Slides of Regeneration

Slides and Text Courtesy of Dr. Steven Scadding, <>

48 Hours Post-Amputation: The epidermis (E) has grown across the wound surface, although the humerus (H) is still protruding due to the retraction of soft tissues following the amputation. Some dedifferentiation (D) is beginning distal to the amputation, although most of the stump's muscle (M)is still seen as differentiated tissue.
7 Days Post-Amputation: The amputation wound is completely healed (covered by epidermis (E)). The muscle is now undergoing dedifferentiation (D) for some distance proximal to the amputation level (arrow). Osteoclasts are beginning to break down the distal portion of the humerus (H).
14 Days Post-Amputation: A thickened apical cap of epidermis (E) has formed. A blastema (B) has formed over the cut end of the humerus (H) at the amputation site (arrow). Note the extensive area of dedifferentiated muscle cells (D).
18 Days Post-Amputation: The blastema (B) is now quite prominent, and cell proliferation is ongoing in this area. Note the close contact between the epidermis (E) and the underlying blastema. A large nerve (N) is seen to divide as it reaches the blastema.
24 Days Post-Amputation: The blastema is now as long as it is wide, forming a cone shaped structure. It continues to elongate rapidly.
24 Days Post-Amputation #2: As the cone elongates, cartilage (C) begins to differentiate within the blastema around the ends of the transected bones at the level of amputation (arrow).
35 Days Post-Amputation: The entire skeletal pattern consisting of the humerus (H), radius (R), ulna (U), carpels (Ca) and phalanges (P) has been laid down. NOTE: This picture is actually from a different species which shows faster regeneration than the one in the other pictures. As a result, this amputation took place only 24 days ago, but is equivalent to 35 days post-amputation in the particular species seen in the other pictures!
42 Days Post-Amputation: The limb pattern has been completely restored following the amputation. The humerus (H), radius (R), ulna (U), carpels (C) and phalanges (P) have all redifferentiated and been restored (main picture and inset). This limb requires only further growth to make it almost identical to the amputated limb. The arrow indicates the level of amputation (see inset).


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