Connective tissue

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Connective tissue
Section of epididymis. Connective tissue (blue) is seen supporting the epithelium (purple)
Identifiers
MeSHD003238
FMA96404
Anatomical terminology

Connective tissue is one of the four primary types of

leukocytes
.

The term "connective tissue" (in German, Bindegewebe) was introduced in 1830 by Johannes Peter Müller. The tissue was already recognized as a distinct class in the 18th century.[4][5]

Types

Connective tissue can be broadly classified into connective tissue proper, and special connective tissue.[6][7]

Connective tissue proper

Connective tissue proper consists of loose connective tissue (including reticular connective tissue and adipose tissue) and dense connective tissue (subdivided into dense regular and dense irregular connective tissues.)[8] Loose and dense connective tissue are distinguished by the ratio of ground substance to fibrous tissue. Loose connective tissue has much more ground substance and a relative lack of fibrous tissue, while the reverse is true of dense connective tissue. Dense regular connective tissue, found in structures such as tendons and ligaments, is characterized by collagen fibers arranged in an orderly parallel fashion, giving it tensile strength in one direction. Dense irregular connective tissue provides strength in multiple directions by its dense bundles of fibers arranged in all directions.[citation needed]

Special connective tissue

Special connective tissue consists of

muscular tissue. New vascularised connective tissue that forms in the process of wound healing is termed granulation tissue.[12] All of the special connective tissue types have been included as a subset of fascia in the fascial system, with blood and lymph classed as liquid fascia.[13][14]

Bone and cartilage can be further classified as supportive connective tissue. Blood and lymph can also be categorized as fluid connective tissue,[2][15][16] and liquid fascia.[13]

Membranes

epithelial tissue. Connective tissue membranes include the meninges (the three membranes covering the brain and spinal cord) and synovial membranes that line joint cavities.[17] Mucous membranes and serous membranes are epithelial with an underlying layer of loose connective tissue.[17]

Fibrous types

Fiber types found in the

reticular fibers.[18]
Ground substance is a clear, colorless, and viscous fluid containing glycosaminoglycans and proteoglycans allowing fixation of Collagen fibers in intercellular spaces. Examples of non-fibrous connective tissue include adipose tissue (fat) and blood. Adipose tissue gives "mechanical cushioning" to the body, among other functions.[19][20] Although there is no dense collagen network in adipose tissue, groups of adipose cells are kept together by collagen fibers and collagen sheets in order to keep fat tissue under compression in place (for example, the sole of the foot). Both the ground substance and proteins (fibers) create the matrix for connective tissue.

Type I collagen is present in many forms of connective tissue, and makes up about 25% of the total protein content of the mammalian body.[21]

Types of fibers
Tissue Purpose Components Location
Collagen fibers
 Bind bones and other tissues to each other Alpha polypeptide chains tendon, ligament, skin, cornea, cartilage, bone, blood vessels, gut, and intervertebral disc.
Elastic fibers Allow organs like arteries and lungs to recoil Elastic microfibril and elastin extracellular matrix
Reticular fibers Form a scaffolding for other cells Type III collagen liver, bone marrow, and lymphatic organs

Function

See also:
Epithelial-mesenchymal transition
inherited connective tissue defect
.

Connective tissue has a wide variety of functions that depend on the types of cells and the different classes of fibers involved.

aponeuroses, and is also found in highly specialized organs such as the cornea.[22]: 161  Elastic fibers, made from elastin and fibrillin, also provide resistance to stretch forces.[22]: 171  They are found in the walls of large blood vessels and in certain ligaments, particularly in the ligamenta flava.[22]
: 173 

In

stroma—or structural support—for the parenchyma (that is, the bulk of functional substance) of the organ.[22]
: 171 

Mesenchyme is a type of connective tissue found in developing organs of embryos that is capable of differentiation into all types of mature connective tissue.[23] Another type of relatively undifferentiated connective tissue is the mucous connective tissue known as Wharton's jelly, found inside the umbilical cord.[22]: 160  This tissue is no longer present after birth, leaving only scattered mesenchymal cells throughout the body.[24]

Various types of specialized tissues and cells are classified under the spectrum of connective tissue, and are as diverse as brown and white adipose tissue, blood, cartilage and bone.[22]: 158  Cells of the immune system—such as macrophages, mast cells, plasma cells, and eosinophils—are found scattered in loose connective tissue, providing the ground for starting inflammatory and immune responses upon the detection of antigens.[22]: 161 

Clinical significance

Main article: Connective tissue disease

There are many types of connective tissue disorders, such as:

See also

Notes and references

  1. ^ Biga, Lindsay M.; Dawson, Sierra; Harwell, Amy (26 September 2019). "4.1 Types of Tissues". Retrieved 30 July 2022.
  2. ^ a b c d Biga, Lindsay M.; Dawson, Sierra; Harwell, Amy; Hopkins, Robin; Kaufmann, Joel; LeMaster, Mike; Matern, Philip; Morrison-Graham, Katie; Quick, Devon (2019), "4.3 Connective Tissue Supports and Protects", Anatomy & Physiology, OpenStax/Oregon State University, retrieved 16 April 2021
  3. ^ "5.3.4: Fluid Tissues". Biology LibreTexts. 21 May 2021. Retrieved 2 August 2022.
  4. ^ Mathews, M. B. (1975). Connective Tissue, Macromolecular Structure Evolution. Springer-Verlag, Berlin and New York. link.
  5. S2CID 22765625
    .
  6. ^ Shostak, Stanley. "Connective Tissues". Retrieved 9 December 2012.
  7. ISBN 978-1582557243
    . Retrieved 11 May 2011.
  8. ^ Potter, Hugh. "The Connective Tissues". Archived from the original on 31 October 2012. Retrieved 9 December 2012.
  9. ^ Caceci, Thomas. "Connective Tisues". Archived from the original on 6 January 2013. Retrieved 9 December 2012.
  10. ^ King, David. "Histology Intro". Retrieved 9 December 2012.
  11. ^ "Medical Definition of FIBROAREOLAR". Merriam-Webster. Retrieved 11 October 2018.
  12. ^ "Granulation Tissue Definition". Memidex. Archived from the original on 16 November 2018. Retrieved 7 May 2016.
  13. ^
    PMID 29630284
    . Retrieved 3 August 2022.
  14. PMID 31183880
    .
  15. ^ "Supporting Connective Tissue | Human Anatomy and Physiology Lab (BSB 141)". courses.lumenlearning.com. Retrieved 16 April 2021.
  16. ^ Karki, Gaurab (23 February 2018). "Fluid or liquid connective tissue: blood and lymph". Online Biology Notes. Retrieved 16 April 2021.
  17. ^ a b "Membranes | SEER Training". training.seer.cancer.gov. Retrieved 3 August 2022.
  18. PMID 12164335
    .
  19. S2CID 3294995
    .
  20. PMID 17270403
    .
  21. PMID 11704682
    .
  22. ^
    ISBN 978-0781772006
    .
  23. ISBN 978-0702047473
    .
  24. ISBN 978-1-947172-04-3
    .

External links

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