Male

∞ generated and posted on 2016.04.25 ∞

Male mammals are responsible for producing, maturing, and delivering sperm internally to females (and in some species also contributing to the raising of resulting offspring).

Males in terms of their contribution to reproduction essentially by definition produce sperm, which are produced, in animals, within gonads that we refer to as testes.

This page contains the following terms: Gamete, Gonads, Testes, Scrotum, Spermatogenesis, Seminiferous tubules, Spermatogonia, Sperm, Semen, Epididymis, Vas deferens, Seminal vesicle, Prostate gland, Bulbourethral gland, Penis

The video provides a nice overview of male reproductive system from prior to puberty through to the approximately ejaculation.



Gamete

Haploid cell that fuses with a second haploid cell to effect fertilization and create a zygote.
Haploid means having half as much genetic material as found in what instead are known as diploid cells. Normal human cells are both diploid and possess 46 chromosomes. Gametes, by contrast, possess 23 chromosomes.

The process by which a diploid cell becomes a haploid cell is known as meiosis, which is a kind of cell division (the conversion of one cell into two, or in the case of meiosis, one cell into four). The gametes in humans as well as many other organisms are differentiated into male-associated gametes known as sperm or spermatozoa, and female-associated gametes known as eggs or oocytes.


Links to terms of possible interest: Acrosome, Axoneme, Basal body, Corona radiata, Egg, End piece of sperm, First polar body, Mitochondria, Sperm, Spermatozoa, Zona pellucida

The above video presents the very basics of gamete formation; meiosis is a kind of cell division, i.e., that is used by animals to produce gametes.

The above video provides a quick overview of the basics of meiotic cell division.

The above video provides a fair range of information regarding what gametes are all about.



Gonads

Gamete producing organ.
It is within gonads that gamete precursor cells undergo meiosis as well as maturation and associated development to become gametes. These gametes in males are known as sperm (or spermatozoa) and in females they are known as eggs (or oocytes). The gonads that produce them are described as testes and ovaries, respectively.

In addition to producing gametes, the gonads are major producers of sex hormones. The latter are the androgens (particularly testosterone) by the testes and a combination of estrogen and progesterone by the ovaries.


Links to terms of possible interest: Cortical cords, Ductus epididymidis, Efferent ductule, Follicular cell, Germinal epithelium, Gonad, Hindguts, Mesonephric duct, Mesorchium, Mesovarium, Mesonephric tubule, Oogonium, Ovarian stroma, Ovary, Paramesonephric duct, Primary sex cord, Primordial follicle, Primordial germ cell, Rete ovarii, Rete testis, Seminiferous cord, Seminiferous tubule, Suprarenal cortex, Suprarenal medulla, Testis, Tunica albuginea, Uterine tube

The above video provides an introduction to the testes and ovaries, i.e., the male gonads and female gonads, respectively.



Testes

Male gonads.
A.k.a., testicles, the male gonads in humans and various other mammals are housed within a sac known as a scrotum. Within the testes are found seminiferous tubules. It is in association with the seminiferous tubules that spermatogenesis, the formation of sperm, occurs.


Links to terms of possible interest: Ductus deferens, Epididymis, Lobule, Rete testis, Seminiferous tubules, Septum, Spermatic cord, Testis, Tunica albuginea, Vas deferens,

This video discusses the anatomy of the penis, prostate gland, testicles, and scrotum, with discussion of the testes starting at 4:03.



Scrotum

Sac in certain mammals that holds the male gonads.
The scrotum regulates the temperature of the testes to allow for optimal sperm production. That temperature is slightly less than that of body temperature and thus the scrotum regulates the temperature of testes to between that of the external environment and that of the core of the body.

When the testes are overly warm, the scrotum relaxes and the testes are found further away from the body core. When the testes are overly cold, on the other hand, the scrotum tenses, pulling the testes closer to the body core and therefore closer to warmth.


Links to terms of possible interest: Epididymis, Penis, Scrotum, Sperm, Spermatic cord, Testicle

The above video provides a nice introduction to the anatomy and functioning of the scrotum.



Spermatogenesis

The formation of spermatozoa as occurs in humans in the seminiferous tubules.
The formation of spermatozoa begins with cells that are called spermatogonia, which give rise to spermatocytes, specifically primary spermatocytes. The primary spermatocytes undergo the first round of meiotic cell division, yielding two secondary spermatocytes. The secondary spermatocytes then undergo the second round of meiotic cell division, yielding a total of four spermatids (four spermatids per starting primary spermatocytes, which works out to two spermatids per secondary spermatocyte). The spermatids at this point are immature but then mature into flagellated spermatozoa.

