Download Reproduction(Day 1)

Reproduction(Day 1)
Raymundo Jaime
Jose Cuevas
Animal Reproduction
• Asexual reproduction
– Only one parent
– Efficient Strategy
- Although there is the advantage of this type of
reproduction is beneficial for certain animals that are unable to
look for mates and ideally “costs” the parent les energy and
time, the disadvantage is that there is a lack of genetic variation.
– Cnidarians (hydras) produce by budding
– Annelids (earthworms and sandworms) by
regeneration from fragments
• Fragmentation: the body of the parent breaks into
distinct pieces, each of which can produce offspring
• Regeneration: piece of a parent is detached and can
develop into a completely new individual
Animal Reproduction
• Flatworms, roundworms, crustaceans,
annelids, insects, fishes, lizards, and some
turkeys can reproduce parthenogenetically,
parthenogenesis is a modification of sexual
reproduction in which an unfertilized egg
develops into a complete individual
– 1.Facultative
– 2.Obligate
http://ferrebeekeeper.files.wordpress.com/2011/05/bbc_virgi
nshark_1.gif
Animal Reproduction
• Sexual reproduction
– Egg is fertilized by sperm of another
• Dioecious, two separate sexes
• Monoecism (hermaphroditic) have female and male
boy parts
– Sex reversal- coral reef fishes called wrasses; male has a
harem of several females, when the male dies, one of the
females become male.
Animal reproduction
• Animals produce gametes ( a mature male or
female germ cell possessing a haploid
chromosome) in specialized organs called
gonads
– Testes produce sperm
– Ovaries produce eggs
The egg is fertilized with the sperm, and can be
done in different forms, such a external fertilization
or through copulation
Animal Reproduction
Viviparous (producing living young instead of eggs)
– Placental mammals
» Placenta
Oviparous
– Animals that deposit an egg in the external environment
» larva
Ovoviviparous
– Animals that retain their eggs in some way and release young
able to fend for themselves
» Oysters
» Male sea horses
In vitro fertilization (IVF)
• The process by which an egg is fertilized by
sperm outside the body
• It involves monitoring the woman’s ovulatory
process, removing an ovum or ova (eggs) from
the ovaries and letting sperm fertilized them
in a fluid medium in a laboratory.
• Potential Risks and variation of views on IVF
SENSITIVE MATERIAL AHEAD
Human Male Reproduction
• The testes produce gametes
• A series of ducts store and transport the
sperm
• The accessory glands produce the fluid
portion of semen
• The penis transfers the sperm through
copulation to the female
• Hormones
Human Male Reproduction
Spermatogenesis
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter28/animation__
spermatogenesis__quiz_1_.html
• The basic function of spermatogenesis is to turn each one of the
diploid spermatogonium (tiny tubules containing diploid cells) into
four haploid sperm cells.
• This is accomplished through meiotic cell division
• FSH (secreted by the pituitary) stimulates primary spermatocytes
to undergo the first division of meiosis.
• LH (also secreted by the pituitary) stimulates the secretion of
testosterone by the testes
• Testosterone (secreted by interstitial cells) stimulates secondary
spermatocytes to develop into sperm.
Human Male Reproduction (testes)
• Leydig cells (interstitial cells)
– release the male sex hormones (Androgens)
• Germinal epithelium cells
– Wall of the seminiferous tube
– Place of sperm production
• Sertoli cells
– Nourish the developing sperm cell
– Called the “nurse” cell
• Developing spermatozoa (motile sperm cell)
Human Male Reproduction
Male Reproductive System
Organ
Function
Testes
Produce sperm and sex hormones
Epididymides (lies on the posterior aspect
of each testicule, connecting it to the vas
deferens)
Vasa deferentia
Sites of maturation and some storage of
sperm
Seminal vesicles
Prostate gland
Contribute fluid to semen (add nutrient
fluid to semen during ejaculation)
Contributes fluid to semen
Urethra
Conducts sperm (and urine)
Bulbourethral glands
Contribute fluid to semen
Penis
Organ of copulation
Conduct and store sperm
Sperm
Testosterone
• Three roles of testosterone in males
– Development of male genitalia (in the fetal stage)
– Maintenance of sex drive and happiness
– Development of male secondary sexual
characteristics at puberty (growth of facial hair,
deepening of the voice, initiation of sperm
production)
Day Two
Spermatogenesis
Human Female Reproduction
• The females' reproductive system is adapted to
produce eggs, receive the penis and sperm, and
protect and nourish the embryo during and after
pregnancy
• The ovaries produce gametes and sex hormones
• The oviducts transport the secondary oocyte
• The uterus incubates the embryo
• The vagina receives sperm
• The vulva are external genital structures
• The breasts function in lactation
Female Reproductive System
Female Reproductive Organs
Organ
Function
Ovaries
Produce egg and sex hormones
Oviducts (fallopian tubes)
Conduct egg; location of fertilization
Uterus (womb)
Houses developing embryo and fetus
Vagina
Receives penis during copulation and
serves as birth canal
Ovary
• Location: on the lateral wall of the pelvis
• Oocyte: The oocyte is a female germ cell that is not yet
ready for fertilization. The oocyte matures into an
ovum (egg) that will be released during ovulation.
