CHAPTER NINE
REPRODUCTIVE
SYSTEM
THE REPRODUCTIVE SYSTEM
The power of reproductive is one of the essential
characteristics of life Reproduction of the species of two
sexes ,both of which play their parts in the formation of a
new individual .
The reproductive organs of the male and female differ in
anatomical structure and arrangement ,each being
adapted to the functional activities they are required to
perform.
The male reproductive system
The function of the male organs is to form spermatozoa or
sperms and implant them within the female so that they
can meet the ova. The system is divided into the external
organs (the penis,containing the urethra), the internal
organs (two testes, vas deferens, seminal vesicles and their
ducts , and the prostate gland)
EXTERNAL ORGANS
1scrotum is an outpouhing wall the abdominal
wall and is divided into two sacs , one for each
testis and its epididymis . During fetal
development , the testes are located in the
abdomen ,but during the seventh month of
intrauterine development ,they descend into the
scrotum. This descent is essential for normal
sperm production during adulthood , since
sperm formation requires a temperature
several degrees lower than normal internal body
temperature .
2-penis ;it has a gland , a body , and a root . The 
urethra opens at the tip of the gland . The male
urethra serves not only for voiding the urine from
the bladder , but also for ejaculating the seminal
fluid . The penis consists almost entirly of three
cylindrical vascular compartments , which ,
during sexual excitation , become engorged with
blood and the penis becomes rigid . It also consist
of erectile tissue , which becomes firm and rigid
when congested with blood . The main function of
the penis is to implant sperms within the female.
2-INTERNAL ORGANS
1-the testis is one of the paired male reproductive or
seminal glands situated in the scrotum. The sperm
formation or spermatogenesis and the male sex
hormones are produced in the testes. The sites of the
spermatogenesis are the many tiny , convoluted
seminiferous tubule . The wall of the tubule has a
layer of smooth muscle cells that are responsible for
peristaltic movements of the tubule, and is composed
of developing germ cells . The Leydig cells , or
interstitial cells , which lie in small connective tissue
space between tubules, are the cells that secrete
testosterone .
**EPIDIDYMIS
From the seminiferous tubules, the sperm pass 
through the rete testis and efferent ductules into a
single convoluted duct lying close to the
posterior border of the testis ,called epididymis. In
turn it draining each testis leads to a vas deferens
. The vas deferens and the portion of the
closest to it serve as a storage epididymis
reservoir for sperm ,holding them until sexual
arousal leads to ejaculation. Also , in the
epididymis the sperm undergo a further
maturation process.
VAS DEFERENS
Or seminal ducts is a large thick-walled tube ,which
serves to transmit and store the seminal fluid. After
entering the abdomen ,the two vas deferens-one from
each side –near the prostate join the excretory duct of
the seminal vesicle, thus forming the ejaculatory duct
.
4-spermatic cord consists of vas deferens and the
blood and lymph vessels and nerves supplying the
testis and of the epididymis . It passes to the testis
through a slit like passage ,the inguinal canal, in the
abdomen wall.
5-seminal vesicles is a paired organ, located between
the fundus of the bladder and the rectum . The
seminal vesicles are the reservoir for the seminal
fluid . They also produce a secretion which is a
constituent of this fluid .
6- Ejaculatory duct is formed by junction of the vas
deferens and the duct of the seminal vesicle. It
passes through the substance of the prostate and
opens into the prostatic part of the urethra .
7-The prostate gland is a single dount-shaped gland
below the bladder and surrounding the upper part of
the urethra ,into which it secretes fluid through
hundreds of tiny openings in the side of the urethra
. The prostate gland and seminal vesicles 
secrete the bulk of the fluid in which ejaculated
sperm are suspended , this fluid , plus the
sperm cells , constitute semen , the sperm
contributing only a few percent of the total
volume . The glandular secretions contain a
large number of different chemical substances
, including nutrients , buffers for protecting the
sperm against the acidic vaginal secretion ,
and prostaglandin .
