endplates

Endplates is a term used to describe specialized plate-like structures in various biological contexts. The most common references are vertebral endplates and motor endplates (the postsynaptic specialization of the neuromuscular junction).

Vertebral endplates are thin layers of cartilage that cap the superior and inferior aspects of each vertebral body, forming the interface with the intervertebral disc. They consist mainly of hyaline cartilage and a calcified cartilage zone that anchors to subchondral bone. Their function is to transmit mechanical loads between the disc and vertebral body and to regulate nutrient exchange by acting as a diffusion barrier for the avascular disc tissue. The integrity of endplates is important for disc health; defects or degeneration can accompany degenerative disc disease and may be associated with Modic changes and Schmorl’s nodes, which involve intrusion of disc material into the adjacent vertebral body.

Motor endplates are specialized postsynaptic regions on muscle fibers at the neuromuscular junction. They feature deep folds of the muscle fiber membrane, rich in acetylcholine receptors, which maximize the surface area available for receptor activation by acetylcholine released from the presynaptic nerve terminal. This arrangement converts a chemical signal into an electrical depolarization that triggers muscle contraction. Disorders affecting the endplates, most notably myasthenia gravis, involve impaired transmission at the neuromuscular junction and present with fatigable weakness.

In some contexts, endplates may refer to other plate-like components in engineered or imaging terminology, but in biology the two main types are vertebral endplates and motor endplates.