Sperm Cell

Sperm Cell



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Sperm Cell
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What’s the Function of a Sperm Cell? – Definition & Structure
What’s the Function of a Sperm Cell? – Definition & Structure

By Antonio Barberá BSc (embryologist), Emilio Gómez Sánchez BSc, PhD (senior embryologist), Zaira Salvador BSc, MSc (embryologist) and Sandra Fernández BA, MA (fertility counselor).
By Emilio Gómez Sánchez BSc, PhD (senior embryologist).
By Zaira Salvador BSc, MSc (embryologist).
By Zaira Salvador BSc, MSc (embryologist).
By Zaira Salvador BSc, MSc (embryologist).
By Zaira Salvador BSc, MSc (embryologist).
By Zaira Salvador BSc, MSc (embryologist).
By Zaira Salvador BSc, MSc (embryologist).
By Zaira Salvador BSc, MSc (embryologist).
By Zaira Salvador BSc, MSc (embryologist).
Bachelor's Degree in Biology and Biochemistry from the University of Valencia (UV). He has developed several research projects for the Research Foundation La Fe (Valencia, Spain). He has been working as a biologist and biochemist at the andrology lab of CREA Valencia for over 8 years. More information about Antonio Barberá
Bachelor's Degree in Biology from the University of Seville. PhD in Biology from the University of Valencia. Large experience as an Embryologist Specialized in Assisted Reproduction. Currently, he is the IVF Lab Director of Tahe Fertilidad. More information about Emilio Gómez Sánchez
Bachelor's Degree in Biotechnology from the Technical University of Valencia (UPV). Biotechnology Degree from the National University of Ireland en Galway (NUIG) and embryologist specializing in Assisted Reproduction, with a Master's Degree in Biotechnology of Human Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI) More information about Zaira Salvador
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández
What Is The Function of Sperm Cells?
How do you know when a man is fertile?
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Male Fertility – Parts & Functions of the Male Reproductive System
Fertility in males depends on the proper functioning of their reproductive system. Learn about its anatomy with pictures and definitions of its organs. Read more
It takes place in testicles and lasts two months and a half approximately. It is the maduration of some cells that split, madurate, and eventually become spermatozoa. Read more
Sperm’s Journey to the Egg – How Sperm Meets Egg with Pictures
How long does it take for sperm to reach the egg? When and where does sperm meet egg? Get the answer to these questions about the sperm's path to the egg. Read more

