Chapters 16-17
16.1 Human Life Cycle
Human reproduction is possible when a person completes puberty. In girls, that is reached at age 11-13 and boys at 14-16 years of age. To follow are the different functions of organs for each sex:
Male: Produce sperm Female: Produce eggs
Nurture sperm Transport egg to uterus
Penis delivers sperm into vagina Vagina receives sperm and provides conduit to egg
Testes produce sex hormones Uterus provides locale for fetal development
Vagina is pathway for delivery
Ovaries produce sex hormones
There are two types of cell division: mitosis and meiosis. Mitosis is duplication from one cell dividing producing two cells each containing all 46 chromosomes. Meiosis occurs only in the testes and ovaries of the reproductive organs. Each sperm and egg cell produces contain only 23 chromosomes so that when united, the zygote will have all 46 chromosomes.
16.2 Male Reproductive System
The testes (gonads) are the primary sex organs of the male reproductive system. The testes produce sperm and sex hormones. The scrotum will regulate the temperature of the testes by raising or lowering the testes from the body. Too warm and the sperm will not be viable. The sperm than mature and are stored in the epididymides. The sperm then leave the epididymides and can be stored in the vas deferens or transported onward. After entering the ejaculatoroy duct, nutrients and semen are contributed by the seminal vesicles, prostate gland, and bulbourethral glands.
Human reproduction is possible when a person completes puberty. In girls, that is reached at age 11-13 and boys at 14-16 years of age. To follow are the different functions of organs for each sex:
Male: Produce sperm Female: Produce eggs
Nurture sperm Transport egg to uterus
Penis delivers sperm into vagina Vagina receives sperm and provides conduit to egg
Testes produce sex hormones Uterus provides locale for fetal development
Vagina is pathway for delivery
Ovaries produce sex hormones
There are two types of cell division: mitosis and meiosis. Mitosis is duplication from one cell dividing producing two cells each containing all 46 chromosomes. Meiosis occurs only in the testes and ovaries of the reproductive organs. Each sperm and egg cell produces contain only 23 chromosomes so that when united, the zygote will have all 46 chromosomes.
16.2 Male Reproductive System
The testes (gonads) are the primary sex organs of the male reproductive system. The testes produce sperm and sex hormones. The scrotum will regulate the temperature of the testes by raising or lowering the testes from the body. Too warm and the sperm will not be viable. The sperm than mature and are stored in the epididymides. The sperm then leave the epididymides and can be stored in the vas deferens or transported onward. After entering the ejaculatoroy duct, nutrients and semen are contributed by the seminal vesicles, prostate gland, and bulbourethral glands.
Male reproductive anatomy:
I will not be commenting on the act of intercourse, since this is a public internet site. There may be greater than 400 million sperm in 3.5 mL of semen.
The Seminiferous Tubules are the locations of sperm production. It takes 74 days for sperm to develop. Mature sperm have 3 parts, head, middle piece, and tail. The head is covered by acrosome, which contains an enzyme to penetrate the egg. The middle piece has mitochondria which provides energy for movement. The tail flagellates to propel the sperm. The interstitial cells in the testes produce the sex hormones. The hypothalamus in the brain produces gonadotropin-releasing hormone (GnRH) that stimulates the anterior pituitary to release gonadotropic hormones, both follicle stimulating (stimulates sperm production) and luteinizing hormones (stimulates testosterone production). Testosterone maintains normal development and functioning of the sexual organs. It also gives males some of their male traits, such as greater muscle mass, lower voices, adam’s apple, broader shoulders and greater height.
16.3 Female Reproductive System
The Seminiferous Tubules are the locations of sperm production. It takes 74 days for sperm to develop. Mature sperm have 3 parts, head, middle piece, and tail. The head is covered by acrosome, which contains an enzyme to penetrate the egg. The middle piece has mitochondria which provides energy for movement. The tail flagellates to propel the sperm. The interstitial cells in the testes produce the sex hormones. The hypothalamus in the brain produces gonadotropin-releasing hormone (GnRH) that stimulates the anterior pituitary to release gonadotropic hormones, both follicle stimulating (stimulates sperm production) and luteinizing hormones (stimulates testosterone production). Testosterone maintains normal development and functioning of the sexual organs. It also gives males some of their male traits, such as greater muscle mass, lower voices, adam’s apple, broader shoulders and greater height.
