Editing Collagen (section)

==In humans==
===Cardiac===
The collagenous [[cardiac skeleton]], which includes the four [[heart valve]] rings, is histologically, elastically and uniquely bound to cardiac muscle. The cardiac skeleton also includes the separating [[cardiac septa|septa of the heart chambers]] – the [[interventricular septum]] and the [[atrioventricular septum]]. Collagen contribution to the measure of [[Cardiac stress test|cardiac performance]] summarily represents a continuous torsional force opposed to the [[fluid mechanics]] of blood pressure emitted from the heart. The collagenous structure that divides the upper chambers of the heart from the lower chambers is an impermeable membrane that excludes both blood and electrical impulses through typical physiological means. With support from collagen, [[atrial fibrillation]] never deteriorates to [[ventricular fibrillation]]. Collagen is layered in variable densities with smooth muscle mass. The mass, distribution, age, and density of collagen all contribute to the [[compliance (physiology)|compliance]] required to move blood back and forth. Individual cardiac valvular leaflets are folded into shape by specialized collagen under variable [[pressure]]. Gradual [[calcium]] deposition within collagen occurs as a natural function of aging. Calcified points within collagen matrices show contrast in a moving display of blood and muscle, enabling methods of [[cardiac imaging]] technology to arrive at ratios essentially stating blood in ([[cardiac input]]) and blood out ([[cardiac output]]). Pathology of the collagen underpinning of the heart is understood within the category of [[connective tissue disease]].{{Citation needed|date=May 2021}}

===Bone grafts===
As the skeleton forms the structure of the body, it is vital that it maintains its strength, even after breaks and injuries. Collagen is used in bone grafting because its triple-helix structure makes it a very strong molecule. It is ideal for use in bones, as it does not compromise the structural integrity of the skeleton. The triple helical structure prevents collagen from being broken down by enzymes, it enables adhesiveness of cells and it is important for the proper assembly of the extracellular matrix.<ref>{{cite journal| vauthors = Cunniffe G, O'Brien F |title=Collagen scaffolds for orthopedic regenerative medicine|journal=The Journal of the Minerals, Metals & Materials Society|year=2011|volume=63|issue=4|pages=66–73|doi=10.1007/s11837-011-0061-y|bibcode = 2011JOM....63d..66C |s2cid=136755815}}</ref>

===Tissue regeneration===
Collagen scaffolds are used in tissue regeneration, whether in sponges,<ref>{{cite journal | vauthors = Geiger M, Li RH, Friess W | title = Collagen sponges for bone regeneration with rhBMP-2 | journal = Advanced Drug Delivery Reviews | volume = 55 | issue = 12 | pages = 1613–1629 | date = November 2003 | pmid = 14623404 | doi = 10.1016/j.addr.2003.08.010 }}</ref> thin sheets,<ref>{{cite journal | vauthors = Bunyaratavej P, Wang HL | title = Collagen membranes: a review | journal = Journal of Periodontology | volume = 72 | issue = 2 | pages = 215–229 | date = February 2001 | pmid = 11288796 | doi = 10.1902/jop.2001.72.2.215 | hdl-access = free | hdl = 2027.42/141506 }}</ref> gels,<ref>{{cite journal | vauthors = Drury JL, Mooney DJ | title = Hydrogels for tissue engineering: scaffold design variables and applications | journal = Biomaterials | volume = 24 | issue = 24 | pages = 4337–4351 | date = November 2003 | pmid = 12922147 | doi = 10.1016/S0142-9612(03)00340-5 }}</ref> or fibers.<ref>{{cite journal | vauthors = Tonndorf R, Aibibu D, Cherif C | title = Collagen multifilament spinning | journal = Materials Science & Engineering. C, Materials for Biological Applications | volume = 106 | pages = 110105 | date = January 2020 | pmid = 31753356 | doi = 10.1016/j.msec.2019.110105 | s2cid = 202227968 }}</ref> Collagen has favorable properties for tissue regeneration, such as pore structure, permeability, hydrophilicity, and stability in vivo. Collagen scaffolds also support deposition of cells, such as [[osteoblasts]] and [[fibroblast]]s, and once inserted, facilitate growth to proceed normally.<ref name=Oliveira>{{cite journal | vauthors = Oliveira SM, Ringshia RA, Legeros RZ, Clark E, Yost MJ, Terracio L, Teixeira CC | title = An improved collagen scaffold for skeletal regeneration | journal = Journal of Biomedical Materials Research. Part A | volume = 94 | issue = 2 | pages = 371–379 | date = August 2010 | pmid = 20186736 | pmc = 2891373 | doi = 10.1002/jbm.a.32694 }}</ref>

