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Learning Outcomes
Text Pages
P1
P. 416-417
Identify and give functions for each of the
following:
testes (seminiferous tubules and interstitial cells),
epididymis, ductus (vas) deferens, prostate gland,
cowper's gland, seminal vesicles, penis.
P2
Demonstrate a knowledge of the path of sperm
from the seminiferous tubules to the urethral
opening.
P. 414-415
P3
List the functions of seminal fluid.
P. 414-415
P4
Identify the tail, midpiece, head, and acrosome of
a mature sperm and state their functions.
P. 416-417
P5
Describe the functions of testosterone.
P. 417
P6
Demonstrate a knowledge of the control of
testosterone levels the endocrine system.
P. 417
_____ Birth canal
_____ Buffer
_____ Bulbourethral gland
_____ Cervix
_____ Clitoris
_____ Copulation
_____ Corpus luteum
_____ Cowper’s glands
_____ Ductus (vas) deferens
_____ Ejaculation
_____ Endometrium
_____ Epididymus
_____ Erectile tissue
_____ Estrogen
_____ External genitalia
_____ Fimbria
_____ Follicles
_____ Follicular phase
_____ FSH
____ GnRH
____ Gonads
_____ HCG
_____ Implantation
_____ Interstitial cells
_____ Labia
_____ Leutenizing hormone
_____ Luteal phase
_____ Menopause
_____ Menstrual phase
_____ Menstruation (menses)
_____ Oogenesis
_____ Ova
_____ Ovaries
_____ Oviduct
_____ Ovarian cycle
_____ Ovulation
_____ Oxytocin
_____ Pap smear
_____ Penis
_____ Placenta
_____ Pregnancy
_____ Progesterone
_____ Proliferative phase
_____ Prostate gland
_____ Puberty
_____ Scrotum
_____ Secretory phase
_____ Semen
_____ Seminal fluid
_____ Seminal vesicles
_____ Seminiferous tubules
_____ Spermatogenesis
_____ Spermatogonia
_____ Spermatozoa (sperm)
_____ Testes
_____ Testosterone
_____ Urethra
_____ Uterine cycle
_____ Uterus
_____ Vagina
_____ Vulva
_____ Womb
Fertility facts. The largest cell in the human body is the female egg and
the smallest is the male sperm. While you can’t see skin cells or muscle
cells, the ovum is typically large enough to be seen with the naked eye
with a diameter of about a millimeter. The sperm cell, on the other hand, is
tiny, consisting of little more than nucleus.
Dreams of pregnant women. The three things pregnant women dream
most of during their first trimester are frogs, worms and potted plants.
Many women also dream of water, and giving birth.
Teething in the womb. Your teeth start growing 6 months before you are
born. While some babies are born with teeth in place, the tooth buds that
will eventually become teeth in young children (during their 1st year of life)
are formed at 9 to 12 weeks in utero.
All the blue-eyed babies. Babies are always born with blue eyes. The
color of your eyes depends on the genes you get from your parents, but at
birth most babies appear to have blue eyes. The reason behind this is the
pigment melanin. The melanin in a newborn’s eyes often needs time after
birth to be fully deposited or to be darkened by exposure to ultraviolet
light, later revealing the baby’s true eye color.
All the strong babies. Babies are, pound for pound, stronger than an ox.
While a baby certainly couldn’t pull a covered wagon at its present size, if
the child were the size of an oxen it just might very well be able to. Babies
have especially strong and powerful legs for such tiny creatures, so watch
out for those kicks.
Infants with teeth. One out of every 2,000 newborn infants has a tooth
when they are born. Nursing mothers may cringe at this fact. Sometimes
the tooth is a regular baby tooth that has already erupted and sometimes
it is an extra tooth that will fall out before the other set of choppers comes
in.
A fetus with fingerprints. A fetus acquires fingerprints at the age of three
months. At only 6-13 weeks of development, the whorls of what will be
fingerprints have already developed. Oddly enough, those fingerprints will
not change throughout the person’s life and will be one of the last things to
disappear after death.
