Spermatozoon

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Spermatozoon

A sperm, from the ancient Greek

Ancient Greek

Ancient Greek is the historical stage in the development of the Greek language spanning across the Archaic Greece , Classical Greece , and Hellenistic civilization periods of ancient Greece and the classical antiquity....
word sp??µa (seed) and (living being) and more commonly known as a sperm
Sperm

The term sperm is derived from the Greek word sperma and refers to the male reproductive Cell . In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell....
cell
Cell

Cell may refer to:...
, is the haploid

Ploidy

Ploidy is the number of complete sets of non-homologous chromosomes in a biological cell. In humans, the somatic cells that comprise the body are diploid , but sex cells are haploid....
cell

Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
that is the male gamete

Gamete

A gamete is a Cell that fuses with another gamete during fertilization in organisms that sexual reproduction. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete?called an ovum ?and a male produces th...
. It joins an ovum

Ovum

An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization....
to form a zygote

Zygote

A zygote is a cell that is the result of fertilization. That is, two ploidy cells—usually an ovum from a female and a sperm cell from a male—merge into a single ploidy cell called the zygote ....
. A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo

Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
.

Sperm cells contribute half of the genetic information

Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
to the diploid offspring. In mammals, the sex

Sex

In biology, sex is a process of combining and mixing genetics traits, often resulting in the specialization of organisms into male and female types ....
of the offspring is determined by the sperm cell: a spermatozoon bearing a Y chromosome

Chromosome

A chromosome is an organized structure of DNA and protein that is found in Cell . A chromosome is a single piece of DNA that contains many genes, regulatory sequence and other genetic sequence....
will lead to a male

Malé

Mal? , population 104,403 , is the Capital , the largest city in terms of population, and the name of an island in the Maldives. It is located at the southern edge of North Male' Atoll Kaafu Atoll....
(XY) offspring, while one bearing an X chromosome will lead to a female

Female

Female is the sex of an organism, or a part of an organism, which produces mobile ovum . The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male....
(XX) offspring (the ovum

Ovum

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Encyclopedia

A sperm, from the ancient Greek

Ancient Greek

Ploidy

Ploidy is the number of complete sets of non-homologous chromosomes in a biological cell. In humans, the somatic cells that comprise the body are diploid , but sex cells are haploid....
cell

Cell (biology)

Gamete

Ovum

Zygote

Embryo

Gene

Sex

Chromosome

Malé

Female

Ovum

Anton van Leeuwenhoek

Antonie Philips van Leeuwenhoek was a Netherlands tradesman and scientist from Delft, the Netherlands. He is commonly known as "Fathers_of_scientific_fields", and considered to be the first microbiologist....
in 1677.

Mammalian spermatozoan structure, function, and size

Humans

The human sperm cell is the reproductive cell in males and will only survive in warm environments, once leaving the body the sperms survival is reduced and may cause the cell to die. 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.

In male humans, sperm cells consists of a head 5 µm

Micrometre

A micrometre or micron is one Micro- of a metre, or equivalently one thousandth of a millimetre. It is also commonly known as a micron....
by 3 µm and a tail 50 µm long. The Reynolds number

Reynolds number

In fluid mechanics and heat transfer, the Reynolds number is a dimensionless number that gives a measure of the ratio of inertial forces to viscosity forces and, consequently, it quantifies the relative importance of these two types of forces for given flow conditions....
associated with spermatozoa is in the order of 1, so it is known that the spermatozoa exhibit non-turbulent

Turbulence

In fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time....
flow. The tail flagellate

Flagellate

Flagellates are cell s with one or more whip-like organelles called flagellum. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla....
s, which propels the sperm cell (at about 1–3 mm/minute in humans) by whipping in an elliptical cone.. Semen

Semen

Semen is an organic fluid, also known as seminal fluid, that usually contains spermatozoon....
has an alkaline nature, and they do not reach full motility (hypermotility) until they reach the vagina

Vagina

The vagina is a fibromuscular cylinder tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles....
where the alkaline pH is neutralized by acidic vaginal fluids. This gradual process takes 20–30 minutes. In this time, fibrinogen from the seminal vesicles forms a clot, securing and protecting the sperm. Just as they become hypermotile, fibrinolysin

Fibrinolysin

Fibrinolysin is an enzyme derived from plasma of bovine origin or extracted from cultures of certain bacteria. It is used locally only and exclusively together with the enzyme desoxyribonuclease ....
from the prostate

Prostate

The prostate is a compound tubuloalveolar exocrine gland of the male mammalian reproductive system. Females do not have a prostate gland, although females do have tiny paraurethral Skene's glands connected to the distal third of the urethra in the prevaginal space that are homologous to the prostate....
dissolves the clot, allowing the sperm to progress optimally.

