Transcript ANATOMY - REPRODUCTION

pregnancy + development
In your textbook
Fertilization & Pregnancy
Conception: What fertilization and implantation are
referred to as
Development begins as embryo is moved to uterus
After about 3 days, embryo implants into the
endometrium
HCG secretes through membranes surrounding
embryo
Uterine tissues form placenta, which exchanges gases
and nutrients between fetal & maternal blood
Control of Reproduction
41.4 in
your textbook
Abstinence: Not engaging in sexual
intercourse.
Most
reliable. Prevents transmission of sexually transmitted
diseases (STDs).
Male and female condoms.
Changes in signal transduction pathways can alter
cellular response.
Preven: Kit made up of four synthetic progesterone
pills. Upsets normal uterine cycle, making it difficult for
embryo to implant itself in the endometrium. Studies
show it is 85% effective in preventing unintended
pregnancies.
Control of Human
Reproduction
Contraceptive vaccines are now being
developed.
41.4 in your textbook
Types intended to women against HCG, the
necessary hormone to maintaining the implantation
of the embryo. Immunization wears off with time,
studies show.
Research for developing safe/effective hormonal
birth control for males. Implants, pills, patches, and
injections are all being tested as ways to deliver
testosterone and/or progesterone to suppress sperm
production. Still in experiment unlikely to be
available outside of clinical trials for at least a few
more years.
Reproductive Technologies
41.4 in your textbook
Infertility: The inability of a couple to achieve
pregnancy after one year of regular, unprotected
intercourse.
Females (if healthy body weight/no obstruction
is apparent in their body) may take fertility
drugs, gonadotrophic hormones that stimulate
the ovaries and bring about ovulation. May
result in multiple ovulations and multiple births.
Adoption
Reproductive Technologies
Assisted Reproductive Technologies
(ARTs)
41.4
in your textbook
developed to increase chances of pregnancy. Lab
settings.
Artificial Insemination by Donor (AID): Sperm are
placed in vagina by a physician. Especially helpful if
male has low sperm count. Donor sperm is common.
IUI (intrauterine insemination) fertility drugs given
to stimulate ovaries but donor’s sperm is placed in
uterus.
Surrogate Mothers: Women are contracted and paid to
have babies. Sperm and oocytes of couple inside
woman’s body.
Reproductive Technologies
41.4 in your textbook
In Vitro Fertilization (IVF): Union of sperm and an egg
to form a zygote occurs in laboratory glassware.
Retrieve immature oocytes by using a needle
Immature oocytes mature in glassware, then
concentrated sperm are added.
After 2-4 days, embryos are ready to be
transferred to the uterus of the woman, who is in
the secretory phase of her uterine cycle
(because she is under fertility drugs).
Ethical Concerns With IVF
Little evidence to suggest that children born as a result
of standard IVF protocols are different in any way from
children conceived naturally. Equality is important in
esteeming them!
Potential risks in drug treatments given to woman.
Concerns about artificial selection of sperm and
injection.
Natural selection of sperm doesn’t occur.
Unhealthy ones are bypassed. Evidence shows
higher rates of abnormality in offspring.
Sexually Transmitted
Diseases 41.5 in your textbook
Caused by organisms such as viruses and bacteria.
AIDS: Acquired immunodeficiency syndrome caused
by HIV (human immunodeficiency virus). Transmitted
by sexual contact with an infected person, needlesharing, etc. HIV attacks helper T cells and makes
them decline in number. This makes a person become
more susceptible to other types of infections. Epidemic
disease.
Genital Herpes: Caused by Type 2 herpes simplex
virus. Repeatedly flares up.
STDs continued
41.5 in your textbook
Hepatitis: Infects liver and can cause cancer and
death.
Hepatitis A - usually acquired from sewagecontaminated drinking water, but also can be
transmitted through sexual/oral contact.
Hepatitis B - can be spread by blood transfusions
and bodily fluids.
Hepatitis C - “posttransfusion hepatitis” can be
transmitted through sexual contact. No vaccines
available for this type.
STDs continued...
41.5 in your textbook
Chlamydia: Caused by tiny bacterium clled Chlamydia
trachomatis.
Men: 8-21 days after infection men may
experience a mild burning sensation on urination
and a mucoid discharge.
Women: May have vaginal discharge or
symptoms of a urinary tract infection. Can cause
cervical ulcerations, which increase the risk of
acquiring AIDS. Possible risk of pelvic
inflammatory disease if untreated--which can
lead to sterility and infertility.
STDs continued
in your textbook
Gonorrhea: Caused by bacterium Neisseria41.5
gonorrhoeae.
