1. 28-1 Structures of the Reproductive System
The Male Reproductive System
Testes or male gonads
Secrete male sex hormones (androgens)
Produce male gametes (spermatozoa or sperm)

2. Figure 28-4a The Structure of the Testes.
Ductus deferens
Epididymis
Mediastinum of testis
Efferent ductule
Rete
testis
Scrotum
Skin
Dartos muscle
Straight
tubule
Superficial
scrotal fascia
Seminiferous
tubules
Cremaster muscle
Tunica vaginalis
Tunica albuginea
Septa
Scrotal cavity
Septa
Lobule
Raphe
A transverse section of
the scrotum and testes a

3. 28-2 Male Reproductive Functions
Spermatogenesis
Is the process of sperm production
Begins at outermost cell layer in seminiferous tubules
Proceeds toward lumen

4. 28-2 Male Reproductive Functions
Cells of Spermatogenesis
Spermatogonia (stem cells) divide by mitosis to produce two daughter cells
One remains as spermatogonium
Second differentiates into primary spermatocyte
Primary spermatocytes begin meiosis and form secondary spermatocytes

5. 28-2 Male Reproductive Functions
Cells of Spermatogenesis
Secondary spermatocytes differentiate into spermatids (immature gametes)
Spermatids
Differentiate into spermatozoa
Spermatozoa
Lose contact with wall of seminiferous tubule
Enter fluid in lumen

6. Figure 28-5c The Seminiferous Tubules.
Spermatid
Nurse
cell
Dividing
spermatocytes
Capillary
Lumen
Interstitial cells
Spermatogonium
Spermatozoa c c
Nurse cells surround the stem cells of the tubule and support the developing spermatocytes and spermatids.

7. Figure 28-5d The Seminiferous Tubules.
Spermatids completing
spermiogenesis
LUMEN
Spermatids beginning
spermiogenesis
Initial spermiogenesis
Secondary
spermatocyte
Secondary spermatocyte
in meiosis II
Primary
spermatocyte
preparing
for meiosis I
Luminal compartment
Blood–testis
barrier
Nuclei of
nurse cells
Fibroblast
Connective
tissue capsule
Capillary
Interstitial cells
Spermatogonium
Basal compartment d
Stages in spermatogenesis in the wall of a seminiferous tubule. d

8. 28-2 Male Reproductive Functions
Spermatogenesis
Involves three integrated processes
Mitosis
Meiosis
Spermiogenesis

9. 28-2 Male Reproductive Functions
Mitosis
Is part of somatic cell division
Produces two diploid (2n) daughter cells
Both have identical pairs of chromosomes

10. Figure 28-6a Chromosomes in Mitosis and Meiosis.
Mitosis. The fates of three representative
chromosome pairs during mitosis
Cell
(2n)
Chromosomes
Chromosome
duplication 1 2
Chromosomes
of daughter
cell 1
Chromosomes
of daughter
cell 2
Daughter
cells (2n)

11. Figure 28-6b Chromosomes in Mitosis and Meiosis.
Meiosis. The fates of three representative chromosome pairs
during the two stages of meiosis
Cell (2n)
Chromosomes
Tetrad
Chromosome duplication,
synapsis, and
tetrad formation
Meiosis I
Meiosis II 1 2 3 4 1 2 3 4
Chromosomes of gametes
Gametes (n)

12. Figure 28-7 Spermatogenesis (Part 4 of 4).
Spermiogenesis (physical maturation)
In spermiogenesis, the last step of
spermatogenesis, each spermatid matures
into a single spermatozoon, or sperm. The
process of spermiogenesis—from
spermatids to spermatozoa—takes 24 days.
Spermatozoa
(haploid, n)

13. 28-2 Male Reproductive Functions
Six Major Functions of Nurse Cells
Maintain blood–testis barrier
Support mitosis and meiosis
Support spermiogenesis
Secrete inhibin
Secrete androgen-binding protein (ABP)
Secrete Müllerian-inhibiting factor (MIF)

14. 28-2 Male Reproductive Functions
Secretion of Inhibin
Inhibin
Is a peptide hormone secreted by nurse cells in response to factors released by spermatozoa
Depresses:
Pituitary production of FSH
Hypothalamic secretion of GnRH
Regulation of FSH and GnRH by inhibin:
Gives nurse cells feedback control of spermatogenesis
After division, increases inhibin production

