The Mathematical Institute, University of Oxford, Eprints Archive

Mammalian Sperm Motility: Observation and Theory

Gaffney, E. A. and Gadelha, H and Smith, D J and Blake, J R and Kirkman-Brown, J C (2011) Mammalian Sperm Motility: Observation and Theory. Annual Review of Fluid Mechanics, 43 (2). pp. 501-528.

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Abstract


Mammalian spermatozoa motility is a subject of growing importance because of rising human infertility and the possibility of improving animal breeding. We highlight opportunities for fluid and continuum dynamics to provide novel insights concerning the mechanics of these specialized cells, especially during their remarkable journey to the egg. The biological structure of the motile sperm appendage, the flagellum, is described and placed in the context of the mechanics underlying the migration of mammalian sperm through the numerous environments of the female reproductive tract. This process demands certain specific changes to flagellar movement and motility for which further mechanical insight would be valuable, although this requires improved modeling capabilities, particularly to increase our understanding of sperm progression in vivo. We summarize current theoretical studies, highlighting the synergistic combination of imaging and theory in exploring sperm motility, and discuss the challenges for future observational and theoretical studies in understanding the underlying mechanics.
Acronyms and Definitions
Acrosome: the cap of the sperm head containing enzymes allowing penetration of the zona pellucida via the acrosome reaction
Adenosine triphosphate (ATP): the currency unit of chemical energy transfer in living cells
Axoneme: a phylogenetically conserved structure within the eukaryotic flagellum consisting of a ring of nine microtubule doublets and a central pair, frequently referred to as 9 + 2
Bending moment density: the moment per unit length associated with flagellar bending; it can be divided into a hydrodynamic moment, an elastic moment (from the flagellar bending stiffness), an active moment (generated by dyneins exerting forces between adjacent microtubule doublets), and a passive moment resisting shear
Capacitation: the physiological state of a sperm required for fertilization, which is accompanied by the motility patterns associated with hyperactivation, characterized in saline by high-amplitude asymmetric beating
Central pair: a pair of microtubules along the length of the axoneme, symmetrically and slightly offset from the axoneme centerline
Cumulus oophorus: the outer vestment of the mammalian egg consisting of hundreds of cells radiating out from the egg embedded within a non-Newtonian hyaluronic acid gel
Dynein: a molecular motor within the axoneme, attached between adjacent microtubule doublets, that exerts a shearing force to induce axonemal bending
Flagellum: a motile cellular appendage that drives the swimming of sperm and other cells; this article focuses on the eukaryotic flagellum
Microtubule doublet: a pair of proteinaceous filament structures running the length of the axoneme; dyneins drive their bending, which induces flagellar motion
Mid-piece: the region of a sperm flagellum with a mitochondrial sheath, where ATP is generated
Oocyte: the egg
Outer dense fibers and fibrous sheath: accessory structures reinforcing the mammalian sperm flagellum; the combined axoneme and accessory structures are referred to as 9+9+2
Resistive-force theory: an approximation for the local drag of a slender filament element in Stokes flow (or a viscoelastic generalization thereof)
Rheotaxis: directed motility in response to the influence of fluid flow
Shear: in the context of the flagellum, the relative movement of adjacent microtubule doublets
Slender-body theory: an improved approximation for the local drag on a slender filament element in Stokes flow (or a viscoelastic generalization thereof)
Zona pellucida: a tough glycoprotein coat between the human egg and the cumulus oophorus, which a sperm must penetrate for successful fertilization

Item Type:Article
Uncontrolled Keywords:flagellum microswimmer fluid-filament interactions slender-body theory
Subjects:A - C > Biology and other natural sciences
Research Groups:Centre for Mathematical Biology
ID Code:1355
Deposited By:Eamonn Gaffney
Deposited On:04 Aug 2011 14:26
Last Modified:04 Aug 2011 14:26

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