Free medical quiz
The Sacral Plexus Quiz
Focused SBA-style practice, followed by the answer and explanation for every question.
- Free now
- 5 questions
- Full bank
- 7 questions
- Answers
- Explained
Free question
Try one with the answer
A question from this quiz. Answer it to see the explanation students get.
Which of the following nerves is a major peripheral nerve of the sacral plexus?
- A Obturator nerve You picked ✕
- B Genitofemoral nerve You picked ✕
- C Ilioinguinal nerve You picked ✕
- D Femoral nerve You picked ✕
- E Sciatic nerve You picked ✓
Correct!
Incorrect
The answer is E: Sciatic nerve
Explanation
Why E is correct
See Peripheral Nerves of the Sacral Plexus. Option E is correct. The sacral plexus is a network of nerves on the back wall of the pelvis, in front of the piriformis muscle (a small, pear-shaped muscle deep in the buttock), formed by the anterior rami of S1 to S4 together with L4 and L5, which arrive through the lumbosacral trunk. Its five major peripheral nerves are the superior gluteal, inferior gluteal, sciatic, posterior femoral cutaneous and pudendal nerves. The sciatic nerve (L4 to S3) is the largest of them and the largest nerve in the body, about 2 cm wide. It leaves the pelvis through the greater sciatic foramen below piriformis, runs down the back of the thigh supplying the hamstring muscles, and divides near the back of the knee into the tibial and common fibular nerves. It is really two nerves in one sheath, so through its two divisions it supplies all the muscles below the knee and most of the skin of the leg and foot. A good way to avoid mixing up the two plexuses is to learn each list with its own memory aid: the lumbar plexus is 'I, I Get Leftovers On Fridays' and the sacral plexus is 'Some Irish Sailor Pesters Polly', with the sciatic nerve third.
- Roots: L4 to S3
- Size: the largest nerve in the body, about 2 cm wide
- Course: leaves the pelvis through the greater sciatic foramen below piriformis
- Divisions: tibial and common fibular nerves in one sheath, dividing near the back of the knee
Why the other options are incorrect
- A. Obturator nerve: The obturator nerve is also a lumbar plexus nerve (L2 to L4) from the back wall of the abdomen, and it supplies the adductors of the inner thigh. It does not come from the sacral roots. Your answer
- B. Genitofemoral nerve: The genitofemoral nerve is formed from L1 and L2 within the lumbar plexus on the back wall of the abdomen. Its branches supply the cremaster muscle and the skin of the genital region and upper thigh. Your answer
- C. Ilioinguinal nerve: The ilioinguinal nerve is a lumbar plexus nerve with a root of L1 and supplies the lower abdominal wall and the groin. It belongs to the plexus higher up the back of the abdomen. Your answer
- D. Femoral nerve: The femoral nerve comes from the lumbar plexus (L2 to L4) on the back wall of the abdomen and supplies the front of the thigh. It would be the answer if the question asked about the lumbar plexus. Your answer
With Premium, questions you miss become Revision Coach flashcards, scheduled for review.
Question preview
What you will practise
More questions from this set. Start the quiz to answer them and see each explanation.
-
1
Which set of spinal nerve roots forms the pudendal nerve?
-
2
Which nerve of the sacral plexus leaves the pelvis through the greater sciatic foramen and supplies the muscles at the back of the thigh?
Revise before you test
Review SimpleMed's doctor-written article, then return here to check recall.
Read the topic articleNeed wider coverage?
Explore every Musculoskeletal System topic set, or build a tailored mixed session.
Browse subject quizzes