Spermatozoa Development

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Human spermatozoa (light microscope)
Human spermatozoa (electron microscope)
Single human spermatozoa[1]

This page introduces spermatogenesis the development of spermatozoa, the male haploid gamete cell. In humans at puberty, spermatozoa are produced by spermatogonia meiosis in the seminiferous tubules of the testis (male gonad). A second process of spermiogenesis leads to change in cellular organisation and shape before release into the central lumen of the seminiferous tubule. This overall process has been variously divided into specific identifiable stages in different species: 6 in human, 12 in mouse, and 14 in rat. Structurally, the seminiferous tubule epithelium is divided into a basal and an apical (adluminal) compartment by the blood–testis barrier (BTB). (More? Testis Development).

A second unique feature of this process is that during mitosis and meiosis the dividing cells remain connected by cytoplasmic bridges as the cells do not complete cytokinesis. This cellular organization is described as a syncytium, only ending with release into the central lumen of the seminiferous tubule, when the cell cytoplasm is discarded. Retinoic acid has been shown to be a key regulator of the development process. (More? Retinoic acid)

In a healthy adult human male it takes about 48 days from meiosis to produce a mature spermatozoa, and he produces somewhere between 45 to 207 million spermatozoa per day, or about 1 to 2,000 every second. (More? Statistics)

History - Spermatozoa Discovery (1677)
Anton van Leeuwenhoek
Anton van Leeuwenhoek (1632 – 1723), was a Dutch scientist who developed the early compound microscope. In 1677 on examination of his own ejaculate under the microscope, he identified tiny “animalcules” he found wriggling inside. He submitted this new observation to the Royal Society London, with the following caveat: “If your Lordship should consider that these observations may disgust or scandalise the learned, I earnestly beg your Lordship to regard them as private and to publish or destroy them as your Lordship sees fit.” Royal Society London 1677.

Fertilization Links: fertilization | oocyte | spermatozoa | meiosis | | ovary | testis | menstrual cycle | zona pellucida | zygote | granulosa cell Lecture - Fertilization | 2016 Lecture | mitosis | Lecture - Week 1 and 2 | hydatidiform mole | Assisted Reproductive Technology | | morula | blastocyst | Lecture - Genital Development | Category:Fertilization
Historic Embryology - Fertilization 
1910 Fertilization | 1919 Human Ovum | 1921 The Ovum | 1927 First polar body | 1929 Oocyte Size | 1943 Fertilization | 1944 In vitro fertilization | 1948 In vitro fertilization

Genital Links: genital | Lecture - Medicine | Lecture - Science | Lecture Movie | Medicine - Practical | primordial germ cell | meiosis | endocrine gonad‎ | Genital Movies | genital abnormalities | Assisted Reproductive Technology | puberty | Category:Genital
Female | X | X inactivation | ovary | corpus luteum | oocyte | uterus | vagina | reproductive cycles | menstrual cycle | Category:Female
Male | Y | SRY | testis | spermatozoa | ductus deferens | penis | prostate | Category:Male
Historic Embryology - Genital 
General: 1901 Urinogenital Tract | 1902 The Uro-Genital System | 1904 Ovary and Testis | 1912 Urinogenital Organ Development | 1914 External Genitalia | 1921 Urogenital Development | 1921 External Genital | 1942 Sex Cords | 1953 Germ Cells | Historic Embryology Papers | Historic Disclaimer
Female: 1904 Ovary and Testis | 1904 Hymen | 1912 Urinogenital Organ Development | 1914 External Genitalia | 1914 Female | 1921 External Genital | 1927 Female Foetus 15 cm | 1927 Vagina | 1932 Postnatal Ovary
Male: 1887-88 Testis | 1904 Ovary and Testis | 1904 Leydig Cells | 1906 Testis vascular | 1909 Prostate | 1912 Prostate | 1914 External Genitalia | 1915 Cowper’s and Bartholin’s Glands | 1920 Wolffian tubules | 1935 Prepuce | 1935 Wolffian Duct | 1942 Sex Cords | 1943 Testes Descent | Historic Embryology Papers | Historic Disclaimer

