When isolated, fang sheath retraction has experimentally been shown to induce very high pressures in the venom delivery system. A similar method was used to stimulate the compressor musculature, the main muscle responsible for the contraction and squeezing of the venom glad, and then measuring the induced pressures. It was determined that the pressure created from the fang sheath retraction was at times an order of magnitude greater than those created by the compressor musculature. Snakes do not have direct neurological control of the fang sheath, it can only be retracted as the fangs enter a target and the targets skin and body provide substantial resistance to retract the sheath. For these reasons, the pressure balance hypothesis concludes that external factors, mainly the bite and physical mechanics, are responsible for the quantity of venom expelled. Venom Spitting
Venom spitting is another venom delivery method that is unique to some Asiatic and African cobras. In venom spitting, a stream of venom is propelled at very high pressures outwards up to 3 meters. The venom stream is usually aimed at the eyes and face of the target as a deterrent for predators. There are non-spitting cobras that provide useful information on the unique mechanics behind venom spitting. Unlike the elongated oval shaped exit orifices of non-spitting cobras, spitting cobras have circular exit orifice at their fang tips.
Pelvic congestion syndrome, also known as pelvic vein incompetence, is a long term condition believed to be due to enlarged veins in the lower abdomen. The condition may cause chronic pain, such as a constant dull ache, which can be worsened by standing or sex. Pain in the legs or lower back may also occur.While the condition is believed to be due to blood flowing back into pelvic veins as a result of faulty valves in the veins, this hypothesis is not certain. The condition may occur or worsen during pregnancy. The presence of estrogen is believed to be involved in the mechanism. Diagnosis may be supported by ultrasound, CT scan, MRI, or laparoscopy.Early treatment options include medroxyprogesterone or nonsteroidal anti-inflammatory drugs (NSAIDs). Surgery to block the varicose veins may also be done. About 30% of women of reproductive age are affected. It is believed to be the cause of about a third of chronic pelvic pain cases. While pelvic venous insufficiency was identified in the 1850s it was only linked with pelvic pain in the 1940s. Signs and symptoms
Women with this condition experience a constant pain that may be dull and aching, but is occasionally more acute. The pain is worse at the end of the day and after long periods of standing, and those affected get relief when they lie down.