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Friday, March 13, 2020

Obstetrics

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Obstetrics

Obstetrics is the field of study concentrated on pregnancy, childbirth, and the postpartum period. As a medical specialty, obstetrics is combined with gynaecology under the discipline known as obstetrics and gynecology (OB/GYN), which is a surgical field.

Main areas

Prenatal care

Prenatal care is important in screening for various complications of pregnancy. This includes routine office visits with physical exams and routine lab tests:

First trimester

Genetic screening for Down syndrome (trisomy 21) and trisomy 18, the national standard in the United States, is rapidly evolving away from the AFP-Quad screen for Down syndrome, done typically in the second trimester at 16–18 weeks. The newer integrated screen (formerly called F.A.S.T.E.R for First And Second Trimester Early Results) can be done at 10 plus weeks to 13 plus weeks with an ultrasound of the fetal neck (thicker nuchal skin correlates with higher risk of Down syndrome being present) and two chemicals (analytes) PAPP-A and βHCG (pregnancy hormone level itself). It gives an accurate risk profile very 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.

Second trimester

  • MSAFP/quad. screen (four simultaneous blood tests) (maternal serum AFP, inhibin A, estriol, & βHCG) – 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, fluid and baby
  • Amniocentesis is the national standard (in what country) for women over 35 or who reach 35 by mid pregnancy or who are at increased risk by family history or prior birth history.

Third trimester

  • Hematocrit (if low, the mother receives iron supplements)
  • 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 (GLT) – screens for gestational diabetes; if > 140 mg/dL, a glucose tolerance test (GTT) is administered; a fasting glucose > 105 mg/dL suggests 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 (plus or minus 5 minutes). The standard modified criteria have been lowered to 135 since the late 1980s. 

The result of an Ultrasonography: a black and white image that shows a clear view of the interior abdomen.

Fetal assessments

A dating scan at 12 weeks.
 
Obstetric ultrasonography is routinely 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 significantly influenced by other factors. Ultrasound is also used for detecting congenital anomalies (or other foetal anomalies) and determining the biophysical profiles (BPP), which are generally easier to detect in the second trimester when the foetal structures are larger and more developed. Specialised ultrasound equipment can also 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 (CT) are not used, especially in the first trimester, due to the ionizing radiation, which has teratogenic effects on the foetus. No effects of magnetic resonance imaging (MRI) 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, and 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, and fetal pole. The gestational age can be assessed by evaluating the mean gestational sac diameter (MGD) before week 6, and 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:

Intercurrent diseases

A pregnant woman may have intercurrent diseases, that is, other diseases or conditions (not directly caused by the pregnancy) that may become worse or be a potential risk to the pregnancy.

Induction and labour

Induction is a method of artificially or prematurely stimulating labour in a woman. Reasons to induce can include pre-eclampsia, foetal distress, placental malfunction, intrauterine growth retardation and failure to progress through labour increasing the risk of infection and foetal distresses.

Induction may be achieved via several methods:
  • Disturbance of cervical memebranes
  • Pessary of Prostin cream, prostaglandin E2
  • Intravaginal or oral administration of misoprostol
  • Cervical insertion of a 30-mL Foley catheter
  • Rupturing the amniotic membranes
  • Intravenous infusion of synthetic oxytocin (Pitocin or Syntocinon)
During labour, the obstetrician carries out the following tasks:

Complications and emergencies

The main emergencies include:
  • Ectopic pregnancy is when an embryo implants in the uterine (Fallopian) tube or (rarely) on the ovary or inside the peritoneal cavity. This may cause massive internal bleeding.
  • Pre-eclampsia is a disease defined by a combination of signs and symptoms that are related to maternal hypertension. The cause is unknown, and markers are being sought to predict its development from the earliest stages of pregnancy. Some unknown factors cause vascular damage in the endothelium, causing hypertension. If severe, it progresses to eclampsia, where seizures occur, which can be fatal. Preeclamptic patients with the HELLP syndrome show liver failure and Disseminated intravascular coagulation (DIC). The only treatment is to deliver the foetus. Women may still develop pre-eclampsia following delivery.
  • Placental abruption is where the placenta detaches from the uterus and the woman and foetus can bleed to death if not managed appropriately.
  • Foetal distress where the foetus is getting compromised in the uterine environment.
  • Shoulder dystocia where one of the foetus' shoulders becomes stuck during vaginal birth. There are many risk factors, including macrosmic (large) foetus, but many are also unexplained.
  • Uterine rupture can occur during obstructed labour and endanger foetal and maternal life.
  • Prolapsed cord can only happen after the membranes have ruptured. The umbilical cord delivers before the presenting part of the foetus. If the foetus is not delivered within minutes, or the pressure taken off the cord, the foetus dies.
  • Obstetrical hemorrhage may be due to a number of factors such as placenta previa, uterine rupture or tears, uterine atony, retained placenta or placental fragments, or bleeding disorders.
  • Puerperal sepsis is an ascending infection of the genital tract. It may happen during or after labour. Signs to look out for include signs of infection (pyrexia or hypothermia, raised heart rate and respiratory rate, reduced blood pressure), and abdominal pain, offensive lochia (blood loss) increased lochia, clots, diarrhea and vomiting.

