1. University of California
The Male Reproductive
System
Michael Hall PhD
University of California
Los Angeles

2. Components of the Male Reproductive System
The male reproductive system includes 1.the testes which produce sperm, 2. the genital ducts which transport sperm through 3. the penis to the exterior and
4. the accessory sex glands (seminal vesicles, prostate and bulbourethral glands).

3. Embryology of Gonad Development
Mesenchyme
Genital ridge
Medulla
Cortex
6 weeks (male = female)
Male
7-8 weeks
Female

4. Functions of Testes Spermatogenesis-production of sperm
a. spermatocytogenesis-mitotic division of
spermatogonia
b. meiosis-production of haploid spermatids
c. spermiogenesis-maturation of spermatids to
spermatozoa
2. Steroidogenesis-production of steroid hormones

5. Testis Head of epididymis Vas deferens Efferent ducts
Body of epididymis
Rete testis
Mediastinum testis
Tail of epididymis
Tubuli recti
Head of epididymis
Efferent ducts
Seminiferous tubule
Septum
Tunica albuginea
Tunica vaginalis
Note: The mediastinum testis is the thickened part of the tunica albuginea (dense connective tissue), while the rete testis is a complex of epithelium lined channels in the mediastinum. Sperm flows from the seminiferous tubules into the tubuli recti (the ends of the seminiferous tubules) into the rete testis and leaves the testis through the efferent ducts. It will help if you remember that the seminiferous tubules are shaped like a ‘U’ with both ends open.

6. T. albuginea Seminiferous tubules
This is a low power microscopic picture of the seminiferous tubules in a lobule. Note that due to their highly convoluted structure, they are cut in a variety of sections. The thick tunica albuginea surrounds and encloses the entire testis.

7. Components of the seminiferous epithelium
Lumen
Spermatid
Primary
spermatocytes
Secondary
spermatocyte
Spermatogonium
Basal lamina
Sertoli cell
nucleus
cytoplasm
Spermatozoa
(2N)
(4N)
(N) CT
(DNA)
‘N’ denotes the DNA content of cells in various stages of mitosis and meiosis

8. Spermatogenesis-production of sperm
a. spermatocytogenesis-mitotic division of
spermatogonia (2N) to primary spermatocytes (4N)
b. meiosis-two successive divisions producing
haploid spermatids (N)
c. spermiogenesis-maturation of spermatids to
spermatozoa (non-motile)

9. Cross section of a seminiferous tubule
Leydig

10. Spermiogenesis
Spermiogenesis denotes the maturation of sperm from a spermatid, to a mature (but non motile) spermatozoa

11. Sertoli Cells Lumen Spermatozoa Spermatid Secondary spermatocyte
Primary
spermatocytes
Secondary
spermatocyte
Spermatogonium
Basal lamina
Sertoli cell
nucleus
cytoplasm
Spermatozoa
(2N)
(4N)
(N) CT
(DNA)
‘N’ denotes the DNA content of cells in various stages of mitosis and meiosis

12. Sertoli cells form tight junctions
Junctional
complex JC
Sertoli cells form tight junctions
The seminiferous epithelium sits on a basement membrane. Adjacent Sertoli cells are joined by junctional complexes (JC) which prevent the passage of any toxins, viruses, antibodies etc. between the cells. Thus the developing sperm cells are in an immunologically protected environment.

13. Functions of Sertoli Cells
Support, protection, and nutritional regulation
of the developing spermatozoa
2. Phagocytosis of residual bodies
3. Secretion of testicular fluid into lumen
4. Production of Androgen Binding Protein (ABP)
5. Secretion of Inhibin (suppresses FSH secretion)

14. Components of the seminiferous epithelium
Lumen
Spermatid
Primary
spermatocyte
Secondary
Spermatogonium
Basal lamina
Sertoli cell
nucleus
cytoplasm
Spermatozoa
(2N)
(4N)
(N)
It will help if you remember that the stem cells (spermatogonia) of this epithelium lie on the basal lamina at the circumference of the seminiferous tubule, and that as the spermatogenic cells mature, they move towards the lumen of the tubule, until the most mature spermatozoa are released into the lumen.

15. Sertoli cells in seminiferous tubule
The nucleus of the Sertoli cell is about all that one can pick out in light micrographs. These nuclei are oval shaped with a prominent nucleolus, indicating that they are producing a lot of ribosomal RNA. Remember that they completely surround the developing germ cells, and are responsible for the metabolic support, nutrition and protection of these cells. They also secrete testicular fluid and synthesize androgen binding protein, which binds testosterone. Can you identify the other cells in this section?

