Posterior horn of spinal cord

The posterior horn of spinal cord is part of the spinal gray matter which is situated dorsal to the central canal. It is sensory in function and is the place where information from the body surface and underlying tissues first reaches the central nervous system.

The posterior horn of spinal cord extends throughout the length of the cord. According to the old literature, it is divisible into various sub-parts, including an apex, a head, a neck and a base. The posterior horn can also be divided into distinct layers or laminae–called the Rexed laminae–based on the cytoarchitectural details of the cells in these regions. Rexed lamina I is the thinnest of all and corresponds with the apex of posterior horn. Lamina III and IV correspond with the head of posterior horn. Lamina II caps the head of posterior horn (with some considering it to be a part of the head). Lamina V and VI lie in the neck and the base of posterior horn, respectively. Some consider lamina VII (zona intermedia) as part of the base as well.

The posterior horn of spinal cord contains different groups of sensory nuclei, which are positioned in dedicated Rexed laminae mentioned above. These nuclei include the ‘marginal zone nucleus’ (lamina I), ‘substantia gelatinosa’ (lamina II), ‘nucleus proprius’ (laminae III and IV, with slight projection into lamina V as well), ‘dorsal nucleus of Clarke or posterior thoracic nucleus’ (lamina VII) and the ‘visceral afferent nucleus’ (lamina VII).

Sensory information of pain and temperature is relayed into the substantia gelatinosa (and marginal zone) nuclei by first order neurons of spinothalamic pathway. Similarly, sensory information pertaining to conscious proprioception, vibration, and 2-point discrimination gets transmitted to nucleus proprius by collaterals from first order neurons of dorsal column pathway. Moreover, subconscious proprioceptive information from cerebellum gets relayed into dorsal nucleus of Clarke, while the visceral afferent information gets transmitted to the visceral afferent nucleus in the posterior horn of spinal cord. Every type of sensory information gets eventually relayed inside the thalamus, prior to reaching the primary sensory cortex.