Gas Exchange- Humans

  • Created by: Haeinh
  • Created on: 28-07-16 20:01


2.44 a- Describe the structure of the thorax

The Lungs are the Respiratory Organ of a man

The Thorax is the Top Part of your body

                       -------> Seperated from the Lower Part of your body by the Diaphragm.


RIBS- Bones that embrace/protect the lungs

INTERCOSTAL MUSCLES- Muscles located in-between the ribs. Keeps the ribs in place + moves them when inhaling/exhaling 

DIAPHRAGM- A sheet of skeletal muscle ----> goes right across the body. Seperates lungs + heart from abdomen. Allows lungs to inhale/exhale (ex: diaphragm pushes up into lungs to help exhale + vice versa inhaling)

TRACHEA- Your Windpipe. Air first passes through here when inhaling. Has rings of cartilage to keep it open + support.

BRONCHI- Two tubes from the trachea ------> seperate into each lung (singular tube- bronchus)

BRONCHIOLES- Smaller tubes progressively split from the bronchi. Contains alveoli at tips.

ALVEOLI- Mircroscopic airsacs. Where gas exchange of carbon dioxide and oxygen occurs in lungs. 

PLEURAL MEMBRANE-  Thin + moist membranes that are the outer lining of each lung. Envelopes lungs, forming airtight seal.

PLEURAL CAVITY-  Spaces between the two pleural membranes. Filled with pleural liquid.  Spongy + Slippery (pleural liquid) to reduce friction when rubbing against the ribs. and so lungs do not stick to chest wall whilst breathing. (NOT ON SYLLABUS).

2.44 b- Process of the Air

Air goes in from mouth/nose ------> down trachea -----> splits through bronchi into left/right lung ------> seperates further into many bronchioles ------> once at end reaches aveoli.

2.45- Understand the role of the intercostal muscles and the diaphragm in ventilation


  • Movement of air in/out AKA inhaling/exhaling
  • This process requires a difference in air pressure (explanation further down)
  • Throax is an airtight cavity ----> when inhale- thorax volume changes = pressure changes


I-  Intercostal muscles





Breathing In

1. Intercostal muscles contract

Once Muscles Contract-

2. Diaphragm becomes flatter and moves down

3. Ribs cage pulled upward and outward

4. Thorax Volume increases

5. So Pressure Decreases...

6. ...Drawing air in

Breathing Out

1. Intercostal muscles relax

Once Muscles Contract-

2. Diaphragm relaxes becomes dome-shaped 

3. Ribcage and Sternum move down and in

4. Thorax Volume decreases

5. Pressure Decreases

6. As air forced to rush out and so lungs deflate



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