Portal:Male reproductive system
Portal maintenance status: (October 2018)
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Introduction
The male reproductive system consists of a number of sex organs that play a role in the process of human reproduction. These organs are located on the outside of the body and within the pelvis.
The main male sex organs are the penis and the testicles which produce semen and sperm, which, as part of sexual intercourse, fertilize an ovum in the female's body; the fertilized ovum (zygote) develops into a fetus, which is later born as an infant.
Selected general articles
The septum of the scrotum is a vertical layer of fibrous tissue that divides the two compartments of the scrotum. It consists of flexible connective tissue. Its structure extends to the skin surface of the scrotum as the scrotal raphe. It is an incomplete wall of connective tissue and nonstriated muscle (dartos fascia) dividing the scrotum into two sacs, each containing a testis.
Histological septa are seen throughout most tissues of the body, particularly where they are needed to stiffen soft cellular tissue, and they also provide planes of ingress for small blood vessels. Because the dense collagen fibres of a septum usually extend out into the softer adjacent tissues. A septum is a cross-wall. Thus it divides a structure into smaller parts. Read more...- The term paradidymis (organ of Giraldés) is applied to a small collection of convoluted tubules, situated in front of the lower part of the spermatic cord, above the head of the epididymis.
These tubes are lined with columnar ciliated epithelium, and probably represent the remains of a part of the Wolffian body, like the epididymis, but are functionless and vestigial. The Wolffian body operates as a kidney (mesonephros) in fishes and amphibians, but the corresponding tissue is co-opted to form parts of the male reproductive system in other classes of vertebrate. The paradidymis represents a remnant of an unused, atrophied part of the Wolffian body. Read more...
The seminal vesicles (Latin: glandulae vesiculosae), vesicular glands, or seminal glands, are a pair of simple tubular glands posteroinferior to the urinary bladder of some male mammals. Seminal vesicles are located within the pelvis. They secrete fluid that partly composes the semen. Read more...
The efferent ducts (or efferent ductules or ductuli efferentes or ductus efferentes or vasa efferentia) connect the rete testis with the initial section of the epididymis.
There are two basic designs for efferent ductule structure:- a) multiple entries into the epididymis, as seen in most large mammals. In humans and other large mammals, there are approximately 15 to 20 efferent ducts, which also occupy nearly one third of the head of the epididymis.
- b) single entry, as seen in most small animals such as rodents, where by the 3–6 ductules merge into a single small ductule prior to entering the epididymis.
The scrotum. (Label for Dartos is at bottom left.)
The dartos fascia or simply dartos is a layer of connective tissue found in the penile shaft, foreskin, and scrotum. The penile portion is referred to as the superficial fascia of penis or the subcutaneous tissue of penis, while the scrotal part is the dartos proper. In addition to being continuous with itself between the scrotum and the penis, it is also continuous with Colles fascia of the perineum and Scarpa's fascia of the abdomen.
It lies just below the skin, which places it just superficial to the external spermatic fascia in the scrotum and to Buck's fascia in the penile shaft. Read more...
In males, the suspensory ligament of the penis is attached to the pubic symphysis, which holds the penis close to the pubic bone and supports it when erect. Read more...
Seminiferous tubules are located within the testes, and are the specific location of meiosis, and the subsequent creation of male gametes, namely spermatozoa.
The epithelium of the tubule consists of a type of sustentacular cells known as Sertoli cells, which are tall, columnar type cells that line the tubule. Read more...
A corpus cavernosum penis (singular) (cavernous body of the penis) is one of a pair of sponge-like regions of erectile tissue, the corpora cavernosa (plural) (cavernous bodies), which contain most of the blood in the penis during an erection. Such a corpus is homologous to the corpus cavernosum clitoridis in the female; the body of the clitoris contains erectile tissue in a pair of corpora cavernosa (literally "cave-like bodies") with a recognisably similar structure. Read more...
Figure 1. The process of spermatogenesis as the cells progress from spermatogium, to primary spermatocytes, to secondary spermatocytes, to spermatids and to Sperm.
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 secondary spermatocytes (Figure 1). Primary and secondary spermatocytes are formed through the process of spermatocytogenesis (Figure 3).