Latent infection leads to pelvic inflammatory disease in both
genders--which affects the vasa deferentia or oviducts. As
inflamed tubules heal, they may become partially or completely
blocked by scar tissue, resulting in infertility or sterility. If baby is
exposed during birth, an eye infection leading to blindness can
result. All newborns are given eyedrops to prevent this
possibility.
Gonorrhea proctitis, infection of the anus. Causes anal pain and
blood or pus in feces. Oral/genital contact can cause infection of
the mouth, throat, and tonsils. Can spread to internal parts of
body, causing heart damage or arthritis.
Up to now, gonorrhea was curable by antibiotic therapy, but
resistance to antibiotics is becoming more and more common.
STDs continued.......
41.5 in your textbook
Syphilis: Caused by Treponema pallidum. 3 stages
separated by latent periods.
Primary stage: hard chancre (ulcerated sore w/
hard edges) appears. Secondary Stage: Rash
appears all over body--even palms of hands.
Tertiary stage: may affect cardiovascular and/or
nervous system.
Infected person may become mentally retarded,
blind, walk with shuffle, or show signs of insanity.
Asexual Reproduction
•Single parent gives rise to an identical offspring, unless
mutations have occurred
o
Good because you can reproduce rapidly and
colonize quickly
•Many different means
o
Sponges produce gemmules that develop into
individuals
o
Cnidarians reproduce by "budding", where an
outgrowth from the parent becomes an individual
continued
•Flatworms, roundworms, insects, some turkeys, etc.
can reproduce pathogenically
o
Modification of sexual reproduction were an
unfertilized egg develops into a complete individual
o
In bees, queen selectively fertilizes some eggs with
stored sperm

Unfertilized eggs become haploid males
Sexual Reproduction
• Sex cells (gametes) produced by parents unite, forming a
genetically unique being
• Hermaphroditic organisms (have both sets of sex organs)
can self-fertilize
o
Sex reversal can also occur
• Animals produce gametes in regions called gonads
(sponges are the exception)
o
Testes and ovaries
• Eggs or sperm are derived from germ cells, which are
Life History Strategies
• Oviparous- Any animal that deposits an egg in the external
environment
o
Usually leads to larval stage (immature)
• When terrestrial animals lay eggs, they contain an
extraembryonic membrane to prevent drying out & protect
embryo
o
One membrane surrounds the yolk, which is nutrient rich
material
• Viviparous- Animals who have young inside them in placenta,
which supports the baby until it's ready for independence
Fertilization
42.1 in your textbook
Fertilization is the union of a sperm and an egg to form
a zygote. It requires a series of events that will result
in the diploid zygote.
Acrosome reaction is the reaction that occurs in the
acrosome of the sperm as it approaches the egg.
Cortical reaction occurs in fertilization when a sperm
cell unites with the egg’s plasma membrane. (zona
reaction)
Process of Fertilization
Vesicles in the egg called cortical granules secrete
enzymes that turn the zona pellucida, forming an
impenetrable fertilization membrane; this is called
“Slow Block.”
As soon as plasma membranes of the sperm and egg
fuse, the zona pellucida lifts away from the surface of
the egg, forming a moat that prevents entrance of any
other sperm.
The diploid zygote forms when a nuclear envelope
surrounds the sperm and egg chromosomes.
Process of Fertilization
Several sperm penetrate the corono radiata and
several sperm attempt to penetrate the zona pellucida
One sperm enters the egg and their nuclei eventually
fuse
After the sperm head binds tightly to the zona
pellucida, the acrosome enzymes digest and form a
pathway for the sperm through the zona pellucida.
The head, middle piece and usually the tail enters the
egg
Prevention of polyspermy depends on changes in the
egg plasma membrane when the sperm touches the
egg and depolarizes the egg plasma membrane; this
Tissue Stages
• Early gastrula stage- inward movement
(invagination) of the blastula wall to form a
gastrula of two to three primary germ layers
–Outer layer of cells to become ectoderm- the
beginnings of the epidermis, epithelial lining of mouth
and rectum, and the nervous system
–Inner layers become endoderm- beginnings of the
lining of the digestive and respiratory tract, and
glands
–Pore created by the inward movement (invagination)
of the blastopore
Cellular Stages of Development
• An organism is an embryo during the first
stages of development.
• After fertilization, a zygote undergoes
cleavage, cell division without growth.
• DNA replication and mitosis occur repeatedly,
cells get smaller with each division.
