Anatomy
Summary
The sciatic nerve, originating from the anterior and posterior divisions of the anterior rami of L4-S3, courses beneath the piriformis muscle and exits via the greater sciatic notch. It then splits into two primary branches: the common peroneal nerve and the tibial nerve. This multifunctional nerve provides both sensory and motor innervation; it delivers sensation to the posterior and lateral portions of the leg and foot, excluding the medial aspect. For motor functions, it innervates muscles in the posterior thigh including the semitendinosus, semimembranosus, biceps femoris, and the hamstrings part of the adductor magnus.
Injury to the sciatic nerve can arise from various factors, such as hip dislocations, femoral neck fractures, hip arthroplasty, piriformis syndrome, and improperly administered intramuscular gluteal injections. Such injuries can lead to sensory loss in the posterior and lateral regions of the calf and foot, as well as motor deficits affecting the hamstrings. These injuries often culminate in a loss of the achilles reflex, serving as a key diagnostic indicator.
Lesson Outline
Don't stop here!
Get access to 51 more Anatomy lessons & 13 more medical school learning courses with one subscription!
FAQs
The Sciatic Nerve is the largest nerve in the body, originating from the Lumbosacral Plexus. It forms from spinal nerves L4 through S3, exits the pelvis, and runs down the leg, innervating numerous muscles and skin.
The sciatic nerve branches into the common peroneal nerve and the tibial nerve, each with distinct sensory responsibilities in the lower extremity. The common peroneal nerve supplies the lateral aspect of the leg and dorsum of the foot, while the tibial nerve takes provides sensation for the posterior leg and plantar surface of the foot. Injury to the sciatic nerve or its branches can result in sensory deficits, such as numbness or tingling, in their respective domains.
The sciatic nerve primarily supplies the posterior thigh muscles, which include the semitendinosus, semimembranosus, and biceps femoris. It also supplies the hamstrings portion of the adductor magnus muscle. These muscles are primarily involved in knee flexion and hip extension.
Injury to the sciatic nerve can result from various causes, such as hip dislocations, femoral neck fractures, and hip arthroplasty. Piriformis syndrome, which is the compression of the sciatic nerve by the piriformis muscle, is also a common cause. Additionally, improper intramuscular gluteal injections can lead to sciatic nerve injury.
An injury to the sciatic nerve impacts both sensory and motor functions, thanks to its two main branches: the common peroneal nerve and the tibial nerve. Sensory loss can manifest in the lateral leg and dorsum of the foot, as well as the posterior leg and plantar surface of the foot. Motor deficits may include weakness in knee flexors and hip extensors such as semitendinosus, semimembranosus, and biceps femoris. Additionally, you might experience difficulty in foot and toe movements. A compromised sciatic nerve often results in the loss of the achilles reflex, an important indicator of nerve dysfunction.
MCAT® is a registered trademark of the Association of American Medical Colleges. The United States Medical Licensing Examination (USMLE®) is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). NAPLEX® is a registered trademark of the National Association of Boards of Pharmacy. PANCE© is a registered trademark of the National Commission on Certification of Physician Assistants. NCLEX® is a registered trademark and service mark of the National Council of State Boards of Nursing, Inc. None of the trademark holders are endorsed by nor affiliated with Sketchy or this website.
