Gas Exchange (6.4)

Question 1

What are the three processes involved in physiological respiration?

Answer 1

Cell respiration
Gas exchange
Ventilation

Question 2

Define cell respiration

Answer 2

Cell respiration happens in the cytoplasm and mitochondria of cells and releases ATP. In humans, oxygen is USED and carbon dioxide is PRODUCED. So oxygen is taken in and carbon dioxide released.

Question 3

Define gas exchange

Answer 3

The exchange of oxygen and carbon dioxide between the alveoli and the bloodstream by passive diffusion.

Question 4

Define ventilation

Answer 4

The exchange of air between the atmosphere and the lungs. i.e. the physical act of breathing.

Question 5

Describe how the three processes of physiological respiration work together

Answer 5

Oxygen is USED by cells in respiration and carbon dioxide is PRODUCED. So oxygen is continually being removed from the alveoli into the bloodstream and carbon dioxide is continually being released.

The lungs function as a ventilation system to keep oxygen levels high and carbon dioxide levels low. A concentration gradient must be maintained in the lungs as gas exchange is a passive process.

Question 6

Describe the movement of air to/in the lungs

Answer 6

Air is inhaled through the nose or mouth and passes through the pharynx to the trachea.

Air travels down the trachea, then divides into two bronchi which connect to the lungs. In each lung, the bronchi divide into many small airways (bronchioles). Each bronchiole terminates with a cluster of air sacs (alveoli). This is where gas exchange with the bloodstream occurs.

Question 7

Structural features of the alveoli

Answer 7

• A thin epithelial layer of cells means the gases only have to diffuse a short distance
• Surrounded by a rich capillary network which increases gas exchange with the blood.
• Roughly spherical in shape (max SA available for gas exchange).
• The inner surface is moist so dissolved gases are able to better diffuse into the bloodstream.

Question 8

What are pneumocytes?

Answer 8

Pneumocytes are the cells that line the alveoli.

Question 9

Describe Type I pneumocytes

Answer 9

Type I pneumocytes make up the wall of the alveoli and are involved in the process of gas exchange from the alveoli to the capillaries.

Question 10

Describe Type II pneumocytes

Answer 10

Type II pneumocytes secrete a pulmonary surfactant which creates a moist surface on the inner surface of the alveoli. This makes it easier to dissolved gases to diffuse into the bloodstream but also reduces surface tension in the alveoli.

Question 11

Describe alveolar macrophages

Answer 11

Alveolar macrophages destroy bacteria and remove particulate matter (dust) from the lungs.

Question 12

What is lung cancer?

Answer 12

The uncontrolled growth of lung cells caused by genetic mutation that lead to the abnormal growth of lung tissue.

Question 13

Causes of lung cancer (Mneumonic)

Answer 13

Radiation
Ageing
Pollution
Environment (eg. radon gas)
Diseases

Genetics (family history)
Occupation (eg. mining)
Asbestos
Tobacco (smoking)
Smoking (second-hand)

Question 14

Four consequences of lung cancer

Answer 14

Short of breath
Hemoptysis (coughing up blood)
Metastasis (spread of cancer to other parts of the body)
Shortened lifespan

Question 15

What is Chronic Obstructive Pulmonary Disease (COPD)?

Answer 15

An umbrella term for two diagnoses.
- Chronic bronchitis (able to be treated)
- Emphysema (irreversible)

Question 16

What is emphysema?

Answer 16

Emphysema is a lung condition where the alveoli enlarge, leading to a lower SA for gas exchange. The main cause of emphysema is smoking because chemical irritants are directly inhaled into the lungs. It is irreversible. Symptoms of emphysema are cyanosis (lack of oxygen to extremities), shortness of breath, phlegm, increased risk of chest infections and an enlarged rib cage.

Question 17

What happens during inhalation and exhalation?

Answer 17

During inhalation the external intercostal muscles contract and the ribcage moves up and out. The diaphragm contracts and moves downwards. So, the volume of the thorax (chest cavity) increases and pressure decreases (due to Boyle’s Law). Air flows into the lungs to even the pressure.

During exhalation the internal intercostal muscles contract and the ribcage moves down and in. The diaphram relaxes and moves outwards. So, the volume of the thorax decreases and the pressure increases. Air flows out of the lungs until pressure evens out.