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A spermatozoon, in plural spermatozoa , or sperm cell is the male reproductive cell that is expelled along with the seminal fluid or semen when a man ejaculates. In humans, spermatozoa determine the gender of the baby-to-be, which means that they can carry either the X or the Y chromosome.
The function of spermatozoa is to fertilize the egg cell during fertilization, creating a new organism called zygote that will develop from embryo to fetus during the 9 months of pregnancy. Human sperm cells are haploid, which means that they contain 23 chromosomes.
Below you have an index with the 10 points we are going to deal with in this article.
The sperms, spermatozoa or sperm cells are the male sex cells. Their function is to combine with the female sex cell and create a completely new organism. Spermatozoa are expelled with seminal fluid (semen) during ejaculation.
Spermatozoa production takes place in the testis, while oocytes or egg cells are produced in the ovaries of the woman. When an egg and a spermatozoon unite, they create a zygote, which will develop into an embryo (an unborn, developing organism), and later into a fetus.
Learn about the differences between these terms with this post: Differences between human zygote, embryo and fetus .
In humans, the sperm cell is the one responsible for determining the gender of the new organism . This means that spermatozoa can carry either a Y or an X chromosome, while egg cells always contain an X chromosome.
Human sperm cells are always haploid, that is, they contain 23 chromosomes. When a spermatozoon reaches and joins an oocyte, which also contains 23 chromosomes, they form a diploid cell of 46 cells.
Spermatozoa are structurally specialized to its function through the following anatomical changes:
According to experts, actually spermatozoa have a very narrow function in comparison with other cells that adapt to their function as well. For example, they lack ribosomes, since they are actually unnecessary for carrying DNA to the egg cell.
Before ejaculation, spermatozoa pass through the ejaculatory ducts, and mix with fluids from the seminal vesicles, bulbourethral glands, and the prostate. In fact, 65-75% of the semen expelled contains fluids from the seminal vesicles, including:
Also, the sertoli cells secrete a fluid into the seminiferous tubules that helps in the transport of spermatozoa to the genital ducts. In short, semen is typically translucent with white or grey tint, sometimes yellowish.
The presence of blood in the semen is known as hematospermia and can cause a reddish or pinkish color. If this happens, it may indicate a medical problem that should be evaluated by your doctor.
Very simply put, seminal fluid is comprised of proteins, fructose, water and other components such as vitamins, minerals, etc. So, dehydration, a lack of nutrients, or vitamin deficiency can lead to male infertility if untreated.
The scientist Antonie van Leeuwenhoek was the first person who described in detail the structure of a sperm cell in 1677. Although the parts of spermatozoa are more or less common in all mammal species—a head and a long tail—there are small differences between species, especially in the morphology of the head.
Spermatozoa are the only human cells that contain flagella. They are made up of three basic parts : the head, the middle-piece, and the tail.
The head is an oval-shaped structure, which size ranges from 5 to 8 µm. It consists of two parts:
The neck and the middle piece, as the name suggests, are the parts that can be found between the head and the tail. Their function is to connect both ends of the sperm cell.
As one shall she in the diagram below, the neck contains millions of spirally arranged mitochondria . Their function is to provide the sperm will all the energy required by the flagellum to allow it to swim in the female reproductive tract.
The tail, also known as flagellum , is a long structure which main function is to allow sperm motility by means of a slithering, snake-like movement.
The length of the tail is about 50 µm, allowing a swimming velocity of 3 millimeters per minute approximately.
Sperm tail defects or alterations can lead to male fertility problems, being asthenozoospermia the most frequent one.
After ejaculation, most sperm die within minutes outside the woman's genital tract. If spermatozoa enter the female reproductive system (the cervix and uterus), they can survive 1-2 days , some up to 5 days.
Even though some sperms are able to survive for up to 5 days, almost all pregnancies can be attributed to intercourse that occurred 1-2 days prior to ovulation , as the percentage of sperms that are able to survive less than five days is higher.
On the other hand, when sperm are processed and stored under strict laboratory conditions in a nutrient-rich medium, they can remain alive for up to 7 days. If collected at home into a sterile container, their fertilizing capability will drop dramatically within 60 minutes.
So, in conclusion, the lifespan of human spermatozoa is 24-48 hours, but it depends on the environment, which is to say, the conditions under which they are held. If exposed to air or deposited on clothing, they dry out rapidly and die within minutes after ejaculation.
Sperm cell diseases or defects are more common than one may think. They occur in the structure of the sperm cell and can lead to male infertility, thereby preventing fertilization from taking place.
Teratozoospermia is a common abnormality that affects sperm morphology , that is, the shape of the sperm cells is altered (for example, sperm cells with 2 heads). Defects can be found either in the head, neck, tail, or in several parts simultaneously.
The sperm cell uses flagella to move towards the Fallopian tube; if they are damaged or not working, it will never meet the egg and subsequently fertilization will not occur. When male fertility issues are caused by alterations related to sperm motility, the patient is diagnosed with asthenozoospermia through a sperm analysis (SA). Vitamin supplements are often recommended as a home remedy when a man has issues related with the motility of his sperm.
Sperm diseases related to the anatomy of spermatozoa can translate into a man being infertile in the most severe cases. They can be caused by defects during spermatogenesis (sperm production), or by alterations acquired during the sperm maturation process and pathway until the sperms come out with ejaculation.
If you need to undergo IVF to become a mother, we recommend that you generate your Fertility Report now. In 3 simple steps, it will show you a list of clinics that fit your preferences and meet our strict quality criteria. Moreover, you will receive a report via email with useful tips to visit a fertility clinic for the first time.
Spermatogenesis is the process whereby male reproductive cells are formed, from the immature ones, spermatogonia, until the mature ones, spermatozoa. This complicated process occurs within the seminiferous tubule in the testis and takes about 64-72 days.
Once spermatozoa (sperm cells) have been produced, they leave the testis and travel to the epididymis, where they will acquire the necessary motility in a process that lasts 10 days approximately. Spermatozoa will be stored in the epididymis until they are expelled with ejaculation. When ejaculation starts, sperm travel through the vasa deferentia and mingle with the seminal fluid that originates in the secretory glands, creating what we all know as semen . Finally, it is expelled through the urethra.
Sperm cells cannot divide because they are haploid, that is, they contain 23 chromosomes. However, after the fusion with the egg cell, which contains 23 chromosomes as well, they create a diploid cell of 46 chromosomes (totipotent zygote).
A spermatozoon (in plural spermatozoa ) is a motile sperm cell, that is, the reproductive cell of human males, carried in semen, that fertilizes the ovum to create a new human being, while the term sperm is commonly used to refer to the semen.
Approximately, the distance that spermatozoa travel through the female reproductive tract is about 15 to 18 cm. Experts have discovered that sperms have to travel distances that are around 1,000 times their own length while they swim in the right direction towards the egg.
Mitochondria supply energy to the sperm cells and are responsible for carrying out the process of respiration, necessary to provide the tail (flagellum) with the energy supply that it needed to allow the sperm cell to swim towards the egg.
As explained above, spermatozoa are haploid: they contain 23 chromosomes. Both sperm cells and egg cells contain half the chromosomes contained in normal diploid cells (a.k.a. somatic cells ). Haploid cells are produced during meiosis.
Egg cells are the complete opposite of sperm cells, actually. The main and most obvious difference is that egg cells are produced in the female reproductive system, while sperm cells develop in the testes, which are part of the male reproductive system.
On the other hands, while spermatozoa are one of the smallest cells in the male body, ova are one of the largest cells present in the body of human females.
Not literally, but in a way yes. Actually, blood brings oxygen and nutrition to the testicles. In fact, everything in our body (both in males and females) gets oxygen and nutrients from blood. So, while blood should not present in the semen, it is responsible for the sperm production process.
While there exist many old-wives tales and myths about this, the truth is that there is a 50% chance that a sperm cell will carry an X chromosome and a 50% chance that it will carry a Y chromosome. So, in short, the assignment of gender occurs 100% randomly.
We have laearned about the anatomy of sperm cells, but do you know how they are formed and where? This process, called spermatogenesis, is explained in detail here: How are sperm produced?
Now that we have learned about the parts and functions of a sperm cell, you may want to find out what is the pathway of sperm in their journey to the egg. Check this out to get more information: Sperm's journey to the egg .
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Find the latest news on assisted reproduction in our channels.

