Human Reproduction and
Development
 Anatomy of the Male and Female
Reproductive Systems
 Gamete Formation
 Hormonal Control of Reproduction
 Conception, Pregnancy,
Development, Birth
Male Anatomy
• External genitalia
– Penis and Scrotum
• Internal Reproductive Organs
– Pair of gonads
• Produce gametes (sperm cells)
• Produce hormones
– Accessory glands
• Secret products essential to sperm
movement
– Set of ducts
• Carry sperm and glandular secretions.
Male Anatomy
• Penis
– Composed of 3 cylinders of spongy tissue.
– During sexual arousal, tissue fills with blood
from the arteries
• The increasing pressure seals off the veins that
drain the penis
– Result = penis engorges with blood = erection
– The tip (Glans) is covered by a fold of skin
called the foreskin, which may be removed by
circumcision
• A tradition with religious roots.
• No verifiable health or hygienic advantage.
Male Anatomy
• Scrotum
– Sac which contains testes
– Regulates temperature of testes by
contraction of cremaster muscle.
• Cold = contracts
– Brings testes close to body to warm up.
• Warm = relaxes
• Goal = keep testes 3o below normal body
temperature.
Male Anatomy
• Testes
– Stored in scrotum
• Before birth, testes develop in the abdomen and then migrate
down a canal into scrotum around the time of birth.
– Sperm producing organ
• Made in tightly coiled tubes called seminiferous tubules
inside testes
• Sperm produced is not fully mature when it leaves testis (not
motile yet)
– Source of male hormone testosterone
• Made by interstitial cells scattered between the seminiferous
tubules
– Deposits sperm into epididymis
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Male Anatomy
• Epididymis
– Coiled tubes
– About 6 meters long!!
– Posterior to the testis
– Stores sperm
– Site of further sperm maturation
• Gains motility
– Contracts during ejaculation, expelling sperm
into vas deferens
– Sperm can be store here for months
• If not ejaculated, will eventually be phagocytized
Male Anatomy
• Vas Deferens
– Muscular tubes that carry sperm from
epididymis to ejaculatory duct (and eventually
the urethra)
• peristalsis
– Urethra drains both the excretory system and
the reproductive system
• Not the case in females
Male Anatomy
• Ejaculatory Duct
– Connects seminal vesicle to urethra
– Passes through prostate gland
Male Anatomy
• Seminal Vesicle
– Lies below and behind bladder
– Secretes thick, clear fluid into ejaculatory duct
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•
•
60% volume of semen (the fluid that is ejaculated)
Alkaline – to neutralize acidic pH of vagina
Fructose – used for energy by sperm
Prostaglandins – chemical messengers which,
once in female, stimulate uterine peristalsis to help
move semen up the uterus
• Proteins – cause semen to coagulate after it is
deposited in the female, making it easier for the
uterine contractions to move the semen
Male Anatomy
• Prostate Gland
– Doughnut shaped gland which surrounds
urethra
– Secretes thin milky fluid into urethra
• 20% of seminal volume
• Liquefy the semen – prevents sperm from
clumping together
• Alkaline – continues to neutralize acid from
residual urine in urethra and natural acidity of
vagina
Male Anatomy
• Cowper’s Gland (Bulbourethral Gland)
– Pair of small glands along urethra, below the
prostate
– Secrete viscous fluid before emission of
sperm & semen
• Thought to lubricate penis and vagina
– Released before ejaculation
• Fluid does contain some sperm
• One factor in the high failure rate of the
“withdrawal method” of birth control.
Male Anatomy
• Vasectomy
– Incision through scrotum
– Cut and tie off vas deferens
– Sperm is still produced but can’t get out
– Phagocytized
Male Anatomy Review
•
Passageway from testes to
outside
1. Multiple seminiferous tubules
•
site of spermatogenesis
2. Single tubed epididymis
3. Vas deferens
4. Seminal vesicle
5. Ejaculatory duct
6. Urethra
Fun Facts
•
For Your Information
– Volume of ejaculation = 2.75 ml
– pH = 7.2 – 7.6
– 50 – 150 million sperm per ml.
