Basics of anatomy and physiology of human reproductive system. Prepared for educational purpose for undergraduate B Pharm students.

1. Unit: V
5.1: Reproductive System
Presented by: Prof.Mirza Anwar Baig
Anjuman-I-Islam's Kalsekar Technical Campus
School of Pharmacy,New Pavel,Navi Mumbai,Maharashtra
1
1

2. Content:
▪ Anatomy of male and female reproductive
system.
▪ Functions of male and female reproductive
system, sex hormones.
▪ Physiology of menstruation
▪ Spermatogenesis,oogenesis, fertilization
pregnancy and parturition.
2

3. Anatomy of Male Reproductive System
The male reproductive system include
• Testes: Produce sperm and secrete hormones.
• A system of ducts (epididymis, ductus deferens,ejaculatory ducts,
and urethra): Transports and stores sperm, assists in their
maturation, and conveys them to the exterior.
• Accessory sex glands (seminal vesicles, prostate, and
bulbourethral glands): Provide semen which contains sperm plus
the secretions.
• Supporting structures (scrotum and the penis): The
penis delivers sperm into the female reproductive tract and the
scrotum supports the testes. 3

4. Scrotum
• A supporting structure for the testes.
• Consists of loose skin that hangs from the root of the penis .
• Externally, looks like a single pouch of skin separated into lateral
portions by a median ridge called the raphe
• Internally, the scrotal septum divides the scrotum into two sacs, each
containing a single testis.
• Normal sperm production requires a temperature about 2–3C below core
body temperature.
• The location of the scrotum (outside the pelvic cavity.) and the
contraction of its muscle fibers regulate the temperature of the testes.
• In cold temperatures, the cremaster and dartos muscles contract which
moves the testes closer to the body, where they can absorb body heat.
• Exposure to warmth reverses these actions
4

5. Scrotum contd…
5

6. Testes
• Size and shape: The testes are paired
oval glands in the scrotum measuring
about 5 cm long and 2.5 cm in diameter.
Each testis (singular) has a mass of 10–
15 grams.
• Location: The testes develop near the
kidneys, in the posterior portion of the
abdomen.
• Coverings:
✓ Tunica vaginalis, partially covers the
testes.
✓ Tunica albuginea, a white fibrous
capsule; it extends inward, forming septa
that divide the testis into a series of
internal compartments called lobules.
✓ The tunica vasculosa. This consists of a
network of capillaries supported by
delicate connective tissue.
6

7. Internal structure of the testes
▪ Each testes consist of 200 to 300
lobules and each lobule contains 1
to 4 convoluted loops.
▪ Each loop composed of germinal
epithelial cells, called seminiferous
tubules.
▪ Between the tubules there are
groups of interstitial cells (of Ley
dig) that secrete the hormone
testosterone after puberty.
▪ At the upper pole of the testis the
tubules combine to form a single
tubule(6 m in length) is repeatedly
folded and tightly packed into a
mass called the epididymis.
▪ It leaves the scrotum as the deferent
duct (vas deferens) in the spermatic
cord.
▪ Blood and lymph vessels pass to the
testes in the spermatic cords.
7

8. 8

9. Internal structure of the testes Contd…
Cells of the testes
1. Sertoli cells:
▪ Present in large number in the seminiferous tubules.
▪ Support and protect developing spermatogenic cells in several ways
– nourishes spermatocytes, spermatids, and sperm;
– phagocytize excess spermatid cytoplasm as development proceeds;
– control movements of spermatogenic cells
– release of sperm into the lumen of the seminiferous tubule.
– They also produce fluid for sperm transport,
– secrete the hormone inhibin, and regulate the effects of testosterone and FSH .
2. Leydig (interstitial) cells :
• Present in between the seminiferous tubules
• Secrete testosterone, the most prevalent androgen.
• Testosterone promotes the development of masculine characteristics &
man’s libido (sexual drive).
9

