B11 Gas exchange

What is the breathing system?

The organ system that allows the body to obtain oxygen for aerobic respiration and to remove carbon dioxide as a waste product

Label this diagram

When you breathe what is the pathway the air takes?

nose/mouth → larynx → trachea → bronchi → bronchioles → alveoli

Lungs explanation

the main organs in the respiratory system, containing the surfaces where gas exchange takes place

Ribs and intercostal muscles explanation

Intercostal muscles are found between the ribs.

Internal and external intercostal muscles work antagonistically in pairs to expand and contract the rib cage during breathing.

The ribs also protect the lungs and heart from physical damage.

Larynx explanation

contains the vocal cords.

Trachea explanation

connects the throat to the bronchi. C-shaped cartilage rings are present to provide structural strength, keeping the trachea open so that air can pass through it.

Bronchi explanation

hollow tubes composed of cartilage rings that carry air from the trachea to the lungs. The bronchi splits into two tubes to enter the left and right lung, before branching further inside the lungs.

Bronchiles explanation

Smaller tubes which branch off from the bronchi in the lungs, leading to the alveoli.

Alveoli explanation

Where gas exchange occurs

How does gas exchange happen?

Happens at the surface of the alveoli. Oxygen diffuses across the wall of the alveoli from the air into the blood in the capillaries.

Carbon dioxide diffuses across the wall of the alveoli from the blood capillaries into the air

How are alveoli adapted for gas exchange?

large surface area- more efficient diffusion as more gas can diffuse at once

thin surface- short diffusion distance

good blood supply- maintains concentration gradient

good ventilation with air- that waste gases can diffuse out of the blood into the air in the lungs whilst oxygen diffuses into the blood.

What is breathing/ventilation?

the act of moving air into and out of the lungs to allow gas exchange to occur

How does breathing in/inhaling happen?

1. internal intercostal muscles relax

2. external intercostal muscles contract, pulling the ribs up and out

3. the diaphragm flattens/contracts down which causes the volume in the thorax to increase

4. as the volume of the thorax increases, the pressure inside it decreases

5. air enters the lungs from the atmosphere to equalise

   -there is a lower concentration of air inside the lungs compared to outside, thus air diffuses in

How does breathing in/inhaling happen?

1. external intercostal muscles relax

2. internal intercostal muscles contract, pulling the ribs down and in

3. the diaphragm relaxes upwards which causes the volume in the thorax to decrease

4. as the volume of the thorax decrease, the pressure inside it increases

5. air leaves the lungs as it is forced out by the increasing pressure to equalise

What is inspired air?

the air you breathe in from the atmosphere

What is expired air?

the fire you breathe out after it has been processed by the lungs

Fill in this table

Explain the differences in inspired and expired air for oxygen

Inspired air contains more oxygen because it comes directly from the atmosphere

Expired air contains less oxygen because

Explain the differences in inspired and expired air for carbon dioxide

Inspired air contains little co2 as atmosphere co2 levels are naturally low

Expired air contains more co2 because it is as a waste product of respiration that you body breathes out

Explain the differences in inspired and expired air for nitrogen

Both inspired and expired air have the same amount of nitrogen because it is not used or produced during respiration

Explain the differences in inspired and expired air for water vapour

Inspired air has variable water vapour levels depending on the surrounding humidity

Expired air is always saturated with water vapour because water evaporates from the moist linings of lungs

Explain the differences in inspired and expired air for temperature

Inspired air has variable temperature because it depends on surroundings

Expired air is warmer because air is heated to body temp as it passes through respiratory system

What is the effects of physical activity on the rate and depth of breathing?

Exercise causes an increase in heart rate and greater depth of breathing

Explain the effects of physical activity on the rate and depth of breathing

This is because muscles contract more frequently which requires more energy. Energy is released during respiration so more oxygen and glucose is needed. In response, the heart beats faster to deliver oxygenated blood to the muscles and remove carbon dioxide more efficently.