Sperm Cells - Definition, Function, Structure, Adaptations, Microscopy
What’s the Function of a Sperm Cell ? - Definition & Structure
Sperm — Wikipedia Republished // WIKI 2 | Non-motile sperm cells
What Are Sperm Cells ? (with pictures)
Sperm cells (magnified 1,000 times). | Britannica
For other uses, see Sperm (disambiguation) .
Video of human sperm cells under a microscope
Sperm and egg fusing ( fertilisation )
Dimensions of the human sperm head measured from a 39 year-old healthy human subject.
Human sperm stained for semen quality testing
Further information: Sperm donation
Motile sperm cells of algae and seedless plants [31]


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^ Wilson, Clare (July 31, 2020). "Sperm have a weird way of swimming and we only noticed after 300 years" . New Scientist .

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^ a b Fishman, Emily L; Jo, Kyoung; Nguyen, Quynh P. H; Kong, Dong; Royfman, Rachel; Cekic, Anthony R; Khanal, Sushil; Miller, Ann L; Simerly, Calvin; Schatten, Gerald; Loncarek, Jadranka; Mennella, Vito; Avidor-Reiss, Tomer (2018). "A novel atypical sperm centriole is functional during human fertilization" . Nature Communications . 9 (1): 2210. Bibcode : 2018NatCo...9.2210F . doi : 10.1038/s41467-018-04678-8 . PMC   5992222 . PMID   29880810 .

