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I have this sentence in my notes
Ovary is surrounded by tunica albuginea and the cortex keeps the primordial follicles. The medulla containing CT and blood vessels develop from mesonephros.
I have these words in my mind about CT
- cyto- (maybe cytotrophoblast)
- corona (no other than corona radiata so not)
What can CT be here?
I think CT is an abbreviation for connective tissue. Some examples of its use in that fashion:
The female reproductive system can at times feel like a difficult jumble of hormones that all seem to be related, but fluctuate in unpredictable ways. To make sense of the particularities of the female reproductive system, especially for exams like the MCAT, it is important to not only know what hormones are involved, but also to understand what their purpose is and how that purpose is connected to their seemingly random (but actually quite predictable!) cyclic fluctuations. Once you know all that, the reproductive system transforms from a confusing jumble of terms to a beautiful concert of hormones working together to drive and maintain the complex processes of ovulation, menstruation, and pregnancy.
Before we get started, it is important to introduce the key hormonal players that we will be tracking.
- Progesterone: Important for developing and maintaining the endometrium, a mucous membrane lining the uterus that is the site of implantation by a developing zygote (future fetus).
- Estrogen: Important for general female reproductive system maintenance, including thickening of the endometrium.
- Follicle stimulating hormone (FSH): Stimulates germ cell maturation and promotes estrogen production. Secreted by the anterior pituitary.
- Luteinizing hormone (LH): Promotes progesterone production. Secreted by the anterior pituitary.
- Gonadotropin-releasing hormone (GnRH):Released by the hypothalamus to stimulate FSH and LH production, but not as directly involved in the reproductive cycle signaling as the other hormones listed.
Stress Effects on the Excretory and Reproductive Systems
Stress Effects on the Excretory and Reproductive Systems
Male and Female Reproductive System
Develop a PowerPoint presentation about human reproduction. You are to pretend that the presentation is what you will use to give your son or daughter "the talk" about human reproduction. Objectives 1.Identify the major structures and functions of the endocrine, skeletal, muscular, reproductive, and nervous systems.. 2.Eva
Control of testosterone production and menstrual cycle
1. How does mitosis differ from meiosis? 2. In the male reproductive system, the hypothalamus releases (GnRH) to stimulate the release of (LH) from the anterior pituitary, which then causes (Leydig) cells to produce testosterone. (Use abbreviations.) Please check if answers in parenthesis are correct. 3. The ovarian and uteri
Mitosis, Meiosis, Chromosome Abnormalities and Genetic Tests
1. How does mitosis differ from meiosis? When do they occur in the body and what is their purpose? 2. Name and briefly describe 4 different chromosome abnormalities that can occur. (Use actual conditions and describe how they affect the carriers). 3. A child is born with attached ear lobes. His parents have free ear lobes. Wh
Genetic Testing: Preimplantation Genetic Diagnosis
In the last 20 years, genetic testing has advanced rapidly. It is now possible for families to test embryos for inherited diseases and only implant those who do not carry the disease. Through Preimplantation Genetic Diagnosis (PGD), families can carry children free of inherited diseases such as Huntington's disease or Amyotrophi
Controversy Surrounding Artificial Womb
If science could allow us to create and artificial womb, maybe even allowing an animal womb for humans that would be safe and effective should scientists purse this research and development? Why would some people be against this technology?
Explain the reproductive system. Include all the major endocrine glands and the most important hormones that they produce.
Information about Hormones
Provide the following information in a table format or paragraphs on the following parts as it relates to the following. 1. FSH 2. ESTROGEN 3. MELATONIN 4. OXYTOCIN What type of molecule is the hormone? What stimulates the production and or release of the hormone? Where is the hormone synthesized and released? Where
Describe the components of the male reproductive system and the roles played by the reproductive tract and accessory glands in producing spermatozoa specify the composition of semen and summarize the hormonal mechanism that regulate male reproductive functions
Describe the components of the male reproductive system and the roles played by the reproductive tract and accessory glands in producing spermatozoa specify the composition of semen and summarize the hormonal mechanism that regulate male reproductive functions. The main topic is the male reproductive system but the main fo
Table of human hormones including the regulation, major actions, and symptoms of too much or too little hormone.
Table of hormones including: growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, follicle stimulating hormone, lutenizing hormone, oxytocin, antidiuretic hormone/vasopressin, thyroid hormone, calcitonin, parathyroid hormone, mineralcorticoids, glucocorticoids, gonadocorticoids, catecholamines, insulin and g
A sample of female blood is analyzed for reproductive hormone levels. The results indicate a low level of progesterone, low levels of sestrogen, low levels of inhibin, and elevated levels of FSH and LH. The female is most likely experiencing [ ] of the uterine cycle A. Proliferative phase B. Menses C. Secretory p
Explanation of the uterine and ovarian cycles.
Explain the hormones and phases of the uterine cycle.
Graphs needed in excel to show hormonal events in menstrual cycle.
Hi, I just need help with 4 diagrams in excel in total. 2 diagrams to show the hormonal events in menstrual cycle. graph 1: say a graph that shows the levels of each hormone during the menses, ovulation and luteal phase in relation to follicle development. and graph 2: showing levels of hormones estrradol and progesterone in
Estrogen and bones during menopause
Estrogen and bone relationship and its effect during menopause. I want both some web links on this subject and some general points - enough to do some research.
Uterus and cervix
The uterus is a thick-walled, muscular, pear-shaped organ located in the middle of the pelvis, behind the bladder, and in front of the rectum. The uterus is anchored in position by several ligaments. The main function of the uterus is to sustain a developing fetus.
The uterus consists of the following:
The cervix is the lower part of the uterus, which protrudes into the upper part of the vagina. It can be seen during a pelvic examination. Like the vagina, the cervix is lined with a mucous membrane, but the mucous membrane of the cervix is smooth.
Sperm can enter and menstrual blood can exit the uterus through a channel in the cervix (cervical canal). The cervical canal is usually narrow, but during labor, the canal widens to let the baby through.
The cervix is usually a good barrier against bacteria, except around the time an egg is released by the ovaries (ovulation), during the menstrual period, or during labor. Bacteria that cause sexually transmitted diseases can enter the uterus through the cervix during sexual intercourse.
Did You Know.
Girls are born with over a million egg cells, but only about 400 are released during a lifetime of menstrual cycles.
No new eggs develop after birth.
The channel through the cervix is lined with glands that secrete mucus. This mucus is thick and impenetrable to sperm until just before ovulation. At ovulation, the mucus becomes clear and elastic (because the level of the hormone estrogen increases). As a result, sperm can swim through the mucus into the uterus to the fallopian tubes, where fertilization can take place. At this time, the mucus-secreting glands of the cervix can store live sperm for up to about 5 days, but occasionally slightly longer. These sperm can later move up through the corpus and into the fallopian tubes to fertilize an egg. Almost all pregnancies result from intercourse that occurs during the 3 days before ovulation. However, pregnancies sometimes result from intercourse that occurs up to 6 days before ovulation or during the 3 days after ovulation. For some women, the time between a menstrual period and ovulation varies from month to month. Consequently, pregnancy can occur at different times during a menstrual cycle.
The corpus of the uterus, which is highly muscular, can stretch to accommodate a growing fetus. Its muscular walls contract during labor to push the baby out through the cervix and the vagina. During the reproductive years, the corpus is twice as long as the cervix. After menopause, the reverse is true.
As part of a woman's reproductive cycle (which usually lasts about a month), the lining of the corpus (endometrium) thickens. If the woman does not become pregnant during that cycle, most of the endometrium is shed and bleeding occurs, resulting in the menstrual period.
How Many Eggs?
A baby girl is born with egg cells (oocytes) in her ovaries. Between 16 and 20 weeks of pregnancy, the ovaries of a female fetus contain 6 to 7 million oocytes. Most of the oocytes gradually waste away, leaving about 1 to 2 million present at birth. No oocytes develop after birth. At puberty, only about 300,000—more than enough for a lifetime of fertility—remain.