15. 28-2 Male Reproductive Functions
Secretion of Androgen-Binding Protein (ABP)
Androgen-Binding Protein (ABP)
Binds androgens (primarily testosterone)
In seminiferous tubule fluid
Is important in:
Elevating androgen in seminiferous tubules
Stimulating spermiogenesis
Production of ABP is stimulated by FSH

16. 28-2 Male Reproductive Functions
Secretion of Müllerian-Inhibiting Factor (MIF)
Müllerian-Inhibiting Factor (MIF)
Is secreted by nurse cells in developing testes
Causes regression of fetal Müllerian (paramesonephric) ducts
Help form uterine tubes and uterus in females
In males, inadequate MIF production leads to:
Retention of ducts
Failure of testes to descend into scrotum

17. Figure 28-8 Spermiogenesis and Spermatozoon Structure (Part 2 of 2).
Tail (55 m)
Fibrous sheath
of flagellum
Middle
piece (5 m)
Spermatozoa
SEM × 780
Mitochondrial
spiral
Neck (1 m)
Centrioles
Nucleus
Head (5 m)
Acrosome
Spermatozoon

18. 28-2 Male Reproductive Functions
The Male Reproductive Tract
Sperm maturation
Testes produce physically mature spermatozoa that CANNOT fertilize an oocyte
Other parts of reproductive system are responsible for:
Functional maturation, nourishment, storage, and transport

19. 28-2 Male Reproductive Functions
The Male Reproductive Tract
Sperm maturation
Spermatozoa
Detach from nurse cells
Are free in lumen of seminiferous tubule
Are functionally immature
Are incapable of locomotion or fertilization
Are moved by cilia lining efferent ductules into the epididymis

20. Figure 28-9a The Epididymis.
Spermatic cord
Ductus deferens
Efferent ductules
Straight tubule
Rete testis
Seminiferous
tubule
Epididymis
Head of epididymis
Tunica
albuginea
Body of epididymis
Testis
Tail of epididymis
Scrotal
cavity a
A diagrammatic view
of the head, body, and
tail of an epididymis

21. 28-2 Male Reproductive Functions
Three Functions of the Epididymis
Monitors and adjusts fluid produced by seminiferous tubules
Recycles damaged spermatozoa
Stores and protects spermatozoa
Facilitates functional maturation

22. 28-2 Male Reproductive Functions
Two Steps in Capacitation
Spermatozoa become motile
When mixed with secretions of seminal glands
Spermatozoa become capable of fertilization
When exposed to female reproductive tract

23. Figure 28-10a The Ductus Deferens and Accessory Glands.
Ureter
Urinary
bladder
Ductus deferens
Seminal gland
Ampulla of
ductus deferens
Duct of
seminal gland
Ejaculatory duct
Prostate gland
Prostatic urethra a
A posterior view of the urinary
bladder and prostate gland,
showing subdivisions of the
ductus deferens in relation
to surrounding structures.
Bulbourethral glands
Urogenital diaphragm

24. 28-2 Male Reproductive Functions
Four Major Functions of Male Glands
Activating spermatozoa
Providing nutrients spermatozoa need for motility
Propelling spermatozoa and fluids along reproductive tract
Mainly by peristaltic contractions
Producing buffers
To counteract acidity of urethral and vaginal environments

25. 28-2 Male Reproductive Functions
Semen
Typical ejaculation releases 2–5 mL
Abnormally low volume may indicate problems
With prostate gland or seminal glands
Sperm count
Is taken of semen collected after 36 hours of sexual abstinence
Normal range 20–100 million spermatozoa/mL of ejaculate

26. 28-2 Male Reproductive Functions
Ejaculate
Is the volume of fluid produced by ejaculation
Contains:
Spermatozoa
Seminal fluid
Enzymes
Including protease, seminalplasmin, prostatic enzyme, and fibrinolysin

