Download The Reproductive Systems

The Reproductive Systems
The male and female reproductive systems
-produce gametes, that is, sperm and egg
cells, and
-ensure the union of gametes in fertilization
- in women, the uterus provides the site for
the developing embryo/fetus until it is sufficiently
developed to survive outside the womb
MEIOSIS
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The cell division process of meiosis
produces the gametes—sperm or egg
cells.
In meiosis, one cell with the diploid
number of chromosomes (46 for humans)
divides twice to form four cells, each with
the haploid number of chromosomes.
Haploid means half the usual diploid
number, so for humans the haploid
number is 23.
SPERMATOGENESIS
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Spermatogenesis is the process of
meiosis as it takes place in the testes,.
Within each testis are seminiferous
tubules that contain spermatogonia,
which are stem cells that generate sperm.
A spermatogonium divides by mitosis to
form two cells, one of which will remain in
place as a stem cell, while the other
differentiates (specializes) to become a
primary permatocyte that will undergo
meiosis .
Role of Hormones
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Follicle-stimulating hormone (FSH) from
the anterior pituitary gland initiates sperm
production.
Testosterone,secreted by the testes when
stimulated by luteinizing hormone (LH)
from the anterior pituitary, promotes the
maturation of sperm.
* Inhibin, also produced by the testes,
decreases the secretion of FSH.
For each primary spermatocyte, four
Sperm &Ova production
Sperm production begins at puberty (10
to 14years of age), and millions of sperm
are formed each day in the testes.
*Although sperm production diminishes
with advancing age, there is usually no
complete cessation, as there is of egg
production in women at menopause
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OOGENESIS
Oogenesis is the process of meiosis for
egg cell formation;
 it is regulated by hormones:
- FSH initiates the growth of ovarian
follicles, each of which contains an
oogonium, a stem cell for egg cell
production .
This hormone also stimulates the follicle
cells to secrete estrogen, which promotes
the maturation of the ovum.
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Notice
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for each primary oocyte that undergoes
meiosis, only one functional egg cell is
produced. The other three cells produced
are called polar bodies. They have no
function,
and will simply deteriorate.
A mature ovarian follicle actually contains
the secondary oocyte.
The second meiotic division will take place
if and when the egg is fertilized
Oogenesis
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The production of ova begins at puberty (10 to
14years of age) and continues until
menopause (45 to 55years of age), when the
ovaries atrophy and no longer respond to
pituitary hormones.
During this 30- to 40-year span, egg production
is cyclical, with a mature ovum being produced
approximately every 28 days
Actually, several follicles usually begin to develop
during each cycle.
However, the rupturing (ovulation) of the first
follicle to mature stops the growth of the others
Fertilization
It is union of nuclei of sprm &ovum
 The haploid egg and sperm cells produced by
 meiosis each have 23 chromosomes.
 When fertilizaTion occurs, the nuclei of the egg
and sperm merge,and the fertilized egg
(zygote) has 46 chromosomes, the diploid
number.
 Thus, meiosis maintains the diploid number of
the human species by reducing the number of
chromosomes by half in the formation of
gametes
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MALE REPRODUCTIVE SYSTEM
The male reproductive system consists of
 1- two testes
 2- series of ducts : epididymis, ductus
deferens, ejaculatory duct, and urethra .
 3- the reproductive glands:
seminal vesicles, prostate gland, and
bulbourethral glands.
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TESTES
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The testes are located in the scrotum, a sac of
skin between the upper thighs.
The temperature within the scrotum is about
34c, slightly lower than body temperature, which
is necessary for the production of viable sperm.
In the male fetus, the testes develop near the
kidneys, then descend into the scrotum just
before birth. Cryptorchidism is the condition in
which the testes fail to descend, and the result
is sterility unless the testes are surgically placed
in the scrotum.
Testis
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Each testis is about 1.5 inches long by 1 inch
wide (4 cm by 2.5 cm) and is divided internally
into lobes
Each lobe contains several seminiferous
tubules, in which spermatogenesis takes place.
Among the spermatogonia of the seminiferous
tubules are sustentacular (Sertoli) cells,
which produce the hormone inhibin when
stimulated by testosterone.
Testis
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Between the loops of the seminiferous
tubules are interstitial cells, which
produce testosterone when stimulated
by luteinizing hormone (LH) from the
anterior pituitary gland.
Besides its role in the maturation of
sperm, testosterone is also responsible for
the male secondary sex characteristics,
which begin to develop at puberty .
sperm cell
A sperm cell consists of several parts:
- The head contains the 23 chromosomes.
-On the tip of the head is the acrosome, which
is similar to a lysosome and contains enzymes to
digest the membrane of an egg cell.
- Within the middle piece are mitochondria that
produce ATP.