16. Leydig cells Leydig cells lie in the CT between the seminiferous
tubules
Leydig cells
Leydig cells
Leydig cells are found in the interstitial tissue between the tubules.
Note that the spermatids found in this tubule have not developed the characteristic shape of spermatozoa, and are thus called ‘early spermatids’
Early spermatids

18. Leydig cells Seminiferous tubule
Note that the Leydig cells have a ‘foamy’ appearance. This is because they contain large amounts of lipids, from which androgens, particularly testosterone, are synthesized. Leydig cells lie in the connective tissue between seminiferous tubules.

19. Function of Leydig cells and Testosterone
The prime function of the Leydig cells is the
production of testosterone. Testosterone
has many separate but interrelated functions:
a). differentiation and maturation of sperm in the
seminiferous tubule (200x testosterone)
b). Development and secretory activity of accessory
sex glands ( seminal vesicle, prostate and
bulbourethral glands
c). development of male secondary sex characteristics
(facial and pubic hair, muscularity, libido, obnoxious
behavior, voice etc.)

20. Hormonal control of spermatogenesis
Hypothalamus
GnRH
1.LH stimulates
synthesis of male
sex hormones
by Leydig cells 1 2
2.FSH stimulates
Sertoli cells to
synthesize ABP
3.Leydig cells
produce
testosterone
into blood
into tubule 3 LH
FSH
Inhibin from
Sertoli cells
Seminiferous tubule
Testosterone which is produced by the Leydig cells, under the stimulation of LH from the anterior pituitary, is transported to the seminiferous tubules, where it binds to androgen binding protein (ABP), thus increasing the local concentration of testosterone to levels high enough to stimulate spermatogenesis. ABP is produced by Sertoli cells under the stimulation of FSH. Lower levels of testosterone also diffuse into the blood, where they are involved in the development of the secondary sex characteristics and the development and maintenance of the accessory sex glands

21. Components of the Genital
Duct System
prostate
gland
urethra
seminal vesicle
epididymis
efferent
ducts
rete testis
b-u gland
vas deferens
Spermatozoa leave the testes through the straight tubules and enter the anastomosing channels of the rete testis, from where they pass into the efferent ducts, the vas deferens, through the ampulla and ejaculatory duct and into the urethra. The non-sperm components of semen are added from the seminal vesicle, the prostate gland and the bulbo-urethral (b-u) gland. Semen leaves the penis through the urethra.

22. Rete testis
The rete testis consists of a series of epithelium lined channels in the dense connective tissue of the mediastinum. Spermatozoa leave the seminiferous tubules and percolate through the rete testis, before entering the efferent ducts, which connect to the vas deferens.

23. Components of the Genital
Duct System
prostate
gland
urethra
seminal vesicle
ampulla
epididymis
efferent
ducts
rete testis
b-u gland
vas deferens
Spermatozoa leave the testes through the straight tubules and enter the anastomosing channels of the rete testis, from where they pass into the efferent ducts, the vas deferens, through the ampulla and ejaculatory duct and into the urethra. The non-sperm components of semen are added from the seminal vesicle, the prostate gland and the bulbo-urethral (b-u) gland. Semen leaves the penis through the urethra.

24. Efferent duct Epididymis smooth muscle sc cilia
The epithelium of the efferent ducts is pseudostratified columnar and consists of alternating groups of tall columnar and cuboidal cells which gives it a wavy appearance. The tall columnar cells are ciliated which helps to move the spermatozoa along the tubule, while the cuboidal cells contain microvilli and are involved in the reabsorption of fluids. The epithelium of the epididymis, by contrast, has a smooth surface. It is also pseudostratified, with tall columnar cells and small basal cells lying on the basement membrane (what do you think the function of these basal cells might be?). The tall columnar cells contain non-motile stereocilia (sc) on their apical surface, which are involved in the reabsortion of fluids, as well as the secretion of factors involved in the maturation of sperm as they pass through this tubule. Both of these tubules are surrounded by a thin layer of smooth muscle. Rhythmic contractions of these muscle layers help to move the spermatozoa through these ducts.

25. Components of the Genital
Duct System
prostate
gland
urethra
seminal vesicle
ampulla
epididymis
efferent
ducts
rete testis
b-u gland
vas deferens
Spermatozoa leave the testes through the straight tubules and enter the anastomosing channels of the rete testis, from where they pass into the efferent ducts, the vas deferens, through the ampulla and ejaculatory duct and into the urethra. The non-sperm components of semen are added from the seminal vesicle, the prostate gland and the bulbo-urethral (b-u) gland. Semen leaves the penis through the urethra.

