• Dr.
Mariam Al-Awadhi
The • Department of Physiology
• Faculty of Medicine
Reproductive • Maryam.awathi@ku.edu.kw
System • 3rd floor, room 334a
• Lecture ID 30, 31, 32
Objectives
• To understand the function of the reproductive system
• The know the function of different organs and glands of the male and female reproductive systems
• To describe the process gametogenesis (spermatogenesis and oogenesis)
• To describe the hormonal control of the male and female reproductive system (hypothalamus-pituitary-
gonadal axis)
• Explain the menstrual cycles
• To describe the process of fertilization and acrosomal reaction
• To understand the stages of pre-embryonic development
• To know the hormones of pregnancy
• To understand male and female contraceptive methods
• To understand infertility and the assisted reproductive methods
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Sexual
Reproduction
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Functions of the Reproductive System
1. Production of gametes: sperm within testes and eggs within ovaries.
2. Storing and transporting gametes.
3. Fertilization of egg and growth of zygote takes place in female reproductive system.
4. Production of sex hormones.
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Reproduction
• humans at birth are sexually immature.
• Humans undergo a sequence of events until puberty, during which a child becomes a
sexually competent young adult.
• Sexual maturity typically occurs between the ages of 9 - 14 in girls and 11 - 16 in boys.
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Male
Reproductive
System
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Mariam Al-Awadi- Human Reproduction -2019
Vas
Bulbourethral gland
Organ Function
Testes Primary sex organ the produce sperms and sex hormones
Epididymis Sites of maturation (ability to swim and gain resistance against pH
and temperature) and some storage of sperm
Vas deferens Conduct and store sperm
Urethra Conducts sperm (and urine)
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Penis Organ of copulation
The Testes
• Testes are main organs in male reproductive system.
• Develop inside abdominal cavity but descend into scrotal sac during
last 2 months of fetal development.
• Suspended in scortum (important to regulate testicular temperature).
• Undescendent testes (sterility and cancer).
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The Testes (cont.)
• Testes consist of lobules containing:
1. Seminiferous tubules:
Contains cells required for spermatogenesis:
➢ Germinal cells: sperms
➢ Sertoli cells: possess follicle stimulating hormone
(FSH) receptors; they support, nourish and
regulate spermatogenic cells
2. Interstitial tissue:
➢ Leydig cells: They are located in the spaces
between tubules. They possess luteinizing
hormone (LH) receptors ➔ testosterone 9
Spermatogenesis
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Spermatogenesis (cont.)
• Starts at ~11-16 years of age
• Occurs in the seminiferous tubules upon LH & FSH
stimulation
• Takes on average 74 days to complete
• 120 million sperm are produced/day
(~ 60 - 150 million/day)
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Spermatogenesis (cont.)
• Spermiogenesis:
• The last step in spermatogenesis. It results in Spermatogenesis
transformation of spermatids to sperms.
Spermiogenesis
• Mediated by Sertoli cells that are responsible
for eliminating most of the spermatid
cytoplasm to give spermatozoa.
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Sperm (spermatozoa) contain 3 parts:
1. Head: contains a nucleus covered by an acrosome (a specialized lysosome that stores
enzymes to penetrate egg).
1. Middle piece: contains mitochondria wrapped around microtubules of the flagellum
(mitochondria provide energy for movement).
2. Tail: contains microtubules as components of flagellum; its movements propels sperm.
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Control of Male
Sex Hormone
Secretion
Hypothalamic-pituitary-
testes axis
Androgen-binding
Phagocytosis proteins
Luminal fluid
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At the completion of spermatogenesis:
• Spermatozoa will be released into the lumen of seminiferous tubules (non motile), but they move
by bulk movement of fluid secretion.
• In the epididymis, sperms become mature
and gain motility. Sperms also become more
resistance to change in pH and temperature.
• Most of the sperms are then stored in the
vas deferens.
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Mariam Al-Awadi- Human Reproduction -2019
Vas
Gland Function
Seminal vesicles 60% of the semen; thick viscous fluid containing nutrients (fructose) for use by sperm.
