Subcutaneous tissue

In arthropods, a hypodermis can refer to an epidermal layer of cells that secretes the chitinous cuticle. The term also refers to a layer of cells lying immediately below the epidermis of plants.

Structure

• Fibrous bands anchoring the skin to the deep fascia
• Collagen and elastin fibers attaching it to the dermis
• Fat is absent from the eyelids, clitoris, penis, much of pinna, and scrotum
• Blood vessels on route to the dermis
• Lymphatic vessels on route from the dermis
• The glandular part of some sweat glands; mammary glands lie entirely within the subcutaneous tissue (which are modified apocrine sweat glands)
• Cutaneous nerves and free endings
• Hair follicle roots
• Ruffini and Pacinian corpuscles
• Mast cells
• 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 scrotum, called the panniculus carnosus

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

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.

Subcutaneous fat

Subcutaneous fat is the most widely distributed subcutaneous tissue layer. It is composed of adipocytes, which are grouped together in lobules separated by connective tissue. The number of adipocytes varies among different body areas, while their size varies according to the body's nutritional state. It acts as padding and as an energy reserve, as well as providing some minor thermoregulation via insulation. Subcutaneous fat is found just beneath the skin, as opposed to visceral fat, which is found in the peritoneal cavity, and can be measured using body fat calipers to give a rough estimate of total body adiposity.