Puberty begins at age 8 to 10 for most girls in the United States. It is triggered by rising levels of GnRH, stimulates anterior lobe of pituitary to produce: FSH and LH. FSH stimulates developing ovarian follicles and they begin to secrete estrogen, progesterone, inhibin, and a small amount of androgen. Thelarche is the onset of breast development is the earliest noticeable sign of puberty. Pubarche is the appearance of pubic and axillary hair, sebaceous glands, and axillary glands. Menarche is the first menstrual period, which requires about 17% body fat in teenagers and 22% in adults. Estradiol stimulates vaginal metaplasia, growth of ovaries and secondary sex organs, growth hormone secretion, responsible for feminine physique because it stimulates the deposition of fat, and makes a girl’s skin thicker. Progesterone, primarily acts on the uterus preparing it for possible pregnancy in the second half of the menstrual cycle. Estrogens and progesterone suppress FSH and LH secretion through negative feedback. Inhibin selectively suppresses FSH secretion. Hormone secretion is distinctly cyclic and the hormones are secreted in sequence.
Oogensis is egg development. Oogensis produces haploid gametes by means of meiosis, distinctly cyclic event that normally releases one egg each month, accompanied by cyclic changes in hormone secretion, and cyclic changes in histological structure of the ovaries and uterus. Egg development resumes in adolescence. Embryonic development of ovary: female germ cells arise from yolk sac, colonize gonadal ridges the first 5 to 6 weeks of development, differentiate into oogonia and multiply until the fifth month, transform into primary oocytes: early meiosis I, most degenerate (atresia) by the time the girl is born, egg or ovum: any stage from the primary oocyte to the time of fertilization, by puberty, 400,000 oocytes remain. FSH stimulates monthly cohorts of oocytes to complete meiosis I. Each oocyte divides into two haploid daughter cells of unequal size and different destinies. It is important to produce an egg with as much cytoplasm as possible. If fertilized, it must divide repeatedly and produce numerous daughter cells.
Folliculogenesis is the development of the follicles around the egg that undergoes oogenesis. Primordial follicles: consists of a primary oocyte in early meiosis, surrounded by a single layer of squamous follicular cells, follicular cells connected to the oocyte by fine cytoplasmic processes for passage of nutrients and chemical signals, concentrated in the cortex of the ovary, most wait 13 to 50 years before they develop further, and adult ovary has 90% to 95% primordial follicles.
Primary follicles have larger oocytes and follicular cells that still form a single layer. Secondary follicles still have larger oocytes and follicular cells now stratified (granulosa cells). Zona pellucida is a layer of glycoprotein gel secreted by granulosa cells around the oocyte. Theca folliculi is the connective tissue around the granulosa cells condenses to form a fibrous husk. Mature (graafian) follicles are normally only one follicle from each month’s cohort becomes a mature follicles destined to ovulate and remainder degenerate.
Ovulation is the rupture of the mature follicle and the release of its egg and attendant cells, typically around day 14. Estradiol stimulates a surge of LH and a lesser spike of FSH by anterior pituitary. Ovulation takes only 2 to 3 minutes: Nipplelike stigma appears on ovary surface over follicle, seeps follicular fluid for 1 to 2 minutes, follicle bursts and remaining fluid oozes out carrying the secondary oocyte and cumulus oophorus, and normally swept up by ciliary current and taken into uterine tube.
Uterine tube prepares to catch the oocyte when it emerges, it swells the edema, its fimbriae envelop and caress the ovary in synchrony with the woman’s heartbeat, cilia create gentle current in the nearby peritoneal fluid, and many oocytes fall into the pelvic cavity and die. Couples attempting to conceive a child or avoid pregnancy need to be able to tell when ovulation occurs. LH surge occurs about 24 hours prior to ovulation, which can be detected with home testing kit. The best time for conception is within 24 hours after the cervical mucus changes and the basal temperature rises.
