1. The Reproductive System: Part A27
The Reproductive System: Part A

2. Primary sex organs (gonads): testes and ovaries
Reproductive System
Primary sex organs (gonads): testes and ovaries
Produce sex cells (gametes)
Secrete steroid sex hormones
Androgens (males)
Estrogens and progesterone (females)
Accessory reproductive organs: ducts, glands, and external genitalia

3. Sex hormones play roles in
Reproductive System
Sex hormones play roles in
Development and function of the reproductive organs
Sexual behavior and drives
Growth and development of many other organs and tissues

4. Male Reproductive System
Testes (within the scrotum) produce sperm
Sperm are delivered to the exterior through a system of ducts
Epididymis, ductus deferens, ejaculatory duct, and the urethra

5. Male Reproductive System
Accessory sex glands: seminal vesicles, prostate, and bulbourethral glands
Empty secretions into the ducts during ejaculation

6. Ureter Urinary bladder Prostatic urethra Peritoneum Seminal vesicle
Membranous
urethra
Ampulla of
ductus
deferens
Urogenital
diaphragm
Pubis
Ejaculatory
duct
Corpus
cavernosum
Rectum
Corpus
spongiosum
Prostate
Bulbourethral
gland
Spongy urethra
Epididymis
Anus
Glans penis
Bulb of penis
Prepuce
Ductus (vas)
deferens
Testis
External
urethral orifice
Scrotum
Figure 27.1

7. Sac of skin and superficial fascia
The Scrotum
Sac of skin and superficial fascia
Hangs outside the abdominopelvic cavity
Contains paired testes
3C lower than core body temperature (temperature necessary for sperm production)

8. Temperature is kept constant by two sets of muscles
The Scrotum
Temperature is kept constant by two sets of muscles
Smooth muscle that wrinkles scrotal skin (dartos muscle)
Bands of skeletal muscle that elevate the testes (cremaster muscles)

9. Urinary bladder Superficial inguinal ring (end of inguinal canal)
Testicular artery
Spermatic cord
Ductus (vas)
deferens
Penis
Autonomic
nerve fibers
Middle septum
of scrotum
Pampiniform
venous plexus
Cremaster muscle
External spermatic
fascia
Epididymis
Tunica vaginalis
(from peritoneum)
Superficial fascia
containing dartos
muscle
Tunica albuginea
of testis
Scrotum
Internal spermatic
fascia
Skin
Figure 27.2

10. Each is surrounded by two tunics
The Testes
Each is surrounded by two tunics
Tunica vaginalis, derived from peritoneum
Tunica albuginea, the fibrous capsule
Septa divide the testis into 250–300 lobules, each containing 1–4 seminiferous tubules (site of sperm production)

11. Sperm are conveyed through
The Testes
Sperm are conveyed through
Seminiferous tubules
Tubulus rectus
Rete testis
Efferent ductules
Epididymis

12. The Testes
Blood supply comes from the testicular arteries and testicular veins
Spermatic cord encloses nerve fibers, blood vessels, and lymphatics that supply the testes

13. Spermatic cord Blood vessels and nerves Ductus (vas) deferens
Head of epididymis
Testis
Efferent ductule
Seminiferous
tubule
Rete testis
Lobule
Straight tubule
Septum
Tunica albuginea
Body of epididymis
Tunica vaginalis
Duct of epididymis
Cavity of
tunica vaginalis
Tail of epididymis
(a)
Figure 27.3a

14. The Testes
Interstitial (Leydig) cells outside the seminiferous tubules produce androgens

15. Seminiferous tubule (c) Interstitial cells Spermatogenic
cells in tubule
epithelium
Areolar
connective
tissue
Myoid
cells
Sperm
Figure 27.3c

16. The Penis
External genitalia are the scrotum and the penis
Penis is the male copulatory organ

17. The Penis Penis consists of
Root and shaft that ends in the glans penis
Prepuce, or foreskin—the cuff of loose skin covering the glans
Circumcision is the surgical removal of the foreskin
Crura
The proximal end surrounded by ischiocavernosus muscle; anchors penis to the pubic arch

18. The Penis
Spongy urethra and three cylindrical bodies of erectile tissue (spongy network of connective tissue and smooth muscle with vascular spaces)
Corpus spongiosum surrounds the urethra and expands to form the glans and bulb
Corpora cavernosa are paired dorsal erectile bodies
Erection: erectile tissue fills with blood, causing the penis to enlarge and become rigid

