Female reproductive system
The female reproductive system is made up of the internal and external sex organs that function in reproduction of new offspring. In the human the female reproductive system is immature at birth and develops to maturity at puberty to be able to produce gametes, to carry a foetus to full term; the internal sex organs are the uterus, Fallopian tubes, ovaries. The uterus or womb accommodates the embryo; the uterus produces vaginal and uterine secretions which help the transit of sperm to the Fallopian tubes. The ovaries produce the ova; the external sex organs are known as the genitals and these are the organs of the vulva including the labia and vaginal opening. The vagina is connected to the uterus at the cervix. At certain intervals, the ovaries release an ovum, which passes through the Fallopian tube into the uterus. If, in this transit, it meets with sperm, a single sperm can enter and merge with the egg or ovum, fertilizing it into a zygote. Fertilization occurs in the Fallopian tubes and marks the beginning of embryogenesis.
The zygote will divide over enough generations of cells to form a blastocyst, which implants itself in the wall of the uterus. This begins the period of gestation and the embryo will continue to develop until full-term; when the foetus has developed enough to survive outside the uterus, the cervix dilates and contractions of the uterus propel the newborn through the birth canal. The corresponding equivalent among males is the male reproductive system; the vulva consists of all of the external parts and tissues and includes the mons pubis, pudendal cleft, labia majora, labia minora, Bartholin's glands and vaginal opening. The female internal reproductive organs are the vagina, Fallopian tubes, ovaries; the vagina is a fibromuscular canal leading from the outside of the body to the cervix of the uterus or womb. It is referred to as the birth canal in the context of pregnancy; the vagina accommodates the male penis during sexual intercourse. Semen containing spermatozoa is ejaculated from the male at orgasm, into the vagina enabling fertilization of the egg cell to take place.
The cervix is the neck of the uterus, the lower, narrow portion where it joins with the upper part of the vagina. It protrudes through the upper anterior vaginal wall. Half its length is visible, the remainder lies above the vagina beyond view; the vagina has a thick layer outside and it is the opening where the fetus emerges during delivery. The uterus or womb is the major female reproductive organ; the uterus provides mechanical protection, nutritional support, waste removal for the developing embryo and fetus. In addition, contractions in the muscular wall of the uterus are important in pushing out the fetus at the time of birth; the uterus contains three suspensory ligaments that help stabilize the position of the uterus and limits its range of movement. The uterosacral ligaments keep the body from moving anteriorly; the round ligaments restrict posterior movement of the uterus. The cardinal ligaments prevent the inferior movement of the uterus; the uterus is a pear-shaped muscular organ. Its major function is to accept a fertilized ovum which becomes implanted into the endometrium, derives nourishment from blood vessels which develop for this purpose.
The fertilized ovum develops into a fetus and gestates until childbirth. If the egg does not embed in the wall of the uterus, a female begins menstruation; the Fallopian tubes are two tubes leading from the ovaries into the uterus. On maturity of an ovum, the follicle and the ovary's wall rupture, allowing the ovum to escape and enter the Fallopian tube. There it travels toward the uterus, pushed along by movements of cilia on the inner lining of the tubes; this trip takes days. If the ovum is fertilized while in the Fallopian tube it implants in the endometrium when it reaches the uterus, which signals the beginning of pregnancy; the ovaries are paired organs located near the lateral walls of the pelvic cavity. These organs are responsible for the secretion of hormones; the process by which the egg cell is released is called ovulation. The speed of ovulation is impacts directly to the length of a menstrual cycle. After ovulation, the egg cell is captured by the Fallopian tube, after traveling down the Fallopian tube to the uterus being fertilized on its way by an incoming sperm.
