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Spinnbarkeit (English:spinnability), also known as fibrosity, is a biomedical rheology term which refers to the stringy or stretchy property found to varying degrees in mucus, saliva, albumen and similar viscoelastic fluids. The term is used especially with reference to cervical mucus at the time just prior to or during ovulation,[1] and to sputum, particularly in cases of cystic fibrosis.[2]

Under the influence of estrogens, cervical mucus becomes abundant, clear, and stretchable, and somewhat like egg white. The stretchability of the mucus is described by its spinnbarkeit, from the German word for the ability to be spun. Only such mucus appears to be able to be penetrated by sperm. After ovulation, the character of cervical mucus changes, and under the influence of progesterone it becomes thick, scant, and tacky. Sperm typically cannot penetrate it.

Saliva does not always exhibit spinnbarkeit, but it can under certain circumstances. The thickness and spinnbarkeit of nasal mucus are factors in whether or not the nose seems to be blocked.

Mucociliary transport depends on the interaction of fibrous mucus with beating cilia.[3]


  1. ^ Clift AF (November 1945). "Observations on Certain Rheological Properties of Human Cervical Secretion". Proc R Soc Med. 39 (1): 1–9. PMC 2181791. PMID 19993188.
  2. ^ Lai SK, Wang YY, Wirtz D, Hanes J (2009-02-27). "Micro- and macrorheology of mucus". Adv Drug Deliv Rev. 61 (2): 86–100. doi:10.1016/j.addr.2008.09.012. PMC 2736374. PMID 19166889.
  3. ^ Trindade SH; de Mello JF Jr; Mion Ode G; Lorenzi-Filho G; Macchione M; Guimarães ET; Saldiva PH. (Sep–Oct 2007). "Methods for studying mucociliary transport". Braz J Otorhinolaryngol. 73 (5): 704–12. PMID 18094814.