Venous plexus

An important difference between epidural anesthesia and spinal anesthesia is that agents injected into the epidural space may readily enter the blood due to the presence of a rich venous plexus... 

The mode of action is thought to be related to cholinesterase inhibition. This inhibition temporarily paralyzes the adult worms, resulting in their shift from the bladder venous plexus to small arterioles of the lungs, where they are trapped, encased by the immune system, and die. The drug is not effective against S haematobium eggs live eggs continue to pass in the urine for several months after all adult worms have been killed. 

GnRH is produced in the arcuate nucleus of the hypothalamus. GnRH is secreted into the hypothalamic-pituitary venous plexus and binds to cell surface receptors of the anterior pituitary gonadotroph cells. Pulsatile GnRH secretion is required to stimulate the gonadotroph cell to produce and release luteinizing hormone (LH) and follicle stimulating hormone (FSH). 

Blood from the haemorrhoidal venous plexus passes via the azygous superior rectal vein into the inferior mesenteric vein and thereafter into the portal vein. By contrast, the paired middle rectal vein and inferior rectal vein discharge their blood via the iliac vein into the inferior vena cava. In portal hypertension, anorectal varices are found in the region of the rectum, the anal canal and the external anal region. Haemorrhoids are distended and dislocated cavernous bodies in the rectum, which have no connection to the portal venous system. Although haemorrhoids and anorectal varices are two different clinical pictures, it is quite possible for them to occur simultaneously. The frequency of anorectal varices (40-80%) is dependent upon the extent and duration of portal hypertension. The bleeding tendency is low (7-14%). However, there have also been reports of massive haemorrhages. (21,45,55,66,83,105,156) (s. tab. 14.10)... 

Approximately 85% of the CSF is produced within the third, fourth, and lateral ventricles by the choroid plexus (see Fig. 105-1). CSF volmne in the CNS is related to patient age Infants have approximately 40 to 60 mL of CSF, older children have 60 to 100 mL, and adults have 110 to 160 mL. Normally, CSF is produced at the rate of approximately 500 mL/day and flows unidirectionaUy downward through the spinal cord. The CSF is removed by the arachnoid villi and vertebral venous plexus located in the spinal cord and does not recommimicate with the point of production. ... 

Dameron, G. W., K. W. Weingand, J. M. Duderstadt, L. W. Odioso, T. A. Dierckman, W. Schwecke, and K. Baran. 1992. Effects of bleeding site on clinical laboratory testing of rats Orbital venous plexus versus posterior vena cava. Laboratory Animal Science 42 299-301. 

Matsuzawa, T., H. Tabata, M. Sakazume, S. Yoshida, and S. Nakamura. 1994. A comparison of the effect of bleeding site on hematological and plasma chemistry values of F344 rats The inferior vena cava, abdominal aorta, and orbital venous plexus. Comparative Haematology International 4 207-211. 

Another theory describes the ulceration of a submucosal fibroid into the endometrial surface [91]. The fibroids may compress the venous plexus within the myometrium which may lead to uterine engorgement and greater bleeding [91]. The latest... 

CT and MRI. On CT and MRI pelvic varices are seen as dilated tortuous paraovarian or parauterine tubular structures, frequently extending to the broad ligament and pelvic sidewall or paravaginal venous plexus [26,27] (Fig. 11.4a,b). 

Foramen magnum Clival venous plexus, spinal perimedullary veins... 

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