8- The bulbourethral glands or Cowper’s glands 
are a paired organ , lying below the prostate ,
drain into the urethra just after it leaves the
prostate. They contribute a small volume of
mucoid secretion .
The system of ducts through which the sperm 
are transported and the glands lining or
emptying into the ducts are termed the
accessory reproductive organs .
SPERMATOGENESIS
The seminiferous cells change by a series of complex
transformations into spermatozoa. This process is called
spermatogenesis . The undifferentiated germ cells begin to
divide at puberty (12-15 years old) . Testosterone required
for initiation and maintenance of spermatogenesis .
Luteinizing
Hormone (LH) acts on the leydig cells to stimulate
testosterone secretion . Follicle stimulating hormone (FSH)
acts on the Sertoli cells , which nourish developing sperm
and secrete paracrine agents that stimulate sperm
proliferation and differentiation . The normal human male
manufactures approximately 30 million sperm per day .
The average volume of expelled semen is 3 ml , containing
300 million sperm .
FEMAL REPRODUTIVE SYSTM
The female organs are adapted to form ova or eggs
which, if fertilized by spermatozoa, remain in the cavity
of the uterus. Here an embryo or foetusis formed and is
retained until the second individual is capale of a
separate and independent existence.
The female reproductive system (Figure 34) includes
the two ovaries and the female reproductive tract- two
uterine tubes, a uterus , and vagina. These structres are
also termed the female internal genitialia .In the female
, unlike in the male, the urinary and reproductive duct
systems are entirely separate from each other.
The female reproductive system (Figure 34) 
includes the two ovaries and the female
reproductive tract- two uterine tubes, a uterus ,
and vagina. These structres are also termed
the female internal genitialia .In the female ,
unlike in the male, the urinary and reproductive
duct systems are entirely separate from each
other.
Oogenesis is the production of gametes- the ova. At birth,
afemale's ovaries contain an estimated total of 2to 4 million
eggs , and no new ones appear after birth .Only a few ,
perhaps 400 , are destined to be ovulated . Throughout their
life in the ovaries ,the eggs exist in structures known as
follicles . Maturation of follicles begins at sexual maturity. As
a follicle matures the cells which compose its wall proliferate
and the follicle enlarges, a cavity filled with fluid forms
inside. A mature follicle is called a graafian follicle.
1-An ovary is one of a pair of organs. It is a sexual gland in
which female cells develop and mature, and female sex
hormones are produced (estrogen, progesterone, inhibin,
relaxin, and activin).


Oogenesis is the production of gametes- the ova. 
At birth, afemale's ovaries contain an estimated
total of 2to 4 million eggs , and no new ones
appear after birth .Only a few , perhaps 400 , are
destined to be ovulated . Throughout their life in
the ovaries ,the eggs exist in structures known as
follicles . Maturation of follicles begins at sexual
maturity. As a follicle matures the cells which
compose its wall proliferate and the follicle
enlarges, a cavity filled with fluid forms inside. A
mature follicle is called a graafian follicle.
A follicle takes about 28 days . The ovum present in the
follicle develops as the follicle matures, undergoing
complex changes. The wall of a mature follicle thins and
ruptures. The ovum present in the follicle is carried away by
the flow of fluid into the peritoneal cavity , and it enters the
uterine tube (oviduct). The maturation of the female germ
cell in the follicle of the ovary and its leaving the graafian
follicle is called ovulation. A corpus luteum (yellow body)
forms at the site of the ruptured graafian follicle. A corpus
luteum secretes estrogen, progesterone and inhibin . If
pregnancy occurs, the corpus luteum persists till the end of
it and performs the function of an endocrine gland . During
approximately the first 2 months of pregnancy, almost the
estrogen and progesterone are supplied by the extremely
active corpus luteum.