Medicine Practical | fertilization | Category:Spermatozoa

Some Recent Findings

  • Mechanism of Acrosome Biogenesis in Mammals[2] "During sexual reproduction, two haploid gametes fuse to form the zygote, and the acrosome is essential to this fusion process (fertilization) in animals. The acrosome is a special kind of organelle with a cap-like structure that covers the anterior portion of the head of the spermatozoon. The acrosome is derived from the Golgi apparatus and contains digestive enzymes. With the progress of our understanding of acrosome biogenesis, a number of models have been proposed to address the origin of the acrosome. The acrosome has been regarded as a lysosome-related organelle, and it has been proposed to have originated from the lysosome or the autolysosome. Our review will provide a brief historical overview and highlight recent findings on acrosome biogenesis in mammals."
  • The dynamics and regulation of chromatin remodeling during spermiogenesis[3] "The functional sperm is the key factor for species continuation. The process spermatogenesis, to produce mature sperm is quite complex. It begins with the proliferation and differentiation of spermatogonia, which develop from primary spermatocytes to secondary spermatocytes and round spermatids, which eventually develop into fertile mature sperm. Spermiogenesis is the latest stage of spermatogenesis, where the round spermatids undergo a series of dramatic morphological changes and extreme condensation of chromatin to construct mature sperm with species-specific shape. During spermiogenesis, chromatin remodeling is a unique progress. It leads the nucleosome from a histone-based structure to a mostly protamine-based configuration. The main events of chromatin remodeling are the replacement of histone by histone variants, hyperacetylation, transient DNA strand breaks and repair, variants by transition proteins and finally by protamines. In this review, we synthesize and summarize the current knowledge on the progress of chromatin remodeling during spermiogenesis. We straighten out the chronological order of chromatin remodeling and illustrate the possible regulation mechanisms of each step."
  • Deficiency of fibroblast growth factor 2 (FGF-2) leads to abnormal spermatogenesis and altered sperm physiology[4] "In previous studies, we described the presence of fibroblast growth factor 2 (FGF-2) and its receptors (FGFRs) in human testis and sperm, which are involved in spermatogenesis and in motility regulation. The aim of the present study was to analyze the role of FGF-2 in the maintenance of sperm physiology using FGF-2 knockout (KO) mice. Our results showed that in wild-type (WT) animals, FGF-2 is expressed in germ cells of the seminiferous epithelium, in epithelial cells of the epididymis, and in the flagellum and acrosomal region of epididymal sperm.... Overall, our findings suggest that FGF-2 exerts a role in mammalian spermatogenesis and that the lack of FGF-2 leads to dysregulated sperm production and altered sperm morphology and function. FGF-2-deficient mice constitute a model for the study of the complex mechanisms underlying mammalian spermatogenesis."
  • Small RNAs Are Trafficked from the Epididymis to Developing Mammalian Sperm[5] "The biogenesis of the RNA payload of mature sperm is of great interest, because RNAs delivered to the zygote at fertilization can affect early development. Here, we tested the hypothesis that small RNAs are trafficked to mammalian sperm during the process of post-testicular maturation in the epididymis. By characterizing small RNA dynamics during germ cell maturation in mice, we confirm and extend prior observations that sperm undergo a dramatic switch in the RNA payload from piRNAs to tRNA fragments (tRFs) upon exiting the testis and entering the epididymis. Small RNA delivery to sperm could be recapitulated in vitro by incubating testicular spermatozoa with caput epididymosomes. Finally, tissue-specific metabolic labeling of RNAs in intact mice definitively shows that mature sperm carry RNAs that were originally synthesized in the epididymal epithelium. These data demonstrate that soma-germline RNA transfer occurs in male mammals, most likely via vesicular transport from the epididymis to maturing sperm."
  • Review - Sperm nuclear protamines: A checkpoint to control sperm chromatin quality[6] "Protamines are nuclear proteins which are specifically expressed in haploid male germ cells. Their replacement of histones and binding to DNA is followed by chromatin hypercondensation that protects DNA from negative influences by environmental factors. Mammalian sperm contain two types of protamines: PRM1 and PRM2. While the proportion of the two protamines is highly variable between different species, abnormal ratios within a species are known to be associated with male subfertility. Therefore, it is more than likely that correct protamine expression represents a kind of chromatin checkpoint during sperm development rendering protamines as suitable biomarkers for the estimation of sperm quality. This review presents an overview of our current knowledge on protamines comparing gene and protein structures between different mammalian species with particular consideration given to man, mouse and stallion."
More recent papers  
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This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.

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  • The displayed list of references do not reflect any editorial selection of material based on content or relevance.
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More? References | Discussion Page | Journal Searches | 2019 References | 2020 References

Search term: Spermatozoa Development | Spermatogonia Development | Spermatogonia Stem Cells | Spermatozoa Meiosis | Primary Spermatocyte | Secondary Spermatocyte | Spermatid | Spermatogenesis | Spermiogenesis | Sertoli Cell Development | Spermatozoa Chemotaxis | Acrosome

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.

  • Temporal trends in sperm count- a systematic review and meta-regression analysis[7] " Review Sperm Counts in Western Men May Have Decreased by 50 Percent Over 40 Years. This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50–60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand."
  • Morphometric dimensions of the human sperm head depend on the staining method used.[8] "Different staining techniques change the morphometric dimensions of the human sperm head, probably due to the fact that either the fixatives or stains are not iso-osmotic in relation to human semen."
  • Redistribution of nuclear pores[9] "The appearance of an electron-lucent nuclear region surrounded by the nascent redundant nuclear envelope indicated a pathway for transporting degradation products through the nuclear pores to the residual cytoplasm. The packaging of the nuclear pores into the redundant nuclear envelope suggests that they play a role in late stages of sperm maturation or in fertilization, as most other unnecessary organelles of sperm are discarded during spermiogenesis or during shedding of the cytoplasmic droplet."
  • Calpain modulates capacitation and acrosome reaction[10] "We found that calpain-1 is relocated and translocated from cytoplasm to plasma membrane during capacitation, where it could cleave spectrin, one of the proteins of the plasma membrane-associated cytoskeleton and facilitates acrosome reaction."
  • Spermatocytes cultured in simulated microgravity[11] "A critical step of spermatogenesis is the entry of mitotic spermatogonia into meiosis. Progresses on these topics are hampered by the lack of an in vitro culture system allowing mouse spermatogonia differentiation and entry into meiosis. Previous studies have shown that mouse pachytene spermatocytes cultured in simulated microgravity (SM) undergo a spontaneous meiotic progression. Here we report that mouse mitotic spermatogonia cultured under SM with a rotary cell culture system (RCCS) enter into meiosis in the absence of any added exogenous factor or contact with somatic cells."

Spermatozoa Movies

Human spermatozoa penetrating zona pellucida during fertilisation
Human spermatozoa penetrating the zona pellucida during fertilisation (see Movie).

See also Week 1 movies.

