Transcript Embryonic Development and Implantation

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Vicki Hughes
Chapter 16: Reproductive System
Gonads = primary sex organs (testes and ovaries)
Gametes = sex cells (sperm and ova)
Roots:
Gonad = seed
Albu = white
Ductus = carrying away
Gen = origin
Epi = on top of
Corp = body
Leut = yellow
Assignments:
OL CH 16 Flashcards
treehugger.com
Male Anatomy
Penis = delivers sperm to vagina
Testes = manufactures sperm
Epididymis = stores immature
sperm
Ductus deferens =
delivers sperm to penis
Seminal vesicle =
produces most of fluid
carrying sperm
Prostrate Gland =
secretes milky fluid
that activates sperm
Bladder
Ductus
deferens
Seminal
vesicle
Prostate gland
Epididymis
Spermatogenesis = production of sperm
Spermatogenesis occurs
in the seminiferous
tubules located inside the
testes.
Immature sperm are
stored in the epididymis.
Seminiferous tubules
http://bio1151.nicerweb.com
In the Seminiferous Tubules…
1. Germ cells near the outer wall of
the seminiferous tubules of the
testis differentiate into stem cells
called spermatogonia.
2. Spermatogonia divide by mitosis,
and mature into primary
spermatocytes.
3. Each primary spermatocyte
undergoes meiosis yielding 4
equal-sized spermatids.
4. The spermatids migrate toward
the lumen (central opening).
5. Sertoli cells supply nutrients for
the spermatids, which mature
into motile sperm in the
epididymis.
Spermatogenesis
http://wps.aw.com/bc_martini_eap_4/40/104
69/2680298.cw/content/index.html
http://bio1151.nicerweb.com
Diseases of the male reproductive system
Hydrocele
Testicular Cancer
Benign Prostrate Hyperplasia
Female Anatomy
Ovary = location of maturing eggs
Fallopian Tubes = provide passage of egg to location for fertilization
Uterus = the “womb”
where the egg
develops into a fetus.
Vagina = “birth canal”
Oogenesis = production of egg
1. Follicle = saclike structures
with one egg each.
2. Oocyte = unfertilized egg
3. FSH = follicle stimulating
hormone
4. Ovarian cycle = monthly
maturation of a small
number of follicles.
5. Produces 2 cells: larger
oocyte and smaller polar
body.
6. Secondary oocyte grows
and bursts from follicle –
“ovulation.”
7. Polar body is discarded.
http://wps.aw.com/bc_martini_eap_4/40/10
469/2680298.cw/content/index.html
http://www.como.wa.edu.au
The polar body has no real purpose.
Polar body
When the body cell undergoes meiosis to
produce the egg, ½ of the nuclear material
goes into the egg to be fertilized and ½
goes into the polar body.
The egg receives the bulk of nutrient rich
plasma to provide maximum nutrients in
the event of fertilization.
The polar body basically “gives up” its
plasma and nutrients for the good of the
other egg.
Diseases of the female reproductive system
Endometriosis
Ovarian cyst
Sexually Transmitted Diseases (STDs)
Aids
syphilis
Gonorrhea
Genital Herpes
Chlamydia
Genital Warts
Menstrual Cycle (No Fertilization)
Day 1-7 Menstruation
(bleeding)
Day 8-11 Uterus thickens
Day 14 Ovulation
Day 18-25 Corpus
Luteum fades away
Day 26-28 Uterine lining
detaches
Start over at Day 1
above.
Birth Control
FEMALE BIRTH CONTROL
• Tubal ligation is a surgical
procedure in which the
uterine tubes are separated.
• Tying of the tubes also
prevents pregnancy.
• Sperm cannot reach the
egg and the egg cannot
reach the womb.
• Hysterectomy is surgical
removal of the uterus.
Birth Control
MALE BIRTH CONTROL
• Mature sperm are
stored in the epididymides
• Vasectomy is a
surgical contraceptive
procedure whereby the
vas deferens are
permanently divided,
preventing the
spermatozoa from leaving
the epididymis
• Following vasectomy, a man
can only ejaculate seminal fluids
that are free of sperm cells.
Fertilization
• Sperm are released into
the vagina and move through
the cervix into the uterus.
• From there sperm move
through the fallopian tube to
the egg.
• Fertilization occurs about
1/3 of the way from the ovary
to the uterus.
Fertilization
• Once a sperm has reached
the egg it uses specialized
enzymes which break down
the egg covering.
• The sperm is then
absorbed into the egg as the
two membranes fuse.
Embryonic Development and Implantation
Once the egg is fertilized it is
called a zygote.
Zygote
Early Cleavage
For the first 0-2 days, the zygote
is dividing
but not growing.
Morula
Blastocyst
This early division is called
early cleavage.
Formation of
ectoderm,
mesoderm and
endoderm
Gastrula
www.msdellasantina.com
Embryonic Development and Implantation
Early cleavage occurs in the
fallopian tube prior to entry into
the uterus.
www.msdellasantina.com
Embryonic Development and Implantation
The morula stage is reached in
3 to 4 days.
Earlyball
Cleavage
TheZygote
morula is a solid
of 16
or more cells.
Formation of
ectoderm,
mesoderm and
endoderm
Morula
Blastocyst
Gastrula
www.msdellasantina.com
Embryonic Development and Implantation
The morula enters the uterine
cavity, remaining there for 4 to 5
days as it continues to divide into
100 cells or more.
www.msdellasantina.com
Embryonic Development and Implantation
As mitosis continues, a cavity
forms within the mass of cells.
