NERVE INNERVATION
The mammary gland is innervated by both sensory and motor nerves. Sensory nerves, while not directly connected to alveolar cells or milk secretion, play a crucial role in milk ejection.
The sensory nerve supply to the udder originates from ventral branches of the first through fourth lumbar nerves. These nerves unite to form the inguinal nerve, which divides into cranial and caudal branches. The cranial branch innervates the cranial part of the front quarter, including the teat, while the caudal branch supplies the glandular tissue and rear quarter. The skin of the teat is rich in sensory receptors, particularly near the teat sphincter, stimulating sensory nerves essential for milk letdown via oxytocin release.Motor nerve supply primarily consists of fibers from the sympathetic system, regulating vasoconstriction and muscular constriction of the teat sphincter. Despite the cutaneous origin of the mammary gland, there is no parasympathetic nerve innervation. This complex innervation pattern complicates local anesthesia but simplifies teat surgery due to the vertical orientation of teat nerves within the teat wall.
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Source:
Rana Tanmoy (ed.). Principles of Veterinary Animal Physiology. CRC Press,2026. — 290 p.. 2026
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