[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › [Cardiovascular](https://durgical.com/en/physiology/#s-cardio) › Skin blood flow [Physiology](https://durgical.com/en/physiology/) · [Cardiovascular](https://durgical.com/en/physiology/#s-cardio) # Skin blood flow - Regulation - For completeness Skin gets far more blood than it needs for its own nutrition, because its flow is mostly used to control body temperature. Updated 2026-11-01 **See it in 3D:** [Skin](https://durgical.com/en/anatomy/skin/) ## Key points - At rest in a neutral temperature skin gets ≈3 mL/min per 100 g; in heat it can reach about 30% of output. - The arteriovenous anastomoses of hands, feet and ears get only sympathetic vasoconstrictor fibers: in heat they open when tone is withdrawn. - On the trunk and limbs heat vasodilation is active, linked to the sympathetic cholinergic sweat fibers. - Cold and sympathetic discharge (shock, pain, fear) constrict the skin: pallor and coolness. - Skin is a blood reservoir: in hemorrhage it shuts down to divert flow to the brain and heart. ## What it is Skin blood flow can range from almost zero to about 30% of cardiac output. A venous plexus beneath the skin, fed in the hands, feet and ears by arteriovenous anastomoses, carries heat from the core to the surface. The hypothalamus controls that flow through the sympathetic system: in the cold it shuts flow down to keep heat, in the heat it opens it to lose heat. ## How it works, step by step - Thermoreceptors and blood temperature inform the hypothalamus. - In the cold, noradrenergic sympathetic tone rises: arterioles and anastomoses constrict and the skin insulates the core. - Local cold also makes the vessels more sensitive to norepinephrine. - In the heat, constrictor tone is withdrawn and sympathetic cholinergic fibers dilate the skin and drive sweating. - The venous plexus fills and heat moves to the surface, where it is lost by radiation, convection and evaporation. - In exercise in the heat, skin and muscle compete for output: heart rate climbs higher and performance falls. ## Regulation - *+* **Heat and a breaking fever (sympathetic withdrawal, cholinergic fibers)**: Skin vasodilation: flushing, warm skin and heat loss. - *+* **Local heat and inflammatory mediators**: Reddening of the area (erythema). - *−* **Cold and the chill at the start of a fever**: Vasoconstriction: pale, cold skin; heat is conserved. - *−* **Sympathetic discharge in shock, pain or fear**: Cold, clammy skin; flow is diverted to vital organs. ## Clinical notes - Raynaud phenomenon: exaggerated digital vasospasm with cold or stress: white, blue, then red; it may accompany lupus or scleroderma. - In hypovolemic shock, cold skin and slow capillary refill reflect sympathetic vasoconstriction; in early septic shock the skin may be warm. - In the hot climate of Colombia's coast, hard exercise demands a lot of skin blood flow and raises the risk of heat exhaustion. ## Memory aid "Skin is the radiator": open in the heat, closed in the cold and switched off in shock. ## Test yourself Think of the answer, then tap the question to see it. ## Why is the skin of a patient in hypovolemic shock cold and pale? Sympathetic discharge constricts skin arterioles and anastomoses to divert blood to brain and heart; the skin gets very little flow and loses warmth. ## Which structure in the hands, feet and ears lets skin flow change so much for temperature control? Arteriovenous anastomoses, which carry blood straight from arterioles to the venous plexus and are controlled by sympathetic vasoconstrictor fibers. ## Why is exercise in a hot environment harder on the heart? The skin needs a lot of flow to shed heat and competes with muscle for cardiac output; sweating also lowers plasma volume. ## What explains the color changes in Raynaud phenomenon? First the vasospasm turns the digits white; stagnant blood deoxygenates and looks blue; when the spasm eases, reactive hyperemia turns them red. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/physiology/skin-blood-flow/) ## See it in 3D The structures of Durgical's 3D anatomy where it happens. - [Skin](https://durgical.com/en/anatomy/skin/) ## Related topics - [Local and humoral control of blood flow](https://durgical.com/en/physiology/local-and-humoral-control-of-blood-flow/) - [Nervous control of the circulation and the CNS ischemic response](https://durgical.com/en/physiology/nervous-control-of-the-circulation-and-the-cns-ischemic-response/) - [Muscle blood flow and the cardiovascular response to exercise](https://durgical.com/en/physiology/muscle-blood-flow-and-the-cardiovascular-response-to-exercise/) - [The response to standing up](https://durgical.com/en/physiology/the-response-to-standing-up/) ## Related conditions - [Raynaud phenomenon](https://durgical.com/en/conditions/raynaud-phenomenon/) - [Systemic lupus erythematosus](https://durgical.com/en/conditions/systemic-lupus-erythematosus/) - [Hypovolaemic shock](https://durgical.com/en/conditions/hypovolaemic-shock/) - [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/) [← All of physiology](https://durgical.com/en/physiology/) Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given. Sources: [5.3 Functions of the Integumentary System](https://openstax.org/books/anatomy-and-physiology-2e/pages/5-3-functions-of-the-integumentary-system) (OpenStax (Rice University), 2022); [Physiology, Integument](https://www.ncbi.nlm.nih.gov/books/NBK554386/) (StatPearls (NCBI Bookshelf), 2023); [Raynaud Disease](https://www.ncbi.nlm.nih.gov/books/NBK499833/) (StatPearls (NCBI Bookshelf), 2026); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 74). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/physiology/skin-blood-flow/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/skin-blood-flow/