Henry Gray (18251861). Anatomy of the Human Body. 1918.
of the right subcardinal vein, the postrenal part of the right cardinal vein, and the cross branch which joins these two veins. The left subcardinal disappears, except the part immediately in front of the renal vein, which is retained as the left suprarenal vein. The spermatic (or ovarian) vein opens into the postrenal part of the corresponding cardinal vein. This portion of the right cardinal, as already explained, forms the lower part of the inferior vena cava, so that the right spermatic opens directly into that vessel. The postrenal segment of the left cardinal disappears, with the exception of the portion between the spermatic and renal vein, which is retained as the terminal part of the left spermatic vein.
In consequence of the atrophy of the Wolffian bodies the cardinal veins diminish in size; the primitive jugular veins, on the other hand, become enlarged, owing to the rapid development of the head and brain. They are further augmented by receiving the veins (subclavian) from the upper extremities, and so come to form the chief veins of the Cuvierian ducts; these ducts gradually assume an almost vertical position in consequence of the descent of the heart into the thorax. The right and left Cuvierian ducts are originally of the same diameter, and are frequently termed the right and left superior venæ cavæ. By the development of a transverse branch, the left innominate vein between the two primitive jugular veins, the blood is carried across from the left to the right primitive jugular (Figs. 479,480). The portion of the right primitive jugular vein between the left innominate and the azygos vein forms the upper part of the superior vena cava of the adult; the lower part of this vessel, i.e., below the entrance of the azygos vein, is formed by the right Cuvierian duct. Below the origin of the transverse branch the left primitive jugular vein and left Cuvierian duct atrophy, the former constituting the upper part of the highest left intercostal vein, while the latter is represented by the ligament of the left vena cava, vestigial fold of Marshall, and the oblique vein of the left atrium, oblique vein of Marshall(Fig. 480). Both right and left superior venæ cavæ are present in some animals, and are occasionally found in the adult human being. The oblique vein of the left atrium passes downward across the back of the left atrium to open into the coronary sinus, which, as already indicated, represents the persistent left horn of the sinus venosus.
Venous Sinuses of the Dura Mater.1The primary arrangement for drainage of the capillaries of the head (Figs. 481,488) consists of a primary head vein which starts in the region of the midbrain and runs caudalward along the side of the brain tube to terminate at the duct of Cuvier. The primary head vein drains three plexuses of capillaries: the anterior dural plexus, the middle dural plexus and the posterior dural plexus. The growth of the cartilaginous capsule of the ear and the growth and alteration in form of the brain bring about changes in this primary arrangement (Figs. 483488). Owing to the growth of the otic capsule and middle ear the course of the primary head vein becomes unfavorable and a segment of it becomes obliterated. To make the necessary adjustment an anastomosis is established above the otic capsule (Fig. 483) and the middle plexus drains into the posterior plexus. Then the anteror plexus fuses with the middle plexus (Fig. 484) and drains through it and the newly established channel, dorsal to the otic capsule. All that remains of the primary head vein is the cardinal portion or internal jugular and the part in the region of the trigeminal nerve which may be called the cavernous sinus. Into it drain the orbital veins. The drainage from the cavernous sinus is now upward through the original trunk of the middle plexus, which is now the superior petrosal sinus, into the newly established dorsal channel. This dorsal channel is the transverse sinus (Figs. 485488). The inferior petrosal sinus appears later (Fig. 486). From the anterior plexus a sagittal plexus extends forward from which develops the superior sagittal sinus (Figs. 484488). The straight sinus is
Note 1. Streeter, Am. Jour. Anat., 1915, vol. xviii. [back]