27. Figure 28-12 Regulation of Male Reproduction (Part 1 of 2).
Male reproductive function is regulated by the
complex interaction of hormones from the hypothalamus, anterior lobe of the pituitary gland, and the testes. Negative feedback systems keep testosterone levels within a relatively narrow range until late in life.
HYPOTHALAMUS
Release of Gonadotropin-
Releasing Hormone (GnRH)
Negative feedback ?
High testosterone levels
inhibit the release of GnRH
by the hypothalamus,
causing a decrease in
LH secretion, which
lowers testosterone to
normal levels.
The hypothalamus secretes
the hormone GnRH at a rate
that remains relatively steady.
As a result, blood levels of
FSH, LH, and testosterone
remain within a relatively
narrow range throughout a
man’s reproductive life.
When stimulated by GnRH, the anterior lobe of the pituitary gland releases luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
ANTERIOR
LOBE OF THE
PITUITARY
GLAND
Secretion of Follicle-
Stimulating Hormone
(FSH)
Secretion of
Luteinizing
Hormone (LH)
Inhibin depresses the pituitary production of FSH, and perhaps the hypothalamic secretion of gonadotropin-releasing hormone (GnRH).The
faster the rate of sperm production, the more inhibin is secreted. By regulating FSH and GnRH secretion, nurse cells provide feedback control of spermatogenesis.
FSH targets primarily
the nurse cells of the
seminiferous tubules.
LH targets the
interstitial cells
of the testes.
KEY
Stimulation
Inhibition

28. Figure 28-12 Regulation of Male Reproduction (Part 2 of 2).
Interstitial Cell Stimulation
Negative feedback
LH induces the secretion of testosterone and other androgens
by the interstitial cells of the testes.
TESTES
Nurse Cell Stimulation
Testosterone
Under FSH stimulation, and with testosterone from the interstitial cells,
nurse cells (1) secrete inhibin in response to factors released by developing spermatozoa, (2) secrete androgen-binding protein (ABP), and
(3) promote spermatogenesis and spermiogenesis.
Inhibin
KEY
Stimulation
Inhibition
Androgen-binding protein (ABP) binds androgens within the seminiferous tubules, which increases the local concentration of androgens and stimulates the physical maturation of spermatids.
Nurse cell environment facilitates both spermatogenesis and spermiogenesis.
Peripheral Effects of Testosterone
Maintains libido (sexual drive)
and related behaviors
Stimulates
bone and
muscle
growth
Establishes and maintains male secondary sex characteristics
Maintains accessory glands and organs
of the male reproductive system

30. Figure 28-14b The Ovaries and Their Relationships to the Uterine Tube and Uterus.
Corpus
luteum
Cortex
Tunica
albuginea
Mesenteries of
the Ovary and
Uterine Tube
Mesosalpinx
Mesovarium
Broad ligament
Ovarian
hilum
Egg
nest
Germinal
epithelium
Mature
follicle b
A sectional view of the ovary, uterine tube, and associated mesenteries

31. 28-3 The Female Reproductive System
Oogenesis
Also called ovum production
Begins before birth
Accelerates at puberty
Ends at menopause

32. Figure 28-15 Oogenesis (Part 1 of 3).
Mitosis of oogonium
Oogonium
(stem cell)
Unlike spermatogonia, the oogonia
(ō-ō-GŌ-nē-uh), or female reproductive stem cells, complete their mitotic divisions before birth.
Oogonium
Primary
oocyte
(diploid, 2n)

33. Figure 28-15 Oogenesis (Part 2 of 3).
Meiosis I
DNA replication
Between the third and seventh months of fetal development, the daughter cells, or primary oocytes (Ō-ō-sīts), prepare to undergo
meiosis. They proceed as far as the prophase
of meiosis I, but then the process comes to a halt.
Primary
oocyte
Tetrad
First polar
body
The primary oocytes remain in a state of suspended development until puberty, when rising levels of FSH trigger the start of the ovarian cycle. Each month
after the ovarian cycle begins, some of the primary oocytes are stimulated to undergo further development. Meiosis I
is then completed, yielding a secondary oocyte and a polar body.
Secondary
oocyte
First polar body
may not complete
meiosis II