10. Internal structure of the testes Contd…
Blood– Testis Barrier:
• A tight junctions joins the two neighboring Sertoli cells
• All substances must first pass through the Sertoli cells
before they can reach the developing sperm.
• It prevents an immune response against the
spermatogenic cell’s surface antigens, which are
recognized as “foreign” by the immune system.
• The blood–testis barrier does not include spermatogonia
10

11. Spermatogenesis (Formation of sperm)
11

12. Spermatogenesis (Formation of sperm)
• In humans, spermatogenesis takes 65–75 days.
• It begins with the spermatogonia, which contain the diploid (2n) number of
chromosomes .
• Spermatogonia are types of stem cells; when they undergo mitosis, some
spermatogonia remain near the basement membrane of the seminiferous
tubule in an undifferentiated state to serve as a reservoir of cells for future
cell division and subsequent sperm production.
• The rest of the spermatogonia lose contact with the basement membrane,
squeeze through the tight junctions of the blood–testis barrier, undergo
developmental changes, and differentiate into primary spermatocytes .
• Primary spermatocytes, like spermatogonia, are diploid (2n); that is, they
have 46 chromosomes.
12

13. Spermatogenesis (Formation of sperm) contd..
▪ Primary spermatocyte (2n) undergoes Meiosis I and II.
▪ In Meiosis I, primary spermatocyte replicates and gives two cells
with 23 Chromosomes (n) called secondary spermatocytes.
▪ Each secondary spermatocytes (n) is made up of two chromatids
still attached by centromare.
▪ In meiosis II, secondary spermatocytes (n)four haploid cells forms are
called spermatids (n).
▪ A single primary spermatocyte therefore produces four spermatids
via two rounds of cell division (meiosis I and meiosis II).
13

14. Spermatogenesis (Formation of sperm) contd…
1) The final stage of spermatogenesis, spermiogenesis (development of haploid
spermatids into sperm).
2) No cell division occurs in spermiogenesis; each spermatid becomes a single
sperm cell.
3) During this process, spherical spermatids transform into elongated, slender
sperm.
4) An acrosome forms atop the nucleus, which condenses and elongates, a
flagellum develops, and mitochondria multiply.
5) Sertoli cells dispose of the excess cytoplasm .
6) Finally, sperm are released from their connections to Sertoli cells, an event
known as spermiation.
7) Sperm then enter the lumen of the seminiferous tubule.
8) Fluid secreted by Sertoli cells pushes sperm along their way, toward the ducts
of the testes.
14

15. Structure of sperm
15

16. What is sperm?
• 300 million/day sperm complete the process of spermatogenesis.
• A sperm is about 60 μm long.
• The major parts of a sperm are the head and the tail.
• The flattened, pointed head of the sperm is about 4–5 μ m long. It contains a nucleus
with 23 highly condensed chromosomes.
• Covering the anterior two-thirds of the nucleus is the acrosome (acro- atop; -some
body), a caplike vesicle filled with enzymes that help a sperm to penetrate a secondary
oocyte to bring about fertilization.
• Among the enzymes are hyaluronidase and proteases.
• The tail of a sperm is subdivided into four parts: neck, middle piece, principal piece,
and end piece.
• The neck is the constricted region just behind the head that contains centrioles. The
centrioles form the microtubules that comprise the remainder of the tail.
• The middle piece contains mitochondria arranged in a spiral, which provide the energy
(ATP) for locomotion of sperm to the site of fertilization and for sperm metabolism.
• The principal piece is the longest portion of the tail, and the end piece is the terminal,
tapering portion of the tail.
• Once ejaculated, most sperm do not survive more than 48 hours within the female
reproductive tract.
16

17. Hormonal Control of Testes:
17
▪ Although the initiating factors are
unknown, GnRH stimulates
gonadotrophs in the anterior
pituitary to increase LH and FSH
Secretion.
▪ LH stimulates Leydig cells, to
secrete the hormone testosterone
(synthesized from cholesterol)
▪ In some target cells (external
genitals and prostate), 5 alpha-
reductase converts testosterone to
called dihydrotestosterone (DHT).