16.3 Female Reproductive System
Ovaries are the female gonads. The produce eggs, estrogen and progesterone. The ovaries are located at one end of the fallopian tubes. They are not connected. The fallopian tubes have fimbriae (projections that sweep over the ovaries) and cilia which “brush” the eggs after they emerge from the ovaries in the direction of the uterus.
An egg is only viable for 6-24 hours until fertilization occurs. Fertilization usually occurs in the fallopian tube. The developing fetus (zygote, at this stage) arrives and implantation occurs in the thickened uterine lining. The uterus prior to emplantation is approx. 5 cm wide and can stretch to over 30cm wide when pregnant. The lining of the uterus is called the endometrium comprised of two layers, the basal laer and the functional layer. The cervix is at the base of the uterus and leads to the vaginal canal.
The external genitalia is collectively called vulva. The outermost folds are called labia majora. Moving medially, the next folds are called labia minora. Ventrally, they join to form a foreskin for the clitoris, this is the organ of arousal in a woman. Just dorsal to that is the urethra and then the vagina.
16.4 Female Hormone Levels
Hormones cycle an average of every 28 days. This is ovary-driven. An ovary initially contains as many as 2 million follicles and only about 400 will ever mature to produce an egg. Generally speaking, only one egg is produced every month.
16.4 Female Hormone Levels
Hormones cycle an average of every 28 days. This is ovary-driven. An ovary initially contains as many as 2 million follicles and only about 400 will ever mature to produce an egg. Generally speaking, only one egg is produced every month.
Genetic spicing gone wrong. The chicken must have died,
there's not a full dozen.
Back to the basics . . .
The human cycle is depicted in the picture below: 
http://www.anselm.edu/homepage/jpitocch/genbio/repronot.html
After the oocyte is released, the follicle develops into a corpus luteum. This produces progesterone and a little estrogen. As in men, the hypothalamus controls sexual function by releasing gonadotropin-releasing hormone. This stimulate the pituitary to produce FSHand LH, which control the ovarian cycle. During the first half of the cycle, the FSH stimulates the follicle in the ovary to produce estrogen which cignals the hypothalamus to secrete GnRH which in turn leads to a surge of LH production by the anterior pituitary and ovulation. The LH matures the corpus luteum and progesterone is secreted. Estrogen is responsible for our feminine traits. In encourages fatty accumulation under the skin, lending a softer appearance. The ovarian cycle will cease at around 50 years of age. The ovaries fail to respond to GhRH and no longer secrete estrogen and progesterone.
The uterine cycle is the response to the fluctuating hormones. The lining of the uterus will thicken to accommodate a possible developing embryo and this will slough off if an egg is not fertilized that month resulting in a menstrual period.
Pregnancy: Once a sperm has fertilized an egg, it becomes a zygote. This implants in the lining of the uterus. At the place where the molecules of fetal blood and maternal blood are exchanged, a placenta will develop. Progesterone production increases and will stop follicles from producing more eggs during the pregnancy. The placenta will begin to produce progesterone and estrogen and the corpus luteum will regress.
16.5 Control of Reproduction
There are multiple methods available to prevent pregnancy from occurring. They are listed below and these rates are applicable only when the methods are used correctly:
http://www.anselm.edu/homepage/jpitocch/genbio/repronot.html
After the oocyte is released, the follicle develops into a corpus luteum. This produces progesterone and a little estrogen. As in men, the hypothalamus controls sexual function by releasing gonadotropin-releasing hormone. This stimulate the pituitary to produce FSHand LH, which control the ovarian cycle. During the first half of the cycle, the FSH stimulates the follicle in the ovary to produce estrogen which cignals the hypothalamus to secrete GnRH which in turn leads to a surge of LH production by the anterior pituitary and ovulation. The LH matures the corpus luteum and progesterone is secreted. Estrogen is responsible for our feminine traits. In encourages fatty accumulation under the skin, lending a softer appearance. The ovarian cycle will cease at around 50 years of age. The ovaries fail to respond to GhRH and no longer secrete estrogen and progesterone.
