Anatomy of GIT
The GI tract or gastrointestinal tract is an organ
system consisting of a hollow-muscular tube starting
from the oral cavity, where food enters
the mouth, continuing through the pharynx,
oesophagus, stomach, and intestines to the rectum and anus, where food is
expelled. Usually, the GI involves both the stomach and intestines and is
classified into the upper and lower gastrointestinal tract.
The primary purpose of the
gastrointestinal tract is to break food down into nutrients, which can be absorbed into the body to provide
energy. First food must be ingested into the mouth to be
mechanically processed and moistened. Secondly, digestion occurs mainly in the
stomach and small intestine where proteins, fats, and carbohydrates are
chemically broken down into their basic building blocks. Smaller molecules are
then absorbed across the epithelium of the small intestine and subsequently enter the circulation. The large intestine plays a key role in reabsorbing
excess water. Finally, undigested material and secreted waste products are
excreted from the body via defecation (passing of faeces). In the case of
gastrointestinal disease or disorders, these functions of the gastrointestinal
tract are not achieved successfully. Patients may develop symptoms of nausea,
vomiting, diarrhoea, malabsorption, constipation, or obstruction.
Gastrointestinal problems are very common and most people will have experienced
some of the above symptoms several times throughout their lives.
Upper gastrointestinal tract
The upper gastrointestinal tract consists of the mouth, pharynx, oesophagus, 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 on function, location, and internal anatomy. The four segments of the duodenum are as follows (starting at the stomach, and moving toward the jejunum): blub, descending, horizontal, and ascending. The suspensory muscle attaches the superior border of the ascending duodenum to the diaphragm.
Lower gastrointestinal tract
The lower gastrointestinal tract includes most of the small intestine and all of the large intestine. In human anatomy, the intestine 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.