– Only a few sperm reach the egg
– Average sperm count has decreased from 113
million/ml to 66 million/ml in past 40 years.
– Infertility = <20 million/ml
• Factors leading to infertility are environmental
toxins, estrogens in meat, radiation, pesticides,
marijuana, alcohol
Labelling Diagram
1.
2.
3.
4.
5.
6.
7.
Pubic Bone
Seminal Vesicles
Rectum
Prostate Gland
Cowper’s Gland
Anus
Vas Deferens
(sperm duct)
8. Epididymis
9. Testes
10.Urethra
11.Penis
12.Scrotum
13.Head of Penis
(Glans)
14.Foreskin
15.Bladder
Hormonal Control
• Male Reproductive System Control
– Testosterone
• Primary Function
– Stimulate spermatogenesis
• Secondary Function
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Maturation of testes and penis
Sex drive
Facial hair
Body hair
Deeper voice
Increased muscle strength
Body oil secretion -- acne
Hormonal Control
•
Hypothalamus releases
1. Gonadotropin-Releasing Hormone (GnRH)
• Stimulates pituitary to release LH & FSH
•
Pituitary releases
1. Follicle-Stimulating Hormone (FSH)
• Stimulates spermatogenesis by seminiferous
tubules
2. Luteinizing hormone (LH)
• Stimulates testosterone production by interstitial
cells
• Indirectly stimulates spermatogenesis because
testosterone is required for sperm production.
Hormonal Control
• LH, FSH, and GnRH concentrations in the
blood are controlled by negative feedback
systems
Testosterone production
Spermatogenesis
Testosterone production
Spermatogenesis
Hormonal Control
Hormonal Control
Female Anatomy
• External genitalia
- Two sets of labia that surround the clitoris
and vaginal opening
• Internal Reproductive Organs
- A pair of gonads (ovaries)
- A system of ducts and chambers to
- Conduct the gametes
- House the embryo and fetus
Internal Organs
Internal Organs
Female Anatomy
• Ovaries
– Lie in abdomen, below most of the
digestive system
– Enclosed in a tough protective capsule
– Produces eggs (follicles)
– Produces female sex hormones
1. Estrogen
2. Progesterone
Female Anatomy
Female Anatomy
•
Follicles
– Consists of one egg cell surrounded by
layers of follicle cells.
•
Nourish and protect the developing egg cell
– All of the 400,000 follicles a woman will ever
have are present at birth.
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•
Only a few hundred will be released during a
woman’s reproductive years
One (very rarely 2 or more) follicle matures and
releases its egg during each menstrual cycle
Female Anatomy
•
Follicles
– Follicle cells release the primary female sex
hormone… estrogen.
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Secondary sex characteristics, wider hips, more body fat,
Necessary for breast development
– At ovulation, the egg “explodes” out of the
follicle leaving behind the follicular tissue
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This grows into a solid mass called a Corpus Luteum
– Secretes progesterone (necessary for pregnancy)
If fertilization does not occur, the corpus luteum
disintegrates and a new follicle matures the next month.
Female Anatomy
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Oviduct
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Fallopian tube
Conducts eggs to the uterus
Fertilization occurs here
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If embryo grows here = ectopic pregnancy
The ovary and oviduct don’t actually touch.
The egg is released into the abdominal cavity and is
“sucked” into the oviduct.
• Oviduct has fingers called “fimbrae” and hairs
called “cilia” that vibrate and sweep the egg into
the tube by swishing body fluids towards itself
• These cilia also help move the egg towards the
uterus
Female Anatomy
Female Anatomy
•
Uterus (womb)
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Houses and nurtures the developing fetus
Oviducts enter at the top
Cervix (opening) at the bottom
The lining is called the endometrium
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Richly supplied with blood vessels
Varies in thickness depending on the stage of the
menstrual cycle
Controlled by hormones
2 Layers
– Basal layer = stable, does not change thickness
– Functional layer = changes thickness with menstruation
Female Anatomy
Female Anatomy
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Vagina
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Birth canal
Average = 7.5 cm in length
pH = 4-5
Upper end closes at cervix
Receives penis during sexual intercourse
Elastic to facilitate sexual intercourse and
birth
Female Anatomy
Gametogenesis
1.