Only a small percentage of oocytes mature into eggs. The many thousands of oocytes that do not mature degenerate. Degeneration progresses more rapidly in the 10 to 15 years before menopause. All are gone by menopause.
Only about 400 eggs are released during a woman's reproductive life, usually one during each menstrual cycle. Until released, an egg remains dormant in its follicle—suspended in the middle of a cell division. Thus, the egg is one of the longest-lived cells in the body.
Because a dormant egg cannot repair itself as cells usually do, the opportunity for damage increases as a woman ages. A chromosomal or genetic abnormality is thus more likely when a woman conceives a baby later in life.
The mammary glands are modified sweat glands that produce milk in a process called Lactation
· Lobes(15-20) Separated by fat and CT
· Lobules –contain alveoli
· Alveoli –milk secreting cells
· Lactiferous Duct-drain milk from lobules
· Lactiferous Sinus -empty milk into nipples
· Nipple –surrounded by pigmented areola
Answer to Problem 15A
The correct answer is option (D) in an oviduct.
Explanation of Solution
Explanation/justification for the correct answer:
Option (D) in an oviduct. Fertilization usually occurs in the fallopian tube which is also known as oviduct. The oviduct is a part of the genital tract. Fertilization takes place in the oviduct which is located between the ovary and uterus. So, this is the correct option.
Explanation for incorrect answer:
Option (A) in the uterus. The fertilization takes place in the oviduct. The oviduct is present between the ovary and the uterus. It does not occur usually in the uterus. So, this is an incorrect option.
Option (B) in the vagina. The fertilization takes place in the oviduct. The oviduct is present between the ovary and the uterus. The fertilization does not take place in the vagina. So this is an incorrect option.
Option (C) in the corpus luteum. The fertilization takes place in the oviduct. The oviduct is present between the ovary and the uterus, as fertilization does not occur in the corpus luteum. So, this is an incorrect answer.
Study the Male and Female Reproductive Systems
The organs that comprise the male genital system are the testicles, the epididymis, the vas deferens, the seminal vesicles, the ejaculatory duct, the prostate, the bulbourethral glands, the urethra and the penis.
More Bite-Sized Q&As Below
2. Concerning reproduction, what is the function of the testicles?
The testicles are the male gonads that is, the organs where the production of gametes takes place. In human beings, gametes are produced by meiosis that occurs in the testicles.
3. After passing the epididymis, through which structures do sperm cells travel until exteriorization?
After leaving the epididymis in the testicle, sperm cells enter the vas deferens. After that, they receive secretions from seminal vesicles and gather (from the right and left sides) in the ejaculatory duct. They also get secretions from the prostate and the bulbourethral glands and then go through the urethra, inside the penis, to the exterior.
4. What is the function of the secretions of the prostate, seminal vesicle and bulbourethral glands in reproduction?
These secretions, along with sperm cells from the testicles, form semen. These secretions have the function of nourishing the sperm cells and serving as a fluid means of propagation for them. The alkaline pH of seminal fluid also neutralizes the acidic secretions of the vagina, allowing the survival of sperm cells in the vaginal environment after copulation.
5. What endocrine glands regulate sexual activity in males? How does this regulation work and what hormones are involved ?
In males, sexual activity is regulated by the endocrine glands: the hypophysis (the pituitary), the adrenal glands and the gonads (testicles).
FSH (follicle-stimulating hormone) secreted by the adenohypophysis acts on the testicles, stimulating spermatogenesis. LH (luteinizing hormone), another adenohypophyseal hormone, also stimulates the production of testosterone by the testicles. Testosterone, the production of which intensifies after the beginning of puberty, acts on several organs of the body and is responsible for the appearance of secondary male sex characteristics (beard, body hair, deep voice, increase in the muscle and bone mass, maturation of genitalia, etc.). Testosterone also stimulates spermatogenesis.
The Female Reproductive System
6. What organs are a part of the female reproductive system?
The organs that make up the female reproductive system are the ovaries, the Fallopian tubes (or uterine tubes), the uterus, the vagina and the vulva.
7. During which period of life does the formation of gametes begin in women?
The meiosis that forms female gametes begins in the cells of ovarian follicles before birth. After the beginning of puberty, under hormonal stimuli, during each menstrual cycle, one of the cells is released on the surface of the ovary and meiosis resumes. However, the meiotic process is only concluded if fertilization occurs.
8. What organ releases the female gamete under formation? How is this release triggered? What organ collects the released gametes?
The organ that releases the female gamete is the ovary, the female gonad. The releasing of the oocyte is a response to hormonal stimuli. The immature egg cell (still an oocyte) falls into the abdominal cavity and is picked up by the Fallopian tube (uterine tube, or oviduct), a tubular structure that connects the ovary with the uterus.
9. What are the anatomical relationships between the organs of the female reproductive system, from the external vulva to the ovaries?
The external female genitalia is called the vulva. The vulva is the external opening of the vaginal canal, or vagina. The vagina is the copulation organ of females and its posterior extremity communicates with the uterus through the uterine cervix. The uterus is divided into two portions: the cervix and the uterine cavity. The lateral walls of the uterine fundus communicate with the Fallopian tubes. The other extremity of each Fallopian tube ends in fimbria, forming fringes in the abdominal cavity. Between the uterine tube and the ovary is intra-abdominal space.
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The Menstrual Cycle
10. What is the menstrual cycle?
The menstrual cycle is the periodic succession of interactions between the hormones and organs of the female reproductive system that, after the beginning of puberty, regulates the release of female gametes and prepares the uterus for fertilization and pregnancy.
11. What endocrine glands are involved in the menstrual cycle? What hormones are in involved?
The endocrine glands that secrete hormones involved in the menstrual cycle are the hypophysis (the pituitary gland) and the ovaries.
The hormones from the adenohypophysis are FSH (follicle-stimulating hormone) and LH (luteinizing hormone) and the hormones from the ovaries are estrogen and progesterone.
12. What event marks the beginning of the menstrual cycle? What is the blood concentration of FSH, LH, estrogen and progesterone during this phase of the cycle?
By convention, the menstrual cycle begins on the day that menses begins. (Menses is the endometrial hemorrhage excreted through the vaginal canal.) During these days, the hormones FSH, LH, estrogen and progesterone have low concentration.
13. After menses, what hormone influences the maturation of ovarian follicles?
The maturation of ovarian follicles after menses is stimulated by the action of FSH (follicle-stimulating hormone).
14. What hormone is secreted by the growing ovarian follicles? What is the action of that hormone on the uterus?
The follicles growing after menses secrete estrogen. These hormones act on the uterus, stimulating the thickening of the endometrium (the internal mucosa of the uterus).
15. What is the relationship between estrogen level and the LH level in the menstrual cycle? What is the function of LH in the menstrual cycle and when does its blood concentration reach a peak?
The increase in the blood concentration of estrogen with the growing of the ovarian follicle causes the hypophysis to secrete LH. During this phase, LH acts along with FSH to promote the maturation of the follicle, which on the 14th day, ruptures, releasing the female gamete (ovulation). After the release of the ovum, LH stimulates the formation of the corpus luteum, a structure made from the remaining follicular mass. LH concentration is at its maximum on the 14th day of the cycle.
16. What hormones promote the release of the female gamete from the follicle and on which day of the menstrual cycle does this phenomenon happen? What is this event called?
The hormones that promote the release of the ovum from the follicle are FSH and LH, hormones found in maximum blood concentration around the 14th day of the cycle. The release of the female gamete from the ovary is called ovulation. Ovulation happens at (around) on 14th day of the menstrual cycle.
17. How does the female gamete move from the ovary to the uterus?
The female gamete released by the ovary falls into the surrounding abdominal cavity and is collected by the Fallopian tube. The internal epithelium of the uterine tubes has ciliated cells that move the ovum or the fertilized egg cell towards the uterus.
