Ventral and dorsal buds from the distal foregut contribute to the formation of the pancreas (Fig. 2-46). The uncinate process and inferior portion of the pancreatic head are derived from the slightly more caudal ventral bud, which is originally bifid in shape.84-87 The body, tail, and superior portion of the head develop from the dorsal bud, which grows into the mesenchyme of the

Fig. 2-43. Patent ductus venosus in a 3-year-old female with cardiac failure.

(a) Enhanced CT shows a moderately dilated left portal vein (arrow) and a large vessel (curved arrow) connecting the left portal vein and IVC.

(b) Angiography with a catheter placed at the left portal vein inserted via the IVC confirms the patent ductus venosus (curved arrows) ending at the confluence of the left hepatic vein (LH) and IVC. RA = right atrium.

mesoduodenum (dorsal mesentery of the duodenum). The pancreatic buds follow the duodenum in the latter's 90° rotation. The anteriorly located ventral bud undergoes an additional 180° rotation that brings it rightward, posteriorly, and finally leftward to lie in the concavity of the duodenal "C-loop." The fusion of the two pri-mordia occurs at the end of the sixth week, and their ducts anastomose. The dorsal pancreatic bud has a greater propensity for fatty infiltration than the ventral bud, which allows distinction between the pancreatic embryological anlagen on imaging studies in some in dividuals (Fig. 2-47). As the mesoduodenum is resorbed, the pancreas assumes its retroperitoneal location, with the exception of a small portion of the tail that lies near the hilum of the spleen that thus remains intraperitoneal in position.84 Variations in the lateral contour of the normal head of the pancreas are common. CT scans of more than 30% ofpatients without pancreatic diseases have shown discrete lobulations of the pancreas greater than 1 cm lateral to the gastroduodenal or anterior superior pancreaticoduodenal artery.88 These lobulations may mimic pancreatic masses on CT (Fig. 2-48).

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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