^ Blachon, S; Cai, X; Roberts, K. A; Yang, K; Polyanovsky, A; Church, A; Avidor-Reiss, T (2009). "A Proximal Centriole-Like Structure is Present in Drosophila Spermatids and Can Serve as a Model to Study Centriole Duplication" . Genetics . 182 (1): 133–44. doi : 10.1534/genetics.109.101709 . PMC   2674812 . PMID   19293139 .

^ Hewitson, Laura & Schatten, Gerald P. (2003). "The biology of fertilization in humans" . In Patrizio, Pasquale; et al. (eds.). A color atlas for human assisted reproduction: laboratory and clinical insights . Lippincott Williams & Wilkins. p. 3. ISBN   978-0-7817-3769-2 . Retrieved 2013-11-09 .

^ Semen and sperm quality

^ Gould, JE; Overstreet, JW; Hanson, FW (1984). "Assessment of human sperm function after recovery from the female reproductive tract" . Biology of Reproduction . 31 (5): 888–894. doi : 10.1095/biolreprod31.5.888 . PMID   6518230 .

^ Cyranoski, David (2016). "Researchers claim to have made artificial mouse sperm in a dish". Nature . doi : 10.1038/nature.2016.19453 . S2CID   87014225 .

^ Gurevich, Rachel (2008-06-10). "Does Age Affect Male Fertility?" . About.com . Retrieved 14 February 2010 .

^ Gavriliouk D, Aitken RJ (2015). "Damage to Sperm DNA Mediated by Reactive Oxygen Species: Its Impact on Human Reproduction and the Health Trajectory of Offspring". The Male Role in Pregnancy Loss and Embryo Implantation Failure . Advances in Experimental Medicine and Biology. 868 . pp. 23–47. doi : 10.1007/978-3-319-18881-2_2 . ISBN   978-3-319-18880-5 . PMID   26178844 .

^ Marchetti F, Wyrobek AJ (2008). "DNA repair decline during mouse spermiogenesis results in the accumulation of heritable DNA damage" . DNA Repair . 7 (4): 572–81. doi : 10.1016/j.dnarep.2007.12.011 . PMID   18282746 .

^ Marchetti F, Essers J, Kanaar R, Wyrobek AJ (2007). "Disruption of maternal DNA repair increases sperm-derived chromosomal aberrations" . Proceedings of the National Academy of Sciences of the United States of America . 104 (45): 17725–9. Bibcode : 2007PNAS..10417725M . doi : 10.1073/pnas.0705257104 . PMC   2077046 . PMID   17978187 .

^ Marchetti F, Bishop J, Gingerich J, Wyrobek AJ (2015). "Meiotic interstrand DNA damage escapes paternal repair and causes chromosomal aberrations in the zygote by maternal misrepair" . Scientific Reports . 5 : 7689. Bibcode : 2015NatSR...5E7689M . doi : 10.1038/srep07689 . PMC   4286742 . PMID   25567288 .

^ Lüpold, Stefan; Manier, Mollie K; Puniamoorthy, Nalini; Schoff, Christopher; Starmer, William T; Luepold, Shannon H. Buckley; Belote, John M; Pitnick, Scott (2016). "How sexual selection can drive the evolution of costly sperm ornamentation" . Nature . 533 (7604): 535–8. Bibcode : 2016Natur.533..535L . doi : 10.1038/nature18005 . PMID   27225128 . S2CID   4407752 .

^ Gardiner, Jennifer R (2016). "The bigger, the better" . Nature . 533 (7604): 476. doi : 10.1038/533476a . PMID   27225117 .

^ Sarfraz Manzoor (2 November 2012). "Come inside: the world's biggest sperm bank" . The Guardian . Retrieved 4 August 2013 .

^ a b c Assisted Reproduction in the Nordic Countries ncbio.org

^ a b FDA Rules Block Import of Prized Danish Sperm Posted Aug 13, 08 7:37 AM CDT in World, Science & Health

^ a b Steven Kotler (26 September 2007). "The God of Sperm" .

