3. Male sexual response
Erection is enlargement and stiffening of
the penis, resulting from engorgement of
the erectile bodies with blood, and
innervated by the parasympathetic division
of the autonomic nervous system.
4. Ejaculation is the propulsion of semen from
the male duct system, innervated by the
sympathetic division of the autonomic
nervous system.
5. Orgasm is a state of muscular and
psychological relaxation and
vasoconstriction of the penile arterioles,
which allows the penis to become flaccid
once again.
6. Spermatogenesis
Spermatogenesis is the sequence of events
in the seminiferous tubules of the testes that
leads to the production of male gametes
called sperm (spermatozoa).
Spermatogenic cells are epithelia from the
walls of the seminiferous tubules that give
rise to sperm.
7.
8. Spermatogonia are stem cells that are the
outermost and least differentiated tubule
cells, that give rise to type A and B
daughter cells.
9. Type A daughter cells remain at the
basement membrane to maintain the germ
cell line.
Type B daughter cells get pushed toward
the lumen, where they become primary
spermatocytes destined to produce four
sperm.
10. Each primary spermatocyte generated
during the first phase undergoes meiosis I,
forming two smaller haploid cells called
secondary spermatocytes.
The secondary spermatocytes proceed to
meiosis II, and their daughter cells, called
spermatids, are small round cells with large
nuclei.
11. Spermatids most undergo a streamlining
process called spermiogenesis, during
which they shed most of their cytoplasm
and grow a tail, which results in the
formation of a sperm (spermatozoan).
12. The head of a sperm consists almost
entirely of its nucleus.
Adhering to the top of the nucleus is an
acrosome, which contains hydrolytic
enzymes that enable the sperm to penetrate
and enter an egg.
13.
14. The sperm midpiece contains mitochondria
spiraled around the contractile filaments of
the tail.
The tail is a flagellum with an attached
centriole, that propels the sperm in the
female reproductive tract.
15. Descendants of the same spermatogonium
remain closely attached to one another, and
are surrounded by and connected to
supporting cells called sustentacular
(Sertoli) cells.
16. The basal compartment is a region of the
seminiferous tubule that contains
spermatogonia.
The adluminal compartment lies internal to
the tight junctions of the seminiferous
tubule and includes the meiotically active
cells and the tubule lumen.
17. The tight junctions between the
sustentacular cells form the blood-testis
barrier, which prevents the membrane
antigens of differentiating sperm from
escaping through the basal lamina into the
bloodstream.
18. The sustentacular cells secrete testicular
fluid that provides the transport medium for
sperm in the lumen, and dispose of the
excess cytoplasm sloughed off the
spermatids as they transform into sperm.
19. Hormonal regulation of male
reproductive function
Hormonal regulation of spermatogenesis
and testicular androgen production involves
interactions between the hypothalamus, the
anterior pituitary gland, and testes (brain-
testicular axis).
20.
21. The hypothalamus releases gonadotropin-
releasing hormone (GnRH), which controls
the release of the anterior pituitary
gonadotropins, follicle-stimulating
hormone, and luteinizing hormone.
22. FSH stimulates spermatogenesis in the
testes indirectly by stimulating the
sustentacular cells to release androgen-
binding protein (ABP), which prompts the
spermatogenic cells to bind and concentrate
testosterone.
23. LH, also known as interstitial cell-
stimulating hormone, binds to the interstitial
cells and stimulates them to secrete
testosterone.
Testosterone inhibits hypothalamic release
of GnRH, and acts directly on the anterior
pituitary to inhibit gonadotropin release.
24. Inhibin is a protein hormone produced by
the sustentacular cells, which is released
when the sperm count is high, inhibiting
anterior pituitary release of FSH, and GnRH
release by the hypothalamus.
26. Oogenesis
The production of female sex cells is called
oogenesis.
The oogonia are diploid stem germ cells of
the ovaries, that multiply rapidly by mitosis
and then enter a growth phase, during
which they lay in nutrient reserves.
27.
28. Primordial follicles begin to appear as the
oogonia are transformed into primary
oocytes, which begin the first meiotic
division , but become dormant late in
prophase I.
29. One primary oocyte continues meiosis I
each month, and produces two haploid cells,
the smaller of which is called the first polar
body, and the larger, which contains most
of the cytoplasm is called the secondary
oocyte.
30. If a secondary oocyte is penetrated by a
sperm, it completes meiosis II, yielding one
large ovum and a tiny second polar body.
31. The ovarian cycle
The monthly series of events associated
with the maturation of an egg is called the
ovarian cycle.
The follicular phase of the ovarian cycle is
the period of follicle growth, and lasts from
the first to the fourteenth day of the cycle.
32. The luteal phase is the period of corpus
luteum activity, which occurs during days
14-28.
Most ovarian cycles repeat every 28 days,
with ovulation occurring mid-cycle.
33.
34. A primary follicle is formed when the cells
of the primordial follicle proliferate, and the
oocyte enlarges.
When more than one cell layer is present in
the primary follicle, the cells are called
granulosa cells.
35. In the next phase, a layer of connective
tissue begins to condense around the
follicle, forming the theca folliculi.
The granulosa cells secrete a glycoprotein-
rich substance that forms a thick transparent
membrane called the zona pellucida, which
surrounds the oocyte.
36. During the next phase, a clear liquid
accumulates between the granulosa cells,
and eventually coalesces to form a fluid-
filled cavity called the antrum.
The antrum isolates the oocyte, along with
its surrounding capsule of granulosa cells
called a corona radiata, on a stalk on one
side of the follicle.
37. Ovulation occurs when the ballooning
ovary wall ruptures and expels the
secondary oocyte into the peritoneal cavity.
After ovulation and discharge of the antrum
fluid, the ruptured follicle collapses, and the
antrum fills with clotted blood, which is
eventually absorbed.
38. The hormonal regulation of the
ovarian cycle
At the onset of puberty, the hypothalamus
begins to release GnRH, which stimulates
the release FSH and LH by the pituitary.
Gonadotropin levels continues to increase
for a few years, and eventually the adult
cyclic pattern is achieved which leads to the
initial establishment of menstrual function,
called menarche.
39.
40. The uterine cycle
The uterine cycle, also referred to as
menstrual cycle, is a series of cyclic
changes that uterine endometrium goes
through each month as it responds to
changing levels of ovarian hormones in the
blood.
41.
42.
43. Events of the three-stage uterine
cycle
Menstrual phase, days 1-5: The uterus sheds
all but the deepest part of its endometrium.
Proliferative phase, days 6-14: The basal
layer of the endometrium rebuilds itself,
under the influence of rising blood levels of
estrogen, and generates a new functional
layer.
44. Ovulation occurs in the ovary at the end of
the proliferative phase in response to the
sudden release of LH from the anterior
pituitary.
Secretory phase, days 15-28: The
endometrium prepares for implantation of
an embryo.
45. Female sexual response
The female sexual response involves
swelling of the clitoris, vaginal mucosa and
breasts, increased activity of the vestibular
glands, and erection of the nipples, which
may ultimately result in orgasm.