Postnatal care

Postnatal care is care provided to the mother following parturition.

A woman in the Western world who is delivering in a hospital may leave the hospital as soon as she is medically stable and chooses to leave, which can be as early as a few hours postpartum, though the average for spontaneous vaginal delivery (SVD) is 1–2 days, and the average caesarean section postnatal stay is 3–4 days.

During this time the mother is monitored for bleeding, bowel and bladder function, and baby care. The infant's health is also monitored.

Certain things must be kept in mind as the physician proceeds with the post-natal care.
  1. General condition of the patient.
  2. Check for vital signs (pulse, blood pressure, temperature, respiratory rate, (pain) at times)
  3. Palour?
  4. Oedema?
  5. Dehydration?
  6. Fundus (height following parturition, and the feel of the fundus) (Per abdominal examination)
  7. If an episiotomy or a C-section was performed, check for the dressing. Intact, pus, oozing, haematomas?
  8. Lochia (colour, amount, odour)?
  9. Bladder (keep the patient catheterized for 12 hours following local anaesthesia and 24–48 hours after general anaesthesia) ? (check for bladder function)
  10. Bowel movements?
  11. More bowel movements?
  12. Follow up with the neonate to check if they are healthy.

Veterinary obstetrics

History

Two midwives assisting a woman in labour on a birthing chair in the 16th century, from a work by Eucharius Rößlin.

Prior to the 18th century, caring for pregnant women in Europe was confined exclusively to women, and rigorously excluded men. The expectant mother would invite close female friends and family members to her home to keep her company during childbirth. Skilled midwives managed all aspects of the labour and delivery. The presence of physicians and surgeons was very rare and only occurred if a serious complication had taken place and the midwife had exhausted all measures at her disposal. Calling a surgeon was very much a last resort and having men deliver women in this era was seen as offending female modesty.

Before the 18th century

Prior to the 18th and 19th centuries, midwifery was well established but obstetrics was not recognized as a specific medical specialty. However, the subject matter and interest in the female reproductive system and sexual practice can be traced back to Ancient Egypt and Ancient Greece. Soranus of Ephesus sometimes is called the most important figure in ancient gynecology. Living in the late first century A.D. and early second century, he studied anatomy and had opinions and techniques on abortion, contraception –most notably coitus interruptus– and birth complications. After his death, techniques and works of gynecology declined; very little of his works were recorded and survived to the late 18th century when gynecology and obstetrics reemerged as a medical specialism.

18th century

The 18th century marked the beginning of many advances in European midwifery, based on better knowledge of the physiology of pregnancy and labour. By the end of the century, medical professionals began to understand the anatomy of the uterus and the physiological changes that take place during labour. The introduction of forceps in childbirth also took place at this time. All these medical advances in obstetrics were a lever for the introduction of men into an arena previously managed and run by women—midwifery.

The addition of the male-midwife (or man-midwife) is historically a significant change to the profession of obstetrics. In the 18th century medical men began to train in area of childbirth and believed with their advanced knowledge in anatomy that childbirth could be improved. In France these male-midwives were referred to as accoucheurs, a title later used all over Europe. The founding of lying-in hospitals also contributed to the medicalization and male-dominance of obstetrics. These early maternity hospitals were establishments where women would come to have their babies delivered, as opposed to the practice since time immemorial of the midwife attending the home of the woman in labour. This institution provided male-midwives with endless patients to practice their techniques on and was a way for these men to demonstrate their knowledge.

Many midwives of the time bitterly opposed the involvement of men in childbirth. Some male practitioners also opposed the involvement of medical men like themselves in midwifery and even went as far as to say that male-midwives only undertook midwifery solely for perverse erotic satisfaction. The accoucheurs argued that their involvement in midwifery was to improve the process of childbirth. These men also believed that obstetrics would forge ahead and continue to strengthen.