Primary spermatocytes are diploid (2N) cells. After Meiosis I, two secondary spermatocytes are formed. Secondary spermatocytes are haploid (N) cells that contain half the number of chromosomes. Read more...
The tunica albuginea is the fibrous envelope of the corpora cavernosa penis. It consists of approximately 5% elastin, an extensible tissue that is primarily made up of the amino acids glycine, valine, alanine, and proline. The majority of the remaining tissue is collagen, which is made up of lysine, proline, glycine, alanine, and other amino acids.
The tunica albuginea is directly involved in maintaining an erection; that is due to Buck's fascia constricting the deep dorsal vein of the penis, preventing blood from leaving and thus sustaining the erect state. Read more...
Germinal epithelium of the testicle.
1: basal lamina
2: spermatogonia
3: spermatocyte 1st order
4: spermatocyte 2nd order
5: spermatid
6: mature spermatid
7: Sertoli cell
8: tight junction (blood testis barrier)
A Sertoli cell (a kind of sustentacular cell) is a "nurse" cell of the testicles that is part of a seminiferous tubule and helps in the process of spermatogenesis, the production of sperm.
It is activated by follicle-stimulating hormone (FSH) secreted by the adenohypophysis, and has FSH receptor on its membranes. It is specifically located in the convoluted seminiferous tubules (since this is the only place in the testes where the spermatozoa are produced). Development of Sertoli cells is directed by the testis-determining factor protein. Read more...
Germinal epithelium of the testicle. 1 basal lamina, 2 spermatogonia, 3 spermatocyte 1st order, 4 spermatocyte 2nd order, 5 spermatid, 6 mature spermatid, 7 Sertoli cell, 8 tight junction (blood testis barrier)
The blood–testis barrier is a physical barrier between the blood vessels and the seminiferous tubules of the animal testes. The name "blood-testis barrier" is misleading in that it is not a blood-organ barrier in a strict sense, but is formed between Sertoli cells of the seminiferous tubule and as such isolates the further developed stages of germ cells from the blood. A more correct term is the "Sertoli cell barrier" (SCB). Read more...
Germinal epithelium of the testicle.
1: basal lamina
2: spermatogonia
3: spermatocyte 1st order
4: spermatocyte 2nd order
5: spermatid
6: mature spermatid
7: Sertoli cell
8: tight junction (blood testis barrier)
The spermatid is 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.
Spermatids are connected by cytoplasmic material and have superfluous cytoplasmic material around their nuclei. Read more...
Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone (LH). Leydig cells are polyhedral in shape, display a large prominent nucleus, an eosinophilic cytoplasm and numerous lipid-filled vesicles. Read more...
Spermatocytogenesis is the male form of gametocytogenesis and involves stem cells dividing to replace themselves and to produce a population of cells destined to become mature sperm.
The stem cells involved are called spermatogonia and are a specific type of stem cell known as gametogonia. Read more...
A diagram of the major components of an adult human testicle, including the following numbered items: 1. Tunica albuginea, 2. Septula testis, 3. Lobulus testis, 4. Mediastinum testis, 5. Tubuli seminiferi contorti, 6. Tubuli seminiferi recti, 7. Rete testis, 8. Ductuli efferentes testis, 9a. Head of epididymis, 9b. Body of epididymis, 9.c Tail of epididymis,10. Vas deferens, 11a. Tunica vaginalis (parietal lamina), 11b. Tunica vaginalis (visceral lamina), and 12. Cavity of tunica vaginalis.
The mediastinum testis is a network of fibrous connective tissue that extends from the top to near the bottom of each testis. It is wider above than below.
Numerous imperfect septa are given off from its front and sides, which radiate toward the surface of the testes and are attached to the tunica albuginea. These divide the interior of the testes into a number of incomplete spaces called lobules. These are somewhat cone-shaped, being broad at their bases at the surface of the gland, and becoming narrower as they converge to the mediastinum. Read more...