2.
3.
4.
The walls of the seminiferous
tubules consist of diploid
spermatogonia, stem cells
that are the precursors of
sperm.
divide by mitosis to produce
more spermatogonia
The Meiosis of each
spermatocyte produces 4
haploid spermatids.
These then differentiate into
sperm, losing most of their
cytoplasm and gaining
motility in the process.
In epididymis
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Sperm nourished by sertoli
cells (in seminiferous tubules)
Whole process takes 70 days
Gametogenesis
1.
2.
3.
4.
5.
6.
Takes place in ovaries
Primary Oogonium develop
into oocytes before birth
Oocytes complete maturation
one at a time & once a month
during reproductive years
Primary oocyte grows larger
and begins meiosis
Forms a secondary oocyte
and first polar body
After fertilization, secondary
oocyte completes meiosis and
become 1 egg and second
polar body.
Hormonal Control
•Hypothalamus - produces releasing GnRH
•Anterior Pituitary – secrete gonadotropic hormones.
–FSH - follicle stimulating hormone.
–LH - luteinizing hormone.
•Ovaries - secrete the female sex hormones.
–Estrogen –thickening of uterine lining
–Progesterone – matures/maintains uterine lining
Hormonal Control
• FSH is released from AP
–Start the ripening of ovum within follicle
• Estrogen is produced by follicle
–Development of endometrium for possible
pregnancy
–Feedback to hypothalamus to inhibit FSH
and release LH
Hormonal Control
• LH surge on day 14
–Stimulates ovulation
–Conversion of follicle into corpus
luteum
• Progesterone production
– Continued development of
endometrium
– Feedback to inhibit release of LH
Hormonal Control
•If no fertilization
– Degeneration of corpus luteum
– Drop in hormone level
The 4 Phases of Menstruation
Female Anatomy
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Menstruation
1. Flow Phase (Menstrual Phase)
– Start of bleeding marks Day 1 of
phase
– Shedding of the endometrium
(uterine lining)
– Average = 4-5 days
• Sometimes up to 8 days
– Occurs due to low hormone levels
Female Anatomy
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1
Menstruation
2. Follicular Phase
– Occurs during day 6-13
– Period of repair and thickening of
endometrium.
Female Anatomy
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Menstruation
2. Follicular Phase
– Occurs during day 6-13
– Period of repair and thickening of
endometrium.
– FSH from the pituitary promotes follicle
development in the ovary.
Female Anatomy
• sdfsdfsdf
Menstruation
2. Follicular Phase
– Occurs during day 6-13
– Period of repair and thickening of endometrium.
WHY??
– FSH from the pituitary promotes follicle development
in the ovary.
– As follicle develops it produces estrogen,
• thickening of the uterine lining
• LH production increase
• FSH production decrease
Menstruation
FSH
Decrease
Menstruation
3. Ovulation Phase
– LH causes ovulation to occur on
day 14.
• Secondary oocyte is released
from the follicle/ovary.
Female Anatomy
• sdfsdfsdf
Menstruation
4. Luteal Phase
– Final preparation of endometrium to
receive the fertilized ovum
– LH stimulates development of the
Corpus Luteum.
• causes progesterone levels to
increase.
Menstruation
Menstruation
4. Luteal Phase
– Final preparation of endometrium to receive
the fertilized ovum
– LH stimulates development of the Corpus
Luteum.
• causes progesterone levels to increase.
– Estrogen and progesterone inhibit GnRH,
thereby decreasing LH and FSH levels.
– This low level of hormones initiates the flow
phase.
Menstruation
Menstruation
Menstruation
Menopause
• The end of a woman’s reproductive years
• Between ages of 45 – 55
• Ovaries no longer respond to FSH & LH from AP
– Ovaries do not produce estrogen or
progesterone
• Marked by circulatory irregularities (hot flashes),
dizziness, insomnia, sleepiness, depression
• Hormone replacement therapy may help.
Review Video
• Crash Course