18. Hormonal Control of Testes contd:
▪ FSH and testosterone act synergistically on the Sertoli cells to stimulate
secretion of androgen-binding protein (ABP) into the lumen of the
seminiferous tubules and into the interstitial fluid around the
spermatogenic cells.
▪ ABP binds to testosterone, keeping its concentration high.
▪ Testosterone stimulates the final steps of spermatogenesis in the
seminiferous tubules.
▪ Once the degree of spermatogenesis required has been achieved, Sertoli
cells release inhibin, inhibiting FSH secretion by the anterior pituitary.
▪ Testosterone and dihydrotestosterone produce several effects:
✓ Prenatal development. Development of ducts and the descent of the testes
development of the external genitals.
✓ Development of male sexual characteristics.
✓ Development of sexual function. male sexual behavior and spermatogenesis and to
sex drive (libido) in both males and females.
✓ Stimulation of anabolism heavier muscle and bone mass of most men as compared
to women.
18

19. Ducts and accessory organs
19

20. Ducts in Males
The spermatic cords
• Suspend the testes in the scrotum.
• Each cord contains a testicular artery, testicular veins, lymphatics, a deferent
duct and testicular nerves, and is attached to the testis on the posterior wall.
The deferent duct. This is some 45 cm long. It passes upwards from the testis
through the inguinal canal and ascends medially towards the posterior wall of
the bladder where it is joined by the duct from the seminal vesicle to form the
ejaculatory duct.
The nerve supply: Provided by branches from the 10th and llth thoracic nerves.
Ejaculatory ducts:
• Two tubes about 2 cm long, each formed by the union of the duct from a
seminal vesicle and a deferent duct.
• They pass through the prostate gland and join the prostatic urethra, carrying
seminal fluid and spermatozoa to the urethra.
• The ejaculatory ducts are composed of the same layers of tissue as the seminal
vesicles.
20

21. Accessory sex glands
Seminal vesicles
• These are two small fibromuscular pouches lined with
columnar epithelium, lying on the posterior aspect of the
bladder.
• Each seminal vesicle joins with the corresponding deferent
duct to form an ejaculatory duct.
Functions of the seminal vesicles
• The seminal vesicles contract and expel their stored
contents,seminal fluid, during ejaculation.
• Seminal fluid = 60% of the bulk of the ejaculated fluid at
male orgasm, contains nutrients to support the sperm during
their journey through the female reproductive tract.
21

22. Prostate gland
• Location: Lies in the pelvic cavity in front of the rectum and behind
the symphysis pubis, surrounding the first part of the urethra.
• It consists of an outer fibrous covering, a layer of smooth muscle
and glandular substance composed of columnar epithelial cells.
Functions of the prostate gland
• Secretes a thin, milky fluid that makes up about 30% of semen, and
gives it its milky appearance.
• It is slightly alkaline, which provides a protective local environment
for sperm arriving in the acidic vagina.
• It also contains a clotting enzyme, which thickens the semen in the
vagina, increasing the likelihood of semen being retained in the
vicinity of the cervix.
22

23. Bulbourethral glands or Cowper’s glands:
▪ Paired and are about the size of peas.
▪ They are located inferior to the prostate on either side of the
membranous urethra.
▪ Secrete alkaline fluid that neutralizes the acidic environment
of the urethra and mucus that lubricates the lining of the
urethra and the tip of the penis during sexual intercourse.
23

24. Semen ( seed)
• It’s a mixture of sperm and seminal fluid (secretions of the
seminiferous tubules, seminal vesicles, prostate, and bulbourethral
glands).
• A typical ejaculation volume is 2.5–5 mL, with 50–150 million
sperm per mL.
• Less than 20 million/mL sperm count, the male is likely to be
infertile.
• Semen has a slightly alkaline pH of 7.2–7.7 due to the higher pH
and fluid from the seminal vesicles, despite the slight acidity of
prostatic fluid.
• The prostatic secretion gives semen a milky appearance.
• Fluids from the seminal vesicles and bulbourethral glands give it a
sticky consistency.
• Seminal fluid provides sperm with a transportation medium,
nutrients, and protection from the hostile acidic environment of the
male’s urethra and the female’s vagina.
24