If no fertilization occurs, the intimately connected with
menstruation , a periodic discharge of a sanguineos fluid
from the uterus. During pregnancy both ovulation and
menstruation cease. Ovulation and menstruation are
observed from the age of 12- 16 to 45-50 , after which the
woman has the so-called menopause. At this time ovarian
function and menstruation cease.
In terms of ovarian function, therefore, the menstrual cycle
may be divided into two phase approximately equal in length
and separated by ovulation (1) the follicular phase , during
which a single mature follicle and secondary ooccyte
develop, and (2) the luteal phase , beginning after ovulation
and lasting until the demise of corpus luteum.


2- The uterus is a hollow, thick-walled 
muscular organ lying between the urinary
bladder and rectum. It is the source of
bleeding during and it menstruation houses
the fetus during pregnancy. The uterus expels
the fetus at the end of pregnancy by the
concentration of its muscular walls. The lower
portion of the uterus is the cervix. A small
opening in the cervix leads to the vagina, the
canal leading from the uterus to the outside.
3- Uterine tubes,also known as oviducts or 
fallopian tubes,are not directly attached to the
ovaries but open in to the abdominal cavity
close to them.The opening of each uterine tube
is funnel-shaped and surrounded by long,fingerlike projections(the fimbriae) lined with ciliated
epithelium.The other ends of the uterine tubes
are attach to the uterus and empty directly into
its cavity
The tube function is to collect the ova discharged
from ovary in its fimbriated end, and pass them
along its interior towards the cavity of the uterus by
the action of its ciliated epithelium.Fertilization of
the ovum by spermatozoa usually takes place in the
tube. The fertilized ovum begins to divide and an
embryo develops.The developing embryo moves
along the uterine tube to the uterus. The vibrations
of the cilia of the ciliated epithelium and the
contractions of the wall of the uterine tube
apparently help the embryo in its movement.
II-The female external genitalia include the 
mons pubis, labia majora,labia minora, clitoris,
vestibule of the vagina,and vestibular glands.
The term vulva is another name for all these
structure.
4- The vagina is a tube 8 to 10 cm long.During
copulation the seminal fluid containing
spermatozoa is discharged form the penis into the
vagina. The spermatozoa are motile, and swim
from the vagina into the uterine cavity and thence
into the uterine tubes. During parturition the fetus
passes from the uterus out of the body through the
vagina. The vagina is lined by a thin type of skin
which is thrown into a number of transverse folds
and is kept moist by the secretion of the mucous
glands present in the cervix. This secretion is
slightly acid.
CONTROL OF OVARIAN FUNCTION
The menstrual cycle results from a finely tuned
interplay of hormones secreted by the ovaries,
the anterior pituitary, and the hypothalamus.
During the early and middle follicular phases,
FSH stimulates the granulose cells to
proliferate and secrete estrogen. During the
late follicular phase, plasma estrogen becomes
high enough to elicit a surge of LH, which then
causes, via the granulose cell,
Completion of the egg`s maturation, 
ovulation,
and formation of the corpus luteum.
During the luteal phase, under the influence of
small of LH, the corpus luteum secretes
progesterone and estrogen. Regression of the
corpus luteum results in a cessation of the
secretion of these hormones.
MENSTRUAL CYCLE
The phases of the menstrual cycle can also be 
named in terms of uterine events. Day 1 is the
first day of menstrual bleeding, and the entire
period of menstruation is known as the
menstrual phase, which is generally about 3 to
5 days in atypical 28 day cycle. During this
period the epithelial lining of uterus - the
endometrium- degenerates, restulting in the
menstrual flow.
The amount of fluid, which consists of blood, 
mucin and epithelial cell varies between 90200 ml. The menstrual flow then ceases, and
the endometrium begins to thicken as its
regenerates. This period of growth, the
prolifeerative phase,lasts for the 10 days or so
between cessation of menstruation and the
occurrence of ovulation. Soon after ovulation,
the endometrium begins to secrete various
substances, and part of the menstrual cycle
between ovulation and the onset of the next
mentruation is call secretory phase.
‫كتابة‪:‬‬
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