Deep (cutaneous) vascular plexus and arteriovenous anastomoses
Reticular dermis · AV anastomoses Thermoregulation α1 constrictor tone
Horizontal plexus at the dermal-hypodermal border, supplied by perforators from underlying muscle and fascia, that feeds the superficial plexus above it. Its arteriovenous anastomoses make skin blood flow the body's principal heat-exchange control.
Traced from the start
- Stratum basale (germinativum)
- Lamina densa (type IV collagen basement membrane)
- Subpapillary (superficial) vascular plexus
- Deep (cutaneous) vascular plexus and arteriovenous anastomoses
Detail
- Range of flow
- About 250 mL/min at rest, falling towards zero with maximal vasoconstriction and rising to 6-8 L/min in severe heat stress
- Vasoconstriction
- Sympathetic noradrenergic fibres acting on alpha-1 receptors; the dominant tone in the cold and in shock
- Vasodilatation
- Withdrawal of constrictor tone plus an active sympathetic vasodilator system released with sweating in the heat
- Arteriovenous anastomoses
- Glomus bodies in digits, palms, soles, ears and nose shunt blood past the capillaries for rapid heat loss or conservation
When it goes wrong
Cutaneous vasoconstriction in hypovolaemic or cardiogenic shock
Cold, pale, clammy peripheries with prolonged capillary refill and a widened core-to-peripheral temperature gap, while blood pressure may still be normal
Failure of cutaneous heat loss in exertional or classic heat stroke
Core temperature above 40 degrees Celsius with central nervous system dysfunction; treat with immediate active cooling, not antipyretics
Glomus tumour arising from an arteriovenous anastomosis
Exquisitely painful subungual lesion with cold sensitivity, relieved by excision
Practise this structure
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