the digestive tract
by julee snyder
Referred to as the soft spine, the digestive tract is the hollow tube that runs from mouth to anus. It includes the mouth, esophagus, stomach, small intestines, large intestines, and rectum. It is approximately 30ft, or 10 yards, in length. The digestive tract is a hollow tube lined with smooth muscle. The superficial muscular fibers run longitudinally and send waves down the length of the tube. The deeper muscular fibers gently hug and churn the chyme. Collectively, they squeeze the contents and move them along.
The esophagus runs along the front of the spine behind the trachea and behind the heart. It veers slightly left where it pierces the diaphragm at the level of T10. This is called the cardiac sphincter. It then becomes the stomach.
The stomach has three muscular layers wrapping in different planes designed to mechanically churn the contents. It sits under the dome of the diaphragm on the left side. Its fundus goes as high as the 5th/6th intercostal space. Its medial border is called the lesser curvature and is lined with the vagus nerve. It follows the line of the left sternal border. The lateral border of the stomach is the greater curvature and can be found at the left lateral border of the rectus abdominus. Size and shape of stomachs vary widely.
The pyloric shelf rests between the naval and the xyphoid process. This is where the stomach becomes the duodenum of the small intestines. The pancreas and gall bladder both empty their juices into the small intestines here at the first leg of the duodenum. The duodenum wraps like a circle (with four legs) around the head of the pancreas slightly above the naval. It then empties into the jenjunoileum.
The jejunoileum is the site of absorption. It has many loops that are held by the mesentery. The mesentery is a connective tissue sling with contractile properties that hold the small intestines into the back wall of the peritoneum. It ends near the appendix in the lower right abdomen at the iliocecal valve.
The large intestines begin with a large sac in the right belly called the cecum. It moves the contents upward through the ascending colon. Contents then travel across the abdomen via the transverse colon and down the descending colon on the left. From there it enters the sigmoid colon, which travels to the rectum, and is released through the anus.
The Ascending Colon on the right supports the right leg; The Descending Colon on the left supports the left leg. This is especially sensed in the suspensory role in poses like three-legged dog.
the five spines
In BMC, we sometimes refer to the five spines. We have the hard spine of the vertebral column and its discs; the nervous system spine of the central nervous system; the soft spine of the organs; the glandular spine; and the embryological spine of the notochord. Each offers support to the others and gives a different quality of expression.
Spend time with each organ of the digestive tract. Understand its structure, its sense of tone, its mobility. Feel the connections of the spine and limbs as you move into asana. In yoga we talk about stoking the digestive fire through practice of vinyasa or the more fiery breaths. But what if we were gentle with the digestive tract? What if we nuzzled it softly to the spine for support.
It has an intimate relationship with the vagus nerve and the enteric nervous system–both very responsive to our sense of safety in the world. The gut tube also has the same receptors for emotional balance as the brain–receptors for seratonin, dopamine, etc. Science is learning more and more about how our gut health is related to our emotional health and vice versa.
*credit here is owed to Jean-Pierre Barral and Bonnie Bainbridge Cohen. Some of this material comes directly from their manuals.