The venous system is irregular in its development and in its anatomy. Much less attention is devoted to the venous system of the various body structures, and seldom are diseases of the endocrine venous system encountered. The endocrine system is divided into two groups—the pure (ductless) group, which includes the thyroid, pituitary gland, thymus, and adrenal gland, and the dual group (both endocrine and exocrine), which includes the testes or ovaries, and pancreas. The glands may be developed from the ectoderm, mesoderm, or entoderm. Pharyngeal pouch endocrine organ derivatives include the thyroid, thymus gland, and parathyroid glands. Being developed from the cephalic part of the foregut, these buds separate and form into separate glands. The parathyroid glands develop from the third pouch. The thymus gland may also develop from caudally directed cylinder cells of the third pouch. The floor of the pharynx may develop a minute diverticulum known as the median thyroid diverticulum and become the tuberculum, which is eventually incorporated in the thyroid. All of the glands—both the arterial and the venous systems—may be intimately related to the vascular system. The endocrine glands routinely secrete chemical compounds or hormones that control the function of other cellular tissues. The glands themselves, histologically, may be well differentiated, and chemical analysis of the glands may be performed. The arterial supply as well as the venous drainage may be involved in different aspects of the endocrine system and of the specific gland. The venous drainage of these glands may be used for diagnosis more frequently than for disease-specific considerations.
VENOUS DRAINAGE OF THE PANCREAS
The pancreas is both an exocrine and an endocrine organ, and it develops as a gastrointestinal structure with insulin-secreting characteristics. A large arterial and venous system may develop about the gland. In general, the veins parallel the arteries and lie superficial to them. Both lie posterior to the ducts in the body and tail of the pancreas (Figure 28-1). They drain into the portal, splenic, superior, and inferior mesenteric veins. The veins of the head of the pancreas include four pancreaticoduodenal veins that form arcades draining the head of the pancreas and duodenum. The anterior vein joins the right gastroepiploic vein, which joins the superior mesenteric vein (SMV). The posterior vein enters the portal vein above the superior margin of the pancreas. The anterior and posterior veins separately or together form a large vein that enters the dorsal aspect of the SMV. The pancreatic tributaries do not enter the anterior surface of the portal or SMVs. Other small, unnamed veins drain independently into the SMV and the right side of the portal vein.
Veins of pancreas (posterior view).
The veins of the left portion of the pancreas form two large venous channels, the splenic vein above and the transverse (inferior) pancreatic vein ...