The sacral spinal nerve 1 (S1) is a spinal nerve

Spinal nerve

The term spinal nerve generally refers to a mixed spinal nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body...

 of the sacral segment..

It originates from the spinal column from below the 1st body of the sacrum

Sacrum

In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...

 

Muscles

S1 supplies many muscles, either directly or through nerves originating from S1. They are not innervated with S1 as single origin, but partly by S1 and partly by other spinal nerves. The muscles are:

• gluteus maximus muscle
  Gluteus maximus muscle
  The gluteus maximus is the largest and most superficial of the three gluteal muscles...
  
  
• gluteus medius muscle
  Gluteus medius muscle
  The gluteus medius , one of the three gluteal muscles, is a broad, thick, radiating muscle, situated on the outer surface of the pelvis....
  
  
• gluteus minimus muscle
  Gluteus minimus muscle
  The gluteus minimus , the smallest of the three gluteal muscles, is situated immediately beneath the gluteus medius.-Origin and insertion:...
  
  
• tensor fasciae latae
  Tensor fasciae latae
  The tensor fasciae latae or tensor fasciæ latæ is a muscle of the thigh. The English name for this muscle is the muscle that stretches the band on the side...
  
  
• piriformis
  Piriformis muscle
  The piriformis is a muscle in the gluteal region of the lower limb. It was first named by Spigelius, a professor from the University of Padua in the 16th century.- Origin and insertion :...
  
  
• obturator internus muscle
  Obturator internus muscle
  The obturator internus muscle originates on the medial surface of the obturator membrane, the ischium near the membrane, and the rim of the pubis.It exits the pelvic cavity through the lesser sciatic foramen....
  
  
• inferior gemellus
  Inferior gemellus muscle
  The inferior gemellus muscle is a muscle of the human body.The Gemelli are two small muscular fasciculi, accessories to the tendon of the Obturator internus which is received into a groove between them....
  
  
• superior gemellus
  Superior gemellus muscle
  The superior gemellus muscle is a muscle of the human body.The Gemelli are two small muscular fasciculi, accessories to the tendon of the Obturator internus which is received into a groove between them....
  
  
• quadratus femoris
  Quadratus femoris muscle
  The quadratus femoris is a flat, quadrilateral skeletal muscle. Located on the posterior side of the hip joint, it is a strong external rotator and adductor of the thigh, but also acts to stabilize the femoral head in the Acetabulum.- Course :...
  
  
• semitendinosus
  Semitendinosus muscle
  The semitendinosus is a muscle in the back of the thigh; it is one of the hamstrings.-Structure:The semitendinosus, remarkable for the great length of its tendon of insertion, is situated at the posterior and medial aspect of the thigh ....
  
  
• gastrocnemius
  Gastrocnemius muscle
  In humans, the gastrocnemius muscle is a very powerful superficial pennate muscle that is in the back part of the lower leg. It runs from its two heads just above the knee to the heel, and is involved in standing, walking, running and jumping. Along with the soleus muscle it forms the calf muscle...
  
  
• flexor hallucis longus
  Flexor hallucis longus muscle
  The Flexor hallucis longus muscle is a muscle of the leg.It is one of the deep muscles of the posterior compartment of the leg. The other deep muscles of the leg are flexor digitorum longus and tibialis posterior. Tibialis posterior is most powerful of these deep muscles.The Flexor hallucis...
  
  
• abductor digiti minimi
  Abductor digiti minimi muscle (foot)
  The Abductor digiti minimi is a muscle which lies along the lateral border of the foot, and is in relation by its medial margin with the lateral plantar vessels and nerves....
  
  
• quadratus plantae
  Quadratus plantae muscle
  The Quadratus plantæ is separated from the muscles of the first layer by the lateral plantar vessels and nerve. It acts to aid in flexing the 2nd to 5th toes and is one of the few muscles in the foot with no homolog in the hand.It arises by two heads, which are separated from each other by the long...