The uterine cycle is the response to the fluctuating hormones. The lining of the uterus will thicken to accommodate a possible developing embryo and this will slough off if an egg is not fertilized that month resulting in a menstrual period.
Pregnancy: Once a sperm has fertilized an egg, it becomes a zygote. This implants in the lining of the uterus. At the place where the molecules of fetal blood and maternal blood are exchanged, a placenta will develop. Progesterone production increases and will stop follicles from producing more eggs during the pregnancy. The placenta will begin to produce progesterone and estrogen and the corpus luteum will regress.
16.5 Control of Reproduction
There are multiple methods available to prevent pregnancy from occurring. They are listed below and these rates are applicable only when the methods are used correctly:
Abstinence is the only guaranteed method of birth control and it also has the advantage of no STD transmission. Morning after pills are administered 1-7 days after intercourse has occurred. It upsets the progesterone cycle preventing the implantation of the embryo. RU-486 is a different type of morning-after pill that causes the endometrium to slough, of course the embryo goes with it.
Infertility is deemed such after one year of regularly attempted impregnation. Low sperm count is one cause of infertility. Too much sitting, smoking or drinking alcohol can cause this. Overweight women may fail to ovulate. Blocked oviducts from pelvic inflammatory disease and endometriosis can prevent the journey of the egg to the uterus also causing infertility.
There are technologies available to help infertile couples have children. Artificial insemination is when the sperm is placed in the vagina by a physician. This is helpful when the male has a low sperm count. Sometimes fertility drugs are given to the woman to produce one or more eggs and the sperm is placed directly into the uterus. In Vitro Fertilization, conception is attained in the lab. Then the embryos are transplanted in the uterus of the woman. Sometimes, other women are contracted to give birth. The egg and sperm can be from the desiring parents. Scientists can also inject a single sperm into and egg and then transplant it into the mom’s uterus.
16.6 Sexually Transmitted Diseases
Viral Sexually Transmitted Diseases
HIV – precursor to AIDS. First stage of infection can be asymptomatic, but highly contagious. This may develop into AIDS when the helper T cell count falls dangerously low and the host cannot fight infections. AIDS patients usually die from opportunistic infections that would normally be stopped by a healthy immune system.
Genital Warts – caused by the human papillomaviruses. The carriers may not have warts and may have less noticeable flat lesions. A baby can pick up this virus as it passes through the birth canal. Vaccinations are available for some the common strains of this virus. 90% of all cancers of the cervix are thought to be caused by this virus.
Genital Herpes – Herpes simplex type 2. This is presented with blisters, tingling or itching sensations. Some events may be accompanied with fever, pain with urination, or swollen lymph nodes and the person is very contagious at this time. Newborns may pick this up through the birth canal.
Several types of hepatitis are acquired through sexual transmission. This generally causes liver damage.
Bacterial Sexually Transmitted Diseases
These are curable with antibiotics. Some resistant strains may require taking stronger drugs for a longer amount of time.
Chlamydia – mild or asymptomatic in women. If undiagnosed, can spread from the cervix to the fallopian tubes causing pelvic inflammatory disease, a very painful condition which may result in infertility.
Gonorrhea – can lead to pelvic inflammatory disease in both males and females. Gonorrhea will infect whatever part was exposed to the virus and can be spread to internal parts, causing heart damage or arthritis. Because of increased resistance to antibiotic therapy, 40% of all strains don’t respond to therapy.
Syphilis – also potentially deadly, begins as a small ulcer (chancre) that resolves on its own. Then the infected person will develop a rash that does no itch and is seen on palms and soles of feet. This, too, will resolve. The last stage may affect the cardiovascular system by causing aneurysms and ulcers on the skin or internal organs. Early diagnosis and treatment is vital for successful treatment.
Other Common Infections
Bacterial vaginosis is asymptomatic and can be due to nonsexual reasons, or may have been passed on from infected males. Candida albicans (non-sexual) and Trichomonas (sexual) are vaginal infections treated with oral or topical medications.