Each seminal vesicle consists of a single tube, coiled upon itself, and giving off several irregular cecal diverticula; the separate coils, as well as the diverticula, are connected together by fibrous tissue. When uncoiled, the tube is about the diameter of a quill, and varies in length from 10 to 15 cm.; it ends posteriorly in a cul-de-sac; its anterior extremity becomes constricted into a narrow straight duct called the excretory duct of seminal gland (or duct of the seminal vesicle), which joins with the corresponding ductus deferens to form the ejaculatory duct. Read more...
In anatomy, the urethra (from Greek οὐρήθρα – ourḗthrā) is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body. In males, the urethra travels through the penis and also carries semen. In human females (and in other primates), the urethra connects to the urinary meatus above the vagina, whereas in non-primates, the female's urethra empties into the urogenital sinus.
Females use their urethra only for urinating, but males use their urethra for both urination and ejaculation. The external urethral sphincter is a striated muscle that allows voluntary control over urination. The internal sphincter, formed by the involuntary smooth muscles lining the bladder neck and urethra, is innervated by the sympathetic division of the autonomic nervous system. The internal sphincter is present both in males and females. Read more...
The epididymis (/ɛpɪˈdɪdɪmɪs/; plural: epididymides /ɛpɪdɪˈdɪmədiːz/ or /ɛpɪˈdɪdəmɪdiːz/) is a tube that connects a testicle to a vas deferens in the male reproductive system. It is present in all male reptiles, birds, and mammals. It is a single, narrow, tightly-coiled tube in adult humans, 6 to 7 meters (20 to 23 ft) in length connecting the efferent ducts from the rear of each testicle to its vas deferens. Read more...
The process of spermatogenesis. 1. Primary spermatocyte 2. Secondary spermatocytes
3. Spermatids 4. Sperm
Spermiogenesis is the final stage of spermatogenesis, which sees the maturation of spermatids into mature, motile spermatozoa. The spermatid is a more or less circular cell containing a nucleus, Golgi apparatus, centriole and mitochondria. All these components take part in forming the spermatozoon. Read more...
A spermatozoon (pronounced /ˌspɜːrmætəˈzoʊən/, alternate spelling spermatozoön; plural spermatozoa; from Ancient Greek: σπέρμα "seed" and Ancient Greek: ζῷον "living being") is a motile sperm cell, or moving form of the haploid cell 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 a 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 by Anton van Leeuwenhoek in 1677. Read more...
The ejaculatory ducts (ductus ejaculatorii) are paired structures in male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the urethra at the seminal colliculus. During ejaculation, semen passes through the prostate gland, enters the urethra and exits the body via the urinary meatus. Read more...
The spongy urethra (cavernous portion of urethra, penile urethra) is the longest part of the male urethra, and is contained in the corpus spongiosum of the penis.
It is about 15 cm long, and extends from the termination of the membranous portion to the external urethral orifice. Read more...
The glans penis is the sensitive bulbous structure at the distal end of the human penis. The glans is anatomically homologous to the clitoral glans of the human female.
Typically, the glans is completely or partially covered by the foreskin, except in men who have been circumcised. The foreskin can generally be retracted over and past the glans, and may automatically retract during an erection. Read more...
The vas deferens (Latin: "carrying-away vessel"; plural: vasa deferentia), also called ductus deferens (Latin: "carrying-away duct"; plural: ductus deferentes), is part of the male reproductive system of many vertebrates; these ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. It is a partially coiled tube which exits the abdominal cavity through the inguinal canal. Read more...
The seminal colliculus (Latin colliculus seminalis), or verumontanum, of the prostatic urethra is a landmark near the entrance of the ejaculatory ducts (on both sides, corresponding vas deferens and seminal vesicle feed into corresponding ejaculatory duct). Verumontanum is translated from Latin to mean 'mountain ridge', a reference to the distinctive median elevation of urothelium that characterizes the landmark on magnified views. Embryologically, it is derived from the uterovaginal primordium. The landmark is important in classification of several urethral developmental disorders. The margins of seminal colliculus are the following:- the orifices of the prostatic utricle
- the slit-like openings of the ejaculatory ducts.
- the openings of the prostatic ducts
The tunica vaginalis is the pouch of serous membrane that covers the testes. It is derived from the vaginal process of the peritoneum, which in the fetus precedes the descent of the testes from the abdomen into the scrotum.
