Scanning electron microscopic study of the vascular system in the hemal node of the bovine cervical region.

The vasculature of the hemal node (HN) from the bovine cervical region was investigated using a combination of vascular corrosion casting and scanning electron microscopy. A dense vessel network of capsule was found surrounding the cast of HN parenchyma and had no connection with the subcapsular sinus; these vessels converged and exited the HN via the hilar vein. Within the HN, many anastomoses were found between the capillary networks and the surrounding sinuses in the follicular zone and deep cortex. The sinusoid pathway in the HN was characterized by subcapsular sinuses, which were continuous with the trabecular sinuses and tubular sinuses over the parenchyma, and these sinuses finally entered the medullary veins. In our study, direct communications between cortical capillaries and subcapsular sinuses were identified. This may explain the origin of numerous erythrocytes in the HN sinusoids and help to understand lymphocyte migration of the HN.