A spermatozoon (; also spelled spermatozoön; ; ) is a motile

sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, ...

cell, or moving form of the haploid cell that is the male

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...

. A spermatozoon joins an

ovum The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete i ...

to form a

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicell ...

. (A zygote is a single cell, with a complete set of

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins ar ...

s, that normally develops into an

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

.) Sperm cells contribute approximately half of the nuclear

genetic information A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. By convention, sequences are u ...

to the

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectiv ...

offspring (excluding, in most cases,

mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

). In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing an X chromosome will lead to a

female Female ( symbol: ♀) is the sex of an organism that produces the large non-motile ova (egg cells), the type of gamete (sex cell) that fuses with the male gamete during sexual reproduction. A female has larger gametes than a male. Fema ...

(XX) offspring, while one bearing a Y chromosome will lead to a

male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...

(XY) offspring. Sperm cells were first observed in Antonie van Leeuwenhoek's laboratory in 1677.

Mammalian spermatozoon structure, function, and size

Humans

The human sperm cell is the reproductive cell in males and will only survive in warm environments; once it leaves the male body the sperm's survival likelihood is reduced and it may die, thereby decreasing the total sperm quality. Sperm cells come in two types, "female" and "male". 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. A human sperm cell consists of a flat, disc shaped head 5.1

µm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer ( American spelling), also commonly known as a micron, is a unit of length in the International System of Uni ...

by 3.1 µm and a tail known as a

flagellum A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

50 µm long. The flagellum propels the sperm cell (at about 1–3 mm/minute in humans) by whipping in an elliptical cone. Sperm have an olfactory guidance mechanism, and after reaching the Fallopian tubes, must undergo a period of

capacitation Capacitation is the penultimate step in the maturation of mammalian spermatozoa and is required to render them competent to fertilize an oocyte. This step is a biochemical event; the sperm move normally and look mature prior to capacitation. ''In ...

before penetration of the ovum. Head: It has a compact nucleus with only chromatic substance and is surrounded by only a thin rim of cytoplasm. Above the nucleus lies a cap-like structure called the acrosome, formed by modification of the Golgi body, which secretes the enzyme spermlysin (''hyaluronidase, corona-penetrating enzyme, zona lysin,'' or ''acrosin''), that is necessary for fertilization. As the spermatozoon approaches the egg, it undergoes the acrosome reaction in which the membrane surrounding the acrosome fuses with the plasma membrane of the sperm's head, exposing the contents of the acrosome. Neck: It is the smallest part (.03µm), and has a proximal

centriole In cell biology a centriole is a cylindrical organelle composed mainly of a protein called tubulin. Centrioles are found in most eukaryotic cells, but are not present in conifers (Pinophyta), flowering plants (angiosperms) and most fungi, and are ...

parallel to the base of the nucleus and distal

perpendicular to the previous one. The proximal centriole is present also in the mature spermatozoon; the distal centriole disappears after axoneme assembly. The proximal centriole enters into the egg during fertilisation and starts the first cleavage division of the egg, which has no centriole. The distal centriole gives rise to the axial filament which forms the tail and has a (9+2) arrangement. A transitory membrane called the ''Manchette'' lies in the middle piece. Middle piece: It has 10–14 spirals of mitochondria surrounding the axial filament in the cytoplasm. It provides motility, and hence is called the powerhouse of the sperm. It also has a ring centriole (annulus) that form a diffusion barrier between the middle piece and the principal piece and serve as a stabilizing structure for tail rigidity. Tail: The flagellum is the longest part (50µm), having an axial filament surrounded by cytoplasm and plasma membrane, but at the posterior end the axial filament is naked. The flagellum gives movement to the cell.

Semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Sem ...

has an alkaline nature and the spermatozoa do not reach full motility (hypermotility) until they reach the vagina, where the alkaline pH is neutralized by acidic vaginal fluids. This gradual process takes 20–30 minutes. During this period, fibrinogen from the seminal vesicles forms a clot, securing and protecting the sperm. Just as they become hypermotile,

fibrinolysin Fibrinolysin is an enzyme derived from plasma of bovine origin (plasmin) or extracted from cultures of certain bacteria. It is used locally only and exclusively together with the enzyme desoxyribonuclease (extracted from bovine pancreas). Fibrino ...

from the

prostate gland The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and physi ...

dissolves the clot, allowing the sperm to progress optimally. The spermatozoon is characterized by a minimum of

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...

and the most densely packed DNA known in eukaryotes. Compared to mitotic chromosomes in somatic cells, sperm DNA is at least sixfold more highly condensed. The specimen contributes with DNA/

chromatin Chromatin is a complex of DNA and protein found in eukaryote, eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important ...