18. How long after ovulation must fertilization occur to be effective?
If fertilization does not occur approximately 24 hours after ovulation, the released ovum often dies.
19. Into what structure is the follicle transformed after ovulation? What is the importance of that structure in the menstrual cycle?
The follicle that released the ovum undergoes the action of LH and is transformed into the corpus luteum. The corpus luteum is very important because it secretes estrogen and progesterone.
These hormones prepare the uterine mucosa, also known as endometrium, for nidation (the implantation of the zygote in the uterine wall) and embryonic development, since they stimulate the thickening of the mucous tissue, increase its vascularity and cause the appearance of uterine glycogen-producing glands.
20. What is the importance of uterine glycogen-producing glands?
Uterine glands produce glycogen that can be broken down into glucose to nourish the embryo before the complete development of the placenta.
21. How does negative feedback between the hypophysis and corpus luteum work? What is the name given to the atrophied corpus luteum after this feedback process?
After ovulation, the estrogen and progesterone secretions from the corpus luteum inhibit hypophyseal FSH and LH secretions (this happens through the inhibition of GnRH, gonadotropin-releasing hormone, a hypothalamic hormone). The blood concentration of these adenohypophyseal hormones falls to basal levels once again. As LH lowers, the corpus luteum (luteum means “yellow”) becomes atrophic and turns into the corpus albicans (“white”). With the regression of the corpus luteum, the production of estrogen and progesterone ceases.
22. In hormonal terms, why does menses occur?
Menses is the monthlyndometrial desquamation that occurs as the estrogen and progesterone levels fall after the regression of the corpus luteum. This is because these hormones, mainly progesterone, can no longer support and maintain the thickening of the endometrium.
23. What is the explanation for the bleeding that accompanies menses?
The hemorrhage that accompanies menses occurs because the endometrium is a highly vascularized tissue. The rupture of the blood vessels of the uterine mucosa during menstrual desquamation causes the bleeding.
24. What are the phases of the menstrual cycle?
The menstrual cycle is divided into two main phases: the follicular (or menstrual) phase and the luteal (or secretory) phase.
The menstrual phase begins on the first day of menses and lasts until ovulation (around the 14th day). The luteal phase begins after ovulation and ends when menses begins (around the 28th day).
25. Including the main events and hormonal changes, how can the menstrual cycle be described?
The cycle can be described like an analog clock on which 12 o’clock is the beginning and the end of the menstrual cycle and 6 o’clock corresponds to the 14th day of the cycle.
At 12 o’clock, menses and therefore the menstrual cycle begin and FSH blood levels begins to increase. Around 2 o’clock, the follicles maturing under the effect of FSH are already secreting estrogen and the endometrium is thickening. Around 3 o’clock, estrogen is intensely stimulating the increase of LH blood levels. At 6 o’clock (the 14th day), LH is at its maximum concentration and FSH is also at high levels to promote ovulation. LH then stimulates the formation of the corpus luteum. Around 7 o’clock, the corpus luteum is already secreting a large amount of estrogen and progesterone and the endometrium thickens even more levels of FSH and LH decrease with the increasing of the ovarian hormones. Around 11 o’clock, the reduced LH and FSH levels make the corpus luteum turn into the corpus albicans the production of estrogen and progesterone ceases and the endometrium regresses. At 12 o’clock again (the 28th day), the endometrium desquamates and a new menstrual cycle begins.
26. In general, during what phase of the menstrual cycle can copulation lead to fertilization?
Although this is not a rule, to be effective, fertilization must occur within 24 hours after ovulation (which occurs around the 14th day of the menstrual cycle). Fertilization may occur even if copulation took place up to 3 days before ovulation, since male gametes remain viable for about 72 hours within the female reproductive system.
However, the fertile period of the women is considered to be the period from 7 days before ovulation to 7 days after ovulation.
27. In what part of the female reproductive system does fertilization occur?
Fertilization generally occurs in the Fallopian tubes, but it can also take place in the uterus. There are cases when fertilization may occur even before the ovum enters the uterine tube, which may lead to a severe medical condition known as abdominal pregnancy.
28. How does the sexual arousal mechanism in women facilitate fertilization?
During sexual arousal in women, the vagina secretes substances to neutralize its acidity, thus allowing the survival of sperm cells within it. During the female fertile period, hormones make the mucus that covers the internal surface of the uterus less viscous to help the passage of sperm cells into the uterine tubes. During copulation, the uterine cervix advances inside the vagina to facilitate the entrance of male gametes through the cervical canal.
Nidation and Pregnancy
29. What is nidation? During which phase of the menstrual cycle does nidation occur?
Nidation is the implantation of the embryo into the uterus. Nidation occurs around the 7th day after fecundation, that is, 7 to 8 days after fertilization (obviously, it occurs only if fecundation also occurs). Since it occurs in the luteal phase ,the progesterone level is high and the endometrium is in its best condition to receive the embryo.
30. What is tubal pregnancy?
Often fertilization takes place in the Fallopian tubes. Generally, the newly formed zygote is moved to the uterus, where nidation and embryonic development occur. However, in some cases, the zygote cannot descend into the uterus and the embryo implants itself in the uterine tube tissue, which is the characteristic of tubal pregnancy. Tubal pregnancy is a severe clinical condition since the tube often ruptures during gestation, causing a hemorrhage and even the death of the woman. The most common treatment for tubal pregnancy is surgery.
31. How do hormonal tests to detect pregnancy work?
Laboratory tests to detect pregnancy commonly test for human chorionic gonadotropin (HCG) concentration in blood or urine samples. If the level of this hormone is abnormally high, pregnancy is likely.
32. Does the hypophysis-ovaries endocrine axis work in the same way during pregnancy as in non-pregnant women? If pregnancy does not occur how does another menstrual cycle begin?
The functioning of the hypophysis is altered during pregnancy. Since estrogen and progesterone levels remain elevated during the gestational period, the production of GnRH (gonadotropin-releasing hormone) from the hypothalamus is inhibited. The lack of GnRH therefore inhibits the secretion of FSH and LH by the hypophysis and a new menstrual cycle does not begin.
If pregnancy does not occur, the lowering of estrogen and progesterone levels stimulates the production of GnRH by the hypothalamus. This hormone then hastens the adenohypophyseal secretion of FHS and LH, which in turn stimulate the maturation of follicles and the beginning of a new menstrual cycle.
33. What is the endocrine function of the placenta?
The placenta, in addition to being the organ through which the exchange of substances between the mother and the fetus is carried out, also has the function of secreting estrogen and progesterone to maintain a high level of these hormones during pregnancy. (The placenta still secretes other hormones such as human placental lactogen, which acts in a way similar to that of the hypophyseal hormones that regulate reproduction, and HCG, human chorionic gonadotropin.)
Reproductive Planning Methods
34. How do contraceptive pills generally work?
Contraceptive pills generally contain the hormones estrogen and progesterone. If taken daily from the 4th day after menses, the abnormal elevation of these hormones acts upon the hypophysis-hypothalamus endocrine axis, inhibiting FSH and LH secretions. Since these hormones do not reach their normal high levels during the menstrual cycle, ovulation does not occur.
(Treatment with contraceptive pills must be started under medical supervision.)
35. What are the common contraindications of contraceptive pills?
There are medical reports associating the use of contraceptive pills with vomiting, nausea, vertigo, headaches, hypertension and other pathological conditions. Some research has attempted to relate the medical ingestion of estrogen and progesterone with an increased propensity for cardiovascular diseases (such as heart attacks, strokes and thrombosis) and malignant neoplasms (cancers). Doctors must always be askedꂫout the risks and benefits of the contraceptive pill prior to use.
