Subcutaneous Tissue

The subcutaneous tissue consists of fat (adipose tissue), connective tissue, and blood vessels. It serves several purposes, including padding and protecting the bones, muscles, and organs underneath from physical damage.


a, b Longitudinal and transverse 12-5 MHz US images show fluid distention of fat lobules with hypoechoic background in a patient with foreign-body-related subcutaneous abscess. The abscess contains pus, WBCs and debris.


Like the pads a football player wears for protection, subcutaneous tissue serves as padding for your organs and muscles against shock or changes in temperature. It also acts as a layer of insulation to conserve body heat.

The spongy, resilient nature of this tissue makes it an excellent insulator. Adipose (fat-storing) tissue acts as an additional insulator, as fat molecules are poor conductors of heat.

As we age, our subcutaneous tissue thins out, which makes the body less efficient at keeping itself warm and increases its sensitivity to cold temperatures. It can also affect how well medications injected into this tissue are absorbed.

Sometimes foreign bodies, such as wood splinters, glass, metal or thorns can get into the subcutaneous tissue after a traumatic injury or therapeutic procedure. These can lead to granuloma formation, secondary soft-tissue infection with the development of abscesses, fistula or purulent tenosynovitis and/or septic arthritis. US is often used to assess the twisting of injection ports surgically inserted into the subcutaneous tissue for injections. This twisting can be a sign of infection, fluid accumulation and possible failure of the procedure.

Shock Absorption

The large proportion of fat in the subcutaneous layer makes it a good insulator, protecting the deeper tissues like muscles and organs from changes in temperature. It also absorbs shock to limit damage. It connects the skin to the underlying muscles and bones, and it stores energy in fat cells.

The layer also produces sweat to regulate the body’s temperature, and it helps the skin move smoothly over the underlying tissues and muscles without rubbing against them. It also functions as a buffer to disperse the impact of running or jumping, limiting injuries to the bones and muscles.

The subcutaneous layer has fewer blood vessels than muscle, so medicines injected into it are absorbed much slower. This is why the skin must be cleaned well before injection. People can develop abscesses, which are pockets of pus, in the subcutaneous layer. These can occur if germs enter the subcutaneous tissue and the immune system reacts with inflammation. They can also develop pressure ulcers, which are a type of skin injury that occurs when someone spends prolonged time in bed or in a wheelchair.

Structural Support

Besides insulating and regulating temperature, the subcutaneous tissue also acts as a shock absorber and a store of fat energy for the body. Blood vessels, nerves, hair follicles, and lymph vessels pass through this layer.

This layer is thickest in the buttocks and palms of the hands. It contains adipose cells and connective tissues. Its structure provides support for the body and allows it to move with ease.

Light microscopy shows a dense layer of adipose tissue with an undulating pattern of dermal papillae and rete ridges. It has strong connections with the subjacent galea aponeurotica and with the superficial fascia.

The deepest layer of the skin, the subcutaneous tissue is a network of fat and collagen cells. It helps to insulate and protect the bones, muscles, and organs underneath it. It also protects against abrasion and other forms of physical injury. The adipose cells in the subcutaneous tissue help regulate the body’s temperature by storing and releasing excess heat. The size of these adipose cells is determined by a person’s diet and lifestyle habits.

Energy Storage

The subcutaneous layer primarily contains fat, which acts as an insulator to regulate the body’s temperature independent of the environment. It also stores energy in the form of triglyceride esters and glycogen, which can be used during periods of scarcity of other nutrients.

Fat tissue is thicker in warmer areas of the body (such as the palms of the hands and thighs), but thinner in cooler regions (such as the chest and abdomen). The amount and distribution of fatty tissue varies by person and sex; men tend to have larger adipocytes than women.

Subcutaneous fat is a rich source of lipid-soluble gases, such as carbon dioxide and hydrogen. These gases can be absorbed into the blood and converted to energy during b oxidation.

Medicine Injections

Subcutaneous injection (also known as sub-Q or SQ injection) is a popular method for drug delivery. It allows the drug to be delivered directly into fatty tissue where it will dissolve and be absorbed by the body. Medications such as insulin, pain medications and nausea/vomiting preventatives are commonly administered this way.

A patient can be taught how to self-administer their medication by using an injection pen, which contains prefilled cartridges of medicine and a needle. Teaching the correct injection technique is essential to ensure that the medication is injected correctly and effectively. It is also important to teach the patient about the proper storage and administration of their medications.

Injection of drugs into the subcutaneous and muscle tissues is dependent on many factors, such as injection conditions, injected site, local available space and body movements. This study, using X-ray imaging with high spatial resolution, investigated the effects of injection conditions on the permeation and diffusion characteristics of a drug solution in porcine subcutaneous and muscle tissues. These results will provide important information for the design of injection devices that minimize variability, skin disorder and pain during drug injections.