Collagenum
Collagenum est proteinum praecipuum textus conexivi animalium, quo massa corporis mammalium maxime abundat (26% totius massae proteini; in homine c. 6% ponderis corporis). Collagenum ubique invenitur, sicut in musculis, cartilagine, vasis sanguineis, cornea oculi, disco intervertebrali, intestinis. Collageni species duodetriginta sunt, quae ordine aminoacidorum paululum inter se differunt et in textibus unius cuiusque speciei propriis inveniuntur. Plurimum collageni speciei I in osse sed etiam in tendinibus, ligamentis, dermide, cuti est. Collageni speciei II plurimum in cartilagine, speciei III autem in textu adiposo reperitur.

Fibrae collageni nascuntur ex procollageno, quod ex cellulis textus conexivi, praesertim fibroblastis, exsistit. Quae enim cellulae procollagenum in spatium externum excernunt una cum enzymis, quae ibi procollagenum in tropocollagenum findunt. 
Fibrae autem tropocollageni aliae iuxta alias positae natura inclinant mutuo complexu implicari ita ut covalentia inter fibras vincula efficiantur.

Bibliographia 
 Brodsky B.;Ramshaw J. A. (1997) The Collagen Triple-Helix Structure. Matrix Biololy 15: 545-554.
 Exposito, Jean-Yves ; Cluzel, Caroline ; Garrone, Robert ; Lethias, Claire (2002) Evolution of collagens, The Anatomical Record 268 (3): 302–16. 
 Saad, Mohamed (1994) Low resolution structure and packing investigations of collagen crystalline domains in tendon using Synchrotron Radiation X-rays, Structure factors determination, evaluation of Isomorphous Replacement methods and other modeling. Dissertatio doctoralis, Université Joseph Fourier Grenoble 1.

Cytologia
Textus conexivi
Matrix extracellularis