The thoracic inlet is an opening at the top of the ribcage formed by the bony ring of the first ribs, the first thoracic vertebra, and the manubrium (top of the breastbone). It is where the neck meets the torso. Many vital anatomical structures – arteries, nerves, veins, lymph vessels, plus the trachea and esophagus – pass through this aperture.
If we are looking for a structure in the body that parallels the pelvic floor and the thoracic diaphragm, let’s consider the Sibson’s fascia. The Sibson’s fascia is a thickening of the pleural fascia at the apex of the lungs and extends the endothoracic fascia, which lines the thoracic ribcage. It is anchored to the internal border of the first ribs and the transverse processes of the C7 vertebra. And because the lungs extend somewhat above the thoracic inlet, so does the Sibson’s fascia. Check out this cool drawing.
Many of us tend to collapse our thoracic cage during activities of daily living. Yoga practice is one of the places where we practice our postural alignment. Come to sitting in a chair with your sitting bones near the front of the seat and your feet flat on the ground. Allow your spine to collapse into an old postural habit. Then turn your attention to your sitting bones and feel them push down into the chair as you lift your manubrium and 1st rib upwards. Only go as far as you can feel equal length in the front and back of your body. Once you feel compression in your kidneys, you’ve gone too far. This should bring your thoracic cage into its fullest volume and the thoracic inlet into its widest opening, creating a fuller breath and an increased sense of vitality.
Now try this in tadasana, mountain pose. Can you feel the lift of the 1st rib from the rooting of the feet? Begin to catch yourself slouching throughout your day and instead of hoisting yourself into ‘good posture,’ see if you can find a healthy lift of the 1st rib from the grounding of your feet or seat. In a later post, we will add to this a stacking of the diaphragms.
Once you become accustomed to the sensation of lift and fullness in the rib cage, begin to find it in other poses. Also notice that some poses in the forward bend family actively cultivate a condensing through the front of the rib cage, a drawing down of the first rib and manubrium, and a narrowing of the thoracic inlet. While some poses in the backbending family do the opposite. Continue to play and notice. Report back to us what you find!