A spermatogonium (plural: ''spermatogonia'') is an undifferentiated male

germ cell A germ cell is any cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they unde ...

. Spermatogonia undergo

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

to form mature spermatozoa in the seminiferous tubules of the

testicle A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is Homology (biology), homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of Androgen, androgens, p ...

s. There are three subtypes of spermatogonia in humans: Type A (dark) cells, with dark nuclei. These cells are reserve spermatogonial stem cells which do not usually undergo active mitosis. Type A (pale) cells, with pale nuclei. These are the spermatogonial stem cells that undergo active mitosis. These cells divide to produce Type B cells. Type B cells, which undergo growth and become primary spermatocytes.

Types of spermatogonia

Spermatogonia are often classified into different types depending on their stage in the differentiation process. In humans and most mammals, spermatogonia are divided into two types, A and B, but this can differ for other organisms. There are three subtypes of spermatogonia in humans: *Type A (dark) cells, with dark nuclei. These cells are reserve

spermatogonial stem cell A spermatogonial stem cell (SSC), also known as a type A spermatogonium, is a spermatogonium that does not differentiate into a spermatocyte, a precursor of sperm cells. Instead, they continue dividing into other spermatogonia or remain dormant ...

s which do not usually undergo active

mitosis Mitosis () is a part of the cell cycle in eukaryote, eukaryotic cells in which replicated chromosomes are separated into two new Cell nucleus, nuclei. Cell division by mitosis is an equational division which gives rise to genetically identic ...

. *Type A (pale) cells, with pale nuclei. These are the spermatogonial stem cells that undergo active

. These cells divide to produce Type B cells. *Type B cells, which undergo growth and become primary

spermatocyte Spermatocytes are a type of male gametocyte in animals. They derive from immature germ cells called spermatogonia. They are found in the testis, in a structure known as the seminiferous tubules. There are two types of spermatocytes, primary and s ...

Spermatogenesis

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

is the process in which sperm cells are produced and formed into mature

spermatozoa A spermatozoon (; also spelled spermatozoön; : spermatozoa; ) is a motile sperm cell (biology), cell produced by male animals relying on internal fertilization. A spermatozoon is a moving form of the ploidy, haploid cell (biology), cell that is ...

from spermatogonia. Males mature

(sperm) are produced to later join with a female

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

(egg) to create offspring. Throughout the process of

, there are many different parts of the male anatomy, accessory organs, and

hormones A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physiology and behavior. Hormones a ...

. However,

can be broken down in the following steps, which are initiated at the start of

puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a female, the testicles i ...

: * Spermatogenesis occurs in the germinal epithelium of the seminiferous tubules. Spermatogonia undergo

meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c ...

to produce spermatids that later mature into spermatozoa. The spermatogonia duplicate their DNA to obtain 46 chromosomes in preparation for the primary division. At this stage, the germ cells are now referred to as primary spermatocytes. * The primary spermatocytes undergo a primary division, yielding two secondary spermatocytes each with 23

chromatid A chromatid (Greek ''khrōmat-'' 'color' + ''-id'') is one half of a duplicated chromosome. Before replication, one chromosome is composed of one DNA molecule. In replication, the DNA molecule is copied, and the two molecules are known as chrom ...

s. The secondary spermatocytes then undergo a second division to produce two spermatids, each with 23

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

s. * The spermatids are currently surrounded by Sertoli cells, which nourish the sperm and produce inhibin, an inhibitor of the

follicle-stimulating hormone Follicle-stimulating hormone (FSH) is a gonadotropin, a glycoprotein polypeptide hormone. FSH is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland and regulates the development, growth, puberty, pubertal maturat ...

(FSH). * The last step of spermatogenesis is spermiogenesis. During this process, the spermatids are transformed into spermatozoa, mature sperm. At this point, no other division occurs. The sperm is released from the Sertoli cells and transported to the

epididymis The epididymis (; : epididymides or ) is an elongated tubular genital organ attached to the posterior side of each one of the two male reproductive glands, the testicles. It is a single, narrow, tightly coiled tube in adult humans, in length; ...

through

peristalsis Peristalsis ( , ) is a type of intestinal motility, characterized by symmetry in biology#Radial symmetry, radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an wikt:anterograde, anterograde dir ...

. While in the epididymis, the sperm is stored and begins maturation. Once the sperm has fully matured, it will reach its spermatozoan phase.

Male hormones

Spermatogenesis is a very regulated process controlled by endocrine stimuli. These stimuli include the

(FSH) and the

luteinizing hormone Luteinizing hormone (LH, also known as luteinising hormone, lutropin and sometimes lutrophin) is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by gonadotropin-releasing hormone (G ...

(LH), which stimulate

testosterone Testosterone is the primary male sex hormone and androgen in Male, males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testicles and prostate, as well as promoting se ...

. These hormones produce regulatory signals that control the maintenance and nutrients needed for the developing germ cells. The following explains what each hormone contributes to the regulation of spermatogenesis. *

Gonadotropin-releasing hormone Gonadotropin-releasing hormone (GnRH) is a releasing hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. GnRH is a tropic peptide hormone synthesized and rele ...

(GnRH): Secreted by the

hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...

, GnRH triggers the release of the luteinizing hormone (LH) and follicle-stimulating hormone (FSH). * Follicle-stimulating hormone (FSH): FSH is in charge of stimulating Sertoli cells with testosterone to produce regulatory molecules and nutrients needed for the cells. The nutrients are a needed factor for the maintenance of spermatogenesis. * Luteinizing hormone (LH): LH stimulates Leydig cells to produce testosterone. *

Testosterone Testosterone is the primary male sex hormone and androgen in Male, males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testicles and prostate, as well as promoting se ...