36. What are the most common methods of male and female surgical sterilization?
Vasectomy is the most common method of surgical sterilization in men. In vasectomy, the vas deferens inside the scrotum are sectioned and closed at a section, forbidding the sperm cells from entering the ejaculatory duct but still allowing the release of seminal fluid during ejaculation.
The surgical sterilization of women is often done by bilateral tubal ligation. With tubal ligation, the ovum does not enter the uterus and, as a result, sperm cells cannot reach it.
37. How does a contraceptive diaphragm work? What are the limitations of this contraceptive method?
A contraceptive diaphragm is a device made of latex or plastic that, when placed on the vaginal fundus, covers the uterine cervix, preventing the passage of sperm cells through the cervical canal. To be more effective, the diaphragm needs to be used with spermicide. However, this method does not prevent sexually transmitted infections (STIs).
38. Why is the use of condoms not just a contraceptive method but also a health protection behavior?
The use of condoms, in addition to being an efficient contraceptive method, also helps the prevention of diseases caused by sexually transmitted agents (STIs), such as syphilis, gonorrhea, HPV (the human papilloma virus, which may lead to genital cancers) infection, HIV infection, etc.
39. What is the normal duration of the menstrual cycle? How does the calendar contraceptive method work?
The normal duration of the menstrual cycle is 28 days, but it can vary among different women or different cycles in the same woman.
In the calendar contraceptive method, the date n-14 (n minus 14) is taken, considering n the number of days of the normal menstrual cycle of the woman (generally n=28). The safety margin +3 or –3 refers to the days around n-14 during which intercourse should be avoided to prevent pregnancy. (This method is not completely free of failures. A doctor must always be consulted before relying on any contraceptive method.)
40. How is the ovulation date estimated via the measurement of a woman's body temperature?
One method to estimate the exact ovulation date is daily measurement of body temperature always done under same conditions. On the date of ovulation, body temperature often increases about 0.5 degrees centigrade.
41. What is the contraceptive mechanism of an IUD?
An IUD (intrauterine device) is a piece of plastic coated with copper that is inserted into the uterus by a doctor. Copper is then gradually released (an IUD can last from 5 to 10 years) and since it has a spermicidal effect, sperm cells are destroyed before fertilization. in addition to this mechanism, the movement of the IUD inside the uterus causes slight endometrial inflammation, which helps to prevent nidation.
Reproduction in Other Animals
(See zoology subjects for a comprehensive review.)
42. Generally, how does a male animal realize that the female is receptive to copulation?
In most vertebrate species with internal fertilization, females have reproductive cycles with fertile periods. During this period, the female secretes pheromones (odoriferous substances that attract the male of the species) from the skin and mucosae. The presence of the male individual and his pheromones also stimulates the release of pheromones by the female. (Many animals also use pheromones to mark their territories and for signal transmission between individuals about the location of dangers and food.)
43. What is parthenogenesis?
Parthenogenesis is the reproduction or formation of a new individual from the egg cell without fertilization by the male gamete. Depending on the species, individuals born via parthenogenesis may be male or female, or of any sex.
In bees, the drone (the single male bee) is haploid and born via parthenogenesis while the females (queen and workers) are diploid.
Now that you have finished studying Reproductive System, these are your options:
27.2 Anatomy and Physiology of the Female Reproductive System
The female reproductive system functions to produce gametes and reproductive hormones, just like the male reproductive system however, it also has the additional task of supporting the developing fetus and delivering it to the outside world. Unlike its male counterpart, the female reproductive system is located primarily inside the pelvic cavity (Figure 27.9). Recall that the ovaries are the female gonads. The gamete they produce is called an oocyte . We’ll discuss the production of oocytes in detail shortly. First, let’s look at some of the structures of the female reproductive system.
External Female Genitals
The external female reproductive structures are referred to collectively as the vulva (Figure 27.10). The mons pubis is a pad of fat that is located at the anterior, over the pubic bone. After puberty, it becomes covered in pubic hair. The labia majora (labia = “lips” majora = “larger”) are folds of hair-covered skin that begin just posterior to the mons pubis. The thinner and more pigmented labia minora (labia = “lips” minora = “smaller”) extend medial to the labia majora. Although they naturally vary in shape and size from woman to woman, the labia minora serve to protect the female urethra and the entrance to the female reproductive tract.
The superior, anterior portions of the labia minora come together to encircle the clitoris (or glans clitoris), an organ that originates from the same cells as the glans penis and has abundant nerves that make it important in sexual sensation and orgasm. The hymen is a thin membrane that sometimes partially covers the entrance to the vagina. An intact hymen cannot be used as an indication of “virginity” even at birth, this is only a partial membrane, as menstrual fluid and other secretions must be able to exit the body, regardless of penile–vaginal intercourse. The vaginal opening is located between the opening of the urethra and the anus. It is flanked by outlets to the Bartholin’s glands (or greater vestibular glands).
The vagina , shown at the bottom of Figure 27.9 and Figure 27.9, is a muscular canal (approximately 10 cm long) that serves as the entrance to the reproductive tract. It also serves as the exit from the uterus during menses and childbirth. The outer walls of the anterior and posterior vagina are formed into longitudinal columns, or ridges, and the superior portion of the vagina—called the fornix—meets the protruding uterine cervix. The walls of the vagina are lined with an outer, fibrous adventitia a middle layer of smooth muscle and an inner mucous membrane with transverse folds called rugae . Together, the middle and inner layers allow the expansion of the vagina to accommodate intercourse and childbirth. The thin, perforated hymen can partially surround the opening to the vaginal orifice. The hymen can be ruptured with strenuous physical exercise, penile–vaginal intercourse, and childbirth. The Bartholin’s glands and the lesser vestibular glands (located near the clitoris) secrete mucus, which keeps the vestibular area moist.
The vagina is home to a normal population of microorganisms that help to protect against infection by pathogenic bacteria, yeast, or other organisms that can enter the vagina. In a healthy woman, the most predominant type of vaginal bacteria is from the genus Lactobacillus. This family of beneficial bacterial flora secretes lactic acid, and thus protects the vagina by maintaining an acidic pH (below 4.5). Potential pathogens are less likely to survive in these acidic conditions. Lactic acid, in combination with other vaginal secretions, makes the vagina a self-cleansing organ. However, douching—or washing out the vagina with fluid—can disrupt the normal balance of healthy microorganisms, and actually increase a woman’s risk for infections and irritation. Indeed, the American College of Obstetricians and Gynecologists recommend that women do not douche, and that they allow the vagina to maintain its normal healthy population of protective microbial flora.
The ovaries are the female gonads (see Figure 27.9). Paired ovals, they are each about 2 to 3 cm in length, about the size of an almond. The ovaries are located within the pelvic cavity, and are supported by the mesovarium, an extension of the peritoneum that connects the ovaries to the broad ligament . Extending from the mesovarium itself is the suspensory ligament that contains the ovarian blood and lymph vessels. Finally, the ovary itself is attached to the uterus via the ovarian ligament.
The ovary comprises an outer covering of cuboidal epithelium called the ovarian surface epithelium that is superficial to a dense connective tissue covering called the tunica albuginea. Beneath the tunica albuginea is the cortex, or outer portion, of the organ. The cortex is composed of a tissue framework called the ovarian stroma that forms the bulk of the adult ovary. Oocytes develop within the outer layer of this stroma, each surrounded by supporting cells. This grouping of an oocyte and its supporting cells is called a follicle . The growth and development of ovarian follicles will be described shortly. Beneath the cortex lies the inner ovarian medulla, the site of blood vessels, lymph vessels, and the nerves of the ovary. You will learn more about the overall anatomy of the female reproductive system at the end of this section.
The Ovarian Cycle
The ovarian cycle is a set of predictable changes in a female’s oocytes and ovarian follicles. During a woman’s reproductive years, it is a roughly 28-day cycle that can be correlated with, but is not the same as, the menstrual cycle (discussed shortly). The cycle includes two interrelated processes: oogenesis (the production of female gametes) and folliculogenesis (the growth and development of ovarian follicles).
