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.
Circulation of the Cerebrospinal Fluid. Introduction. The cerebrospinal fluid is a clear watery nutritional fluid containing sodium chloride, potassium, glucose, and various proteins. It fills the space between the arachnoid and pia mater of the central nervous system (CNS), the ventricles of the brain and the central canal of the spinal cord.