The spermatozoon is characterized by a minimum of cytoplasm

Cytoplasm

Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
chromosomes in somatic cell

Somatic cell

Somatic cells are any cell s forming the body of an organism, as opposed to germline cells. In mammals, germline cells are the spermatozoa and ova which fuse during fertilization to produce a cell called a zygote, from which the entire mammalian embryo develops....
s, sperm DNA is at least sixfold more highly condensed.

Avoidance of immune system response

Glycoprotein

Not to be confused with peptidoglycan or proteoglycan.Glycoproteins are proteins that contain oligosaccharide chains covalently attached to their Peptide side-chains....
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. 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 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

Host (biology)

In biology, a host is an organism that harbors a virus or parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter....
.

The blood-testis barrier

Blood-testis barrier

The blood-testis barrier is a physical barrier between the blood vessels and the seminiferous tubules of the animal testicle.The barrier is formed by tight connections between the Sertoli cells, which are sustentacular cells of the seminiferous tubules, and nourish the Spermatogonium....
, maintained by the tight junctions between the Sertoli cell

Sertoli cell

A Sertoli cell is a 'nurse' cell of the testicle which is part of a seminiferous tubule.It is activated by follicle-stimulating hormone, and has FSH-receptor on its membranes....
s of the seminiferous tubules, prevents communication between the forming spermatozoa and the blood vessels within the interstitial space

Interstitial space (biology)

In biology, the interstitial space, also called the tissue space, is the space that surrounds the cell s of a given tissue. It is filled with interstitial fluid....
. This gives the forming spermatozoa an immunological advantage and thus prevents them from eliciting an immune response. The blood-testis barrier is also important in preventing toxic substances from disrupting spermatogenesis.

Spermatozoa in other organisms

Animals

Fertilization relies on spermatozoa for most sexually reproductive animals.

The fruit fly

Fruit fly

Fruit fly may refer to:* Tephritidae, the family of large fruit flies.* Drosophilidae, the family of small fruit flies and vinegar flies, including:...
has the largest known spermatozoon relative to its size. Drosophila melanogaster

Drosophila melanogaster

Drosophila melanogaster is a two-winged insect that belongs to the Diptera, the Order of the Fly. The species is commonly known as the Drosophilidae or vinegar fly, and is one of the most commonly used model organisms in biology, including studies in genetics, physiology and Life history theory....
produces sperm that can be up to 1.8 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

Oocyte

An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in biological reproduction. In other words, it is an immature ovum, or ovum cell....
cytoplasm

Cytoplasm

The cytoplasm is the part of a Cell that is enclosed within the plasma membrane. In eukaryote cells the cytoplasm contains organelles, such as mitochondrion, that are filled with liquid kept separate from the rest of the cytoplasm by biological membranes....
.

The wood mouse Apodemus slvaticus possesses spermatozoa with falciform morphology. What makes these gametocytes even more unique is the presence of an apical hook on the sperm head. This hook is used to attach to the hooks or to the flagella of other spermatozoa. Aggregation is caused by these attachments and mobile trains result. These trains provide improved motility in the female reproductive tract and are a means by which fertilization is promoted.

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.

Plants, algae and fungi

The gametophyte

Gametophyte

In plants and algae that undergo alternation of generations, a gametophyte is the multicellular structure, or phase, that is haploid, containing a single set of chromosomes:...
s of bryophyte

Bryophyte

Bryophytes are all embryophytes that are non-vascular plant: they have tissues and enclosed reproductive systems, but they lack vascular tissue that circulates liquids....
s, fern

Fern

A fern is any one of a group of about 20,000 species of plants classified in the phylum or division Pteridophyta, also known as Filicophyta....
s and some gymnosperm