Spermatozoa animation icon.jpg
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Spermatozoa motility icon 01.jpg
 ‎‎Spermatozoa Motility
Page | Play
Spermatozoa chemotaxis icon.jpg
Sperm Chemotaxis
Page | Play
Human fertilization 1 icon.jpg
 ‎‎Fertilisation to
4 Blastomere
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Human fertilization 2 icon.jpg
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Fertilization 002 icon.jpg
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Fertilization 001 icon.jpg
 ‎‎Mouse Fertilisation
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Links: Week 1 movies | Movies

Seminiferous Tubule

Adult Seminiferous tubule showing spermatozoa developmental stages
Seminiferous tubule cross-section and supporting cells
Rat Spermatogenesis cartoon[12]

Seminiferous tubule cartoon.jpg

Seminiferous tubule cartoon[13]

  • Spermatogonia - are the first cells of spermatogenesis
  • Primary spermatocyte - large, enter the prophase of the first meiotic division
  • Secondary spermatocytes - small, complete the second meiotic division
  • Spermatid - immature spermatozoa
  • Spermatozoa - differentiated gamete
Spermatozoa development: primordial germ cell - spermatogonia - primary spermatocyte - Template:Secondary spermatocyte - spermatid - spermatozoa

Links: Testis Histology | testis

Spermatozoa Structure

Mouse- spermatozoa EM and diagram.jpg

Spermatozoa (mouse) cross-sections of tail (EM) and diagram[14]

Other main cell types seen in the histological sections

  • Interstitial cells or Leydig cells - produce hormone
  • Smooth muscle - surround seminiferous tubule and contribute to contraction of the tubule

Human Spermatozoa Development

  • Spermatogenesis process of spermatagonia mature into spermatazoa (sperm).
  • Continuously throughout life occurs in the seminiferous tubules in the male gonad- testis (plural testes).
  • At puberty spermatagonia activate and proliferate (mitosis).
  • about 48 days from entering meiosis until morphologically mature spermatozoa
  • about 64 days to complete spermatogenesis, depending reproduction time of spermatogonia
  • follicle stimulating hormone (FSH) - stimulates the spermatogenic epithelium
  • luteinizing-hormone (LH) - stimulates testosterone production by Leydig cells


In humans at about 2 months of age, primordial germ cells (gonocytes) are replaced by adult dark (Ad) and pale (Ap) spermatogonia forming the spermatogonial stem cell (SSC) population that at puberty will commence differentiation into spermatozoa.

The spermatogonia are the diploid stem cell (spermatogonial stem cell, SSC) progenitor for spermatozoa development. They are located on the basal lamina around the periphery of the seminiferous tubule wall. See this recent spermatogonia review.[15]

In 1963 Clermont identified spermatogonia as Ap (pale) and Ad (dark) on basis of light microscope staining.[16]

  • now also type B
  • 60 years - Ap spermatogonia number decrease
  • 80 years - Ad spermatogonia number decrease
Seminiferous Tubule
Pre-puberty Post-puberty
Testis histology 006.jpg Seminiferous-tubule-HEx40.jpg
Containing only spermatogonia and sertoli cells Containing spermatogonia, sertoli cells and stages of spermatozoa cell meiosis

Mouse spermatogonial self-renewal.jpg Mouse spermatogonia have been shown to require a number of factors to regulate both their spermatogonial self-renewal and differentiation.Zhou Q & Griswold MD. (2008). Regulation of spermatogonia. , , . PMID: 20614596 DOI.

The mouse "As model" originally stated that the As spermatogonia are the SSCs. A more recent proposal suggests that only some of the As spermatogonia have the potential for long-term self-renewal, while others have a limited capacity, indicating the presence of a SSC hierarchy.[15]

In the mouse testis, spermatogonial stem cells can also be identified by Id4 expression[17], a dominant-negative transcription factor containing a basic helix-loop-helix (bHLH) region. Id4 inhibits binding to DNA and transcriptional transactivation by hetero-dimerization with other bHLH proteins.


Spermatozoa maturation involves two processes meiosis and spermiogenesis. After puberty, new spermatozoa continue to be generated throughout life from a spermatogonia stem cell (SSC) population in the testis.

Male gametogenesis.jpg

Primary Spermatocyte

Primary Spermatocyte
Primary Spermatocyte

The first large differentiating diploid (2N) cell before meiosis I, that enters the prophase of the first meiotic division.

Search PubMed: Primary Spermatocyte

Secondary Spermatocyte

The primary spermatocyte forms two second small cells that complete the second meiotic division to be haploid (N) . Histologically difficult to observe, these cells will complete meiosis, forming next the spermatid stage that is the immature morphological state of the spermatozoa.

Search PubMed: Secondary Spermatocyte

Differences in Mammalian Meioses

Female Oogenesis Male Spermatogenesis
Meiosis initiated once in a finite population of cells continuously in mitotically dividing stem cell population
Gametes produced 1 / meiosis 4 / meiosis
Meiosis completed delayed for months or years completed in days or weeks
Meiosis Arrest arrest at 1st meiotic prophase no arrest differentiation proceed continuously
Chromosome Equivalence All chromosomes exhibit equivalent transcription and recombination during meiotic prophase Sex chromosomes excluded from recombination and transcription during first meiotic prophase
Gamete Differentiation occurs while diploid (in first meiotic prophase) occurs while haploid (after meiosis ends)

Links: meiosis


Spermiogenesis is the final stage of spermatogenesis, morphological changes transform the round spermatids into the mature spermatozoa shape and structure.

  1. Nuclear compression - chromatin condensation occurs by the replacement of histones with protamines.
  2. Acrosome formation - located over the anterior part of the spermatid nucleus, cap-like membrane-bound organelle formed through coalescence of the coated vesicles budding from the trans-Golgi network. The acrosome-acroplaxome-manchette complex is a major driver for the shaping of the spermatozoa head.
  3. Tail development - located over the posterior part of the spermatid nucleus, initially a centriole pair moves, the axoneme develops from the distal centriole. Axoneme consists of a central pair of microtubules surrounded by 9 outer doublet microtubules ("9 × 2 + 2").
  4. Cytoplasm disposal - cytoplasm transported towards the tail along the manchette and finally its removal.

