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.
The cerebrospinal fluid (CSF) is contained in the brain ventricles and the cranial and spinal subarachnoid spaces. The mean CSF volume is 150 ml, with 25 ml in the ventricles and 125 ml in subarachnoid spaces. CSF is predominantly, but not exclusively, secreted by the choroid plexuses. Brain interstitial fluid, ependyma and capillaries may also play a poorly defined role in CSF secretion.