Bio11 schedule. Ch 16 Reproductive System. The male reproductive system. Sperm cells. Formation of sperm. Spermatogenesis

Bio11 schedule   Lecture: Reproductive system Lecture exam 2 - Thursday Feb 24     Males & Females Embryonic Development Family planning HIV/...
Author: Mervin Lawrence
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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 

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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


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?

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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


Spermatogenesis 

Sperm delivery system

Meiosis I and Meiosis II.

Produces gametes





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



The female reproductive system

Develops male sex characteristics

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Enlarges the sex organs Body hair, beard Voice change

Designed to  

Develops sexual function

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Sex drive (libido) Sperm maturation

Produce 1 egg each month Prepare the uterus for implantation of the fertilized egg


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


FSH and LH coordinate the ovarian cycle

FSH and LH coordinate the ovarian cycle 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


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 (luteinizing hormone) stimulates 

FSH and LH

FSH and 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



FSH, LH Negative feedback


Estrogen Progesterone Menstrual cycle

Ovarian cycle



Estrogens have several important functions 

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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

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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


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

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the first tissue to develop Formation of body organs

From embryo to fetus 1 4:18

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


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”


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 

What is an IUD?


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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? 


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


How do these hormones prevent ovulation? 


 

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


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

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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


How does Plan B work?  


 

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


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


Without treatment, rate of transmission is 25%

Risk of HIV infection 90% of HIV-positive people do not know they are infected 

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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