Recall:
Female Reproductive System
Male Reproductive System:
1)
1)
Produce testosterone for
sexual characteristics
2)
Produce large numbers of
sperm & store them until
ejaculation
3)
Produce fluids to add to semen
4)
Sexual intercourse; ejaculate
semen high into vagina
2)
3)
4)
5)
6)
Produce estrogen and
progesterone for sexual
characteristics
Produce and release one large
oocyte at regular intervals
Sexual intercourse, receive
semen
Produce hormones to prepare
endometrium for pregnancy each
cycle; shed functional layer by
menstruation
Protect/nourish embryo/fetus;
expel it during childbirth
Produce milk to nourish newborn
Organs of the male reproductive system”
Midsagittal view
Posterior view
Testis:
Approximately 4cm x 2 cm x 2 cm
Outside body cavity in scrotum
Divided into + 200
compartments;
Each compartment
contains a long, coiled
seminiferous tubule
Seminiferous tubules are
site of spermatogenesis
Hundreds of millions of sperm produced per day
Entire process takes about sixty days
Spermatogenesis is
initiated and stimulated by
follicle stimulating hormone
(FSH) secreted by the
pituitary gland.
Testosterone, produced
within the testicle, must also
be present
FSH is the same hormone that stimulates oogenesis in the ovary.
However, secretion of FSH in women rises and falls each cycle,
resulting in the production of just one oocyte;
Secretion of FSH and testosterone in men remains relatively
steady so spermatogenesis is continuously stimulated and sperm
are continuously produced.
The pituitary gland also
secretes luteinizing
hormone (LH) in male.
LH stimulates formation of the
corpus luteum and production of
progesterone in the ovary.
In the testicle, LH stimulates the
production of testosterone by
interstitial cells, which are
located between the
seminiferous tubules
Unlike oogenesis, in which the developing oocyte is surrounded
and protected by a follicle, sperm are not produced within follicles
However: developing
sperm are protected and
supported by a special
cell called a sustentacular
or Sertoli cell.
Sperm leaving the testis next enter a long (>6 meters) coiled tube
called the epididymis.
Also located in scrotum, behind the
testis
Sperm take about 40 days to pass
through the epididymis, maturing and
becoming fertile.
They are stored here until ejaculation.
From the epididymis, sperm are transported through the vas
deferens or ductus deferens which passes upward into the
abdominal cavity. This is happening constantly, but occurs much
more rapidly during ejaculation.
As it passes from the scrotum to the abdominal cavity, the vas
deferens is accompanied by the artery, veins, and nerves supplying
the testis.
All of these are surrounded by a thick covering of connective tissue,
and the entire structure is called the spermatic cord
The spermatic cord passes through a tunnel called
the inguinal canal
Within the abdomen, the vas deferens on each side curves
backward, then downward and forward, along the side of the
bladder.
The end of the vas
deferens, called its
ampulla, is enlarged.
Male Accessory Glands:
Seminal Vesicles: Paired, posterior to
bladder. Ducts join vas deferens to
form ejaculatory duct.
Produce + 60% of
semen volume.
Contains nutrients for
sperm.
Contains chemicals to
decrease viscosity of
cervical mucous, and
to stimulate peristalsis
of cervix
Male Accessory Glands:
Prostate: Inferior to bladder, ejaculatory ducts embedded within it.
Surrounds proximal part of urethra as it leaves the bladder
Produces + 30% of semen volume.
Contains chemicals to:
- Neutralize acidity of vagina;
- Increase sperm motility;
- Cause semen to clot, then liquify.
Penis:
Root: Embedded in perineum; + 50% of total length
Body or shaft: Outside, covered with skin
Glans: Tip, not covered with skin
Penis:
Three erectile bodies:
- Two corpora cavernosa
- One corpus spongiosum
Fill with blood during erection,
causing shaft to line up with
root of penis
When blood leaves erectile
bodies, shaft of penis droops
down into normal position
Ejaculation:
Physical stimulation of penis sends autonomic nerve signals to
lower (lumbar) spinal cord.
Reflexive nerve signals cause:
Contraction of smooth muscle of vas
deferens to move sperm into ejaculatory
ducts and urethra
Contraction of seminal vesicles & prostate
move their secretions into urethra
Then ….
Ejaculation:
Physical stimulation of penis sends autonomic nerve signals to
lower (lumbar) spinal cord.
Reflexive nerve signals cause:
Contraction of smooth muscle of vas
deferens to move sperm into ejaculatory
ducts and urethra
Contraction of seminal vesicles & prostate
move their secretions into urethra
Reflexive nerve signals cause:
Contraction of skeletal muscles
along root of penis to force semen
along urethra and out external
urethral orifice
During ejaculation:
a) Sperm from the epididymis and vas deferens
b) Fluid from the seminal vesicles
c) Fluid from the prostate
All enter the urethra as it passes through the prostate
The urethra then passes
through the penis to its tip.
Semen:
Mixture of sperm, seminal vesicle fluid, prostate fluid
Normal ejaculate:
4 – 6 milliliters
50-100 million sperm per milliliter
Alkaline to neutralize acidity of vagina
Contains nutrients for sperm, chemicals to decrease viscosity of
cervical mucous and to stimulate peristalsis of cervix
Semen clots immediately after ejaculation to hold it in vagina,
then liquifies gradually over 5 to 10 minutes to release sperm
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