Single-celled people. Every human spent about half an hour as a single
cell. All life has to begin somewhere, and even the largest humans spent a
short part of their lives as a single celled organism when sperm and egg
cells first combine. Shortly afterward, the cells begin rapidly dividing and
begin forming the components of a tiny embryo.
The goal of the reproductive system is to pass on your
genetic code onto a new and unique generation. This is
ultimately accomplished via fertilization.
Terms you
should know:
1.
2.
3.
4.
5.
Haploid
Diploid
Zygote
Gamete
Gonad
Label these on
the diagram
Human reproduction employs internal fertilization, and
depends on the integrated action of hormones, the nervous
system, and the reproductive system.
Male gonads are the testes, which
produce sperm and testosterone.
estrogen
Female gonads are the ovaries which
produce eggs and 2 hormones:
estrogen and progesterone.
http://www.youtube.com/watch?v=WEzcK-OKd10
Male Anatomy
The male external genitalia are the scrotum and penis.
The scrotum is a fold of skin that encloses the male gonads
(testes)
The testes are a pair of tightly coiled tubes surrounded by
several layers of connective tissues.
These tubes are the SEMINIFEROUS TUBULES, where
sperm are produced by meiosis.
About 250 meters of tubules are packed into each testis.
The INTERSTITIAL CELLS are scattered between the
seminiferous tubules in the testes.
These cells produce testosterone.
Sperm production cannot occur at normal body
temperature.
So just before birth, the testes descend to hang outside
the abdominal cavity in the scrotum, a fold of skin.
The temperature in the scrotum is ~2oC below body
temperature.
SPERMATOGENESIS
This, the production of
mature sperm cells, is a
continuous and prolific
process in the adult male.
Spermatogenesis occurs in
the seminiferous tubules of
the testes.
The spermatogonia undergo
repeated mitoses to produce
large numbers of potential
sperm or spermatocytes
(approximately 3
million/day).
SPERMATOGENESIS
Next, Meiosis occurs to
create 4 haploid
spermatids.
The sertoli cells transfer
nutrients to the spermatids,
and the developing sperm are
gradually pushed toward the
center of the seminiferous
tubule and make their way to
the epidymis.
When the spermatids reach
the epidymis, they acquire
motility (mature), and are
stored.
SPERMATOGENESIS
The process from spermatogonia to motile sperm, takes
65-75 days in the human male.
Each ejaculation of a human male contains about 400
million sperm cells.
Sperm production begins at
puberty and continues
throughout life, with several
hundred million sperm being
produced each day.
SPERM CELLS
The structure of a sperm cell fits its
function.
The thick head contains the haploid
nucleus and is tipped with a special body,
the acrosome. The acrosome contains
enzymes that help the sperm penetrate
the egg.
The neck contains large numbers of
mitochondria that provide ATP for
movement.
The tail is a flagellum which moves the
sperm.
During ejaculation, the sperm are
propelled from the epididymis
through the muscular VAS
DEFERENS ducts, which run from
the scrotum around and behind the
bladder, where they join to form a
short EJACULATORY DUCT.
This duct opens into the URETHRA,
the tube which drains both the
excretory and reproductive systems
(never both at the same time).
The urethra runs through the penis
and opens to the outside at the tip of
the penis.
In addition to the testes and ducts, the male reproductive system contains
three sets of glands that add their secretions to the SEMEN (the fluid
ejaculated).
1. SEMINAL VESICLES: contribute about 60% of the total
volume of semen. This pair of glands lies below and
behind the bladder and empties into the ejaculatory duct.
The fluid is thick and clear and contains mucous,
amino acids, and large amount of fructose (which
provides energy for the sperm).
These vesicles also secrete PROSTAGLANDINS, which once in the
female reproductive tract, stimulate contractions of the uterine muscles
that help move the semen up into the uterus.
Proteins in the seminal fluid cause the semen to coagulate after it is
deposited in the female, thus, making it easier for uterine contractions to
move the semen.
2. PROSTATE GLAND:
This is the largest of the
accessory glands.
Prostatic fluid is thin, milky,
and quite alkaline, which
balances the acidity of any
residual urine in the urethra
and the natural acidity of the
vagina.