19th century

18th century physicians expected that obstetrics would continue to grow, but the opposite happened. Obstetrics entered a stage of stagnation in the 19th century, which lasted until about the 1880s. The central explanation for the lack of advancement during this time was the rejection of obstetrics by the medical community. The 19th century marked an era of medical reform in Europe and increased regulation over the profession. Major European institutions such as The College of Physicians and Surgeons considered delivering babies ungentlemanly work and refused to have anything to do with childbirth as a whole. Even when Medical Act 1858 was introduced, which stated that medical students could qualify as doctors, midwifery was entirely ignored. This made it nearly impossible to pursue an education in midwifery and also have the recognition of being a doctor or surgeon. Obstetrics was pushed to the side.

By the late 19th century, the foundation of modern-day obstetrics and midwifery began developing. Delivery of babies by doctors became popular and readily accepted, but midwives continued to play a role in childbirth. Midwifery also changed during this era due to increased regulation and the eventual need for midwives to become certified. Many European countries by the late 19th century were monitoring the training of midwives and issued certification based on competency. Midwives were no longer uneducated in the formal sense.

As midwifery began to develop, so did the profession of obstetrics near the end of the century. Childbirth was no longer unjustifiably despised by the medical community as it once had been at the beginning of the century. But obstetrics was underdeveloped compared to other medical specialites. Many male physicians would deliver children but very few would have referred to themselves as obstetricians. The end of the 19th century did mark a significant accomplishment in the profession with the advancements in asepsis and anaesthesia, which paved the way for the mainstream introduction and later success of the Caesarean Section.

Before the 1880s mortality rates in lying-hospitals would reach unacceptably high levels and became an area of public concern. Much of these maternal deaths were due to puerperal fever, then known as childbed fever. In the 1800s Dr. Ignaz Semmelweis noticed that women giving birth at home had a much lower incidence of childbed fever than those giving birth by physicians in lying-hospitals. His investigation discovered that washing hands with an antiseptic solution before a delivery reduced childbed fever fatalities by 90%. So it was concluded that it was physicians who had been spreading disease from one labouring mother to the next. Despite the publication of this information, doctors still would not wash. It was not until the 20th century when advancements in aseptic technique and the understanding of disease would play a significant role in the decrease of maternal mortality rates among many populations.

History of obstetrics in America

The development of obstetrics as a practice for accredited doctors happened at the turn of the 18th century and thus was very differently developed in Europe and in the Americas due to the independence of many countries in the Americas from European powers. “Unlike in Europe and the British Isles, where midwifery laws were national, in America, midwifery laws were local and varied widely”.

Gynaecology and Obstetrics gained attention in the American medical field at the end of the nineteenth century through the development of such procedures as the ovariotomy. These procedures then were shared with European surgeons who replicated the surgeries. This was a period when antiseptic, aseptic or anaesthetic measures were just being introduced to surgical and observational procedures and without these procedures surgeries were dangerous and often fatal. Following are two surgeons noted for their contributions to these fields include Ephraim McDowell and James Marion Sims. 

Ephraim McDowell developed a surgical practice in 1795 and performed the first ovariotomy in 1809 on a 47-year-old widow who then lived on for thirty-one more years. He had attempted to share this with John Bell whom he had practiced under who had retired to Italy. Bell was said to have died without seeing the document but it was published by an associate in Extractions of Diseased Ovaria in 1825. By the mid-century the surgery was both successfully and unsuccessfully being performed. Pennsylvanian surgeons the Attlee brothers made this procedure very routine for a total of 465 surgeries–John Attlee performed 64 successfully of 78 while his brother William reported 387– between the years of 1843 and 1883. By the middle of the nineteenth century this procedure was successfully performed in Europe by English surgeons Sir Spencer Wells and Charles Clay as well as French surgeons Eugène Koeberlé, Auguste Nélaton and Jules Péan.

J. Marion Sims was the surgeon responsible for being the first treating a vesicovaginal fistula – a condition linked to many caused mainly by prolonged pressing of the feotus against the pelvis or other causes such as rape, hysterectomy, or other operations– and also having been doctor to many European royals and the 20th President of the United States James A. Garfield after he had been shot. Sims does have a controversial medical past. Under the beliefs at the time about pain and the prejudice towards African people, he had practiced his surgical skills and developed skills on slaves. These women were the first patients of modern gynecology. One of the women he operated on was named Anarcha Westcott, the woman he first treated for a fistula.