Contains prostaglandins that stimulate smooth muscle contraction along male and
female reproductive system
Prostate gland 30% of the semen; secretes alkaline secretion that increase motility of sperm
Prostatic hypertrophy and prostate cancer
Bulbourethral glands Produce clear viscous secretion known as pre-ejaculate that clear the urethra from
urine residues 16
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Mariam Al-Awadi- Human Reproduction -2019
• During ejaculation, the vas deferens (contains sperms) obtains fluid secretions of seminal vesicle
and prostate, and together with the sperms the semen is carried by the ejaculatory duct to the
urethra.
• Semen (seminal fluid) is a thick whitish fluid that contains sperm (5%) and glandular secretions.
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Penis
• Male organ for sexual intercourse
• Three columns of spongy erectile tissue with extensive blood space extend
through the shaft.
• It has a shaft and enlarged tip called gland penis, which is covered by layer
called foreskin. In circumcision the foreskin is removed.
• Circumcised males are 25-35% less likely acquire certain sex transmitted
diseases (eg AIDS).
• It also decreases the incidence of penile cancer and urinary track infection.
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Erection
• Stimuli (physical, psychological, visual)
trigger brain to send nerve signals through
spinal cord autonomic nerves →
relaxation of arterial smooth muscle (by
release of nitric oxide “NO”) → fill the
erectile tissue with blood → compress
compression of veins → penile erection.
• During erection bladder sphincter closes
off so no urine enters the urethra.
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Erection (cont.)
• An erection lasts for a limited time and the penis generally returns to a flaccid state following
ejaculation.
• Erectile dysfunction (impotency):
➢ inability to achieve or maintain erection
➢Its prevalence is estimated to be 26% under the age of 40
➢ Cause by number of factors ie, poor blood flow, some medications, and illnesses
➢ Management: treat the underlying cause.
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Ejaculation
1. The first phase of ejaculation is emission:
Sexual stimuli trigger brain → send nerve signals through spinal cord to the muscular wall of:
• Epididymis, vas deferens to empty sperm.
• Reproductive glands (seminal vesicles, prostate, and bulbourethral glands) to release secretion.
resulting in movement of sperm from the vas deference to the urethra.
2. The second phase of ejaculation is expulsion:
It is the movement of sperm from the urethra to the exterior
• Gland secretions stimulate rhythmical contractions of muscles at the base of the penis and within the
urethral wall expel the semen in spurts.
• During ejaculation, urinary bladder sphincter closes, so that no semen can enter the bladder.
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Ejaculation
Ejaculation results in the expulsion of semen (achieved at the peak of sexual arousal):
• 2-5 ml of semen that contains ~300 million sperms
• Life of sperm in female genital tract is ~ 24 - 72 hrs
• ~100- 200 reach the egg
• Only one sperm enters an egg
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• It is the main sex hormone in males.
Functions of • Important for development and function of male reproductive
glands and organs.
Testosterone • Essential for the maturation of sperm.
• Essential for development of male secondary sex characteristics:
• Oil and sweat glands secretion leading to acne and body odor
• Enlargement of larynx and vocal cords; deepening of voice
• Development of hair on face, chest and back
• Tallness, longer legs, broad shoulders
Male pattern hair loss
• Greater muscle strength (athletes, anabolic steroids)
• Sex drive and aggressiveness
• Triggers baldness if appropriate genes are present
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Female
Reproductive
System
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Female Reproductive System
Organ Function
Ovaries Primary sex organ that produce egg each month and sex hormones.
Oviducts (fallopian tubes) Conduct egg; site of fertilization.
Uterus (womb) Houses developing embryo and fetus. Consists of endometrium,
myometrium perimetrium. Cervical cancer.
Vagina Receives penis during copulation, serves as birth canal and exit for
menstrual flow. 25
Oogenesis
• Mitosis of primary oogonia occurs during fetal life until midgestation (peak of 7 million oocytes) and
then ceases.
• Primary oocyte begins first meiotic division in utero: meiosis I is arrested in prophase until the time of
ovulation.
