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
Anatomy of Circulation• The vascular plexuses of the fascia, subcutaneous tissue and skin are divided into 6 layers
Anatomy of Circulation1)Subfascial plexus small plexus lying on the undersurface of the fascia
Anatomy of Circulation2) Prefascial plexus -a larger plexus -particularly prominent on the limbs -fasciocutaneous vessels
Anatomy of Circulation3)Subcutaneous Plexus -lies at the level of superficial fascia -Predominant on the torso -musculocutaneous vessels
Anatomy of Circulation4)Subdermal Plexus -receives blood from underlying plexus -the main plexus supplying blood to the skin -represents the dermal bleed observed in incised skin
Anatomy of Circulation5) Dermal Plexus -mainly arterioles -important in thermoregulation
Anatomy of Circulation6)Subepidermal Plexus -contains small vessels without muscle in the walls -nutritive and thermoregulatory function
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
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.
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
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.
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
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
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
The angiosome concept has important clinical implications1) 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.
The angiosome concept has important clinical implications3) 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.