34. Figure 28-15 Oogenesis (Part 3 of 3).
Meiosis II
Secondary oocyte released (ovulation) in metaphase of meiosis II
Each month after the ovarian cycle begins, one or more secondary oocytes leave the ovary suspended in metaphase of meiosis II.
At the time of fertilization, a second polar body forms and the fertilized oocyte is then called a mature ovum. (A cell
in any of the preceding steps in oogenesis is sometimes called an immature ovum.)
Second
polar
body
Sperm
(n)
Nucleus
of oocyte
(n)
Fertilization
(see Figure 29–1)

35. 28-3 The Female Reproductive System
Fetal Development
Between third and seventh months:
Primary oocytes prepare for meiosis
Stop at prophase of meiosis I
Atresia
Is the degeneration of primordial follicles
Ovaries have about 2 million primordial follicles at birth
Each containing a primary oocyte
By puberty:
Number drops to about 400,000

36. 28-3 The Female Reproductive System
Oogenesis: Two Characteristics of Meiosis
Cytoplasm of primary oocyte divides unevenly
Producing one ovum (with original cytoplasm)
And two or three polar bodies (that disintegrate)
Ovary releases secondary oocyte (not mature ovum)
Suspended in metaphase of meiosis II
Meiosis is completed upon fertilization

37. 28-3 The Female Reproductive System
The Ovarian Cycle
After sexual maturation
A different group of primordial follicles is activated each month
Is divided into:
Follicular phase (preovulatory phase)
Luteal phase (postovulatory phase)

38. 28-3 The Female Reproductive System
The Ovarian Cycle
Ovarian follicles
Are specialized structures in cortex of ovaries
Where oocyte growth and meiosis I occur
Primary oocytes
Are located in outer part of ovarian cortex
Near tunica albuginea
In clusters called egg nests

39. 28-3 The Female Reproductive System
Primordial Follicle
Each primary oocyte in an egg nest
Is surrounded by follicle cells
Primary oocyte and follicle cells form a primordial follicle

40. Figure 28-16 The Ovarian Cycle (Part 1 of 7).
Primordial follicles
in egg nest
Primary
oocyte
Follicle
cells
LM ×1440

41. Figure 28-16 The Ovarian Cycle (Part 2 of 7).
Formation of
primary follicle
Granulosa
cells
Primary
oocytes
Zona
pellucida
Thecal
cells
LM ×1092

42. Figure 28-16 The Ovarian Cycle (Part 3 of 7).
Formation of
secondary follicle
Thecal cells
Zona
pellucida
Nucleus
of primary
oocyte
Granulosa
cells
LM ×1052

43. Figure 28-16 The Ovarian Cycle (Part 4 of 7).
Formation of
tertiary follicle
Antrum
containing
follicular
fluid
Granulosa
cells
Corona
radiata
Secondary
oocyte
LM ×136

44. Figure 28-16 The Ovarian Cycle (Part 5 of 7).
Primordial
follicles
Primary
follicle
Secondary
follicle
Tertiary
follicle
Released
secondary
oocyte
Corona
radiata
Corpus albicans
Corpus luteum 5
Ovulation
Follicular
fluid
Secondary
oocyte within
corona radiata
Ruptured
follicle wall
Outer
surface
of ovary
LM ×70

45. 28-3 The Female Reproductive System
The Uterine Cycle (Menstrual Cycle)
Is a repeating series of changes in endometrium
Lasts from 21 to 35 days
Average 28 days
Responds to hormones of ovarian cycle
Menses and proliferative phase
Occur during ovarian follicular phase
Secretory phase
Occurs during ovarian luteal phase

46. 28-3 The Female Reproductive System
Menses
Is the degeneration of functional zone
Occurs in patches
Is caused by constriction of spiral arteries
Reducing blood flow, oxygen, and nutrients
Weakened arterial walls rupture
Releasing blood into connective tissues of functional zone

47. 28-3 The Female Reproductive System
Menses
Degenerating tissues break away, enter uterine lumen
Entire functional zone is lost
Through external os and vagina
Only functional zone is affected
Deeper, basilar zone is supplied by straight arteries

48. The endometrium at menses
Figure 28-20a The Appearance of the Endometrium during the Uterine Cycle.
Perimetrium
Uterine
glands
Uterine cavity
Endometrium
Myometrium
Basilar zone
of endometrium
Cervix
MYOMETRIUM
Menses
LM ×63 a
The endometrium at menses

