# Human sperm diagram

## Brent Cornell

Skill:

•  Annotation of diagrams of mature sperm and egg to indicate functions

The male and female reproductive gametes (sperm and egg) have specialised structures which reflect their functions

• The male gamete (sperm) is small and motile and only contributes the male’s haploid nucleus to the zygote
• The female gamete (egg) is large and non-motile and contributes all the organelles and cytoplasm to the zygote

Sperm

• A typical human spermatozoa can be divided into three sections – head, mid-piece and tail
• The head region contains three structures – a haploid nucleus, an acrosome cap and paired centrioles
• The haploid nucleus contains the paternal DNA (this will combine with maternal DNA if fertilisation is successful)
• The acrosome cap contains hydrolytic enzymes which help the sperm to penetrate the jelly coat of the egg
• The centrioles are needed by a zygote in order to divide (egg cells expel their centrioles within their polar bodies)
• The mid-piece contains high numbers of mitochondria which provide the energy (ATP) needed for the tail to move
• The tail (flagellum) is composed of a microtubule structure called the axoneme, which bends to facilitate movement

Egg

• A typical egg cell is surrounded by two distinct layers – the zone pellucida (jelly coat) and corona radiata
•  The zona pellucida is a glycoprotein matrix which acts as a barrier to sperm entry
• The corona radiata is an external layer of follicular cells which provide support and nourishment to the egg cell
• Within the egg cell are numerous cortical granules, which release their contents upon fertilisation to prevent polyspermy
• Although diagrams of egg cells commonly include a haploid nucleus, no nucleus will form within the egg until after fertilisation has occurred (the egg cell is arrested in metaphase II until it becomes fertilised by a sperm)

Diagram of Human Gametes(click to show / hide labels)

Video of an Unfertilised Human Egg

Sours: http://ib.bioninja.com.au/higher-level/topic-11-animal-physiology/114-sexual-reproduction/egg-and-sperm.html

## Structure of Human Sperm- Definition, Diagram, Structure & Function

Structure of Human Sperm: Do you know how a female egg cell, present at the fallopian tube, gets fertilized by the sperm cell? Do you know how a sperm cell travels all along the female reproductive part to reach the egg cell? The sperm cell has a tail that shows flagellated movement, and it helps it to travel all along the female reproductive tract to reach the egg cell. But where do sperm cells get the energy to move? How does it break protective layers of the egg cell? Know all these in this article below.

### What is the Structure of Human Sperm- Definition

The human sperm cell is the male germ cell that contains a haploid set of chromosomes which, when fused with an egg cell, forms a diploid zygote.

Fig: Human Sperm

Spermatogenesis results in the formation of haploid sperms. Spermatids formed during spermatogenesis undergoes changes during spermiogenesis where a specialized structure is formed called sperm. Two types of sperms are produced, androsperms and gymnosperms, Y and X containing sperms, respectively.

Both are $$50-50$$ percent. If androsperms, i.e., Y containing sperms, are fused with the egg, the resulting offspring would be a boy, while if gymnosperms, i.e., X containing sperms, fuse with the egg, then the resulting offspring would be a girl. The chances of getting a girl offspring or a boy offspring is always $$50\%.$$ Because X containing sperms are $$50\%$$ of the total sperm present and the same for Y containing sperm.

### Structure of Human Sperm- Diagram

Fig: Structure of a sperm cell

### What is the Structure of Sperm?

Human sperm is a microscopic structure whose shape is like a tadpole. It has flagella which makes it motile. Its diameter is $$2 – 5{\rm{ \mu m}},$$ and its length is $$60{\rm{ \mu m}}.$$ It is surrounded by a plasma membrane. It has no nutritive material. It lacks most of the cell organelles like ribosomes, endoplasmic reticulum, etc. The seminal plasma, along with the sperms, constitutes the semen.
The sperm is made up of four parts, namely, head, neck, middle piece, and tail.

Head: It is composed of an acrosome and a nucleus. The shape, size and structure of sperm heads vary greatly in different groups of vertebrates.  The nucleus of the sperm occupies a major part of the head, and its shape ultimately determines the shape of the head of sperm, and a cap-like structure called acrosome is present at the anterior end of the sperm nucleus.