During fertilization the egg cell plays a role. The egg can absorb the sperm and fertilization can begin; the Fallopian tubes are lined with small hairs to help the egg cell travel. The reproductive tract is the lumen that starts as a single pathway through the vagina, splitting up into two lumens in the uterus, both of which continue through the Fallopian tubes, ending at the distal ostia that open into the abdominal cavity. In the absence of fertilization, the ovum will traverse the entire reproductive tract from the fallopian tube until exiting the vagina through menstruation; the reproductive tract can be used for various transluminal procedures such as fertiloscopy, intrauterine insemination, transluminal sterilization. Chromosome characteristics determine the genetic sex of a fetus at conception; this is based on the 23rd pair of chromosomes, inherited. Since the mother's egg
Obstetrics is the field of study concentrated on pregnancy and the postpartum period. As a medical specialty, obstetrics is combined with gynecology under the discipline known as obstetrics and gynecology, a surgical field. Prenatal care is important in screening for various complications of pregnancy; this includes routine office visits with physical exams and routine lab tests: Complete blood count Blood type General antibody screen for HDN Rh D negative antenatal patients should receive RhoGam at 28 weeks to prevent Rh disease. Rapid plasma reagin to screen for syphilis Rubella antibody screen Hepatitis B surface antigen Gonorrhea and Chlamydia culture PPD for tuberculosis Pap smear Urinalysis and culture HIV screenGenetic screening for Down syndrome and trisomy 18, the national standard in the United States, is evolving away from the AFP-Quad screen for Down syndrome, done in the second trimester at 16–18 weeks; the newer integrated screen can be done at 10 plus weeks to 13 plus weeks with an ultrasound of the fetal neck and two chemicals PAPP-A and βHCG.
It gives an accurate risk profile early. A second blood screen at 15 to 20 weeks refines the risk more accurately; the cost is higher than an "AFP-quad" screen due to the ultrasound and second blood test, but it is quoted to have a 93% pick up rate as opposed to 88% for the standard AFP/QS. This is an evolving standard of care in the United States. MSAFP/quad. Screen – elevations, low numbers or odd patterns correlate with neural tube defect risk and increased risks of trisomy 18 or trisomy 21 Ultrasound either abdominal or transvaginal to assess cervix, placenta and baby Amniocentesis is the national standard for women over 35 or who reach 35 by mid pregnancy or who are at increased risk by family history or prior birth history. Hematocrit Group B Streptococcus screen. If positive, the woman receives IV penicillin or ampicillin while in labor—or, if she is allergic to penicillin, an alternative therapy, such as IV clindamycin or IV vancomycin. Glucose loading test – screens for gestational diabetes.
Most doctors do a sugar load in a drink form of 50 grams of glucose in cola, lime or orange and draw blood an hour later. The standard modified criteria have been lowered to 135 since the late 1980s. Obstetric ultrasonography is used for dating the gestational age of a pregnancy from the size of the fetus, determine the number of fetuses and placentae, evaluate for an ectopic pregnancy and first trimester bleeding, the most accurate dating being in first trimester before the growth of the foetus has been influenced by other factors. Ultrasound is used for detecting congenital anomalies and determining the biophysical profiles, which are easier to detect in the second trimester when the foetal structures are larger and more developed. Specialised ultrasound equipment can evaluate the blood flow velocity in the umbilical cord, looking to detect a decrease/absence/reversal or diastolic blood flow in the umbilical artery. X-rays and computerized tomography are not used in the first trimester, due to the ionizing radiation, which has teratogenic effects on the foetus.
No effects of magnetic resonance imaging on the foetus have been demonstrated, but this technique is too expensive for routine observation. Instead, obstetric ultrasonography is the imaging method of choice in the first trimester and throughout the pregnancy, because it emits no radiation, is portable, allows for realtime imaging; the safety of frequent ultrasound scanning has not be confirmed. Despite this, increasing numbers of women are choosing to have additional scans for no medical purpose, such as gender scans, 3D and 4D scans. A normal gestation would reveal a gestational sac, yolk sac, fetal pole; the gestational age can be assessed by evaluating the mean gestational sac diameter before week 6, the crown-rump length after week 6. Multiple gestation is evaluated by the number of placentae and amniotic sacs present. Other tools used for assessment include: Fetal screening is used to help assess the viability of the fetus, as well as congenital abnormalities. Fetal karyotype can be used for the screening of genetic diseases.
