Download Human Biology 4.3

Human Biology 4.3
The reproductive system allows
the production of offspring.
The reproductive system produces
specialized cells.
• The reproductive system allows adults to produce
offspring.
• Males and females have different reproductive systems
which make specialized cells.
– Female specialized cells are called egg cells.
– Male specialized cells are called sperm cells.
• Each specialized cell provides genetic material, needed
information for the organism to form, develop, and grow.
• Both male and female reproductive systems rely on
hormones to signal the process of sexual development.
– Growth of reproductive organs
– Development of sexual characteristics.
• Once mature, reproductive organs produce hormones to
maintain secondary sexual characteristics.
The reproductive system produces
specialized cells.
Main Idea
Detail Notes
A. Males and females have different
reproductive systems.
B. Both males and females make
specialized reproductive cells.
The reproductive system
produces specialized cells.
C. In the female, the specialized cells
are called egg cells.
D. In the male, the specialized cells
are called sperm cells.
E. Each cell contains all the genetic
material needed for growth and
development.
The Female Reproductive System
• The female reproductive
system has two functions.
– produce egg cells
– protect and nourish the
offspring until birth.
• Two reproductive organs
called ovaries.
– Each contains hundreds of
egg cells.
– Pituitary gland releases a
hormone that stimulates
some of the eggs to develop
and grow every 28 days.
Menstruation
• After an egg cell develops another hormone signals the
ovary to release the egg.
• Egg moves from the ovary into a fallopian tube.
• If within ten to twelve hours the egg cell is fertilized by a
sperm cell, it will move to the uterus.
• After implanting inside the thick lining of the uterus, the
fertilized egg cell rapidly grows and divides.
• If fertilization does not occur within 24 ,the egg and the
lining of the uterus begin to break down.
• Muscles in the uterus contract in a process called
menstruation.
• During menstruation there is a flow of blood and tissue
from the body through a canal called the vagina over a
period of about five days.
The Female Reproductive System and
Menstruation
Flow of blood and
tissue
Lasts about 5 days
Menstruation
Occurs if fertilization
does not take place
Muscles of the
uterus contract
The Male Reproductive System
• The organs that produce sperm are called the testes.
• Produced inside tiny, coiled tubes hundreds of feet long inside the
testes.
• The testes release a hormone that controls the development of
sperm.
• This hormone is also responsible for physical characteristics such as
facial hair and a deep voice.
• Sperm cells are the specialized cells of the male reproductive system.
• Sperm starts being produced sometime during adolescence.
The Male Reproductive System
•The sperm is a single cell with a head and a tail.
•The head is filled with chromosomes.
•The tail functions as a whip to make the sperm mobile.
•Sperm travel from the testes, through several different structures of
the reproductive system.
•While they travel, the sperm mix with fluids called semen which
contains nutrients for the sperm cells.
•One drop of semen contains up to several million sperm cells.
Chromosomes are
contained in the
nucleus.
The reproduction of offspring includes
fertilization, pregnancy, and birth.
• Each sex cell has half of the genetic material
needed for a human being to grow and
develop.
• During sexual intercourse, millions of sperm
cells leave the testes and exit the body
through the urethra.
• Sperm is ejaculated into the female’s vagina.
• Sperm travel into the uterus and continue to
the fallopian tube.
Reproduction includes fertilization,
pregnancy, and birth.
Step 1
• The sperm leave the testes.
Step 2
• The sperm exit through the urethra.
Step 3
• The sperm enter through the vagina.
Step 4
• The sperm travel to the uterus and on to the
fallopian tube.
Fertilization
• Occurs when one sperm cell joins the egg cell.
• Once fertilized in the fallopian tube, chemical
changes to the egg’s surface prevent any more
sperm from entering.
• Once inside the egg, the genetic material from
the sperm combines with the genetic material of
the egg cell.
• The fertilized egg cell moves down the fallopian
tube toward the uterus.
• It divides into two cells, then each of those cells
divides again.
• Cell division continues, and within a few days, the
embryo implants itself to the lining of the uterus
The egg cell moves down the
fallopian tube following
fertilization. Its final destination
is the uterus.
Pregnancy
• Three periods of specific stages of development.
• Week 1 the embryo grows rapidly and the placenta forms.
– Blood vessels lead from the mother’s circulatory system to the
embryo through the umbilical cord.
– Oxygen and nutrients move through the placenta and umbilical
cord to the growing embryo.
• Week 8 the developing embryo is called a fetus.
–
–
–
–
Begins to have facial features
Major organ systems
Beginnings of a skeleton
Becomes male or female
• Week 12 fetus continues to grow and bones develop further.
• In the last twelve weeks the fetus and all its organ systems
develop fully.
Labor and Delivery
• At the end of pregnancy, the fetus is fully developed.
• Birth of a fetus is divided into three stages.
– Labor
• Begins with muscular contractions of the uterus.
• Contractions start at 10 to 30 minutes and last about 40 seconds.
• They progress until they are occurring about every 2 minutes.
– Delivery
• Cervix dilates until it becomes wide enough for the mother’s muscles
to push the fetus out.
• The fetus is pushed out of the uterus, through the vagina, and out of
the body.
• The fetus is still connected to the mother by the umbilical cord.
– Birth of the placenta
• The umbilical cord is cut shortly after the fetus is delivered.
• The placenta separates from the uterine wall and the mother pushes
it out with more muscular contractions.
Pregnancy, Labor and Delivery, and
Multiple Births
Name of the
Stage
What Happens in This Stage
First
labor
The uterus contracts
Second
Delivery of
the fetus
Third
birth
The baby is pushed out
of the uterus
The placenta is pushed
out
Multiple Births
• The birth of more than one offspring is called a multiple
birth.
– Uncommon in humans
• Identical twins are produced when a single fertilized egg
divides in half, forming two complete organisms.
–
–
–
–
–
Always of the same sex
Look alike
Have identical blood types
Form early in pregnancy
Approximately 1 in 29 births is a set of identical twins
• Fraternal twins are produced when two eggs are released
at the same time and are fertilized by two different sperm.
– May be very different from each other
– Can be the same sex or different sexes
Identical twins, which
begin as a single
fertilized egg, are
always the same sex
and blood type, and
are very hard to tell
apart.
Fraternal twins may or
may not be the same
sex or blood type, and
they often do not look
any more alike than
other siblings.