Gametogenesis in females is called oogenesis . The process begins with the ovarian stem cells, or oogonia (Figure 27.11). Oogonia are formed during fetal development, and divide via mitosis, much like spermatogonia in the testis. Unlike spermatogonia, however, oogonia form primary oocytes in the fetal ovary prior to birth. These primary oocytes are then arrested in this stage of meiosis I, only to resume it years later, beginning at puberty and continuing until the woman is near menopause (the cessation of a woman’s reproductive functions). The number of primary oocytes present in the ovaries declines from one to two million in an infant, to approximately 400,000 at puberty, to zero by the end of menopause.
The initiation of ovulation —the release of an oocyte from the ovary—marks the transition from puberty into reproductive maturity for women. From then on, throughout a woman’s reproductive years, ovulation occurs approximately once every 28 days. Just prior to ovulation, a surge of luteinizing hormone triggers the resumption of meiosis in a primary oocyte. This initiates the transition from primary to secondary oocyte. However, as you can see in Figure 27.11, this cell division does not result in two identical cells. Instead, the cytoplasm is divided unequally, and one daughter cell is much larger than the other. This larger cell, the secondary oocyte, eventually leaves the ovary during ovulation. The smaller cell, called the first polar body , may or may not complete meiosis and produce second polar bodies in either case, it eventually disintegrates. Therefore, even though oogenesis produces up to four cells, only one survives.
How does the diploid secondary oocyte become an ovum —the haploid female gamete? Meiosis of a secondary oocyte is completed only if a sperm succeeds in penetrating its barriers. Meiosis II then resumes, producing one haploid ovum that, at the instant of fertilization by a (haploid) sperm, becomes the first diploid cell of the new offspring (a zygote). Thus, the ovum can be thought of as a brief, transitional, haploid stage between the diploid oocyte and diploid zygote.
The larger amount of cytoplasm contained in the female gamete is used to supply the developing zygote with nutrients during the period between fertilization and implantation into the uterus. Interestingly, sperm contribute only DNA at fertilization —not cytoplasm. Therefore, the cytoplasm and all of the cytoplasmic organelles in the developing embryo are of maternal origin. This includes mitochondria, which contain their own DNA. Scientific research in the 1980s determined that mitochondrial DNA was maternally inherited, meaning that you can trace your mitochondrial DNA directly to your mother, her mother, and so on back through your female ancestors.
Mapping Human History with Mitochondrial DNA
When we talk about human DNA, we’re usually referring to nuclear DNA that is, the DNA coiled into chromosomal bundles in the nucleus of our cells. We inherit half of our nuclear DNA from our father, and half from our mother. However, mitochondrial DNA (mtDNA) comes only from the mitochondria in the cytoplasm of the fat ovum we inherit from our mother. She received her mtDNA from her mother, who got it from her mother, and so on. Each of our cells contains approximately 1700 mitochondria, with each mitochondrion packed with mtDNA containing approximately 37 genes.
Mutations (changes) in mtDNA occur spontaneously in a somewhat organized pattern at regular intervals in human history. By analyzing these mutational relationships, researchers have been able to determine that we can all trace our ancestry back to one woman who lived in Africa about 200,000 years ago. Scientists have given this woman the biblical name Eve, although she is not, of course, the first Homo sapiens female. More precisely, she is our most recent common ancestor through matrilineal descent.
This doesn’t mean that everyone’s mtDNA today looks exactly like that of our ancestral Eve. Because of the spontaneous mutations in mtDNA that have occurred over the centuries, researchers can map different “branches” off of the “main trunk” of our mtDNA family tree. Your mtDNA might have a pattern of mutations that aligns more closely with one branch, and your neighbor’s may align with another branch. Still, all branches eventually lead back to Eve.
But what happened to the mtDNA of all of the other Homo sapiens females who were living at the time of Eve? Researchers explain that, over the centuries, their female descendants died childless or with only male children, and thus, their maternal line—and its mtDNA—ended.
Again, ovarian follicles are oocytes and their supporting cells. They grow and develop in a process called folliculogenesis , which typically leads to ovulation of one follicle approximately every 28 days, along with death to multiple other follicles. The death of ovarian follicles is called atresia, and can occur at any point during follicular development. Recall that, a female infant at birth will have one to two million oocytes within her ovarian follicles, and that this number declines throughout life until menopause, when no follicles remain. As you’ll see next, follicles progress from primordial, to primary, to secondary and tertiary stages prior to ovulation—with the oocyte inside the follicle remaining as a primary oocyte until right before ovulation.
Folliculogenesis begins with follicles in a resting state. These small primordial follicles are present in newborn females and are the prevailing follicle type in the adult ovary (Figure 27.12). Primordial follicles have only a single flat layer of support cells, called granulosa cells , that surround the oocyte, and they can stay in this resting state for years—some until right before menopause.
After puberty, a few primordial follicles will respond to a recruitment signal each day, and will join a pool of immature growing follicles called primary follicles . Primary follicles start with a single layer of granulosa cells, but the granulosa cells then become active and transition from a flat or squamous shape to a rounded, cuboidal shape as they increase in size and proliferate. As the granulosa cells divide, the follicles—now called secondary follicles (see Figure 27.12)—increase in diameter, adding a new outer layer of connective tissue, blood vessels, and theca cells —cells that work with the granulosa cells to produce estrogens.
Within the growing secondary follicle, the primary oocyte now secretes a thin acellular membrane called the zona pellucida that will play a critical role in fertilization. A thick fluid, called follicular fluid, that has formed between the granulosa cells also begins to collect into one large pool, or antrum . Follicles in which the antrum has become large and fully formed are considered tertiary follicles (or antral follicles). Several follicles reach the tertiary stage at the same time, and most of these will undergo atresia. The one that does not die will continue to grow and develop until ovulation, when it will expel its secondary oocyte surrounded by several layers of granulosa cells from the ovary. Keep in mind that most follicles don’t make it to this point. In fact, roughly 99 percent of the follicles in the ovary will undergo atresia, which can occur at any stage of folliculogenesis.
Hormonal Control of the Ovarian Cycle
The process of development that we have just described, from primordial follicle to early tertiary follicle, takes approximately two months in humans. The final stages of development of a small cohort of tertiary follicles, ending with ovulation of a secondary oocyte, occur over a course of approximately 28 days. These changes are regulated by many of the same hormones that regulate the male reproductive system, including GnRH, LH, and FSH.
As in men, the hypothalamus produces GnRH, a hormone that signals the anterior pituitary gland to produce the gonadotropins FSH and LH (Figure 27.13). These gonadotropins leave the pituitary and travel through the bloodstream to the ovaries, where they bind to receptors on the granulosa and theca cells of the follicles. FSH stimulates the follicles to grow (hence its name of follicle-stimulating hormone), and the five or six tertiary follicles expand in diameter. The release of LH also stimulates the granulosa and theca cells of the follicles to produce the sex steroid hormone estradiol, a type of estrogen. This phase of the ovarian cycle, when the tertiary follicles are growing and secreting estrogen, is known as the follicular phase.
The more granulosa and theca cells a follicle has (that is, the larger and more developed it is), the more estrogen it will produce in response to LH stimulation. As a result of these large follicles producing large amounts of estrogen, systemic plasma estrogen concentrations increase. Following a classic negative feedback loop, the high concentrations of estrogen will stimulate the hypothalamus and pituitary to reduce the production of GnRH, LH, and FSH. Because the large tertiary follicles require FSH to grow and survive at this point, this decline in FSH caused by negative feedback leads most of them to die (atresia). Typically only one follicle, now called the dominant follicle, will survive this reduction in FSH, and this follicle will be the one that releases an oocyte. Scientists have studied many factors that lead to a particular follicle becoming dominant: size, the number of granulosa cells, and the number of FSH receptors on those granulosa cells all contribute to a follicle becoming the one surviving dominant follicle.
