The stomach is composed of the following four parts:

Cardia (cardiac part) - the smallest portion; it surrounds the cardiac orifice and is the very first part that receives ingested food; this portion is a continuation of the abdominal esophagus (Read more!), and it contains a sphincter known as the cardiac or lower esophageal sphincter;
Fundus - the most superior part; it appears rounded and dome-shaped and is the superior dilation of the stomach; this portion is located above and left to the cardiac opening; in the upright body position, it is filled with gas; in fact, it can become dilated by gas, fluid, food, or any other combination; when this part is filled with gas, it is referred to as “gastric or stomach bubble" in imaging studies;
- Fornix of stomach - upper border of the fundus;
Body (corpus) - the largest portion; it is positioned between the fundus and the pylorus;
Pyloric part (pylorus) (Read more!) - the most distal part that links the stomach with the duodenum; it is subdivided into two smaller portions named the pyloric antrum and the pyloric canal; the pyloric antrum is wider, while the pyloric canal is narrower; the pyloric canal connects with the duodenum via the pyloric orifice that is surrounded and controlled by the pyloric sphincter.

These subdivisions of the stomach are also used when discussing X-rays of barium-filled stomachs.

Note: These anatomical parts do not correspond to the histological classification of the stomach. Histologically, the stomach is divided into only three instead of four portions. The body and fundus have the same microscopic characteristics.

Stomach sphincters

As described above, the stomach has two sphincters, and each stomach opening is guarded by one. These sphincters ensure that the food bolus and chyme move further to the following parts of the digestive system, and at the same time, they block the backflow of the contents.

The cardiac or lower esophageal sphincter is located between the stomach and the esophagus at the level of the eleventh thoracic vertebra (T11). This sphincter is a physiological sphincter. It is made of smooth muscle fibers, diaphragmatic crura, and the fibers from the phrenoesophageal ligament. This sphincter demarcates the transition from esophageal mucosa into the gastric mucosa.
The pyloric sphincter is located between the pylorus of the stomach and the duodenum. This sphincter controls the passage of the chyme into the duodenum. The pyloric sphincter is an anatomical sphincter made of the fibers of the circular muscle layer.

Note: Chyme is a thick, semi-fluid mass of partly digested food that is mainly mixed with gastric juice and expelled by the stomach into the duodenum.

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Stomach parts and sphincters