This can be obtained via amniocentesis or chorionic villus sampling Foetal haematocrit for the assessment of foetal anemia, Rh isoimmunization, or hydrops can be determined by percutaneous umbilical blood sampling, done by placing a needle through the abdomen into the uterus and taking a portion of the umbilical cord. Fetal lung maturity is associated with. Reduced production of surfactant indicates decreased lung maturity and is a high risk factor for infant respiratory distress syndrome. A lecithin:sphingomyelin ratio greater than 1.5 is associated with increased lung maturity. Nonstress test for fetal heart rate Oxytocin challenge test A pregnant woman may have intercurrent diseases, that is, other diseases or conditions that may become worse or be a potential risk to the pregnancy. Diabetes mellitus and pregnancy deals with the interactions of diabetes mellitus and pregnanc
American and British English spelling differences
Many of the differences between American and British English date back to a time when spelling standards had not yet developed. For instance, some spellings seen as "American" today were once used in Britain and some spellings seen as "British" were once used in the United States. A "British standard" began to emerge following the 1755 publication of Samuel Johnson's A Dictionary of the English Language, an "American standard" started following the work of Noah Webster and in particular his An American Dictionary of the English Language, first published in 1828. Webster's efforts at spelling reform were somewhat effective in his native country, resulting in certain well-known patterns of spelling differences between the American and British varieties of English. However, English-language spelling reform has been adopted otherwise, so modern English orthography varies somewhat between countries and is far from phonemic in any country. In the early 18th century, English spelling was inconsistent.
These differences became noticeable after the publishing of influential dictionaries. Today's British English spellings follow Johnson's A Dictionary of the English Language, while many American English spellings follow Webster's An American Dictionary of the English Language. Webster was a proponent of English spelling reform for reasons both nationalistic. In A Companion to the American Revolution, John Algeo notes: "it is assumed that characteristically American spellings were invented by Noah Webster, he was influential in popularizing certain spellings in America, but he did not originate them. Rather he chose existing options such as center and check for the simplicity, analogy or etymology". William Shakespeare's first folios, for example, used spellings like center and color as much as centre and colour. Webster did attempt to introduce some reformed spellings, as did the Simplified Spelling Board in the early 20th century, but most were not adopted. In Britain, the influence of those who preferred the Norman spellings of words proved to be decisive.
Spelling adjustments in the United Kingdom had little effect on today's American spellings and vice versa. For the most part, the spelling systems of most Commonwealth countries and Ireland resemble the British system. In Canada, the spelling system can be said to follow both British and American forms, Canadians are somewhat more tolerant of foreign spellings when compared with other English-speaking nationalities. Australian spelling has strayed from British spelling, with some American spellings incorporated as standard. New Zealand spelling is identical to British spelling, except in the word fiord. There is an increasing use of macrons in words that originated in Māori and an unambiguous preference for -ise endings. Most words ending in an unstressed -our in British English end in -or in American English. Wherever the vowel is unreduced in pronunciation, e.g. contour, velour and troubadour the spelling is consistent everywhere. Most words of this kind came from Latin, they were first adopted into English from early Old French, the ending was spelled -or or -ur.
After the Norman conquest of England, the ending became -our to match the Old French spelling. The -our ending was not only used in new English borrowings, but was applied to the earlier borrowings that had used -or. However, -or was still sometimes found, the first three folios of Shakespeare's plays used both spellings before they were standardised to -our in the Fourth Folio of 1685. After the Renaissance, new borrowings from Latin were taken up with their original -or ending and many words once ending in -our went back to -or. Many words of the -our/or group do not have a Latin counterpart; some 16th- and early 17th-century British scholars indeed insisted that -or be used for words from Latin and -our for French loans. Webster's 1828 dictionary had only -or and is given much of the credit for the adoption of this form in the United States. By contrast, Johnson's 1755 dictionary used -our for all words still so spelled in Britain, but for words where the u has since been dropped: ambassadour, governour, inferiour, superiour.