Other Features

  • Nuclear pore redistribution - with packaging of the nuclear pores into the redundant and discarded nuclear envelope. [9]
  • Autophagy - a self-digestion process, may also occur regulating cytoskeleton reorganization.[18][19]

Sertoli Cell

Histology Sertoli cell
Sertoli cells

The sertoli cell was named after Enrico Sertoli (1842 - 1910) an Italian (Milan) physiologist and histologist. These cells support spermatozoa development and span the wall of the seminiferous tubule.

  • sustentacular cells of seminiferous tubules.
  • form a “blood-testis” barrier through junctional complexes
  • separate the intra-tubular germinal epithelium into two compartments
  1. basal compartment - cells are exposed to the extra-tubular environment
  2. luminal compartment - cells are subject to an environment produced by Sertoli cells and germ cells

During infancy and childhood, sertoli cells are the most active cell population in the seminiferous tubule producing AMH from fetal period until mid-puberty.[20]

Links: sertoli cell | AMH

Spermatogenic Cycle

Along the length of the seminiferous tubule spermatozoa develop in a cyclic manner over time progressing through a number of stages, called the spermatogenic cycle, see review.[21] The number of stages appears to differ between species, in mouse there are 12 stages (I – XII) and in the rat 14 stages.

In mouse, one spermatogenic cycle (12 stages) occurs over 8.6 days and four cycles (35 days) are required from spermatogonial stem cell to released spermatozoa.



Spermatozoa Structure

Mouse- spermatozoa EM and diagram.jpg

Spermatozoa (mouse) cross-sections of tail (EM) and diagram[14]


This structure forms the acrosome plate with intermediate filament bundles of the marginal ring at the leading edge of the acrosome. The acroplaxome site for Golgi-derived proacrosomal vesicles to tether and fuse and anchors the developing acrosome to the elongating spermatid head and may provide a scaffolding for the shaping of the spermatid nucleus.[24]


Derived from the Golgi apparatus in conjunction with transient specialized bundles of microtubules (Template:Manchette), this vesicle releases its contents following progesterone stimulus or zona pellucida binding.

Acrosome Reaction

The "acrosome reaction" (AR) a type of specialised exocytosis, or similar to the release of an exosome.[25] This also leads to changes in the spermatozoa membrane. The 26S proteasome[26], has been identified from in vitro studies to be required for zona lysin in many species, including mammals.[27]

  • Calcium ion permeability - Ca(2+) release from the acrosome leads to exocytosis of the acrosomal vesicle[28], alkalization appears to be a critical step.[29]
    • store-operated Ca(2+) channels and voltage-dependent Ca(2+) channels
  • Vesicle membrane - initially holding excreting molecules, remains on the cell surface
  • Membrane loss - both outer acrosomal membrane and plasma membrane are lost by forming vesicles during acrosome reaction.

Acrosome reaction has a slow and rapid component:[30]

  1. Rapid - (seconds) efflux of calcium from intracellular stores, triggers fusion pores opening and the release of hybrid vesicles.
  2. Slow - (minutes) acrosomal swelling, triggered by activation of an adenylyl cyclase downstream of the opening of store-operated calcium channels. Determines the kinetics of the acrosome reaction.

  • Exosomes - extracellular vesicles that are released from cells upon fusion of an intermediate endocytic compartment, the multivesicular body (MVB), with the plasma membrane.
  • Proteasomes - protein complexes which typically degrade unneeded or damaged proteins by proteolysis.


  • Acrosin is essential for sperm penetration through the zona pellucida in hamsters PNAS February 4, 2020 117 (5) 2513-2518 "Mammalian oocytes are surrounded by the zona pellucida, a glycoprotein coat that protects the oocyte and embryo from mechanical damage during their preimplantation development within the oviduct. Fertilizing spermatozoa must penetrate the zona, but we do not know the exact mechanisms underlying this process. Sperm proteases were thought to work as zona lysins, but gene-knockout studies in mice did not support this assumption. In this study, we generated hamsters without acrosin, the major acrosomal protease, to examine its role in both in vivo and in vitro fertilization. Surprisingly, mutant male hamsters were completely infertile because their spermatozoa were unable to penetrate the zona. We thus demonstrated that, at least in hamsters, acrosin is essential for sperm penetration through the zona."

Human acrosin - 22q13.33

Links: OMIM - Acrosin


The spermatozoa nucleus undergoes extensive compression, and nuclear DNA chromatin remodelling by tightly packing with spermatozoa-specific protamines.[31]

It is thought that the lysine-rich protein precursor (H1 histone) has evolved into the arginine-rich protamines.[32] Three major spermatozoa nuclear basic proteins types:
  1. histone type (H-type)
  2. protamine-like type (PL-type)
  3. protamine type (P-type)
EM Human Spermatozoa Nucleus
Human spermatid EM01.jpg Human spermatid EM02.jpg
Cap-phase spermatid nucleus[33] Elongated spermatid nucleus[33]
Human spermatozoa nucleus EM01.jpg Human spermatozoa nucleus EM03.jpg
Normal human spermatozoa[34] Abnormal human spermatozoa[34]


The stable mature microtubule-containing tail of the sperm.

Spermatozoa tail EM01.jpg Mouse- spermatozoa EM and diagram.jpg
Historic EM spermatozoon tail Mouse cross-sections of tail[14]


Spermatozoa initially contains 2 centrioles (proximal, distal) and at fertilisation only a single (proximal) is present, which in most mammalian species is contributed to reconstitute the zygotic centrosome. Note that in rodents (rat, mice) both centrioles are lost and only a maternal centrosomal inheritance occurs.

