A fascia (; plural fasciae or fascias; adjective fascial; from Latin: "band") is a band or sheet of

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

, primarily

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...

, beneath the skin that attaches to, stabilizes, encloses, and separates

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

s and other internal organs. Fascia is classified by layer, as

superficial fascia A fascia (; plural fasciae or fascias; adjective fascial; from Latin: "band") is a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches to, stabilizes, encloses, and separates muscles and other internal orga ...

, deep fascia, and ''visceral'' or ''parietal'' fascia, or by its function and anatomical location. Like

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

s, aponeuroses, and tendons, fascia is made up of fibrous connective tissue containing closely packed bundles of collagen fibers oriented in a wavy pattern parallel to the direction of pull. Fascia is consequently flexible and able to resist great unidirectional tension forces until the wavy pattern of fibers has been straightened out by the pulling force. These collagen fibers are produced by

fibroblast A fibroblast is a type of cell (biology), biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (Stroma (tissue), stroma) for animal Tissue (biology), tissues, and plays a critical role in wound ...

s located within the fascia. Fasciae are similar to ligaments and tendons as they have collagen as their major component. They differ in their location and function: ligaments join one bone to another bone, tendons join muscle to bone, and fasciae surround muscles and other structures.

Structure

There exists some controversy about what structures are considered "fascia", and how types of fascia should be classified. The two most common systems are: * The one specified in the 1983 edition of

Nomina Anatomica ''Nomina Anatomica'' (''NA'') was the international standard on human anatomic terminology from 1895 until it was replaced by ''Terminologia Anatomica'' in 1998. In the late nineteenth century some 30,000 terms for various body parts were in use ...

(NA 1983) * The one specified in the 1997 edition of Terminologia Anatomica (TA 1997)

Superficial fascia

Superficial fascia is the lowermost layer of the skin in nearly all of the regions of the

body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of anima ...

, that blends with the

reticular dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided in ...

layer. It is present on the face, over the upper portion of the

sternocleidomastoid The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the access ...

, at the nape of the

neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...

, and overlying the

breastbone The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sh ...

. It consists mainly of loose areolar, and fatty adipose

and is the layer that primarily determines the shape of a body. In addition to its

subcutaneous Subcutaneous may refer to: * Subcutaneous injection * Subcutaneous tissue The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The ...

presence, superficial fascia surrounds organs and glands,

neurovascular bundle A neurovascular bundle is a structure that binds nerves and veins (and in some cases arteries and lymphatics) with connective tissue so that they travel in tandem through the body. Structure There are two types of neurovascular bundles: superficia ...

s, and is found at many other locations where it fills otherwise unoccupied space. It serves as a storage medium of fat and water; as a passageway for lymph,

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

and

blood vessels The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...

; and as a protective padding to cushion and insulate. Superficial fascia is present, but does not contain fat, in the eyelid, ear, scrotum, penis and

clitoris The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), above the ope ...

. Due to its viscoelastic properties, superficial fascia can stretch to accommodate the deposition of adipose that accompanies both ordinary and prenatal weight gain. After pregnancy and weight loss, the superficial fascia slowly reverts to its original level of tension.

Visceral fascia

Visceral fascia (also called subserous fascia) suspends the organs within their cavities and wraps them in layers of connective tissue

membranes A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...

. Each of the organs is covered in a double layer of fascia; these layers are separated by a thin serous membrane. * The outermost wall of the organ is known as the parietal layer * The skin of the organ is known as the visceral layer. The organs have specialized names for their visceral fasciae. In the brain, they are known as

meninges In anatomy, the meninges (, ''singular:'' meninx ( or ), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in th ...

; in the heart they are known as pericardia; in the lungs, they are known as pleurae; and in the abdomen, they are known as peritonea. Visceral fascia is less extensible than superficial fascia. Due to its suspensory role of the organs, it needs to maintain its tone rather consistently. If it is too lax, it contributes to organ prolapse, yet if it is

hypertonic In chemical biology, tonicity is a measure of the effective osmotic pressure gradient; the water potential of two solutions separated by a partially-permeable cell membrane. Tonicity depends on the relative concentration of selective membrane- ...

, it restricts proper organ motility.