• Germinal epithelium: layer of simple epithelial cells
covering the ovary
• Primary follicles: is an immature follicle consisting of
the oocyte surrounded by a single layer of cells
• Mature follicles: a follicle that is ready for ovulation
• Secondary Oocyte: will be produced when the primary
oocyte completes meiosis. Will talk about later in
menstruation cycle
Ovary
Oogenesis
Egg
Spermatogenesis vs. Oogenesis
Gametes
• Spermatogenesis:
– Four are made from a spermatogonium
– continuous production
– Although from puberty to old age sperm cells are
constantly being engendered, the production is
subject to extreme fluctuation regarding both
quantity and quality.
• Oogenesis:
– Only one made from primary oocyte, once a month
– Exhaustion of the supply at menopause
Menstrual Cycle
• http://www.youtube.com/watch?v=nwo9KSNwSjE
• The menstrual cycle is the scientific term for the
physiological changes that occur in fertile women and
other female primates for the purposes of sexual
reproduction.
• It is commonly divided into three phases: the follicular
phase, ovulation, and the luteal phase.
- It begins with the formation of the corpus luteum
(the cells that surrounds the egg while it was in the
ovary) and ends in either pregnancy or luteolysis
(structural and functional degradation of the corpus
luteum)
Hormones During the Menstrual Cycle
Hormone
Role in the Menstrual Cycle
Follicle Stimulating Hormone (FSH)
Stimulates the follicle to produce mainly
estrogen, and development of an egg
Luteinizing Hormone (LH)
Stimulates the corpus luteum to produce
mainly progesterone and causes ovulation
Estrogen
Causes the repair of the lining of the
uterus after the last menstruation
Progesterone
Causes the lining of the uterus to get
thicker ready for the fertilized egg
Control of Human Reproduction
• Intrauterine devices
– Mechanically prevent implantation, and can contain progesterone to prevent
ovulation, prevent implantation and thicken cervical mucus
• Hormone Skin Patches
– Same as oral contraceptives
• Depo-Provera
– Shot of progesterone
• Diaphragm and Spermicidal jelly
– Latex cup that covers the cervix
• Female and Male Condoms
• Implant
– Implanting of progesterone under skin
• Birth Control
– Combined action of estrogen and progesterone
• “Morning after” pill
Reproductive technologies
• Artificial Insemination by Donor (AID)
– Sperm is placed in the vagina by a physician
• In Vitro Fertilization (IVF)
– “In Glass” fertilization
• Gamete Intrafallopian Transfer (GIFT)
– Exactly the same of IVF, but oocytes and sperm are
placed in the oviducts immediately after being
brought together
• Surrogate Mother
• Intracytoplasmic Sperm Injection (ICSI)
– Single sperm is injected into an oocyte
Acquired Immunodeficiency Syndrome
(AIDS)
• Cause
– Human Immunodeficiency Virus (HIV)
– Attacks helper T cells
• Symptoms
– Categories A, B, and C
• A- last about a year, no symptoms but still passes it on
• B- may last six to eight years, lymph nodes swell, and the person may experience weight
loss, night sweats, fatigue, fever, and diarrhea
• C- full-blown AIDS, nervous disorders and the development of an opportunistic disease,
such as an unusual type of pneumonia or skin cancer
• Transmission
– Sexual contact
– Needle-sharing
– Transfusions of infected blood
• Treatment
– No cure
– Drug cocktail
Other STDs
•
Genital Warts
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Caused by the human papillomaviruses (HPVs)
Flat or raised warts on the penis and foreskin of males and the vaginal orifices and cervix of females
No cure, but treated by surgery, freezing, application of an acid and lasers
Vaccination for most common HPV has been made
Genital Herpes
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Caused by herpes simplex virus
Type one causes cold sore and fever blisters
Type two cause genital herpes
Crossover infections can happen
Blisters on genitals
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Can be accompanied by fever, pain on urination, swollen lymph nodes, and a copious discharge in the ladies
Blisters rupture and form ulcers
Hepatitis
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Several types, all infect the liver and can cause death and cancer
Hepatitis A is caused by drinking sewage-contaminated water, sexually transmitted through oral or anal
contact
Hepatitis B is spread by the same manner as AIDS, and is more infectious
Hepatitis C is called posttransfusion hepatitis but can be spread by sexual contact
Vaccine for B, none for C
Other STDs (cont)
•
Gonorrhea
– Caused by the bacterium Neisseria gonorrhoeae
– Typical symptoms for males are pain upon urination and a thich, greenish yellow urethral
discharge
– Latent infection leads to pelvic inflammatory disease (PID)
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Syphilis
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Caused by the bacterium Treponema palidum
Primary stage- a hard chancre (ulcerated sore with hard edges) appears
Secondary stage- a rash appears all over the body
Tertiary stage- affects the cardiovascular and/or nervous system
Infected person may become mentally retarded, become blind, walk with a shuffle, or show
signs of insanity
Bacterial Vaginosis
Trichomoniasis
Chlamydia
– Caused by the bacterium Chlamydia trachomatis
– After about 8-21 days of infection, men may experience a mild burning sensation on urination
and a muciod discharge
– Women have a vaginal discharge alone with the symptoms of a urinary tract infection
GRAND FINALE
Fertilization
• The union of a sperm and an egg to form a
zygote.