  • distal centriole - (perpendicular to membrane) required as the basal body generating the microtubule axoneme and is then lost (disintegration).
  • proximal centriole - required after fertilisation for decondensing spermatozoa nucleus allowing development into the male pronucleus.


A transient microtubule structure formed in spermatids involved in the process of: assembly of the mammalian sperm tail, mechanical shaping and condensation of the sperm nucleus. These microtubules are also invloved with specific transport, intramanchette transport, which has been likened to intraflagellar transport. This microtubular structure surrounds the nucleus of the developing spermatid and is thought also to assist in both the reshaping of the nucleus and redistribution of spermatid cytoplasm.


Contained in the initial segment provide the energy for motility and may also enter the egg on fertilization, but are eliminated by a ubiquitin-dependent mechanism.

Perinuclear Theca

Located in the sperm head perinuclear region and contains a cytoskeletal element to maintain the shape of the sperm head and functional molecules leading to oocyte activation during fertilization.

Mature Human Spermatozoa

Spermatozoa animation icon.jpg Features:
  • 60 µm long, actively motile
  • divided into 3 main regions (head, neck and tail)
  • head - (flattened, 5 µm long by 3 µm wide) the nucleus and acrosome. Posterior part of nuclear membrane forms the basal plate.
  • neck - (1 µm) attached to basal plate, transverse oriented centriole, contains nine segmented columns of fibrous material, continue as outer dense fibres in tail.
  • tail - 3 parts a middle piece, principal piece and end piece
    • middle piece - (5 µm long) axonema and dense fibres surrounded by mitochondria
    • principal piece - (45 µm long) fibrous sheath interconnected by regularly spaced circumferential hoops
    • end piece - (5 µm long) axonema surrounded by small amount of cytoplasm and plasma membrane

Human Spermatazoa Statistics | Development Animation - Spermatozoa

Human Spermatozoa Statistics

Male Testis

Normal Human Reproductive Male (between 20 to 50 years)
Spermatozoa Number/Time
produced / day (two testes) 45 to 207 million
  compare adult human red blood cell / day 250,000 million
produced / second each day (approx) 2,000
stored (epididymal reserves) up to per epididymis 182 million
stored extragonadal 440 million
extragonadal - ductuli deferentia and caudae epididymides per ejaculation 225 million
Transit Times
through the caput 0.72 day
through the corpus 0.71 days
through the cauda epididymidis 1.76 days
  Table Data [35]   See also WHO human semen reference values(2010).[36]   Links: spermatozoa

Spermatozoa Morphology

Morphology is a term used to describe the overall appearance of a cell or tissue and is often used to characterise changes in cellular state or activity. Historically, there have been studies comparing the overall appearance of spermatozoa between different species.[37] More recently, there have been several different ways of characterising the morphology of human spermatozoa developed mainly in relation to clinical reproductive technologies.

Integrated Sperm Analysis System (ISAS)

A semi-automated computer-aided system that measures spermatozoa head parameters length (L), width (W), area (A), perimeter (P), acrosomal area (Ac), and the derived values L/W and P/A.[38]

  • For each man a homogeneous population of distributions characterized seminal spermatozoa (7,942 cells: median values L 4.4 μm, W 2.8 μm, A 9.8 μm(2), P 12.5 μm, Ac 47.5%, L/W 1.57, P/A 1.27)
  • Different men could have spermatozoa of significantly different dimensions.
  • Head dimensions for swim-up spermatozoa from different men (4 812 cells) were similar to those in semen, differing only by 2%-5%.
  • The values of L, W and L/W fell within the limits given by the World Health Organization (WHO).
  • A subpopulation of 404 spermatozoa considered to fit the stringent criteria of WHO 'normal' seminal spermatozoa[36] from both semen and swim-up were characterized by median values (and 95% confidence intervals) of L, 4.3 μm (3.8-4.9), W, 2.9 μm (2.6-3.3), A, 10.2 μm(2) (8.5-12.2), P, 12.4 μm (11.3-13.9), Ac, 49% (36-60), L/W, 1.49 (1.32-1.67) and P/A, 1.22 (1.11-1.35). These median values fall within the 95th centile confidence limits given by WHO, but the confidence intervals for L and W were larger.

Spermatozoa Chemotaxis

Chemotaxis was first identified in marine species[39], which still remains today as a model system. While the signals may differ, the overall effect is to chemically attack spermatozoa to the oocyte to allow fertilisation to occur.

The following series of 2011 research articles have identified the spermatozoa calcium channel protein (CatSper) as the progesterone activated pathway involved in capacitated spermatozoa chemotaxis.
  • The CatSper channel mediates progesterone-induced Ca2+ influx in human sperm[40]
  • Progesterone activates the principal Ca2+ channel of human sperm[41]
  • Spermatozoa hyperactivated motility[42]
    • part of the chemotactic response of human spermatozoa.
    • initiated by elevation of intracellular Ca2+
    • non-linear with increased velocity and a large amplitude of lateral head displacement
    • intense flagellar whiplash movements.
Spermatozoa chemotaxis icon.jpg
Sperm Chemotaxis
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Human spermatozoa chemotaxis labeled model.jpg

Human Spermatozoa Chemotaxis Model (2009)[43]

See also 2008 review.[44]

Sertoli Cell

The sertoli cells are the first cells to be differentiated in development by SRY expression. Post-puberty these are the "support" cells for spermatozoa development and transport from the periphery to lumen of the seminiferous tubule. Sertoli cells form a barrier with cell junctions at the Sertoli cell-cell and Sertoli-germ cell interface.

