Spermalso called spermatozoon, plural spermatozoamale reproductive cellproduced by most animals. With the exception of nematode worms, decapods e. In higher vertebrates, especially mammals, sperm are produced in the testes.
When you see a doctor because you're having trouble getting your partner pregnant, he or she will try to determine the underlying cause. Even if your doctor thinks low sperm count is the problem, it is recommended that your partner be evaluated to rule out potential contributing factors and determine if assisted reproductive techniques may be required. This includes examination of your genitals and asking questions about any inherited conditions, chronic health problems, illnesses, injuries or surgeries that could affect fertility.
In the context of sexual reproduction, natural selection is generally thought of as a pre-copulation mechanism. We are drawn to features of the human body that tell us our partner is healthy and will provide us a fighting opportunity to carry on our genetic lineage. But a new article appearing in the February issue of Current Directions in Psychological Science suggests that the human male has evolved mechanisms to pass on his genes during post-copulation as well, a phenomenon dubbed "sperm competition.
Sperm cells are gametes sex cells that are produced in the testicular organ gonad of male human beings and animals. Like the female gamete Oocytesperm cells carry a total of 23 chromosomes that are a result of a process known as meiosis. In both animals and human beings, among many other organisms, these cells are involved in the sexual mode of reproduction which involves the interaction of male and female gametes. The general morphology of sperm cells consists of the following parts:.
By Rachel Nowak, Melbourne. Men who view pornographic images of two men and a woman produce better-quality sperm than men viewing pornographic images of just women, an Australian study reveals. In the study, zoologists Leigh Simmons and Sarah Kilgallon of the University of Western Australia in Perth asked 52 heterosexual men aged between 18 and 35 years to ejaculate into a container after viewing the two types of image.
Sperm cells are the target of strong sexual selection that may drive changes in sperm structure and function to maximize fertilisation success. Sperm evolution is regarded to be one of the major consequences of sperm competition in polyandrous species, however it can also be driven by adaptation to the environmental conditions at the site of fertilization. Strong stabilizing selection limits intra-specific variation, and therefore polymorphism, among fertile sperm eusperm.
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg  during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a female's chance to produce more viable offspring.
Suarez, A. At coitus, human sperm are deposited into the anterior vagina, where, to avoid vaginal acid and immune responses, they quickly contact cervical mucus and enter the cervix. Cervical mucus filters out sperm with poor morphology and motility and as such only a minority of ejaculated sperm actually enter the cervix. In the uterus, muscular contractions may enhance passage of sperm through the uterine cavity.
For reproduction, most fish species adopt external fertilization: their spermatozoa are delivered in the external milieu marine- or freshwater that represents both a drastic environment and a source of signals that control the motility function. This chapter is an updated overview of the signaling pathways going from external signals such as osmolarity and ionic concentration and their membrane reception to their transduction through the membrane and their final reception at the flagellar axoneme level. Additional factors such as energy management will be addressed as they constitute a limiting factor of the motility period of fish spermatozoa.