To begin our series on breathing, let’s have a look at what actually goes on inside of you 22,000 times a day.
Your torso comprises two cavities, the thoracic cavity (upper) and the abdominal cavity (lower). The thoracic cavity contains the heart and lungs, and the abdominal cavity houses the stomach, gall bladder, pancreas and small intenstines (which all help to control digestion), the large intestine (managing elimination) kidneys (the bodies filter) and bladder, the liver (which breaks down toxins and stores nutrients) and our reproductive organs.
Separating these two cavities is the diaphragm. Each time the diaphragm moves, all your internal organs are massaged, squeezed and saturated with fluids and oxygen. Any restriction of the diaphragm (whether it be conscious or unconscious) not only impacts our breath quality, but also the vitality and optimal functioning of all of our internal organs.
The diaphragm is a dome shaped muscle that looks somewhat like a jellyfish or an opened parachute. At the top of the dome is a tendon above which sits the heart. The fibres of the diaphragm muscle radiate outwards from this central tendon like panels on an opened umbrella. The edges attach to the ribs and lower spine, fanning it out to literally form a roof-like structure to the abdominal cavity. Its rhythmic contraction and expansion occurs 24 hours a day and it is responsible for 75 % of all of our respiratory effort.
When the diaphragm is stimulated by the phrenic nerve it drops downwards from its domed shape, causing an enlargement of the lung capactiy and volume. This causes a pressure imbalance; pressure outside the body is then greater than the pressure inside the lungs, so air is drawn into the body in a vacuum like effect. This is the action we experience as an inhalation. As the air is drawn into the lungs it comes into contact with a hundred million alveoli, located at the base of the lungs which allows the oxygen to dissolve and pass into the bloodstream, and the carbon dioxide to be eliminated.
When the diaphragm has finished contracting it relaxes upwards in the torso, compressing the air inside the lungs, forcing it to be expelled through the nostrils. The lungs are elastic by design and they don’t collapse inwards even after most of the air has been emptied. This is due to the space surrounding the outer part of the lungs and the chest wall – the pleural cavity, which contains no air, only a vacuum which holds the lungs tightly against the inner surface of the chest wall.
Apart from the diaphragm, there are other muscles used in breathing. The intercostal muscles are short muscles found woven between the ribs which work to expand contract the chest, and draw the ribs closer together. The abdominal muscles are generally used in forced and deep exhalations when the abdominal wall is pressed inwards, and the organs are forced up agains the diaphragm which decreases the size of the chest cavity and pushes air out of the lungs. The secondary breathing muscles include any other muscles which assist in changing the shape of the torso as we breathe. They are generally smaller and tend to tire more easily. But they do give us more adaptability in the manner in which we breathe. These muscles include the pectoralis (in the front of the chest) and the trapezius (across the upper back) to name just a few, and are generally located higher up in the body.
This is a very simple (I know that may be a matter of opinion – but our bodies are complex things!) explanation of the breath from an anatomical point of view. If this is a topic that interests you and you want to deepen your understanding of it, I recommend finding the following books.
- Yoga Anatomy by Leslie Kaminoff has an excellent introductory chapter on the anatomy of breathing. This book is being re-released and expanded in the Fall so if you don't own this already, I would wait until the second edition has been released. This book contains great diagrams to help aid your understanding if you are a visual learner. You can find this on the 889 bookshelf in the tea garden.
- The Breathing Book by Donna Farhi is one of my all time favourite yoga books, one that I refer to very regularly. Very simple for complete beginners to the subject, but still very informative for teachers too. Again, this one is in the library in the tea garden for you to read before or after class.
- Anatomy of Hatha Yoga by David Coulter is an academic and dense hard covered text and is a great reference for teachers, but not recommended for beginner students. Chapter Two on breathing is highly informative but intense reading.