Sertoli cell postnatal proliferation may be regulated by thyroid status. An animal model study of postnatal transient hypothyroidism has demonstrated Sertoli cell proliferation (6 to 8 fold increase) 2 days after the diet switch and remained elevated the next days.[45]


Papanicolaou stain (Papanicolaou's stain, Pap stain) a multichromatic (five dyes) staining histological technique developed by George Papanikolaou, used to differentiate cells in smear preparations of various bodily secretions.

Links: sertoli cell | Testis Histology | Histology Stains | Search PubMed - Sertoli Cell Development

Male Abnormalities

Male Infertility Genes

Examples of known genes resulting in various forms of male infertility.

Selected genes in Male Infertility
Gene abbreviation Name Gene Location Online Mendelian
Inheritance in Man (OMIM)
HUGO Gene Nomenclature
Committee (HGNC)
GeneCards (GCID) Diagnosis
AURKC Aurora kinase C 19q13.43 603495 11391 GC19P057230 Macrozoospermia
CATSPER1 Cation channel sperm-associated 1 11q13.1 606389 17116 GC11M066034 Asthenozoospermia
CFTR Cystic fibrosis transmembrane conductance regulator 7q31.2 602421 1884 GC07P117465 Obstructive azoospermia
DNAH1 Dynein axonemal heavy chain 1 3p21.1 603332 2940 GC03P052350 Asthenozoospermia
DPY19L2 Dpy-19-like 2 gene 12q14.2 613893 19414 GC12M063558 Globozoospermia
GALNTL5 Polypeptide N-acetylgalactosaminyltransferase-like 5 7q36.1 615133 21725 GC07P151956 Asthenozoospermia
MAGEB4 MAGE family member B4 Xp21.2 300153 6811 GC0XP030260 Azoospermia
NANOS1 Nanos C2HC-type zinc finger 1 10q26.11 608226 23044 GC10P119029 Azoospermia
NR0B1 Nuclear receptor subfamily 0 group B member 1 Xp21.2 300473 7960 GC0XM030322 Azoospermia
NR5A1 Nuclear receptor subfamily 5 group A member 1 9q33.3 184757 7983 GC09M124481 Azoospermia
SOHLH1 Spermatogenesis and oogenesis-specific basic helix–loop–helix 1 9q34.3 610224 27845 C09M135693 Azoospermia
vSPATA16 Spermatogenesis-associated 16 3q26.31 609856 29935 GC03M172889 Globozoospermia
SYCE1 Synaptonemal complex central element protein 1 10q26.3 611486 28852 GC10M133553 Azoospermia
TAF4B TATA-box binding protein-associated factor 4b 18q11.2 601689 11538 GC18P026225 Azoospermia
TEX11 Testis expressed 11 Xq13.1 300311 11733 GC0XM070528 Azoospermia
TEX15 Testis expressed 15, meiosis and synapsis associated 8p12 605795 11738 GC08M030808 Azoospermia
WT1 Wilms tumour 1 8p12 607102 12796 GC11M032365 Azoospermia
ZMYND15 Zinc-finger MYND-type containing 15 17p13.2 614312 20997 GC17P004740 Azoospermia
  Table data source[46] (table 1)    Links: fertilization | spermatozoa | testis | Male Infertility Genes | Female Infertility Genes | oocyte | ovary | Genetic Abnormalities | ART

  Asthenozoospermia - (asthenospermia) term for reduced spermatozoa motility. Azoospermia - term for no spermatozoa located in the ejaculate. Globozoospermia - term for spermatozoa with a round head and no acrosome.

Human Seminiferious Tubule - Non-obstructive azoospermia and Obstructive azoospermia

Human sperm pathologies EM01.jpg

Human sperm pathologies[47] These electron micrographs show a range of tail structural abnormalities including (a) two tails. (b) shows a normal spermatozoa tail cross-section and c to g show a range of abnormal tail structures (open image to see details).

Johnsen score

A clinical score (1-10) for assessing spermatogenesis in a human testicular biopsy. Named after the author of the original article .[48]

10 complete spermatogenesis and perfect tubules
9 many spermatozoa present but disorganized spermatogenesis
8 only a few spermatozoa present
7 no spermatozoa but many spermatids present
6 only a few spermatids present
5 no spermatozoa or spermatids present but many spermatocytes present
4 only a few spermatocytes present
3 only spermatogonia present
2 no germ cells present
1 neither germ cells nor Sertoli cells present

Reference: Johnsen SG. Testicular biopsy score count - a method for registration of spermatogenesis in human testes: normal values and results in 335 hypogonadal males. (1970) Hormones 1(1): 2-25. PubMed 5527187

Classification Count (Millions/mL)
Azoospermia 0
Severe oligozoospermia less than 1
Moderate oligozoospermia 1-5
Mild oligozoospermia 5-20
Normal greater than 20


(Low Sperm Count) less than 20 million sperm after 72 hour abstinence from sex


(Absent Sperm) blockage of duct network

Immotile Cilia Syndrome

Lack of sperm motility

Acephalic spermatozoa syndrome

Acephalic spermatozoa syndrome is characterized by the presence of very few intact spermatozoa and tailless sperm heads in the semen and leads to severe male infertility. Sad1 and UNC84 domain-containing 5 (SUN5) is a testis-specific nuclear envelope protein. A recent study has shown that mutations in SUN5 appear to affect the secondary structure of the protein and influence its folding and cellular localization.[49]

Links: OMIM - SUN5

Infertility - Stem Cells

Recent studies have been able to transplant of own cryostored spermatogonial stem cells (SSCs) is a promising technique for fertility restoration when the SSC pool has been depleted.[50]

Additional Images


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  • Spermatogenesis | PubMed - Spermatogenesis "Spermatogenesis is a new quarterly, peer-reviewed journal that will publish high-quality articles covering all aspects of spermatogenesis." Note last PubMed entries for this journal in 2016.
  • WHO. WHO Laboratory Manual for the Examination and Processing of Human Semen. 5th ed. Geneva, Switzerland: World Health Organization; 2010. Online PDF


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Griswold MD. (2016). Spermatogenesis: The Commitment to Meiosis. Physiol. Rev. , 96, 1-17. PMID: 26537427 DOI.