: Testosterone is an important hormone that helps mature sperm through the process and gives rise to male secondary characteristics. * Inhibin: Inhibin is secreted by Sertoli cells. It participates in regulating and inhibiting FSH.

Sperm structure

The overall structure of spermatozoa is very specialized as the cell has fully differentiated and matured. As spermatozoa, the cell no longer undergoes division. It consists of a head, midpiece, and

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

tail for motility. * Head: As the head of the sperm, it is an ovular shape consisting of the nucleus and the acrosome. ** Acrosome: The Acrosome covers two-thirds the head’s outside area; it contains hydrolytic enzymes needed to penetrate the

for

fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise, -ize (-isation, -ization), spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give ...

. ** Nucleus: The nucleus consists of conjugated DNA with

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

. The

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

is tightly compacted with no visible

chromosomes A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most importa ...

. * Midpiece/neck: The midpiece consists of the

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

where ATP is produced. * Tail: The tail consists of a long

flagellum A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

made up of microtubules. It arises during the spermatid stage and allows

motility Motility is the ability of an organism to move independently using metabolism, metabolic energy. This biological concept encompasses movement at various levels, from whole organisms to cells and subcellular components. Motility is observed in ...

Infertility

Infertility In biology, infertility is the inability of a male and female organism to Sexual reproduction, reproduce. It is usually not the natural state of a healthy organism that has reached sexual maturity, so children who have not undergone puberty, whi ...

is the inability of a couple to conceive an offspring after a year of unprotected intercourse. Spermatogonia plays a vital role in male fertility, as they are the initial germ cells for sperm production. A disruption of spermatogonia’s function, structure, or development can lead to infertility. There are several factors that can affect

and the health of spermatogonia, including genetic disorders, hormonal imbalances, environmental factors, and many more.

Diseases that cause infertility

There are many diseases and causes of infertility experienced in males. *

Cystic fibrosis Cystic fibrosis (CF) is a genetic disorder inherited in an autosomal recessive manner that impairs the normal clearance of Sputum, mucus from the lungs, which facilitates the colonization and infection of the lungs by bacteria, notably ''Staphy ...

** Cystic fibrosis is a genetic condition that changes proteins in the body. It causes

mucus Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...

to become thick and sticky leading to blockages and damage as it builds up. ** The vast majority of Men with

cystic fibrosis Cystic fibrosis (CF) is a genetic disorder inherited in an autosomal recessive manner that impairs the normal clearance of Sputum, mucus from the lungs, which facilitates the colonization and infection of the lungs by bacteria, notably ''Staphy ...

suffer from

infertility In biology, infertility is the inability of a male and female organism to Sexual reproduction, reproduce. It is usually not the natural state of a healthy organism that has reached sexual maturity, so children who have not undergone puberty, whi ...

issues. The main cause of infertility is due to obstructive azoospermia (OA). OA is a condition where there is a blockage in a male's reproductive tract, resulting in a lack of sperm in a male's ejaculate. This is mostly due to an absence of the

vas deferens The vas deferens (: vasa deferentia), ductus deferens (: ductūs deferentes), or sperm duct is part of the male reproductive system of many vertebrates. In mammals, spermatozoa are produced in the seminiferous tubules and flow into the epididyma ...

, which is thought to be caused by CFTR mutations. In most males with CF,

does occur, but the males have a lower ejaculate volume. *

Klinefelter syndrome Klinefelter syndrome (KS), also known as 47,XXY, is a chromosome anomaly where a male has an extra X chromosome. These complications commonly include infertility and small, poorly functioning testicles (if present). These symptoms are often n ...

** Klinefelter syndrome is the most common chromosomal abnormality associated with male infertility. Klinefelter's is due to a trisomy of XXY on the 23rd chromosome, giving males an extra X chromosome. The cause of

is related to the replacement of normal testicular architecture with tubular atrophy, sclerosis, or maturation arrest, which degenerates into fibrosis. Cystic fibrosis and Klinefelter syndrome are just two examples of ways diseases and

genetic mutations In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosi ...

can lead to

in men.

Anticancer drugs

Anticancer drugs such as doxorubicin and

vincristine Vincristine, also known as leurocristine and sold under the brand name Oncovin among others, is a chemotherapy medication used to treat a number of types of cancer. This includes acute lymphocytic leukemia, acute myeloid leukemia, Hodgkin lym ...

can adversely affect male fertility by damaging the

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

of proliferative spermatogonial

stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell ...

s. Experimental exposure of rat undifferentiated spermatogonia to doxorubicin and vincristine indicated that these cells are able to respond to DNA damage by increasing their expression of

DNA repair DNA repair is a collection of processes by which a cell (biology), cell identifies and corrects damage to the DNA molecules that encode its genome. A weakened capacity for DNA repair is a risk factor for the development of cancer. DNA is cons ...

genes, and that this response likely partially prevents DNA break accumulation. In addition to a DNA repair response, exposure of spermatogonia to doxorubicin can also induce programmed cell death (

apoptosis Apoptosis (from ) is a form of programmed cell death that occurs in multicellular organisms and in some eukaryotic, single-celled microorganisms such as yeast. Biochemistry, Biochemical events lead to characteristic cell changes (Morphology (biol ...

Additional images

File:Gray1150.png, Transverse section of a tubule of the

testis A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is Homology (biology), homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of Androgen, androgens, p ...

of a

rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include '' Neotoma'' (pack rats), '' Bandicota'' (bandicoo ...

. X 250. File:Spermatocytogenesis.png, Schematic diagram of Spermatocytogenesis Wandimu Geneti

References

{{Male reproductive system Germ cells