25. Semen ( seed) contd..
• Once ejaculated, liquid semen coagulates within 5 minutes due to
the presence of clotting proteins from the seminal vesicles.
• The proteins involved are different from those that cause blood
coagulation.
• Semen reliquefies after about 10 to 20 minutes, because prostate-
specific antigen (PSA) and other proteolytic enzymes produced by
the prostate break down the clot.
• Abnormal or delayed liquefaction of clotted semen may cause
complete or partial immobilization of sperm, thereby inhibiting their
movement through the cervix of the uterus.
25

26. Urethra and penis
Urethra:
• A common pathway for the flow of urine and semen.
• It is about 19 to 20 cm long
Consists of three parts.
• Prostatic urethra originates at the urethral orifice of the bladder and
passes through the prostate gland.
• Membranous urethra is the shortest and narrowest part and extends
from the prostate gland to the bulb of the penis.
• Spongiose or penile urethra lies within the corpus spongiosum of the
penis and terminates at the external urethral orifice in the glans
penis.
There are two urethral sphincters.
• Internal sphincter consists of smooth muscle fibres at the neck of the
bladder above the prostate gland.
• External sphincter consists of skeletal muscle fibres surrounding
the membranous part.
26

27. Penis
• The penis has a root and a body.
• The root lies in the perineum and the body
surrounds the urethra.
• It is formed by cylindrical masses of erectile tissue
and involuntary muscle.
• The urethra is covered by columns called corpora
cavernosa and corpus spongiosum.
• A triangular structure at the tip known as the glans
penis.
• Just above the glans the skin is folded upon itself
and forms a movable double layer, the foreskin or
prepuce.
• The penis is supplied by autonomic and somatic
nerves.
• Parasympathetic stimulation leads to filling of the
spongy erectile tissue with blood,caused by
arteriolar dilatation and venoconstriction, which
increases blood flow into the penis.
• The penis therefore becomes engorged and
erect, an essential prerequisite for coitus to occur.
27

28. Female Reproductive System
Divided into external and internal organs
External genitalia (vulva)
It consist of the
▪ Labia majora and labia minora,
▪ Clitoris,
▪ Vaginal orifice,
▪ Vestibule,
▪ Hymen and the vestibular glands (Bartholin's
glands).
Labia majora
– Two large folds which form the boundary of the
vulva.
– Composed of large numbers of sebaceous glands.
– At puberty hair grows on the mons pubis and on the
lateral surfaces of the labia majora.
Labia minora
▪ Two smaller folds of skin between the labia majora
▪ Containing numerous sebaceous glands.
▪ Cleft between the labia minora is the vestibule
( secretes secretions of vagina, urethra and ducts of
the greater vestibular glands )
28

29. Female Reproductive System
Clitoris
• Corresponds to the penis in the male.
• Contains sensory nerve endings and
erectile tissue.
• Has no reproductive significance.
Vestibular glands (Bartholin's glands)
• Situated one on each side near the vaginal
opening.
• Small pea size
• Secretes mucus (to keep vulva moist)
through ducts open lateral to hymen.
29

30. Female Reproductive System contd..
Internal genitalia
• Lie in the pelvic cavity
• Consist of following internal organs
o Vagina
o Uterus
o Two uterine tubes
o Two ovaries.
Vagina
▪ Fibromuscular tube
▪ Lined with stratified squamous epithelium,
▪ Connecting the external and internal organs of reproduction.
▪ Anterior wall is about 7.5 cm (3 inches) long
▪ Posterior wall about 9 cm long.
30

31. Vagina contd..
• The vagina has three layers:
– Outer covering of areolar tissue,
– Middle layer of smooth muscle
– Inner lining of stratified squamous epithelium that forms ridges or rugae.
• It has no secretary glands but the surface is kept moist by cervical secretions.
• Lactobacillus acidophilus bacteria are normally present, which secrete lactic
acid, maintaining the pH between 4.9 and 3.5.
• The acidity inhibits the growth of most other microbes that may enter the
vagina from the perineum.
Functions:
• Acts as the receptacle for the penis during coitus.
• Provides an elastic passageway through which the baby passes during
childbirth.
31