Talwar P & Hayatnagarkar S. (2015). Sperm function test. J Hum Reprod Sci , 8, 61-9. PMID: 26157295 DOI.

Yoshida S. (2010). Stem cells in mammalian spermatogenesis. Dev. Growth Differ. , 52, 311-7. PMID: 20388168 DOI.

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Ruwanpura SM, McLachlan RI & Meachem SJ. (2010). Hormonal regulation of male germ cell development. J. Endocrinol. , 205, 117-31. PMID: 20144980 DOI.

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NCBI Bookshelf

MBoC - Sperm | MBoC - Highly simplified drawing of a cross-section of a seminiferous tubule in a mammalian testis | MBoC - Cytoplasmic bridges in developing sperm cells and their precursors



Spermatozoa Development (expand to see terms)  

Spermatozoa Development

Note there are additional glossaries associated with genital, spermatozoa, oocyte and renal.

  • acroplaxome - structure forms the acrosome plate with intermediate filament bundles of the marginal ring at the leading edge of the acrosome. The sub-acrosomal layer located in the developing spermatozoa head perinuclear region, located between the inner acrosomal membrane and the nuclear envelope. The other part of the perinuclear region is the post-acrosomal sheath (PAS) at the post-acrosomal region.
  • acrosome - Cap-shaped cellular structure formed from the golgi apparatus and contains enzymes to dissolve the oocyte (egg) zona pellucida for fertilisation.
  • acrosome compaction - Acrosome reshaping process in final stages of spermatogenesis (spermatid to spermatozoa).
  • acrosome reaction - Chemical change within the spermatozoa following binding to the zona pellucida, only acrosome reacted spermatozoa have an ability to fuse with oocytes.
  • annulus - Cytoskeletal (septin) structure located between the midpiece and principal piece regions of the tail, thought to form a diffusion barrier between these two domains. PMID 20042538
  • asthenozoospermia - (asthenospermia) Term for reduced sperm motility and can be the cause of male infertility.
  • axoneme - (axonema) The basic structure in cilia and eukaryotic flagella and in the spermatozoa tail, consisting of parallel microtubules in a characteristic "9 + 2" pattern. This pattern describes 9 outer microtubule doublets (pairs) surrounding 2 central singlet microtubules, in humans 50 μm long. The motor protein dynenin move the outer microtubules with respect to the central pair, bending the cilia and generating motility. Note that prokaryotic bacteria have a similar process (flagellum) that uses an entirely different mechanism for motility.
  • capacitation - term describing the process by which spermaozoa become capable of fertilizing an oocyte, requires membrane changes, removal of surface glycoproteins and increased motility.
  • caput - proximal head of the epididymis, epithelium with stereocilia, involved in absorbing fluid to concentrate spermatozoa. Underlying smooth muscle aids movement. Epididymis three main parts : caput (head), corpus (body), cauda (tail).
  • CatSper - cationic (Ca2+) channel of spermatozoa, progesterone activated involved in hyperactivation, acrosome reaction, and possibly chemotaxis.
  • cauda - distal tail of the epididymis, region with a thin epithelium and the greatest quantity of smooth muscle. Epididymis three main parts : caput (head), corpus (body), cauda (tail).
  • centriole - a microtubule organising centre. First required for axoneme formation (distal centriole) that is lost and a second for pronuclei formation (proximal) following fertilisation. Rodents loose both and only have maternal centrioles.
  • connecting piece - linkage between the spermatozoa head and the midpiece of the tail. PMID 22767409
  • corpus - elongated body of the epididymis, This has an intermediate thickness of epithelium and thicker smooth muscle layer than caput. Epididymis three main parts : caput (head), corpus (body), cauda (tail).
  • cytoplasmic bridges - Transient cytoplasm connections between spermatids arising from one spermatogonium due to incomplete cytokinesis.
  • diploid - (Greek, di = double + ploion = vessel) Having two sets of chromosomes, the normal state for all cells other than the gametes.
  • end piece - Last portion of the spermatozoa tail region.
  • epididymis - testis tubular structure connecting the efferent ducts to the ductus deferent and functions for the storage and maturation of spermatozoa. Epididymis three main parts : caput (head), corpus (body), cauda (tail). PMID27307387
  • fibrous sheath - cytoskeletal structure surrounding the axoneme and outer dense fibers, defining the extent of the principal piece region.
  • haploid - (Greek, haploos = single) Having a single set of chromosomes as in mature germ/sex cells (oocyte, spermatozoa) following reductive cell division by meiosis. Normally cells are diploid, containing 2 sets of chromosomes.
  • interstitial cell - (Leydig cell) Male gonad (testis) cell which secrete the androgen testosterone, beginning in the fetus.
  • interstitium - testis developmental region (space between testis cords) that generates Leydig cells and other less well characterized cell types.
  • Johnsen score - a clinical score (1-10) for assessing spermatogenesis in a human testicular biopsy. Named after the author of the original article. PMID 5527187
  • Leydig cell - (interstitial cell) Male gonad (testis) cell that secrete the androgen testosterone, beginning in the fetus. Fetal Leydig cells develop from coelomic epithelium and undifferentiated perivascular cells in the gonad–mesonephros border region. Adult Leydig cells appear after birth from stem/progenitor cells among peritubular and peri-vascular cells. Leydig cells were first histologically identified in 1850 by Franz von Leydig (1821 - 1908) a German scientist.
  • meiosis - The cell division that occurs only in production of germ cells where there is a reduction in the number of chromosomes (diploid to haploid) which is the basis of sexual reproduction. All other non-germ cells in the body divide by mitosis.
