Friday, May 9, 2008

Chapter 16 & 17

Chapter 16

Reproductive System

Chapter Concepts

  1. Human life Cycle
  2. Male Reproductive System
  3. Female Reproductive System
  4. Female Hormone Levels
  5. Control of Reproduction
  6. Sexually Transmitted Diseases
  7. Picture References

  1. Human life Cycle
    • The reproductive system is quite different in male and females. Puberty is the sequence of events by which a child becomes a sexually competent young adult.
    • Does not begin fully until puberty is complete. Sexual maturity occurs between the age of 11-13 in girls, and 14-16 in boys. At the completion of puberty both boys and girls are capable of producing children.
    • Mitosis and Meiosis

o The two type of cell division in the human life cycle are mitosis and meiosis. Mitosis is duplication division (number of chromosomes stays the same). Mitosis is the type of cell division that takes place during growth and repair of tissues. Meiosis is reduction division (number of chromosomes is reduced).

o The mother chromosomes contribute 23 to the new individual and the father also contributes 23.

o Meiosis occurs in the male’s testes and females ovaries.

Mitosis and Development

  1. Male Reproductive System
    • The external genitals of males are:

o The penis (organ of sexual intercourse)

o The scrotum (contains the testes)

  • Sperm produced by the testes mature within the epididymis, which is a tightly coiled duct laying just outside each testis.
  • When sperm leave an epididymis they enter a vas deferens also called the ductus deferens, where they may also be stored for a time. It is where mature sperm are stored.
  • The ejaculation ducts enter the urethra.
  • When sperm leaves the penis in a fluid its called semen.


The Male Reproductive System

    • Orgasm in Males

o The penis is the male organ of sexual intercourse.

§ Circumcision, the surgical removal of the foreskin, is usually done soon after birth.

o During sexual arousal, autonomic nerves release nitric oxide, NO.

o Stimulus leads to the production of cGMP which causes the smooth muscle of incoming arterial walls to relax and the erectile tissue to fill with blood.

o The veins that take blood away from the penis are compressed, and the penis becomes erect.

o Erectile dysfunction exists when the erectile tissue doesn’t expand enough to compress the veins.

    • Male Gonads, the Testes
    • The testes, which produce sperm.
    • The testes begin their development inside the abdominal cavity but descend into the scrotal sacs during the last two months of fetal development.
    • Spermatogenesis, occurring in seminiferous tubules of the testes, produces sperm.
    • Mature sperm have three distinct parts:

o Head, middle piece and a tail.

  • Mitochondria in the middle piece provide energy for the movement of the tail, which is a flagellum.
  • The head contains a nucleus covered by a cap called the acrosome, which stores enzymes needed to penetrate the egg.
  • A normal human male contains several hundred million sperm but only one sperm enters an egg.
  • Does not usually live more than 48 hours in the female genital tract.
  • Cells that lie between the seminiferous tubules secrete the male sex hormones, the androgens they are called interstitial cells.


Testis and Sperm

    • Hormonal Regulation in Males

o The hypothalamus has ultimate control of the testes’ sexual function because it secretes a hormone called gonadotropinreleasing hormone (GnRH) that simulates the anterior pituitary to secrete the GnRH.

o Testosterone, the main sex hormones in males are essential for the normal development and functioning of the organs.

o Hormonal regulation, involving secretions from the hypothalamus, the anterior pituitary, and the testes, maintains a fairly constant level of testosterone.

o FSH from the anterior pituitary promotes spermatogenesis.

o LH from the anterior pituitary promotes testosterone production by interstitial cells.

  1. Female Reproductive System
    • The female gonads are paired ovaries that lie in shallow depressions, one on each side of the upper pelvic cavity.
    • The ovaries produce eggs and the female sex hormones, estrogen and progesterone.
    • The Genital Tract

o Oviducts, also called the uterine or fallopian tubes extend from the uterus to the ovaries.

o Zygote diploid cell formed by the union of sperm and egg; the product of fertilization.

o Implantation the embryo embeds in the uterine lining

The Female Reproductive System

o The cervix contains opening to uterus

o Development of the embryo and fetus normally takes place in the uterus.

o The vagina is the organ of sexual intercourse and the birth canal in females.