Chapter 17: Development and Aging
17.1 Fertilization
The flagellum moves the sperm toward the egg. The arcosome on the head contains enzymes that will penetrate the zona pellucid.
http://www.wccusd.k12.ca.us/gompers/HealthScience/BodySystems/FemaleReproductiveSystem.html
As soon as the head touches the plasma membrane, it will depolarize prohibiting the penetration of more sperm. When a sperm enters an egg to form a zygote, fertilization occurs.
17.2 Pre-Embryonic and Embryonic Development
Immediately after fertilization, the cells begin to divide within the zygote but it doesn’t increase in size. Then the daughter cells begin to increase in size. At morphogenesis, the cells migrate and begin to form the shape of the embryo. Differentiation is when the cells begin to function according to their structure. The nervous system is the first to appear.
The structures that support the embryo are pictured below.
Chorion – becomes the fetus’ half of the placenta.
Allantois – extends away from the embryo, collects urine before bladder develops. The blood vessels will become the umbilical blood vessels.
Yolk Sac – first embryonic membrane to appear. It contains a small amount of yolk. The placenta will soon take over.
Amnion – contains fluid which will protect the baby.
http://www.wccusd.k12.ca.us/gompers/HealthScience/BodySystems/FemaleReproductiveSystem.html
As soon as the head touches the plasma membrane, it will depolarize prohibiting the penetration of more sperm. When a sperm enters an egg to form a zygote, fertilization occurs.
17.2 Pre-Embryonic and Embryonic Development
Immediately after fertilization, the cells begin to divide within the zygote but it doesn’t increase in size. Then the daughter cells begin to increase in size. At morphogenesis, the cells migrate and begin to form the shape of the embryo. Differentiation is when the cells begin to function according to their structure. The nervous system is the first to appear.
The structures that support the embryo are pictured below.
Chorion – becomes the fetus’ half of the placenta.
Allantois – extends away from the embryo, collects urine before bladder develops. The blood vessels will become the umbilical blood vessels.
Yolk Sac – first embryonic membrane to appear. It contains a small amount of yolk. The placenta will soon take over.
Amnion – contains fluid which will protect the baby.
From a zygot, to a morula, to a blastocyst, this will separate into the embryo inside and the outer layer called a chorion. Embryonic development begins the second week. The chorion will secret enzymes to eat away some the tissue of the endometrium and implant. It will also secrete human chorionic gonadotropin which will preserve the lining of the uterus until the pregnancy is completed. This is the start of gastrulation, forming of three primary germ layers:
Ectoderm: outer layer forming the epidermis, lining of oral cavity and nervous system
Mesoderm: middle layer forming the skeleton, muscles, dermis, CV system, urinary system,
reproductive system, outer layers of respiratory and digestive systems
Endoderm: inner layer forming the digestive tract and respiratory tract and their glands.
In the third week the nervous system and the heart begins to form. At the end of the fifth week the umbilical cord will be fully formed. Little limb buds become apparent. At the end of eight weeks, the nervous system has developed enough to permit a startled response. The embryo is about 1.5 inches long and all organ systems are present.
In the picture, ten models, approximately life-sized, represent eight weeks of embryonic development, at the end of which main organ systems, limbs and features have taken shape.
http://www.doc.ic.ac.uk/~gzy/heart/heart/embryo.htm
17.3 Fetal Development
At the third month the uterus is the size of a grapefruit and gender can be detected by ultrasound.
By four months, the skeleton is visible and hair is growing. At five months, a coating is developing on the baby and the heartbeat can be heard. By the seventh month, the testes descend in to the scrotom and the eyes are open. At eight months, the baby begins to develop that cute fat and is ready for birth at nine months.
Cute baby fat . . .
http://www.humorupload.com/files/F4A589dzy.jpg
During pregnancy, the placenta will become the source of progesterone and estrogen to discourage follicle stimulation and to maintain the endometrium.
