When does the stomach begin to develop in the embryo?

The stomach starts developing in the fourth week of intrauterine life, appearing as a fusiform dilatation of the foregut distal to the esophagus.

What are the key rotations the stomach undergoes during development?

The stomach undergoes two rotations: a 90° clockwise longitudinal axis rotation, making the left side anterior and right side posterior, and an anteroposterior axis rotation where the cardiac end moves left and down and the pyloric end moves right and up.

How does stomach rotation affect the vagus nerves?

Due to the 90° clockwise rotation, the left vagus nerve becomes anterior and the right vagus nerve becomes posterior, explaining their adult anatomical positions.

What structures form from the mesenteries of the developing stomach?

The stomach's mesenteries give rise to several ligaments: the ventral mesogastrium forms the lesser omentum and falciform ligament, while the dorsal mesogastrium forms the gastrosplenic ligament, lienorenal ligament, and greater omentum.

What is the origin of the lesser sac (omental bursa)?

The lesser sac forms behind the stomach when rotation pulls the dorsal mesogastrium to the left, creating this peritoneal space.

What are the embryonic origins of stomach tissues?

Stomach tissues derive from: the epithelium and gastric glands come from endoderm of the foregut, while the muscle and serous layers come from splanchnic intraembryonic mesoderm.

What is congenital hypertrophic pyloric stenosis and how does it present?

It is a condition caused by hypertrophy of the circular muscle at the pylorus, leading to obstruction. Infants typically present with projectile, non-bilious vomiting 2–3 hours after feeding, along with visible peristalsis and a palpable mass in the right hypochondrium.

Stomach Development – Rotation & Lesser Sac

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