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^ Fiedler, Anja; Rehdorf, Jessica; Hilbers, Florian; Johrdan, Lena; Stribl, Carola; Benecke, Mark (2008). "Detection of Semen (Human and Boar) and Saliva on Fabrics by a Very High Powered UV-/VIS-Light Source" . The Open Forensic Science Journal . 1 : 12–15. doi : 10.2174/1874402800801010012 .

^ Allery, J. P; Telmon, N; Mieusset, R; Blanc, A; Rougé, D (2001). "Cytological detection of spermatozoa: Comparison of three staining methods". Journal of Forensic Sciences . 46 (2): 349–51. doi : 10.1520/JFS14970J . PMID   11305439 .

^ Illinois State Police/President's DNA Initiative. "The Presidents's DNA Initiative: Semen Stain Identification: Kernechtrot" (PDF) . Retrieved 2009-12-10 .

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^ Sumbali, Geeta (2005). The Fungi . Alpha Science Int'l Ltd. ISBN   1-84265-153-6 .

^ Maheshwari R (1999). "Microconidia of Neurospora crassa". Fungal Genetics and Biology . 26 (1): 1–18. doi : 10.1006/fgbi.1998.1103 . PMID   10072316 .

^ Avidor-Reiss, T; Khire, A; Fishman, EL; Jo, KH (2015). "Atypical centrioles during sexual reproduction" . Front Cell Dev Biol . 3 : 21. doi : 10.3389/fcell.2015.00021 . PMC   4381714 . PMID   25883936 .

^ Blachon, S.; Cai, X.; Roberts, K. A.; Yang, K.; Polyanovsky, A.; Church, A.; Avidor-Reiss, T. (May 2009). "A Proximal Centriole-Like Structure Is Present in Drosophila Spermatids and Can Serve as a Model to Study Centriole Duplication" . Genetics . 182 (1): 133–44. doi : 10.1534/genetics.109.101709 . PMC   2674812 . PMID   19293139 .

^ Avidor-Reiss, Tomer; Leroux, Michel R (2015). "Shared and Distinct Mechanisms of Compartmentalized and Cytosolic Ciliogenesis" . Current Biology . 25 (23): R1143–50. doi : 10.1016/j.cub.2015.11.001 . PMC   5857621 . PMID   26654377 .




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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 , which are known as sper­ma­to­zoa , while some red algae and fungi pro­duce non-motile sperm cells, known as sper­ma­tia . [1] Flow­er­ing plants con­tain non-motile sperm in­side pollen , while some more basal plants like ferns and some gym­nosperms have motile sperm. [2]

Sperm cells form dur­ing the process known as sper­mato­ge­n­e­sis , which in am­niotes ( rep­tiles and mam­mals ) takes place in the sem­i­nif­er­ous tubules of the testes . [3] This process in­volves the pro­duc­tion of sev­eral suc­ces­sive sperm cell pre­cur­sors, start­ing with sper­mato­go­nia , which dif­fer­en­ti­ate into sper­ma­to­cytes . The sper­ma­to­cytes then un­dergo meio­sis , re­duc­ing their chro­mo­some num­ber by half, which pro­duces sper­matids . The sper­matids then ma­ture and, in an­i­mals, con­struct a tail, or fla­gel­lum, which gives rise to the ma­ture, motile sperm cell. This whole process oc­curs con­stantly and takes around 3 months from start to fin­ish.

Sperm cells can­not di­vide and have a lim­ited lifes­pan, but after fu­sion with egg cells dur­ing fer­til­i­sa­tion , a new or­gan­ism be­gins de­vel­op­ing, start­ing as a totipo­tent zy­gote . The human sperm cell is hap­loid , so that its 23 chro­mo­somes can join the 23 chro­mo­somes of the fe­male egg to form a diploid cell. In mam­mals , sperm is stored in the epi­didymis and is re­leased from the penis dur­ing ejac­u­la­tion in a fluid known as semen .

The word sperm is de­rived from the Greek word σπέρμα , sperma , mean­ing "seed".

The main sperm func­tion is to reach the ovum and fuse with it to de­liver two sub-cel­lu­lar struc­tures: (i) the male pronu­cleus that con­tains the ge­netic ma­te­r­ial and (ii) the cen­tri­oles that are struc­tures that help or­ga­nize the mi­cro­tubule cy­toskele­ton .

