Bio11 schedule
Lecture: Reproductive system Lecture exam 2 - Thursday Feb 24
Males & Females Embryonic Development Family planning HIV/AIDS
Posted: Your total points so far (your “grade” in class)
Ch 16 Reproductive System
Same format as before Covers Ch 5-8, 11-15 Study guide is posted
Last day to drop with a “W” is this Fri 2/25
Extra credit is due Thur Mar 3
The male reproductive system
Designed for the continuous production of a large number of sperm Produces testosterone, the male sex hormone
Sperm cells
Formation of sperm
The testes
Highly specialized for their role in fertilization Head: contains the nucleus Acrosome: contains enzymes to digest a passage to the egg Mitochondria: function? Tail: for movement
Spermatogenesis
produce sperm the hormone testosterone
Sperm do not complete their development at body temp (37°C) So the testes are outside of the body in the scrotum
The testis is packed with tightly coiled seminiferous tubules Sperm production, or spermatogenesis, takes place inside the tubules
Spermatogenesis begins in germ line cells on the outside of the tubule
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Meiosis: review
Spermatogenesis
Germ line cells in the seminiferous tubules undergo meiosis to form sperm
Germ line cell is diploid DNA is replicated Two cell divisions
The result?
Are sperm haploid or diploid?
They are released into the seminiferous tubule Adult males produce several hundred million sperm each day
Sperm cells are made in the testis Develop motility in the epididymis Delivered to the vas deferens When sperm is ejaculated, it travels from the vas deferens to the urethra
4 haploid daughter cells
Sperm leave the penis in a fluid called semen Various glands (seminal vesicle, prostate gland and Cowper’s gland) add fluids which help nourish the sperm
Hormones control the male reproductive system
The penis contains 3 long cylinders of spongy tissue It is designed to inflate
Nerve impulses cause the blood vessels leading into this tissue to expand Blood collects in the spongy tissue and causes the penis to become erect and rigid
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Spermatogenesis
Sperm delivery system
Meiosis I and Meiosis II.
Produces gametes
Spermatogenesis
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FSH
LH
The pituitary gland secretes 2 hormones, FSH and LH FSH stimulates sperm formation LH stimulates the testis to produce testosterone
Continued stimulation is required for ejaculation
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Testosterone
The female reproductive system
Develops male sex characteristics
Enlarges the sex organs Body hair, beard Voice change
Designed to
Develops sexual function
Sex drive (libido) Sperm maturation
Produce 1 egg each month Prepare the uterus for implantation of the fertilized egg
Ovulation
Stimulates bone and muscle growth
Anatomy of the female reproductive system
The eggs, or ova, mature in the ovaries The fallopian tubes transport egg to the uterus The uterus is lined with epithelial tissue called the endometrium
The Female Reproductive Cycle
The female reproductive cycle is actually two cycles in one:
The ovarian cycle
the surface of the endometrium is shed during menstruation
the uterus narrows to a muscular “neck” called the cervix The vagina leads from the uterus to the external genitalia
Growth and release of 1 egg each month Coordinated by FSH and LH
The menstrual cycle
prepares the uterus for possible implantation of an embryo. Coordinated by estrogens and progesterone
Ovulation – The ovarian cycle
only 1 egg matures each month
Eggs develop from cells called oocytes During each reproductive cycle, one (usually) of the oocytes matures
Ovulation: the mature follicle discharges the egg The egg is swept up into the Fallopian tube
Only ~400 oocytes mature and are ovulated in a woman’s lifetime Ovary and Fallopian tube
where fertilization may occur
Ovary and Fallopian tube
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FSH and LH coordinate the ovarian cycle
FSH and LH coordinate the ovarian cycle FSH
FSH
FSH stimulates the growth and maturation of a follicle The follicle cells secrete estrogen into the bloodstream
FSH and LH coordinate the ovarian cycle FSH
Pituitary
Formation of the corpus luteum Secretion of progesterone and estrogens
If the egg is not fertilized, the corpus luteum breaks down
FSH 28_24a
Estrogen levels peak at 12 days this causes LH levels to surge
and stimulates ovulation at 14 days
The mature follicle bursts and releases an egg
The uterine (menstrual) cycle
LH
LH (luteinizing hormone) stimulates
FSH and LH
FSH and LH
LH
Rising levels of progesterone and estrogens promote thickening of the endometrium When the corpus luteum breaks down → drop in levels of these hormones Endometrium begins to shed – menstruation
Female reproductive cycle
Ovary
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FSH, LH Negative feedback
Uterus
Estrogen Progesterone Menstrual cycle
Ovarian cycle
Time
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Estrogens have several important functions
Develop and maintain female reproductive structures, secondary sex characteristics, and the breasts Increase protein synthesis Preserve bone density Regulate synthesis of cholesterol by liver
Embryonic Development
It all starts with fertilization
The process of fertilization Only one sperm reaches the egg
Copulation releases hundreds of millions of sperm into the vagina Only a few hundred survive the trip to the egg Only one will fertilize it. Figure 26.13
The egg’s journey
Fertilization takes place in the Fallopian tube The fertilized egg begins mitosis – a series of cell divisions called cleavage It eventually forms a ball of cells called a blastocyst which implants in the lining of the uterus
The blastocyst
Implantation occurs at day 7 The inner cell mass forms the developing embryo
The outer cell layer (trophoblast) becomes part of the placenta
These are pluripotent stem cells – they give rise to all types of cells in the body Provides nutrients and oxygen to the embryo
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What prevents menstruation?
