## **Core Concept**
The lumbar plexus is a complex neural network formed by the ventral divisions of the first four lumbar nerves (L1-L4) and contributions from the T12 (subcostal nerve) and L5 spinal nerves. It supplies the lower limb, providing motor and sensory innervation to various regions.

## **Why the Correct Answer is Right**
The obturator nerve, femoral nerve, and liliohypogastric nerve are all branches of the lumbar plexus. The obturator nerve arises from L2-L4, the femoral nerve from L2-L4, and the iliohypogastric nerve from L1. The dorsal scapular nerve, however, originates from the brachial plexus, specifically from the C5 root.

## **Why Each Wrong Option is Incorrect**
- **Option A:** The obturator nerve is indeed a branch of the lumbar plexus, providing sensory innervation to the medial thigh and motor innervation to the adductor muscles.
- **Option B:** The femoral nerve is a major branch, responsible for motor supply to the anterior thigh muscles and sensory supply to the anterior and medial thigh and leg.
- **Option C:** The iliohypogastric nerve is also a branch, providing sensory innervation to the lower abdominal and hip regions.

## **Why Option D is Correct (Implicit):**
- **Option D:** The dorsal scapular nerve is not a branch of the lumbar plexus; instead, it arises from the C5 root of the brachial plexus, supplying the rhomboids and levator scapulae muscles.

## **Clinical Pearl / High-Yield Fact**
A useful clinical correlation is that the lumbar plexus nerves can be affected in conditions like psoas major muscle hematoma or abscess, leading to symptoms such as thigh weakness and sensory disturbances.

## **Correct Answer:** D. Dorsal scapular nerve.