S1 anterior ramus
Roots · S1
Largest sacral ramus. Joins the lumbosacral trunk on the anterior surface of piriformis to form the upper band of the sacral plexus, contributing to the sciatic and both gluteal nerves.
Detail
- Dermatome
- Lateral foot, little toe, sole, posterior calf
- Myotome
- Plantarflexion, eversion, hip extension
- Reflex
- Ankle jerk (S1)
When it goes wrong
L5/S1 disc prolapse compressing the S1 root
Sciatica down the posterior thigh and calf, weak plantarflexion (cannot rise onto tiptoes), absent ankle jerk, numb lateral foot and sole
Practise this structure
1 question in the bank tagged Reflexes.