• Egg is covered by sperm, secret enzymes
weaken the corona radiata
• After weaken enough, they squeeze through
and then bind to the zona pellucida
• Acrosome Reaction:
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Acrosome: organelle that develops over the anterior half of the head in sperm cells. (cap-like
structure)
The acrosome release digestive enzyme that forge a pathway for the sperm through the zona
pellucida to the oocyte plasma membrane
Fertilization (cont)
• When the sperm is attached too the oocyte,
events happen to prevent polyspermy
• The oocyte’s plasma membrane depolarize
and change in charge, “fast block”
• Vesicles in the oocyte called cortical granules
secrete enzymes that turn the zona pellucida
into an impenetrable fertilization membrane,
“slow block”
Fertilization (cont)
• Last events lead to the formation of the diploid zygote
• Microvilli from the plasma membrane of the oocyte
bring the sperm in
• Sperm nucleus release its chromatin
– Reforms into chromosomes enclosed within the sperm
pronucleus
• Secondary oocyte completes meiosis
– Chromosomes are also enclosed in a pronucleus
• Singular nuclear envelope soon surrounds both sperm
and egg pronuclei
• The two haploid sets of chromosomes share the first
spindle apparatus of the fertilized egg, called a zygote
Fertilization, simplified
1. Sperm makes its way through the corona radiata
2. Acrosomal enzymes digest a portion of zona
pellicuda
3. Sperm biinds to and fuses with oocyte plasma
membrane
4. Sperm nucleus enters cytoplasm of oocyte
5. Cortical granules release enzymes; becomes
fertilization membrane
6. Sperm and egg pronuclei are enclosed in a
nuclear envelope
Embryonic Development
• Cellular stages of development
– Cleavage resulting in a multicellular embryo
• Cleavage is cell division without growth
– Only increases the number of cells, does not change the
original volume of the egg’s cytoplasm
– Formation of the blastula
– Order of development
• Zygote
• Morula (ball of cells)
• Blastula (hollow ball of cells having a fluid filled cavity
called a blastocoel)
Embryonic development
• Tissue stages of development
– The early gastrula
• Begins when cells begin to push, invaginate, into the
blastocoel, creating a double layer of cells
• Has two layers of cells
– Ectoderm- outer layer of cells
– Endoderm- inner layer of cells
– The pore made by invagination is the blastopore
– The last gastrula
• Gastrulation is not complete until three layers of cells that
will develop into adult organs are produced
• The late gastrula has a middle layer of cells called the
mesoderm
Embryonic Development
• Organ stage of development
• The organs of an animal’s body develop from the three embryonic germ
layers
– The mesoderm cells lie along the main longitudinal axis of the animal and
unite to form a dorsal supporting rod called the notochord
• In vertebrates, the notochord is later replaced by the vertebral column
– The nervous system develops from the midline ectoderm
• Thickening of cells begins, called the neural plate
• Then neural folds develop on either side of a neural groove, becomes the neural tube
– Embryo is now called a neurula
– Midline mesoderm cells that did not contribute to the formation of the
notochord now become two longitudinal masses of tissue
– Form into somites, give rise to muscles associated with the axial skeleton and
the vertebrate
– Primitive gut tube is formed by endoderm as the body itself folds into a tube
• Heart also begins as a simple tubular pump
Developmental Processes
• Development requires:
– Growth
– Cellular Differentiation
• Cells become specialized in structure and function
– Morphogenesis
• The shape and form of the body is produced
• Includes pattern formation, how tissues and organs are
arranged in the body
• Apoptosis is important to pattern formation
Cellular Differentiation
• Cytoplasmic Segregation
– Maternal determinants are in the egg, influence the
course of developments
• Induction
– The ability of one embryonic tissue to influence the
development of another tissue
– Example, experiment was done with notochord tissue
being cut out and transplanted into different places
• Cut out and transplanted to the belly region, and the neural
tissue began to grow around it
Human Embryonic and Fetal
Development
• Separated into two different time periods
– Embryonic period
• Months 1 and 2
• Major organs are formed
– Fetal development
• Months 3 to 9
• Organs are defined
Embryonic Period
• First Week
– Fertilization occurs in the upper third of the oviduct (fallopian tube)
– Cleavage begins 30 hours after fertilization and continues as the embryo
passes through the oviduct to the uterus
– Third day, embryo reaches uterus and is now a morula
– On fifth day, morula transformers into the blastocyst
• Blastocyst is a fluid-filled cavity with a single layer of outer cells called the trophoblast
and a n inner cell mass
• Trophoblast serves to provide nourishment for the embryo, Later gives rise to the
chorion, one of the extraembryonic membranes that helps gas exchange, along with the
amnion (membrane around the fetus that contains the protective amniotic fluid), the
allantois (collects nitrogenous waste), and the yolk sac (provides nourishment)
• Second Week
– Embryo begins implanting in the wall of the uterus
– The trophoblast secretes enzymes to digest away some of the tissue and blood
vessels of the endometrium of the uterus
– Inner cells mass detaches itself and forms the yolk sac and the embryonic disk
– Gastrulation occurs during this week, inner cells flatten to embryonic disk
Basic Summary of beginning
1.