Acrosome, a flattened sac, cap-like structure, lies at the tip of the nucleus. It is formed from the part of the Golgi apparatus of the spermatid. Acrosomal membrane binds acrosome, and it contains certain acrosomal polysaccharides like galactose, mannose, fructose, and hexosamine (Kopency, $$1976$$).

Acrosome consists of hyaluronidase enzyme, corona penetrating enzyme and acrosin. These are collectively called sperm lysin, which has the capacity to dissolve the coverings or cell membranes of the ovum. Corona penetrating enzymes digest the cells of the corona radiata layer. These cells are held together by hyaluronic acid. So, hyaluronidase dissolves this acid and cells are released. Acrosin digests the zona pellucida, a layer of the ovum. These enzymes are therefore secreted during fertilization so that sperm can release its haploid nucleus into the ovum. This dissolution of layers of the egg on the arrival of the sperm is called an acrosomal reaction.

The nucleus lies below the acrosome. In humans, it is flat and oval. It is formed by the condensation of chromatin material and loss of RNA, nucleolus and RNA proteins. The nucleus contains its genetic material in the form of DNA and its associated proteins. The nucleus has become pointed anteriorly, and posteriorly it has a depression.
The complete head part is surrounded by the plasma membrane. The upper half of the nucleus and acrosome is covered by one more membrane inside the plasma membrane called galea. The lower half of the nucleus, the neck region and the middle piece is covered by an extra membrane called Manchette. The galea and manchette are the additional coverings around the sperm.

Neck: This region comprises two centrioles, one proximal centriole and other distal centrioles formed from centrosomes of the spermatid. The Neck region is a small region that has a narrow depression present below the nucleus. Proximal centriole lies at the depression of the posterior part of the nucleus, which is perpendicular to the main axis of the sperm. It is responsible for spindle formation during the first cleavage of the zygote. Distal centriole lies behind the proximal centriole, but its axis is parallel to the longitudinal axis of the sperm. It acts as a basal body and gives rise to the axial filament of the tail of the sperm. Each centriole is a triplet structure and has a $$9+0$$ arrangement.

Middle Piece: After the neck is the middle piece. In the middle piece, spiral ribbon-like mitochondria are arranged called Nebenkern around the axial filament.It is cylindrical in shape and lies behind the neck, and as it is composed of mitochondria and we know mitochondria is the powerhouse of the cell, so it provides energy to the sperm cell for its motility which is essential for fertilization.

Tail: It is the longest part of the sperm. It has an axial filament formed by the distal centriole. It is in a $$9+2$$ pattern. It is the flagellum with which sperm moves forward and reaches the egg for fertilization. Axial filament makes the skeletal structure of the tail. The cytoplasm is almost lost, but very little cytoplasm is present in the tail region.

Viability: The sperms retain the power of fertilizing the egg only for $$24$$ hrs. However, it can live longer, but its capability to fertilize is only for $$24$$ hrs. Human male ejaculate about $$200-300$$ million sperm during coitus, and the average sperm count is between $$40$$ million and $$300$$ million sperm per millilitre.

### What is the Function of Sperm?

Sperm has the following functions-
1. It provides a pronucleus containing the haploid genome to the egg cell, which fuses with the haploid genome of the egg cell and forms a diploid zygote.
2. It delivers centriole, which helps in the formation of centrosomes.
3. It acts as a stimulating factor that activates the dormant oocyte.

### Summary

Sperm is the male germ cell formed by the process of spermatogenesis. Spermatids formed during spermatogenesis undergoes changes during spermiogenesis where a specialized structure is formed called sperm. The sperm consists of the head, neck, middle piece and tail. The head has a nucleus and acrosome. The nucleus consists of genetic material, while the acrosome lying on the nucleus has lytic enzymes.

The Golgi body forms an acrosome. The neck comprises two centrioles, one proximal and the other distal. The middle piece consists of mitochondria in the form of a ribbon. The tail consists of the axial skeleton, and it helps in its movement. Sperm genetic material fuses with the egg genetic material to form a diploid zygote.

### Frequently Asked Questions (FAQs) on Structure of Human Sperm

Q.1. What are the four main parts of a sperm?
Ans:The four main parts of sperm are, Head, Neck, Middle piece and Tail.

Q.2. What is the structure and function of sperm cells?
Ans: Human sperm is a microscopic structure whose shape is like a tadpole. It is a flagellated, microscopic, motile structure that has a head, neck, middle piece and tail. Its main function is to provide genetic material to the egg cell to form a diploid zygote.