Johnson, unlike Webster, was not an advocate of spelling reform, but chose the spelling best derived, as he saw it, from among the variations in his sources. He preferred French over Latin spellings because, as he put it, "the French supplied us". English speakers who moved to America took these preferences with them, H. L. Mencken notes that "honor appears in the 1776 Declaration of Independence, but it seems to have got there rather by accident than by design. In Jefferson's original draft it is spelled "honour". In Britain, examples of color, behavior and neighbor appear in Old Bailey court records from the 17th and 18th centuries, whereas there are thousands of examples of their -our counterparts. One notable exception is honor. Honor and honour were frequent in Br
A diuretic is any substance that promotes diuresis, the increased production of urine. This includes forced diuresis. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way. Alternatively, an antidiuretic, such as vasopressin, is an agent or drug which reduces the excretion of water in urine. In medicine, diuretics are used to treat heart failure, liver cirrhosis, influenza, water poisoning, certain kidney diseases; some diuretics, such as acetazolamide, help to make the urine more alkaline and are helpful in increasing excretion of substances such as aspirin in cases of overdose or poisoning. Diuretics are sometimes abused by people with an eating disorder people with bulimia nervosa, with the goal of losing weight; the antihypertensive actions of some diuretics are independent of their diuretic effect. That is, the reduction in blood pressure is not due to decreased blood volume resulting from increased urine production, but occurs through other mechanisms and at lower doses than that required to produce diuresis.
Indapamide was designed with this in mind, has a larger therapeutic window for hypertension than most other diuretics. High ceiling diuretics may cause a substantial diuresis – up to 20% of the filtered load of NaCl and water; this is large in comparison to normal renal sodium reabsorption which leaves only about 0.4% of filtered sodium in the urine. Loop diuretics have this ability, are therefore synonymous with high ceiling diuretics. Loop diuretics, such as furosemide, inhibit the body's ability to reabsorb sodium at the ascending loop in the nephron, which leads to an excretion of water in the urine, whereas water follows sodium back into the extracellular fluid. Other examples of high ceiling loop diuretics include ethacrynic torasemide. Thiazide-type diuretics such as hydrochlorothiazide act on the distal convoluted tubule and inhibit the sodium-chloride symporter leading to a retention of water in the urine, as water follows penetrating solutes. Frequent urination is due to the increased loss of water that has not been retained from the body as a result of a concomitant relationship with sodium loss from the convoluted tubule.
The short-term anti-hypertensive action is based on the fact that thiazides decrease preload, decreasing blood pressure. On the other hand, the long-term effect is due to an unknown vasodilator effect that decreases blood pressure by decreasing resistance. Carbonic anhydrase inhibitors inhibit the enzyme carbonic anhydrase, found in the proximal convoluted tubule; this results in several effects including bicarbonate accumulation in the urine and decreased sodium absorption. Drugs in this class include methazolamide; these are diuretics. The term "potassium-sparing" refers to an effect rather than a location. Aldosterone adds sodium channels in the principal cells of the collecting duct and late distal tubule of the nephron. Spironolactone prevents aldosterone from entering the principal cells, preventing sodium reabsorption. Similar agents are potassium canreonate. Epithelial sodium channel blockers: amiloride and triamterene; the term "calcium-sparing diuretic" is sometimes used to identify agents that result in a low rate of excretion of calcium.
