sperm

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For more information on sperm, visit Britannica.com.

A mature sperm (spermatozoon) is a complex and highly specialized cell, genetically programmed, and unique in both function and shape. Its production — spermatogenesis — involves cell divisions and reorganization of chromosomal material, which generates genetic diversity. After extensive cell modelling it eventually becomes mobile and capable of penetrating and fertilizing an egg.

Spermatogenesis occurs in the hundreds of seminiferous tubules of the testes, and is dependent on the actions of testosterone produced from cells which lie among these tubules (Leydig cells) and of the gonadotrophic hormones from the pituitary gland. It begins at puberty when the germ cells (spermatogonia), which have been in the testes since fetal life, start dividing by mitosis to produce a small clone of daughter cells with the normal 23 pairs of chromosomes (diploid cells). One of these pairs constitutes the sex chromosomes: in males an X chromosome and a smaller Y chromosome, which carries the male-determining gene. The majority of these cells (now termed primary spermatocytes) push their way through the junctions between the large protective and nourishing cells (Sertoli cells) which lie between them and the lumen of the tubule. In their new environment, created by secretions of the adjacent Sertoli cells, they undergo divisions which halve their number of chromosomes. In the first meiotic division the pairs of chromosomes come together and strands of DNA are swapped between them (crossing over), thus changing the genetic code carried by each chromosome. Eventually the pairs separate and two haploid cells, each containing a single set of 23 chromosomes, are formed. Thus one of these ‘secondary spermaocytes’ contains an X chromosome and the other a Y chromosome. Almost immediately after this first meiotic division a second meiotic division takes place. This involves the separation of the two halves of each single chromosome. These haploid cells — now called spermatids — thus contain 23 single half chromosomes. By this stage the important genetic events have taken place, but these spermatids are still simple round cells and must now undergo extensive remodelling (spermiogenesis) before they are capable of performing their function.

A mature sperm and sections of the testis and seminiferous tubules (S). 1, 2, 3, 4, represent stages of development of spermatogonia to spermatocytes, to spermatids, beside the Sertoli cells (SC). Adapted from Jennett, S. (1989). Human Physiology. Churchill Livingstone, Edinburgh


The first stage is the formation of the acrosome, which is an enzyme-rich structure covering the head of the sperm. This is essential for fertilization. Then a tail develops for forward propulsion and mitochondria (energy generators for the cell) form in the midpiece of the sperm. By now, the work of the Sertoli cells in nurturing the primary spermatocytes through the process of spermatogenesis is complete. As these processes have occurred the developing cells have moved closer and closer to the lumen of the seminiferous tubule. Finally they are extruded and released into the tubule (see figure). In humans this whole process of spermatogenesis takes 64 days.

Once in the lumen of the tubule, the sperm are washed away by secretions from the Sertoli cells, and eventually reach the confluence of all the tubules in the single, highly-convoluted tube of the epididymis, which eventually drains into the vas deferens. The passage of sperm from the seminiferous tubules of the testis to the vas deferens takes about 12 days. During this time the sperm are subjected to major environmental changes due to testosterone-dependent secretions within these tubes. As a result, sperm not only acquire the ability to swim (on leaving the testis they are only capable of an infrequent twitch), but they also change in the way they utilize and break down energy substrates, and finally reach full fertilizing capacity. Sperm obtained before their passage through the epididymis are incapable of fertilizing an egg even if implanted directly.

By the time sperm reach the vas deferens they are fully mature and mobile and, due to fluid absorption in the epididymis, they are now densely packed. In fact 1 ml of fluid in the vas deferens contains about 5000 million sperm. Sperm can be stored for as long as five weeks in the tail of the epididyms and the vas deferens until they are released at ejaculation. In the absence of ejaculation sperm dribble into the urethra and are washed away in the urine. In men who have undergone a vasectomy, sperm build up behind the ligation, and are then removed by phagocytes in the epididymis.

Each sperm produced by the testis is only a few thousandths of a millimetre in length and must travel through some 30-40 cm (100 000 times its own length) in the male and then in the female reproductive tract before it reaches the Fallopian tubes and can perform the function for which it was intended. Needless to say, many fewer than 1 in a million ever complete this hazardous journey.

— Saffron Whitehead

See urogenital system. See also ejaculation; semen; testes.

noun

The male fluid of fertilization: seed, semen. See start/end.

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The male sex cell, typically consisting of a head, midpiece, and tail. (See fertilization.)

Sperm are much smaller than the ova they fertilize.

The male germ cell. See also spermatozoon.