Gymnosperm

Gymnosperm is a group of spermatophyte seed-bearing plants with ovules on scales, which are usually arranged in cone-like structures. The other major group of seed-bearing plants, the angiosperms, [from the Greek, 'angion' - container] have ovules enclosed in a carpel, a sporophyll with fused margins....
s produce motile sperm

Sperm

The term sperm is derived from the Greek word sperma and refers to the male reproductive Cell . In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell....
cells, contrary to pollen

Pollen

Pollen is a fine to coarse powder consisting of Gametophyte , which produce the male gametes of spermatophyta. A hard coat covering the pollen grain protects the sperm cells during the process of their movement between the stamens of the flower to the pistil of the next flower....
grains employed in most gymnosperms and all angiosperms. This renders sexual reproduction in the absence of water

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
impossible, since water is a necessary medium for sperm and egg to meet. 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

Pollen tube

The pollen tube of most seed plants acts as a conduit to transport sperm cells from the pollen grain, either from the stigma to the ovules at the base of the pistil, or directly through ovule tissue in some gymnosperms ....
in higher plants) to reach the egg cell.

Spermatozoa production in mammals

Spermatozoa are produced in the seminiferous tubules of the testes in a process called spermatogenesis. Round cells called spermatogonia divide and differentiate eventually to become spermatozoa. During copulation the cloaca

Cloaca

In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the alimentary tract and urinary tract of certain animal species....
or vagina

Vagina

Insemination

Insemination is the introduction of spermatozoon into the female uterus of a mammal or the oviduct of an oviparous during copulation with another animal....
ed, and then the spermatozoa move through chemotaxis

Chemotaxis

Chemotaxis, a kind of taxis, is the phenomenon in which bodily cells, bacterium, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment....
to the ovum inside a Fallopian tube

Fallopian tube

The Fallopian tubes, named after Gabriel Fallopius , also known as oviducts, uterine tubes, and salpinges are two very fine tubes lined with cilia epithelia, leading from the ovaries of female mammals into the uterus....
or the uterus

Uterus

The uterus is a major female hormone-responsive reproductive sex organ of most mammals, including humans. It is within the uterus that the fetus develops during gestation....
.

Spermatozoa Activation

Mammalian sperm cells become even more active when they approach an egg cell in a process called sperm activation. Sperm activation has been shown to be caused by calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal, and is the fifth most abundant element by mass in the earth's Crust ....
ionophores in vitro, progesterone

Progesterone

Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species. Progesterone belongs to a class of hormones called progestogens, and is the major naturally occurring human progestogen....
released by nearby cumulus cells and binding to ZP3

ZP3

ZP3 is the receptor in the zona pellucida which binds with the acrosome of the sperm in the acrosome reaction.External links...
of the zona pellucida

Zona pellucida

The zona pellucida is a glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but not extraneous to it....
.

The initial 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 channel

Ion channel

Ion channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of all living cell s by allowing the flow of ions down their electrochemical gradient....
s formed by proteins called CatSper. 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

Acrosome reaction

File:Acrosome reaction diagram.svgDuring fertilization, sperm must first fuse and then penetrate the female egg in order to fertilize it. Fusing to the egg usually causes little problem whereas penetrating through the egg's hard shell can present more of a problem to the sperm....
. This involves releasing hyaluronidase

Hyaluronidase

The hyaluronidases are a family of enzymes that degrade hyaluronic acid.In humans, there are six associated genes, including HYAL1, HYAL2 and HYAL3....
to digest cumulus cells surrounding the oocyte and exposing acrosin

Acrosin

Acrosin is a digestive enzyme that acts as a protease.Acrosin is released from the acrosome of spermatozoa as a consequence of the acrosome reaction....
attached to the inner membrane of the sperm. 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. 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

Acrosome

In spermatozoon of many animals, the Acrosome is an organelle that develops over the anterior half of the sperm's head. It is a cap-like structure derived from the Golgi apparatus....
to release the enzymes that allow the sperm to fuse with the egg.

Upon penetration, the oocyte is said to have become activated. It undergoes its secondary meiotic division, and the two haploid nuclei (paternal and maternal) fuse to form a zygote

Zygote

Polyspermy

In biology, polyspermy describes an Ovum that has been Fertilisation by more than one Spermatozoon. Ploidy organisms normally contain two copies of each chromosome, one from each parent....
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.