2. PROSTATE GLAND:
This gland is the sources of some of the most common medical
problems of men over 40.
A benign enlargement of the prostate occurs in more than ½ of all men
in this age group.
That is why it is important
to get tested annually after
the age of 40.
3. BULBOURETHRAL GLANDS (cowper’s gland):
These are a pair of small glands along the urethra below the prostate.
They secrete a viscous fluid before emission of the semen.
It has been suggested that this fluid lubricates the penis and vagina,
but the volume (just one or two drops) seems insufficient to be very
effective for this function.
This fluid does carry some
sperm released before
ejaculation,.
This is one factor in the low
success rate of the withdrawal
method of birth control.
The penis is composed of spongy tissue derived from modified veins
and capillaries.
During sexual arousal, this erectile tissue fills with blood from the
arteries.
As it fills, the increasing pressure seals off the veins that drain the
penis, causing it to engorge with blood.
The resulting erection is essential to insertion of the penis into
the vagina (rodents, raccoons, walruses, and several other
mammals also possess a baculum, a bone that stiffens the penis).
The main shaft of the penis is covered by relatively thick skin,
whereas the head (or glans penis) has a much thinner covering
and is consequently more sensitive to stimulation.
The human glans is covered by a fold of skin called the foreskin (or
prepuce).
Foreskin
Glans penis
Viagra is used for the treatment of male impotency. The active
ingredient in Viagra is an inhibitor which allows for increased blood
flow into the penis, which may result in an erection.
Normally, sexual stimulation in the male is followed by release of
nitric oxide (NO) in the penis. Nitrous oxide activates an enzyme
which allows for the relaxation of the penile arteries and an
increase flow of blood into the penile cavity.
The effect of Viagra is to magnify the effect of Nitrous Oxide
release.
One of the curious side effects of Viagra is an effect on the visual
discrimination of certain colors.
MALE SEX HORMONES
The principal male sex hormones are the androgens, of which,
testosterone is the most important.
Androgens are steroid hormones produced by the interstitial cells
of the testes, and are directly responsible for the primary and
secondary sex characteristics of the male.
Androgens are also potent determinants of behaviour in mammals.
In addition to specific sexual behaviour and libido (sex drive),
androgens increase general aggressiveness.
CONSEQUENCES OF USE:
*ROID RAGE (extreme
uncontrollable aggression)
* Irritable and depressed.
* Low sex drive
* Possible cancer & liver
damage
* Feminizing effects in males
(growth of breast tissue)…
* Shrunken testicles…
* Limb loss…
* Heart disease/heart
attacks…
* HIV/AIDS from the sharing
of needles…
CONSEQUENCES OF USE:
* Reduced sperm count…
* Impotence & Infertility…
* Baldness…
* Pain & difficulty urinating…
* Enlarged prostate…
* Adolescents experience
stunted growth…
MALE SEX HORMONES
Primary sex
characteristics:
development of the vas
deferens and other ducts,
the external genitalia,
and sperm production.
All babies start as female.
If testosterone is present,
they will become male, if
not, they will be born
female.
Sex is determined by 13
weeks, sex is determined.
MALE SEX HORMONES
Secondary sex characteristics: features we associate with maleness
such as: deepening of the voice, the male distributions of axillary (armpit),
facial, and pubic hair, and muscle growth (androgens stimulate protein
synthesis).
The hypothalamus makes a hormone called GnRH
(the gonadotropin-releasing hormone).
GnRH control the release of two
hormones from the anterior pituitary:
1. Follicle-stimulating hormone
(FSH)
2. Luteinizing hormone
(LH)
LH stimulates the
interstitial cells in the
seminiferous tubules to
secrete testosterone.
Testosterone has a role in
sperm production and
developing male secondary
sex characteristics.
FSH acts on the epidymis to
help in sperm maturation.
Negative feedback by testosterone controls the actions of GnRH.