This whole process occurs while at the same time the cells involved are propelled from the outer layers of the walls of the seminiferous tubules inward toward the lumen of these tubules. The flagellated sperm then move from the seminiferous tubules towards the epididymis, where maturation is completed and sperm storage in anticipation of subsequent ejaculation otherwise occurs.


Links to terms of possible interest: Ejaculation, Epididymis, Meiosis, Primary spermatocytes, Secondary spermatocytes, Seminiferous tubules, Spermatids, Spermatocytes, Spermatogonia, Spermatozoa,



Seminiferous tubules

Specific location of sperm production.
The seminiferous tubules are found in tight coils within testes, with approximately 250 such coils per testicle. Spermatogenesis proceeds from outside of the seminiferous tubules to inside, with spermatogonia found on the outside and maturing sperm found on the inside of the seminiferous tubules. The seminiferous tubules are more or less continuous with and supply sperm to a tube known as the epididymis, which in turn is continuous with and supplies sperm to a tube known as the vas deferens.


Links to terms of possible interest: Epididymis, Seminiferous tubules, Sperm, Spermatogenesis, Spermatogonia, Testes, Testicle, Vas deferens

The above video provides an overview of the anatomy of the male reproductive system with some emphasis on the seminiferous tubules (pardon the abrupt cutting off at the end).



Spermatogonia

Precursor cells found in male gonads which develop into male gametes.
Unlike the gametes they eventually develop into, a spermatogonium (singular) is a diploid cell, i.e., just as are most of the cells that make up the human body. Spermatogonia (46 chromosomes) go through a mitotic cell division process to yield cells called primary spermatocytes (also 46 chromosomes).

It is those cells that then go through the cell division process called meiosis to generate secondary spermatocytes and then spermatids (both of which are haploid, that is, have only 23 chromosomes), which in turn are the precursor cells to the gametes that are known as spermatozoa, i.e., sperm.

The above video takes a quick, relatively low resolution walk through spermatogenesis, beginning more or less with spermatogonia.



Sperm

Gametes that upon fertilization supply chromosomes but not much else.
Sperm, a.k.a., spermatozoa, tend to be relatively small and somewhat motile (though with exceptions to the latter in some species). Their "job" is both to reach the ovum (unfertilized egg) and then to fertilize the ovum. Human sperm is flagellated with a single flagellum, a whip-like organelle that propels the sperm forward towards the ovum.

The sperm are generated, via a process known as spermatogenesis, within the testes, as carried by various tubes towards the urethra (chiefly the vas deferens from the epididymis) and then through the urethra. In the course of this movement the sperm are combined with various fluids – from the seminal vesicles and prostate gland – to generate semen.


Links to terms of possible interest: Epididymis, Fertilization, Flagellum, Gametes, Motile, Ovum, Prostate gland, Semen, Seminal vesicles, Sperm, Spermatogenesis, Spermatozoa, Unfertilized egg, Urethra, Vas deferens,

The above video provides some interesting and fun, especially evolutionary musings on sperm.



Semen

Sperm carrying fluid of ejaculation.
Semen in addition to carrying sperm also consists of the fluid produced by the seminal vesicles along with that produced by the prostate gland and bulbourethral glands. The function of semen is to increase the probability of sperm survival and functioning in the course of their deposition into the vagina.

The above video discusses the anatomy of the male genitourinary tract.



Epididymis

Post seminiferous tubule location of sperm storage and maturation.
The epididymis connects the testes to the vast deferens. They – one per testicle – consist of coiled tubes within which sperm is stored during the completion of their maturation process.

In the epididymal walls are smooth muscles that are responsible for propelling sperm into the vas deferens in the course of orgasm, and the contraction of this smooth muscle occurs in a rhythmic fashion. As sperm does not last forever following maturation, the epididymis is also the site of sperm degeneration and reabsorption by the body.


