<P> The upper gastrointestinal tract consists of the mouth, pharynx, esophagus, stomach, and duodenum . The exact demarcation between the upper and lower tracts is the suspensory muscle of the duodenum . This differentiates the embryonic borders between the foregut and midgut, and is also the division commonly used by clinicians to describe gastrointestinal bleeding as being of either "upper" or "lower" origin . Upon dissection, the duodenum may appear to be a unified organ, but it is divided into four segments based upon function, location, and internal anatomy . The four segments of the duodenum are as follows (starting at the stomach, and moving toward the jejunum): bulb, descending, horizontal, and ascending . The suspensory muscle attaches the superior border of the ascending duodenum to the diaphragm . </P> <P> The suspensory muscle is an important anatomical landmark which shows the formal division between the duodenum and the jejunum, the first and second parts of the small intestine, respectively . This is a thin muscle which is derived from the embryonic mesoderm . </P> <P> The lower gastrointestinal tract includes most of the small intestine and all of the large intestine . In human anatomy, the intestine (bowel, or gut . Greek: éntera) is the segment of the gastrointestinal tract extending from the pyloric sphincter of the stomach to the anus and, as in other mammals, consists of two segments, the small intestine and the large intestine . In humans, the small intestine is further subdivided into the duodenum, jejunum and ileum while the large intestine is subdivided into the, cecum, ascending, transverse, descending and sigmoid colon, rectum, and anal canal . </P> <P> The small intestine begins at the duodenum and is a tubular structure, usually between 6 and 7 m long . Its mucosal area in an adult human is about 30 m . Its main function is to absorb the products of digestion (including carbohydrates, proteins, lipids, and vitamins) into the bloodstream . There are three major divisions: </P>

Is the small intestine part of the upper gi tract