1. The Respiratory System To explore lung structure and the mechanics of breathing.

2.  The apex of each lung is its rounded tip. The apex rises just above the clavicle.  The base is the bottom portion of each lung; the base is concave and is superior to the diaphragm.  The curved region, below the ribs, is the costal surface.  The medial surface is concave and is where the hilum is located.  The space between the lungs is referred to as the mediastinum and is occupied by the heart and structures entering the lungs.

3. Pleura  The pleural membrane is a double membrane that covers each lung. The pleural membrane ensures the lungs remain airtight and allows friction free movement when breathing.  The pleura of the right lung and pleura of the left lung are separate, this is important so that damage to one does not affect the other.

4.  The parietal pleura is attached to the wall of the thorax.  The visceral pleura covers the surface of the lung.  Between the 2 membranes is a potential space called the pleural cavity.  The pleural cavity contains pleural fluid; this is made by the membranes and ensures that the membranes glide against each other during breathing.  The two layers of pleura normally remain tightly adhered to one another.

5. Ventilation  Q – What is ventilation?  For breathing to occur, the volume of the thorax has to keep changing.  First, the volume is made larger so that air gets drawn in – this is inhalation.  The volume is then made smaller so that air is expelled – this is exhalation.  The volume of the thorax is made larger and smaller by muscles – the intercostal muscles located between the ribs and the diaphragm – the sheet of muscle that separates the thorax from the abdomen.

7.  According to Marieb (2006, p 434), Volume changes lead to pressure changes, which lead to the flow of gases to equalise the pressure.  When the volume (space inside) of the thorax is increased, the air pressure inside it drops. As a result air is sucked into the body from the atmosphere to equalise the pressure in the lungs with that of the outside environment (atmospheric pressure).

8.  When the volume of the thorax is decreased, the air pressure inside it rises. As a result air is forced out of the body to equalise the pressure within the lungs with that of the outside environment (atmospheric pressure).

9. Intercostal Muscles  The intercostal muscles are paired muscles located between the ribs.  The inner muscles are referred to as the internal intercostal muscles.  The outer muscles are referred to as the external intercostal muscles.  NB – there is a layer of innermost intercostal muscles situated below the internal intercostal muscles.

10. Breathing In/Inspiration  The external intercostal muscles contract (the internal intercostal muscles relax).  This elevates the ribcage, moving it upwards and outwards.  The dome-shaped diaphragm contracts and flattens.  Both actions serve to increase the volume of the thorax.

11.  Air pressure in the lungs drops and air rushes in from the atmosphere to equalise the pressure.  Inspiration is an energy requiring activity because it involves muscle contraction.

12. Breathing Out/Exhalation  This is normally a passive process.  During quiet breathing, the external intercostal muscles relax and the ribcage returns to its normal position (thus decreasing in size; the internal intercostal muscles also relax).  The diaphragm relaxes and returns to its dome-shaped position.  The volume of the thorax is decreased; air pressure in the lungs increases and air is forced out of the body.

13. Forced Exhalation – Requires Energy  The internal intercostal muscles contract during forced exhalation.  This could be when breathing out more deeply during exercise, when singing, playing a musical instrument or even during illness.  The function of the innermost intercostal muscles is to fix the position of the ribs during breathing.

14. ??

16. Animations  http://www.johnwiley.net.au/highered/interactions/media/ Respiration/content/Respiration/resp1a/frameset.htm http://www.johnwiley.net.au/highered/interactions/media/ Respiration/content/Respiration/resp1a/frameset.htm  http://www.nhlbi.nih.gov/health/health- topics/topics/hlw/whathappens.html http://www.nhlbi.nih.gov/health/health- topics/topics/hlw/whathappens.html

17. Quiz  http://www.biologycorner.com/quiz/qz_respiratory.html http://www.biologycorner.com/quiz/qz_respiratory.html Marieb EN (2006) ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY, 8 th ed., San Francisco, Benjamin Cummings