Respiratory System

Question 1

Breathing vs Respiration

Answer 1

• Breathing is the movement of air in and out of the lungs.

• Respiration is the chemical reaction that occurs in cells converting oxygen into usable energy for the cells.
Which produces carbon dioxide as a waste product.
• Glucose + Oxygen -> Carbon Dioxide + Water + Energy

Question 2

The Respiratory System

Answer 2

• The function of the respiratory system is to take in oxygen from the external environment and pass out waste carbon dioxide.
• The respiratory system is made of a series of branching tubes from our nose and mouth to the tiny air sacs called alveoli where gas exchange occurs.

Question 3

Lungs (Pathway of air)

Answer 3

• Covered by 2 layers of membrane called the Pleural Membrane (or Pleura). The inner layer is attached to the lungs and the outer layer attached to the thoracic cavity
• Between the 2 layers of membrane is the pleural fluid which holds the lungs against the inside of chest wall (sticks the two layers together) and also allows lungs to slide as we breathe.

Question 4

Nose/Nasal Cavity (Pathway of air)

Answer 4

• Filters, warms, and moistens air in preparation for entering lungs.
• Smell receptors are stimulated by substances in the air.
• Acts as a Resonating chamber that enhances sounds produced in speech.
• Hairs and mucous trap foreign particles

Question 5

Pharynx (Pathway of air)

Answer 5

• The throat section
• Air passes through pharynx from nasal cavity to larynx.
• Also used to pass food from mouth into oesophagus.

Question 6

Larynx (Pathway of air)

Answer 6

• Air passes from pharynx to trachea
• Allows for speech – vocal cords vibrate to make sound

Question 7

Trachea (Pathway of air)

Answer 7

• Carries air from larynx to lungs
• Made of c-shaped bands of cartilage that give flexibility and support
• Lined with mucous membrane and cells with cilia to trap any solid particles
• Cilia beat to move mucous and trapped particles upwards

Question 8

Bronchi (Pathway of air)

Answer 8

• Two bronchi branch from the trachea, one left and one right.
• Singular = Bronchus
• Divide into secondary and tertiary bronchi

Question 9

Bronchioles (Pathway of air)

Answer 9

• Very fine tubes that pass air from bronchi to alveoli
• End in tiny air sacs, the alveoli

Question 9

Alveoli (Pathway of air)

Answer 9

• Tiny air sacs that are found in clusters on the ends of bronchioles
• They have very thin walls
• Surrounded by blood capillaries
• Location of gas exchange (oxygen and carbon dioxide)
• The cells of the alveoli secrete alveolar fluid that keeps the surface of the alveoli moist.
• The fluid contains surfactant which helps prevent the alveoli from collapsing and assists in the diffusion of gases

Question 10

Gas Exchange

Answer 10

• Gas Exchange – is the process of oxygen diffusing from the alveoli into the blood and carbon dioxide diffusing from the blood into the alveoli in the lungs.
• The Diffusion of gases into and out of the blood can only occur when they are dissolved in fluid -> alveolar fluid
• When we inhale, there is a high concentration of oxygen in the alveoli and a low concentration of oxygen in the blood coming to the lungs (from the heart). -> So, oxygen diffuses from alveoli into the blood.
• At the same time, there is a high concentration of carbon dioxide in the blood (waste product of respiration in the cells) and a low concentration in the alveoli. -> So, it diffuses from blood into alveoli and is exhaled.

Question 11

Concentration Gradient (Gas Exchange)

Answer 11

• Blood constantly moving through the capillaries surrounding the alveoli (so there is always ‘new’ blood that is low in O2 arriving to become oxygenated).
• Constant inhaling and exhaling, bring ‘new’ air into the alveoli to be exchanged
• The same process of gas exchange occurs between the blood and all the other cells of the body

Question 12

Why the lungs are suited for Gas Exchange

Answer 12

• Many alveoli and convoluted structure = Large surface area. This allows large amounts of gas to be exchanged quickly
• Each alveoli is covered in capillaries = blood is as close to the air in alveolus as possible. This means the gases don’t have to travel very far.
• Walls of alveoli and capillaries are only 1 cell thick. This means the gases don’t have to travel very far into or out of the blood.
• The lungs are positioned deep inside the body. This prevents excessive evaporation of the fluids that cover the alveoli surfaces. This is important as gases can only diffuse into and out of the blood when they are dissolved in fluid.
• The lung volume can be changed by movements of the muscles so air flows into and out of the lungs. This ensures there is always a concentration difference of the gases