The mam­malian sperm cell can be di­vided in 2 parts:

The neck or con­nect­ing piece con­tains one typ­i­cal cen­tri­ole and one atyp­i­cal cen­tri­ole such as the prox­i­mal cen­tri­ole-like . [10] [11] The mid­piece has a cen­tral fil­a­men­tous core with many mi­to­chon­dria spi­ralled around it, used for ATP pro­duc­tion for the jour­ney through the fe­male cervix , uterus and uter­ine tubes .

Dur­ing fer­til­iza­tion , the sperm pro­vides three es­sen­tial parts to the oocyte : (1) a sig­nalling or ac­ti­vat­ing fac­tor, which causes the meta­bol­i­cally dor­mant oocyte to ac­ti­vate; (2) the hap­loid pa­ter­nal genome ; (3) the cen­tri­ole , which is re­spon­si­ble for form­ing the cen­tro­some and mi­cro­tubule sys­tem. [12]

The sper­ma­to­zoa of an­i­mals are pro­duced through sper­mato­ge­n­e­sis in­side the male go­nads ( tes­ti­cles ) via mei­otic di­vi­sion. The ini­tial sper­ma­to­zoon process takes around 70 days to com­plete. The process starts with the pro­duc­tion of sper­mato­go­nia from germ cell pre­cur­sors. These di­vide and dif­fer­en­ti­ate into sper­ma­to­cytes , which un­dergo meio­sis to form sper­matids . In the sper­matid stage, the sperm de­vel­ops the fa­mil­iar tail. The next stage where it be­comes fully ma­ture takes around 60 days when it is called a sper­ma­to­zoan . [13] Sperm cells are car­ried out of the male body in a fluid known as semen . Human sperm cells can sur­vive within the fe­male re­pro­duc­tive tract for more than 5 days post coitus. [14] Semen is pro­duced in the sem­i­nal vesi­cles , prostate gland and ure­thral glands .

In 2016, sci­en­tists at Nan­jing Med­ical Uni­ver­sity claimed they had pro­duced cells re­sem­bling mouse sper­matids from mouse em­bry­onic stem cells ar­ti­fi­cially. They in­jected these sper­matids into mouse eggs and pro­duced pups. [15]

Sperm quan­tity and qual­ity are the main pa­ra­me­ters in semen qual­ity , which is a mea­sure of the abil­ity of semen to ac­com­plish fer­til­iza­tion . Thus, in hu­mans, it is a mea­sure of fer­til­ity in a man . The ge­netic qual­ity of sperm, as well as its vol­ume and motil­ity, all typ­i­cally de­crease with age. [16] (See pa­ter­nal age ef­fect .)

DNA dam­ages pre­sent in sperm cells in the pe­riod after meio­sis but be­fore fer­til­iza­tion may be re­paired in the fer­til­ized egg, but if not re­paired, can have se­ri­ous dele­te­ri­ous ef­fects on fer­til­ity and the de­vel­op­ing em­bryo. Human sperm cells are par­tic­u­larly vul­ner­a­ble to free rad­i­cal at­tack and the gen­er­a­tion of ox­ida­tive DNA damage. [17] (see e.g. 8-Oxo-2'-de­oxyguano­sine )

The post­mei­otic phase of mouse sper­mato­ge­n­e­sis is very sen­si­tive to en­vi­ron­men­tal geno­toxic agents, be­cause as male germ cells form ma­ture sperm they pro­gres­sively lose the abil­ity to re­pair DNA damage. [18] Ir­ra­di­a­tion of male mice dur­ing late sper­mato­ge­n­e­sis can in­duce dam­age that per­sists for at least 7 days in the fer­til­iz­ing sperm cells, and dis­rup­tion of ma­ter­nal DNA dou­ble-strand break re­pair path­ways in­creases sperm cell-de­rived chro­mo­so­mal aberrations. [19] Treat­ment of male mice with mel­pha­lan , a bi­func­tional alky­lat­ing agent 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. [20] Such un­re­paired DNA dam­ages in sperm cells, after fer­til­iza­tion, can lead to off­spring with var­i­ous ab­nor­mal­i­ties.