Hypothalamus
-
GnRH
Hypothalamus
-
GnRH
Anterior Pituitary
LH & FSH
Hypothalamus
-
GnRH
Anterior Pituitary
LH & FSH
FSH
Follicle stimulating hormone
Hypothalamus
-
GnRH
Anterior Pituitary
LH & FSH
FSH
Follicle stimulating hormone
Epidydimis
Hypothalamus
GnRH
-
Anterior Pituitary
LH & FSH
FSH
Follicle stimulating hormone
Epidydimis
Matures the sperm
(makes it motile)
Hypothalamus
GnRH
-
Anterior Pituitary
LH & FSH
FSH
Follicle stimulating hormone
Epidydimis
Matures the sperm
(makes it motile)
Fish swim
Hypothalamus
-
GnRH
Anterior Pituitary
LH & FSH
LH
luteinizing hormone
FSH
Follicle stimulating hormone
Epidydimis
Matures the sperm
(makes it motile)
Hypothalamus
-
GnRH
Anterior Pituitary
LH & FSH
LH
luteinizing hormone
FSH
Follicle stimulating hormone
Interstitial Cells
Epidydimis
Matures the sperm
(makes it motile)
Hypothalamus
-
GnRH
Anterior Pituitary
LH & FSH
LH
luteinizing hormone
FSH
Follicle stimulating hormone
Interstitial Cells
Epidydimis
Testosterone
Matures the sperm
(makes it motile)
Hypothalamus
GnRH
-
Anterior Pituitary
LH & FSH
LH
luteinizing hormone
FSH
Follicle stimulating hormone
Interstitial Cells
Epidydimis
Testosterone
Sperm
production
2o sex
characteristics
deep voice, body hair,
more muscle, libido…
Matures the sperm
(makes it motile)
Hypothalamus
GnRH
-
Anterior Pituitary
LH & FSH
Teens have a Love
Hate relationship
with testosterone
LH
luteinizing hormone
FSH
Follicle stimulating hormone
Interstitial Cells
Epidydimis
Testosterone
Sperm
production
2o sex
characteristics
deep voice, body hair,
more muscle, libido…
Matures the sperm
(makes it motile)
#
Learning Outcome
Text Pages
P7
P. 418-419
Identify and give a function for each of the
following: ovaries (follicles and corpus luteum),
oviducts (fallopian tubes), uterus, cervix, vagina,
clitoris.
P8
Describe the functions of estrogen.
P. 421-424
P9
Describe the sequence of events in the ovarian
and uterine cycles.
P. 420-423
P10
Demonstrate knowledge of the control of the
ovarian and uterine cycles by hormones.
P. 420-423
P11
Demonstrate knowledge of a positive feedback
mechanism involving oxytocin.
P. 208, 394
P12
Describe the hormonal changes that occur as a
result of implantation.
Page 424
The female gonads, ovaries, are located within the lower
abdominal cavity, below most of the digestive system.
Each ovary is
enclosed in a tough
protective capsule
and contains many
follicles.
A FOLLICLE consists of
one egg cell surrounded by
one or more layers of
follicle cells, which nourish
and protect the
developing egg cell.
All of the 400,000 follicles
a woman will ever have are
formed at birth.
Of these, only several hundred will be released during the
woman’s reproductive years.
After puberty, one (or rarely two or more) follicles matures
and releases its egg during each menstrual cycle.
The cells of the follicle also produce the primary female sex
hormones, ESTROGEN.
When ovulation occurs, the egg is expelled from the
follicle (like a small volcano).
http://images.google.ca/imgres?im
gurl=http://embryology.med.unsw.e
du.au/notes/images/week1/ovary/o
vulation2.jpg&imgrefurl=http://embr
yology.med.unsw.edu.au/notes/we
ek1_3a.htm&usg=__pB3lCLviCh_
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20&sz=6&hl=en&start=4&tbnid=vN
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118&prev=/images%3Fq%3Dovula
tion%26gbv%3D2%26hl%3Den
The remaining follicular tissue grows within the ovary to
form a solid mass called the CORPUS LUTEUM.
The corpus luteum secretes PROGESTERONE (the hormone
of pregnancy) and additional estrogen.
If the egg is not fertilized, the corpus luteum degenerates
and a new follicle matures during the next cycle.
The female reproductive
system is not completely
closed.