32. Uterus
• Hollow muscular pear-shaped organ,
flattened anteroposteriorly.
• Location: Lies in the pelvic cavity
between the urinary bladder and the
rectum.
• Size: 7.5 cm long, 5 cm wide and its
walls are about 2.5 cm thick. It weighs
from 30 to 40 grams.
Parts:
• The fundus. This is the dome-shaped
part of the uterus above the openings of
the uterine tubes.
• The body. This is the main part. It is
narrowest inferiorly at the internal os
where it is continuous with the cervix.
• The cervix ('neck' of the uterus). This
protrudes through the anterior wall of
the vagina, opening into it at the
external os.
32

33. Structure of the uterus
The walls of the uterus are composed of three layers of
tissue:
– Perimetrium,
– Myometrium
– Endometrium
Perimetrium
Anteriorly it extends over the fundus and the body (folded
on to the upper surface of the urinary bladder. This fold of
peritoneum forms the vesicouterine pouch).
Posteriorly the peritoneum extends over the fundus, the body
and the cervix, then it continues on to the rectum to form the
rectouterine pouch (of Douglas).
Laterally only the fundus is covered because the peritoneum
forms a double fold with the uterine tubes in the upper free
border. This double fold is the broad Ligament.
33

34. Structure of the uterus contd..
Myometrium
Thickest layer of tissue in the uterine wall.
Has smooth muscle fibres interlaced with areolar tissue, blood vessels and nerves.
Endometrium
columnar epithelium containing a large number of mucus-secreting tubular glands.
It is divided functionally into two layers.
• The functional layer is the upper layer and it thickens and becomes rich in
blood vessels in the first half of the menstrual cycle. If the ovum is not fertilised
and does not implant, this layer is shed during menstruation.
• The basal layer lies next to the myometrium, and is not lost during
menstruation. It is the layer from which the fresh functional layer is regenerated
during each cycle.
The upper two-thirds of the cervical canal is lined with this mucous membrane.
34

35. Supporting organs of uterus:
The broad ligaments.
• These are double fold of
peritoneum, one on each side of the
uterus.
• Hang down from the uterine tubes.
• Ovaries are attached to the
posterior wall, one on each side.
• Blood and lymph vessels and nerves
pass to the uterus and uterine tubes
between the layers of the broad
ligaments.
The round ligaments.
• Bands of fibrous tissue
• Present between the two layers of
broad ligament, one on each side of
the uterus.
35

36. Functions of the uterus
• After puberty, the endometrium of the uterus goes through a regular
monthly cycle of changes, the menstrual cycle, which is under the control
of hypothalamic and anterior pituitary hormones.
• The purpose of the cycle is to prepare the uterus to receive, nourish and
protect a fertilized ovum.
• The cycle is usually regular, lasting between 26 and 30 days.
• If the ovum is not fertilised a new cycle begins with a short period of
bleeding (menstruation).
• If the ovum is fertilised the zygote embeds itself in the uterine wall. The
uterine muscle grows to accommodate the developing baby, which is called
an embryo during its first 8 weeks, and a fetus for the remainder of the
pregnancy.
• Uterine secretions nourish the ovum before it implants in the endometrium,
and after implantation the rapidly expanding ball of cells is nourished by
the endometrial cells themselves.
36

37. • This is sufficient for only the first few weeks and the placenta is the organ
that takes over thereafter.
• Placenta, attached to the fetus by the umbilical cord, is firmly attached to
the wall of the uterus, and provides oxygen, nutrients to the growing baby
and gets rid of its wastes.
• During pregnancy (Approx. 40 weeks), the muscular walls of the uterus are
prevented from contracting and expelling the baby early by high levels of
the hormone progesterone secreted by the placenta.
• At the end of pregnancy (at term) the hormone oestrogen, which increases
uterine contractility, becomes the predominant sex hormone in the blood.
• Additionally, oxytocin is released from the posterior pituitary, and also
stimulates the uterine muscle.
• Control of oxytocin release is by positive feedback.
• During labour, the uterus forcefully expels the baby by means of powerful
rhythmical contractions.
37

