Hydrodynamic propulsion of human sperm

Abstract

The detailed fluid mechanics of sperm propulsion are fundamental to our understanding of reproduction. In this paper, we aim to model a human sperm swimming in a microscope slide chamber. We model the sperm itself by a distribution of regularized stokeslets over an ellipsoidal sperm head and along an infinitesimally thin flagellum. The slide chamber walls are modelled as parallel plates, also discretized by a distribution of regularized stokeslets. The sperm flagellar motion, used in our model, is obtained by digital microscopy of human sperm swimming in slide chambers. We compare the results of our simulation with previous numerical studies of flagellar propulsion, and compare our computations of sperm kinematics with those of the actual sperm measured by digital microscopy. We find that there is an excellent quantitative match of transverse and angular velocities between our simulations and experimental measurements of sperm. We also find a good qualitative match of longitudinal velocities and computed tracks with those measured in our experiment. Our computations of average sperm power consumption fall within the range obtained by other authors. We use the hydrodynamic model, and a prototype flagellar motion derived from experiment, as a predictive tool, and investigate how sperm kinematics are affected by changes to head morphology, as human sperm have large variability in head size and shape. Results are shown which indicate the increase in predicted straight-line velocity of the sperm as the head width is reduced and the increase in lateral movement as the head length is reduced. Predicted power consumption, however, shows a minimum close to the normal head aspect ratio.

Sperm competition differentially affects swimming velocity and size of spermatozoa from closely related muroid rodents: head first

“…Changes in head dimensions may affect hydrodynamic resistance, therefore resulting in a more hydrodynamically efficient sperm design (Malo et al 2006, Gillies et al 2009). Furthermore, the increase in sperm HA is associated with the appearance of a hook.…”

“…Modifications in the dimensions of the sperm head may also lead to an increase in head elongation (i.e. increase in HL/HW ratio) that could reduce drag and lead to a more efficient propulsion (Malo et al 2006, Gillies et al 2009, Tourmente et al 2011a. Sperm heads may also bear modifications either in the apical or in the basal region, particularly in rodents, in which hooks or post-nuclear appendices have been described, and which may be related to more efficient swimming (reviewed in Roldan et al (1992)).…”

Effect of viscosity on motion characteristics of bovine sperm

“…In the present study, we focused on the effect of the viscosity of the oviductal mucus on the sperm motility. Many researchers have conducted rigorous studies on the motion characteristics of sperm from theoretical [1]- [4], experimental, [5]- [12] and numerical [13]- [16] standpoints. However, there are few studies that focus on the effect of the surrounding environment of the sperm, i.e., the fluid characteristics of the oviduct, on the sperm motility.…”

Bistability and metabistability scenario in the dynamics of an ellipsoidal particle in a sheared viscoelastic fluid

“…For instance, elongated rigid particles are added into fluids to confer special final properties to the composite material [1][2][3][4]. Also, shape anisotropy of bioparticles such as bacteria [5][6][7], microswimmers [8], sperm cells [9], platelets [10] and hetero-cell aggregates [11] imparts peculiar dynamical properties to the overall flowing materials.…”