26. Efferent duct Epididymis smooth muscle sc cilia
The epithelium of the efferent ducts is pseudostratified columnar and consists of alternating groups of tall columnar and cuboidal cells which gives it a wavy appearance. The tall columnar cells are ciliated which helps to move the spermatozoa along the tubule, while the cuboidal cells contain microvilli and are involved in the reabsorption of fluids. The epithelium of the epididymis, by contrast, has a smooth surface. It is also pseudostratified, with tall columnar cells and small basal cells lying on the basement membrane (what do you think the function of these basal cells might be?). The tall columnar cells contain non-motile stereocilia (sc) on their apical surface, which are involved in the reabsortion of fluids, as well as the secretion of factors involved in the maturation of sperm as they pass through this tubule. Both of these tubules are surrounded by a thin layer of smooth muscle. Rhythmic contractions of these muscle layers help to move the spermatozoa through these ducts.

27. Components of the Genital
Duct System
prostate
gland
urethra
seminal vesicle
ampulla
epididymis
efferent
ducts
rete testis
b-u gland
vas deferens
Spermatozoa leave the testes through the straight tubules and enter the anastomosing channels of the rete testis, from where they pass into the efferent ducts, the vas deferens, through the ampulla and ejaculatory duct and into the urethra. The non-sperm components of semen are added from the seminal vesicle, the prostate gland and the bulbo-urethral (b-u) gland. Semen leaves the penis through the urethra.

28. Vas deferens Smooth muscle layers IL C OL
The vas deferens is surrounded by 3 thick layers of smooth muscle—inner (IL) and outer (OL) longitudinal and middle circular (C). It is contraction of these muscle layers that forcefully ejects the sperm during ejaculation.

29. Vas deferens smooth muscle stereocilia
The epithelium of the vas deferens is pseudostratified columnar with stereocilia. Stereocilia are non-motile. They resemble long microvilli and are probably involved in the resorprtion of fluids. Note the thick inner longitudinal layer of smooth muscle. Sperm are stored in the vas deferens as well as the tail of the epididymis until ejaculation.

30. Components of the Genital
Duct System
prostate
gland
urethra
seminal vesicle
ampulla
epididymis
efferent
ducts
rete testis
b-u gland
vas deferens
spermatic
cord
Spermatozoa leave the testes through the straight tubules and enter the anastomosing channels of the rete testis, from where they pass into the efferent ducts, the vas deferens, through the ampulla and ejaculatory duct and into the urethra. The non-sperm components of semen are added from the seminal vesicle, the prostate gland and the bulbo-urethral (b-u) gland. Semen leaves the penis through the urethra.

31. Spermatic cord vas deferens pampiniform plexus cremaster muscle
The spermatic cord carries the blood and nerve supply to and from the testes, as well as the vas deferens. The pampiniform plexus comprises a counter current heat exchange system, whereby arterial blood traveling to the testes is cooled by venous blood returning from the testes, thus helping to maintain the 2 degree lower temperature required for the development of the sperm.
cremaster
muscle

32. Pampiniform plexus of spermatic cord
Nerve
The spermatic veins emerge from the back of the testis, and receive tributaries from the epididymis: they unite and form a convoluted plexus, the pampiniform plexus, which forms the chief mass of the cord. In addition to its function in venous return from the testes, the pampiniform plexus also plays a role in the temperature regulation of the testes. It acts as a heat exchanger, cooling blood in adjacent arteries supplying the testes . The vessels composing this plexus are very numerous, and eventually unite to form a single vein, the testicular vein, which opens into the inferior vena cava. The veins of the pampiniform plexus have thick muscular walls, so that they resemble arteries.
Arteries and veins

33. Vasectomy
Vasectomy involves cutting the vas deferens and tying off or cauterizing its ends.. Sperm is still produced—it just doesn’t find it’s way into the vas deferens. Since the contributions of the accessory sex glands make up 95% of the volume of semen, the volume of the ejaculate is almost the same as before vasectomy. The Leydig cells are unaffected by this procedure, and still produce testosterone, so libido, erection and ejaculation are normal.

34. The Accessory Sex Glands
prostate
gland
urethra
seminal vesicle
b-u gland
Spermatozoa leave the testes through the straight tubules and enter the anastomosing channels of the rete testis, from where they pass into the efferent ducts, the vas deferens, through the ampulla and ejaculatory duct and into the urethra.The non-sperm components of semen are added from the seminal vesicle, the prostate gland and the bulbo-urethral (b-u) gland. Semen travels though the penis in the urethra.

35. Seminal vesicle Cross section of a single, highly coiled seminalSM
Epithelium
Seminal vesicle 1 2
Cross section of a single,
highly coiled seminal
vesicle surrounded
by smooth muscle
2. High magnification of the
mucosa of a seminal vesicle
Each seminal vesicle is a highly coiled tube, with an extensively folded or ridged mucosa. It is so folded upon itself that it often appears (lower fig.) as if the mucosa forms arches. However, this is due to the plane of the section. The epithelium is pseudostratified, consisting of low columnar/cuboidal cells and small round basal cells. . The epithelial cells secrete the seminal fluid that is stored in the lumen of the organ until ejaculation.
The underlying lamina propria contains some smooth muscle and extensive elastic fibers while the submucosa contains extensive smooth muscle (SM) which contracts during ejaculation

36. Prostate Gland Bladder Urethra Smooth muscle Capsule Mucosal glands
Submucosal glands
Main glands
Capsule
Smooth muscle
Urethra
Bladder
Prostate Gland
The prostate gland contains 3 layers of secretory glands, all of which open into the urethra. It is enclosed in a thick fibromuscular capsule, and the mucosa of the glands is also rich in smooth muscle cells and elastic fibers. Contraction of the muscle forcefully propels prostatic fluid into the urethra. As the prostate grows, it may constrict the urethra, making urination difficult.