Spermatogenesis is the process of sperm in seminiferous tubules. It involves three main principals. One was being Remolding of a large germ cell into small, mobile sperm cells with flagella. The second principal would be the reduction of chromosome number by one-half in sperm cells. Lastly, the shuffling of genes so new combinations exist in sperm that are different from the parents. This ensures genetic variation in the off spring and four of the sperm cells are produced from one germ cell by meiosis. Hormonal control of spermatogenesis varies among species. In humans the mechanism are not completely understood, however it is known that initiation of spermatogenesis occurs at puberty due to the interaction of the hypothalamus, pituitary gland and Leydig cells. If the pituitary gland is removed, spermatogenesis can still be initiated by follicle stimulating hormone and testosterone.
Follicle stimulating hormone stimulates both the production of androgen binding protein by Sertoli cells, and the formation of the blood-testis barrier. Androgen binding protein is essential to concentrating testosterone in levels high enough to initiate and maintain spermatogenesis, which can be 20-50 times higher than the concentration found in blood. Follicle stimulating hormone may initiate the sequestering of testosterone in the testes, but once developed only testosterone is required to maintain spermatogenesis. The hormone inhibin acts to decrease the levels of follicle stimulating hormone. Studies from rodent models suggest that gonadotropin hormones (both LH and FSH) support the process of spermatogenesis by suppressing the proapoptotic signals and therefore promote spermatogenic cell survival. P
Pregnancy lasts about 40 weeks, counting from the first day of your last normal period. The weeks are grouped into three trimesters. During the first trimester, which is between week one and week 12, your body undergoes many changes. Hormonal changes affect almost every organ system in your body. Most women find the second trimester of pregnancy easier than the first (week 13 to 28). You might notice that symptoms like nausea and fatigue are going away. But other new, more noticeable changes to your body are now happening. Your abdomen will expand as the baby continues to grow. During the third trimester (week 29 to week 40), some of the same discomforts you had in your second trimester will continue. Because the baby is getting bigger and pressing on the mother’s organs, women often find that they have to go to the bathroom more frequently. Along with being pregnant, you will definitely notice major weight gain.
A lot of people like to use the term “eating for two”. While you are “eating for two”, you have to make sure that you are eating the proper foods. It is a must that you watch what you eat, considering you have another life growing inside of you. You need more protein, iron, calcium, and folic acid than you did before pregnancy. You also need more calories. But “eating for two” doesn’t mean eating twice as much. You will experience a lot of weight gain, but you should never go overboard.
Studies have shown that women who gain more than the recommended amount during pregnancy and who fail to lose this weight within six months after giving birth are at much higher risk of being obese nearly 10 years later. In addition to making healthy food choices, ask your doctor about taking a prenatal vitamin and mineral supplement every day to be sure you are getting enough of the nutrients your baby needs. You also can check the label on the foods you buy to see how much of a certain nutrient the product contains. Women who are pregnant need more of these nutrients than women who are not pregnant.
The process of normal human childbirth is categorized in three stages of labor: the shortening and dilation of the cervix, descent and birth of the infant, and birth of the placenta. Vaginal delivery is the most common and safest type of childbirth. When necessary in certain circumstances, forceps may be used to cup your baby’s head and help guide the baby through the birth canal. Vacuum delivery is another way to assist delivery and is similar to forceps delivery. In vacuum delivery, a plastic cup is applied to the baby’s head by suction and the health care provider gently pulls the baby from the birth canal. Caesarean delivery (C-section) may be necessary for the safety of you and your baby. Your baby is not in the head-down position, your baby is too large to pass through the pelvis, and your baby is in distress.
Labor occurs in three stages. When regular contractions begin, the baby moves down into the pelvis as the cervix both effaces and dilates. But each stage features some milestones that are true for every woman. The first stage begins with the onset of labor and ends when the cervix is fully opened. It is the longest stage of labor, usually lasting about 12 to 19 hours. The second stage involves pushing and delivery of your baby. It usually lasts 20 minutes to two hours. You will push hard during contractions, and rest between contractions.
The third stage involves delivery of the placenta (afterbirth). It is the shortest stage, lasting five to 30 minutes. Contractions will begin five to 30 minutes after birth, signaling that it’s time to deliver the placenta. Many natural methods help women to relax and make pain more manageable. Things women do to ease the pain include: Trying breathing and relaxation techniques, taking warm showers or baths, getting massages, Having the supportive care of a loved one, using a labor ball and listening to music.
Courtney from Study Moose
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