Review Sheet 3 - Fertilization, Human Reproduction, Menstrual Cycle
Review Sheet 3 - Internal and External Fertilization/Development, Human Reproduction, Pregnancy, Menstrual Cycle
FERTILIZATION
The zygote may divide by mitosis and differentiate to form the specialized cells, tissues, and organs of multicellular organisms. Human reproduction and development are influenced by factors such as gene expression, hormones, and the environment.
During fertilization the gametes unite to form a zygote. Zygote formation is known as recombination since the genes from both parents recombine when fertilization occurs. Therefore, a zygote is a cell that contains all the genetic information necessary for growth, development and many other processes. Development is considered the changes an organism goes through from fertilization to birth.
EXTERNAL AND INTERNAL FERTILIZATION/EXTERNAL INTERNAL DEVELOPMENT
Compare and contrast internal fertilization of humans with external fertilization as seen in organisms such as birds, fish, amphibians and reptiles. Internal fertilization and development evolved as an adaptation to terrestrial life.
In particular, we took a close look at the external development of a chick embryo. You should be able to identify the variuos structures and understand their role in maintaining the embryo. (shell, yolk, yolk sac, albumin, air space, chorion, amniotic sac, amnion, amniotic fluid, allantois). You should be able to compare and contrast a chick embryo to a human embryo.
HUMAN REPRODUCTIVE SYSTEMS
The reproductive cycle in both males and females is regulated by hormones such as testosterone, estrogen and progesterone.
HUMAN MALE
The structures and functions of the human male reproductive system, as in other mammals, are designed to produce gametes in testes and make possible the delivery of these gametes for fertilization. The male reproductive system performs two major functions: the production of sperm with associated sex hormones and the deposition of sperm cells within the female reproductive tract.
Sperm production occurs in the testes and is stimulated by the hormone testosterone. The testes are paired structures located in the scrotum, a sac outside the body that regulates temperature for sperm production. From the testes sperm move to the epididymis, then the vas deferens, and urethra (located within the penis). The prostate gland, seminal vesicle, and bulborethral glands produce a liquid medium that mixes with sperm to form semen. The semen exits the male through the urethra. The penis and the semen are adaptations for life on land. The male deposits semen in the vagina of the female.
In addition to producing sperm, the testes are the sites for the production the male sex hormone testosterone. Testosterone regulates the maturation of sperm and the development of the male secondary sex characteristics, such as beard development, a deeper voice pitch, body hair, etc.
HUMAN FEMALE
The structures and functions of the female reproductive system, as in almost all other mammals, are designed to produce gametes in ovaries, allow for internal fertilization, support the internal development of the embryo and fetus in the uterus and provide essential materials through the placenta, and nutrition through milk for the newborn.
The female reproductive system performs two major functions. The first is to produce eggs or ova with associated sex hormones. The second is to serve as the site of internal development. The female reproductive system is specially designed for internal fertilization and development.
Ovaries are paired structures located within the lower portion of the body cavity. Ovaries produce eggs in tiny cavities called follicles. When an egg cell reaches maturity it is released from the ovary and is transported through the oviduct (fallopian tube) to the uterus. Fertilization usually occurs in the upper portion of the oviduct. A fertilized egg makes its way to the uterus for implantation. The uterus is a muscular organ that is normally the site of development. At the lower end of the uterus is the opening known as the cervix. The cervix is connected to the vagina, which receives the sperm and also serves as the birth canal.
In addition to eggs, the ovaries produce the sex hormones, estrogen and progesterone. These hormones play a coordinating role in the menstrual cycle, which prepares the body for a potential pregnancy each month. The menstrual cycle begins at puberty and ceases at menopause. Menopause is the permanent cessation of the menstrual cycle. The duration of this cycle is approximately 28 days but may vary considerably and may be interrupted by pregnancy, illness and other factors. (KNOW DETAILS OF MENSTRUAL CYCLE, EVEN IF THEY ARE NOT HERE. Hormones - LH, FSH, estrogen, progesterone, follicle, corpus luteum, uterine lining; Phases: flow/menstrual phase, follicle phase, ovulation, luteal phase)
You should be able to compare and contrast the male and female reproductive systems.
Feedback systems
Positive feedback systems - System A sends a message to system B in order to accomplish something, and once that message gets thru, the message from A gets increasingly stronger until the job is accomplished. In the early stages of labor the uterus contracts, pushing the babies head against the bottom of the uterus, which causes and even stronger contraction, which causes the babies head to pushes even harder on the base of the uterus... until the baby is born.
Negative feedback systems - System A sends a message to System B, and once System B accomplishes its task, it sends a message back to system A telling A to stop sending messages. Example - thermostat and heating system in homes.
The menstrual cycle is a negative feedback system - not only do hormones send messages for something to get done, they (estrogen and progesterone) also send messages back to the pituitary gland to turn of the incoming message (of FSH and LH, respectively.)
Preganancy
Fertilization usually occurs in the upper portion of the oviduct and a zygote is produced. The series of mitotic divisions that begin development start in the oviduct and 6 to 10 days later, the resulting embryo may become implanted in the uterine lining. After approximately 8 weeks of development, the embryo is called a fetus.
Within the uterus, the placenta is formed from embryonic and maternal tissues. It is through this structure that the exchange of nutrients, wastes and respiratory gases between the mother and embryo occurs.
There is no direct connection between the maternal and the embryonic bloodstream. Transport is accomplished by diffusion and active transport, through the placenta. An umbilical cord containing blood vessels, attaches the embryo to the placenta. Humans are placental mammals. In a few mammals, such as marsupials, there is no placenta.
The fetus develops in a watery environment, called amniotic fluid, which is contained within an amniotic sac. Birth usually occurs after a period of gestation (pregnancy) of approximately 38 weeks. The chorion encloses and protects the other membranes and becomes part of the placenta.
Just prior to and continuing after birth, there is a release of hormones that cause changes in the mother’s body leading to the production of milk by mammary glands and the return of the mother’s body to its pre-pregnancy condition.
Problems can occur during the first few months of pregnancy. At this time delicate vital organs are forming. These problems can be the result of genetics or of the mother’s exposure to harmful environmental factors that can affect the embryo. These harmful environmental factors include:
-exposure to radiation such as x-rays which can lead to abnormal organs and even death
-infectious microorganisms such as viruses that cause rubella and German measles or bacteria such as streptococci which can result in permanent brain damage, blindness, and/or death
-some chemicals such as tranquilizers which can result in limb deformities
-drugs such as heroin, LSD, and cocaine which can cause serious damage to the fetus and lead to prenatal addiction, pre-term labor as well as cognitive and psychological difficulties in infants
-alcohol use which can lead to fetal alcohol syndrome, and increase the risk of midtrimester abortion, mental retardation, as well as behavior and learning disorders
Cigarette smoking which can result in spontaneous abortions, ectopic pregnancies, fetal brain damage, growth retardation/low birth weight, lower or higher than normal blood pressure and mental retardation
Flowers and Sexual Reproduction - not for period 10
know and be able to identify the structures of a flower - stamen, pistil, ovary, pollen, style, anther, stigma. Understand how fruits and seeds form.
Pages from textbook
(Periods 4,5,6 only - 656, 666-667), 817, 819, 826, 839, 840, 1040-1055, 1058-1059,