When only the one dominant follicle remains in the ovary, it again begins to secrete estrogen. It produces more estrogen than all of the developing follicles did together before the negative feedback occurred. It produces so much estrogen that the normal negative feedback doesn’t occur. Instead, these extremely high concentrations of systemic plasma estrogen trigger a regulatory switch in the anterior pituitary that responds by secreting large amounts of LH and FSH into the bloodstream (see Figure 27.13). The positive feedback loop by which more estrogen triggers release of more LH and FSH only occurs at this point in the cycle.
It is this large burst of LH (called the LH surge) that leads to ovulation of the dominant follicle. The LH surge induces many changes in the dominant follicle, including stimulating the resumption of meiosis of the primary oocyte to a secondary oocyte. As noted earlier, the polar body that results from unequal cell division simply degrades. The LH surge also triggers proteases (enzymes that cleave proteins) to break down structural proteins in the ovary wall on the surface of the bulging dominant follicle. This degradation of the wall, combined with pressure from the large, fluid-filled antrum, results in the expulsion of the oocyte surrounded by granulosa cells into the peritoneal cavity. This release is ovulation.
In the next section, you will follow the ovulated oocyte as it travels toward the uterus, but there is one more important event that occurs in the ovarian cycle. The surge of LH also stimulates a change in the granulosa and theca cells that remain in the follicle after the oocyte has been ovulated. This change is called luteinization (recall that the full name of LH is luteinizing hormone), and it transforms the collapsed follicle into a new endocrine structure called the corpus luteum , a term meaning “yellowish body” (see Figure 27.12). Instead of estrogen, the luteinized granulosa and theca cells of the corpus luteum begin to produce large amounts of the sex steroid hormone progesterone, a hormone that is critical for the establishment and maintenance of pregnancy. Progesterone triggers negative feedback at the hypothalamus and pituitary, which keeps GnRH, LH, and FSH secretions low, so no new dominant follicles develop at this time.
The post-ovulatory phase of progesterone secretion is known as the luteal phase of the ovarian cycle. If pregnancy does not occur within 10 to 12 days, the corpus luteum will stop secreting progesterone and degrade into the corpus albicans , a nonfunctional “whitish body” that will disintegrate in the ovary over a period of several months. During this time of reduced progesterone secretion, FSH and LH are once again stimulated, and the follicular phase begins again with a new cohort of early tertiary follicles beginning to grow and secrete estrogen.
The Uterine Tubes
The uterine tubes (also called fallopian tubes or oviducts) serve as the conduit of the oocyte from the ovary to the uterus (Figure 27.14). Each of the two uterine tubes is close to, but not directly connected to, the ovary and divided into sections. The isthmus is the narrow medial end of each uterine tube that is connected to the uterus. The wide distal infundibulum flares out with slender, finger-like projections called fimbriae . The middle region of the tube, called the ampulla , is where fertilization often occurs. The uterine tubes also have three layers: an outer serosa, a middle smooth muscle layer, and an inner mucosal layer. In addition to its mucus-secreting cells, the inner mucosa contains ciliated cells that beat in the direction of the uterus, producing a current that will be critical to move the oocyte.
Following ovulation, the secondary oocyte surrounded by a few granulosa cells is released into the peritoneal cavity. The nearby uterine tube, either left or right, receives the oocyte. Unlike sperm, oocytes lack flagella, and therefore cannot move on their own. So how do they travel into the uterine tube and toward the uterus? High concentrations of estrogen that occur around the time of ovulation induce contractions of the smooth muscle along the length of the uterine tube. These contractions occur every 4 to 8 seconds, and the result is a coordinated movement that sweeps the surface of the ovary and the pelvic cavity. Current flowing toward the uterus is generated by coordinated beating of the cilia that line the outside and lumen of the length of the uterine tube. These cilia beat more strongly in response to the high estrogen concentrations that occur around the time of ovulation. As a result of these mechanisms, the oocyte–granulosa cell complex is pulled into the interior of the tube. Once inside, the muscular contractions and beating cilia move the oocyte slowly toward the uterus. When fertilization does occur, sperm typically meet the egg while it is still moving through the ampulla.
Watch this video to observe ovulation and its initiation in response to the release of FSH and LH from the pituitary gland. What specialized structures help guide the oocyte from the ovary into the uterine tube?
If the oocyte is successfully fertilized, the resulting zygote will begin to divide into two cells, then four, and so on, as it makes its way through the uterine tube and into the uterus. There, it will implant and continue to grow. If the egg is not fertilized, it will simply degrade—either in the uterine tube or in the uterus, where it may be shed with the next menstrual period.
The open-ended structure of the uterine tubes can have significant health consequences if bacteria or other contagions enter through the vagina and move through the uterus, into the tubes, and then into the pelvic cavity. If this is left unchecked, a bacterial infection (sepsis) could quickly become life-threatening. The spread of an infection in this manner is of special concern when unskilled practitioners perform abortions in non-sterile conditions. Sepsis is also associated with sexually transmitted bacterial infections, especially gonorrhea and chlamydia. These increase a woman’s risk for pelvic inflammatory disease (PID), infection of the uterine tubes or other reproductive organs. Even when resolved, PID can leave scar tissue in the tubes, leading to infertility.
Watch this series of videos to look at the movement of the oocyte through the ovary. The cilia in the uterine tube promote movement of the oocyte. What would likely occur if the cilia were paralyzed at the time of ovulation?
The Uterus and Cervix
The uterus is the muscular organ that nourishes and supports the growing embryo (see Figure 27.14). Its average size is approximately 5 cm wide by 7 cm long (approximately 2 in by 3 in) when a female is not pregnant. It has three sections. The portion of the uterus superior to the opening of the uterine tubes is called the fundus . The middle section of the uterus is called the body of uterus (or corpus). The cervix is the narrow inferior portion of the uterus that projects into the vagina. The cervix produces mucus secretions that become thin and stringy under the influence of high systemic plasma estrogen concentrations, and these secretions can facilitate sperm movement through the reproductive tract.
Several ligaments maintain the position of the uterus within the abdominopelvic cavity. The broad ligament is a fold of peritoneum that serves as a primary support for the uterus, extending laterally from both sides of the uterus and attaching it to the pelvic wall. The round ligament attaches to the uterus near the uterine tubes, and extends to the labia majora. Finally, the uterosacral ligament stabilizes the uterus posteriorly by its connection from the cervix to the pelvic wall.
The wall of the uterus is made up of three layers. The most superficial layer is the serous membrane, or perimetrium , which consists of epithelial tissue that covers the exterior portion of the uterus. The middle layer, or myometrium , is a thick layer of smooth muscle responsible for uterine contractions. Most of the uterus is myometrial tissue, and the muscle fibers run horizontally, vertically, and diagonally, allowing the powerful contractions that occur during labor and the less powerful contractions (or cramps) that help to expel menstrual blood during a woman’s period. Anteriorly directed myometrial contractions also occur near the time of ovulation, and are thought to possibly facilitate the transport of sperm through the female reproductive tract.
The innermost layer of the uterus is called the endometrium . The endometrium contains a connective tissue lining, the lamina propria, which is covered by epithelial tissue that lines the lumen. Structurally, the endometrium consists of two layers: the stratum basalis and the stratum functionalis (the basal and functional layers). The stratum basalis layer is part of the lamina propria and is adjacent to the myometrium this layer does not shed during menses. In contrast, the thicker stratum functionalis layer contains the glandular portion of the lamina propria and the endothelial tissue that lines the uterine lumen. It is the stratum functionalis that grows and thickens in response to increased levels of estrogen and progesterone. In the luteal phase of the menstrual cycle, special branches off of the uterine artery called spiral arteries supply the thickened stratum functionalis. This inner functional layer provides the proper site of implantation for the fertilized egg, and—should fertilization not occur—it is only the stratum functionalis layer of the endometrium that sheds during menstruation.
