A detailed Physiology of Male Reproductive Organs and the mechanism by which Erection and Ejaculation takes place.

1. Functions Of Male Reproductive
Organs, Spermatogenesis and
Mechanism Of Erection &
Ejaculation.
Saadiya
Naeemi
SBB Dewan University,
Dewan Institute Of Rehabilitation Sciences.

2. I- Primary Sex Organ:
Testis.
II- Reproductive Tract:
Epididymis.
Vas Deferens.
Spermatic cord.
III- Accessory Sex Glands:
Seminal vesicles.
Prostate gland.
Bulbourethral glands.
IV- External Genitalia:
Penis
Components Of Male Reproductive System

3.  An out pouching of loose
skin & superficial fascia.
The Left scrotum is
slightly lower than the
right.
 Functions:
 Houses & Protects the
testis
 Regulates testicular
temperature (no
superficial fat )
 It has thin skin with
sparse hairs and sweat
glands.
Scrotum

4. The scrotum contains three
major (paired) structures:
Testis – the site of sperm
production.
Epididymis – situated at
the head of each testicle. It
functions as a storage
reservoir for sperm.
Spermatic cord – a
collection of muscle fibres,
vessels, nerves and ducts
that run to and from the
testes.
Scrotum

5. • Paired almond-shape gonads
that suspended in the scrotum
by the spermatic cord.
• Its volume is about 20-25 ml.
• 4 - 5 cm long
• Weigh (10.5 – 14 g.).
• Functions:
 Spermatogenesis.
 Hormone production:
 (Androgens--testosterone)
 Testis or Testicle (singular),
Testes (plural).
Testes:

6. • Fibrous septae extend from the
capsule, divide the testis into a
(200-300) -average 250- lobules.
• Each lobule contains, (1-3)
seminiferous tubules.
 Seminiferous Tubules: (60 cm coiled
tubule).
 They are the site of the
spermatogenesis.
 They form the bulk of testicular
tissue.
 Interstitial cells of Leydig secret
Testosterone.
Internal Structure of The
Testis

7.  Seminiferous Tubules:
•Maintain environment for
spermatogonia by the basal lamina
and the Sertoli cells
Sertoli cells separate the lumen
from the basal lamina and create a
blood-testis barrier
Creates three compartments
Lumen – low glucose, high K+
& steroid hormones
Basal compartment – the
baso-
lateral side of the sertoli cells &
containing the developing
spermatogonia
Interstitial fluid space –
below the
basal lamina and contains the
Leydig
cells
•Produce hormones/paracrines
From Sertoli cells
From Leydig cells
Internal Structure of The
Testis

8. Seretoli Cells:
Produce hormones &
paracrines involved with
control of hypothalamus-
pituitary-gonad and the
testes directly.
Anti-Müllerian Hormone
(AMH)
Secreted during
embryogenesis
Inhibin & activin
Regulate FSH release from
anterior pituitary
inhibin decreases FSH
release
activin increases LH
function & increases
FSH release

9. Seretoli Cells:
Androgen Binding
Protein (ABP)
Binds to testosterone and
DHT(Dihydrotestosterone
), resulting in an increase
in testicular testosterone
levels
Estradiols & Aromatase
Support spermatogenesis
GDNF (glial derived
neurotrophic factor) & ERM
transcription factor
Maintenance of the stem
cell line

10. Leydig Cells:
Produce androgens
testosterone, androstenedione
and dehydroepiandrosterone
(DHEA)
•Increase
spermatogenesis
Influence secondary
sexual characteristics
Stimulated to produce
androgens by luteinizing hormone
(LH)
•FSH increases the response
to LH by Leydig cells

11. Epididymis:
 A Single coiled tubule
 6 Meters long.
 Located on the superior and
posterior margins of the
testis.
 It is divided into 3 parts:
• Head, Body and Tail.
• The Head receives (rete testis)
efferent ductules from the testis.
 The Tail is continuous with Vas
Deferens.

12. Epididymis:
Functions:
1. Secretes/absorbs the
nourishing fluid.
2. Recycles damaged
spermatozoa.
3. Stores spermatozoa Up to 2
weeks to allow for maturation.

13. Vas Defarans:
 A muscular tube 45 cm long.
 Carries sperms from the
epididymis to pelvic cavity.
 It joins the duct of the seminal
vesicle to form ejaculatory duct
which opens in the prostatic
urethra.

14. Accessory Glands:
 Seminal vesicle.
 Bulbourethral or
Cooper’s glands.
 Prostate.
 Functions:
1. Secretion of seminal
fluid.
2. Nourishing,
activation of
sperms.
3. Protection of
sperms.

15. Accessory Glands:
Seminal Fluid
Components,
Function and Location

16. Seminal Vesicle:
 Paired elongated glands.
 Secrete (60% of Semen)

17. Ejaculatory Ducts:
• Formed by the union of
the lower end of the vas
deferens and the duct of
the seminal vesicle.
• Its length is about 2.5cm.
• The 2 ejaculatory ducts
open into the prostatic
urethr.
• They drain the seminal
fluid into the prostatic
urethra.