Question 13

Other Respiratory Structures

Answer 13

Ribs: Framework that protects/supports the chest

Intercostal muscles: muscles between the ribs, they contract to lift the rib cage and increase the volume of the thoracic cavity

Diaphragm: Dome-shaped muscle that separates the chest from the abdomen. It contracts (flattens) to increase the volume of the cavity

Internal Intercostal muscles: Contract to pull ribs in and down
External Intercostal muscles: Contract to pull ribs up and out. Relax to let the ribs contact

Pleural membrane: Double-layered membrane
• Inner Layer covers the lungs
• Outer layer attached to the inside of the ribs
• Aids the expansion and contraction of the lungs during breathing

Pleural Fluid:
• Sits between the layers of pleural membrane
• Lubrication for the movement (expansion and contraction) of the lungs

Question 14

Mechanics of Breathing

Answer 14

• The process of moving air into and out of the lungs is called VENTILATION
• Inspiration / Inhalation – air moving into lungs
• Expiration / Exhalation – air moving out of lungs

Question 15

Inspiration

Answer 15

• For air to flow into lungs, air pressure inside lungs must be less than air pressure outside the body.

To achieve this, we increase the volume of the lungs:
• Diaphragm contracts moving downwards
• Intercostal muscles contract moving up and outwards
• This increases lung volume, which decreases air pressure inside lungs
• Air flows into lungs from a higher pressure (outside body) to a lower pressure (inside lungs) until pressure becomes equal

Question 16

Expiration

Answer 16

• For air to flow out of lungs, air pressure inside lungs must be higher than air pressure outside the body.

To achieve this, we decrease the volume of the lungs:
• Diaphragm relaxes moving upwards
• Intercostal muscles relax moving down and inwards
• This decreases lung volume, which increases air pressure inside lungs
• Air flows out of lungs from a higher pressure (inside lungs) to a lower pressure (outside body) until pressure becomes equal

Question 17

Lung Tidal Volume

Answer 17

• Tidal volume: volume of air that is inhaled and exhaled in only a single breath
• Inspiration reserve volume: max volume of air that can be inhaled from the end-inspiratory level
• Expiratory reserve volume: max volume of air that can be exhaled from the end-expiratory level.
• Vital Capacity: Max volume breathed after deepest inhalation
• Residual Volume: Volume of air remaining in lungs after max exhalation
• Total Lung Capacity: Volume of lungs at max inflation (Vital Capacity + Residual Volume)

Question 18

Carrying Oxygen in the Blood

Answer 18

Oxygen has diffused through the capillary walls into the bloodstream:
• 3% dissolves into the plasma
• 97% binds to the haemoglobin molecule in the red blood cell to form oxyhaemoglobin

One haemoglobin molecule can hold 4 oxygen molecules:
• The oxygen will bind to the haemoglobin molecule readily when oxygen concentration is high such as in the alveoli.
• Oxyhaemoglobin will break down again where oxygen concentrations are low, such as the cells of the body.

Question 19

Carrying Carbon Dioxide in the Blood

Answer 19

• 8% dissolves into the plasma
• 22% binds to the haemoglobin molecule in the red blood cell to form carbaminohaemoglobin

70% will react with the water in the plasma to form bicarbonate ions (HCO3-):
• The bicarbonate ions form as a result of CO2 reacting with H2O when it is diffuse into the blood forming carbonic acid.
• The carbonic acid then dissociates into Hydrogen ions and Bicarbonate ions
• When CO2 is being exhaled, it must be transported from the blood back to the alveoli:
• The CO2 dissolved in the plasma diffuses out of the blood
• The carbaminohaemoglobin breaks down and the CO2 diffuses out of the blood
• The H+ and HCO3- ions recombine to form H2CO3, which then breaks down into CO2 and H2O, so the CO2
can diffuse out.