• A cavity called the blastocoel develops
forming a hollow ball called the blastula
24
• Late gastrula stage- middle dermal layer
forms called mesoderm
–Mesoderm is two layered and the space between
is called coelom that will now contain body organs
–Mesoderm gives ride to skeleton, dermis, muscles,
excretory system, reproductive system,
• Germ layers later fuse to become organs
Organ Stages
• Mesoderm cells congregate into a line on the main
axis, forms dorsal notochord, later becomes
vertebral column
• Nervous system develops from midline ectoderm
– Ectoderm cells fuse to form neural plate
– Folds in on itself to form neural tube
– Now the embryo is called a neurula!
– Neural tube grows brain on one end and rest becomes
spinal cord
• The rest of midline mesoderm two masses of tissue,
these form into segmental muscles, and the
vertebral bones in vertebrates
Stages
of
Birth
When fetal brain matures, androgens are released.
Placenta uses androgens as precursors for estrogens that
stimulate the production of prostaglandin and oxytocin.
estrogen, oxytocin, prostaglandin cause uterus to contract
and expel fetus.
Positive feedback: mechanism that brings about an ever
greater change in the same direction. Baby’s head presses
on cervix due to contractions and signals are sent to brain.
Signals cause pituitary gland to release oxytocin. As
oxytocin increases, so do contractions until birth occurs.
Process of birth (parturition) has 3 stages: dilation of cervix, birth
of the baby, and expulsion of the placenta. Initiated by
prostaglandins in humans.
positive feedback loop w/ oxytocin
Embryonic Development
An organism is called an embryo during the first
stages of development.
The cellular stages of development are (1) cleavage
resulting in a multicellular embryo and (2) formation of
the blastula.
Cleavage is a cell division without growth. It increases
only the number of cells.
Morula ball of cells, a result of cleavage. Then
continues to divide to form a blastula, or a hollow ball
of cells that have a fluid-filled cavity called blastocoel.
Embryonic Development
Covers events from conception (fertilization followed
by implantation) to birth (parturition).
Human development is divided into embryonic and
fetal development
The embryonic period, months 1 and 2 of
pregnancy, is when the major organs are formed
Fetal development is during months 3-9, when
organ systems are refined.
Embryonic development
Development can also be divided into trimesters
First trimester: embryonic and early fetal
development occurs
Second trimester: development of organs and
organ systems; fetus is distinctly human at the end
of the second trimester
Third trimester: fetus grows rapidly and organ
systems become functional
Structure and Function of
Placenta
Placenta begins formation once the embryo is fully
implanted. Provides gas, nutrient and waste
exchange.
Chorionic vill are treelike extensions of the chorion
Chorionic villi project into the maternal tissues.
Later, the chorionic villi disappear in all areas except
where the placenta develops.
Exchange of molecules between the fetal and
maternal blood takes place across the walls of the
chorionic villi.
By the tenth week, the placenta is fully formed and has already
begun to produce progesterone and estrogen.
Due to the negative feedback control by the
hypothalamus and anterior pituitary, no new follicles
mature. They maintain the lining of uterus and there is no
menstruation during pregnancy.
Exchange of molecules between the fetal and maternal blood takes
place across the walls of the chorionic villi. CO2 and wastes move
across from fetus; O2 and nutrients flow from the menstrual side.
The umbilical cord stretches between the placenta and fetus.
Human chorionic gonadotropin (HCG): produced by
the placenta, which surrounds the embryo.
Maintains the corpus luteum that surrounds the
egg until the placenta begins to produce its own
progesterone and estrogen. Maintains the uterine
lining to provide a place for uterine development
until placenta eventually forms.
Hormone detected in pregnancy tests, since it’s
present in the mother’s blood and the urine as
soon as 10 days after conception
Aminion surrounds the embryo and cushions it with
amniotic fluid to insulate against thermal changes and
protect it from harm.
Fig. 42.15
• 1.
Stages
of
Birth
When the fetal brain matures, the hypothalamus
causes the pituitary to stimulate the adrenal cortex so
that androgens are released.
• 2. The placenta uses androgens as precursors for
estrogens that stimulate the production of
prostaglandin and oxytocin.
• 3. The hormones estrogen, prostaglandin, and
oxytocin all cause the uterus to contract and expel the
fetus.
• 4. The process of birth (parturition) has three stages:
dilation of the cervix, birth of the baby, and expulsion
• The expulsion stage lasts 2-60 minutes.
Expulsion
• Contractions last 50-90 seconds and they are 1-2 minutes
apart.
• Expulsion ends when the baby is pushed through the vagina.
• A baby is born with its umbilical cord still attached
• The birth of the baby is followed by the delivery of the
placenta (the afterbirth)