The egg cell is expelled
into the abdominal
cavity near the opening
of the OVIDUCT (or
fallopian tube).
The fimbriae on the oviduct sweep the ovary for the egg,
and the cilia on the inner epithelium lining the duct help
collect the egg cell by creating a current to draw fluid into
the duct.
The oviduct is the site of fertilization.
The cilia in this duct also convey the egg cell down the duct
to the UTERUS (womb).
The UTERUS is a thick, muscular organ (shaped like an
upside down pear).
It is remarkably small; the uterus of a woman who has never
been pregnant is about 7 cm long and 4-5 cm wide at its
widest.
The unique arrangement of muscles that make up the uterine
wall allow it to expand to accommodate a 4 kg (9 lb) fetus.
The inner lining of the uterus, the ENDOMETRIUM, is richly
supplied with blood vessels, in which a fertilized egg implants
and develops.
The narrow neck of the uterus
is the CERVIX, which opens
into the VAGINA.
The vagina is a thin-walled
chamber that forms the birth
canal through which the baby is
expelled; it is also the
receptacle for the man’s penis.
The vagina is the terminal portion of the female reproductive
system, but it is covered by two pairs of skin folds.
The female external genitals are collectively known as the
vulva.
The labia minora are the inner folds of skin just
outside the vaginal opening. They are composed of
erectile tissue and enlarge during arousal/intercourse.
The labia majora, a pair of thick, fatty ridges, cover
and protect the genital area.
At the top of these two folds is
a small bulb of erectile tissue
called the glans clitoris,
which is the female equivalent
of the glans of the penis.
Like that organ, it is one of the
most sensitive points of
stimulation in sexual response.
The mammary gland (breast) is
another structure important to
mammalian reproduction, although it
is not part of the reproductive tract
itself.
The secretory apparatus consists of
a series of alveoli, small sacs of
epithelial tissue that secrete milk.
The aveoli drain into a series of
ducts that open at the nipple.
The lack of estrogen in males prevents the development of
both the secretory apparatus and the fat deposits, so the
breasts remain small and the nipple is not connected to the
ducts.
OOGENESIS
The ovary contains many follicles composed of a developing egg
surrounded by an outer layer of follicle cells. Each egg begins
oogenesis as a primary oocyte. The development of ova (mature,
unfertilized eggs) differs from spermatogenesis in three ways.
1. During meiotic divisions of oogenesis, cytokinesis is unequal,
as only 1 of the four cells will develop into an ovum, the other 3
are called polar bodies (which help to nourish the egg).
2. At birth each female carries all of
the egg cells it will ever have,
though still in an immature state.
3. Oogenesis is cyclical. It has
long ‘resting’ periods before the
process is complete.
After puberty, a developing egg
is released each month from
puberty until menopause, a total
of 400-500 eggs.
THE FEMALE HORMONES
The pattern of hormone secretion
controlling female reproduction
differs strikingly from the male
pattern, mostly due to its cyclical
nature.
Whereas the male produces
sperm continuously, females
ovulate only one or a few eggs at
one time during each cycle.
The control of this cycle is
complex.
THE FEMALE HORMONE CYCLES
Two different types of cycles
occur in the female mammals:
1. The menstrual cycle
2. The ovarian cycle
The Menstrual Cycle
The human menstrual cycle refers specifically to the changes that occur in
the uterus.
It lasts an average of 28 days, but only ~30% of women have cycle lengths
within a day or two of the statistical 28 days. Cycles vary from about 20 to
40 days. In some women the cycles are usually very regular, but in other
individuals the timing varies from cycle to cycle.
MENSTRUAL CYCLE : This cycle occurs in the uterus. There are 3
phases in this cycle.
Day 1 is the first day of a woman’s ‘period’ (1st day of menstruation)
THREE PHASES OF THE MENSTRUAL CYCLE
1. The Flow phase: Menstrual bleeding usually persists for a few
days (day 2-8).
2. The Proliferative phase: the endometrium begins to thicken for
a week or two (until ovulation).
3. The Secretory phase: usually about 2 weeks long, the
endometrium continues to thicken, becomes more vascularized
and secretes a fluid rich in glycogen to prepare for a fertilized egg.
