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Nail bed corion (hand)

The nail bed corium (also called the nail bed dermis) is the highly vascular, innervated connective tissue layer located beneath the nail plate. It binds tightly to the distal phalanx and is responsible for supporting the nail plate, nourishing the nail matrix, and facilitating nail growth and adherence.

The corium is composed of dense collagenous tissue, rich capillary loops, sensory nerve endings, and specialized fibroblasts. It forms a continuous structure with the nail matrix proximally and the hyponychium distally. Because of its vascularity and adherence to the distal phalanx, injuries to the corium are often painful and bleed readily.

Synonyms

  • Nail bed dermis

Relations

  • Dorsally: Nail plate

  • Ventrally: Periosteum and cortex of distal phalanx

  • Proximally: Nail matrix and eponychium

  • Distally: Hyponychium and fingertip pulp

  • Laterally: Nail folds

Attachments

  • Anchored to distal phalanx via dense fibrous septa

  • Firm adhesion to nail plate through interdigitating epidermal ridges

  • Supports capillary loops that create the pink coloration of the nail

Function

  • Supports and nourishes the nail plate

  • Provides a smooth surface for nail gliding

  • Rich capillary network supplies oxygen and nutrients

  • Sensory structure for fine tactile detection

  • Plays a key role in nail adhesion and growth stability

Clinical Significance

  • Injuries to the corium cause intense pain and bleeding

  • Infections can spread to distal phalanx (risk of osteomyelitis)

  • Nail bed lacerations require precise repair to avoid permanent nail deformity

  • Psoriasis and lichen planus commonly affect the nail bed

  • Crush injury may lead to subungual hematoma formation

MRI Appearance

T1-weighted images:

  • Nail plate: low signal

  • Corium: intermediate signal due to vascular connective tissue

  • Distal phalanx cortex: very low signal

  • Bone marrow beneath nail bed: bright T1 signal

T2-weighted images:

  • Nail plate: low signal

  • Corium: intermediate-to-high signal (soft tissue with small vessels)

  • Epidermal layer: thin low-signal interface

  • Distal phalanx bone: low signal with bright marrow

STIR:

  • Nail bed corium: intermediate-to-dark signal

  • Enhanced contrast between corium and surrounding fat

  • Highlights soft tissue planes under nail plate

CT Appearance

Non-Contrast CT:

  • Nail plate: thin, mildly hyperattenuating structure

  • Corium: soft-tissue density between nail plate and distal phalanx

  • Distal phalanx: dense cortical bone with trabecular core

  • Good visualization of nail-bed relationship to bone

Post-Contrast CT:

  • Corium: mild uniform enhancement due to vascularity

MRI images

Nail bed corion hand MRI axial image-img-00000-00000