The female reproductive system has several key functions: formation of egg cells, reception of sperm, provision of an environment for fertilization and fetal development, childbirth, and lactation. The female reproductive organs include the ovaries, which produce egg cells and hormones, and the uterus, which nourishes a developing fetus. At birth, the sex of an individual is determined by the chromosomes inherited - XX for female and XY for male. Fertilization occurs when an egg is fused by a sperm cell in the fallopian tubes. The placenta functions to exchange nutrients, gases, and waste between the mother and developing fetus. Childbirth is stimulated by hormones like oxytocin and prostaglandins that trigger powerful uterine contractions

1. Reproductive physiology
BY TESFAHUN B. (BScN)

2. The functions of the female reproductive system are:
Formation of egg cell
Reception of sperm
Provision of suitable environments for
fertilization and fetal development
Parturition (childbirth)
Lactation, the production of breast milk, which
provides
Complete nourishment for the baby in its early
life.

3. Introduction
• Early embryonic gonads can become either testes or
ovaries.
• A particular gene on the Y chromosome induces the
embryonic gonads to become testes.
• Females lack a Y chromosome, and the absence of this
gene causes the development of ovaries.
• The embryonic testes secrete testosterone, which induces
the development of male accessory sex organs and
external genitalia.
• The absence of testes(rather than the presence of ovaries)
in a female embryo causes the development of the female
accessory sex organs

4. • In sexual reproduction, germ cells ,or
gametes(sperm and ova), are formed within the
gonads(testes and ovaries) by a process of
reduction division, or meiosis.
• During this type of cell division, the normal
number of chromosomes inhuman cells—forty-
six—is halved, so that each gamete receives
twenty-three chromosomes.
• Fusion of a sperm cell and ovum(egg cell) in the
act of fertilization results in restoration of the
original chromosome number of forty-six in the
zygote ,or fertilized egg.

5. Sex Determination
 Each zygote inherits twenty-three chromosomes
from its mother and twenty-three chromosomes
from its father.
 This does not produce forty-six different
chromosomes, but rather twenty three pairs of
homologous chromosomes.
 The twenty-third pair of chromosomes are the sex
chromosomes.
 In a female, these consist of two X chromosomes
,where as in a male there is one X chromosome and
one Y chromosome.
 The X and Y chromosomes look different and contain
different genes

6. The gametes are said to be haploid(they contain
only half the number of chromosomes in the
diploid parent cell).
Because all ova contain one X chromosome,
whereas some sperm are X-bearing and others
are Y-bearing ,the chromosomal sex of the
zygote is determined by the fertilizing sperm
cell.
If a Y-bearing sperm cell fertilizes the ovum, the
zygote will be XY and male; if an X-bearing
sperm cell fertilizes the ovum, the zygote will be
XX and female

7. • In Klinefelter’s syndrome,the affected person
has 47 instead of 46 chromosomes because of
the presence of an extra X chromosome.
• This person, with an XXY genotype, will
develop testes and have a male phenotype
despite the presence of two X chromosomes.
• Patients with Turner’s syndrome, who have the
genotype XO (and therefore have only 45
chromosomes), have poorly developed
(“streak”) gonads and are phenotypically
female.

8. Formation of Testes and Ovaries
• Following conception, the gonads of males and
females are similar in appearance for the first 40 or
50 days of development.
• At this stage, the embryonic structures have the
potential to become either testes or ovaries.
• The hypothetical substance that promotes their
conversion to testes has been called the testis-
determining factor (TDF).
• The structures that will eventually produce sperm
with in the testes, the seminiferous tubules, appear
very early in embryonic development between 43
and 50 days of conception

9.  The tubules contain two major cell types: germinal and
non-germinal.
 The germinal cells are those that will eventually become
sperm through meiosis and subsequent specialization.
 The non germinal cells are called Sertoli cells and the
Leydig (or interstitial) cells.
 Leydig cells in the embryonic testes secrete large
amounts of male sex hormones, or androgens. The major
androgen secreted by these cells is testosterone.
 Testosterone secretion during embryonic development in
the male serves the very important function of
masculinizing the embryonic structures.
 In contrast to the rapid development of the testes, the
functional units of the ovaries—called the ovarian
follicles—do not appear until the second trimester of
pregnancy

10. • As the testes develop, they move within the
abdominal cavity and gradually descend into the
scrotum.
• Descent of the testes is sometimes not complete
until shortly after birth.
• The temperature of the scrotum is maintained at
about 35°C, about 3°C below normal body
temperature. This cooler temperature is needed
for spermatogenesis.
• The fact that spermatogenesis does not occur in
males with undescended testes—a condition
called cryptorchidism

11. Development of Accessory Sex Organs
and External Genitalia
• In addition to testes and ovaries, various
internal accessory sex organs are needed for
reproductive function.
• Male accessory organs are derived from the
wolffian (mesonephric) ducts, and female
accessory organs are derived from the
müllerian (paramesonephric) ducts

12. • The secretion of testosterone by the Leydig cells
of the testes subsequently causes growth and
development of the wolffian ducts into male
accessory sex organs :the epididymis, ductus
(vas) deferens, seminal vesicles,and ejaculatory
duct.
• The external genitalia of males and females are
essentially identical during the first 6 weeks of
development

13. • The secretions of the testes masculinize these
structures to form the penis and spongy (penile)
urethra ,prostate ,and scrotum.
• In the absence of secreted testosterone, the genital
tubercle that forms the penis in a male will
become the clitoris in a female.
• The penis and clitoris are thus said to be
homologous structures.

