Internal hemorrhoids
arise from the superior hemorrhoidal veins situated above
the anorectal/pectinate line, covered by rectal mucosa.
External hemorrhoids are dilations of the inferior
hemorrhoidal veins situated externally to the anorectal
pectinate line and covered by skin hemorrhoid
symptoms are seldom attributable to external
hemorrhoids alone. Mixed hemorrhoids
are a combination of internal and external
hemorrhoids caused by the downward
reflection of internal hemorrhoid pressure
via a communicating vasculature to the
external hemorrhoid complex. Because the
superior hemorrhoidal veins are devoid of
valves, this vasculature is sensitive to
changes in venous pressure.
Repeated straining, diarrhea, constipation and
other factors result in vascular dilation and
eventually bleeding, soilage, pain. pruritis and
protrusion down the anal canal.