

Answer 7

emphysema: chronic disease with few large alveoli with thick walls making gas exchange less efficient (decreased SA, increased distance for diffusion)

Causes: (elastase is released when phagocytes digest bacteria, elastase digests lung tissue)

• smoking increases bacteria in alveoli
• smoking reduces effectiveness of A1AT that inhibits elastase from digesting lung tissue
• genetic factors reduces effectiveness of A1AT

Consequences:

• increases CO2 blood concentration
• decreases oxygen blood concentration
• fatigue
• shortness of breath
• laboured breathing
• rapid ventilation