Download I. Testes

Male Reproductive Systems: For Discussion: True or False?
1. Sperm cells in the female reproductive tract are considered by a
woman’s immune system to be “non-self” and are attacked by her
phagocytic white blood cells. True
2. Sperm cells are considered by a man’s immune system as “non-self”
and are attacked by a man’s own white blood cells. True
3. A woman, in her reproductive lifetime, has the potential to produce
about 500,000 eggs, but she will only ever use about 500. True
4. The average man, in a single average ejaculation of semen, emits
more reproductive cells than the average woman produces in her
reproductive lifetime. True, about 420 million per average ejaculate,
he produces about 4 million/hour
5. Only one sperm may fertilize an egg in humans. True
6. Only about 1 in 42,000 sperm, or 0.00238 % of the sperm in an
average ejaculation reach the egg. True
The Male Reproductive System -produces and maintains sperm cells and
transports them, along with their
supporting fluids, into the female
reproductive tract
-produces and secretes male sex
hormones
Ureter
Large intestine
Urinary bladder
Seminal vesicle
Pubic bone
Penis
Ejaculatory duct
Ductus (vas)
deferens
Urethra
Prostate gland
Corpus cavernosum
Bulbourethral (Cowper’s)
gland
Anus
Corpus spongiusum
Glans penis
Epididymus
Prepuce (foreskin)
Testis
Scrotum
The Male Reproductive System
I. Testes -male primary sex organs
-produce sperm and male sex hormones
-housed within the scrotum
-form within the abdominal cavity, stimulated by
Ever hear of a
“gubanatorial
testosterone to descend into the scrotum 1-2 months
election”? It’s
before birth through the inguinal canal, led by the
from the Latin
for “steersman!”
gubernaculum, which anchors the testis to the bottom of
the scrotum
Rx – Inguinal hernia -in about one-fourth of males, the pouch of
peritoneum that moves through the inguinal canal
remains open; allowing for a loop of intestine to be
forced through the inguinal canal under great
vaginal
process
pressure, like getting dogpiled in a football game
-if the loop becomes constricted in the inguinal
canal, the blood supply can be cut off, creating a
strangulated hernia, in which the tissue will die
without prompt surgical treatment
I. Testes
Rx – Cryptorchidism -failure of one or both of the testes to descend into
the scrotum, which has an internal temperature of
about 34.4 °C (94 °F)
-internal body temperature 37 °C (98.6 °F) is too
high for sperm to survive
-sperm-producing cells degenerate, leading to
infertility
-leads to increased risk of testicular cancer
I. Testes -structure
A. Tunica albuginea -tough, white fibrous capsule surrounding
each testis and subdividing the inside of
each testis into about 250 lobules
B. Seminiferous tubules -each lobule contains 1-4 coiled
seminiferous tubules, each about
70 cm long (210 total meters), which
Ductus deferens
unite to form the rete testis, which in
Epididymus
turn form ducts that empty in the
epididymus, which continues into the
ductus deferens
Rete testis
-cells with the walls of the
seminiferous tubules called
spermatogonia divide by mitosis
when stimulated by testosterone
to produce primary spermatocytes,
Seminiferous
tubules
Tunica
which divide by meiosis to produce
albuginea
spermatozoa
Spermatogonia
Spermatozoa
I. Testes
B. Seminiferous tubules
Spermatozoa
Sustentacular
cells
Nucleus of
sustentacular cell
Spermatid
Secondary
spermatocyte
The sustenacular cells and
the tight junctions between
them form the blood-testis
barrier, which prevents
access to the sperm by the
white blood cells, which
would attack them as “nonself”
Primary
spermatocyte
Tight junction
New Type B
spermatogonium
New Type A
spermatogonium
Basement membrane
I. Testes
B. Seminiferous tubules
1. Spermatogenesis -creation of sperm within the walls of
the seminiferous tubules
-beginning at puberty, an increase in
testosterone triggers meiosis of the
primary spermatocyte
n
n
n
n
n=23
2n=46
Meiosis I
Reduction division
Meiosis II
Mitotic division
Maturation
n
n
n
n
n=23
Primary
spermatocyte
Secondary
spermatocytes
spermatids
spermatozoa
I. Testes
B. Seminiferous tubules
1. Spermatogenesis -from puberty to old age, a man can
produce about 100 million sperm per
day, average sperm count in semen
is 120 million sperm per mL, less than
20 million sperm per mL = infertility
During synapsis of
homologous chromosomes
during Prophase I, crossing
over occurs, resulting in new
genetic variation
I. Testes
B. Seminiferous tubules
1. Spermatogenesis
a. Sperm structure
i. Head -made up of the acrosome, which allow
the sperm to digest its way into the egg,
and a highly compacted nucleus, which
Acrosome
Head
contains 23 chromosomes in its diffuse
Nucleus
state chromatin
ii. Midpiece -contains mitochondria to provide
Midpiece
energy to lash the tail
iii. Tail -a single flagellum
Tail (flagellum)
I. Testes
Rx – Testicular Cancer -accounts for only about 1% of the cancers in men
in the U.S., causing about 390 deaths each year
-most common type of cancer in young men, ages
Seminiferous tubules
15-34, arises from epithelial tissue of tubules
-treated with the surgical removal (orchiectomy)
of the affected testicle and radiation and/or
chemotherapy to prevent reoccurence
-cured 95% of the time
-incidence is on the rise for all men, incidence is
the highest among white men, especially those of
Scandanavian descent
Interstitial cells