Q.3. What is the size of human sperm?
Ans: Sperm’s diameter is $$2 – 5{\rm{ \mu m}},$$ and length is $$60{\rm{ \mu m}},$$

Q.4. How many days can sperm live?
Ans: Sperms retain the power of fertilizing the egg only for $$24$$ hrs. However, it can live longer, even up to $$5$$ days.

Q.5. Do sperm have eyes?
Ans: No, sperms do not have eyes, but it moves towards the egg cell with its tail due to the chemical stimulation from the egg cell.

We hope this detailed article on Structure of Human Sperm helps you in your preparation. If you get stuck do let us know in the comments section below and we will get back to you at the earliest.

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Categories:CBSE (VI - XII), Foundation, foundation1, K12

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## Sperm

### Overview

The male reproductive system creates sperm that is manufactured in the seminiferous tubules within each testicle. The head of the sperm contains the DNA, which when combined with the egg's DNA, will create a new individual. The tip of the sperm head is the portion called the acrosome, which enables the sperm to penetrate the egg. The midpiece contains the mitochondria which supplies the energy the tail needs to move. The tail moves with whip-like movements back and forth to propel the sperm towards the egg. The sperm have to reach the uterus and the fallopian tube in order to fertilize a woman's egg.

Updated by: LaQuita Martinez, MD, Department of Obstetrics and Gynecology, Emory Johns Creek Hospital, Alpharetta, GA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

Sours: https://medlineplus.gov/ency/imagepages/19471.htm
How to draw and label a sperm

## Spermatozoon

Motile sperm cell

A spermatozoon (pronounced , alternate spelling spermatozoön; plural spermatozoa; from Ancient Greek: σπέρμα ("seed") and Ancient Greek: ζῷον ("living being")) is a motilespermcell, or moving form of the haploidcell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.)

Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring (excluding, in most cases, mitochondrial DNA). In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing an X chromosome will lead to a female (XX) offspring, while one bearing a Y chromosome will lead to a male (XY) offspring. Sperm cells were first observed in Antonie van Leeuwenhoek's laboratory in 1677.[1]

Human sperm under microscope

### 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 by 3.1 µm and a tail 50 µm long.[2] The tail flagellates, which propels the sperm cell (at about 1–3 mm/minute in humans) by whipping in an elliptical cone.[3] Sperm have an olfactory guidance mechanism, and after reaching the Fallopian tubes, must undergo a period of capacitation before penetration of the ovum.[4]

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.[5]

Neck: It is the smallest part (3 ×10−8 m), and has a proximal centriole parallel to the base of the nucleus and distal centriole 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.[6]

Tail: It is the longest part (50×10−6 m), having an axial filament surrounded by cytoplasm and plasma membrane, but at the posterior end the axial filament is naked. It is push mechanism.

Semen 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 from the prostate gland dissolves the clot, allowing the sperm to progress optimally.

The spermatozoon is characterized by a minimum of cytoplasm 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.[7]

The specimen contributes with DNA/chromatin, a centriole, and perhaps also an oocyte-activating factor (OAF).[8] It may also contribute with paternal messenger RNA (mRNA), also contributing to embryonic development.[8]

• Electron micrograph of human spermatozoa magnified 3140 times.

• Dimensions of the human sperm head measured from a 39 year-old healthy subject.

The human spermatozoon contains at least 7500 different proteins.[9]

Human sperm genetics has been associated with human evolution, per a 2020 study.[10][11][12]

### DNA damage and repair

DNA damages present in spermatozoa 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 spermatozoa are particularly vulnerable to free radical attack and the generation of oxidative DNA damage.[13][14] (see e.g. 8-Oxo-2'-deoxyguanosine)

Exposure of males to certain lifestyle, environmental or occupational hazards may increase the risk of aneuploid spermatozoa.[15] In particular, risk of aneuploidy is increased by tobacco smoking,[16][17] and occupational exposure to benzene,[18] insecticides,[19][20] and perfluorinated compounds.[21] Increased aneuploidy of spermatozoa often occurs in association with increased DNA damage. DNA fragmentation and increased in situ DNA susceptibility to denaturation, the features similar to these seen during apoptosis of somatic cells, characterize abnormal spermatozoa in cases of male infertility.[22][23]

### Avoidance of immune system response

Glycoprotein 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.[24]

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

Motile sperm cells of algae and seedless plants.