    • Orgasm in Females

o Orgasm is female culminates in uterine and oviduct contractions.

o Orgasm occurs at the height of the sexual response.

  1. Female Hormone Levels
    • Ovarian Cycle: Non-pregnant

o An ovary contains many follicles, and each one contains an immature egg, called an oocyte.

o A female is born with as many as two million follicles but is reduced to 300,000-400,000 by the time of puberty.

o A woman produces only one egg per money during her reproductive years.

o As the follicle matures during the ovarian cycle, it changes from a primary to a secondary to a vesicular follicle.

o Oogenesis is a production of an egg in females by the process of meiosis and maturation.

o Ovulation is a release of a secondary oocyte from the ovary; if fertilization occurs, the secondary oocyte becomes an egg.

o The corpus luterum secretes progesterone and some estrogen.

Ovarian Cycle

· Estrogen and Progesterone

o Affect not only the uterus but other parts of the body as well.

o Estrogen is responsible for sex characteristics in females (body hair and fat distribution).

§ Females are more rounded than male

o The development to produce milk following pregnancy.

o Menopause, the period in a woman’s life during which the ovarian cycle ceases, likely occurs between ages 45-55.

§ Menstruation becomes irregular.

§ Completed menopause until menstruation is absent for a year.

· Uterine Cycle: Non-pregnant

o The female sex hormones, estrogen and progesterone, have numerous functions.

o Uterine cycle is monthly occurring changes in the characteristics of the uterine lining (endometrium).

o 28 day cycle are divided:

§ Days 1-5, a low level of estrogen and progesterone. Day one of the cycle, a flow of blood and tissues, known as the menses, passes out of the vagina during menstruation.

§ Days 6-13, increased production of estrogen by a new ovarian follicle in the ovary causes the endometrium to thicken and become vascular and glandular. This cycle is called the proliferative phase.

§ Day 14, ovulation occurs.

§ Days 15-28, increased production of progesterone by the corpus luterum in the ovary causes the endometrium of the uterus to double or triple in thickness and the uterine glands to mature. This is called the sercetory phase.

Female Hormone Levels

· Fertilization and Pregnancy

o During unprotected sexual intercourse, sperm will likely reach the egg located following ovulation.

o Only one sperm fertilizes an egg and then it becomes a zygote.

o The placenta, which sustains the developing embryo and later the fetus, starts from both maternal and fetal tissues.

o The embryo implants itself in the thickened endometrium.

o The placenta produces HCG (human choronic gonadotropin), which maintains the corpus luterum in the ovary.

§ A pregnancy test detects HCG

o Menstruation does not occur during pregnancy (a skipped period is a sign of pregnancy).

· Birth control pill is a way to not get pregnant.

· Birth control pill thicken the cervical mucus, preventing sperm to enter the uterus.

· When taking birth control pills the hormones that are in the pill feedback to inhibit the hypothalamus and the anterior pituitary; so no new follicles begin in the ovary.

  1. Control of Reproduction

· Birth control methods are used to regulate the number of children an individual or couple will have.

· Birth Control Methods

Birth Control devices

o The most reliable method of birth control is ABSTINENCE

o Contraceptives are medications and devices that reduce the chance of pregnancy.

§ IUD (intrauterine device) – a small piece of molded plastic that is inserted into the uterus.

§ Diaphragm- is a soft latex cup with a flexible rim that lodges behind the pubic bone and fits over the cervix.

§ Female condom- consists of a large polyurethane tube with a flexible rind that fits onto the cervix.

§ Male condom- is most often a latex sheath that fits over the erect penis.

§ Contraceptive implants- utilizes synthetic progesterone to prevent ovulation by disrupting the ovarian cycle.

§ Contraceptive injections- are available as progesterone only or a combination of estrogen and progesterone. Each injection can vary from three to a few weeks.

§ Contraceptive vaccines- are now being developed. A vaccine intended to immunize women against HCG, the hormone so necessary to maintaining the implantation of the embryo.

§ Vasectomy- consists of cutting and sealing the vas deferen on each side so that the sperm are unable to reach the seminal fluid that is ejected at the time of orgasm.

§ Tubal ligation- consists of cutting and sealing the oviducts. Pregnancy rarely occurs because the passage of the egg through the oviducts has been blocked.