Fetal life Puberty – before ovulation Fertilization
Arrest in meiosis I Arrest in meiosis II Completion of Meiosis II
Ovarian Reserve
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Oogenesis (cont.)
• Then there is progressive loss of oocytes & by puberty there are approximately 400,000 oocytes (only
~400 follicles ovulate in women).
• At the time of ovulation, the primary oocyte completes the first meiotic division producing the first polar
body and a secondary oocyte. It arrests in metaphase of 2nd meiotic division.
Fetal life Puberty – before ovulation Fertilization
Arrest in meiosis I Arrest in meiosis II Completion of Meiosis II
Ovarian Reserve
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Oogenesis (cont.)
• Sperm penetration (fertilization) causes completion of 2nd meiotic division and the expulsion of a
second polar body.
Fetal life Puberty – before ovulation Fertilization
Arrest in meiosis I Arrest in meiosis II Completion of Meiosis II
Ovarian Reserve
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Ovarian Cycle
primary
Meiosis I → Meiosis II
FSH dependent Lasts for years
70-85 days 48 hrs
1. Follicular Phase
2. Ovulation
LH dependent
3. Luteal Phase
• Follicles are made up of the oocyte, and follicular cells.
• Follicular cells differentiate to granulosa and thecal cells that produce female sex hormones and fluid.
• Changes in the ovary are the result of changing levels of FSH and LH from the anterior pituitary. 30
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Control of Ovarian Steroidogenesis
CNS
( - )
Hypothalamic-pituitary-ovarian axis Hypothalamus
GnRH GnRH
-
FSH LH
Anterior Pituitary
Granulosa Thecal cell
cell
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❖ Ovarian cycle:
• Follicular phase.
• Ovulation.
Menstrual • Luteal phase.
Cycle ❖ Endometrial cycle:
• Proliferative phase.
• Secretory phase.
• Menstruation.
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Ovulation
Anterior Pituitary
• 28 day vs longer cycles
• Peak E, LH, ovulation
• Trophic hormones
• Functional, basal layers
• Body temperature increase.
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Ovulation
3. Hypothalamus GnRH
secretion
7. E positive feedback on LH
→ LH surge → ovulation
9. High P, E and inhibin → -ve feedback on FSH
and less on LH
4. Pituitary secretion of FSH 8. LH stimulate CL
11. CL regression
produces E, P & inhibin
1. CL dies, E & P levels fall
5. FSH recruit follicles
which secrete E.
10. P → uterine gland development
6. E → endometrial growth
2. Menses 34
• 1. Follicular Phase
• Lasts from day 1 to about day 13 of the cycle (assuming that
the cycle is 28 days) during which:
• FSH ➔ growth and maturation of follicles (only ONE will
become mature).
Ovarian cycle • Granulosa and thecal cells secrete estradiol (peaks at ~
day 12; 2 days before ovulation).
• Granulosa cells are stimulated by FSH; thecal cells are
stimulated by LH.
• The rapid increase in estradiol secretion ➔ positive
feedback effect ➔ rapid LH secretion ➔ LH SURGE.
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2. Ovulation: A woman usually ovulates only one ovum a month.
• LH SURGE:
• Completion of meiosis I.
• Rupture Graafian follicle wall (day 14) ➔ OVULATION ➔
expulsion of secondary oocyte (with the 1st polar body) out of
Ovarian cycle the ovaries into fallopian tube.
• If ova is fertilized by a sperm ➔ ova completes the second
meiotic division ➔ formation of 2nd polar body.
(cont.)
• 3. Luteal Phase
• After ovulation ➔ LH stimulates empty follicle (corpus luteum) to
secrete estradiol & progesterone (and inhibin which inhibits FSH
only) ➔ negative feedback inhibition of FSH and LH ➔ prevents
the development of a new follicle
• Regression of corpus luteum (life span 14±2) ➔ decrease in
estrogen and progesterone ➔ MENSTRUATION.
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1. Proliferative Phase
• Occurs during ovarian follicular phase.
• An increase in estradiol stimulates the growth (proliferation)
of stratum functionale of the endometrium.
