Hypodermis

The hypodermis is the layer of loose connective tissue immediately deep to the dermis of the skin. A lay term for this region that should be avoided is that of 'subcutaneous tissue' which could imply any tissue deep to the hypodermis. It has lead to hypodermal injections being termed 'subcutaneous'. The anatomical terms for this region are superficial fascia and panniculus adiposus. However, the latter is preferred as superficial fascia bears little comparison to the deep fascia.

The hypodermis contains:

• loosely arranged elastic fibres
• fibrous bands anchoring skin to deep fascia
• fat:
  • absent in eyelid, scrotum, penis, nipple and areola
  • distribution is a secondary sexual characteristic: it forms the breasts of females and accentuates the contour of female hips
• blood vessels on route to dermis
• lymphatic vessels on route from dermis
• hair follicle roots
• the glandular part of some sudiferous glands
• nerves:
  • free endings
  • Panicinian corpuscles
• bursae: only in the space overlying joints in order to facilitate smooth passage of overlying skin
• sheets of muscle: panniculus carnosus