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| A sperm cell attempts to penetrate an ovum coat to fertilize it. An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. For soil improvement see Fertilization (soil. | |
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| Diagram of a human spermatozoon | |
| MeSH | Spermatozoa |
A spermatozoon or spermatozoan (pl. Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books spermatozoa), from the ancient Greek σπέρμα (seed) and ζῷον (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. The Ancient Greek language is the historical stage in the development of the Hellenic language family spanning the Archaic (c The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells. "Haplo" redirects here For the fictional character see The Death Gate Cycle. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete It joins an ovum to form a zygote. For soil improvement see Fertilization (soil. An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo. An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular
Sperm cells contribute half of the genetic information to the diploid offspring. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance "Haplo" redirects here For the fictional character see The Death Gate Cycle. In mammals, the sex of the offspring is determined by the sperm cells: a spermatozoon bearing a Y chromosome will lead to a male (XY) offspring, while one bearing an X chromosome will lead to a female (XX) offspring (the ovum always provides an X chromosome). An organism's sex is defined by the gametes it produces males produce male gametes (spermatozoa or Sperm) while females produce female gametes (ova or Egg cells; individual A chromosome is an organized structure of DNA and Protein that is found in cells. Male (♂ refers to the sex of an organism or part of an organism which produces small mobile Gametes called spermatozoa. Female (♀ is the Sex of an Organism, or a part of an organism which produces ova (egg cells An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. Sperm cells were first observed by a student of Anton van Leeuwenhoek in 1677. Antonie Philips van Leeuwenhoek (October 24 1632 &ndash August 30 1723 was a Dutch tradesman and Scientist from Delft, the Netherlands [1]
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Mammalian spermatozoan structure, function, and size
Humans
The human sperm cell is the reproductive cell in males. Sperm cells come in two types; "male" and "female. " Sperm cells that give rise to female (XX) offspring after fertilization differ in that they carry an X chromosome, while sperm cells that give rise to male (XY) offspring carry a Y chromosome. The "female" sperm cell also differs phenotypically in that it has a larger head in comparison to the "male" sperm cell.
In male humans, sperm cells consists of a head 5 µm by 3 µm and a tail 50 µm long. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre The Reynolds number associated with spermatozoa is in the order of 1×10-2, so it is known that the spermatozoa exhibit non-turbulent flow. In Fluid mechanics and Heat transfer, the Reynolds number \mathrm{Re} is a Dimensionless number that gives a measure of the Ratio In Fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic Stochastic property changes The tail flagellates, which propels the sperm cell (at about 1-3 mm/minute in humans) by whipping in an elliptical cone. Flagellates are cells with one or more whip-like organelles called flagella. [2]. Semen has an alkaline nature, and they do not reach full motility (hypermotility) until they reach the vagina where the alkaline pH is neutralized by acidic vaginal fluids. Physiological aspects Internal and external fertilization Depending on the Species, spermatozoa can fertilize The vagina (from Latin, literally " Sheath " or " Scabbard " is a fibromuscular tubular tract leading from the Uterus This gradual process takes 20-30 minutes. In this time, fibrinogen from the seminal vesicles forms a clot, securing and protecting the sperm. Fibrin (also called Factor Ia) is a Protein involved in the clotting of blood The seminal vesicles ( glandulae vesiculosae) are a pair of simple tubular glands posteroinferior to the Urinary bladder of males Just as they become hypermotile, fibrinolysin from the prostate dissolves the clot, allowing the sperm to progress optimally. Fibrinolysin is an enzyme derived from plasma of Bovine origin or extracted from cultures of certain Bacteria. The prostate (from Greek προστάτης - prostates, literally "one who stands before" "protector" "guardian" is a
The spermatozoon is characterized by a minimum of cytoplasm and the most densely packed DNA known in eukaryotes. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. Compared to mitotic chromosomes in somatic cells, sperm DNA is at least sixfold more highly condensed. Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei Somatic cells are any cells forming the body of an organism as opposed to Germline cells [3]
During fertilization, the sperm's mitochondria are destroyed by the egg cell, and this means only the mother is able to provide the baby's mitochondria and mitochondrial DNA, which have an important application in tracing maternal ancestry. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Mitochondrial DNA ( mtDNA) is the DNA located in Organelles called mitochondria. An ancestor is a Parent or ( recursively) the parent of an ancestor (i However it has been recently discovered that mitochondrial DNA can be recombinant [4].