Links to terms of possible interest: Body of epididymis, Deferent duct, Efferent ductules, Epididymis, Head of epididymis, Inferior aberrant ductule, Mediastinum testis, Orgasm, Rete testis, Seminiferous tubules, Septula testis, Sperm, Straight seminiferous tubules, Tail of epididymis, Testes, Tunica albuginea, Tunica artery, Tunica vaginalis, Vas deferens

Discussion of the epididymis becomes at about 2:46, but the video provides a pretty good overview of testis gross anatomy as well.



Vas deferens

Tubes that rhythmically delivers sperm from the epididymis to the urethra during ejaculation.
The vas deferens is also known as the ductus deferens, which is a relatively wide tube (>3 mm in diameter) that is "powered" by associated smooth muscle. The vas deferens receives seminal fluid from the seminal vesicles and then passes through the prostate gland, where connection to the urethra occurs. It is the vas deferens that is intentionally blocked in the course of a vasectomy.


Links to terms of possible interest: Prostate, Seminal vesicles, Testicle, Vas deferens, Vasectomy

This video discusses the anatomy of the penis, prostate gland, testicles, and scrotum, with discussion of the vas deferens starting at 6:00.



Seminal vesicle

Source of yellowish fluid that aids in sperm post ejaculation survival and functioning.
There are two seminal vesicles, one for each vas deferens. Primary ingredients of the seminal fluid that they produce are the sugar fructose, which the sperm use as an energy source, and relatively high pH buffers, which serve to counteract the relatively low pH (acidity) of the vagina.

The seminal fluid is also responsible for the thickening of semen (coagulation) soon following ejaculation, which may play a role in the near-term retention of the semen within the vagina. This coagulation reverses, however, after a number of minutes.


Links to terms of possible interest: Bladder, Prostate, Seminal vesicle, Urethra

The above video discusses the seminal vesicles starting at 0:45 but discusses the vas deferens, prostate gland, and bulbourethral gland, and lots of discussion of the urethra as well.



Prostate gland

Contributor of white, alkaline fluid that makes up one half or more of the volume of semen.
This fluid is an important contributor to the post ejaculatory survival and functioning of sperm. The gland itself, however, can become inflamed and also cancerous. The latter is the sixth most common cause of cancer-related death in men, worldwide, though the incidence of prostate cancer varies among populations.


Links to terms of possible interest: Bladder, Enlarged prostate, Penis, Prostate gland, Rectal examination, Seminal vesicles, Testicle, Urethra, Vas deferens

The above video discusses the prostate gland starting at 0:45 but discusses the vas deferens, seminal vesicles, and bulbourethral gland, and lots of discussion of the urethra as well.



Bulbourethral gland

Source of pre-ejaculate in males.
Pre-ejaculate is a urethra-lubricating fluid that reduces friction during ejaculation. It is a clear fluid contrasting the cloudiness of semen. Pre-ejaculate also normally does not carry sperm, though sperm can be present if found in the urethra prior to pre-ejaculate release, i.e., as from a previous ejaculation.


Links to terms of possible interest: Bulbourethral gland, External urethral orifice, Membranous urethra, Penile urethra, Penis, Prostate gland, Prostatic urethra, Trigone, Ureter, Urethra, Urinary bladder

The above video discusses very briefly the bulbourethral gland starting at 4:55 but discusses the vas deferens, seminal vesicles, prostate gland, and lots of discussion of the urethra as well.



Penis

Semen delivery organ.
It is the job of the penis, in erect form, to supply a conduit for semen into a mate's vagina. This delivery is to outside of the cervix, and subsequent semen movement is from the vagina through the cervix and into the uterus.

It is the job of the penis, also in erect form, to receive tactile stimulation to induce the ejaculatory reflex. The penis, again in erect form, also plays roles in the sexual arousal of partners during mating.

Lastly, the penis, owing to its length, houses a urethra whose opening is substantially further from the anal opening versus the urethral opening in females, resulting in lower likelihoods of the development of urinary tract infections that otherwise can be due to contamination with fecal material.


Links to terms of possible interest: Cavernous artery, Corpora cavernosa penis, Corpora cavernosum urethra, Erectile tissue, Erection, Fibrous envelope, Glans penis, Integument, Penis, Septum pectiniforme, Spongy body, Urethra

The above video is an informal but still great overview of what the penis is all about.

This video discusses the anatomy of the penis, prostate gland, testicles, and scrotum, with discussion of the penis starting at 1:00>.

The above video provides a discussion of erectile dysfunction, its causes, and its treatment.

On hydrostatic skeletons, comparative anatomy, and erections.


Loading