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Chapter 3 Understanding Human Development.
All mammals start life as a tiny fertilized egg. The human
reproductive system is designed to produce gametes and
bring them together through internal fertilization.
Hormones - Messengers in the human body. They travel
through the bloodstream and cause certain cells to
respond in specific ways. Several hormones regulate the
reproductive system.
Puberty - The period when an individual becomes
capable of sexual reproduction and develops secondary
sex characteristics. Hormones change the body so that it
becomes able to reproduce.
When Puberty Begins..
The pituitary gland, located at the base of the brain, starts
to produce follicle stimulating hormone (FSH). FSH
travels to the gonads and signals them to produce
gametes. Other hormones help in the development and
maintenance of secondary sexual characteristics.
Puberty in Males
When FSH reaches the testes it promotes the development
of sperm-producing tubes in the testes and the
development of sperm cells. Other cell in the testes start
to produce Testosterone, which directs the development
of secondary sexual characteristics-deeper voice, body
hair, and broadening of the shoulders.
Puberty in Females
When FSH reaches the ovaries they are stimulated to
begin maturing and releasing eggs. Generally one egg is
released each month. FSH also stimulates the ovaries to
produce Estrogen, which directs the development of
female secondary sexual characteristics-body hair,
deposits of fat in the breasts and hips. After the age of 45
to 50, a woman stops releasing an egg each month
because her estrogen levels drop. This change in the
hormonal cycle is known as menopause.
Copy Page 82 Male Reproductive Anatomy
Copy Page 84 Female Reproductive Anatomy
Make a table listing the Male Parts and their function.
Make a table listing the Female Parts and their function.
Starting Points Activity Page 79
Predicting Reproductive Trends Page 81. Drawing a line
graph Page 591
Copy Page 83 Sperm Development.
Page 83 Answer the Pause and Reflect
More about Females:
Ovaries are about 3cm in length and one egg or ovum
(plural ova) is released by the ovary approximately every
28 days. The two ovaries generally alternate, or take
turns, releasing an egg.
Ovulation
The surface of the ovaries contains many fluid filled
cavities called follicles. Each follicle contains an egg.
During ovulation, a mature egg breaks out of its follicle.
The feather ends of the oviducts, or Fallopian tubes, help
guide the egg into the tube. Hair like structures lining the
oviducts keep the egg moving towards the uterus. The
egg can only survive for 24 to 48 hours after ovulation,
unless fertilized. .
Sperm Development
Sperm are produced from the cells in the walls of the
semniferous tubules. Diploid cell (46) are forced away
from the tubule walls by mitosis. These cells undergo
meiosis to produce mature sperm. The entire process of
sperm production takes 9 to 10 weeks.
Menstrual Cycle
Before and after ovulation, the female reproductive
system undergoes changes in a cycle that last
approximately one month. The pituitary hormones tell
the ovaries what to do and the ovarian hormones tell the
uterus what to do.
Luteinising hormone (LH) is released by the pituitary
gland. Progesterone is released by the ovary.
Progesterone comes from the corpus luteum a structure
formed from the follicle after the egg is released.
The Female Hormones.
1. Pituitary Releases FSH
2. FSH stimulates follicles to develop.
3. A developing follicle releases estrogen.
4. -Estrogen stimulates the lining of the uterus to thicken
-Estrogen also travels to the pituitary stimulating the
pituitary to release LH.
5. LH causes the developing follicle to release a mature
egg (ovulation)
6. LH stimulates the empty follicle to develop into the
corpus luteum.
7. Corpus Luteum produces progesterone and estrogen.
8. -Progesterone increases the thickening of the uterine
lining.
-Progesterone cause the pituitary to decrease
production of FSH and LH preventing more egg cells
from being released.
9. If the egg is not fertilized, The corpus luteum breaks
down, reducing progesterone in the bloodstream.
Declining progesterone levels cause the uterine lining to
break down. The lining, consisting mainly of dead cell
and blood, is shed form the body in the process know as
menstruation. Menstruation lasts for four to seven days.
As the levels of progesterone decrease to a certain level,
the pituitary gland will begin to produce FSH again.
Page 90 Check Your Understanding
Questions 1, 2, 4, 5, 6.
Page 106 Reviewing Key Terms
1 (only those with section 3.1)
Page 106 Understanding Key Concepts
5, 7, 8, 10.
Page 99 Fetal Development Activity Rulers Required!!!
Page 100 Risk Factors during Fetal Development.
Pregnancy
Sperm move through the uterus and into the oviducts.
Fertilization occurs in the oviducts. Only 1 sperm will fertilize
the egg. After fertilization, the zygote continues down the
oviduct toward the uterus. On its way, it begins the process of
mitosis. The zygote undergoes a series of rapid cleavages or cell
divisions. When it reaches the uterus, it has become a mass of
cells arranged to form an almost hollow ball of cells called a
blastocyst. The outer cells of the blastocyst will form the
placenta, the inner cells will form the embryo.
Implantation
The embryo attaches itself to the thickened lining of the uterus
in a process called implantation. This occurs six to ten days
after fertilization. At this point pregnancy begins. The attached
embryo produces a hormonal signal that prevents the corpus
luteum form disintegrating. The corpus luteum continues to
produce progesterone. This Keeps the uterine lining in place,
which means there is no menstrual flow. The corpus luteum
produces progesterone for approximately the first 3 months of
pregnancy.
Page 92. Outside Link
What is IVF?
What percentage of couples are not able to conceive a child?
When are the embryos transplanted into the uterus?
Page 92 Off the Wall.
Summarize and Answer the question.
Page 92 Did you know?
Summarize.
Embryo Development
When the embryo is in the blastocyst stage, its cells are mostly
similar to each other. Then, cells begin to specialize to form a
gastrula, in a process called gastrulation. The cells of the
embryo become arranged into distinct layers called germ layers.
The cells move to specific positions to form three layers called
the endoderm, mesoderm and the ectoderm.
* Draw and label the germ layers on page 93 at the top of the
page.
Supporting Tissues
The outer portions of the embryo develop four important tissues:
1. The yolk sac supplies nutrients to the embryo for the first two
months.
2. The amnion forms a fluid filled sac around the embryo.
3. The allantois helps remove waste from the embryo.
4. The chorion surrounds the embryo, yolk sac, amnion and
allantois. It develops many finger like projections that extend
into the uterine wall to serve as kind of an anchor. Inside the
fingers are blood vessels. Together, the blood vessels and
chorion make up the placenta.
Once the placenta has formed, it takes over the yolk sac’s role in
supplying nutrients to the embryo. It also maintains high levels
of progesterone necessary to sustain pregnancy.
The embryo is attached to the placenta by the umbilical cord.
Sketch the tissues supporting development of the embryo on the
bottom of page 93.
Differentiation and Birth.
Define Differentiation. Page 95
Pages 95 to 98 Describe the changes in the developing child
during each Trimester.
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