Avoidance of immune system response
Glycoprotein molecules on the surface of sperm cells are recognised by all human immune systems, and interpreted as a signal that the cell should not be rejected. Not to be confused with Peptidoglycan. Glycoproteins are proteins that contain Oligosaccharide chains ( Glycans) covalently attached The male immune system might otherwise attack sperm whilst in the testes, and the female immune system would attack sperm in the reproductive tract. The reproductive system is a system of organs within an Organism which work together for the purpose of Reproduction. The specific glycoproteins coating sperm cells are also utilized by some cancerous and bacterial cells, some parasitic worms, and HIV-infected white blood cells, in order to avoid an immune response from the host organism. In Biology, a host is an organism that harbors a Virus or Parasite, or a mutual or Commensal Symbiont, typically providing nourishment [5]
The blood-testis barrier, maintained by the tight junctions between the sertolli cells of the seminiferous tubules, prevents communication between the forming spermatozoa and the blood vessels within the interstitial space. This gives the forming spermatozoa an immunological advantage and thus prevents them from eliciting an immune response. The blood-testis barrier is also imporant in preventing toxic substances from disrupting spermatogenesis.
Spermatozoa in other organisms
- See also: Sperm
Animals
Fertilization relies on spermatozoa for most sexually reproductive animals. The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells.
The fruit fly[3] has the largest known spermatozoon relative to its size. Drosophila melanogaster produces sperm that can be up to 1. Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order 8 mm in size, which is longer than the adult fly. The incredibly long tail is thought to block other sperm from entering the egg. The entire sperm, tail included, gets incorporated into the oocyte cytoplasm. An oocyte, ovocyte, or rarely ocyte, is a female Gametocyte or Germ cell involved in reproduction. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. [6]
Sea urchins such as Arbacia punctulata—are the workhorses of sperm research, because they spawn large numbers of sperm into the sea, making them well-suited as model organisms for research experiments. Sea urchins are small globular spiny sea cat animals composing most of class Echinoidea.
Plants, algae and fungi
The gametophytes of bryophytes, ferns and some gymnosperms produce motile sperm cells, contrary to pollen grains employed in most gymnosperms and all angiosperms. In Plants and Algae that undergo Alternation of generations, a gametophyte is the multicellular structure or phase that is Haploid, containing Bryophytes are all Embryophytes ('land Plants) that are non-vascular: they have tissues and enclosed reproductive systems but they lack Vascular tissue A fern is any one of a group of about 20000 Species of Plants classified in the phylum or division Pteridophyta, also known as Filicophyta Gymnosperm (Gymnospermae are a group of Spermatophyte seed-bearing Plants with Ovules on the edge or blade of an open Sporophyll, which are The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells. Pollen is a fine to coarse powder consisting of microgametophytes ( pollen grains) which produce the male Gametes (sperm cells of The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group This renders sexual reproduction in the absence of water impossible, since water is a necessary medium for sperm and egg to meet. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Algae and lower plant sperm cells are often multi-flagellated (see image) and thus morphologically different from animal spermatozoa.
Some algae and fungi produce non-motile sperm cells, called spermatia. In higher plants and some algae and fungi, fertilization involves the migration of the sperm nucleus through a fertilization tube (e. g. pollen tube in higher plants) to reach the egg cell. The pollen tube of most Seed plants acts as a conduit to transport sperm cells from the Pollen grain, either from the stigma (in Flowering plants
Spermatozoa production in mammals
Spermatozoa are produced in the seminiferous tubules of the testes in a process called spermatogenesis. Spermatogenesis is the process by which male Spermatogonia develop into mature Spermatozoa. Seminiferous tubules are located in the Testicles and are the specific location of Meiosis, and the subsequent creation of gametes, namely Spermatozoa The testicle (from Latin testiculus, diminutive of testis, meaning "witness" virility plural testes) is the male Round cells called spermatogonia divide and differentiate eventually to become spermatozoa. A spermatogonium (plural spermatogonia) is an intermediary male Gametogonium (a kind of Germ cell) in the production of Spermatozoa. During copulation the cloaca or vagina gets inseminated, and then the spermatozoa move through chemotaxis to the ovum inside a Fallopian tube or the uterus. Sexual intercourse, in its biological sense is the act in which the male reproductive organ (in humans and other higher animals enters the female reproductive tract In zoological anatomy a cloaca is the posterior opening that serves as the only such opening for the intestinal and urinary tracts of certain animal species The vagina (from Latin, literally " Sheath " or " Scabbard " is a fibromuscular tubular tract leading from the Uterus Insemination is the introduction of sperm into the female Uterus of a Mammal or the Oviduct of an Oviparous (egg-laying animal during Chemotaxis, a kind of Taxis, is the phenomenon in which bodily cells bacteria, and other single-cell or Multicellular organisms direct their movements The Fallopian tubes, also known as oviducts, uterine tubes, and salpinges ( singular salpinx) are two very fine tubes lined with ciliated The uterus (from the Latin word for womb) is the major Female reproductive organ of most Mammals including Humans One end the
Spermatozoa Activation
Mammalian sperm cells become even more active when they approach an egg cell in a process called sperm activation. Sea urchins are small globular spiny sea cat animals composing most of class Echinoidea. Sperm activation has been shown to be caused by calcium ionophores in vitro, progesterone released by nearby cumulus cells and binding to ZP3 of the zona pellucida.