MENSTRUAL CYCLE
*If an embryo has not implanted in the uterine lining by the end of the
secretory phase, a new menstrual flow commences.
*If an embryo is implanted before the end of the secretory phase, the
endometrium will remain until birth.
THE OVARIAN CYCLE: This cycle occurs in the ovaries. There are
THREE phases in this cycle
THREE PHASES OF THE OVARIAN CYCLE:
1. This cycle begins with the FOLLICULAR PHASE, during which
several follicles in the ovary begin to grow and release estrogen.
The maturing follicle develops an internal fluid-filled cavity and
grows very large, forming a bulge near the surface of the ovary.
THREE PHASES OF THE OVARIAN CYCLE:
2. The follicular phase ends with OVULATION when the follicle and
adjacent wall of the ovary rupture, releasing the egg cell. The egg
cell is transported into the oviduct and is transported into the
uterus.
THREE PHASES OF THE OVARIAN CYCLE:
3. The last phase is the LUTEAL PHASE. During this phase, the
follicular tissue that remains in the ovary after ovulation is
transformed into the corpus luteum.
The corpus luteum is an endocrine tissue that synthesizes and
secretes hormones to prepare the uterus for pregnancy.
The next cycle begins with growth of new follicles.
These cyclic phases are interrupted only by pregnancy
and continue until menopause, when reproductive
capability ends.
THE FEMALE SEX HORMONES
Hormones coordinate the menstrual and ovarian cycles in such a way
that growth of the follicle and ovulation are synchronized with
preparation of the uterine lining for possible implantation of an embryo.
5 hormones participate in both (+) and (-) feedback cycles:
1. Gonadotropin-releasing hormone (GnRH): secreted by the
hypothalamus
2. Follicle stimulating hormone (FSH): secreted by anterior pituitary
3. Luteinizing hormone (LH): secreted by anterior pituitary
4. Estrogen: secreted by ovary (follicle)
5. Progesterone: secreted by ovary (corpus luteum)
1. During the follicular
phase of the ovarian
cycle, the hypothalamus
releases GnRH.
2. This causes the anterior
pituitary to secrete
small quantities of FSH
and LH.
3. At this time, the follicles
in the ovary have
receptors for FSH, but
not for LH.
The FSH causes the
follicles to grow.
4. The follicles release
estrogen as they grow.
The amount of estrogen
secreted during this time
is small.
5. When the [estrogen]
secretion begins to rise,
it causes the
hypothalamus to
release more GnRH
(positive feedback).
6. GnRH causes even
more LH and FSH to be
released from the
anterior pituitary.
7. This causes the LH
SURGE.
8. By now, the follicles have
receptors for LH and can
respond to this hormonal
cue.
The LH SURGE induces
final maturation of the
follicle.
9. Ovulation occurs on
day 14, about one day
after the LH surge.
10. After ovulation, LH will
stimulate the follicle to
become the corpus
luteum.
11. LH will also stimulate the
corpus luteum to start
secreting estrogen and
progesterone.
12. The corpus luteum
reaches its maximum
development about 8-10
days after ovulation. At
this point there is very
high [progesterone] and
[estrogen] in the blood.
13. High levels of these
hormones exerts
negative feedback on
the hypothalamus.
14. This causes a severe
decrease in the amounts
of LH and FSH.
15. When [LH] plummets,
the corpus luteum
begins to degenerate.
16.This causes a sharp
decrease in the
[estrogen] and
[progesterone].
17. Without these
hormones, the
endometrium layer is
sloughed off and day
one of the cycle begins
again.
18. As these hormones
drop off, the
hypothalamus and
pituitary are not
inhibited anymore.
19. So the anterior
pituitary begins to
secrete enough FSH to
stimulate growth of
new follicles in the
ovary.
20. This initiates the
follicular phase of the
next ovarian cycle.
How is the ovarian cycle synchronized with the menstrual cycle?
1. Follicular phase/proliferative phase: Estrogen (which is released by
follicles in the follicular phase) is a hormonal signal to the uterus, which
stimulates the development of the endometrium (proliferative phase).