  • midpiece - (middle piece) spermatozoa tail initial segment of axoneme surrounded outer dense fibres then by mitochondria. Next in the tail is the principal piece then finally the end piece.
  • mitosis - The normal division of all cells, except germ cells, where chromosome number is maintained (diploid). In germ cell division (oocyte, spermatozoa) meiosis is a modified form of this division resulting in reduction in genetic content (haploid). Mitosis, division of the nucleus, is followed by cytokinesis the division of the cell cytoplasm and the cytoplasmic contents. cytokinesis overlaps with telophase.
  • outer dense fibres - (ODF, outer dense fibers) cytoskeletal structures that surround the axoneme in the middle piece and principal piece of the spermatozoa tail.
  • primary spermatocyte - arranged in the seminiferous tubule wall deep (luminal) to the spermatogonia. These large cells enter the prophase of the first meiotic division. (More? meiosis)
  • principal piece - Spermatozoa tail segment containing the plasma membrane calcium channels (CatSper1 and CatSper2) required for hyperactivation of motility. Region is partially separated from the midpiece by a barrier called the annulus.
  • sertoli cells - (sustentacular cell) These cells are the spermatozoa supporting cells, nutritional and mechanical, as well as forming a blood-testis barrier. The cell cytoplasm spans all layers of the seminiferous tubule. The cells are named after Enrico Sertoli (1842 - 1910), and italian physiologist and histologist.
  • sperm annulus - (Jensen's ring; Latin, annulus = ring) A region of the mammalian sperm flagellum connecting the midpiece and the principal piece. The annulus is a septin-based structure formed from SEPT1, 4, 6, 7 and 12. Septins are polymerizing GTPases that can act as a scaffold forming hetero-oligomeric filaments required for cytokinesis and other cell cycle roles.
  • spermatogenesis - (Greek, genesis = origin, creation, generation) The term used to describe the process of diploid spermatagonia division and differentiation to form haploid spermatazoa within the testis (male gonad). The process includes the following cellular changes: meiosis, reoorganization of DNA, reduction in DNA content, reorganization of cellular organelles, morphological changes (cell shape). The final process of change in cell shape is also called spermiogenesis.
  • spermatogenesis - (Greek, genesis = origin, creation, generation) The maturation process of the already haploid spermatazoa into the mature sperm shape and organization. This process involves reorganization of cellular organelles (endoplasmic reticulum, golgi apparatus, mitochondria), cytoskeletal changes (microtubule organization) and morphological changes (cell shape, acrosome and tail formation).
  • spermatogonia - The cells located in the seminiferous tubule adjacent to the basal membrane that either divide and separate to renew the stem cell population, or they divide and stay together as a pair (Apr spermatogonia) connected by an intercellular cytoplasmic bridge to differentiate and eventually form spermatazoa.
  • spermatozoa head - Following spermiogenesis, the first region of the spermatozoa containing the haploid nucleus and acrosome. In humans, it is a flattened structure (5 µm long by 3 µm wide) with the posterior part of nuclear membrane forming the basal plate region. The human spermatozoa is about 60 µm long, actively motile and divided into 3 main regions (head, neck and spermatozoa tail).
  • spermatozoa neck - Following spermiogenesis, the second region of the spermatozoa attached to basal plate, transverse oriented centriole, contains nine segmented columns of fibrous material, continue as outer dense fibres in tail. In humans, it forms a short structure (1 µm). The human spermatozoa is about 60 µm long, actively motile and divided into 3 main regions (head, neck and tail).
  • spermatozoa tail - Following spermiogenesis, the third region of the spermatozoa that has a head, neck and tail). The tail is also divided into 3 structural regions a middle piece, a principal piece and an end piece. In humans: the middle piece (5 µm long) is formed by axonema and dense fibres surrounded by mitochondria; the principal piece (45 µm long) fibrous sheath interconnected by regularly spaced circumferential hoops; the final end piece (5 µm long) has an axonema surrounded by small amount of cytoplasm and plasma membrane.
  • spermatogonial stem cells - (SSCs) The spermatagonia cells located beside the seminiferous tubule basal membrane that either divide and separate to renew the stem cell population, or they divide and stay together as a pair (|Apr spermatogonia) connected by an intercellular cytoplasmic bridge to differentiate and eventually form spermatazoa.
  • spermatozoon - singular form of of spermatozoa.
  • sperm protein 56 - A component of the spermatozoa acrosomal matrix released to the sperm surface during capacitation.
  • teratospermia - Clinical term for a spermatozoa with abnormal morphology (small, large, defects in the head, tail, and/or mid-piece) present in the semen or ejaculate.
  • testis cords - developmental structure that give rise to the adult seminiferous tubules, the other developmental region is the interstitium.
  • vasectomy - Clinical term for ligation of the scrotal portion of the ductus deferens.

See also: Spermatozoa Terms collapse table

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  • World Health Organization - WHO Laboratory Manual for the Examination and Processing of Human Semen. 5th ed. Geneva, Switzerland: World Health Organization; 2010. Online PDF

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Cite this page: Hill, M.A. (2024, June 16) Embryology Spermatozoa Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Spermatozoa_Development

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G