• s. agglutinins — anti-sperm antibodies of the IgG class occur as autoantibodies in dogs infected with Brucella canis.
• s. capacitation — acquisition of the capacity to penetrate an ovum, not present at the time of delivery of the spermatozoon, and which requires a period of incubation in the female tract. It involves increased metabolic activity and motility and the removal of a chemical decapacitation factor from the spermatozoon. Capacitation must take place for the acrosome reaction to occur.
• s. concentration — a sperm count as measured in a hemocytometer; an indication of the health of the relevant testicles and a guide to the prospective fertility of the ejaculate and the donor.
• s. live–dead ratio — an indicator of the viability of the ejaculate as expressed in a slide count of a specially stained smear of the semen in which the dead and live sperm can be distinguished because of their differential staining.
• s. morphology — the normal anatomical structure of the spermatozoon. Abnormality of the structure of individual spermatozoa is used as a guide to the location and nature of the disease causing reduced reproductive efficiency.

  Morphology of normal and abnormal canine spermatozoa. By permission from Nelson RW, Couto CG, Small Animal Internal Medicine, Mosby, 2003

• s. motility — the percentage of spermatozoa moving actively forward. Assessed under the microscope (400 × magnification) or by computerized imaging. See also wave motion; used to predict the probable fertility of the ejaculate.
• s. motility index — half the sum of the sample's sperm percentage motility + sperm progressive motility.
• s. penetration assay — see ovum penetration assay.
• s. stone — hard bodies composed of inspissated masses of spermatozoa found in dilated remnants of epididymal ducts and produced by chronic epididymitis.
• s. transport — within both male and female reproductive tracts some movement forward results from the movements of the spermatozoa but most progress is the result of peristaltic movements by the tubular organs in which the spermatozoa find themselves at the time.

n

Cells contained in the male’s semen that fertilize the female’s egg during the process of conception.

Sperm. (Leonard, 2001, Courtesy Fisher Scientific Company)

For a list of words related to sperm, see:

• Reproduction and Development - sperm: spermatozoon
• Anatomy and Physiology of Sex - sperm: spermatozoon, male seed in semen

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See words rhyming with "sperm."

  See crossword solutions for the clue Sperm.

Dansk (Danish)
1.
n. - sæd, sædvæske, sperma

idioms:

• sperm bank    sædbank
• sperm count    sædtælling

2.
n. - spermacet

idioms:

• sperm whale    kaskelot, spermacethval

Nederlands (Dutch)
sperma, zaadje, product van de potvis

Français (French)
1.
n. - spermatozoïde, sperme

idioms:

• sperm bank    banque de sperme
• sperm count    taux de spermatozoïdes

2.
n. - blanc de baleine, spermaceti

idioms:

• sperm whale    cachalot

Deutsch (German)
1.
n. - Sperma, Samenfaden

idioms:

• sperm bank    Samenbank
• sperm count    Anzahl von Spermien in einem Samenerguß

2.
n. - Spermazet, Walrat

idioms:

• sperm whale    Pottwal

Ελληνική (Greek)
n. - (βιολ.) σπέρμα, (ζωολ.) φυσητήρας ο κατώδους

idioms:

• sperm bank    τράπεζα σπέρματος
• sperm count    αριθμός σπερματοζωαρίων
• sperm whale    (ζωολ.) φυσητήρας ο κατώδους

Italiano (Italian)
sperma

idioms:

• sperm bank    banca del seme
• sperm count    conta spermatica
• sperm whale    capodoglio

Português (Portuguese)
n. - espermatozóide (m), esperma (m), sêmen (m)

idioms:

• sperm bank    banco de esperma (m)
• sperm count    contagem de esperma (m)
• sperm whale    cachalote (m)

Русский (Russian)
сперма, сперматозоид

idioms:

• sperm bank    банк спермы
• sperm count    примерное число сперматозоидов в определенном количестве спермы
• sperm whale    кашалот

Español (Spanish)
1.
n. - esperma

idioms:

• sperm bank    banco de semen, banco de esperma
• sperm count    cuenta de espermatozoides

2.
n. - esperma de ballena

idioms:

• sperm whale    cachalote

Svenska (Swedish)
n. - sperma, sädesvätska, sädescell

中文（简体）(Chinese (Simplified))
精液, 精子, 精虫

idioms:

• sperm bank    提供人工受精用的精子, 精子银行
• sperm count    精子计数
• sperm whale    抹香鲸

中文（繁體）(Chinese (Traditional))
n. - 精液, 精子, 精蟲

idioms:

• sperm bank    提供人工受精用的精子, 精子銀行
• sperm count    精子計數
• sperm whale    抹香鯨

한국어 (Korean)
1.
n. - 정액, 정충, 정자

2.
n. - 경뇌, 경랍, 향유고래기름

日本語 (Japanese)
n. - 精液, 精子

idioms:

• sperm bank    精子銀行
• sperm count    精子数
• sperm whale    マッコウクジラ

العربيه (Arabic)
‏(الاسم) نطفه, مني, السائل المنوي‏

עברית (Hebrew)
n. - ‮זרע, תא-זרע, זירעון‬
n. - ‮דונג העשוי משומן לווייתן הזרע‬

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