### Animals

Fertilization relies on spermatozoa for most sexually reproductive animals.

Some species of fruit fly produce the largest known spermatozoon found in nature.[25][26]Drosophila melanogaster produces sperm that can be up to 1.8 mm,[27] while its relative Drosophila bifurca produces the largest known spermatozoon, measuring over 58 mm in length.[25] In Drosophila melanogaster, the entire sperm, tail included, gets incorporated into the oocytecytoplasm, however, for Drosophila bifurca only a small portion of the tail enters the oocyte.[28]

The wood mouse Apodemus sylvaticus possesses spermatozoa with falciform morphology. Another characteristic 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.[29]

The postmeiotic phase of mouse spermatogenesis is very sensitive to environmental genotoxic agents, because as male germ cells form mature spermatozoa they progressively lose the ability to repair DNA damage.[30] 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.[31] 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.[32] 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.[33]

The spermatozoa of marsupials are usually longer than those of placental mammals.[34]

### 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. This renders sexual reproduction in the absence of water 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

Main article: Spermatogenesis

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

In ART, 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. These problems are related to several complications in spermatozoa production, for example:

• Hyperspermia: usually provoked because of prostate inflammation.
• Hypospermia: a incomplete ejaculation, usually referred to an androgen's deficit (hypoandrogenism) or obstruction in some part of the ejaculatory tract. 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

Main article: Acrosome reaction

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 (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.[35] 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 calciumionophoresin vitro, progesterone released by nearby cumulus cells and binding to ZP3 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 channels formed by proteins called CatSper. 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 zygote. 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.[36] The IVT diluent is composed of several salts, sugars and antibacterial agents and gassed with CO2.[36]

Semen cryopreservation can be used for far longer storage durations. For human spermatozoa, the longest reported successful storage with this method is 21 years.[37]

### MMP and capacitation

During capacitation, spermatozoa acquire the capability to fertilize the oocyte. In vitro, it happens when the spermatozoa is washed and purified. Nowadays, 20% of the population requires assisted reproductive technology, so it is important for our society development. 15% 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 millilitre) measure is synonymous with capacitation, and is very useful parameter to decide, along with a spermiogram, the kind of treatment needed. 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 millilitre are found, it will be recommended to have sexual intercourse, and if that fails, the next step will be intrauterine insemination and later conventional in vitro fertilisation.

With less than 1.0×106 progressive motile sperm per millilitre, 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 wrote about spermatozoon in his work Untersuchungen über die Bedeutung der Samenfäden (Studies on the importance of spermatozoa).