Recall that during the follicular phase of the ovarian cycle, the tertiary follicles are growing and secreting estrogen. At the same time, the stratum functionalis of the endometrium is thickening to prepare for a potential implantation. The post-ovulatory increase in progesterone, which characterizes the luteal phase, is key for maintaining a thick stratum functionalis. As long as a functional corpus luteum is present in the ovary, the endometrial lining is prepared for implantation. Indeed, if an embryo implants, signals are sent to the corpus luteum to continue secreting progesterone to maintain the endometrium, and thus maintain the pregnancy. If an embryo does not implant, no signal is sent to the corpus luteum and it degrades, ceasing progesterone production and ending the luteal phase. Without progesterone, the endometrium thins and, under the influence of prostaglandins, the spiral arteries of the endometrium constrict and rupture, preventing oxygenated blood from reaching the endometrial tissue. As a result, endometrial tissue dies and blood, pieces of the endometrial tissue, and white blood cells are shed through the vagina during menstruation, or the menses . The first menses after puberty, called menarche , can occur either before or after the first ovulation.
The Menstrual Cycle
Now that we have discussed the maturation of the cohort of tertiary follicles in the ovary, the build-up and then shedding of the endometrial lining in the uterus, and the function of the uterine tubes and vagina, we can put everything together to talk about the three phases of the menstrual cycle —the series of changes in which the uterine lining is shed, rebuilds, and prepares for implantation.
The timing of the menstrual cycle starts with the first day of menses, referred to as day one of a woman’s period. Cycle length is determined by counting the days between the onset of bleeding in two subsequent cycles. Because the average length of a woman’s menstrual cycle is 28 days, this is the time period used to identify the timing of events in the cycle. However, the length of the menstrual cycle varies among women, and even in the same woman from one cycle to the next, typically from 21 to 32 days.
Just as the hormones produced by the granulosa and theca cells of the ovary “drive” the follicular and luteal phases of the ovarian cycle, they also control the three distinct phases of the menstrual cycle. These are the menses phase, the proliferative phase, and the secretory phase.
The menses phase of the menstrual cycle is the phase during which the lining is shed that is, the days that the woman menstruates. Although it averages approximately five days, the menses phase can last from 2 to 7 days, or longer. As shown in Figure 27.15, the menses phase occurs during the early days of the follicular phase of the ovarian cycle, when progesterone, FSH, and LH levels are low. Recall that progesterone concentrations decline as a result of the degradation of the corpus luteum, marking the end of the luteal phase. This decline in progesterone triggers the shedding of the stratum functionalis of the endometrium.
Once menstrual flow ceases, the endometrium begins to proliferate again, marking the beginning of the proliferative phase of the menstrual cycle (see Figure 27.15). It occurs when the granulosa and theca cells of the tertiary follicles begin to produce increased amounts of estrogen. These rising estrogen concentrations stimulate the endometrial lining to rebuild.
Recall that the high estrogen concentrations will eventually lead to a decrease in FSH as a result of negative feedback, resulting in atresia of all but one of the developing tertiary follicles. The switch to positive feedback—which occurs with the elevated estrogen production from the dominant follicle—then stimulates the LH surge that will trigger ovulation. In a typical 28-day menstrual cycle, ovulation occurs on day 14. Ovulation marks the end of the proliferative phase as well as the end of the follicular phase.
In addition to prompting the LH surge, high estrogen levels increase the uterine tube contractions that facilitate the pick-up and transfer of the ovulated oocyte. High estrogen levels also slightly decrease the acidity of the vagina, making it more hospitable to sperm. In the ovary, the luteinization of the granulosa cells of the collapsed follicle forms the progesterone-producing corpus luteum, marking the beginning of the luteal phase of the ovarian cycle. In the uterus, progesterone from the corpus luteum begins the secretory phase of the menstrual cycle, in which the endometrial lining prepares for implantation (see Figure 27.15). Over the next 10 to 12 days, the endometrial glands secrete a fluid rich in glycogen. If fertilization has occurred, this fluid will nourish the ball of cells now developing from the zygote. At the same time, the spiral arteries develop to provide blood to the thickened stratum functionalis.
If no pregnancy occurs within approximately 10 to 12 days, the corpus luteum will degrade into the corpus albicans. Levels of both estrogen and progesterone will fall, and the endometrium will grow thinner. Prostaglandins will be secreted that cause constriction of the spiral arteries, reducing oxygen supply. The endometrial tissue will die, resulting in menses—or the first day of the next cycle.
Disorders of the.
Female Reproductive System
Research over many years has confirmed that cervical cancer is most often caused by a sexually transmitted infection with human papillomavirus (HPV). There are over 100 related viruses in the HPV family, and the characteristics of each strain determine the outcome of the infection. In all cases, the virus enters body cells and uses its own genetic material to take over the host cell’s metabolic machinery and produce more virus particles.
HPV infections are common in both men and women. Indeed, a recent study determined that 42.5 percent of females had HPV at the time of testing. These women ranged in age from 14 to 59 years and differed in race, ethnicity, and number of sexual partners. Of note, the prevalence of HPV infection was 53.8 percent among women aged 20 to 24 years, the age group with the highest infection rate.
HPV strains are classified as high or low risk according to their potential to cause cancer. Though most HPV infections do not cause disease, the disruption of normal cellular functions in the low-risk forms of HPV can cause the male or female human host to develop genital warts. Often, the body is able to clear an HPV infection by normal immune responses within 2 years. However, the more serious, high-risk infection by certain types of HPV can result in cancer of the cervix (Figure 27.16). Infection with either of the cancer-causing variants HPV 16 or HPV 18 has been linked to more than 70 percent of all cervical cancer diagnoses. Although even these high-risk HPV strains can be cleared from the body over time, infections persist in some individuals. If this happens, the HPV infection can influence the cells of the cervix to develop precancerous changes.
Risk factors for cervical cancer include having unprotected sex having multiple sexual partners a first sexual experience at a younger age, when the cells of the cervix are not fully mature failure to receive the HPV vaccine a compromised immune system and smoking. The risk of developing cervical cancer is doubled with cigarette smoking.
When the high-risk types of HPV enter a cell, two viral proteins are used to neutralize proteins that the host cells use as checkpoints in the cell cycle. The best studied of these proteins is p53. In a normal cell, p53 detects DNA damage in the cell’s genome and either halts the progression of the cell cycle—allowing time for DNA repair to occur—or initiates apoptosis. Both of these processes prevent the accumulation of mutations in a cell’s genome. High-risk HPV can neutralize p53, keeping the cell in a state in which fast growth is possible and impairing apoptosis, allowing mutations to accumulate in the cellular DNA.
The prevalence of cervical cancer in the United States is very low because of regular screening exams called pap smears. Pap smears sample cells of the cervix, allowing the detection of abnormal cells. If pre-cancerous cells are detected, there are several highly effective techniques that are currently in use to remove them before they pose a danger. However, women in developing countries often do not have access to regular pap smears. As a result, these women account for as many as 80 percent of the cases of cervical cancer worldwide.
In 2006, the first vaccine against the high-risk types of HPV was approved. There are now two HPV vaccines available: Gardasil ® and Cervarix ® . Whereas these vaccines were initially only targeted for women, because HPV is sexually transmitted, both men and women require vaccination for this approach to achieve its maximum efficacy. A recent study suggests that the HPV vaccine has cut the rates of HPV infection by the four targeted strains at least in half. Unfortunately, the high cost of manufacturing the vaccine is currently limiting access to many women worldwide.
Whereas the breasts are located far from the other female reproductive organs, they are considered accessory organs of the female reproductive system. The function of the breasts is to supply milk to an infant in a process called lactation. The external features of the breast include a nipple surrounded by a pigmented areola (Figure 27.17), whose coloration may deepen during pregnancy. The areola is typically circular and can vary in size from 25 to 100 mm in diameter. The areolar region is characterized by small, raised areolar glands that secrete lubricating fluid during lactation to protect the nipple from chafing. When a baby nurses, or draws milk from the breast, the entire areolar region is taken into the mouth.
