The Biology

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The Biology
of Human
Reproduction
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MALE BIOLOGY
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Primary organs paired testes
Secondary organs penis, scrotum, epididymis, vas
deferens, urethra three secretory glands
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anatomy of the male reproductive system
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?
seminiferous tubules
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Developmental stages of the sperm in the
seminiferous tubule are shown here. Seminiferous
tubules are lined with sperm-forming cells
(spermatogonia) in various stages of development.
Through the process of meiosis, these cells form
haploid cells called "spermatids". At the final
stage of sperm maturation, the head and the tail
sections of the sperm are formed.
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SPERM PRODUCTION A single testis can
produce up to 1.5 ? 108 sperm cells daily
The epididymi can store sperm cells for up to 14
days
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Penile tissues
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Upon stimulation, these tissues fill with
blood, causing them to become enlarged this
swelling closes off draining veins, causing
penile erection
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the ejaculatory route
Fully-formed sperm leave the seminiferous tubules
to enter the epididymus where they remain stored
until ejaculation. Certain secretions are
released in the epididymus that alter the sperms
environment and its surface characteristics.
During the process of ejaculation, the sperm
follow the route indicated by the red arrows.
Involuntary smooth muscle contractions force
sperm cells out of the epididymi and into the
vasa deferentia. The sperm move along each vas
deferens. As the sperm move along the vas
deferens materials are added to the sperm and to
the extracellular fluid that surrounds them,
forming semen. The prostate gland and seminal
vesicles add fluid and nutrients at the time of
sperm ejaculation, providing most of the volume
of the semen to be ejaculated. This complex of
fluid and sperm cells travels up the urethra and
is released forcefully from the penile meatus
(last red arrow).
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EJACULATORY SEQUENCE



1. Stimulation causes
sexual arousal penis becomes erect.
2. Smooth muscle contractions
eject sperm from epididymi into vasa

deferentia.
3. High fructose secretions from seminal
vesicles added as vasa deferentia empty into
ejaculatory ducts. 4. Ejaculatory ducts pass
into prostate gland and empty into
prostatic urethra prostatic secretions are
added. 5. Urethra exits prostate and passes near
Cowpers gland, which adds its secretions.
6. Urethra enters penis. 7. Semen is ejaculated
forcefully out of penis.
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Total volume of ejaculate 2-3
ml. Contains 50-150 ? 106 sperm cells
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Semen is a complex combination of fructose,
phosphorylcholine, ergothioneine, ascorbic acid,
flavins, prostaglandins, citric acid,
cholesterol, zinc, acid phosphatase, lactic acid,
fibrinolytic and proteolytic enzymes,
hyaluronidase and sperm.
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sperm cell anatomy ?
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FEMALE BIOLOGY
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Primary organs paired ovaries (they are
approximately the size and shape of an almond)
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Secondary organs fallopian tubes, uterus vulva,
vaginal duct
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Vulva (external genitalia)
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female anatomy of reproduction
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Cross-section through an ovary
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structure of the uterus
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If, after ovulation, no embryo arrives in
the uterus for implantation, most of
the endometrium is shed in MENSTRUATION
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MENSTRUATION involves endometrial breakdown
and shedding
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start of a new cycle
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The female monthly cycle
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Hormone levels in the blood control the
female monthly cycle
http//www.sumanasinc.com/webcontent/anisamples/ma
jorsbiology/ovarianuterine.html
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A closer look at follicle development in
the OVARY
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The maturation of ovarian follicles
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females have 2 million follicles at birth but
only 40,000 remain by menarche
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A woman will ovulate approximately 400 secondary
oocytes during her reproductive lifetime
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The oocyte is the largest of all human cells
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? Fertilization usually occurs in the ampulla of
the tube it MUST occur w/in 24 hours
of ovulation
After ejaculation, sperm take about 15-45 minutes
to swim through the cervix, uterus, and fallopian
tube to reach the oocyte
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The zygote starts dividing, and continues to
divide as it travels down the tube toward the
uterus. Seven days later, the young embryo
arrives in the uterus and becomes implantated in
the endometrial wall
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From a single diploid cell, the zygote, the
wondrous process of human development unfolds....
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View your early days.......
http//embryo.soad.umich.edu/resources/morph.mov
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It is but one of the manifestations of the
limitless creative power of God.
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