Deep fascia

Deep fascia is a layer of dense fibrous connective tissue which surrounds individual

s, and also divides groups of muscles into fascial compartments. This fascia has a high density of

elastin Elastin is a protein that in humans is encoded by the ''ELN'' gene. Elastin is a key component of the extracellular matrix in gnathostomes (jawed vertebrates). It is highly elastic and present in connective tissue allowing many tissues in the bod ...

fibre that determines its

extensibility Extensibility is a software engineering and systems design principle that provides for future growth. Extensibility is a measure of the ability to extend a system and the level of effort required to implement the extension. Extensions can be th ...

or resilience. Deep fascia was originally considered to be essentially avascular but later investigations have confirmed a rich presence of thin blood vessels. Deep fascia is also richly supplied with

sensory receptor Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The cell ...

s. Examples of deep fascia are

fascia lata The fascia lata is the deep fascia of the thigh. It encloses the thigh muscles and forms the outer limit of the fascial compartments of thigh, which are internally separated by the medial intermuscular septum and the lateral intermuscular septu ...

fascia cruris The deep fascia of leg, or crural fascia forms a complete investment to the muscles, and is fused with the periosteum over the subcutaneous surfaces of the bones. The deep fascia of the leg is continuous above with the fascia lata (deep fascia of ...

brachial fascia The brachial fascia (deep fascia of the arm) is continuous with that covering the deltoideus and the pectoralis major muscle, by means of which it is attached, above, to the clavicle, acromion, and spine of the scapula; it forms a thin, loose, me ...

, plantar fascia, thoracolumbar fascia and

Buck's fascia Buck's fascia (deep fascia of the penis, Gallaudet's fascia or fascia of the penis) is a layer of deep fascia covering the three erectile bodies of the penis. Structure Buck's fascia is continuous with the external spermatic fascia in the scrotu ...

Function

Fasciae were traditionally thought of as passive structures that transmit mechanical tension generated by muscular activities or external forces throughout the body. An important function of muscle fasciae is to reduce friction of muscular force. In doing so, fasciae provide a supportive and movable wrapping for nerves and blood vessels as they pass through and between muscles. Fascial tissues are frequently innervated by sensory nerve endings. These include myelinated as well as unmyelinated nerves. Based on this a proprioceptive, nociceptive as well as

interoceptive Interoception is contemporarily defined as the collection of senses perceiving the internal state of the body. This can be both conscious and unconscious. It encompasses the brain's process of integrating signals relayed from the body into specif ...

function of fascia has been postulated. Fascial tissues – particularly those with tendinous or aponeurotic properties – are also able to store and release elastic potential energy.

Clinical significance

Fascia becomes important clinically when it loses stiffness, becomes too stiff, or has decreased shearing ability. When inflammatory

fasciitis Fasciitis is an inflammation of the fascia, which is the connective tissue surrounding muscles, blood vessels and nerves. In particular, it often involves one of the following diseases: * Necrotizing fasciitis * Plantar fasciitis * Ischemic fasc ...

or trauma causes fibrosis and adhesions, fascial tissue fails to differentiate the adjacent structures effectively. This can happen after surgery, where the fascia has been incised and healing includes a scar that traverses the surrounding structures.

Anatomical compartments

A fascial compartment is a section within the body that contains muscles and nerves and is surrounded by fascia. In the

human body The human body is the structure of a Human, human being. It is composed of many different types of Cell (biology), cells that together create Tissue (biology), tissues and subsequently organ systems. They ensure homeostasis and the life, viabi ...

, the limbs can each be divided into two segments: The upper limb can be divided into the arm and the forearm and the sectional compartments of both of these – the fascial compartments of the arm and the fascial compartments of the forearm contain an anterior and a posterior compartment. The lower limbs can be divided into two segments – the leg and the thigh – and these contain the fascial compartments of the leg and the fascial compartments of the thigh. A

fasciotomy Fasciotomy or fasciectomy is a surgical procedure where the fascia is cut to relieve tension or pressure in order to treat the resulting loss of circulation to an area of tissue or muscle. Fasciotomy is a limb-saving procedure when used to trea ...

may be used to relieve compartment syndrome as a result of high pressure within a fascial compartment.

References

External links

Fascia Research
* {{Authority control Connective tissue