2. Secretory Phase
• Occurs during ovarian luteal phase.
Endometrial • An increase in progesterone ➔ stimulates development of
uterine glands.
• Effects of increased estradiol and progesterone levels:
Cycle • endometrium becomes thick, vascular and spongy in
appearance.
• The uterine glands become engorged with glycogen,
lipids & proteins.
• endometrium ready to accept and nourish an embryo.
3. Menstruation
• Resulting from a decrease in estradiol and progesterone
levels during late luteal phase.
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Menstruation
• Process of menstruation:
- Arteries that supply the lining of uterus restrict and capillaries are weakened.
- Damaged vessels detach layers of uterine lining: blood, mucus, and degenerative tissue descend from
uterus.
• Menarche: first menstrual period, usually starts at 11-14 years.
• Amenorrhea: menarche did not occur by age of 16, or uterine cycle was
interrupted for more than 6 months without pregnancy.
- Causes: non-functional ovaries, developmental abnormalities, weight loss or
excessive exercise.
• Menopause is cessation of menstrual cycle because ovaries are no more
functioning. Occurs between 45-55 years. 38
Mariam Al-Awadi- Human Reproduction -2019
Functions of Estrogen & Progesterone
• Estrogen is essential for normal development and function of female reproductive organs
(ovaries, uterus.. etc).
• Estrogen is responsible for development and maintenance of female secondary sexual
characteristics:
• Less body and facial hair.
• More fat beneath the skin to give a rounded appearance.
• Enlargement of pelvic girdle and cavity to give wider hips.
• Both estrogen and progesterone:
• Required for breast development.
• Help maintain endometrium during pregnancy.
• Help suppress gonadotropin (LH and FSH) secretion.
• Inhibit prolactin secretion.
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• The main function of male and female reproductive
Fertilization system is to produce gametes.
and Pregnancy • Fertilization is the union of sperm and egg to form a
zygote, the first cell of new individual.
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Fertilization
• During the act of sexual intercourse, the male ejaculates ~ 300 million sperms into the female
vagina and ONLY ~100-200 sperms survive to enter fallopian tube. Remain viable up to 3 days.
• When does fertilization occur?
• Ovulated oocyte in the fallopian tube lasts12~
24 hrs following ovulation.
• It occurs if intercourse takes place within 3-5
days prior to the day of ovulation.
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Acrosomal Reaction
• Several sperms penetrate corona
radiata. and attempt to penetrate
• Sperms binding to zona pellucida
(glycoprotein layer surrounding the
oocyte) → acrosome burst → release of
digestive enzymes → sperms
penetration of zona pellucida reaching
the oocyte cell membrane
• Sperm plasma membrane fuse with
oocyte membrane and sperm nucleus
enters the cytoplasm
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Acrosomal Reaction (cont.)
• When sperm nucleus enter oocyte:
➢ Cortical granules fuse with cell membrane
and release their content → formation of
fertilization envelope that prevent other
sperms from entering the oocyte (prevent
polyspermy).
➢ The zona pellucida is now called the
fertilization envelope.
➢ Completion of meiosis II
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Process of
Development
• 1. Cleavage:
• Mitotic division of zygote.
• 2. Growth:
• Increase in size of the divided cells.
• 3. Morphogenesis:
• Shaping of the embryo through cell
migration.
• 4. Differentiation:
• Cells take specific structure and function.
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Process of Development
1 2 3
• Embryonic Period:
The period of system formation(organogenesis).
• Fetal Period:
Growth and development.
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Pre-embryonic
Development
• Cleavage:
• Occurs as the zygote goes down the fallopian tube giving
a morula.
• First cleavage division is completed ~ 30 hrs after
fertilization.
• Zygote divides by mitosis to double the number of cells
(2 cells, 4 cells, 8 cells, etc).
• The zygote reaches morula stage after 3-4 days (enters
uterus).
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Pre-embryonic
Development (cont.)
• Blastocyte:
• Early embryonic structure, consists of:
• An inner cell mass:
• develops into fetus and some extraembryonic
membrane (amnion that secretes amniotic
fluid).