The path of fetal circulation
http://www.lpch.org/DiseaseHealthInfo/HealthLibrary/cardiac/fetlcirc.html
Blood is received from the placenta, goes through the liver and is received in the right atrium. Some of it is shunted through the foramen ovale directly to the left atrium, then the left ventricle. Some of the blood in the right atrium will be pumped into the right ventricle where it will be sent through the pulmonary trunk and arterial duct to the aorta as well. The ventricle pumps the blood to the aorta and is then sent to the head and body and returns to the right atrium. Desaturated blood is returned to the placenta via the umbilical arteries. At birth the foramen ovale and arterial ducts will usually close in order to route the blood through the lungs when they start working.
At six weeks, the genitals are indifferent – no specific gender. A gene (SRY) will signal for testes to develop and the testes will produce testosterone. Without SRY, ovaries will develop. Genitals will develop into distinct gender at around 14 weeks.
People with the XY chromosome are males and XX are females. There are a few abnormal developments that make the determination ambiguous. The androgen insensitivity syndrome is when the membrane receptors for testosterone are ineffective. The person will develop as a female and it is not discovered until she fails to menstruate.
17.4 Pregnancy and Birth
randobs.blogspot.com/2008/01/pregnant-wife.html
Initially, one the the first symptoms of becoming pregnant is nausea, vomiting or loss of appetite. She may also become tired. This usually subsides after the first trimester. Energy and stamina are reported often throughout normal, progressing pregnancies. She will gain weight from the enlarging uterus and baby developing inside, her breasts are also enlarging, and her own increase in body fluid (40% increase in blood volume) and fat stores. Increased Progesterone levels will relax smooth muscles also causing perhaps, heartburn and constipation. The tidal volume of her lungs will increase 40% and carbon dioxide levels will fall 20%. Pressure from the uterus on the bladder can cause frequency and incontinence. Pressure on the vena cava will decrease venous return and may cause varicose veins and swollen legs.
As she approaches labor, contractions experienced throughout the pregnancy will become stronger. False labor or Braxton Hicks contractions may fool her into believing it is time for delivery. True labor is defined by contractions every 15-20 minutes lasting at least 40 seconds or longer.
The stretching cervix stimulates the release of oxytocin from the pituitary gland. This stimulates the uterine muscles. During Stage 1 of labor the uterus will push the baby harder against the cervix. When the cervix is completely dilated, Stage 1 is over. Stage 2 is the birth of the baby. Contractions occur more frequently to push the baby through the birth canal. During a normal presentation, the head appears first. Complications may occur if a different part presents. Stage 3 is the delivery of the placenta. The uterus continues to contract which shrinks the uterus and displaces the placenta.
Definitely worth the effort . . .
http://amazinasian.com/weblog/pics/59425792105_0_ALBsmall.jpg
17.5 Development after Birth
Gerontology is the study of aging. It has been the pursuit of many to find the fountain of youth. Research as to why we age has produced a mitochondrial hypothesis – when mitochondria produce energy, they produce free radicals (extra electrons). These attach to other molecules which become disabled and are destroyed. A restricted food intake shuts down the genes the turn on the activity of the mitochondria.
Many hormones also diminish or receptors become resistant. The thymus gland decreases in size and our immune response diminishes. Cancers increase in incidence as we age. Collagen stiffens and effect the elasticity of tendons and ligaments and skin (becomes thinner and less elastic). Hair follicles lessen in number and a decrease in melanocytes causes what hair is left to turn gray and skin to pale. Cardiovascular problems are associated with loss of muscle and hardening and narrowing of the arteries. Blood flow is reduced to all systems of the body and everything functions subpar. Medication must be closely monitored because the filtering of the kidneys and liver are diminished and unsafe levels can occur when elimination is compromised. The digestive tract also slows causing hearburn and slow elimination. Good news is that few neural cells of the cerebral cortex are lost during the aging process. It takes longer for a senior to learn new facts, but one can if given the time to do so. Diminished hearing and vision, glaucoma, loss of muscle mass, inability to hold urine, bone density decline, arthritis and weight gain are all problems shared by the elderly. Why are these the “Golden Years?”
Women enter menopause around 50 years of age and men enter andropause somewhat later between 50-90. Both signify a decrease of the sex hormone and diminished libido.
Many of the problems associated with aging can be avoided with good health habits developed earlier in life.
http://www.fammed.washington.edu/network/sfm/gerihands.jpg
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