Historical role of gender

Women and men inhabited very different roles in natal care up to the 18th century. The role of a physician was exclusively held by men who went to university, an overly male institution, who would theorize anatomy and the process of reproduction based on theological teaching and philosophy. Many beliefs about the female body and menstruation in the 17th and 18th centuries were inaccurate; clearly resulting from the lack of literature about the practice. Many of the theories of what caused menstruation prevailed from Hippocratic philosophy. Midwives of this time were those assisted in the birth and care of both born and unborn children, and as the name suggests, this position was held mainly by women.

During the birth of a child, men were rarely present. Women from the neighbourhood or family would join in on the process of birth and assist in many different ways. The one position where men would help with the birth of a child would be in the sitting position, usually when performed on the side of a bed to support the mother.

Men were introduced into the field of obstetrics in the nineteenth century and resulted in a change of the focus of this profession. Gynaecology directly resulted as a new and separate field of study from obstetrics and focused on the curing of illness and indispositions of female sexual organs. This had some relevance to some conditions as menopause, uterine and cervical problems, and childbirth could leave the mother in need of extensive surgery to repair tissue. But, there was also a large blame of the uterus for completely unrelated conditions. This led to many social consequences of the nineteenth century.
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Natural science

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Natural_science

The natural sciences seek to understand how the world and universe around us works. There are five major branches (top left to bottom right): Chemistry, astronomy, Earth science, physics, and biology.
 
Natural science is a branch of science concerned with the description, prediction, and understanding of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer review and repeatability of findings are used to try to ensure the validity of scientific advances.

Natural science can be divided into two main branches: life science (or biological science) and physical science. Physical science is subdivided into branches, including physics, chemistry, astronomy and Earth science. These branches of natural science may be further divided into more specialized branches (also known as fields). As empirical sciences, natural sciences use tools from the formal sciences, such as mathematics and logic, converting information about nature into measurements which can be explained as clear statements of the "laws of nature".

Modern natural science succeeded more classical approaches to natural philosophy, usually traced to ancient Greece. Galileo, Descartes, Bacon, and Newton debated the benefits of using approaches which were more mathematical and more experimental in a methodical way. Still, philosophical perspectives, conjectures, and presuppositions, often overlooked, remain necessary in natural science. Systematic data collection, including discovery science, succeeded natural history, which emerged in the 16th century by describing and classifying plants, animals, minerals, and so on. Today, "natural history" suggests observational descriptions aimed at popular audiences.

Criteria

Philosophers of science have suggested a number of criteria, including Karl Popper's controversial falsifiability criterion, to help them differentiate scientific endeavors from non-scientific ones. Validity, accuracy, and quality control, such as peer review and repeatability of findings, are amongst the most respected criteria in the present-day global scientific community.

Branches of natural science

Biology

Onion (Allium) cells in different phases of the cell cycle. Growth in an 'organism' is carefully controlled by regulating the cell cycle.

This field encompasses a set of disciplines that examines phenomena related to living organisms. The scale of study can range from sub-component biophysics up to complex ecologies. Biology is concerned with the characteristics, classification and behaviors of organisms, as well as how species were formed and their interactions with each other and the environment.

The biological fields of botany, zoology, and medicine date back to early periods of civilization, while microbiology was introduced in the 17th century with the invention of the microscope. However, it was not until the 19th century that biology became a unified science. Once scientists discovered commonalities between all living things, it was decided they were best studied as a whole.
Some key developments in biology were the discovery of genetics; evolution through natural selection; the germ theory of disease and the application of the techniques of chemistry and physics at the level of the cell or organic molecule.

Modern biology is divided into subdisciplines by the type of organism and by the scale being studied. Molecular biology is the study of the fundamental chemistry of life, while cellular biology is the examination of the cell; the basic building block of all life. At a higher level, anatomy and physiology look at the internal structures, and their functions, of an organism, while ecology looks at how various organisms interrelate.

Chemistry

This structural formula for molecule caffeine shows a graphical representation of how the atoms are arranged.
 
Constituting the scientific study of matter at the atomic and molecular scale, chemistry deals primarily with collections of atoms, such as gases, molecules, crystals, and metals. The composition, statistical properties, transformations and reactions of these materials are studied. Chemistry also involves understanding the properties and interactions of individual atoms and molecules for use in larger-scale applications. 

Most chemical processes can be studied directly in a laboratory, using a series of (often well-tested) techniques for manipulating materials, as well as an understanding of the underlying processes. Chemistry is often called "the central science" because of its role in connecting the other natural sciences. 