· It is view a vasectomy and tubal ligation as permanent.

· Even following successful reconnection, fertility is usually reduced by about 50%.

§ Morning after pill, or emergency contraception, is a medication that will prevent pregnancy after unprotected intercourse.

· Infertility

· Infertility is a failure of a couple to achieve pregnancy after one year of regular, unprotected intercourse.

· Cause of infertility:

o Cause in male is low sperm count or a large amount of abnormal sperm. Abnormal sperm can be due to environmental influences:

§ Alcohol

§ Smoking

§ Sitting around at computer or driving, the testes temperature remains too high for adequate sperm production.

o Body weight in women appears to be the most significant factor in causing female infertility.

o Sometime medication can correct infertility.

· Assisted reproductive technologies

· Artificial insemination by donor (AID)- during artificial insemination, sperm is placed in the vagina by a physician. If partner has a low sperm count it is collected till it can be implanted.

· In vitro fertilization (IVF)- conception occurs in laboratory glassware. About two or three days the embryo is implanted in the women’s uterus that is in the secretory phase of her uterine cycle.

· Gamete intrafallopian transfer (GIFT)- the term gamete refers to a sex cell, either a sperm or an egg. Used the same way as IVF but are placed immediately.

· Surrogate mother- woman are contracted and paid to have babies. The contracting parents can contribute the sperm and even the egg.

· Intracytoplasmic sperm injection (ICSI)- a single sperm is injected into an egg. It is used when a man has severe infertility problems.

  1. Sexually Transmitted Diseases

· Sexual transmitted disease (STDs) is caused by viruses, bacteria, protests, fungi, and animals.

· STDs Caused by Viruses

o AIDs is caused by HIV (human immunodeficiency virus). It is the last stage of HIV.

§ The primary host for HIV is a helper T lymphocyte.

§ There are no cures for AIDS but there are treatments. It helps stop HIV reproduction but treatment has to be taken indefinitely or the virus will rebound.

o Genital warts are caused by human papillomaviruses; these viruses cause warts or lesions on genitals and are associated with certain cancers.

§ Many times people don’t show signs of warts.

§ Can have the warts removed by surgery but may recur.

§ There are new vaccine that is important because genital warts can lead to cancer.

§ Researchers believe that these viruses can be involved in 90% of cancer of the cervix.

o Genital herpes is caused by herpes simplex virus type 2; causes blisters on genitals.

§ Some people show no symptoms to the virus.

§ Some people experience blisters on the genitals and is very painful and takes days to heal.


Genital Herpes around the mouth

o Viruses A, B, C, D, E, and G cause hepatitis. A and E are usually acquitted from contaminated water; hepatitis B and C from blood borne transmission; and B, D, and G are sexually transmitted.

o Hepatitis infects the liver and can lead to liver failure, liver cancer and death.

· STDs Caused by Bacteria

o Only STDs caused by bacteria are curable with antibiotics.

o Chlamydia is caused by Chlamydia trachomatis; PID can results.

§ The incidence of new Chlamydia infections has steadily increased since 1984.

§ The infections of the lower reproductive tract are usually mild especially in women.

§ Men may experiences burning sensation on urination and a muciod discharge.

§ Causes cervical ulcerations, which increase the risk of acquiring HIV.

o Gonorrhea is caused by the bacterium, neisseria gonorrhoeae.

§ Gonorrhea can spread to internal parts of the body, causing heart damage or arthritis.

§ Gonorrhea was curable by antibiotic therapy but resistance to antibiotic is becoming more and more common, and 40% of all strains are now known to be resistant to therapy.

o Syphilis is caused by a bacterium called treponema pallidum.

§ Penicillin is an effective antibiotic.

§ Has three stages:

· Primary stage-indicated the site of infection

· Secondary stage- breaks out in a rash that does not itch and seen on hands and feet.

· Tertiary stage-syphilis many affect the cardiovascular system by causing aneurysms, particularly in the aorta. This stage can result to death.


Syphillis

· Two Other Infections

o Bacterial vaginosis is caused by gardneralla vaginalis.

§ Believed to be accounted for 50% of vaginitis case in American women.

o Trichomoniasis is an overgrowth of Candida albicans.