49. 28-3 The Female Reproductive System
The Proliferative Phase
Epithelial cells of uterine glands
Multiply and spread across endometrial surface
Restore integrity of uterine epithelium
Further growth and vascularization
Completely restores functional zone
Occurs at same time as:
Enlargement of primary and secondary follicles in ovary

50. 28-3 The Female Reproductive System
The Proliferative Phase
Is stimulated and sustained by:
Estrogens secreted by developing ovarian follicles
Entire functional zone is highly vascularized
Small arteries
Spiral toward inner surface
From larger arteries in myometrium

51. The endometrium during the proliferative phase
Figure 28-20b The Appearance of the Endometrium during the Uterine Cycle.
Uterine
glands
Uterine cavity
Uterine
cavity
Functional zone
Myometrium
ENDOMETRIUM
Basilar zone
MYOMETRIUM
Proliferative phase
LM ×66 b
The endometrium during the proliferative phase

52. 28-3 The Female Reproductive System
The Secretory Phase
Endometrial glands enlarge, increasing rate of secretion
Arteries of uterine wall
Elongate and spiral through functional zone
Begins at ovulation and persists as long as corpus luteum remains intact
Peaks about 12 days after ovulation
Glandular activity declines
Generally lasts 14 days
Ends as corpus luteum stops producing stimulatory hormones

53. The endometrium during the secretory phase of the uterine cycle
Figure 28-20c The Appearance of the Endometrium during the Uterine Cycle.
Uterine
glands
Uterine cavity
Detail of
uterine glands
LM ×150
Functional zone
Secretory phase
LM ×52 c
The endometrium during the
secretory phase of the uterine
cycle

54. Figure 28-24 Regulation of Female Reproduction (Part 3 of 6).
The ovarian and uterine cycles must operate in synchrony to ensure proper reproductive
function. If the two cycles are not properly coordinated, infertility results. A female who
doesn’t ovulate cannot conceive, even if her uterus is perfectly normal. A female who
ovulates normally, but whose uterus is not ready to support an embryo, will also be infertile.
HYPOTHALAMUS
As in males, GnRH from
the hypothalamus
regulates reproductive
function in females.
However, in females,
GnRH levels change
throughout the course
of the ovarian cycle. 1
Release of Gonadotropin-Releasing
Hormone (GnRH)
The cycle begins with the release of
GnRH, which stimulates the production
and secretion of FSH and the
production—but not the secretion—
of LH.
KEY
Stimulation
Release of GnRH
Inhibition
ANTERIOR
LOBE OF
PITUITARY
GLAND 2 3
Follicular Phase of
the Ovarian Cycle
Luteal Phase of
the Ovarian Cycle
Production
and secretion
of FSH
Production
of LH
The follicular phase begins
when FSH stimulates some
secondary follicles to develop
into a tertiary follicle.
The combination of increased GnRH
pulse frequency and elevated
estrogen levels stimulates LH secretion.
Secretion
of LH
On or around day 14, a massive surge
in LH level triggers (1) the completion
of meiosis I by the primary oocyte,
(2) the forceful rupture of the follicular
wall, (3) ovulation, roughly 9 hours
after the LH peak, and (4) formation
of the corpus luteum.
As secondary follicles develop,
FSH levels decline due to the
negative feedback effects of inhibin.
Negative
feedback

55. Figure 28-24 Regulation of Female Reproduction (Part 4 of 6).
Follicular Phase of
the Ovarian Cycle
Developing follicles also secrete
estrogens, especially estradiol,
the dominant hormone prior
to ovulation. 3
Luteal Phase of
the Ovarian Cycle
OVARY
After
day 10
The corpus luteum secretes
progesterone, which stimulates
and sustains endometrial development.
Before
day 10
• Meisois I
completion
• Ovulation
• Corpus luteum
formation
In low concentrations, estrogens
inhibit LH secretion. This
inhibition gradually decreases
as estrogen levels increase.
• Follicle
development
• Secretion of
inhibin
estrogens
After ovulation, progesterone
levels rise and estrogen levels fall.
This suppresses GnRH secretion.
If pregnancy does not occur, the
corpus luteum will degenerate
after 12 days, and as progesterone
levels decrease, GnRH secretion
increases, and a new cycle begins.
Secretion of
progesterone
Effects
on CNS
Stimulation
of bone and
muscle growth
Establishment and
maintenance of
female secondary
sex characteristics
Maintenance
of accessory
glands and
organs
Stimulation of
endometrial
growth and
secretion
KEY
Stimulation
Inhibition

