Gas exchange in humans

Two reasons why humans have to breathe

1. To supply oxygen for respiration which provides the ATP for processes like muscle contract active transport etc

2. Removal of carbon dioxide as when it accumulates, the pH of cells and blood lowers it which could affect ionic balance and tertiary structure of proteins

Name 5 features of the human gas exchange system

1. Trachea

2. Cilia

3. Bronchus

4. Bronchioles

5. Alveoli

Trachea: features and uses

A tube which are kept open by rings of cartilage during pressure changes. Cartilage is separated by muscle and elastic tissue which makes it flexible and so can stretch

Cilia: features and uses

small ??? which moves mucus away from lungs to protect from infection

Bronchus: features and uses

First branch of trachea, allows passage of air into bronchioles - also held open by cartilage

Bronchioles: features and uses

Small branches of the bronchus, only have muscle and elastic fibres so they can contract and relax easily during ventilation

Alveoli: features and uses

Mini air sacs, lined with epithelium and covered with a network of capillaries

What is the word for breathing in?

Inspiration/ Inhalation

What is the word for breathing out?

Expiration/Exhalation

How does inhalation/inspiration work?

To move gases into the lungs the pressure in the lungs must be less than atmospheric pressure

How does exhalation/expiration work?

To move gases out of the lungs the pressure in the lungs must be greater than atmospheric pressure

What is Boyles Law?

That volume and pressure are inversely proportionate. As one decreases the other increases.

How does Boyles Law apply to gas exchange?

When a pressure gradient is present, gases (and liquids) will move from a region of higher pressure to a region of lower pressure down a pressure gradient to reach an equilibrium.

The 6 steps for inhalation/inspiration

Inspiration / Inhalation: (Inhalation -External muscles- decreases IED)

1. The diaphragm contracts (goes from dome to flatten out)

2. External intercostal muscles contract, this moves the ribcage up and out

3. By doing steps 1 & 2, this leads to the increased volume of thorax/lungs

4. Due to Boyle’s law, thoracic pressure (pulmonary pressure) decreases

5. The outside atmospherical pressure is now greater than the inside thoracic pressure : establishing a pressure gradient

6. Therefore air moves in down the pressure gradient

6 steps for exhalation/expiration

Expiration / Exhalation (EI)

1. The diaphragm relaxes (goes from flat → dome)

2. Internal intercostal muscles contract, this moves the ribcage down and in

3. By doing steps 1 & 2, this leads to the decreased volume of thorax/lungs

4. Due to Boyle’s law, thoracic pressure (pulmonary pressure) increases

5. The outside atmospherical pressure is now greater than the inside thoracic pressure : establishing a pressure gradient

6. Therefore air moves out down the pressure gradient

Which steps need energy if it is forced?

Step 2

Is inspiration and active or passive process? Why?

Active - contracting the diagram requires energy

Is expiration and active or passive process why?

Both - relaxing the diaphragm doesn't require energy, but it can be forced and would be active (require energy)

What is the equation for pulmonary ventilation and what is it?

Tidal volume x Ventilation rate

The total volume of air moved by the lungs in one minute

What is the tidal volume?

Tidal volume = volume of air in each breath

What is the breathing rate?

Breathing rate = number of breaths per minute

5 ways in which gas exchange in the alveoli is efficient

1. Branched bronchi and bronchioles ending in millions of alveoli - large surface area for gas exchange

2. RBC’s slowed as they pass through the capillaries - more time for diffusion

3.  RBC’s flattened against capillary wall as they pass - maximum surface area presented for exchange + shortening diffusion pathway

4.  Capillary and alveolar walls very thin - minimum diffusion distance

5.  Ventilation and blood circulation - maintain high diffusion gradient