38. Uterine tubes (Fallopian tubes)
• About 10 cm long
• Extend from the sides of the
uterus between the body and the
fundus.
• The end of each tube has
fingerlike projections called
fimbriae.
• The longest of these is the ovarian
fimbria which is in close
association with the ovary.
Structure of the uterine tubes
• Have an outer covering of
peritoneum (broad ligament)
• A middle layer of smooth muscle
lined with ciliated epithelium.
38

39. Function of the uterine tubes
▪ Convey the ovum from the ovary to the uterus by peristalsis
and ciliary movement.
▪ The mucus secreted by the lining membrane provides ideal
conditions for movement of ova and spermatozoa.
▪ Fertilization of the ovum usually takes place in the uterine
tube.
▪ Zygote is propelled into the uterus for implantation.
39

40. Ovaries
➢ Location: Lie in a shallow
fossa on the lateral walls of
the pelvis.
➢ Size: 2.5 to 3.5 cm long, 2
cm wide and 1 cm thick.
➢ Attachment: Each is
attached to the upper part
of the uterus by the
ovarian ligament and to
the broad ligament by the
mesovarium.
➢ Blood vessels and nerves
pass to the ovary through
the mesovarium
40

41. Structure of the ovaries:
• The ovaries have two layers of tissue.
The medulla.
This lies in the centre and consists of fibrous
tissue, blood vessels and nerves.
The cortex.
• Surrounds the medulla.
• It has a framework of connective tissue, or stroma,
covered by germinal epithelium.
• It contains ovarian follicles in various stages of
maturity, each of which contains an ovum.
• Before puberty the ovaries are inactive but the
stroma already contains immature (primordial)
follicles, which the female has from birth.
• During the childbearing years, about every 28
days, one ovarian follicle (Graafian follicle)
matures, ruptures and releases its ovum into the
peritoneal cavity.
• This is called ovulation and it occurs during most
menstrual cycles.
41

42. Functions of the ovaries
▪ FSH from anterior pituitary helps
in maturation of the follicle and
oestrogen secreted by the follicle
lining cells.
▪ LH from anterior pituitary
triggered ovulation.
▪ After ovulation, the follicle lining
cells develop into the corpus
luteum (yellow body) which
produces progesterone and some
estrogen.
▪ If the ovum is fertilized it embeds
itself in the wall of the uterus
where it grows and develops and
produces the hormone human
chorionic gonadotrophin (hCG).
42

43. • hCG stimulates the corpus luteum to
continue secreting progesterone and
oestrogen for the first 3 months of the
pregnancy, thereafter this function is
continued by the placenta.
• If the ovum is not fertilized the corpus
luteum degenerates and a new cycle
begins with menstruation.
• After degeneration corpus luteum converts
to corpus albicans.
• Sometimes more than one follicle matures
at a time, releasing two or more ova in the
same cycle which gives multiple
pregnancy.
43

44. Oogenesis (Formation of gametes )
• It begins in females before they are even born.
• During early fetal development, primordial (primitive) germ cells
differentiate within the ovaries and convert to oogonia (2n) stem cells
• Oogonia divide mitotically to produce millions of germ cells.
• Most of these germ cells degenerate in a process known as atresia.
• A few, however, develop into larger cells called primary oocytes that
enter prophase of meiosis I during fetal development but do not complete
that phase until after puberty.
44

45. Oogenesis (Formation of gametes) contd..
• During this arrested stage of
development, each primary oocyte is
surrounded by a single layer of flat
follicular cells, and the entire
structure is called a primordial
follicle.
• At birth, approximately 2,00000 to
20,00000 primary oocytes remain in
each ovary.
• Of these, about 40,000 are still
present at puberty, and around 400
will mature and ovulate during a
woman’s reproductive lifetime.
45