The intiial change is called "hyperactivation", which causes a change in spermatozoa motility. They swim faster and their tail movements become more forceful and erratic.
A recent discovery links hyperactivation to a sudden influx of calcium ion into the tails. The whip-like tail (flagellum) of the sperm is studded with ion channels formed by proteins called CatSper. Ion channels are pore-forming Proteins that help establish and control the small Voltage Gradient across the Plasma membrane of all living Cation channels of sperm: This small family of Ion channels normally referred to as Catsper channels or CatSper, is related to the Two-pore channels These channels are selective, allowing only calcium ion to pass. The opening of CatSper channels is responsible for the influx of calcium. The sudden rise in calcium levels causes the flagellum to form deeper bends, propelling the sperm more forcefully through the viscous environment. Sperm hyperactivity is necessary for breaking through two physical barriers that protect the egg from fertilization.
The second process in sperm activation is the acrosome reaction. During Fertilization, the acrosome reaction is the reaction which occurs in the Acrosome of the Sperm as it approaches the egg. This involves releasing hyaluronidase to digest cumulus cells surrounding the oocyte and exposing acorsin attached to the inner membrane of the sperm. The hyaluronidases ( are a family of Enzymes that degrade Hyaluronic acid. The cumulus cells are embedded in a gel-like substance made primarily of hyaluronic acid, and developed in the ovary with the egg and support it as it grows.
Acrosin digests the zona pellucida and membrane of the oocyte. Part of the sperm's cell membrane then fuses with the egg cell's membrane, and the contents of the head sink into the egg. For soil improvement see Fertilization (soil. ZP3, one of the proteins that make up the zona pellucida, binds to a partner molecule on the sperm. This lock-and-key type mechanism is species-specific and prevents the sperm and egg of different species from fusing. There is some evidence that this binding is what triggers the acrosome to release the enzymes that allow the sperm to fuse with the egg. In spermatozoa (also known as sperm/sperm cell of many animals the Acrosome is an Organelle that develops over the anterior half of the sperm's head
Upon penetration, the oocyte is said to have become activated. Ovum activation is the events which occur after Fertilisation. It undergoes its secondary meiotic division, and the two haploid nuclei (paternal and maternal) fuse to form a zygote. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" In order to prevent polyspermy and minimise the possibility of producing a triploid zygote, several changes to the egg's cell membranes renders them impenetrable shortly after the first sperm enters the egg. In biology polyspermy describes an egg that has been fertilized by more than one sperm. Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes.
References
- ^ Timeline: Assisted reproduction and birth control. Retrieved on 2006-04-06. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 46 BC - Julius Caesar defeats Caecilius Metellus Scipio and Marcus Porcius Cato in the Battle of Thapsus
- ^ Sumio Ishijima, Shigeru Oshio, Hideo Mohri, "Flagellar movement of human spermatozoa", Gamete research, 1986, vol. 13, no3, pp. 185-197 (27 ref. ) [1]
- ^ Ward WS, Coffey DS (1991). "DNA packaging and organization in mammalian spermatozoa: comparison with somatic cells". Biol. Reprod. 44 (4): 569–74. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 2043729.
- ^ Marilena D'Aurelio et al. , "'Heterologous mitochondrial DNA recombination in human cells'", Human Molecular Genetics 2004 13(24):3171-3179; doi:10. 1093/hmg/ddh326 [2]
- ^ "Sperm clue to 'disease immunity'", BBC News, 2007-12-17. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 546 - Gothic War (535–554: The Ostrogoths of King Totila
- ^ Gilbert, Scott F. , Developmental Biology, Eighth Edition. 2006. Sinauer Associates, pp. 254
External links
- The Handbook of Andrology
- Sperm hyperactivity
- Slower conception 'leads to boys'
- Photos of sperm under a microscope
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