### References

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20. ^Xia Y, Cheng S, Bian Q, Xu L, Collins MD, Chang HC, Song L, Liu J, Wang S, Wang X (2005). "Genotoxic effects on spermatozoa of carbaryl-exposed workers". Toxicological Sciences. 85 (1): 615–23. doi:10.1093/toxsci/kfi066. PMID 15615886.
21. ^Governini L, Guerranti C, De Leo V, Boschi L, Luddi A, Gori M, Orvieto R, Piomboni P (2014). "Chromosomal aneuploidies and DNA fragmentation of human spermatozoa from patients exposed to perfluorinated compounds". Andrologia. 47 (9): 1012–9. doi:10.1111/and.12371. PMID 25382683. S2CID 13484513.
22. ^Gorczyca, W; Traganos, F; Jesionowska, H; Darzynkiewicz, Z (1993). "Presence of DNA strand breaks and increased sensitivity of DNA in situ to denaturation in abnormal human sperm cells. Analogy to apoptosis of somatic cells". Exp Cell Res. 207 (1): 202–205. doi:10.1006/excr.1993.1182. PMID 8391465.
23. ^Evenson, DP; Darzynkiewicz, Z; Melamed, MR (1980). "Relation of mammalian sperm chromatin heterogeneity to fertility". Science. 210 (4474): 1131–1133. Bibcode:1980Sci...210.1131E. doi:10.1126/science.7444440. PMID 7444440.
24. ^"Sperm clue to 'disease immunity'". BBC News. 2007-12-17.
25. ^ abPitnick, S; Spicer, GS; Markow, TA (11 May 1995). "How long is a giant sperm?". Nature. 375 (6527): 109. Bibcode:1995Natur.375Q.109P. doi:10.1038/375109a0. PMID 7753164. S2CID 4368953.
26. ^Pitnick, S; Markow, TA (27 September 1994). "Large-male advantages associated with costs of sperm production in Drosophila hydei, a species with giant sperm". Proceedings of the National Academy of Sciences of the United States of America. 91 (20): 9277–81. Bibcode:1994PNAS...91.9277P. doi:10.1073/pnas.91.20.9277. PMC 44795. PMID 7937755.
27. ^Cooper, K.W. (1950). Demerec, M. (ed.). Biology of Drosophila. New York: Wiley. pp. 1–61.
28. ^Pitnick, S.; Spicer, G. S.; Markow, T. A. (1995). "How long is a giant sperm". Nature. 375 (6527): 109. Bibcode:1995Natur.375Q.109P. doi:10.1038/375109a0. PMID 7753164. S2CID 4368953.
29. ^Moore, H; Dvoráková, K; Jenkins, N; Breed, W (2002). "Exceptional sperm cooperation in Wood Mouse"(PDF). Nature. 418 (6894): 174–177. Bibcode:2002Natur.418..174M. doi:10.1038/nature00832. PMID 12110888. S2CID 4413444.
30. ^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.
31. ^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.
32. ^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.
33. ^Vacquier, Victor D. (August 2011). "Laboratory on sea urchin fertilization". Molecular Reproduction and Development. 78 (8): 553–564. doi:10.1002/mrd.21360. PMID 21805525.
34. ^Larry Vogelnest; Timothy Portas (1 May 2019). Current Therapy in Medicine of Australian Mammals. Csiro Publishing. ISBN .
35. ^Gnessi L, Fabbri A, Silvestroni L, Moretti C, Fraioli F, Pert CB, Isidori A (1986). "Evidence for the presence of specific receptors for N-formyl chemotactic peptides on human spermatozoa". Journal of Clinical Endocrinology and Metabolism. 63 (4): 841–6. doi:10.1210/jcem-63-4-841. PMID 3018025.
36. ^ abWatson, P. F. (1993). "The potential impact of sperm encapsulation technology on the importance of timing of artificial insemination: A perspective in the light of published work". Reproduction, Fertility and Development. 5 (6): 691–9. doi:10.1071/RD9930691. PMID 9627729.
37. ^Planer NEWS and Press Releases > Child born after 21 year semen storage using Planer controlled rate freezer 14/10/2004

Sours: https://en.wikipedia.org/wiki/Spermatozoon

## Sperm

Male reproductive cell in anisogamous forms of sexual reproduction

For other uses, see Sperm (disambiguation).

Diagram of a human sperm cell

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 totipotentzygote. 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 with 46 paired chromosomes. 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".

Video of human sperm cells under a microscope

### Evolution

Main article: Evolution of sexual reproduction

It is generally accepted that isogamy is the ancestor to sperm and eggs. However, there are no fossil records for the evolution of sperm and eggs from isogamy leading there to be a strong emphasis on mathematical models to understand the evolution of sperm.[4]

A widespread hypothesis states that sperm evolved rapidly. However, there is no direct evidence that sperm evolved at a fast rate or before other male characteristics.[5]

### Sperm in animals

Further information: Spermatozoon

### Function

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 microtubulecytoskeleton.[clarification needed]

### Anatomy

Dimensions of the human sperm head measured from a 39 year-old healthy human subject.

The mammalian sperm cell can be divided in 2 parts:

• Head: contains the nucleus with densely coiled chromatin fibers, surrounded anteriorly by a thin, flattened sac called the acrosome, which contains enzymes used for penetrating the female egg. It also contains vacuoles.[6]
• Tail: also called the flagellum, is the longest part and capable of wave-like motion that propels sperm for swimming and aids in the penetration of the egg.[7][8][9] The tail was formerly thought to move symmetrically in a helical shape.

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]

### Origin

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 quality

Main article: Semen quality

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.

