anatomy and physiology of male reproductive system

1. MALE REPRODUCTIVE SYSTEM
BY
SONI KUMARI SHAH

2. Reproduction
Reproduction is the process of producing own kinds of off springs to
maintain the continuity of race. In human beings, sexual type of
reproduction takes place and for this type of reproduction male and
female reproductive system are required.

3. Male Reproductive System
The male reproductive system consists of the organs that produce,
transfer, and introduce mature sperm into the female reproductive
tract, where fertilization occurs.

4. Organs Of Male Reproductive System
Testes
Scrotum
Penis
Urethra
Epididymis
Vas deferens
Spermatic cord
Seminal vesicle
Ejaculatory duct
Prostate gland
Bulbourethral gland

5. Functions Of The Male Reproductive Organs
production, maturation and storage of spermatozoa
delivery of spermatozoa in semen into the female reproductive
tract.
The urethra is also the passageway for urine excretion.

6. Scrotum
The scrotum is a pouch of pigmented skin, fibrous and connective
tissue and smooth muscle.
It is divided into two compartments, each of which contains one
testis, one epididymis and the testicular end of a spermatic cord.
It lies below the symphysis pubis, in front of the upper parts of the
thighs and behind the penis.

7. Testes
The testes are the male
reproductive glands and are the
equivalent of the ovaries in the
female. They are about 4.5 cm
long, 2.5 cm wide and 3 cm thick
and are suspended in the scrotum
by the spermatic cords. They are
surrounded by three layers of
tissue.

8. Layers Of Testis
Tunica vaginalis: This is a double membrane, forming the outer
covering of the testes, and is a downgrowth of the abdominal and
pelvic peritoneum.
Tunica albuginea: This is a fibrous covering beneath the tunica
vaginalis. Ingrowths form septa, dividing the glandular structure of
the testes into lobules.
Tunica vasculosa: This consists of a network of capillaries
supported by delicate connective tissue.

9. Structure Of Testes
In each testis are 200–300 lobules, and within each lobule are 1–4
convoluted loops of germinal epithelial cells, called seminiferous
tubules.
Between the tubules are groups of interstitial cells (of Leydig) that
secrete the hormone testosterone after puberty.
At the upper pole of the testis the tubules combine to form a single
tubule. This tubule, about 6 m in its full length, is repeatedly folded and
tightly packed into a mass called the epididymis.
It leaves the scrotum as the deferent duct (vas deferens) in the

10. Contents Of Spermatic Cord
Vas deferens.
Testicular artery.
Artery of the ductus deferens.
Cremasteric artery.
Pampiniform plexus.
Genital branch of the genitofemoral nerve.
Parasympathetic and sympathetic nerves.
Lymphatic vessels.

11. Functions Of Testes
Spermatozoa (sperm) are produced in the seminiferous tubules
of the testes, and mature as they pass through the long and
convoluted epididymis, where they are stored.
FSH from the anterior pituitary stimulates sperm production.
A mature sperm has a head, a body, and a long whip-like tail
used for motility.

12. Functions Of Testes
Successful spermatogenesis takes place at a temperature about 3°C below
normal body temperature.
The dartos muscle, a smooth muscle in the superficial fascia, causes
scrotal skin to wrinkle, which helps to regulate temperature.
The cremaster muscle, rising from the internal oblique muscle, helps to
govern temperature by elevating the testes.
The testes are cooled by their position outside the abdominal cavity, and
the thin outer covering of the scrotum has very little insulating fat.

13. Blood Supply, Lymph Drainage And Nerve Supply Of Testes
Arterial supply
The testicular artery branches from the abdominal aorta.
Venous drainage
The testicular vein passes into the abdominal cavity. The left vein opens
into the left renal vein and the right into the inferior vena cava.
Lymph drainage
This is through lymph nodes around the aorta.
Nerve supply
This is provided by branches from the 10th and 11th thoracic nerves.

14. Duct System
The male reproductive duct system,
consisting of the epididymis and vas
deferens, conveys sperm from the
testes to the ejaculatory ducts near the
bladder.

15. Epididymis
The epididymis is a coiled tube located
superior to and along the posterior
border of the testis. During
ejaculation, smooth muscle in the
epididymis contracts, ejecting
spermatozoa into the vas deferens.

16. The Deferent Duct or Vas
Deferens
This is some 45 cm long. It
passes upwards from the testis
through the inguinal canal and
ascends medially towards the
posterior wall of the bladder
where it is joined by the duct from
the seminal vesicle to form the
ejaculatory duct.