19. Figure 27.4 Ureter Ampulla of ductus deferens Seminal vesicle
Urinary bladder
Ejaculatory duct
Prostate
Prostatic urethra
Orifices of prostatic ducts
Bulbourethral gland and duct
Membranous urethra
Urogenital diaphragm
Bulb of penis
Root of penis
Crus of penis
Bulbourethral duct opening
Ductus deferens
Corpora cavernosa
Epididymis
Corpus spongiosum
Shaft (body) of penis
Testis
Section of (b)
Spongy urethra
Glans penis
Prepuce (foreskin)
(a)
External urethral orifice
Dorsal vessels
and nerves
Corpora cavernosa
Urethra
Skin
Tunica albuginea of erectile bodies
Deep arteries
(b)
Corpus spongiosum
Figure 27.4

20. The Male Duct System
Epididymis
Ductus deferens
Ejaculatory duct
Urethra

21. Head: contains the efferent ductules Duct of the epididymis
Microvilli (stereocilia) absorb testicular fluid and pass nutrients to stored sperm
Nonmotile sperm enter, pass slowly through, and become motile
During ejaculation the epididymis contracts, expelling sperm into the ductus deferens

22. Ductus Deferens and Ejaculatory Duct
Passes through the inguinal canal
Expands to form the ampulla and then joins the duct of the seminal vesicle to form the ejaculatory duct
Propels sperm from the epididymis to the urethra
Vasectomy: cutting and ligating the ductus deferens, which is a nearly 100% effective form of birth control

23. Conveys both urine and semen (at different times)
Urethra
Conveys both urine and semen (at different times)
Has three regions
Prostatic urethra
Membranous urethra
Spongy (penile) urethra

24. Figure 27.4 Ureter Ampulla of ductus deferens Seminal vesicle
Urinary bladder
Ejaculatory duct
Prostate
Prostatic urethra
Orifices of prostatic ducts
Bulbourethral gland and duct
Membranous urethra
Urogenital diaphragm
Bulb of penis
Root of penis
Crus of penis
Bulbourethral duct opening
Ductus deferens
Corpora cavernosa
Epididymis
Corpus spongiosum
Shaft (body) of penis
Testis
Section of (b)
Spongy urethra
Glans penis
Prepuce (foreskin)
(a)
External urethral orifice
Dorsal vessels
and nerves
Corpora cavernosa
Urethra
Skin
Tunica albuginea of erectile bodies
Deep arteries
(b)
Corpus spongiosum
Figure 27.4

25. Accessory Glands: Seminal Vesicles
Produces viscous alkaline seminal fluid
Fructose, ascorbic acid, coagulating enzyme (vesiculase), and prostaglandins
70% of the volume of semen
Duct of seminal vesicle joins the ductus deferens to form the ejaculatory duct

26. Accessory Glands: Prostate
Encircles part of the urethra inferior to the bladder
Secretes milky, slightly acid fluid:
Contains citrate, enzymes, and prostate-specific antigen (PSA)
Plays a role in the activation of sperm
Enters the prostatic urethra during ejaculation

27. Accessory Glands: Bulbourethral Glands (Cowper’s Glands)
Pea-sized glands inferior to the prostate
Prior to ejaculation, produce thick, clear mucus
Lubricates the glans penis
Neutralizes traces of acidic urine in the urethra

28. Figure 27.4 Ureter Ampulla of ductus deferens Seminal vesicle
Urinary bladder
Ejaculatory duct
Prostate
Prostatic urethra
Orifices of prostatic ducts
Bulbourethral gland and duct
Membranous urethra
Urogenital diaphragm
Bulb of penis
Root of penis
Crus of penis
Bulbourethral duct opening
Ductus deferens
Corpora cavernosa
Epididymis
Corpus spongiosum
Shaft (body) of penis
Testis
Section of (b)
Spongy urethra
Glans penis
Prepuce (foreskin)
(a)
External urethral orifice
Dorsal vessels
and nerves
Corpora cavernosa
Urethra
Skin
Tunica albuginea of erectile bodies
Deep arteries
(b)
Corpus spongiosum
Figure 27.4

29. Mixture of sperm and accessory gland secretions
Semen
Mixture of sperm and accessory gland secretions
Contains nutrients (fructose), protects and activates sperm, and facilitates their movement (e.g., relaxin)
Prostaglandins in semen
Decrease the viscosity of mucus in the cervix
Stimulate reverse peristalsis in the uterus

30. Semen
Alkalinity neutralizes the acid in the male urethra and female vagina
Antibiotic chemicals destroy certain bacteria
Clotting factors coagulate semen just after ejaculation, then fibrinolysin liquefies it
Only 2–5 ml of semen are ejaculated, containing 20–150 million sperm/ml

31. Male Sexual Response Erection
Enlargement and stiffening of the penis from engorgement of erectile tissue with blood
Initiated by sexual stimuli, including:
Touch and mechanical stimulation of the penis
Erotic sights, sounds, and smells
Can be induced or inhibited by emotions or higher mental activity