Breast milk is produced by the mammary glands , which are modified sweat glands. The milk itself exits the breast through the nipple via 15 to 20 lactiferous ducts that open on the surface of the nipple. These lactiferous ducts each extend to a lactiferous sinus that connects to a glandular lobe within the breast itself that contains groups of milk-secreting cells in clusters called alveoli (see Figure 27.17). The clusters can change in size depending on the amount of milk in the alveolar lumen. Once milk is made in the alveoli, stimulated myoepithelial cells that surround the alveoli contract to push the milk to the lactiferous sinuses. From here, the baby can draw milk through the lactiferous ducts by suckling. The lobes themselves are surrounded by fat tissue, which determines the size of the breast breast size differs between individuals and does not affect the amount of milk produced. Supporting the breasts are multiple bands of connective tissue called suspensory ligaments that connect the breast tissue to the dermis of the overlying skin.
During the normal hormonal fluctuations in the menstrual cycle, breast tissue responds to changing levels of estrogen and progesterone, which can lead to swelling and breast tenderness in some individuals, especially during the secretory phase. If pregnancy occurs, the increase in hormones leads to further development of the mammary tissue and enlargement of the breasts.
Hormonal Birth Control
Birth control pills take advantage of the negative feedback system that regulates the ovarian and menstrual cycles to stop ovulation and prevent pregnancy. Typically they work by providing a constant level of both estrogen and progesterone, which negatively feeds back onto the hypothalamus and pituitary, thus preventing the release of FSH and LH. Without FSH, the follicles do not mature, and without the LH surge, ovulation does not occur. Although the estrogen in birth control pills does stimulate some thickening of the endometrial wall, it is reduced compared with a normal cycle and is less likely to support implantation.
Some birth control pills contain 21 active pills containing hormones, and 7 inactive pills (placebos). The decline in hormones during the week that the woman takes the placebo pills triggers menses, although it is typically lighter than a normal menstrual flow because of the reduced endometrial thickening. Newer types of birth control pills have been developed that deliver low-dose estrogens and progesterone for the entire cycle (these are meant to be taken 365 days a year), and menses never occurs. While some women prefer to have the proof of a lack of pregnancy that a monthly period provides, menstruation every 28 days is not required for health reasons, and there are no reported adverse effects of not having a menstrual period in an otherwise healthy individual.
Because birth control pills function by providing constant estrogen and progesterone levels and disrupting negative feedback, skipping even just one or two pills at certain points of the cycle (or even being several hours late taking the pill) can lead to an increase in FSH and LH and result in ovulation. It is important, therefore, that the woman follow the directions on the birth control pill package to successfully prevent pregnancy.
Aging and the.
Female Reproductive System
Female fertility (the ability to conceive) peaks when women are in their twenties, and is slowly reduced until a women reaches 35 years of age. After that time, fertility declines more rapidly, until it ends completely at the end of menopause. Menopause is the cessation of the menstrual cycle that occurs as a result of the loss of ovarian follicles and the hormones that they produce. A woman is considered to have completed menopause if she has not menstruated in a full year. After that point, she is considered postmenopausal. The average age for this change is consistent worldwide at between 50 and 52 years of age, but it can normally occur in a woman’s forties, or later in her fifties. Poor health, including smoking, can lead to earlier loss of fertility and earlier menopause.
As a woman reaches the age of menopause, depletion of the number of viable follicles in the ovaries due to atresia affects the hormonal regulation of the menstrual cycle. During the years leading up to menopause, there is a decrease in the levels of the hormone inhibin, which normally participates in a negative feedback loop to the pituitary to control the production of FSH. The menopausal decrease in inhibin leads to an increase in FSH. The presence of FSH stimulates more follicles to grow and secrete estrogen. Because small, secondary follicles also respond to increases in FSH levels, larger numbers of follicles are stimulated to grow however, most undergo atresia and die. Eventually, this process leads to the depletion of all follicles in the ovaries, and the production of estrogen falls off dramatically. It is primarily the lack of estrogens that leads to the symptoms of menopause.
The earliest changes occur during the menopausal transition, often referred to as peri-menopause, when a women’s cycle becomes irregular but does not stop entirely. Although the levels of estrogen are still nearly the same as before the transition, the level of progesterone produced by the corpus luteum is reduced. This decline in progesterone can lead to abnormal growth, or hyperplasia, of the endometrium. This condition is a concern because it increases the risk of developing endometrial cancer. Two harmless conditions that can develop during the transition are uterine fibroids, which are benign masses of cells, and irregular bleeding. As estrogen levels change, other symptoms that occur are hot flashes and night sweats, trouble sleeping, vaginal dryness, mood swings, difficulty focusing, and thinning of hair on the head along with the growth of more hair on the face. Depending on the individual, these symptoms can be entirely absent, moderate, or severe.
After menopause, lower amounts of estrogens can lead to other changes. Cardiovascular disease becomes as prevalent in women as in men, possibly because estrogens reduce the amount of cholesterol in the blood vessels. When estrogen is lacking, many women find that they suddenly have problems with high cholesterol and the cardiovascular issues that accompany it. Osteoporosis is another problem because bone density decreases rapidly in the first years after menopause. The reduction in bone density leads to a higher incidence of fractures.
Hormone therapy (HT), which employs medication (synthetic estrogens and progestins) to increase estrogen and progestin levels, can alleviate some of the symptoms of menopause. In 2002, the Women’s Health Initiative began a study to observe women for the long-term outcomes of hormone replacement therapy over 8.5 years. However, the study was prematurely terminated after 5.2 years because of evidence of a higher than normal risk of breast cancer in patients taking estrogen-only HT. The potential positive effects on cardiovascular disease were also not realized in the estrogen-only patients. The results of other hormone replacement studies over the last 50 years, including a 2012 study that followed over 1,000 menopausal women for 10 years, have shown cardiovascular benefits from estrogen and no increased risk for cancer. Some researchers believe that the age group tested in the 2002 trial may have been too old to benefit from the therapy, thus skewing the results. In the meantime, intense debate and study of the benefits and risks of replacement therapy is ongoing. Current guidelines approve HT for the reduction of hot flashes or flushes, but this treatment is generally only considered when women first start showing signs of menopausal changes, is used in the lowest dose possible for the shortest time possible (5 years or less), and it is suggested that women on HT have regular pelvic and breast exams.
Diagnosis of Vaginitis
Diagnosis of vaginitis typically begins with symptoms reported by the patient. This may be followed by a microscopic examination or culture of the vaginal discharge in order to identify the specific cause. The colour, consistency, acidity, and other characteristics of the discharge may be predictive of the causative agent. For example, infection with Candida albicans may cause a cottage cheese-like discharge with a low pH , whereas infection with Gardnerella vaginalis may cause a discharge with a fish-like odor and a high pH.
What is this abbreviation CT in female reproductive system - Biology
Q. Is there any difference between brown eggs and white eggs? My fitness instructor suggested me to have brown eggs instead of white eggs so is there any difference between brown eggs and white eggs?
Q. why the renal doctor told my husband that he needs to eat a dozen of egg a week for protein,how it will help? it won`t afect his cholesterol,also i would like to know what role the protein plays on his treatment and what other foot its rich in protein that he can can take,without causing problems to his health.
Q. How can I catch Salmonella? Yesterday I ate a mousse which was made from raw eggs. Could I have caught Salmonella?
A. Salmonella infections usually resolve in 5-7 days and often do not require treatment unless the patient becomes severely dehydrated or the infection spreads from the intestines. Persons with severe diarrhea may require rehydration, often with intravenous fluids (IV). Antibiotics are not usually necessary unless the infection spreads from the intestines.