, a

, and perhaps also an

oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ...

-activating factor (OAF). It may also contribute with paternal messenger RNA (mRNA), also contributing to embryonic development. File:Spermatozoa-human-3140x.jpg, Electron

micrograph A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken on a m ...

of human spermatozoa magnified 3140 times. File:Sperms (urine) - Spermler (idrar) - 01.png, Sperm cells in the urine sample of a 45-year-old male patient who is being followed with the diagnosis of

benign prostate hyperplasia Benign prostatic hyperplasia (BPH), also called prostate enlargement, is a noncancerous increase in size of the prostate gland. Symptoms may include frequent urination, trouble starting to urinate, weak stream, inability to urinate, or loss o ...

. File:Sperm Head Dimensions.png, Dimensions of the human sperm head measured from a 39 year-old healthy subject. The human spermatozoon contains at least 7500 different

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

s. Human sperm genetics has been associated with

human evolution Human evolution is the evolutionary process within the history of primates that led to the emergence of '' Homo sapiens'' as a distinct species of the hominid family, which includes the great apes. This process involved the gradual developmen ...

, per a 2020 study.

DNA damage and repair

DNA damages present in spermatozoa in the period after

meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately ...

but before

fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Pro ...

may be repaired in the fertilized egg, but if not repaired, can have serious deleterious effects on fertility and the developing embryo. Human spermatozoa are particularly vulnerable to free radical attack and the generation of oxidative DNA damage. (see e.g. 8-Oxo-2'-deoxyguanosine) Exposure of males to certain lifestyle, environmental or occupational hazards may increase the risk of aneuploid spermatozoa. In particular, risk of aneuploidy is increased by tobacco smoking, and occupational exposure to benzene, insecticides, and perfluorinated compounds. Increased aneuploidy of spermatozoa often occurs in association with increased DNA damage.

DNA fragmentation DNA fragmentation is the separation or breaking of DNA strands into pieces. It can be done intentionally by laboratory personnel or by cells, or can occur spontaneously. Spontaneous or accidental DNA fragmentation is fragmentation that gradually a ...

and increased in situ DNA susceptibility to denaturation, the features similar to these seen during

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes ( morphology) and death. These changes in ...

of somatic cells, characterize abnormal spermatozoa in cases of

male infertility Male infertility refers to a sexually mature male's inability to impregnate a fertile female. In humans it accounts for 40–50% of infertility. It affects approximately 7% of all men. Male infertility is commonly due to deficiencies in the semen ...

Avoidance of immune system response

Glycoprotein Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glyco ...

molecules on the surface of ejaculated sperm cells are recognized by all human female immune systems, and interpreted as a signal that the cell should not be rejected. The female immune system might otherwise 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, thereby avoiding an immune response from the host organism. The blood-testis barrier, maintained by the tight junctions between the Sertoli cells of the seminiferous tubules, prevents communication between the forming spermatozoa in the testis and the blood vessels (and immune cells circulating within them) within the interstitial space. This 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. Some species of fruit fly produce the largest known spermatozoon found in nature. ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the " vinegar fly" or "pomace fly". Starting with ...

'' produces sperm that can be up to 1.8 mm, while its relative ''

Drosophila bifurca ''Drosophila bifurca'' is a species of fruit fly. Males of this species are known to have the longest sperm cells of any organism on Earth—5.8 cm long when uncoiled, over twenty times the entire body length of the male. The cells are mos ...

'' produces the largest known spermatozoon, measuring over 58 mm in length. In Drosophila melanogaster, the entire sperm, tail included, gets incorporated into the

, however, for Drosophila bifurca only a small portion of the tail enters the oocyte. The wood mouse ''

Apodemus sylvaticus The wood mouse (''Apodemus sylvaticus'') is a murid rodent native to Europe and northwestern Africa. It is closely related to the yellow-necked mouse (''Apodemus flavicollis'') but differs in that it has no band of yellow fur around the neck, ha ...