§ Is a normal organism found in the vagina; its growth simply increases beyond normal under certain circumstances.

7. Picture References:

http://fig.cox.miami.edu/~cmallery/150/mitosis/lifecycle.jpg

http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_McKinley/f28-11_male_pelvic_regi_c.jpg

http://fig.cox.miami.edu/~cmallery/150/devel/c7.46.12.spermatogenesis.jpg

http://academic.kellogg.cc.mi.us/herbrandsonc/bio201%5FMcKinley/f28-2_sagittal_section__c.jpg

http://www.lib.mcg.edu/edu/eshuphysio/program/section5/5ch9/5ch9img/page3.jpg

http://baby4you.co.nz/images/Resized_Menstural_Cycle_for.gif

http://www.herpes-doctor.com/image_files/herpesmouth.jpg

http://www.aidsmeds.com/images/syphilissore.jpg

Chapter 17

Development and Aging

Chapter Concepts

1. Fertilization

2. Pre-Embryonic and Embryonic Development

3. Fetal Development

4. Pregnancy and Birth

5. Development After Birth

6. Picture References

1. Fertilization

· Fertilization is the union of a sperm and egg to form zygotes, the first cell of the new individual.

· Steps of Fertilization

o The tale of the sperm is a flagellum, which allows it to swim to the egg.

o Fertilization occurs when a sperm makes it way through the corona radiata, acrosome releases digestive enzymes to digest zona pellucida, sperm binds to the egg, their plasma membranes fuse, sperm enters the egg, and egg and sperm nuclei fuse.

Fertilization

2. Pre-Embryonic and Embryonic Development

· Processes of Development

o Cleavage- the zygote begins to divide so that there are first 2, then 4, 8, 16, and 32 cells, and so forth. Cell division during cleavage is mitotic, and each cell receives a full complement of chromosomes and genes.

o Growth- during embryonic development, cell division is accompanied by an increase in size of the daughter cells.

o Morphogenesis- Refers to the shaping of the embryo and is first evident when certain cells are seen to move, or migrate, in relation to other cells. The embryo begins to assume various shapes.

o Differentiation- when cells take on a specific structure and function, differentiation occurs. The first system to become visibly differentiated is the nervous system.

· Extra embryonic Membranes

o The extra embryonic membranes are not part of the embryo and fetus; but instead are outside of the embryo.

o Develop inside of the uterus.

§ Functions:

· Chorion- develops into the fetal half of the placenta, the organ that provides the embryo/fetus with nourishment and oxygen and takes away its waste. Blood vessels within the chorionic villi are continuous with the umbilical blood vessels.

· Allantois- like a yolk sac extends away from the embryo. It collects the small amount of urine produced by the fetal kidneys and later gives rise to the urinary bladder.

· Yolk sac- the yolk sac is the first embryonic membrane to appear. Contains plentiful blood vessels. It’s the first site of blood cell formation.

· Amnion- enlarges as the embryo and then the fetus enlarges. It contains fluid to cushion and protect the embryo, which develops into a fetus.


Human Embryonic Development

· Stages of Development

o The 280 days is called the normal gestation period.

o Only 5% of babies actually arrive on the predicted date.

o Pre-embryonic development encompasses the events of the first week.

o A morula is a compact ball of embryonic cells that becomes a blastocyst.

o The many cells of the blastocyst arrange themselves so that there is an inner cell mass surrounded by an outer later of cells.

o The inner cell mass will become the embryo, the layer of cells will become the chorion.

o Embryonic development begins with the second week and last until the end of the second month of development.

§ Second week-

· the embryo usually begins the process of implanting itself in the wall of the uterus.

· When implantation is successful, the women are clinically pregnant.

· If the embryo implants itself other location that is not the uterus it is called ectopic pregnancy.

· The chorion beings HCG. Pregnancy test detects HCG.

§ Third week-

· Two important organ system makes their appearance during the third week. The nervous system is the first organ.

· Development of the heart begins

§ Fourth and fifth weeks-

· A body stalk connects the embryo to the chorion which has treelike projections called chorionic villi.

· The umbilical cord, connects the developing embryo to the placenta is fully formed.

§ Sixth through eighth weeks-

· The embryo changes to a form that is recognized as a human being.

· Embryo is 38 mm (1.5 in).