FOLLICULAR PHASE
e
s
t
r
o
g
e
n
PROLIFERATIVE
PHASE
How is the ovarian cycle synchronized with the menstrual cycle?
2. Luteal phase/secretory phase: After ovulation, estrogen and
progesterone secreted by the corpus luteum stimulate continued
development and maintenance of the endometrium (secretory phase)
as the body prepares for the possibility of a fertilized egg.
LUTEAL PHASE
p
r
o
g
e
s
t
e
r
o
n
e
SECRETORY PHASE
How is the ovarian cycle synchronized with the menstrual cycle?
3. A rapid drop in the level of
estrogen and progesterone
hormones when the corpus
luteum degenerates causes
spasms of the arteries in the
uterine lining that deprive the
endometrium of blood.
Degeneration of the endometrium
results in menstruation and the
beginning of a new menstrual cycle.
In the meantime, ovarian follicles
that will stimulate renewed
thickening of the endometrium are
just beginning to grow.
Corpus
luteum dies
L
o
w
E
&
P
MENSES
Day 1
Review of female cycles:
http://images.google.ca/imgres?imgurl=http://www.msnbc.com/news/wld/graphics/menstrual_cycle_dw.jpg&imgrefurl=http://ww
w.msnbc.com/news/wld/graphics/menstrual_cycle_dw.htm&usg=__xUXLpPolNSPez1cMkDlGK_zxU4w=&h=400&w=520&sz=
30&hl=en&start=24&tbnid=Wua0J3g_usMtPM:&tbnh=101&tbnw=131&prev=/images%3Fq%3Dmenstrual%2Bcycle%26start%
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In addition to their role in coordinating reproductive cycles,
estrogens are also responsible for the secondary sex
characteristics of the female:
1. Deposition of fat in the breasts and hips
2. Increase in water retention
3. Affects calcium metabolism
4. Stimulates breast development
5. Mediates female sexual behavior
6. Initiates female libido
7. PMS
8. Mood swings
9. Cravings (chocolate, cheese, milk…)
10. Growth of hair (not as much as men)
If the egg is fertilized, the resulting embryo will start to release a hormone
called human chorionic gonadotropin (HCG).
HCG acts like LH to maintain the corpus luteum and this allows the
levels of progesterone and estrogen to remain high.
Thus, the endometrium layer is NOT sloughed off and is maintained by
the high levels of hormones.
The levels of HCG are so high, that some is excreted in the urine, where it
can be detected in pregnancy tests.
HCG
Other changes for the mother in
the first trimester include:
•Increased mucous in the cervix to
form a protective plug.
•Growth of the placenta
•Enlargement of the uterus
•Morning sickness
•Mood swings
•Weight gain of ~1kg
•Cessation of ovulation and
menstrual cycling
•Breasts become large and tender
Oral contraceptives (birth control pills)
usually contain a combination of
estrogen and progesterone.
High levels of these hormones prevent
the release of FSH and LH, and thus
inhibit the development of any new
follicles. And this means no eggs
released and no fertilization possible.
This tricks your body into thinking you
are pregnant. The days that you take
a placebo, would be the days you have
your period.
OTHER OPTIONS?
1. Time-release capsules (Norplant) can be implanted under the skin
and offer long-term suppression of ovulation. May double the risk of
blood clots.
2. There is also an injection available, which you receive once every 3
months (it acts similarly to the pill).
3. RU-486, the ‘morning after pill’, interferes with implantation of the
blastula into the uterine wall. Its use as a contraceptive is very
controversial.
4. Barrier methods: physical (condom, diaphragm) or chemical
(spermacides) means to separate the sperm from the egg.
5. Physical prevention (most effective) include vasectomy and tubal
ligation.
Male fruit bat of the species
Rousettus aegyptiacus
have testes that are 2.15 %
of body mass, whereas their
brains are only 1.70 %.
The males in some bat
species can have testes
that are up to 8.5 % of their
body mass.
It is a baculum, or penis bone, of an extinct species of walrus. The
12,000 year old fossil was discovered in Siberia. What remains is a
4 ½ foot piece of dry muscle tissue and weathered skin.