• Chorion (trophoblast cells):
• will become part of placenta.
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Pre-embryonic
Development (cont.)
• Implantation:
• Trophoblast cells of blastocyst attach to uterine wall (5-6
days).
• Blastocyst implantation in the endometrium starts on 6th
day and completes by 10th-12th day.
• Blastocyst secreted enzymes that invades the uterine
endometrium and endometrial grows around the
blastocyst until it is completely engulfed.
• Hormone human chorionic gonadotrophin (hCG) is now
secreted from implanted blastocyst.
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Pregnancy
Hormones
• Human chorionic gonadotropin (hCG):
• Secreted from trophoblast cells of the implanted blastocyst.
• Becomes detectable in the mother's blood and urine between 6 and
14 days after fertilization
(3 - 4 weeks gestational age) - pregnancy test.
• Causes corpus luteum viability and hormonal secretion until placenta
takes over ~ 3-4 months of gestation (luteal-placental shift).
• Estrogen and progesterone:
• Important to support the endometrium.
• Inhibit the contraction of uterine muscle. 49
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Mariam Al-Awadi- Human Reproduction -2019
Male vs. Female Reproductive Systems
Male Reproductive System Female Reproductive System
• Gonads (testes) resides outside of the • Gonads (ovaries) resides in the abdominal
abdominal cavity. cavity.
• Release of gametes (sperm) is • Release of gamete (egg) occurs once per
continuous. month.
• Gametic reserve is replenished through out
life. • Gametic reserve is limited in number.
• Testosterone exhibits negative feedback on • Estrogen exerts both negative and positive
LH and FSH. feedback on LH and FSH.
• Activity of female tract is rhythmic monthly or
• Activity of male tract does not show rhythm.
on the length of pregnancy.
• Male tract serves only sperm transport, • Female tract serves sperm and egg transport,
store and maturation. store, maturation, fertilization, placentation,
gestation and delivery.
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• Barrier method: condom (failure rate 2% - 12%).
Male • Coitus interruptus: withdrawal of penis before ejaculation
Contraception (failure rate 20% - 30%).
• Vasectomy: surgical procedure where the
Vas deferens are tied or disconnected
(failure rate 0%).
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Female
Contraception
• Contraceptive pill:
Combination of synthetic estrogens & progestins causes negative feedback on GnRH & therefore
ovulation doesn’t occur (false luteal phase; failure rate < 1%).
• Female diaphragm:
Similar to male condom (barrier method, failure rate 20%).
• Intrauterine device (IUD):
Also known as the loop; failure rate < 2%.
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Female
Contraception (cont.)
• Temperature method: (BETTER FOR FERTILIZATION)
Temperature on day of ovulation increases by ~0.5˚C (due to
progesterone secretion, failure rate 4%).
• Rhythm method: 53
Avoid intercourse near the time of ovulation; menstrual cycle
must be regular; (failure rate 20% - 30%).
•Sterilization/ tubal ligation:
Fallopian tubes are ligated (failure rate 0%).
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Infertility
• Failure of couples to achieve pregnancy after couple of years.
• Estimated prevalence is 15% of couples are infertile.
• Causes are evenly distributed between males and females:
• Males the main cause is low sperm count and/or large proportion of abnormal sperm, caused
by environmental influence.
• Females the main cause is overweight.
• Treatment:
• Underlying cause.
• Female fertility drug that stimulate ovulation.
• Assisted reproductive technologies.
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Assisted Reproductive Technologies
• Artificial insemination by donor
• Sperm is placed in the vagina by a physician.
• Good if the partner has low sperm count because the sperm can be collected
over time and concentrated so that sperm count is sufficient for fertilization.
• In vitro Fertilization (IVF)
• Administration of fertility drug to immature egg in the lab → mature egg.
• Concentrated sperm is incubated with the egg in the lab.
• Embryos are transferred to the uterus.
• Gamete Intrafallopian Transfer (GIFT)
• Eggs are removed and reintroduced at the same time in fallopian tube along with sperm.
• Performed only if fallopian tubes are intact and sperms are normal.
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