Spermiogenesis

Spermiogenesis is the final stage of spermatogenesis which sees the maturation of spermatids into mature, motile spermatozoa.

Phases

The process of spermiogenesis is traditionally divided into four stages: the Golgi phase, the cap phase, the acrosomal phase, and the maturation stage.[1]

Golgi phase

The spermatids, which up until now have been mostly radially symmetrical, begins to develop polarity. Spermatid DNA also undergoes packaging, becoming highly condensed. The DNA is packaged firstly with specific nuclear basic proteins, which are subsequently replaced with protamines during spermatid elongation. The resultant tightly packed chromatin is transcriptionally inactive.

Cap phase

The Golgi apparatus surrounds the now condensed nucleus, becoming the acrosomal cap.

Enlarge picture
Note how the tails of the sperm point inward. This orientation occurs during the acrosomal phase.

Acrosomal phase

One of the centrioles of the cell elongates to become the tail of the sperm. A temporary structure called the "manchette" assists in this elongation.

During this phase, the developing spermatozoa orient themselves so that their tails point towards the center of the lumen, away from the epithelium.

Maturation phase

The excess cytoplasm, known as residual bodies, is phagocytosed by surrounding Sertoli cells in the testes.

Spermiation

The mature spermatozoa are released from the protective Sertoli cells into the lumen of the seminiferous tubule and a process called spermiation then takes place, which removes the remaining unnecessary cytoplasm and organelles.

The resulting spermatozoa are now mature but lack motility, rendering them sterile. The non-motile spermatozoa are transported to the epididymis in testicular fluid secreted by the Sertoli cells with the aid of peristaltic contraction.

Whilst in the epididymis they acquire motility and become capable of fertilisation. However, transport of the mature spermatozoa through the remainder of the male reproductive system is achieved via muscle contraction rather than the spermatozoon's recently acquired motility.

References

1. ^ [1]

External links

Spermatogenesis is the process by which male spermatogonia develop into mature spermatozoa. Spermatozoa are the mature male gametes, in many sexually reproducing organisms. Thus, spermatogenesis is the male version of gametogenesis.
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The term spermatid refers to the haploid male gametid that results from division of secondary spermatocytes. As a result of meiosis, each spermatid contains only half of the genetic material present in the original primary spermatocyte.
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A spermatozoon or spermatozoan (pl. spermatozoa), from the ancient Greek σπέρμα (seed) and ζῷον (living being) and more commonly known as a sperm cell
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Symmetry in biology is the balanced distribution of duplicate body parts or shapes. The body plans of most multicellular organisms exhibit some form of symmetry, either radial symmetry or bilateral symmetry. A small minority exhibit no symmetry (are asymmetric).
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In spermatozoa of many animals, the Acrosome is an organelle that develops over the anterior half of the spermatozoon's head. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is completed during testicular maturation.
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axoneme. The axoneme serves as the "skeleton" of these organelles, both giving support to the structure and, in some cases, causing it to bend. Though distinctions of function and/or length may be made between cilia and flagella, the internal structure of the axoneme is common to
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Identifiers
Symbol PRM2

Entrez 5620
HUGO 9448
OMIM 182890

RefSeq NM_002762
UniProt P04554
Other data

Locus Chr. 16 p13.13 Protamines
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Chromatin is the complex of DNA and protein that makes up chromosomes. It is found inside the nuclei of eukaryotic cells, and within the nucleoid in prokaryotes.[1] The nucleic acids are in the form of double-stranded DNA (a double helix).
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In spermatozoa of many animals, the Acrosome is an organelle that develops over the anterior half of the spermatozoon's head. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is completed during testicular maturation.
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A centriole is a barrel shaped organelle[1] found in most eukaryotic cells, though absent in higher plants and fungi.[2] The walls of each centriole are usually composed of nine triplets of microtubules.
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Phagocytosis is the cellular process of engulfing solid particles by the cell membrane to form an internal phagosome, or "food vacuole." The phagosome is usually delivered to the lysosome, an organelle involved in the breakdown of cellular components, which fuses with the
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The testicle (from Latin testis, meaning "witness",[1] plural testes) or ballock is the male generative gland in animals. This article will concentrate on mammalian testicles unless otherwise noted.
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A Sertoli cell (a kind of sustentacular cell) is a 'nurse' cell of the testes which is part of a seminiferous tubule.

It is activated by follicle-stimulating hormone, and has FSH-receptor on its membranes.
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Seminiferous tubules are located in the testicles, and are the specific location of meiosis, and the subsequent creation of gametes, namely spermatozoa.

The epithelium of the tubule consists of sustentacular or Sertoli cells, which are tall, columnar type cells that line
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Cytoplasm is a gelatinous, semi-transparent fluid that fills most cells. Eukaryotic cells contain a nucleus that is kept separate from the cytoplasm by a double membrane layer. The cytoplasm has three major elements; the cytosol, organelles and inclusions.
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In cell biology, an organelle is a specialized subunit within a cell, having a specific function, and separately enclosed within its own lipid membrane.

The name organelle
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The epididymis is part of the human male reproductive system and is present in all male mammals. It is a narrow, tightly-coiled tube connecting the efferent ducts from the rear of each testicle to its vas deferens.
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Peristalsis is the rhythmic contraction of smooth muscles to propel contents through the digestive tract. The word is derived from New Latin and comes from the Greek peristaltikos, peristaltic, from peristellein, "to wrap around," and stellein
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human male reproductive system is a series of organs located outside of the body and around the pelvic region of a male that contribute towards the reproductive process.

The male contributes to reproduction by producing spermatozoa.
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Embryology is the study of the development of an embryo. An embryo is defined as any vertebrate in a stage before birth or hatching. Embryology refers to the development of the egg cell (zygote) after fertilization and the differentiation of cells into tissues and organs.
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University of Lausanne (in French: Université de Lausanne) or UNIL in Lausanne, Switzerland was founded in 1537 as a school of theology, before being made a university in 1890. Today about 10,000 students and 2200 researchers study and work at the university.
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University of Bern is a university in the Swiss capital of Bern. It was founded in 1834. As one of the German-speaking universities in Switzerland its official name is Universität Bern, although it is frequently referred to in the French form, Université de Berne.
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University of Fribourg (French: Université de Fribourg; German: Universität Freiburg) is a university in the city of Fribourg, Switzerland.

It was founded in 1889 by local businessman Georges Python, although the origins of the university can be traced to
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human male reproductive system is a series of organs located outside of the body and around the pelvic region of a male that contribute towards the reproductive process.

The male contributes to reproduction by producing spermatozoa.
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The reproductive system is the ensembles and interactions of organs and/or substances within an organism that strictly pertain to reproduction. As an example, this would include in the case of female mammals, the hormone estrogen, ova, and the uterus and the vagina, and the breasts.
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In some male mammals, the scrotum is a protuberance of skin and muscle containing the testicles. It is an extension of the abdomen, and is located between the penis and anus.
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The dartos is a layer of smooth muscular fiber outside the external spermatic fascia but below the skin.

Gender differences

  • In males it is termed tunica dartos and lies beneath the skin of the scrotum.

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