Hemorrhoids are classified into two general categories: internal and external. Internal hemorrhoids lie far enough inside the rectum that you can't see or feel them. They don't usually hurt because there are few pain-sensing nerves in the rectum. Bleeding may be the only sign that they are there. Sometimes internal hemorrhoids prolapse, or enlarge and protrude outside the anal sphincter.
Cerebrospinal fluid (CSF) collection is a test to look at the fluid that surrounds the brain and spinal cord. CSF acts as a cushion, protecting the brain and spine from injury. The fluid is normally clear. The test is also used to measure pressure in the spinal fluid. See also: CSF culture.
Cerebrospinal Fluid. Cerebrospinal fluid, also called CSF,is a clear fluid that surrounds the spinal cord and brain. The flow of CSF is essential to the cushioning, protection and support of the brain. It is also essential for the removal of waste products from the brain.SF is produced in the chambers of the brain called ventricles. The two highest ventricles in the brain are the lateral ventricles. The third ventricle lies below them and the fourth ventricle lies below the third. A dense plexus of blood vessels, called the telea choroidea, lies close to the ventricles.