The implanted embryo secretes a hormone, human chorionic gonadotropin (hCG) hCG tells the corpus luteum to continue secreting estrogen and progesterone
Stages of early development
Fertilization Cleavage Implantation of the blastocyst (day 7)
Neural tube forms (days 16-25)
Organogenesis (4 weeks)
This prevents menstruation
Because hCG comes from the embryo and not from the mother, pregnancy tests measure hCG
the first tissue to develop Formation of body organs
From embryo to fetus 1 4:18
http://www.youtube.com/watch?v=0xvJ-NNuR6M
Fetal Development: organogenesis
The process of forming body organs begins in the 4th week of pregnancy
A month-old embryo
This is a crucial time Most spontaneous abortions (or miscarriages) occur during this period
Alcohol use during pregnancy is one of the leading causes of birth defects, producing fetal alcohol syndrome
Brain and spinal cord have begun to take shape Four stumpy limb buds A short tail Looks like most month-old vertebrate embryos
Human embryo at 4 weeks
Programmed cell death –
Fetal Development: the first trimester
a key developmental process
Development is essentially complete at the end of the third month of pregnancy
Certain tissues produced during embryonic development are destroyed– apoptosis Cells in the developing hands and feet are killed, separating the fingers and toes
All the major organs are present Arms and legs begin to move The developing human is now referred to as a fetus
Human fetus at 3 months
2 From embryo to fetus 3:20 http://www.youtube.com/watch?v=aw5v6_5GaLQ&NR=1
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Ultrasound imaging
By the end of the 1st trimester, the sex of the fetus can be determined by an ultrasound exam An ultrasound image is produced when highfrequency sound waves are bounced off the fetus
Fetal Development
Fetal Development
The third trimester is a period of rapid growth
The weight of the fetus doubles Brain and lungs complete development
The growing fetus is fed by the placenta which passes nutrients from the mother’s bloodstream into the fetal blood supply
But maternal and fetal blood don’t mix
Human fetus at 4 months
An organ unique to mammals Allows close contact between the bloodstreams of the developing fetus and mother The placenta supplies the fetus with oxygen and nutrients, and allows fetal Oxygen, waste to be disposed of via nutrients and hormones to the mother’s kidneys baby Placenta also synthesizes hormones required to maintain pregnancy
Wastes and CO2 from baby
Three stages of labor
Childbirth The birth of a child is brought about by a series of strong, rhythmic contractions of the uterus called labor Labor is induced by a strong surge of 3 hormones
During the 4th month, the bones enlarge Mother can feel baby kicking By the end of month 6, the fetus can survive outside the uterus with special medical care
The placenta
The second trimester is a time of growth
Dilation of the cervix
Delivery of the infant
Opens to a width of 10 cm (4 inches) Strong uterine contractions
Delivery of the placenta
The “afterbirth”
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Birth control
Family planning
Contraception methods differ in their effectiveness Most effective
Preventing pregnancy
Least effective
Sterilization (vasectomy, tubal ligation) IUD Implant Withdrawal Spermicides
See Birth control effectiveness chart on Planned Parenthood website
http://www.plannedparenthood.org/health-topics/birth-control//birth-control-effectiveness-chart-22710.htm
What is an IUD?
Sterilization
Intrauterine device IUDs are small, "T-shaped" devices inserted into a woman's uterus to prevent pregnancy. Effective for at least 5 years How Does an IUD Work?
vasectomy
tubal ligation
The implant
A matchstick-sized rod that is inserted in the upper arm Releases the hormone progestin and prevents ovulation It protects against pregnancy for up to 3 years.
