THE VESSELS OF THE TAIL
The median artery and vein of the tail require brief notice. The artery, which continues the median sacral, is ventral to the vein for most of the length of the tail and is commonly used for pulse taking; the usual site is about 18 cm from the root of the tail.
The vessels lie side by side in the proximal part of the tail (Cd2 or Cd3), where both artery and vein are available for
Figure 26-5 Dorsal view of the venous drainage in the bovine vertebral canal. The internal vertebral plexus, with its internal connections and its lateral segmental branches, has been exposed. 1, Internal vertebral plexus; 2, intervertebral veins; 3, intervertebral disk; 4, vertebral body.
Figure 26-6 The connections of the major veins with the vertebral plexus-azygous system. Note specifically the connections between the internal vertebral plexus (15) and the intercostal veins (10) and between the plexus and the branches of the vertebral vein (6). 1, Internal jugular v.; 2, external jugular v.; 3, occipital v.; 4, axillary v.; 5, cranial vena cava; 6, vertebral v.; 7, supreme intercostal v.; 8, left azygous v.; 9, caudal vena cava; 10, intercostal vv.; 11, internal iliac v.; 12, external iliac v.; 13, deep circumflex iliac v.; 14, cranial epigastric v.; 15, internal vertebral plexus (red).
Figure 26-7 A, Transverse section of the bovine tail between Cd3 and Cd4. 1, Intervertebral disk; 2, median caudal vein; 3, median caudal artery; 4, hemal process. B, Collection of blood from a median caudal vessel.
obtaining blood, although this site is an unwise choice because of the inevitable fecal contamination (Figure 26-7, B). At this level both vessels lie against the ventral aspect of the caudal vertebrae, where they are protected by the hemal processes (Figure 26-7, A) arches on the first few vertebrae (see Figure 2-12, E/9). The vessels are thus accessible only at intervertebral levels. It is usual to dock the tail of lambs.