2.
3.
4.
5.
6.
Ovulation
Fertilization
Cleavage
Morula
Early blastocyst
Implantation
Human Chorionic Gonadotropin (HCG)
• Also secreted by the trophoblast in the second
week
• Basis for the pregnancy test
• Serves to maintain the corpus luteum past the
time it usually disintegrates
– Endometrium is maintained and mensuration
does not occur
Embryonic Period
• The Third Week
– Nervous system is the first organ system to become visually evident
• After the notochord is replaced by the vertebral column, the nerve cord is called the
spinal cord
– Development of the heart begins in third week and continues onto the fourth
• Begins with right and left heart tubes, when they fuse the heart begins to pump blood
• The Fourth and Fifth Weeks
– Bridge of mesoderm called the body stalk connects the tail end of the embryo
with the chorion
– The allantois is contained within the stalk; its blood vessels become the
umbilical blood vessels
– The umbilical cord, which connects the developing embryo to the placenta is
fully formed after the body stalk moves anteriorly by constriction after the
head and the tail lift up
– Limb buds appear, the head enlarges, and the sense organs become apparent
• Sixth through Eighth Weeks
– Becomes easily recognizable as a human
Placenta
•
Function and structure
– The placenta is a disc-shaped structure that nourishes the developing embryo
– It is formed from the development of the trophoblast upon implantation and eventually
invades the uterine wall
– The umbilical cord connects the fetus to the placenta and maternal blood pools
– Chorionic villi extend into these spaces and facilitate the exchange of materials between the
maternal blood and fetal capillaries
– Nutrients, oxygen and antibodies will be taken up by the fetus, while carbon dioxide and waste
products will be removed
– The placenta is expelled from the uterus after childbirth
– Materials are exchanged between t eh maternal and fetal blood in the placenta
•
Hormonal Role
– The placenta also takes over the hormonal role of the ovary (at around 12 weeks)
– Estrogen stimulates growth of the muscles of the uterus and the development of the
mammary glands
– Progesterone maintains the endometrium, as well as reduces uterine contractions and
maternal immune response (no antibodies against fetus)
– Both estrogen and progesterone levels drop near time of birth
Fetal Position
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Fetal development is marked by an extreme increase in size
Weight grows from 28g to 3kg
Fetus grows to 50 cm in length
Genitalia appear in the third month
Eyebrows, eyelashes, fingernails, toenails put defining touches on
the head, hands, and feet
The skin is growing so fast that it wrinkles
The fetus is supported and protected by the amniotic sac and
amniotic fluid
After 16 weeks, the fetal heartbeat is heard through a stethoscope
Weight gain during the last couple of months increases the
likelihood of survival
Birth
• Hypothalamus causes the pituitary to stimulate the adrenal
cortex so that androgens are release into the bloodstream
• Placenta uses androgens as a precursor for estrogen,
hormones that stimulate the production of prostaglandin (a
molecule produced by many cells that acts as a local
hormone) and oxytocin
• Oxytocin inhibits progesterone, which was inhibiting
uterine contractions
• Oxytocin also directly stimulates the smooth muscle of the
uterine wall to contract, initiating the birthing process
• The contraction of the uterine wall causes further
stretching, which triggers more oxytocin to be released
(causing even more contraction)
Process of Birth
• First stage
– The cervix dilates to allow passage of the baby’s
head and body
– Amnion usually bursts about this time
• Second stage
– The baby is born and the umbilical cord is cut
• Third stage
– The placenta is delivered
Now you know how babies are
made and where they come from