37. Prostate Gland Glands and ducts SM Prostatic concretions
Because of the complex structure of the prostate gland, it is difficult to distinguish between the glands and the ducts, both of which are lined by an epithelium which can vary from simple cuboidal to pseudostratified columnar. Prostatic concretions (corpora amylaceae) are glycoprotein and calcium rich deposits which are characteristic of the prostate, and which increase win number with age. The mucosa underlying the glands is rich in smooth muscle (SM) and elastic fibers.
The enzymatic secretions of the prostate gland help to liquify the semen, enabling the sperm to begin their journey to the egg.

38. Prostate Gland Glands and ducts Smooth muscle and elastic fibers PC
Epithelium
Glands and ducts
Prostate Gland PC
In this section, most of the epithelium is pseudostratified with tall columnar cells and round basal cells. The extensive smooth muscle in the mucosa is clearly seen. A prostatic concretion (PC) is also seen.

39. Bulbourethral gland prostate gland seminal vesicle ampulla urethra
epididymis
efferent
ducts
rete testis
b-u gland
vas deferens
The bulbourethral gland opens into the urethra. During sexual arousal, this gland secretes a small drop of alkaline fluid which neutralizes the acidity of any urine in the urethra, as well as lubricating the urethra to facilitate the passage of sperm

40. The Penis- has two functions: Urination Reproduction
The penis has two functions: 1. urination and 2. reproduction. When flaccid, the penis is used to eliminate urine through the urethra. When erect, the penis can conduct sperm into the vagina, and thus function in a reproductive mode.

41. The Penis Corpora cavernosa Corpus spongiosum Urethra Tunica albuginea
Skin
erectile tissue
The erectile structures of the penis consist two corpora cavernosa and the corpus spongiosum, through which the urethra passes. These erectile tissues are enclosed in a mass of dense connective tissue, the tunica albuginea, which is important in the process of erection. The erectile tissue consists of numerous interconnected cavernous spaces that are lined with typical vascular endothelium. The trabeculae between these spaces contain fibroelastic elastic tissue and smooth muscle. The penis becomes erect when the cavernous spaces are distended with blood.

42. Penis: Erectile Tissue
endothelial cells line cavernous spaces
elastic fibers and smooth muscle
trabeculae

43. The Penis Blood flow to corpus cavernosa and mechanism of erection
Helicine artery
In order to get an erection, several parts of the body must work together. The brain sends a message of sexual arousal through the nervous system to the penis. This message causes the muscles surrounding the arteries to the penis to relax. This allows the artery to the penis to dilate to twice its diameter, increasing the blood flow sixteen fold. Additionally, veins which carry blood away from the penis are blocked both by narrowing, and by constriction against the tunica albuginea, thus reducing blood flow out of the penis. Erection is maintained as long as blood flow out of the penis is less than blood flow through the arteries and into the erectile tissues of the corpora cavernosa. The corpus spongiosum plays a minor role in erection.
As a result, the two spongy-tissue chambers in the shaft of the penis fill with blood and the penis becomes firm. A breakdown in any of these systems makes getting or keeping an erection difficult.

44. Mechanism of action of Viagra
Penile vascular smooth
muscle cell relaxation
(Loss of erection)
GTP
Viagra is an inhibitor of beta- phosphodiesterase 5 (PDE-5) thus inhibiting the hydrolysis of cGMP tp GMP. As long ascGMP levels remain high in the smooth muscle surrounding the arterioles in the penis, erection will be mainatained.

45. See, the problem is that God gives men a brain
and a penis and only enough blood to run one
of them at a time.
Robin Williams

46. Semen Semen consists of spermatozoa and secretions of
the accessory sex glands, which follow one another in a
definite sequence:
During arousal:
Bulbourethral gland secretes mucous-like secretion
which lubricates the urethra
At ejaculation:
1. Prostate gland secretion—proteolytic enzyme
rich
2. Spermatazoa are ejected
3. Seminal vesicle secretion follows—nutrient rich
NB: Spermatozoa comprise only 5% of semen

47. It’s been great—but it’s time
Thank you
It’s been great—but it’s time
to be going home
(my wife’s wondering where I’ve gone!)
bon voyage et bonne chance!