17. Seminal Vesicles
The seminal vesicles are two small
fibromuscular pouches, 5 cm long,
lined with columnar epithelium and
lying on the posterior aspect of the
bladder. At its lower end each
seminal vesicle opens into a short
duct, which joins with the
corresponding deferent duct to form
an ejaculatory duct.

18. Functions Of Seminal Vesicle
The seminal vesicles contract and expel their stored contents,
seminal fluid, during ejaculation.
Seminal fluid, which forms 60% of the volume of semen, is
alkaline to protect the sperm in the acidic environment of the
vagina, and contains fructose to fuel the sperm during their
journey through the female reproductive tract.

19. Ejaculatory Ducts
The ejaculatory ducts are two tubes about
2 cm long, each formed by the union of the
duct from a seminal vesicle and a deferent
duct.
They pass through the prostate gland and
join the prostatic urethra, carrying seminal
fluid and spermatozoa to the urethra.
The walls of the ejaculatory ducts are
composed of the same layers of tissue as
the seminal vesicles.

20. Accessory Reproductive Glands
The accessory reproductive glands,
which produce most of the semen,
include the seminal vesicles,
bulbourethral glands (Cowper’s
glands), and the prostate gland. The
seminal vesicles are paired sacs at the
base of the bladder. The bulbourethral
glands, also paired, are located inferior
to the prostate.

21. Prostate Gland
The prostate gland lies in the pelvic cavity in front of the rectum and
behind the symphysis pubis, completely surrounding the urethra as it
emerges from the bladder.
It has an outer fibrous covering, enclosing glandular tissue wrapped in
smooth muscle.
The gland weighs about 8 g in youth, but progressively enlarges
(hypertrophies) with age and is likely to weigh about 40 g by the age of 50.

22. Functions Of Prostate Gland
The prostate gland secretes a thin, milky fluid that makes up about 30% of the
volume of semen, and gives it its milky appearance.
It contains a clotting enzyme, which thickens the semen in the vagina,
increasing the likelihood of semen being retained close to the cervix.
The prostate continuously secretes prostatic fluid, a thin, milky, alkaline fluid.
During sexual activity, prostatic fluid adds volume to the semen. The fluid
enhances sperm motility and may increase the chances for conception by
neutralizing the acidity of the man’s urethra and the woman’s vagina.
.

23. Semen
Semen is a viscous, white secretion with a slightly alkaline pH (7.8 to 8);
it consists of spermatozoa and accessory gland secretions.
The seminal vesicles produce roughly 60% of the fluid portion of the
semen, while the prostate gland produces about 30%.
A viscid fluid secreted by the bulbourethral glands also becomes part of
the semen

24. Bulbourethral Gland Or Cowper’s Gland
Pair of pea shaped compound tubule-alveolar exocrine gland which lies beneath
the prostate gland. Its secretion is drained by a 2.5cm long duct which opens into
penile urethra at the bulb of penis.
Function
It secretes alkaline pre-ejaculate fluid during sexual
stimulation/arousal. It acts as lubricant for vagina for
smooth movement of penis during coitus.
It helps to lubricate the passage of semen.
It helps to neutralize the traces of acidic urine in urethra.
It also secrets prostate specific antigen(PSA).

25. Urethra
The male urethra provides a common pathway for the flow of urine and
semen. It is about 19–20 cm long and consists of three parts.
The prostatic urethra originates at the urethral orifice of the bladder and
passes through the prostate gland.
The membranous urethra is the shortest and narrowest part and
extends from the prostate gland to the bulb of the penis, after passing
through the perineal membrane.
The penile urethra or spongy urethra lies within the corpus spongiosum
of the penis and terminates at the external urethral orifice in the glans
penis. It makes up about 75% of the entire urethra.

26. Urethra
There are two urethral sphincters.
The internal sphincter is a ring of smooth
muscle at the neck of the bladder above
the prostate gland.
The external sphincter is a ring of skeletal
muscle surrounding the membranous
part

27. Penis
The penis has a root and a shaft.
The root anchors the penis in the perineum
and the shaft (body) is the externally
visible, moveable portion of the organ.
At its tip it is expanded into a triangular
structure known as the glans penis.
Just above the glans the skin is folded upon
itself and forms a movable double layer,
the foreskin or prepuce.