An Embryo and three primary germ layers

3. Fetal Development

· At the end of the embryonic period, all organ systems are established, and there is a mature and functioning placenta. The umbilical arteries and umbilical vein takes blood to and from the placenta, where exchanges take place.

· Exchanges supply the fetus with oxygen and nutrients and rid the fetus of carbon dioxide and wastes.

· The umbilical cord is the lifeline of the fetus because it contains the umbilical arteries and vein.

· The venous ducts join the umbilical vein to the inferior vena cava.

Fetal circulation

· Events of Fetal Development

o Fetal development includes the third through the ninth months of development.

o Third and fourth months

§ Cartilage begins to be replaced by bone as ossification centers appear in most of the bones.

§ The skull has six large membrane areas called fontanels.

§ It is possible to determine the sex of the baby, boy or girl. The SRY gene is presence, usually on the Y-chromosomes.

§ The heartbeat is loud enough to be heard by a stethoscope.

§ The fetus is 152mm (6 in). Weighs (6 oz).

o Fifth through seventh months

§ A month can feel movement

§ A fine down called lanugo covers the wrinkled, translucent skin.

§ A white, greasy, cheese like substance called vernix caseosa.

§ The eyelids are now fully open.

§ The fetus is 300mm (12 in.) and weighs (3 lb)

o Eighth through Ninth Months

§ End of the nine month the fetus is 530mm (20 ½ in.) weighs (7 ½ lb.)

§ Full term babies have a best chance of survival while premature births chances are lower.

§ The end of development the fetus points its head toward the cervix.

§ If the fetus does not turn a breech birth will happen.

§ A cesarean section or c-section may be delivery of the fetus.

· Development of Male and Female Genitals

Female and Male external genitals

o The sex of an individual is determined at the moment of fertilization.

o At six weeks a small bud appears either the male penis or female clitoris

o Nine weeks, a urogenital groove bordered by two swellings appears.

o Fourteen week, the groove disappears, the swelling goes down and the male or female genital take form.

4. Pregnancy and Birth

· Major changes take place in the mother’s body during pregnancy.

· Weight gain occurs as the uterus occupies most of the abdominal cavity.

· Birth

o The uterus had contractions throughout pregnancy.

o Each contraction last 20-30 seconds about 15-20 minutes apart.

o Some women have “false labor” called Braxton hicks contractions.

o Each contraction is recurring and may become stronger.

o Prior to the first stage of parturition, there can be a “blood show”, caused by a mucous plug from the cervical canal.

o The plug prevents bacteria and sperm from entering the uterus during pregnancy.

· Stage 1

o The amniotic fluid is released which is often called “breaking water”

o The cervix dilates.

· Stage 2

o The child is born.

o Sometimes an episiotomy is preformed which is a cut around the vagina to deliver the baby. The incisions are later sewn together.

· Stage 3

o The afterbirth or placenta is expelled.

o About 15 minutes after delivery the contractions shrink the uterus and removal of the placenta.

Process of Birth

5. Development After Birth

· Development after birth consists of infancy, childhood, adolescence, and adulthood.

· Aging encompasses progressive changes from about age 20 on that contribute to an increased risk of infirmity, disease, and death.

· Hypotheses of Aging

o Aging may have a genetic basis.

o Aging may be due to changes that affect the whole body.

o Aging may be due to extrinsic factors (diet and exercise).

· Effect of Age of Body Systems

o Deterioration of organ systems can possibly be prevented or reduced in part of utilizing good health habits.

o Skin becomes thinner and less elastic. The number of elastic fiber decreases and the collagen fiber go through cross-linking.

o Less adipose tissue in the subcutaneous layer, therefore, older people will feel cold.

o Cardiovascular disorder is the leading cause of death. The heart shrinks because of a reduction in cardiac muscle cell size.

· The best way to stay healthy through aging is by healthy eating habits.

6. Picture References

http://www.chariho.k12.ri.us/cms/library/images/reproduction/fertilization1.jpg

http://faculty.southwest.tn.edu/rburkett/human_1.jpg

http://universe-review.ca/I10-13-layers.jpg

http://img.tfd.com/dorland/thumbs/circulation_fetal.jpg

http://images.main.uab.edu/healthsys/ei_0401.gif

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