After its descent, that portion of the pouch which extends from the abdominal inguinal ring to near the upper part of the gland becomes obliterated; the lower portion remains as a shut sac, which invests the surface of each testis, and is reflected on to the internal surface of the scrotum; hence it may be described as consisting of a visceral and a parietal lamina. Read more...- The epididymis is covered by a two layered pseudostratified epithelium. The epithelium is separated by a basement membrane from the connective tissue wall which has smooth muscle cells. The major cell types in the epithelium are:
- Main cells: columnar cells that, with the basal cells, form the majority of the epithelium. These cells extend from the lumen to the basal lamina, They also have non-motile stereocilia, which are long and branching in the head region and shorter in the tail region. They also secrete carnitine, sialic acid, glycoproteins, and glycerylphosphorylcholine into the lumen.
- Basal cells: shorter, pyramid-shaped cells which contact the basal lamina but taper off before their apical surfaces reach the lumen. These are thought to be undifferentiated precursors of principal cells.
- Apical cells: predominantly found in the head region
- Clear cells: predominant in the tail region
- Intraepithelial lymphocytes: distributed throughout the tissue.
- Intraepithelial macrophages
The rectus sheath, an example of a fascia.
A fascia (/ˈfæʃ(i)ə/; plural fasciae /ˈfæʃii/; adjective fascial; from Latin: "band") is a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches, stabilizes, encloses, and separates muscles and other internal organs. Fascia is classified by layer, as superficial fascia, deep fascia, and visceral or parietal fascia, or by its function and anatomical location.
Like ligaments, aponeuroses, and tendons, fascia is made up of fibrous connective tissue containing closely packed bundles of collagen fibers oriented in a wavy pattern parallel to the direction of pull. Fascia is consequently flexible and able to resist great unidirectional tension forces until the wavy pattern of fibers has been straightened out by the pulling force. These collagen fibers are produced by fibroblasts located within the fascia. Read more...
The urinary meatus, also known as the external urethral orifice, is the opening of the urethra. It is the point where urine exits the urethra in males and in females, and also where semen exits the urethra in males. The meatus has varying degrees of sensitivity to touch. The meatus is located on the glans penis in males and in the vulval vestibule in females. Read more...
The cavernous portion of the urethra is narrow, and of uniform size in the body of the penis, measuring about 6 mm in diameter; it is dilated behind, within the bulb, and again anteriorly within the glans penis, where it forms the fossa navicularis urethrae.
The navicular fossa is the spongy part of the male urethra located at the glans penis portion. It is essentially the part right before the external urethral orifice. It is lined by stratified squamous, non-keratinizing epithelium when viewed histologically. Read more...
For their anterior three-fourths the corpora cavernosa penis lie in intimate apposition with one another, but behind they diverge in the form of two tapering processes, known as the crura, which are firmly connected to the ischial rami.
Traced from behind forward, each crus begins by a blunt-pointed process in front of the tuberosity of the ischium, along the perineal surface of the conjoined (ischiopubic) ramus. Read more...
The prostate (from Ancient Greek προστάτης, prostates, literally "one who stands before", "protector", "guardian") is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals. It differs considerably among species anatomically, chemically, and physiologically.
The function of the prostate is to secrete a slightly alkaline fluid, milky or white in appearance, that in humans usually constitutes roughly 30% of the volume of semen along with spermatozoa and seminal vesicle fluid. Semen is made alkaline overall with the secretions from other contributing glands, including, at least, seminal vesicle fluid. The alkalinity of semen helps neutralize the acidity of the vaginal tract, prolonging the lifespan of sperm. The prostatic fluid is expelled in the first part of ejaculate, together with most of the sperm. In comparison with the few spermatozoa expelled together with mainly seminal vesicular fluid, those in prostatic fluid have better motility, longer survival, and better protection of genetic material. Read more...
The prostatic utricle (Latin for "pouch of the prostate") is a small indentation in the prostatic urethra, at the apex of the urethral crest, on the seminal colliculus (verumontanum), laterally flanked by openings of the ejaculatory ducts. It is also known as the vagina masculina or (in older literature) vesicula prostatica. Read more...
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