46. Oogenesis (Formation of gametes) contd..
• Each month after puberty until
menopause, FSH and LH further
stimulate the development of several
primordial follicles, although only one
will typically reach the maturity needed
for ovulation.
• A few primordial follicles start to grow,
developing into primary follicles.
• Each primary follicle consists of a
primary oocyte that is surrounded by
granulosa cells.
• As the primary follicle grows, it forms a
clear glycoprotein layer called the zona
pellucida between the primary oocyte
and the granulosa cells.
• In addition, stromal cells surrounding
the basement membrane begin to form
an organized layer called the theca
folliculi.
46

47. Oogenesis (Formation of gametes) contd..
• Primary follicle develops into a
secondary follicle.
• Secondary follicle theca layer
divided in to two layers.
(1) Theca interna: secrete estrogens
(2) Theca externa, an outer layer of
stromal cells
• Granulosa cells begin to secrete
follicular fluid, which builds up in a
cavity (antrum) in the center of the
secondary follicle.
• The innermost layer of granulosa
cells becomes firmly attached to the
zona pellucida and is now called the
corona radiata.
47

48. Oogenesis (Formation of gametes) contd..
48
• The secondary follicle eventually
becomes larger, turning into a mature
(graafian) follicle
• In this follicle, the primary oocyte (2n)
completes meiosis I, producing two
haploid (n) cells of unequal size—each
with 23 chromosomes.
• The smaller cell produced by meiosis I,
called the first polar body (a packet of
discarded nuclear material).
• The larger cell, known as the secondary
oocyte, receives most of the cytoplasm.
• Once a secondary oocyte is formed, it
begins meiosis II but then stops in
metaphase.
• The mature (graafian) follicle soon
ruptures and releases its secondary
oocyte, a process known as ovulation

49. Oogenesis (Formation of gametes) contd..
• At ovulation, the secondary oocyte is expelled into
the pelvic cavity together with the first polar body
and corona radiata.
• Normally these cells are swept into the uterine tube.
• If fertilization does not occur, the cells degenerate.
• If sperm are present in the uterine tube and one
penetrates the secondary oocyte, however, meiosis
II resumes.
• The secondary oocyte splits into two haploid cells,
again of unequal size.
• The larger cell is the ovum, or mature egg; the
smaller one is the second polar body.
• The nuclei of the sperm cell and the ovum then
unite, forming a diploid zygote.
• If the first polar body undergoes another division
to produce two polar bodies (then the primary
oocyte ultimately gives rise to three haploid polar
bodies, which all degenerate) and a single haploid
ovum.
• Thus, one primary oocyte gives rise to a single
gamete (an ovum).
• By contrast, recall that in males one primary
spermatocyte produces four gametes (sperm).
49

50. The menstrual (sexual) cycle
• A series of events, occurring regularly in females
every 26 to 30 days throughout the childbearing
period of about 36 years.
• It consists of a series of changes that take place
concurrently in the ovaries and uterine walls,
stimulated by changes in the blood concentrations
of hormones.
• Hormones secreted in the cycle are regulated by
negative feedback mechanisms.
• The hypothalamus secretes LHRH which
stimulates the anterior pituitary to secrete FSH and
LH.
• The average length of the menstrual cycle is about
28 days.
• By convention the days of the cycle are numbered
from the beginning of the menstrual phase (about 4
days), proliferative phase (about 10 days), then by
the secretory phase (about 14 days). 50

51. The menstrual (sexual/reproductive) cycle
1.Menstrual phase
▪ When the ovum is not fertilised, the corpus luteum starts to degenerate.
▪ Progesterone (from ovarian follicle) and oestrogen (from corpus luteum) levels
therefore fall, and the functional layer of the endometrium, which is dependent
on high levels of these ovarian hormones, is shed in menstruation.
▪ The menstrual flow consists of the secretions from endometrial glands,
endometrial cells, blood from the broken down capillaries and the unfertilised
ovum.
▪ After degeneration of the corpus luteum, however, falling levels of oestrogen
and progesterone lead to resumed anterior pituitary activity, rising FSH levels
and the initiation of the next cycle.
51