### Sperm size

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]

### Market for human sperm

Further information: Sperm donation

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]

### History

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]

### Forensic analysis

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 in plants

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.[31]

### Motile sperm cells

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).[32]

In nematodes, the sperm cells are amoeboid and crawl, rather than swim, towards the egg cell.[33]

### Non-motile sperm cells

Non-motile sperm cells called spermatia lack flagella and therefore cannot swim. Spermatia are produced in a spermatangium.[32]

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.[32] 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.[34]

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.[35]

### Sperm nuclei

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.[32]

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 syncyticalantheridium surrounding the egg cells. The sperm nuclei reach the eggs through fertilization tubes, similar to the pollen tube mechanism in plants.[32]

### Sperm centrioles

Most sperm cells have centrioles in the sperm neck.[36] 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).[37]

### Sperm tail formation

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.[38]

### References

1. ^"Spermatium definition and meaning | Collins English Dictionary". www.collinsdictionary.com. Retrieved 2020-02-20.
2. ^Kumar, Anil (2006). Botany for Degree Gymnosperm (Multicolor ed.). S. Chand Publishing. p. 261. ISBN .
3. ^"Animal reproductive system - Male systems". Encyclopedia Britannica. Retrieved 2020-02-20.
4. ^Pitnick, Scott S.; Hosken, Dave J.; Birkhead, Tim R. (2008-11-21). Sperm Biology: An Evolutionary Perspective. Academic Press. pp. 43–44. ISBN .
5. ^Fitzpatrick, John L.; Bridge, C. Daisy; Snook, Rhonda R. (2020-08-12). "Repeated evidence that the accelerated evolution of sperm is associated with their fertilization function". Proceedings of the Royal Society B: Biological Sciences. 287 (1932): 20201286. doi:10.1098/rspb.2020.1286. PMC 7575512. PMID 32752988.
6. ^Boitrelle, F; Guthauser, B; Alter, L; Bailly, M; Wainer, R; Vialard, F; Albert, M; Selva, J (2013). "The nature of human sperm head vacuoles: a systematic literature review". Basic Clin Androl. 23: 3. doi:10.1186/2051-4190-23-3. PMC 4346294. PMID 25780567.
7. ^Fawcett, D. W. (1981) Sperm Flagellum. In: The Cell. D. W. Fawcett. Philadelphia, W. B. Saunders Company. 14: pp. 604-640.
8. ^Lehti, M. S. and A. Sironen (2017). "Formation and function of sperm tail structures in association with sperm motility defects." Bi
9. ^Ishijima, Sumio; Oshio, Shigeru; Mohri, Hideo (1986). "Flagellar movement of human spermatozoa". Gamete Research. 13 (3): 185–197. doi:10.1002/mrd.1120130302.
10. ^ abFishman, 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.
11. ^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.
12. ^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 . Retrieved 2013-11-09.
13. ^Semen and sperm quality
14. ^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.
15. ^Cyranoski, David (2016). "Researchers claim to have made artificial mouse sperm in a dish". Nature. doi:10.1038/nature.2016.19453. S2CID 87014225.
16. ^Gurevich, Rachel (2008-06-10). "Does Age Affect Male Fertility?". About.com. Retrieved 14 February 2010.
17. ^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 . PMID 26178844.
18. ^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.
19. ^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.
20. ^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.
21. ^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.
22. ^Gardiner, Jennifer R (2016). "The bigger, the better". Nature. 533 (7604): 476. doi:10.1038/533476a. PMID 27225117.
23. ^Sarfraz Manzoor (2 November 2012). "Come inside: the world's biggest sperm bank". The Guardian. Retrieved 4 August 2013.
24. ^ abcAssisted Reproduction in the Nordic Countries ncbio.org
25. ^ abFDA Rules Block Import of Prized Danish Sperm Posted Aug 13, 08 7:37 AM CDT in World, Science & Health
26. ^ abSteven Kotler (26 September 2007). "The God of Sperm".
27. ^"Timeline: Assisted reproduction and birth control". CBC News. Retrieved 2006-04-06.
28. ^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.
29. ^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.
30. ^
31. ^Phatlane William Mokwala; Phetole Mangena (6 June 2018). Pollination in Plants. BoD – Books on Demand. p. 8. ISBN .
32. ^ abcdefRaven, Peter H.; Ray F. Evert; Susan E. Eichhorn (2005). Biology of Plants, 7th Edition. New York: W.H. Freeman and Company Publishers. ISBN .
33. ^Bottino D, Mogilner A, Roberts T, Stewart M, Oster G (2002). "How nematode sperm crawl". Journal of Cell Science. 115 (Pt 2): 367–84. doi:10.1242/jcs.115.2.367. PMID 11839788.CS1 maint: multiple names: authors list (link)
34. ^Sumbali, Geeta (2005). The Fungi. Alpha Science Int'l Ltd. ISBN .
35. ^Maheshwari R (1999). "Microconidia of Neurospora crassa". Fungal Genetics and Biology. 26 (1): 1–18. doi:10.1006/fgbi.1998.1103. PMID 10072316.
36. ^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.
37. ^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.
38. ^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.