This hollow ball stage is called
a blastocyst, and the cavity is
the
blastocoel. Early Cleavage
Zygote
Trophoblast
Blastocoel
Morula
Blastocyst
The outer layer of the cells of
the blastocyst is called the
trophoblast.
Formation of
ectoderm,
mesoderm and
endoderm
Gastrula
www.msdellasantina.com
Embryonic Development and Implantation
An inner cell mass called the
embryoblast will develop.
The trophoblast becomes
the
Early
Cleavage
fetalZygote
portion of the placenta, and
the embryoblast becomes the
embryo.
Formation of
ectoderm,
mesoderm and
endoderm
Becomes placenta
Becomes embryo
Morula
Blastocyst
Gastrula
www.msdellasantina.com
Embryonic Development and Implantation
Approximately 6 days following
ovulation, the blastocyst attaches
to the endometrium, usually on
the posterior wall.
This attachment is called
implantation.
www.msdellasantina.com
During implantation the embryoblast undergoes embryogenesis
in which the three primary germ layers - ectoderm, mesoderm
and endoderm - are formed.
The germ layers
give rise to the
primary layers of
the individual.
By the end of two weeks,
embryogenesis is
complete, and the
individual is an embryo.
Embryonic Development and Implantation
By the end of the 3rd
week the human
embryo is at the
gastrula stage.
Zygote
Early Cleavage
During the gastrula
stage one end of the
gastrula invaginates
(folds into the ball)
forming what will
Formation of
become
the gut.
ectoderm,
Morula
Blastocyst
Gastrula
mesoderm and
endoderm
www.msdellasantina.com
The chorion
becomes part of the
placenta that
houses the
growing fetus.
The amnionic
cavity fills with fluid
that cushions the
growing fetus.
At the beginning of
the 5th week,
organs, eyes,
limbs, and brain
are forming.
Note: At this
stage, all humans
have a tail and
gills (pharyngeal
pouches). This is
evidence of our
evolutionary
ancestry.
After the first two months of development, the embryo is called a
fetus.
Embryo
Fetus
During the remainder of development there is an enormous
increase in size, with weight increasing by a factor of 600.
By the end of the first trimester (3 months), sexual differentiation
has occurred, the fetus kicks and sucks its thumb; breathing
movements bring amniotic fluid in and out of the lungs.
By the end of the second trimester, the fetus is 12 inches long,
has hair, eyebrows, and eyelashes, and is moving a great deal.
The third trimester is a time of maturation of the digestive and
respiratory systems.
Pregnancy Hormones
Three primary hormones
Involved in pregnancy:
1. Human chorionic
gonadotropin (HCG)
2. Estrogen
3. Progesterone
• Following fertilization, HCG is produced by the embryo.
• HCG causes corpus luteum to secrete estrogen and
progesterone.
Estrogen and Progesterone
•
•
•
•
•
stimulate uterine lining to continue development
stop the menstrual cycle
stimulate the development of mammary glands
prevent premature contractions
enlarge the reproductive organs
Relaxin
• relaxes the pelvic ligaments
Physicians usually calculate the
gestation period, or length of
the pregnancy, as 280 days (40
weeks or 10 lunar months) from
the last menstrual period (LMP)
to the date of confinement,
which is the date of delivery of
the infant.
Parturition refers to the process by which the baby is born.
Stages of Parturition
Labor occurs in three stages: dilation stage, expulsion stage,
and placental stage.
• Dilation is the longest stage marked by dilation (widening)
of the cervical canal and by effacement (thinning) of the
cervix.
• Expulsion stage begins when the baby's head enters the
vagina and lasts until the baby is entirely expelled.
• Placental stage results in expulsion of the placenta,
amnion, and other fetal membranes.
• Two weeks or so before
birth, the fetus "drops"; its
head lies against the cervix,
which may begin to dilate.
cervix
• Baby starts the birthing
process. When the fetal brain
has sufficiently developed, the
fetal hypothalamus causes
the anterior pituitary to signal
the fetal adrenal cortex to
release hormones which
trigger the uterine
contractions that expel the
fetus.
As the uterus contracts, the baby’s head pushes against the
cervix, causing it to dilate. Cervical dilation is the first stage of
labor. The amniotic sac may rupture during this stage. This is
commonly called “water breaking.”
When the cervix has dilated to 10 centimeters, the second stage
of labor begins and the baby moves down the vagina. Once the
baby is born, the umbilical cord can be cut.
The placenta
remains in the
uterus. The
third stage of
labor is delivery
of the placenta,
also called
the "afterbirth."
Hormonal Control of Lactation
The Miracle of Life
http://www.pbs.org/wgbh/nova/body/lifegreatest-miracle.html
You should now be able to:
1.
2.
3.
4.
Distinguish between gonads and gametes.
Identify male and female reproductive structures and functions.
Describe spermatogenesis and oogenesis.
Describe the diseases of the male and female reproductive systems that we
studied.
5. Define a polar body.
6. Describe the menstrual cycle without fertilization.
7. Describe types of birth control for males and females.
8. Describe the development of a fetus from fertilization of the egg to
implantation in
the womb.
9. Describe the steps of parturition.
10. Describe the growth and development of the embryo into a fetus.
11. Discuss the involvement of HCG, estrogen and progesterone during
pregnancy.
12. Define gestation and describe how doctors calculate due dates.
13. Describe the hormonal control of lactation.
Any
questions?