The reduced concentration of calcium in the urine can lead to an increased rate of calcium in serum. The sparing effect on calcium can be beneficial in unwanted in hypercalcemia; the thiazides and potassium-sparing diuretics are considered to be calcium-sparing diuretics. The thiazides cause a net decrease in calcium lost in urine; the potassium-sparing diuretics cause a net increase in calcium lost in urine, but the increase is much smaller than the increase associated with other diuretic classes. By contrast, loop diuretics promote a significant increase in calcium excretion; this can increase risk of reduced bone density. Osmotic diuretics are substances that increase osmolarity but have limited tubular epithelial cell permeability, they work by expanding extracellular fluid and plasma volume, therefore increasing blood flow to the kidney the peritubular capillaries. This thus impairs the concentration of urine in the loop of Henle. Furthermore, the limited tubular epithelial cell permeability increases osmolality and thus water retention in the filtrate.
It was believed that the primary mechanism of osmotic diuretics such as mannitol is that they are filtered in the glomerulus, but cannot be reabsorbed. Thus their presence leads to an increase in the osmolarity of the filtrate and to maintain osmotic balance, water is retained in the urine. Glucose, like mannitol, is a sugar that can behave as an osmotic diuretic. Unlike mannitol, glucose is found in the blood. However, in certain conditions, such as diabetes mellitus, the concentration of glucose in the blood exceeds the maximum reabsorption capacity of the kidney; when this happens, glucose remains in the filtrate, leading to the osmotic retention of water in the urine. Glucosuria causes a loss of hypotonic water and Na+, leading to a hypertonic state wit
Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. A few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, are present in most of its habitats. Bacteria inhabit soil, acidic hot springs, radioactive waste, the deep portions of Earth's crust. Bacteria live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, only about half of the bacterial phyla have species that can be grown in the laboratory; the study of bacteria is known as a branch of microbiology. There are 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants and animals. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere.
The nutrient cycle includes the decomposition of dead bodies. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Data reported by researchers in October 2012 and published in March 2013 suggested that bacteria thrive in the Mariana Trench, with a depth of up to 11 kilometres, is the deepest known part of the oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, "You can find microbes everywhere—they're adaptable to conditions, survive wherever they are."The famous notion that bacterial cells in the human body outnumber human cells by a factor of 10:1 has been debunked. There are 39 trillion bacterial cells in the human microbiota as personified by a "reference" 70 kg male 170 cm tall, whereas there are 30 trillion human cells in the body.
This means that although they do have the upper hand in actual numbers, it is only by 30%, not 900%. The largest number exist in the gut flora, a large number on the skin; the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial in the gut flora. However several species of bacteria are pathogenic and cause infectious diseases, including cholera, anthrax and bubonic plague; the most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year in sub-Saharan Africa. In developed countries, antibiotics are used to treat bacterial infections and are used in farming, making antibiotic resistance a growing problem. In industry, bacteria are important in sewage treatment and the breakdown of oil spills, the production of cheese and yogurt through fermentation, the recovery of gold, palladium and other metals in the mining sector, as well as in biotechnology, the manufacture of antibiotics and other chemicals.
Once regarded as plants constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and harbour membrane-bound organelles. Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two different groups of organisms that evolved from an ancient common ancestor; these evolutionary domains are called Archaea. The word bacteria is the plural of the New Latin bacterium, the latinisation of the Greek βακτήριον, the diminutive of βακτηρία, meaning "staff, cane", because the first ones to be discovered were rod-shaped; the ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, bacteria and archaea were the dominant forms of life. Although bacterial fossils exist, such as stromatolites, their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species.
However, gene sequences can be used to reconstruct the bacterial phylogeny, these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. The most recent common ancestor of bacteria and archaea was a hyperthermophile that lived about 2.5 billion–3.2 billion years ago. Bacteria were involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves related to the Archaea; this involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still found in all known Eukarya. Some eukaryotes that contained mitochondria engulfed cyanobacteria-like organisms, leading to the formation of chloroplasts in algae and plants; this is known as primary endosymbiosis. Bacteria display a wide diversity of sizes, called morphologies.