### Sources

• Fawcett, D. W. (1981) Sperm Flagellum. In: The Cell. D. W. Fawcett. Philadelphia, W. B. Saunders Company. 14: pp. 604–640.
• Lehti, M. S. and A. Sironen (2017). "Formation and function of sperm tail structures in association with sperm motility defects." Biol Reprod 97(4): 522–536.

 Wikimedia Commons has media related to Sperm.
Sours: https://en.wikipedia.org/wiki/Sperm
How to draw sperm diagram -- Draw sperm diagram by easy trick -- labbel diagram of sperm --

## Male Reproductive System

All boys are born with a foreskin, a fold of skin at the end of the penis covering the glans. Some boys are circumcised, which means that a doctor or clergy member cuts away the foreskin. Circumcision is usually done during a baby boy's first few days of life. It's not medically necessary, but parents who choose to have their sons circumcised often do so based on religious beliefs, concerns about hygiene, or cultural or social reasons. Boys who have circumcised penises and those who don't are no different: All penises work and feel the same, regardless of whether the foreskin has been removed.

### How Does the Male Reproductive System Work?

The male reproductive system:

• makes semen (SEE-mun)
• releases semen into the reproductive system of the female during sexual intercourse
• produces sex hormones, which help a boy develop into a sexually mature man during puberty

When a baby boy is born, he has all the parts of his reproductive system in place, but it isn't until puberty that he is able to reproduce. When puberty begins, usually between the ages of 9 and 15, the — located near the brain — secretes hormones that stimulate the testicles to produce testosterone. The production of testosterone brings about many physical changes.

Although the timing of these changes is different for every guy, the stages of puberty generally follow a set sequence:

• During the first stage of male puberty, the scrotum and testes grow larger.
• Next, the penis becomes longer and the seminal vesicles and prostate gland grow.
• Hair begins to grow in the pubic area and later on the face and underarms. During this time, a boy's voice also deepens.
• Boys also have a growth spurt during puberty as they reach their adult height and weight.

### What Do Sperm Do?

A male who has reached puberty will produce millions of sperm cells every day. Each sperm is extremely small: only 1/600 of an inch (0.05 millimeters long). Sperm develop in the testicles within a system of tiny tubes called the seminiferous tubules. At birth, these tubules contain simple round cells. During puberty, testosterone and other hormones cause these cells to transform into sperm cells. The cells divide and change until they have a head and short tail, like tadpoles. The head contains genetic material (genes). The sperm move into the epididymis, where they complete their development.

The sperm then move to the vas deferens (VAS DEF-uh-runz), or sperm duct. The seminal vesicles and prostate gland make a whitish fluid called seminal fluid, which mixes with sperm to form semen when a male is sexually stimulated. The penis, which usually hangs limp, becomes hard when a male is sexually excited. Tissues in the penis fill with blood and it becomes stiff and erect (an erection). The rigidity of the erect penis makes it easier to insert into the female's vagina during sex. When the erect penis is stimulated, muscles around the reproductive organs contract and force the semen through the duct system and urethra. Semen is pushed out of the male's body through his urethra — this process is called ejaculation. Each time a guy ejaculates, it can contain up to 500 million sperm.

### What Is Conception?

If semen is ejaculated into a female's vagina, millions of sperm "swim" up from the vagina through the cervix and uterus to meet the egg in the fallopian tube. It takes only one sperm to fertilize the egg.

This fertilized egg is now called a zygote and contains 46 chromosomes — half from the egg and half from the sperm. Genetic material from the male and female combine so that a new individual can be created. The zygote divides again and again as it grows in the female's uterus, maturing over the course of the pregnancy into an embryo, a fetus, and finally a newborn baby.

Sours: https://kidshealth.org/en/parents/male-reproductive.html

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She was not the only one who finished her off. It turned out about five. The wine was chosen very tasty and it was even pleasant to drink. She listened intently to the life stories of her adored classmates and sipped her wine. Everything was going great.

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