18. Prostate Glands:
The Largest male accessory gland.
 It secretes enzymes which
has the following functions:
 Aid in activating sperm
motility
 Mucus degradation
 Neutralize female reproductive
tract (Alkaline fluid )

19. Bulbourethral (Cooper’s)
Gland:
 Small paired glands
 Located at the base of the penis.
 Secrete alkaline mucus for:
Neutralization of urinary acids &
 Lubrication during sexual
arousment.
 The bulbourethral glands
contract during ejaculation.
This is therefore
a sympathetic function, as
opposed to
the parasympathetic control
of erection .

20. Male Urethra:
15-
20cm
long
Four parts:
The male
urethra is
the conduit
for semen
during sexua
l intercourse
Pre-prostatic.
Prostatic.
Membranous.
Spongy.

21. Penis:
Composed mainly of spongy tissue
Becomes erect due to blood
accumulation in its cylinders
If relatively small when flaccid, likely to
greatly expand when erect
Enhanced at considerable risk
The glans (head) has many nerve
endings.

22. Muscles Of Penis:
There are four muscles located in the root of the
penis:
Bulbospongiosus (x2)
associated with the bulb of the penis.
It contracts to empty the spongy
urethra of any residual semen and
urine.
The anterior fibres also aid in
maintaining erection by increasing the
pressure in the bulb of the penis.
Ischiocavernosus (x2)
It contracts to force blood -this helps
maintain erection.

23. Organs involved in the Production of
Semen:
• Seminal Fluid/: Volume of a typical
ejaculation is 2.5 –5.0ml with a
sperm count of 50 –150 million
sperm (under 20 million sperm is
considered infertile), fluid is slightly
alkaline at pH 7.2 –7.7.
• Seminal Vesicles: Produce 60% of
the volume of seminal fluid; SV’s
produce an alkaline viscous fluid
that contains: fructose,
prostaglandins, and clotting
proteins.

24. Organs involved in the Production of
Semen:
• Prostate Gland: Produce 25% of
the volume of seminal fluid; This
fluid is a milky, slightly acidic fluid
that contains citric acid (for ATP
production), acid phosphatase along
with several other enzymes (
prostate-specific antigen PSA,
pepsinogen, and lysozyme
• Bulbo-urethral gland: produces
alkaline mucus that help lubricate
the urethra and the head of the
penis
• Ampulla of ductus deferens:
releases up to 150 million sperm
cells

25. Spermatogenesis:
• The process by which sperm develop to become mature sperm, capable of
fertilizing an ovum.
•Phases of spermatogenesis
Proliferative: spermatogonia divide to replace their numbers; or produce daughter cells
committed to becoming spermatocytes
Type A spermatogonia.
Meiotic: reduction division resulting in haploid spermatids
Type B spermatogonia
Spermiogenic: spermatids undergo changes to form mature spermatozoa.
Entire process requires 64 days (Ap spermatogonium  spermatozoon).
Hormonal Regulation of Spermatogenesis
Intratesticular Testosterone levels are 100 x greater than serum levels
Testosterone will initiate & qualitatively maintain spermatogenesis in humans

26. Spermatogenesis:
• After ejaculation, the sperm can live for about 48 hours in the
female reproductive tract.
• The sperm are released into the lumen of the seminiferous
tubule and leave the testes. They then enter the epididymis
where they undergo their final maturation and become capable
of fertilizing a female gamete.

27. Mechanism Of Erection:
• An erection is a physiological phenomenon in which the penis
becomes firmer, engorged and enlarged.
• erection is triggered by
 the parasympathetic division of the autonomic nervous
system (ANS),
 causing nitric oxide (a vasodilator) levels to rise in
the trabecular arteries and smooth muscle of the penis.
 The arteries dilate causing the penis to fill with blood; simultaneously
the ischiocavernosus and bulbospongiosus muscles compress
the veins of the corpora cavernosa
 restricting the egress and circulation of this blood. Erection subsides
when parasympathetic activity reduces to baseline.

28. Mechanism Of Erection:
• As an autonomic nervous
system response, an erection
may result from a variety of
stimuli, including sexual
stimulation and sexual arousal.
• It is therefore not entirely
under conscious control.
• Erections during sleep or upon
waking up are known
as nocturnal penile
tumescence (NPT).

29. Mechanism Of Ejaculation:
• The process of ejaculation can be divided into two distinct phases:
emission and expulsion.
• Emission:
• The initial step in emission commences with closure of the bladder neck due to
sympathetic innervation. This action prevents the retrograde flow of ejaculate
into the bladder. After bladder neck closure, secretion of fluid from the prostate,
laden with acid phosphatase, citric acid, and zinc mixes with spermatozoa-rich
fluid from the vas deferens in the prostatic urethra.
• Subsequent contribution of seminal vesicle fluid replete with fructose alkalinizes
the final ejaculatory product.

30. Mechanism Of Ejaculation:
• Expulsion:
• The expulsion phase follows the emission phase.
• Relaxation of the external urinary sphincter (with a closed bladder neck) is followed
by clonic contractions of the prostate, bulbospongiosus muscle, ischiocavernosus,
levator ani, and transverse perineal muscles [6–8].
• Through rhythmic contractions lasting 0.6–1.0 s with latency time of 0.7 s between,
and a total mean duration of contraction lasting 4.2 s, semen is expelled from the
urethra.

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