Re­lated to sperm qual­ity is sperm size, at least in some an­i­mals. For in­stance, the sperm of some species of fruit fly ( Drosophila ) are up to 5.8 cm long — about 20 times as long as the fly it­self. Longer sperm cells are bet­ter than their shorter coun­ter­parts at dis­plac­ing com­peti­tors from the fe­male's sem­i­nal re­cep­ta­cle. The ben­e­fit to fe­males is that only healthy males carry ‘good’ genes that can pro­duce long sperm in suf­fi­cient quan­ti­ties to out­com­pete their competitors. [21] [22]

Some sperm banks hold up to 170 litres (37 imp gal; 45 US gal) of sperm. [23]

In ad­di­tion to ejac­u­la­tion , it is pos­si­ble to ex­tract sperm through TESE .

On the global mar­ket, Den­mark has a well-de­vel­oped sys­tem of human sperm ex­port. This suc­cess mainly comes from the rep­u­ta­tion of Dan­ish sperm donors for being of high qual­ity [24] and, in con­trast with the law in the other Nordic coun­tries, gives donors the choice of being ei­ther anony­mous or non-anony­mous to the re­ceiv­ing couple. [24] Fur­ther­more, Nordic sperm donors tend to be tall and highly educated [25] and have al­tru­is­tic mo­tives for their donations, [25] partly due to the rel­a­tively low mon­e­tary com­pen­sa­tion in Nordic coun­tries. More than 50 coun­tries world­wide are im­porters of Dan­ish sperm, in­clud­ing Paraguay , Canada , Kenya , and Hong Kong . [24] How­ever, the Food and Drug Ad­min­is­tra­tion (FDA) of the US has banned im­port of any sperm, mo­ti­vated by a risk of trans­mis­sion of Creutzfeldt–Jakob dis­ease , al­though such a risk is in­signif­i­cant, since ar­ti­fi­cial in­sem­i­na­tion is very dif­fer­ent from the route of trans­mis­sion of Creutzfeldt–Jakob dis­ease . [26] The preva­lence of Creutzfeldt–Jakob dis­ease for donors is at most one in a mil­lion, and if the donor was a car­rier, the in­fec­tious pro­teins would still have to cross the blood-testis bar­rier to make trans­mis­sion possible. [26]

Sperm were first ob­served in 1677 by An­tonie van Leeuwen­hoek [27] using a mi­cro­scope . He de­scribed them as being an­i­mal­cules (lit­tle an­i­mals), prob­a­bly due to his be­lief in pre­for­ma­tion­ism , which thought that each sperm con­tained a fully formed but small human. [ citation needed ]

Ejac­u­lated flu­ids are de­tected by ul­tra­vi­o­let light , ir­re­spec­tive of the struc­ture or colour of the surface. [28] Sperm heads, e.g. from vagi­nal swabs, are still de­tected by mi­croscopy using the "Christ­mas Tree Stain" method, i.e., Kernechtrot-Pi­croindigo­carmine (KPIC) staining. [29] [30]

Sperm cells in algal and many plant ga­me­to­phytes are pro­duced in male ga­metan­gia ( an­theridia ) via mi­totic di­vi­sion. In flow­er­ing plants , sperm nu­clei are pro­duced in­side pollen . [ citation needed ]

Motile sperm cells typ­i­cally move via fla­gella and re­quire a water medium in order to swim to­ward the egg for fer­til­iza­tion. In an­i­mals most of the en­ergy for sperm motil­ity is de­rived from the me­tab­o­lism of fruc­tose car­ried in the sem­i­nal fluid . This takes place in the mi­to­chon­dria lo­cated in the sperm's mid­piece (at the base of the sperm head). These cells can­not swim back­wards due to the na­ture of their propul­sion. The uni­fla­gel­lated sperm cells (with one fla­gel­lum) of an­i­mals are re­ferred to as sper­ma­to­zoa , and are known to vary in size. [ citation needed ]