Bacterial cells are about one-tenth the size of eukaryotic cells
The pelvis is either the lower part of the trunk of the human body between the abdomen and the thighs or the skeleton embedded in it. The pelvic region of the trunk includes the bony pelvis, the pelvic cavity, the pelvic floor, below the pelvic cavity, the perineum, below the pelvic floor; the pelvic skeleton is formed in the area of the back, by the sacrum and the coccyx and anteriorly and to the left and right sides, by a pair of hip bones. The two hip bones connect the spine with the lower limbs, they are attached to the sacrum posteriorly, connected to each other anteriorly, joined with the two femurs at the hip joints. The gap enclosed by the bony pelvis, called the pelvic cavity, is the section of the body underneath the abdomen and consists of the reproductive organs and the rectum, while the pelvic floor at the base of the cavity assists in supporting the organs of the abdomen. In mammals, the bony pelvis has a gap in the middle larger in females than in males, their young pass through this gap.
The pelvic region of the trunk is the lower part of the trunk, between the thighs. It includes several structures: the bony pelvis, the pelvic cavity, the pelvic floor, the perineum; the bony pelvis is the part of the skeleton embedded in the pelvic region of the trunk. It is subdivided into the pelvic spine; the pelvic girdle is composed of the appendicular hip bones oriented in a ring, connects the pelvic region of the spine to the lower limbs. The pelvic spine consists of the coccyx; the pelvic cavity defined as a small part of the space enclosed by the bony pelvis, delimited by the pelvic brim above and the pelvic floor below. Each hip bone consists of 3 sections, ilium and pubis. During childhood, these sections are separate bones, joined by the triradiate cartilage. During puberty, they fuse together to form a single bone; the pelvic cavity is a body cavity, bounded by the bones of the pelvis and which contains reproductive organs and the rectum. A distinction is made between the lesser or true pelvis inferior to the terminal line, the greater or false pelvis above it.
The pelvic inlet or superior pelvic aperture, which leads into the lesser pelvis, is bordered by the promontory, the arcuate line of ilium, the iliopubic eminence, the pecten of the pubis, the upper part of the pubic symphysis. The pelvic outlet or inferior pelvic aperture is the region between the subpubic angle or pubic arch, the ischial tuberosities and the coccyx. Ligaments: obturator membrane, inguinal ligament Alternatively, the pelvis is divided into three planes: the inlet and outlet; the pelvic floor has two inherently conflicting functions: One is to close the pelvic and abdominal cavities and bear the load of the visceral organs. To achieve both these tasks, the pelvic floor is composed of several overlapping sheets of muscles and connective tissues; the pelvic diaphragm is composed of the coccygeus muscle. These arise between the symphysis and the ischial spine and converge on the coccyx and the anococcygeal ligament which spans between the tip of the coccyx and the anal hiatus; this leaves a slit for the urogenital openings.
Because of the width of the genital aperture, wider in females, a second closing mechanism is required. The urogenital diaphragm consists of the deep transverse perineal which arises from the inferior ischial and pubic rami and extends to the urogential hiatus; the urogenital diaphragm is reinforced posteriorly by the superficial transverse perineal. The external anal and urethral sphincters close the urethra; the former is surrounded by the bulbospongiosus which narrows the vaginal introitus in females and surrounds the corpus spongiosum in males. Ischiocavernosus clitoridis. Modern humans are to a large extent characterized by large brains; because the pelvis is vital to both locomotion and childbirth, natural selection has been confronted by two conflicting demands: a wide birth canal and locomotion efficiency, a conflict referred to as the "obstetrical dilemma". The female pelvis, or gynecoid pelvis, has evolved to its maximum width for childbirth—a wider pelvis would make women unable to walk.
In contrast, human male pelvises are not constrained by the need to give birth and therefore are more optimized for bipedal locomotion. The principal differences between male and female true and false pelvis include: The female pelvis is larger and broader than the male pelvis, taller and more compact; the female inlet is oval in shape, while the male sacral promontory projects further. The sides of the male pelvis converge from the inlet to the outlet, whereas the sides of the female pelvis are wider apart; the angle between