The interstitium is a
contiguous fluid-filled space existing between a structural barrier, such as a
cell membrane or the
skin, and internal structures, such as
organs, including
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 the
circulatory system.
The fluid in this space is called
interstitial fluid, comprises water and
solutes, and drains into the
lymph system.
The interstitial compartment is composed of
connective and supporting tissues within the body – called the
extracellular matrix – that are situated outside the blood and
lymphatic vessels and the
parenchyma
Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms.
Etymology
The term ''parenchyma'' is New Latin from the word π ...
of organs.
Structure
The non-fluid parts of the interstitium are predominantly 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 ...
types I, III, and V, 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 ...
, and glycosaminoglycans, such as hyaluronan
Hyaluronic acid (; abbreviated HA; conjugate base hyaluronate), also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminoglycans ...
and proteoglycan
Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a serine (Ser) residue to whic ...
s that are cross-linked to form a honeycomb-like reticulum.[ Such structural components exist both for the general interstitium of the body,][ and within individual organs, such as the myocardial interstitium of the heart,]lung
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
.
The interstitium in the submucosae of visceral organs, the dermis, superficial fascia, and perivascular adventitia are fluid-filled spaces supported by a collagen bundle lattice. The fluid spaces communicate with draining lymph nodes though they do not have lining cells or structures of lymphatic channels.
Functions
The interstitial fluid is a reservoir and transportation system for nutrients and solutes distributing among organs, cells, and capillaries, for signaling molecules communicating between cells, and for antigens and cytokines participating in immune regulation.[ The composition and chemical properties of the interstitial fluid vary among organs and undergo changes in chemical composition during normal function, as well as during body growth, conditions of inflammation, and development of diseases,][ as in ]heart failure
Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...
[ and ]chronic kidney disease
Chronic kidney disease (CKD) is a type of kidney disease in which a gradual loss of kidney function occurs over a period of months to years. Initially generally no symptoms are seen, but later symptoms may include leg swelling, feeling tired, vo ...
.[
The total fluid volume of the interstitium during health is about 20% of body weight, but this space is dynamic and may change in volume and composition during immune responses and in conditions such as cancer, and specifically within the interstitium of tumors.][ The amount of interstitial fluid varies from about 50% of the tissue weight in skin to about 10% in ]skeletal 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 ...
.[
]
Disease
In people with lung diseases, heart disease, cancer, kidney disease, immune disorders, and periodontal disease, the interstitial fluid and lymph system are sites where disease mechanisms may arise or develop.
See also
* Extracellular matrix
References
{{reflist, 30em
Anatomy
Extracellular matrix
Matrices (biology)
Tissues (biology)