Unit 6.4 - Ventilation and Gas exchange

Question 1

Need for ventilation

Answer 1

Cell respiration happens in the cytoplasm and mitochondria and releases energy in the form of ATP for use inside the cell - in humans exygen is used in cell respiration and carbon dioxide is produced - humans must take in oxygen from their surroundings and release carbon dioxide.

Question 2

Gas exchange

Answer 2

the process of swapping one gas for another is called gas exchange. Happens by diffusion in the alveoli of human lungs. depends on the concentration gradients of oxygen and carbon dioxide between the air in the alveoli and blood in adjacent capillaries. To maintain gradient air in the alveoli must be refreshed frequency - ventilation.

Question 3

Ventilation system

Answer 3

trachea
bronchus
bronchioles
diaphragm
left lung
intercostal muscles

Question 4

Ventilation Rate and Tidal Volume

Answer 4

Ventilation rate = number of inhalations per minute
Tidal volume = volume of air taken in or out with each inhalation or exhalation

Question 5

Monitoring Ventilation rate

Answer 5

can be done by simple data logging
- inflatable chest belt placed around the thorax and air is pumped in with a bladder
- differential pressure sensor then used to measure pressure variations inside the chest belt due to chest expansions
- ventilation rate can be deduced and also the relative size of ventilations

Question 6

Monitoring Tidal Volumes

Answer 6

measured using a spirometer
- can be made using a bell jar with volumes marked on it placed in a pneumatic trough
- tube is used to breathe out into the bell jar so the expired volume can be measured - many designs of digital versions
- Graphs to show the tape of data generated with a spirometer : Tidal volume = how much the lung volume increases or decreases with each ventilation. Ventilation rate = counting number of ventilations and measuring the time (x axis)

Question 7

Ventilation of lungs

Answer 7

Muscle contractions cause pressure changes inside of the thorax that force air in and out of the lungs to ventilate them
Different muscles are required for inspiration and expiration because muscles only do work when they contract - muscles that cause opposite movement from each other are antagonistic muscles

Question 8

Inhaling

Answer 8

• external intercostal muscle contract moving the ribcage up and out
• diaphragm contracts becoming flatter and moving down
• these muscle movements increase the volume of the thorax
• pressure inside the thorax therefore drops below atmospheric pressure
• Air flows into the lungs from outside the body until the pressure inside the lungs rises to atmospheric pressure

Question 9

Exhaling

Answer 9

• Internal intercostal muscles contract moving the ribcage down and in
• abdominal muscles contract pushing the diaphragm up into a dome shape
• These muscles movements decrease the volume of the thorax
• The pressure inside the thorax therefore rises above atmospheric pressure
• Air flows out from the lungs to the outside of the body until the pressure inside the lungs falls to atmospheric pressure

Question 10

Adaptations of the alveoli for gas exchange

Answer 10

• permeable to oxygen and carbon dioxide
• large surface area for diffusion
• thin, so the distance for diffusion is small
• moist so that oxygen can dissolve

Question 11

Type 1 pneumocytes

Answer 11

Extremely thin and permeable alveolar cells that are adapted to carry out gas exchange - most of the wall of the alveolus consists of a single layer of these thin cells - gases only have to diffuse a very short distance

Question 12

Blood Capillaries

Answer 12

alveolus covered by a dense network of blood capillaries with low oxygen and high co2 concentrations. Oxygen therefore diffuses from the air in the alveolus to the blood and carbon dioxide diffuses in the opposite directions

Question 13

Type 2 pneumocytes

Answer 13

Cells in the alveolus that secrete a fluid to keep the inner surface of the alveolus moist and allow gases to dissolve. Fluid also contains a natural detergent (surfactant) to prevent the sides of the alveoli from sticking together by reducing surface tension.

Question 14

Lung Cancer Causes

Answer 14

five main causes of lung cancer = Smoking - tobacco smoke contains many mutagens that causes cancer to develop
Passive smoking - exhaled breath from smokers passes carcinogens on to others
Air pollution - many sources include diesel exhaust fumes nitrogenous oxides
Radon gas - in some areas it leaks out of rocks especially granite
Asbestos and silica- dust from these materials causes cancer if deposited in lungs

Question 15

Epidemology

Answer 15

study of the incidence and causes of disease - survey used to look at correlations between disease rates and factors that could be implicated

Question 16

Lung Cancer consequences

Answer 16

1) difficulties with breathing
2) persistent coughing
3) coughing up blood
4) general fatigue
5) chest pain
6) loss of apetite
7) weight loss

Question 17

Emphysema Causes

Answer 17

main causes -
1) smoking and pollution = cilia that line the airways and expel mucus are damaged and cease to function - mucus builds up in the lungs causing infections
Toxins in cigarette smoke = inflammation and damage to ehw white blood cells that fight infections in the lungs
– protease (trypsin) released from inflamed cells and damaged white blood cells - this enzyme digests elastic fibres in the lungs and eventually causes complete breakdown of alveolus wall - big large air sacs

Question 18

Emphysema Consequences

Answer 18

chronic and progressive disease with serious consequences - oxygen saturation in blood falls and exercise more and more difficult .
Lungs lose elasticity making it increasingly difficult to exhale
Mucus causes coughing and wheezing