Module 1

Question 1

Explain the 2 respiratory system zones- conducting and respiratory and their roles.

Answer 1

• Conducting zone- Nose - pharynx -larynx - trachea- bronchi- bronchiole
  This zone allows passage in air into and out of respiratory system and humidifies the air and traps debris and pathogen via incoming air.
• Respirator zone- Terminal bronchiole- alveolar duct- alveolar sack- alveolus
  This zone is for gas exchange through diffusion btw circulator and respiratory system.

Question 2

What is the relationship between surface area and the different respiratory zone?

Answer 2

• The diameter decreases as you come into the respiratory tract and alveoli have a diameter of 0.3mm but they have a much higher cross surface area due to the bifurcation which increases as you come down the respiratory tract.

Question 3

What is the main function of the respiratory zone?

Answer 3

• It allows gas exchange through passive diffusion

Question 4

What type of cells are the higher upper respiratory tract and the alveoli?

Answer 4

• Upper respiratory tract (Nasal, trachea, bronchus, bronchi) has pseudostratified columnar cells-
• Alveoli has squamous cell which are single layered so allow easier diffusion however are most prone to damage, injury and scar that’s why respiratory system prevents any foreign particles from entering.

Question 5

What are the type of alveoli cell?

Answer 5

• Type 1 – pneumocytes- simple squamous that create a very thin diffusion barrier for gases and fluid
• Type 2- surfactant producing cell, a phospholipid that lines the inner alveolar surface to reduce surface tension
• Alveolar macrophages- phagocytic cells that remove foreign debris and pathogen.

Question 6

Why is there a shorter distance btw pulmonary capillary and alveolus and what’s its relation to Fick’s law of diffusion?

Answer 6

• To allow effective gas diffusion
• According to Fick’s law of diffusion, smaller distance= greater rate of diffusion

Question 7

What is the pleura of the lung and its function?

Answer 7

• The pleura is a serous fluid-filled membrane with 2 layer and fluid filled in the middle.
• The inner pleura (touching lung) is visceral pleura
• The outer pleura towards ribcage is parietal pleura.
• The function of the pleura is to: surface tension (helps position the lungs against thoracic wall) , lubrication (reduces friction during breathing) and creates division to isolate the respiratory system from other major organs.

Question 8

How do we breathe?

Answer 8

• We breathe through a -ve pressure system where the pressure inside our chest cavity (lungs) is lower than atmospheric pressure which draws air inwards to out chest cavity as air flows from higher to lower pressure.

Question 9

What is Boyle’s law and how is it related to pulmonary ventilation?

Answer 9

• According to Boyle’s law, the pressure exerted by a given mass on ideal gas is inversely proportional to the volume it occupies hence volume and pressure are inversely proportional hence when applied to pulmonary ventilation when volume increases, the pressure would decrease allowing the air to flow in (an area of lower pressure).
• Pulmonary ventilation refers to air moving in and out of lungs
• Firstly there is change in volume then change in pressure which dictates flow of gases

Question 10

What we breathe in what changes first volume or pressure?

Answer 10

• Volume changes first

Question 11

How is change in volume driven?

Answer 11

• The change in volume is driven by contraction/ relation of intercostal muscle and diaphragm and allowing the change in volume.

Question 12

Explain pulmonary ventilation and the pressures involved and why is intrapleural pressure lower?

Answer 12

• The atm p =760mmhg, intrapleural pressure= 760mmhg, intrapleural pressure= 756 mmhg.
• The intrapleural pressure is lower because the lungs want to recoil whereas the elastic force of the thoracic cage wants to make the thoracic cage expand hence this results in the parietal and visceral pleural being pulled towards the opposite sides leading to increase in volume and decrease in Pressure. Additionally, there is surface tension provided by pleural fluid.

Question 13

What the key factor influencing -ve intra pleural pressure?

Answer 13

• Surface tension- the pleural fluid provides surface tension between the two pleura.
• Elastic force by the lungs (inwards) as elastic tissue in lung wants to recoil and pull lung inward. This pulls visceral pleura inwards
• Elastic force by thoracic/rib cage (outward). The thoracic cage wants to expand hence naturally pull away from the lung. The parietal pleura moves outward as a result.

Question 14

Explain the process of inspiration.

Answer 14

• The inspiration muscle contract
• The diaphragm moves downwards, and the ribcage moves upward and expands.
• Volume in thoracic cavity increase hence intrapulmonary volume also increases
• Intrapleural pressure decreases by (-1 mmhg)
• Intrapleural pressure drops further as an inflated lungs wants to recoil more increasing the intrapleural volume and decrease the pressure more
• Air flows in until pressure equalises.

Question 15

What is transmural/transpulmonary pressure?

Answer 15

• Transpulmonary pressure is the pressure diff across the whole lung, btw alveolar and plural space
  Ptp=Palv-Pip
• It is the force that keeps the lung open.

Question 16

Explain the process of expiration

Answer 16

• In expiration, in quiet expiration no muscles are contracting its done naturally. So the inspiratory muscle relax
• Ribs relax and move downward
• Thoracic volume decreases hence pressure increases
• Elastic lungs recoil passively so intrapulmonary volume decrease and intrapulmonary pressure rises by +1 mmHg
• Air flows our of lung down its pressure gradient until the pressure equalises with atm pressure.