14. Endocrine Regulation of Reproduction
• The functions of the testes and ovaries are
regulated by gonadotropic hormones secreted
by the anterior pituitary.
• The gonadotropic hormones stimulate the
gonads to secrete their sex steroid hormones.
• This interaction between the anterior pituitary
and the gonads forms a negative feedback loop.
• Before puberty, there are equally low blood
concentrations Of sex steroids-androgens and
estrogens-in both males and females

15. • During puberty, the gonads secrete increased
amounts of sex steroid hormones as a result of
increased stimulation by gonadotropic hormones
from the anterior pituitary.
• The anterior pituitary produces and secretes two
gonadotropic hormones—FSH and LH.
• The gonadotropic hormones of both sexes have
three primary effects on the gonads:
1. Stimulation of spermatogenesis or oogenesis
2. Stimulation of gonadal hormone secretion; and
3. Maintenance of the structure of the gonads(the
gonads atrophy if the pituitary gland is removed).

16. The Onset of Puberty
• Secretion of FSH and LH is high in the newborn, but
falls to very low levels a few weeks after birth.
• Gonadotropin secretion remains low until the beginning
of puberty, which is marked by rising levels of FSH
followed by LH secretion.
• This rise in gonadotropin secretion is a result of two
processes:
(1) Maturational changes in the brain that result in
increased GnRH secretion by the hypothalamus and
(2) Decreased sensitivity of gonadotropin secretion to the
negative feedback effects of sex steroid hormones

17. Characteristic Age of First Appearance Hormonal Stimulation
Appearance of breast buds 8-13 Estrogen, progesterone,
growth hormone,
thyroxine, insulin, cortisol
Pubic hair 8-14 Adrenal androgens
Menarche (first menstrual flow) 10-16 Estrogen and progesterone
Axillary (underarm) hair About 2 years after the
appearance of pubic hair
Adrenal androgens
Eccrine sweat glands and
sebaceous glands; acne
(from blocked sebaceous glands)
About the same time as
axillary hair growth
Adrenal androgens

18. Characteristic Age of First Appearance Hormonal Stimulation
Growth of testes 10–14
Testosterone, FSH, growth
hormone
Pubic hair
10--15 Testosterone
Body growth
10-16 10--16
Growth of penis 10-15 Testosterone
Growth of larynx (voice lowers 10-14 Testosterone

19. Male Reproductive System
• The Leydig cells in the interstitial tissue of the testes are
stimulated by LH to secrete testosterone, a potent androgen
that acts to maintain the structure and function of the male
accessory sex organs and to promote the development of
male secondary sex characteristics.
• The Sertoli cells in the seminiferous tubules of the testes are
stimulated by FSH.
• The cooperative actions of FSH and testosterone are
required to initiate spermatogenesis
• Testosterone is by far the major androgen secreted by the
adult testis.
• This hormone and its derivatives (the 5α-reduced
androgens)are responsible for initiation and maintenance of
the body changes associated with puberty in males.

20. Male Accessory Sex Organs
• The seminiferous tubules are connected at both ends to
a tubular network called the rete testis.
• The epididymis is a tightly coiled structure, about 5
meters long if stretched out, that receives the tubular
products.
• Spermatozoa enter at the “head” of the epididymis and
are drained from its “tail” by a single tube, the ductus,
or vas deferens.
• Spermatozoa that enter the head of the epididymis are
non motile.
• This is partially due to the low pH of the fluid in the
epididymis and ductus deferens.
• The pH is neutralized by the alkaline prostatic fluid
during ejaculation, so that the sperm are fully motile

22. • Sperm obtained from the seminiferous tubules
cannot fertilize an ovum.
• The epididymis serves as a site for sperm
maturation and for the storage of sperm between
ejaculations.
• The ductus deferens carries sperm from the
epididymis out of the scrotum into the pelvic cavity.
• The seminal vesicles then add secretions that pass
through their ducts; at this point, the ductus deferens
becomes an ejaculatory duct.
• The ejaculatory ductis short (about 2 cm), however,
because it enters the prostate and soon merges with
the prostatic urethra.

23. Cont…
• The prostate adds its secretions through numerous
pores in the walls of the prostatic urethra, forming
a fluid known as semen.
• The seminal vesicles secrete fluid containing
fructose, which serves as an energy source for the
spermatozoa.
• This fluid secretion accounts for about 60% of the
volume of the semen.
• The fluid contributed by the prostate contains
citric acid, calcium, and coagulation proteins.

