hypodermis

A layer of tissue that lies immediately below the dermis of vertebrate skin. It is often referred to as subcutaneous tissue though this is a less precise and anatomically inaccurate term. The hypodermis consists primarily of loose connective tissue and lobules of fat. It contains larger blood vessels and nerves than those found in the dermis.

Specifically, the hypodermis contains:

Loosely arranged elastic fibers
Fibrous bands anchoring the skin to the deep fascia
Fat, except in the eyelid, scrotum, penis, nipple and areola
Blood vessels on route to the dermis
Lymphatic vessels on route from dermis
Hair follicle roots
The glandular part of some sudiferous glands
Nerves: free endings and Panicinian corpuscles
Bursae, in the space overlying joints in order to facilitate smooth passage of overlying skin
Fine, flat sheets of muscle, in certain locations, including the scalp, face, hand, nipple, and scrotuim, called the panniculus carnosus

In some animals, such as whales and hibernating mammals, the hypodermis forms an important insulating layer and/or food store.

In some plants, the hypodermis is a layer of cells immediately below the epidermis of leaves. It is often mechanically strengthened, for example, in pine leaves, forming an extra protective layer or a water storage tissue.

Related category

• ANATOMY AND PHYSIOLOGY

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