Final answer:
Internal hemorrhoids drain via the internal iliac veins, while external hemorrhoids drain through the external iliac vein. Both sets of iliac veins join to form the common iliac vein, which leads into the inferior vena cava.
Step-by-step explanation:
Internal hemorrhoids drain through the internal iliac veins, which are part of a network of veins in the pelvic region, including the umbilical veins near the bladder. These veins coalesce into the common iliac vein. External hemorrhoids, on the other hand, drain through the external iliac vein. This vein drains blood from the leg area and joins the common iliac vein as well. The common iliac veins merge at the level of the fifth lumbar vertebra (L5) to form the inferior vena cava, which then carries deoxygenated blood back to the heart.
Internal hemorrhoids drain into the internal iliac vein, which forms from smaller veins in the pelvic region. These veins are responsible for draining blood from the pelvic organs and integument, including the bladder.
External hemorrhoids, on the other hand, drain into the external iliac vein. This vein begins as the femoral vein in the upper limb and carries blood from the leg.