The joint that permits nodding of head while saying yes is?
**Core Concept**
The question is testing the anatomy of the neck and the specific joint responsible for the movement of the head in the sagittal plane. The joint involved is a synovial joint that allows for flexion and extension of the neck.
**Why the Correct Answer is Right**
The correct answer is the Atlanto-Occipital joint (AOJ). This joint is a synovial joint that connects the occipital bone of the skull to the atlas (C1) vertebra. The AOJ is responsible for the movement of the head in the sagittal plane, allowing for flexion (nodding) and extension (tilting back). The joint is stabilized by the ligaments, including the anterior atlanto-occipital membrane and the posterior atlanto-occipital membrane.
**Why Each Wrong Option is Incorrect**
* **Option A:** The Atlanto-Axial joint (AAJ) is located between the atlas (C1) and axis (C2) vertebrae and allows for rotation of the head. It is not responsible for flexion or extension of the neck.
* **Option B:** The Cervico-Thoracic joint is located between the cervical and thoracic vertebrae and allows for movement between the two regions. However, it is not responsible for the specific movement of nodding of the head.
* **Option C:** The Temporomandibular joint (TMJ) is located between the mandible and the temporal bone and allows for movement of the jaw. It is not responsible for the movement of the head in the sagittal plane.
**Clinical Pearl / High-Yield Fact**
The Atlanto-Occipital joint is a synovial joint that can be affected by conditions such as rheumatoid arthritis, causing instability and pain in the neck.
**Correct Answer: C. Atlanto-Occipital joint**