28. Penis
It is formed by three cylindrical masses of
erectile tissue and smooth muscle.
The erectile tissue is supported by fibrous
tissue and covered with skin and has a rich
blood supply.
The two lateral columns are called the
corpora cavernosa and the column
between them, containing the urethra, is
the corpus spongiosum.

29. Erection
Arterial blood is supplied by deep, dorsal and bulbar arteries of the penis,
which are branches from the internal pudendal arteries.
A series of veins drain blood to the internal pudendal and internal iliac veins.
The penis is supplied by autonomic and somatic nerves.
Parasympathetic stimulation leads to filling of the spongy erectile tissue with
blood, caused by arteriolar dilation and venoconstriction, which increases
blood flow into the penis and obstructs outflow.
The penis therefore becomes engorged and erect, essential for sexual
intercourse.

30. Ejaculation
During ejaculation, which occurs at male orgasm, spermatozoa are expelled
from the epididymis and pass through the deferent duct, the ejaculatory
duct and the urethra.
The semen is propelled by powerful rhythmical contraction of the smooth
muscle in the walls of the deferent duct; the muscular contractions are
sympathetically mediated.
Muscle in the walls of the seminal vesicles and prostate gland also contracts,
adding their contents to the fluid passing through the genital ducts.
The force generated by these combined processes leads to emission of the
semen through the external urethral sphincter

31. Ejaculation
Sperm comprise only 10% of the final ejaculate, the remainder being
made up mainly of seminal (50–60%) and prostatic fluids (20–30%),
which are added to the sperm during male orgasm, as well as mucus
produced in the urethra.
Semen is slightly alkaline, to neutralize the acidity of the vagina.
Between 2 and 5 mL of semen are produced in a normal ejaculate, and
contain between 40and 100 million spermatozoa per ml.
If not ejaculated, sperm gradually lose their fertility after several months
and are reabsorbed by the epididymis.

32. Path Of Sperm Cells From Their Origin To Their Exit From The Body

33. Spermatogenesis
Sperm formation, or spermatogenesis, begins when a male reaches
puberty and normally continues throughout life.
Spermatogenesis occurs in four stages:
In the first stage, the primary germinal epithelial cells, called
spermatogonia, grow and develop into primary spermatocytes. Both
spermatogonia and primary spermatocytes contain 46 chromosomes,
consisting of 44 autosomes and the two sex chromosomes, X and Y.

34. Spermatogenesis
Next, primary spermatocytes divide to form secondary spermatocytes.
No new chromosomes are formed in this stage; the pairs only divide.
Each secondary spermatocyte contains one-half the number of
autosomes, 22. One secondary spermatocyte contains an X
chromosome; the other, a Y chromosome.
In the third stage, each secondary spermatocyte divides again to form
spermatids.
Finally, the spermatids undergo a series of structural changes that
transform them into mature spermatozoa, or sperm.

35. Spermatogenesis
Each spermatozoa has a head, neck, body, and tail. The head contains the
nucleus; the tail, a large amount of adenosine triphosphate, which provides
energy for sperm motility.
New sperm pass from the seminiferous tubules through the vasa recta into the
epididymis, where they mature.
Only a small number of sperm can be stored in the epididymis. Most of them
move into the vas deferens, where they’re stored until sexual stimulation
triggers emission.
Sperm cells retain their potency in storage for many weeks. After ejaculation,
sperm can survive for up to 4 days in the female reproductive tract.

36. Spermatogenesis
Primary spermatocytes

37. Structure Of Sperm
A mature sperm has a head, a body, and a long
whip-like tail used for motility.
The head is almost completely filled by the
nucleus, containing its DNA. It also contains the
enzymes required to penetrate the outer layers
of the ovum to reach, and fuse with, its nucleus.
The body of the sperm is packed with
mitochondria, to fuel the propelling action of the
tail that powers the sperm along the female
reproductive tract.
The tail is several times longer than the head.
The sperm swim by its tail in a fluid medium.

38. Male Hormonal Control And Sexual Development
Androgens (male sex hormones) are produced in the testes and the
adrenal glands. They’re responsible for the development of male sex
organs and secondary sex characteristics.
Major androgens include:
Testosterone
Luteinizing Hormone (LH)
Follicle-stimulating Hormone (FSH).

39. Male Hormonal Control And Sexual Development
Leydig’s cells, located in the testes between the seminiferous tubules,
secrete testosterone, the most significant male sex hormone.
Testosterone is responsible for the development and maintenance of
male sex organs and secondary sex characteristics, such as facial hair and
vocal cord thickness.
Testosterone is also required for spermatogenesis.