32. Male Sexual Response Erection:
Parasympathetic reflex promotes release of nitric oxide (NO)
NO causes erectile tissue to fill with blood
Expansion of the corpora cavernosa
Compresses drainage veins and maintains engorgement
Corpus spongiosum keeps the urethra open
Impotence: the inability to attain erection

33. Male Sexual Response Ejaculation
Propulsion of semen from the male duct system
Sympathetic spinal reflex causes
Ducts and accessory glands to contract and empty their contents
Bladder sphincter muscle to constrict, preventing the expulsion of urine
Bulbospongiosus muscles to undergo a rapid series of contractions

34. Most body cells are diploid (2n) and contain
Spermatogenesis
Sequence of events that produces sperm in the seminiferous tubules of the testes
Most body cells are diploid (2n) and contain
Two sets of chromosomes (one maternal, one paternal)
23 pairs of homologous chromosomes
Gametes are haploid (n) and contain
23 chromosomes

35. Gamete formation involves meiosis
Nuclear division in the gonads in which the number of chromosomes is halved (from 2n to n)
Two consecutive cell divisions (meiosis I and II) following one round of DNA replication
Produces four daughter cells
Introduces genetic variation

36. Meiosis Animation: Interphase Animation: Prophase I
PLAY
Animation: Interphase
PLAY
Animation: Prophase I
PLAY
Animation: Metaphase I
PLAY
Animation: Anaphase I
PLAY
Animation: Telephase I
PLAY
Animation: Meiosis II

37. Figure 27.6 (1 of 2) Interphase cell MEIOSIS I Prophase I
Prophase events occur, as in mitosis. Additionally,
synapsis occurs: Homologous chromosomes come
together along their length to form tetrads. During
synapsis, the “arms” of homologous chromatids wrap
around each other, forming several crossovers. The
nonsister chromatids trade segments at points of
crossover. Crossover is followed through the diagrams
below.
Nuclear
envelope
Centromere
Crossover
Centriole
pairs
Spindle
Sister
chromatids
Nuclear envelope
fragments late
in prophase I
Chromatin
2n = 4
Interphase events
As in mitosis, meiosis is preceded
by DNA replication and other
preparations for cell division.
Metaphase I
The tetrads align randomly on the spindle
equator in preparation for anaphase.
Tetrad
Dyad
Anaphase I
Unlike anaphase of mitosis, the centromeres do not
separate during anaphase I of meiosis, so the sister
chromatids (dyads) remain firmly attached. However, the
homologous chromosomes do separate from each other
and the dyads move toward opposite poles of the cell.
Chromosomes
uncoil
Telophase I
The nuclear membranes re-form around the
chromosomal masses, the spindle breaks down, and
the chromatin reappears as telophase and cytokinesis
are completed. The 2 daughter cells (now haploid)
enter a second interphase-like period, called
interkinesis, before meiosis II occurs. There is no
second replication of DNA before meiosis II.
Nuclear
envelopes
re-form
Cleavage
furrow
Figure 27.6 (1 of 2)

38. MEIOSIS II
Prophase II
Meiosis II begins with the
products of meiosis I (2
haploid daughter cells) and
undergoes a mitosis-like
nuclear division process
referred to as the equational
division of meiosis.
Metaphase II
Anaphase II
After progressing through the
phases of meiosis and
cytokinesis, the product is 4
haploid cells, each genetically
different from the original
mother cell. (During human
spermatogenesis, the daughter
cells remain interconnected by
cytoplasmic extensions during
the meiotic phases.)
Telophase II
and cytokinesis
Products of
meiosis:
haploid
daughter cells
Figure 27.6 (2 of 2)

39. Figure 27.5 (1 of 2) Mother cell (before chromosome replication)
MITOSIS
MEIOSIS
Replicated
chromosome
Tetrad formed by
synapsis of replicated
homologous
chromosomes
Prophase
Prophase I
Chromosomes
align at the
metaphase plate
Tetrads align at the
metaphase plate
Metaphase
Metaphase I
Sister chromatids
separate during
anaphase
Homologous chromosomes
separate but sister
chromatids remain together
during anaphase I
Daughter
cells of
mitosis
Daughter cells
of meiosis I 2n 2n
No further chromosomal
replication; sister chromatids
separate during
anaphase II
Meiosis II n n n n
Daughter cells of meiosis II
(usually gametes)
Figure 27.5 (1 of 2)