Motile sperm are also pro­duced by many pro­tists and the ga­me­to­phytes of bryophytes , ferns and some gym­nosperms such as cy­cads and ginkgo . The sperm cells are the only fla­gel­lated cells in the life cycle of these plants. In many ferns and ly­co­phytes , cy­cads and ginkgo they are multi-fla­gel­lated (car­ry­ing more than one flagellum). [31]

In ne­ma­todes , the sperm cells are amoe­boid and crawl, rather than swim, to­wards the egg cell. [32]

Non-motile sperm cells called sper­ma­tia lack fla­gella and there­fore can­not swim. Sper­ma­tia are pro­duced in a sper­matangium . [31]

Be­cause sper­ma­tia can­not swim, they de­pend on their en­vi­ron­ment to carry them to the egg cell. Some red algae , such as Poly­si­pho­nia , pro­duce non-motile sper­ma­tia that are spread by water cur­rents after their release. [31] The sper­ma­tia of rust fungi are cov­ered with a sticky sub­stance. They are pro­duced in flask-shaped struc­tures con­tain­ing nec­tar , which at­tract flies that trans­fer the sper­ma­tia to nearby hy­phae for fer­til­iza­tion in a mech­a­nism sim­i­lar to in­sect pol­li­na­tion in flow­er­ing plants . [33]

Fun­gal sper­ma­tia (also called py­c­niospores, es­pe­cially in the Ure­d­i­nales) may be con­fused with coni­dia . Coni­dia are spores that ger­mi­nate in­de­pen­dently of fer­til­iza­tion, whereas sper­ma­tia are ga­metes that are re­quired for fer­til­iza­tion. In some fungi, such as Neu­rospora crassa , sper­ma­tia are iden­ti­cal to mi­cro­coni­dia as they can per­form both func­tions of fer­til­iza­tion as well as giv­ing rise to new or­gan­isms with­out fertilization. [34]

In al­most all em­bryophytes , in­clud­ing most gym­nosperms and all an­giosperms , the male ga­me­to­phytes ( pollen grains ) are the pri­mary mode of dis­per­sal , for ex­am­ple via wind or in­sect pol­li­na­tion , elim­i­nat­ing the need for water to bridge the gap be­tween male and fe­male. Each pollen grain con­tains a sper­matoge­nous (gen­er­a­tive) cell. Once the pollen lands on the stigma of a re­cep­tive flower, it ger­mi­nates and starts grow­ing a pollen tube through the carpel . Be­fore the tube reaches the ovule , the nu­cleus of the gen­er­a­tive cell in the pollen grain di­vides and gives rise to two sperm nu­clei, which are then dis­charged through the tube into the ovule for fertilization. [31]

In some pro­tists , fer­til­iza­tion also in­volves sperm nu­clei , rather than cells, mi­grat­ing to­ward the egg cell through a fer­til­iza­tion tube. Oomycetes form sperm nu­clei in a syn­cyt­i­cal an­therid­ium sur­round­ing the egg cells. The sperm nu­clei reach the eggs through fer­til­iza­tion tubes, sim­i­lar to the pollen tube mech­a­nism in plants. [31]

Most sperm cells have cen­tri­oles in the sperm neck. [35] Sperm of many an­i­mals has 2 typ­i­cal cen­tri­oles known as the prox­i­mal cen­tri­ole and dis­tal cen­tri­ole. Some an­i­mals like human and bovine have a sin­gle typ­i­cal cen­tri­ole, known as the prox­i­mal cen­tri­ole, and a sec­ond cen­tri­ole with atyp­i­cal structure. [10] Mice and rats have no rec­og­niz­able sperm cen­tri­oles. The fruit fly Drosophila melanogaster has a sin­gle cen­tri­ole and an atyp­i­cal cen­tri­ole named the Prox­i­mal Cen­tri­ole-Like (PCL). [36]

The sperm tail is a spe­cial­ized type of cil­ium (aka fla­gella). In many an­i­mals the sperm tail is formed in a unique way, which is named Cy­toso­lic cil­i­o­gen­e­sis , since all or part of ax­oneme of the sperm tail is formed in the cy­to­plasm or get ex­posed to the cytoplasm. [37]

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