52. 2. Proliferative phase
▪ Again newly secreted FSH helps ovarian follicle to mature and produces
estrogen.
▪ Then oestrogen starts working (develops functional layer of the
endometrium for the reception of a fertilised ovum).
▪ Note: The newly formed endometrium is thick and have an high numbers
of mucus-secreting glands and blood capillaries.
▪ This phase ends when ovulation occurs and oestrogen production declines.
52

53. 3. Secretory phase
• Immediately after ovulation (triggered by LH), ovarian follicle develop to
the corpus luteum (produces progesterone and some oestrogen).
• Now progesterone starts working ie
– Endometrium becomes oedematous
– Secretory glands produce increased amounts of watery mucus.
– This mucus assist the passage of the spermatozoa through the uterus to the uterine tubes
where the ovum is usually fertilised.
– There is a similar increase in the secretion of watery mucus by the glands of the uterine
tubes and by cervical glands which lubricate the vagina.
53

54. Time lines:
▪ The ovum may survive in a fertilisable form for a very short time
after ovulation, probably as little as 8 hours.
▪ The spermatozoa, deposited in the vagina during coitus, may be
capable of fertilising the ovum for only about 24 hours although
they may survive for several days.
▪ This means that the period in each cycle during which fertilisation
can occur is relatively short.
54

55. Symptoms of ovulation:
• Changes in cervical mucus, from thick and dry in
consistency to thin, elastic and watery.
• Small but measurable increase in body temperature.
• Abdominal pain in some women
If the ovum is not fertilized menstruation occurs and a
new cycle begins.
55

56. Fertilization and Pregnancy:
• If the ovum is fertilized (zygote) there is no breakdown of the endometrium
and no menstrual flow.
• Zygote travels from uterine tube to the uterus for fixation in the uterian wall.
• This embeded zygot produces human chorionic gonadotrophin (hCG).
• This hormone keeps the corpus luteum intact, which secrtes progesterone
and oestrogen for the first 3 to 4 months of the pregnancy, inhibiting the
maturation of further ovarian follicles.
• After that, placenta develops and produces oestrogen, progesterone and
gonadotrophins.
56

57. Parturition (Childbirth/Labor).
Three stages of parturition.
1. Dilation
• Starts with the onset of labor. It continues until the cervix is fully dilated.
• This dilation is divided into two phases:
– Latent phase. The cervix is 0 to 4 centimeters (cm) dilated.
– Active phase. The cervix is 4 to 10 cm dilated.
• Latent phase:
It takes about 6 hours (At 1st delivery), 5 hours (At 2nd delivery). For 8 to
12 hours for some women.
• Active phase:
Cervix will dilate at a rate of about 1 cm/hr (At 1st birth) and 1 cm/hr (At
2nd birth)
57
Ref: https://www.healthline.com/health/parturition#complications

58. 2. Expulsion:
• Starts at full dilation and continues until birth.
• This stage also has two phases:
– Passive phase. The baby’s head moves down through the vagina.
– Active phase. The mother feels a need to push, or contract the
abdominal muscles in time with uterine contractions. Lasts about 45
minutes (At 1st birth) and about 30 minutes (At 2nd birth) .
• This ends with the birth of the baby. At this point, the umbilical cord is
clamped, and breastfeeding is often encouraged to help with stage 3.
58
Ref: https://www.healthline.com/health/parturition#complications

59. 3. Placental:
• It starts after birth and ends with the discharge of the
placenta and fetal membrane membranes.
• If the doctor takes an active role — including gently pulling
on the placenta — stage 3 typically takes around 5 minutes.
If the placenta is delivered without assistance, stage 3 can
last around 30 minutes.
59
Ref: https://www.healthline.com/health/parturition#complications
https://www.alamy.com/placenta-and-afterbirth-iage283154922.html

60. References:
• Principles of Anatomy and Physiology by
Tortora Grabowski. Palmetto, GA, U.S.A.
• Ross & Wilson Anatomy and Physiology in
Health and Illness 12th Ed
60

61. Thank You
61