Abstract :
The aim of this study was to describe microcirculation in the human digit, focusing on the vascular patterns of its
cutaneous and subcutaneous areas. We injected a functional supranumerary human thumb (Wassel type IV) with
a low-viscosity acrylic resin through its digital artery. The tissues around the vessels were then digested in hot alkali
and the resulting casts treated for scanning electron microscopy. We concentrated on six different areas: the palmar
and dorsal side of the skin, the eponychium, the perionychium, the nail bed and the nail root. On the palmar
side, many vascular villi were evident: these capillaries followed the arrangement of the fingerprint lines, whereas
on the dorsal side they were scattered irregularly inside the dermal papillae. In the hypodermal layer of the palmar
area, vascular supports of sweat glands and many arteriovenous anastomoses were visible, along with glomerularshaped
vessels involved in thermic regulation and tactile function. In the eponychium and perionychium, the
vascular villi followed the direction of nail growth. In the face of the eponychium in contact with the nail, a
wide-mesh net of capillaries was evident. In the nail bed, the vessels were arranged in many longitudinal trabeculae
parallel to the major axis of the digit. In the root of the nail, we found many columnar vessels characterized by
multiple angiogenic buttons on their surface.