C. Interstitial Cells -cells of Leydig
-lie between seminiferous tubules in testes
-produce and secrete into the bloodstream
the male sex hormones
II. Epididymides -long (6 m) coiled tubules emerge from top and
descend down the back of the testes
-continuous with ducts inside testes, receive the
immature, non-motile sperm from seminiferous
tubules
-cells of epididymis secrete glycogen and other
substances that support sperm and promote their
maturation, rhythmic peristaltic contractions move
sperm down the length of the epididymis, violent
peristaltic contractions during emission of orgasm
propel sperm into ductus deferens
Epididymis
III. Ductus (Vas) Deferentia -muscular tubes 45 cm long leading
from the lower end of the epididymis
and through the inguinal canal to fuse
with the duct of the seminal vesicle to
form the ejaculatory duct
-sheathed together with the veins,
arteries, and nerves that supply the
Seminal
testes to form the spermatic cord,
vesicle
which testes are suspended from
Ductus
deferens
-violent peristaltic contractions during
emission propel sperm into ejaculatory
duct to mix with the secretions of the
Epididymis
seminal vesicles and prostate gland to
form semen, which fills the urethra
Ejaculatory
duct
IV. Seminal Vesicles -contract during emission to secrete a slightly
alkaline fluid to prevent semen from becoming
too acidic as it travels through the urethra
-seminal fluid also contains fructose to provide
energy for the sperm as they swim and
prostaglandlins, which stimulate muscle
contractions within the female reproductive
Seminal
tract, aiding in the movement of sperm towards
vesicle
the egg (can also help initiate labor)
Ductus
deferens
Epididymis
Ejaculatory
duct
V. Prostate Gland -contracts to secrete a thin, milky alkaline fluid
that forms the bulk of semen, neutralizing acidic
waste products produced by the sperm that
inhibits their motility
-alkalinity enhances motility of sperm and
neutralizes the much more acidic contents of the
vagina to protects sperm
Seminal
vesicle
Ductus
deferens
Epididymis
Prostate
gland
Ejaculatory
duct
V. Prostate Gland
Rx – Benign Prostatic Hypertrophy -enlargement of the prostate gland in
50% of all men over age 50, and 90%
of all men over age 70
-pressure on bladder leads to increased
frequency of urination and urine
retention, which can lead to infection,
bladder stones and kidney disease
-can also indicate prostate cancer
Rx – Prostate Cancer -most common cancer in men after skin cancer,
235,000 new cases per year, 70% in men over age
65, causing 27,000 cancer deaths per year
-more common in African American men than in
Caucasian men, genetic tendency perhaps linked to
a diet high in saturated fat
-treated by surgical removal of entire prostate and
sometimes surrounding lymph nodes, and radiation
VI. Bulbourethral (Cowper’s) Gland -secretes a small amount of
mucus-like fluid in response to
sexual stimulation, which
cleanses the urethra of urine
residues prior to ejaculation
and provides lubrication for
sexual intercourse
Seminal
vesicle
Ductus
deferens
Epididymis
Prostate
gland
Ejaculatory
duct
Bulbourethral
glands
VII. Scrotum -houses testes
-protects and regulates temperature at 34.4 ºC (94 ºF)
-dartos muscle contracts to elevate testes as part of the
sexual response to shorten distance sperm have to
travel during emission, contracts to elevate testes to
protect them from cold and to protect them from
physical damage in response to activation of ‘fight-orflight’ mechanism
-padded with fat to protect testes
VIII. Penis -male copulatory organ
-houses urethra, which conveys urine and semen to the
outside of the body
-contains erectile tissues, which enable the penis to
become engorged with blood so that it becomes erect
and can penetrate vagina
VIII. Penis
A. Erectile tissues -Corpus cavernosa and Corpus spongiosum
-fill with blood in response to sexual
stimulation, as parasympathetic nerve
impulses cause arteries leading into erectile
tissues to dilate, increasing blood flow and
at the same time pressing veins leading out
of erectile tissues flat, accumulation of blood
leads to erection
Penis
Corpus
cavernosa
Corpus
spongiosum
VIII. Penis
B. Glans penis -cone-shaped distal end of penis
-houses external urethral orifice
-covered by the sheath-like prepuce, which is
often removed at birth by the surgical procedure
of circumcision
-thin-skinned, with many sensory receptors for
sexual stimulation
Penis
Corpus
cavernosa
Prepuce
Glans
penis
External urethral orifice
Corpus
spongiosum
VIII. Penis -during orgasm, the process of emission mixes sperm
with the secretions of the seminal vesicles, prostate
gland, and bulbourethral gland, filling the urethra with
2-5 mL of semen containing 240-600 million sperm
-during ejaculation, skeletal muscles at the base of the
erectile columns of the penis contract, increasing the
pressure in the erectile tissues, and forcing semen from
the urethra at a speed of 29 kph (18 mph), depositing
semen far up into vagina near cervix
Rx – Erectile Dysfunction -impotence, the inability of the penis to become
erect or sustain an erection
-usually a complicating factor of diabetes,
paralysis, prostate surgery, or drug use
-most often treated with therapy by drugs like
Viagra®, which blocks the enzymatic breakdown of the neurotransmitter cGMP, which
relaxes the arteries leading into the erectile
tissues, allowing them to dilate