56. Figure 28-24 Regulation of Female Reproduction (Part 5 of 6).
FOLLICULAR PHASE OF OVARIAN CYCLE
LUTEAL PHASE OF OVARIAN CYCLE 50 40 LH
Gonadotropic
hormone
levels
(IU/L) 30
GnRH pulse frequency (pulses/day) 20
FSH 10
Follicle stages
during the
ovarian cycle
Corpus
luteum
formation
Mature
corpus
luteum
Corpus
albicans
Follicle development
Ovulation
Progesterone
Ovarian
hormone
levels
Estrogens
Inhibin
28/0 7 14 21
28/0
Days

57. Figure 28-24 Regulation of Female Reproduction (Part 6 of 6).
FOLLICULAR PHASE OF OVARIAN CYCLE
LUTEAL PHASE OF OVARIAN CYCLE
Destruction of
functional zone
Repair and
regeneration of
functional zone
Secretion by
uterine glands
Endometrial
change
during thes
uterine cycle
Phases of the
uterine cycle
MENSES
PROLIFERATIVE
PHASE
SECRETORY PHASE
36.7
Basal body
temperature
(C)
36.4
28/0 7 14 21
28/0
Days

58. 28-3 The Female Reproductive System
Summary: Hormonal Regulation of the Female Reproductive Cycle
Early in follicular phase of ovarian cycle:
Estrogen levels are low
GnRH pulse frequency is 16–24/day (1 per 60–90 minutes)
As tertiary follicles form, concentration of circulating estrogens rises steeply
And GnRH pulse frequency increases to 36/day (1 per 30–60 minutes)

59. 28-3 The Female Reproductive System
Summary: Hormonal Regulation of the Female Reproductive Cycle
In follicular phase:
Switchover occurs
When estrogen levels exceed threshold value for about 36 hours
Resulting in massive release of LH from the anterior lobe of the pituitary gland

60. 28-3 The Female Reproductive System
Summary: Hormonal Regulation of the Female Reproductive Cycle
In follicular phase:
Sudden surge in LH concentration triggers:
Completion of meiosis I by primary oocyte
Rupture of follicular wall
Ovulation
Ovulation occurs 34–38 hours after LH surge begins (nine hours after LH peak)

61. 28-3 The Female Reproductive System
Summary: Hormonal Regulation of the Female Reproductive Cycle
In luteal phase of ovarian cycle:
High LH levels trigger ovulation
Promote progesterone secretion
Trigger formation of corpus luteum
Frequency of GnRH pulses stimulates LH more than FSH
LH maintains structure and secretory function of corpus luteum

62. 28-3 The Female Reproductive System
Summary: Hormonal Regulation of the Female Reproductive Cycle
Luteal phase
Progesterone levels remain high for one week
Unless pregnancy occurs, corpus luteum begins to degenerate
Progesterone and estrogen levels drop
GnRH pulse frequency increases
Stimulating FSH secretion
Ovarian cycle begins again

63. 28-3 The Female Reproductive System
Hormones and the Uterine Cycle
Corpus luteum degenerates
Progesterone and estrogen levels decline
Resulting in menses
Endometrial tissue sheds several days
Until rising estrogen stimulates regeneration of functional zone

64. 28-3 The Female Reproductive System
Hormones and the Uterine Cycle
Proliferative phase continues
Until rising progesterone starts secretory phase
Increase in estrogen and progesterone
Causes enlargement of endometrial glands
And increase in secretory activities

65. 28-3 The Female Reproductive System
Hormones and Body Temperature
Monthly hormonal fluctuations affect core body temperature
During luteal phase, progesterone dominates
During follicular phase, estrogen dominates and basal body temperature decreases about 0.3C
Upon ovulation, basal body temperature (BBT) declines noticeably
Day after ovulation, temperature rises