-The flagellum provides motility. It is the
beating of the flagellum that requires energy
from ATP.
 Sperm from the seminiferous tubules enter a
tubular network called the rete testis, then enter
the epididymis, the first of the reproductive
ducts.
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EPIDIDYMIS
The epididymis (plural: epididymides) is
a tube about 20 feet (6 m) long that is
coiled on the posterior surfaceof each
testis.
 within the epididymis the sperm complete
their maturation, and their flagella become
functional.
 Smooth muscle in the wall of the
epididymis propels the sperm into the
ductus deferens.
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DUCTUS DEFERENS
Also called the vas deferens,
 It extends from the epididymis in the scrotum on its own
 side into the abdominal cavity through the inguinal
canal.
 This canal is an opening in the abdominal wall
for the spermatic cord, a connective tissue sheath
that contains the ductus deferens, testicular blood
vessels, and nerves.
 Because the inguinal canal is an opening in a muscular
wall, it is a natural “weak spot,” and it is the most
common site of hernia formation in men
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Once inside the abdominal cavity, the
ductus deferens extends upward over the
urinary bladder, then down the posterior
side to join the ejaculatory duct on its own
side .
 The smooth muscle layer of the ductus
deferens contracts in waves of peristalsis
as part of ejaculation
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EJACULATORY DUCTS
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Each of the two ejaculatory ducts
receives sperm from the ductus deferens
and the secretion of the seminal vesicle on
its own side.
Both ejaculatory ducts empty into the
single urethra
SEMINAL VESICLES
The paired seminal vesicles are
posterior to the urinary bladder .
 Their secretion contains fructose to
provide an energy source for sperm and is
alkaline to enhance sperm motility.
*The duct of each seminal vesicle joins
the ductus deferens on that side to form
the ejaculatory duct.
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PROSTATE GLAND
A muscular gland just below the urinary bladder,
it is 3 cm by 4 cm by 2 cm, about the size of a
walnut).
 It surrounds the first inch of the urethra as it
emerges from the bladder .
 The glandular tissue of the prostate secretes an
alkaline fluid that helps maintain sperm motility.
*The smooth muscle of the prostate gland
contracts during ejaculation to contribute to
the expulsion of semen from the urethra
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BULBOURETHRAL GLANDS
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Also called Cowper’s glands, about the size of
peas and are located below the prostate gland;
they empty into the urethra.
Their alkaline secretion coats the interior of the
urethra just before ejaculation,which neutralizes
any acidic urine that might be present.
the secretions of the male reproductive glands
are alkaline. This is important because the cavity
of the female vagina has an acidic pH created by
the normal flora .
URETHRA
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The urethra is the last of the ducts
through which semen travels,
- and its longest portion.
Circumcision is the surgical removal of
the foreskin
This is a common procedure performed on
male infants,
SEMEN
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Semen consists of sperm and the
secretions of the seminal vesicles, prostate
gland, and bulbourethral glands;
its average pH is about 7.4. During
ejaculation.
approximately 2 to 4 mL of semen is
expelled.
Each milliliter of semen contains about
100 million sperm cells
CONTRACEPTION
There are several methods of contraception, or
birth control; some are more effective than
others.
 Sterilization—Sterilization in men involves a
relatively simple procedure called a vasectomy.
 The ductus (vas) deferens is accessible in the
scrotum, in which a small incision is made on
either side. The ductus is then sutured and cut.
* Although sperm are still produced in the testes,
they cannot pass the break in the ductus, and
they simply die and are reabsorbed.
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Sterilization in women
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Sterilization in women is usually
accomplished by tubal ligation, the
suturing and severing of the fallopian
tubes by way of a small incision in the
abdominal wall.
Ova cannot pass the break in the tube,
nor can sperm pass from the uterine side
to fertilize an ovum.
When done properly, these forms of
surgical sterilization are virtually 100%
effective.
Oral contraceptives
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Birth control pills contain progesterone
and estrogen in varying proportions. They
prevent ovulation by inhibiting the
ecretion of FSH and LH from the anterior
pituitary gland.
When taken according to schedule, birth
control pills are about 98% effective
PROSTATIC HYPERTROPHY
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Prostatic hypertrophy is enlargement of the
prostate gland.
Benign prostatic hypertrophy is a common
occurrence in men over the age of 60 years.
The enlarged prostate compresses the urethra
within it and may make urination difficult or
result in urinary retention.
A prostatectomy is the surgical removal of part
or all of the prostate.
Newer surgical procedures may preserve sexual
function.
Medications are available to shrink enlarged
Cancer of the prostate
is the second most common cancer among
men (lung cancer is first). Most cases
occur in men over the age of 50
years.
 Treatment may include surgery to remove
the prostate, radiation therapy, or hormone
therapy to reduce the patient’s level of
testosterone
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