40. Figure 27.5 (2 of 2) MITOSIS MEIOSIS Number of divisions
One, consisting of prophase, metaphase,
anaphase, and telophase.
Two, each consisting of prophase, metaphase,
anaphase, and telophase. DNA replication does
not occur between the two nuclear divisions.
Synapsis of
homologous
chromosomes
Does not occur.
Occurs during mitosis I; tetrads formed,
allowing crossovers.
Daughter cell
number and
genetic
composition
Two. Each diploid (2n) cell is identical to
the mother cell.
Four. Each haploid (n) cell contains half as many
chromosomes as the mother cell and is
genetically different from the mother cell.
Roles in the body
For development of multicellular adult
from zygote. Produces cells for growth
and tissue repair. Ensures constancy of
genetic makeup of all body cells.
Produces cells for reproduction (gametes).
Introduces genetic variability in the gametes and
reduces chromosomal number by half so that when
fertilization occurs, the normal diploid chromosomal
number is restored (in humans, 2n = 46).
Figure 27.5 (2 of 2)

41. Spermatic cells give rise to sperm
Spermatogenesis
Spermatic cells give rise to sperm
Mitosis
Spermatogonia form spermatocytes
Meiosis
Spermatocytes form spermatids
Spermiogenesis
Spermatids become sperm

42. Figure 27.7a

43. Spermatogonium
(stem cell)
Cytoplasm of adjacent
sustentacular cells
Sustentacular
cell nucleus
Basal lamina
Type A daughter cell
remains at basal lamina
as a stem cell
Type B daughter cell
Tight junction between
sustentacular cells
Primary
spermatocyte
Secondary
spermatocytes
Early
spermatids
Late spermatids
Cytoplasmic
bridge
Spermatozoa
Lumen of
seminifer-
ous tubule
(c) A portion of the seminiferous tublule wall, showing the spermato-
genic cells surrounded by sustentacular cells (colored gold)
Figure 27.7c

44. Mitosis of Spermatogonia
Begins at puberty
Spermatogonia
Stem cells in contact with the epithelial basal lamina
Each mitotic division  a type A daughter cell and a type B daughter cell

45. Mitosis of Spermatogonia
Type A cells maintain the germ cell line at the basal lamina
Type B cells move toward the lumen and develop into primary spermatocytes

46. Meiosis: Spermatocytes to Spermatids
Meiosis I
Primary spermatocyte (2n)  two secondary spermatocytes (n)
Meiosis II
Each secondary spermatocyte (n)  two spermatids (n)
Spermatid: small nonmotile cells close to the lumen of the tubule

47. Basal lamina
Spermatogonium
(stem cell)
Type A daughter cell
remains at basal lamina
as a stem cell
Mitosis
Type B daughter cell
Growth
Enters meiosis I
and moves to
adluminal
compartment
Primary
spermatocyte
Meiosis I
completed
Secondary
spermatocytes
Meiosis II
Early
spermatids
Late spermatids
Spermatozoa
(b) Events of spermatogenesis,
showing the relative position
of various spermatogenic cells
Figure 27.7b

48. Spermiogenesis: Spermatids to Sperm
Spermatids lose excess cytoplasm and form a tail, becoming spermatozoa (sperm)

49. Sperm
Major regions
Head: genetic region; nucleus and helmetlike acrosome containing hydrolytic enzymes that enable the sperm to penetrate an egg
Midpiece: metabolic region; mitochondria
Tail: locomotor region; flagellum

50. Golgi apparatus Acrosomal vesicle
Approximately 24 days
Golgi
apparatus
Acrosomal
vesicle
Mitochondria
Acrosome
Nucleus 1 2
Centrioles
Spermatid
nucleus
Microtubules
Midpiece
Head
(a) 3
Flagellum
Excess
cytoplasm 4
Tail 5 6 7
(b)
Figure 27.8a, b

51. Role of Sustentacular Cells
Large supporting cells (Sertoli cells)
Extend through the wall of the tubule and surround developing cells
Provide nutrients and signals to dividing cells
Dispose of excess cytoplasm sloughed off during spermiogenesis
Secrete testicular fluid into lumen for transport of sperm

52. Role of Sustentacular Cells
Tight junctions divide the wall into two compartments
Basal compartment—spermatogonia and primary spermatocytes
Adluminal compartment—meiotically active cells and the tubule lumen

53. Spermatogonium
(stem cell)
Cytoplasm of adjacent
sustentacular cells
Sustentacular
cell nucleus
Basal lamina
Type A daughter cell
remains at basal lamina
as a stem cell
Type B daughter cell
Tight junction between
sustentacular cells
Primary
spermatocyte
Secondary
spermatocytes
Early
spermatids
Late spermatids
Cytoplasmic
bridge
Spermatozoa
Lumen of
seminifer-
ous tubule
(c) A portion of the seminiferous tublule wall, showing the spermato-
genic cells surrounded by sustentacular cells (colored gold)
Figure 27.7c

54. Role of Sustentacular Cells
Tight junctions form a blood-testis barrier
Prevents sperm antigens from escaping into the blood where they would activate the immune system
Because sperm are not formed until puberty, they are absent during immune system development, and would not be recognized as “self”