Topic 15: Aerobic Function

Question 1

What is partial pressure?

Answer 1

Partial pressure is the pressure of a gas within a solution of gases

Question 2

Trace the flow of air into the body beginning at the nose and ending at the alveoli

Answer 2

Air gets through the nose to nasal cavity to pharynx where air and food coincides. It continues down to the larynx and then trachea which runs in the middle of our chest. The trachea branches into right and left bronchus which continues to divide and come down into bronchiole and finally, millions of alveoli.

Question 3

Describe why expansion of the thoracic cavity also expands the lungs

Answer 3

The lungs and thoracic cavity have no connective tissues in between, but instead, a specialised double membrane called pleural cavity. Visceral pleura is the membrane attached to the lung, parietal pleura is the membrane attached to the ribcage, and there is pleural fluid in between.

The hydrogran bonds of this fluid creates surface tension which “sticks” the lungs and rib cage together –> expand together

Question 4

Explain why breathing in (inspiration) is an active process compared to the breathing out (expiration)

Answer 4

Inspiration involves the contraction of diaphragm, made up of skeletal muscles, which requires energy. Meanwhile, in expiration, the muscles relax in a passive process.

Question 5

List the mechanisms of how gases are transported in the body

Answer 5

Gas exchange depends on the partial pressure gradient to diffuse from one area to another.
- O2 is primarily transported by haemoglobin
+ 98% by haemoglobin
+ 2% dissolved in plasma

• CO2: 3 mechanisms:
  + 7% dissolved in plasma
  + 93% within RBC - 23% bound to haemoglobin
  - 70% converted into bicarbonate

Question 6

Describe the negative pressure mechanism in inspiration

Answer 6

Negative Pressure is present because some air is trapped in the airways, creating dead space in the lung –> lower pressure in our lung –> flattening diaphragm and expanding chest to pull air in.

Question 7

Describe the differences between right and left lung

Answer 7

Right lung has 3 lobes (superior, middle, inferior) and left lung has 2 lobes (superior, inferior) allowing space for the heart (cardiac notch)

Question 8

What is the functional unit of the lung?

Answer 8

Alveoli: terminal sacs, exchange sites for gases

Question 9

What factor deciding the exchange rate and how do alveoli and capillaries ensure that?

Answer 9

Diffusion distance decides the exchange rate. So, there are millions of alveoli providing a large surface area and the capillaries bed intertwine very closely with alveoli, ensuring rapid exchange.

Question 10

Describe different types of alveoli

Answer 10

• Type 1: gas exchange site
• Type 2: secretes surfactant which minimize surface tension and prevent alveoli from collapsing

Question 11

List and describe some lung volumes and capacities indicators

Answer 11

• Tidal volume: the total amount of air into or out of lung after each breath
• Residual volume: the minimum air volume in lung after maximum deflation (keeps the alveoli from collapsing
• Inspiratory reserve volume: amount of air can be taken in more after tidal volume
• Expiratory reserve volume: amount of air can be exhaled more after tital volume
• Vital capacity: the maximum of air can be exhaled after maximum inhalation

Question 12

What needs to be remembered about deflation of the lungs?

Answer 12

Lungs are never deflated completely as a way to prevent alveoli collapse and as a safety mechanism

Question 13

What is pneumothorax?

Answer 13

Collapsed lung caused by H bonds being broken. As lungs are elastic in nature, they will shrivel down.