'' possesses spermatozoa with falciform morphology. Another characteristics which makes these gametocytes 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. The postmeiotic phase of mouse spermatogenesis is very sensitive to environmental

genotoxic Genotoxicity is the property of chemical agents that damage the genetic information within a cell causing mutations, which may lead to cancer. While genotoxicity is often confused with mutagenicity, all mutagens are genotoxic, but some genotoxic s ...

agents, because as male germ cells form mature spermatozoa they progressively lose the ability to repair DNA damage. Irradiation of male mice during late spermatogenesis can induce damage that persists for at least 7 days in the fertilizing spermatozoa, and disruption of maternal DNA double-strand break repair pathways increases spermatozoa-derived chromosomal aberrations. Treatment of male mice with melphalan, a bifunctional

alkylating agent Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effectin ...

frequently employed in chemotherapy, induces DNA lesions during meiosis that may persist in an unrepaired state as germ cells progress through DNA repair-competent phases of spermatogenic development. Such unrepaired DNA damages in spermatozoa, after fertilization, can lead to offspring with various abnormalities. Sea urchins such as '' Arbacia punctulata'' are ideal organisms to use in sperm research, they spawn large numbers of sperm into the sea, making them well-suited as model organisms for experiments. The spermatozoa of

marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in ...

s are usually longer than those of placental mammals.

Plants, algae and fungi

The

gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the ...

s of bryophytes,

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...

s and some

gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμν ...

s produce motile

cells, contrary to pollen grains employed in most gymnosperms and all

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants ...

s. This renders sexual reproduction in the absence of

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

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 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 Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubu ...

. Round cells called spermatogonia divide and differentiate eventually to become spermatozoa. During

copulation Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetra ...

the cloaca or vagina gets inseminated, and then the spermatozoa move through chemotaxis to the ovum inside a Fallopian tube. In

assisted reproductive technology Assisted reproductive technology (ART) includes medical procedures used primarily to address infertility. This subject involves procedures such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), cryopreservation of gamet ...

, normozoospermia is referred to a total amount of >39 mill ejaculated, >32% with progressive motility and >4% normal morphology. Also, a normal ejaculation in humans must have a volume over 1.5 ml, being an excessive volume 6 ml per ejaculation ( hyperspermia). An insufficient volume is called

hypospermia Hypospermia is a condition in which a man has an unusually low ejaculate (or semen) volume, less than 1.5 mL. It is the opposite of hyperspermia, which is a semen volume of more than 5.5 mL. It should not be confused with oligospermia, which me ...

. These problems are related to several complications in spermatozoa production, for example: * Hyperspermia: usually provoked because of prostate inflammation. * Hypospermia: an incomplete ejaculation, usually referred to an androgen deficit ( hypoandrogenism) or obstruction in some part of the ejaculatory duct. In laboratory conditions, is also due to a partial loss of the sample. * Aspermia: there is no ejaculation. It could happen due to retrograde ejaculation, anatomical or neurological diseases or anti-hypertensive drugs.

Spermatozoa activation

Approaching the egg cell is a rather complex, multistep process of chemotaxis guided by different chemical substances/stimuli on individual levels of phylogeny. One of the most significant, common signaling characters of the event is that a prototype of professional chemotaxis receptors,

formyl peptide receptor The formyl peptide receptors (FPR) belong to a class of G protein-coupled receptors involved in chemotaxis. In humans, there are three formyl peptide receptor isoforms, each encoded by a separate gene that are named FPR1, FPR2, and FPR3. Th ...

(60,000 receptor/cell) as well as the activator ability of its ligand formyl Met-Leu-Phe have been demonstrated in the surface membrane even in the case of human sperms. 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 is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...

ionophores ''

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology a ...