25. • Erection, Emission, and Ejaculation
• Erection, accompanied by increases in the length
and width of the penis, is achieved as a result of
blood flow into the “erectile tissues” of the penis.
• As the erectile tissues become engorged with
blood and the penis becomes turgid, venous
outflow of blood is partially occluded, thus aiding
erection.
• The term emission refers to the movement of
semen into the urethra, and
• Ejaculation refers to the forcible expulsion of
semen from the urethra out of the penis.

26. • Emission and ejaculation are stimulated by
sympathetic nerves, which cause peristaltic
contractions of the tubular system, contractions
of the seminal vesicles and prostate, and
contractions of muscles at the base of the penis.
• Erection is controlled by two portions of the
central nervous system—the hypothalamus in
the brain and the sacral portion of the spinal
cord.

28. Female Reproductive System
• The two ovaries, about the size and shape of large
almonds, are suspended by means of ligaments from
thepelvic girdle.
• Extensions called fimbriae of the uterine (fallopian)
tubes partially cover each ovary.
• Ova that are released from the ovary—in a process
called ovulation—are normally drawn into the uterine
tubes by the action of the ciliated epithelial lining of
the tubes.
• The lumen of each uterine tube is continuous with the
uterus(or womb), a pear-shaped muscular organ
heldin place within the pelvic cavity by ligaments.
.

29. CONT…
• The uterus consists of three layers.
• The outer layer of connective tissue is the
perimetrium, the middle layer of smooth
muscle is the myometrium, and the inner
epithelial layer is the endometrium.
• The stratum functionale, which cyclically
grows thicker as a result of estrogen and
progesterone stimulation, is shed at
menstruation

30. • The uterus narrows to form the cervix, which opens
to the tubular vagina.
• The only physical barrier between the vagina and
uterus is a plug of cervical mucus.
• These structures, the vagina, uterus, and fallopian
tubes, constitute the accessory sex organs of the
female.
• The vaginal opening is located immediately posterior
to the opening of the urethra.
• Both openings are covered by longitudinal folds—the
inner labia minora and outer labia majora.
• The clitoris, a small structure composed largely of
erectile tissue, is located at the anterior margin of the
labia minora

32. Fertilization, Pregnancy, and Parturition
 During the act of sexual intercourse, the male ejaculates an
average of 300 million sperm into the vagina of the female.
This tremendous number is needed because of the high sperm
fatality; only about 100 survive to enter each fallopian tube.
 A woman usually ovulates only one ovum a month, for a total
of less than 450 ova during her reproductive years.
 Fertilization normally occurs in the uterine tubes.
 Each sperm contains a large, enzyme-filled vesicle above its
nucleus, known as an acrosome, that is central to this task.
 A fertilized egg, or zygote, containing the diploid number of
chromosomes (forty-six).

33. • On the sixth day following fertilization, the
blastocyst attaches to the uterine wall, with the
side containing the inner cellmass positioned
against the endometrium.
• When implantation occurs,the trophoblast cells
of the chorion secrete chorionic
gonadotropin,or hCG. This hormone is
identical to LH in its effects and therefore is
able to maintain the corpus luteum past the
time when it would otherwise regress.
• The secretion of estradiol and progesterone is
thus maintained and menstruation is normally
prevented

34. Formation of the Placenta and Amniotic Sac
 As the blastocyst implants in the endometrium and the
chorion develops, the cells of the endometrium also undergo
changes.
 These changes, including cellular growth and the
accumulation of glycogen, are collectively called the
decidual reaction.
 The maternal tissue in contact with the chorion frondosum
is called the decidua basalis.
 These two structures, chorion frondosum(fetal tissue) and
decidua basalis (maternal tissue), together form the
functional unit known as the placenta.
 The embryo, together with its umbilical cord, is therefore
located within the fluid-filled amniotic sac(the volume is
increased and the concentration changed by urine from the
fetus; also contains sloughed off from the fetus, placenta,
and amniotic sac).

35. • Functions of placenta:-
• a) Hormonal:-secrete hCG, progestrone and Estrogen
• b) Metabolic:-synthesizing glycogen and cholesterol,
energy source for the developing fetus..
• c) To exchange nutrients, gases and fetal metabolic
wastes.
• Labor and Parturition
• Powerful contractions of the uterus are needed to expel
the fetus in the sequence of events called labor.
• These uterine contractions are known to be stimulated by
two agents:
• (1) oxytocin, hormone produced in the hypothalamus and
released by the posterior pituitary (and also produced by
the uterus itself), and
• (2) prostaglandins, a class of cyclic fatty acids with
paracrine functions produced within the uterus

36. • The concentration of oxytocin receptors in the
myometrium increases dramatically as a result of
estrogen stimulation making the uterus more sensitive
to oxytocin.
• These effects culminate in parturition,or childbirth.
• Oxytocin may also play a role in promoting the
involution (reduction in size) of the uterus following
delivery.
• Lactation
• During pregnancy, high levels of progesterone stimulate
the development of the mammary alveoli and estrogen
stimulates proliferation of the tubules and ducts.
• The production of milk proteins, including casein and
lactalbumin, is stimulated after parturition by prolactin