40. Testosterone
Testosterone secretion begins approximately 2 months after conception, when the
release of chorionic gonadotropins from the placenta stimulates Leydig’s cells in the
male fetus.
The presence of testosterone directly affects sexual differentiation in the fetus.
With testosterone, fetal genitalia develop into a penis, scrotum, and testes; without
testosterone, genitalia develop into a clitoris, vagina, and other female organs.
During the last 2 months of gestation, testosterone normally causes the testes to
descend into the scrotum.
If the testes don’t descend after birth, exogenous testosterone may correct the
problem

41. Male Hormonal Control And Sexual Development
Other hormones also affect male sexuality. Two of these, LH (also called
interstitial cell-stimulating hormone) and FSH, directly affect secretion of
testosterone.
During early childhood, gonadotropins aren’t secreted and there is little
circulating testosterone.
Secretion of gonadotropins from the pituitary gland usually occurs between
ages 11 and 14, and marks the onset of puberty.
These pituitary gonadotropins stimulate testis functioning as well as
testosterone secretion.

42. Puberty In The Male
During puberty, the penis and testes enlarge and the male reaches full
adult sexual and reproductive capability.
This occurs between the ages of 10 and 14.
Luteinizing hormone from the anterior lobe of the pituitary gland
stimulates the interstitial cells of the testes to increase the production
of testosterone.
Under the influence of testosterone, sexual maturation and other
characteristic changes take place

43. Hormonal Control Of Male Reproductive Function

44. Characteristics Changes in Puberty In The Male
growth of muscle and bone and a marked increase in height and weight
enlargement of the larynx and deepening of the voice – it ‘breaks’
growth of hair on the face, axillae, chest, abdomen and pubis
enlargement of the penis, scrotum and prostate gland
maturation of the seminiferous tubules and production of spermatozoa
the skin thickens and becomes oilier.
After a male achieves full physical maturity, usually by age 20, sexual and
reproductive function remain fairly consistent throughout life.

45. Male Reproductive Changes With Aging
Physiologic changes in older men include reduced testosterone
production which, in turn, may cause decreased libido.
A reduced testosterone level also causes the testes to atrophy and
soften and decreases sperm production by 48% to 69% between ages
60 and 80.
Normally, the prostate gland enlarges with age and its secretions
diminish. Seminal fluid also decreases in volume and becomes less
viscous.

46. Ageing And Reproduction In The Male
There is no equivalent of the female menopause in the older male.
Although testosterone secretion tends to decline after age 50,
leading to a relative reduction in fertility and sexual desire, it is
usually sufficient to maintain sperm production and a man may still
be able to father a child until extreme old age.
Sexual Changes
During intercourse, older men experience slower and weaker physiologic
reactions. However, these changes don’t necessarily lessen sexual
satisfaction.

47. Vasectomy
Vasectomy is a surgical procedure for male sterilization
or permanent contraception. During the procedure, the
male vas deferent are cut and tied or sealed so as to
prevent sperm from entering into the urethra and
thereby prevent fertilization of a female through sexual
intercourse.

48. Male Infertility
This may be due to endocrine disorders, obstruction of the
deferent duct, failure of erection or ejaculation during
intercourse, vasectomy, or suppression of spermatogenesis by,
e.g. ionizing radiation, chemotherapy and other drugs.

49. Spermatogenesis is the:
A. growth and development of sperm into primary spermatocytes.
B. division of spermatocytes into secondary spermatocytes.
C. passage of sperm into the epididymis.
D. entire process of sperm formation.
The primary function of the scrotum is to:
A. provide storage for newly developed sperm.
B. maintain a cool temperature for the testes.
C. deposit sperm in the female reproductive tract.
D. secrete prostatic fluid.
What are male gametes called?
A. ova
B. sperm
C. testes
D. testosterone

50. Leydig cells ________.
a. secrete testosterone
b. activate the sperm flagellum
c. support spermatogenesis
d. secrete seminal fluid
Which hypothalamic hormone contributes to the regulation of the
male reproductive system?
a. luteinizing hormone
b. gonadotropin-releasing hormone
c. follicle-stimulating hormone
d. androgens

51. What is the function of the epididymis?
a. sperm maturation and storage
b. produces the bulk of seminal fluid
c. provides nitric oxide needed for erections
d. spermatogenesis
Spermatogenesis takes place in the ________.
a. prostate gland
b. glans penis
c. seminiferous tubules
d. ejaculatory duct