===Reconstructive surgery===
Collagens are widely used in the construction of [[artificial skin]] substitutes used for managing severe [[burn (injury)|burns]] and wounds.<ref name="Singh">{{cite journal | vauthors = Singh O, Gupta SS, Soni M, Moses S, Shukla S, Mathur RK | title = Collagen dressing versus conventional dressings in burn and chronic wounds: a retrospective study | journal = Journal of Cutaneous and Aesthetic Surgery | volume = 4 | issue = 1 | pages = 12–16 | date = January 2011 | pmid = 21572675 | pmc = 3081477 | doi = 10.4103/0974-2077.79180 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Gould LJ | title = Topical Collagen-Based Biomaterials for Chronic Wounds: Rationale and Clinical Application | journal = Advances in Wound Care | volume = 5 | issue = 1 | pages = 19–31 | date = January 2016 | pmid = 26858912 | pmc = 4717516 | doi = 10.1089/wound.2014.0595 }}</ref> These collagens may be derived from cow, horse, pig, or even human sources; and are sometimes used in combination with [[silicone]]s, [[glycosaminoglycan]]s, fibroblasts, [[growth factor]]s and other substances.<ref>{{Cite web|title=Collagen and Rosehip Extract Sachet|url=http://alainapharma.com/Collagen%20+%20Rosehip%20Extract.html|url-status=live|access-date=31 May 2021|website=Alaina Pharma|archive-url=https://web.archive.org/web/20160704063720/http://alainapharma.com:80/Collagen%20+%20Rosehip%20Extract.html |archive-date=4 July 2016 }}</ref>

=== Wound healing ===
{{More citations needed section|date=April 2021}}
Collagen is one of the body's key natural resources and a component of skin tissue that can benefit all stages of [[wound healing]].<ref name="scr">{{cite journal | vauthors = Birbrair A, Zhang T, Files DC, Mannava S, Smith T, Wang ZM, Messi ML, Mintz A, Delbono O | title = Type-1 pericytes accumulate after tissue injury and produce collagen in an organ-dependent manner | journal = Stem Cell Research & Therapy | volume = 5 | issue = 6 | pages = 122 | date = November 2014 | pmid = 25376879 | pmc = 4445991 | doi = 10.1186/scrt512 | doi-access = free }}</ref> When collagen is made available to the wound bed, closure can occur. This avoids wound deterioration and procedures such as amputation.

Collagen is used as a natural wound dressing because it has properties that artificial wound dressings do not have. It resists bacteria, which is vitally important in wound dressing. As a burn dressing, collagen helps it heal fast by helping [[granulation tissue]] to grow over the burn.<ref name="Singh"/>

Throughout the four phases of wound healing, collagen performs the following functions:
* Guiding: [[collagen fibers]] guide fibroblasts because they migrate along a connective tissue matrix.
* [[Chemotaxis]]: collagen fibers have a large surface area which attracts fibrogenic cells which help healing.
* [[Nucleation]]: in the presence of certain neutral salt molecules, collagen can act as a nucleating agent causing formation of fibrillar structures.
* [[Antihemorrhagic|Hemostasis]]: Blood [[platelet]]s interact with the collagen to make a hemostatic plug.