The document discusses the blood supply of the skin, which originates from deep vessels that feed into perforator vessels and plexuses in 6 layers under the skin. The skin surface is divided into angiosomes, or blocks supplied by named arteries, which are connected by true or choke anastomoses. The delay phenomenon enhances skin flap survival by promoting axial blood flow and dilating choke vessels between angiosomes. The angiosome concept defines safe flap boundaries and connections between arterial territories.

2. Blood Supply of the Skin

3. Anatomy of Circulation
• The blood reaching the skin originates from deep vessels
• These then feed interconnecting perforator vessels which
supply the vascular plexus
• Thus skin fundamentally perfused by musculocutaneous or
septocutaneous perforators

4. Nahai-Mathes Classification

5. Anatomy of Circulation
• The vascular plexuses of the fascia, subcutaneous tissue and
skin are divided into 6 layers

7. Anatomy of Circulation
1)Subfascial plexus
small plexus lying on the
undersurface of the fascia

8. Anatomy of Circulation
2) Prefascial plexus
-a larger plexus
-particularly prominent on
the limbs
-fasciocutaneous vessels

9. Anatomy of Circulation
3)Subcutaneous Plexus
-lies at the level of
superficial fascia
-Predominant on the torso
-musculocutaneous vessels

10. Anatomy of Circulation
4)Subdermal Plexus
-receives blood from
underlying plexus
-the main plexus supplying
blood to the skin
-represents the dermal
bleed observed in incised
skin

11. Anatomy of Circulation
5) Dermal Plexus
-mainly arterioles
-important in
thermoregulation

12. Anatomy of Circulation
6)Subepidermal Plexus
-contains small vessels
without muscle in the walls
-nutritive and
thermoregulatory function

13. Angiosomes
• Similar to a skin dermatome is a composite block of 3
dimensional tissue supplied by a named artery
• Entire skin surface of the body is therefore perfused by a
multitude of angiosome units
• First studied by Marchot 1889, expanded by Salmon 1930 and
more recently by Ian Taylor

14. Angiosomes
• Each angiosome is linked to its neighbour at every tissue
level, either by
– a true (simple) anastomotic arterial connection without
change in caliber of the vessel
– or by a reduced-caliber choke anastomosis.

15. Taylor GI, Palmer JH. The vascular territories (angiosomes) of the body:
experimental study and clinical applications. Br J Plast Surg. 1987;40:113.
• The sites of emergence of
the direct and indirect
cutaneous arterial
perforators of 0.5 mm or
greater averaged from all
studies.
• Direct perforators are more
common in the limbs,
whereas indirect
perforators predominate in
the torso

17. Choke vessels. A: Schematic of choke anastomoses (A) and true anastomoses
(B) between adjacent arteries. (Taylor GI, Minabe T. The angiosomes of the
mammals and other vertebrates. Plast Reconstr Surg. 1992;89:181.

18. Choke Vessels
• Choke vessels play an important role in skin-flap survival, they
provide an initial resistance to blood flow between the base
and the tip of the flap.
• When a skin flap is delayed by the strategic division of
cutaneous perforators along its length, these choke vessels
dilate to the dimensions of true anastomoses thus enhancing
the circulation to the distal flap

19. Delay Phenomenon
• Is a preliminary surgical intervention wherein a portion of the
vascular supply to a flap is divided before definitive elevation
and transfer of the flap
• Mechanism of this phenomenon is controversial

20. Delay Phenomenon
• Increased axiality of blood flow
– Removal of blood flow from periphery of a random flap
promotes development of axial flow
• Tolerance to ischaemia
– Cells become accustomed to hypoxia
• Sympathectomy vasodilation theory
– Thus leading to vasodilation
• Dilation of choke vessels
• Hyperadrenergic theory

21. The angiosome concept has important clinical implications
1) Each angiosome defines the safe anatomic
boundary of tissue in each layer that can be
transferred separately or combined on the
underlying source vessels as a composite flap.
2) Because the junctional zone between adjacent
angiosomes usually occurs within muscles of the
deep tissue, rather than between them, these
muscles provide an important anastomotic detour
(bypass shunt) if the main source artery or vein is
obstructed.

22. The angiosome concept has important clinical implications
3) Because most muscles span two or more angiosomes and are
supplied from each territory, one is able to capture the skin
island from one angiosome by muscle supplied in the
adjacent territory.