'', progesterone released by nearby

cumulus cell The cumulus oophorus, (discus proligerus), is a cluster of cells that surround the oocyte both in the ovarian follicle and after ovulation. In the antral follicle, it may be regarded as an extension of the membrana granulosa. The innermost layer o ...

s and binding to

ZP3 Zona pellucida sperm-binding protein 3, also known as zona pellucida glycoprotein 3 (Zp-3) or the sperm receptor, is a ZP module-containing protein that in humans is encoded by the ''ZP3'' gene. ZP3 is the receptor in the zona pellucida which bi ...

of the zona pellucida. 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. 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 channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ...

s formed by proteins called

CatSper The cation channels of sperm also known as Catsper channels or CatSper, are ion channels that are related to the two-pore channels and distantly related to TRP channels. The four members of this family form voltage-gated Ca2+ channels that ...

. These channels are selective, allowing only calcium ions 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. This involves releasing the contents of the acrosome, which disperse, and the exposure of enzymes attached to the inner acrosomal membrane of the sperm. This occurs after the sperm first meets the egg. 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. ZP3, one of the proteins that make up the zona pellucida, then binds to a partner molecule on the sperm. Enzymes on the inner acrosomal membrane digest the zona pellucida. After the sperm penetrates the zona pellucida, part of the sperm's cell membrane then fuses with the egg cell's membrane, and the contents of the head diffuse into 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

. In order to prevent polyspermy and minimise the possibility of producing a triploid zygote, several changes to the egg's zona pellucida renders them impenetrable shortly after the first sperm enters the egg.

Artificial storage

Spermatozoa can be stored in diluents such as the ''Illini Variable Temperature'' (IVT) diluent, which have been reported to be able to preserve high fertility of spermatozoa for over seven days. The IVT diluent is composed of several salts, sugars and antibacterial agents and gassed with CO₂. Semen cryopreservation can be used for far longer storage durations. For human spermatozoa, the longest reported successful storage with this method is 21 years.Planer NEWS and Press Releases > Child born after 21 year semen storage using Planer controlled rate freezer
14/10/2004

MMP and capacitation

The

is the final phase of spermatozoa development, when they acquire the capability to fertilize the oocyte. In vivo, it happens during ejaculation, when spermatozoa leave the vagina and come in the superior female reproductive tract. In vitro, it happens when the spermatozoa is washed and purified. Almost 30-40% of infertility is due to male factor, so several strategies have been created in order to recover the functional spermatozoa. The MMP (Million Motile Progressive cells per milliliter) measure is synonymous with

, and is very useful parameter to decide, along with a spermiogram, the kind of treatment needed. it represents the ratio between the % of progressive motile sperm obtained in capacitated and the % of progressive motile sperm obtained in ejaculated. It is based on the recovery percentage. Depending on the percentage, we will decide the quality of the motile spermatozoa recovery: 15 to 25 million sperm/ml is considered optimal, between 5 and 15 million is considered enough and less than 5 million is considered sub-optimal or not sufficient. Regarding the values that we have obtained, along with the spermiogram results, different techniques will be displayed. For example, if more than 1.0×10⁶ progressive motile sperm per milliliter are found, it will be recommended to have sexual intercourse, and if that fails, the next step will be

intrauterine insemination Artificial insemination is the deliberate introduction of sperm into a female's cervix or uterine cavity for the purpose of achieving a pregnancy through in vivo fertilization by means other than sexual intercourse. It is a fertility treatment ...

and later conventional in vitro fertilization. With less than 1.0×10⁶ progressive motile sperm per milliliter, we will perform intracytoplasmic sperm injection. In case of azoospermia (no spermatozoa in the ejaculate), we will do a testicular biopsy in order to check if there are spermatozoa in the testes or if no spermatozoa are being produced.

History

* In 1677 microbiologist Antonie van Leeuwenhoek discovered spermatozoa. * In 1841 the Swiss anatomist

Albert von Kölliker Albert von Kölliker (born Rudolf Albert Kölliker'';'' 6 July 18172 November 1905) was a Swiss anatomist, physiologist, and histologist. Biography Albert Kölliker was born in Zurich, Switzerland. His early education was carried on in Zurich, ...

wrote about spermatozoon in his work ''Untersuchungen über die Bedeutung der Samenfäden (Studies on the importance of spermatozoa).''

References

External links

Slower conception 'leads to boys'

Human Sperm Under a Microscope
{{Authority control Germ cells Semen Human cells Fertility Men's health Microscopic discoveries by Antonie van Leeuwenhoek