Copper affects the motility of sperm, preventing fertilization. Also alters the lining of the uterus and prevents the fertilized egg from implanting in the uterus.
Other methods that use hormones to prevent ovulation
Hormone methods
Birth control Shot, Pill, Ring, Patch Breast feeding
The birth control shot contains progestin The pill, ring and patch contain both estrogen and progestin.
The hormone methods work by preventing ovulation
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How do these hormones prevent ovulation?
FSH
LH Negative feedback
Female sex hormones coordinate the reproductive cycle
Estrogen Progesterone
FSH and LH → Ovulation Estrogen and progesterone → prepare the uterine lining for implantation
Birth control pills contain estrogen and progestin
Turn off production of FSH and LH Prevent ovulation
Condoms
Breastfeeding
While a woman is continuously breastfeeding, her body does not make hormones that are necessary for ovulation Less than 1 out of 100 women who practice continuous breastfeeding perfectly will become pregnant. Using breastfeeding as birth control can be effective for 6 months
The Diaphragm
Condoms are thin latex or plastic sheaths that are worn on the penis during intercourse. Condoms prevent pregnancy by collecting semen when a man ejaculates. This keeps sperm from entering the vagina and “meeting” the egg. They also reduce the risk of sexually transmitted infections.
Recap: How different birth control methods work
Prevent ovulation
Hormone methods – Implant, birth control pill, shot, ring, and patch; Plan B; breast feeding
Prevent implantation of embryo
Block or kill sperm
Plan B (morning after pill)
What is Plan B?
IUD IUD, condom, diaphragm, spermicidal jellies
Sterilization Which of these prevent STIs? Which are the woman’s responsibility?
A shallow latex cup inserted into the vagina. When in place, it covers the cervix (the opening to the uterus) Diaphragms prevent pregnancy by keeping sperm from entering the uterus In order to be as effective as possible, the diaphragm is used with spermicide cream or jelly.
Emergency contraception Should be taken within 3 days after intercourse Plan B contains only progestin, a synthetic hormone used in birth control pills
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How does Plan B work?
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How does the pregnancy test work?
Stops ovulation may prevent fertilization and implantation But … Plan B will not work after the fertilized egg is implanted.
It measures hCG levels The embryo secretes human chorionic gonadotropin (hCG)
hCG
hCG comes from the embryo and not from the mother Excess hCG is excreted in the mother’s urine
HIV/AIDS The AIDS pandemic
The problem is massive
Speaking of STIs
What makes HIV so lethal?
The HIV retrovirus highjacks immune cells HIV infects and destroys the very cells that normally suppress viral attacks
the helper T cells of the human immune system
4th leading cause of death worldwide ~40 million people are infected 95% live in developing countries
HIV highjacks immune cells
Long incubation period
The victim feels healthy but is highly infectious
HIV binds to the plasma membrane of helper T cells Penetrates the cell Viral RNA is integrated into the cell genome Human helper T cells ‘manufacture’ the virus Infected cells are killed eventually HIV life cycle 3:10 http://www.youtube.com/watch?v=9leO28ydyfU&feature=related
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HIV budding from an immune cell in culture
Where is the virus?
The viruses bud so rapidly that the cell eventually lyses The number of helper T cells drops, and the body cannot fight off other infections These secondary infections cause AIDS
Acquired immune deficiency syndrome
Treating AIDS: Antiretroviral therapy (ART)
How is HIV transmitted?
Unprotected sexual intercourse
Heterosexual or homosexual
Direct contact with infected blood
blood is tested for HIV (not always in poor countries)
HIV can infect the fetus in utero, or during birth
Breast-feeding
Without treatment, rate of transmission is 25%
Risk of HIV infection 90% of HIV-positive people do not know they are infected
Long incubation period btwn infection and major illness Most people have no access to testing Stigma If there’s no treatment available, why get tested?
More than 25 drugs have been developed Usually given in a “cocktail” of 3 or 4 pills ART is costly, must be maintained every day for the rest of the patient’s life
Avoid developing resistance to drugs
Still no cure or vaccine for HIV
Prevention is key
Mother-to-child
Sharing needles Blood transfusions
HIV is found in all body fluids Only semen, blood, breast milk and vaginal discharge have enough virus to transmit HIV Saliva, tears and sweat do not
The virus is constantly mutating – a moving target
Pop quiz – Name the 3 main routes of HIV transmission
Sexual intercourse Blood or blood products Mother-to-child transmission
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