Early experiments in chemistry had their roots in the system of Alchemy, a set of beliefs combining mysticism with physical experiments. The science of chemistry began to develop with the work of Robert Boyle, the discoverer of gas, and Antoine Lavoisier, who developed the theory of the Conservation of mass.

The discovery of the chemical elements and atomic theory began to systematize this science, and researchers developed a fundamental understanding of states of matter, ions, chemical bonds and chemical reactions. The success of this science led to a complementary chemical industry that now plays a significant role in the world economy.

Physics

The orbitals of the hydrogen atom are descriptions of the probability distributions of an electron bound to a proton. Their mathematical descriptions are standard problems in quantum mechanics, an important branch of physics.

Physics embodies the study of the fundamental constituents of the universe, the forces and interactions they exert on one another, and the results produced by these interactions. In general, physics is regarded as the fundamental science, because all other natural sciences use and obey the principles and laws set down by the field. Physics relies heavily on mathematics as the logical framework for formulation and quantification of principles.

The study of the principles of the universe has a long history and largely derives from direct observation and experimentation. The formulation of theories about the governing laws of the universe has been central to the study of physics from very early on, with philosophy gradually yielding to systematic, quantitative experimental testing and observation as the source of verification. Key historical developments in physics include Isaac Newton's theory of universal gravitation and classical mechanics, an understanding of electricity and its relation to magnetism, Einstein's theories of special and general relativity, the development of thermodynamics, and the quantum mechanical model of atomic and subatomic physics.

The field of physics is extremely broad, and can include such diverse studies as quantum mechanics and theoretical physics, applied physics and optics. Modern physics is becoming increasingly specialized, where researchers tend to focus on a particular area rather than being "universalists" like Isaac Newton, Albert Einstein and Lev Landau, who worked in multiple areas.

Astronomy

Unmanned and manned spacecraft missions have been used to image distant locations within the Solar System, such as this Apollo 11 view of Daedalus crater on the far side of the Moon.

This discipline is the science of celestial objects and phenomena that originate outside the Earth's atmosphere. It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe.

Astronomy includes the examination, study and modeling of stars, planets, comets, galaxies and the cosmos. Most of the information used by astronomers is gathered by remote observation, although some laboratory reproduction of celestial phenomena has been performed (such as the molecular chemistry of the interstellar medium).

While the origins of the study of celestial features and phenomena can be traced back to antiquity, the scientific methodology of this field began to develop in the middle of the 17th century. A key factor was Galileo's introduction of the telescope to examine the night sky in more detail.

The mathematical treatment of astronomy began with Newton's development of celestial mechanics and the laws of gravitation, although it was triggered by earlier work of astronomers such as Kepler. By the 19th century, astronomy had developed into a formal science, with the introduction of instruments such as the spectroscope and photography, along with much-improved telescopes and the creation of professional observatories.

Interdisciplinary studies

The distinctions between the natural science disciplines are not always sharp, and they share a number of cross-discipline fields. Physics plays a significant role in the other natural sciences, as represented by astrophysics, geophysics, chemical physics and biophysics. Likewise chemistry is represented by such fields as biochemistry, chemical biology, geochemistry and astrochemistry.

A particular example of a scientific discipline that draws upon multiple natural sciences is environmental science. This field studies the interactions of physical, chemical, geological, and biological components of the environment, with particular regard to the effect of human activities and the impact on biodiversity and sustainability. This science also draws upon expertise from other fields such as economics, law, and social sciences.

A comparable discipline is oceanography, as it draws upon a similar breadth of scientific disciplines. Oceanography is sub-categorized into more specialized cross-disciplines, such as physical oceanography and marine biology. As the marine ecosystem is very large and diverse, marine biology is further divided into many subfields, including specializations in particular species. 

There is also a subset of cross-disciplinary fields which, by the nature of the problems that they address, have strong currents that run counter to specialization. Put another way: In some fields of integrative application, specialists in more than one field are a key part of the most dialog. Such integrative fields, for example, include nanoscience, astrobiology, and complex system informatics.

Earth science

Earth science (also known as geoscience), is an all-embracing term for the sciences related to the planet Earth, including geology, geophysics, geochemistry, hydrology, meteorology, and oceanography.

Although mining and precious stones have been human interests throughout the history of civilization, the development of the related sciences of economic geology and mineralogy did not occur until the 18th century. The study of the earth, particularly palaeontology, blossomed in the 19th century. The growth of other disciplines, such as geophysics, in the 20th century, led to the development of the theory of plate tectonics in the 1960s, which has had a similar effect on the Earth sciences as the theory of evolution had on biology. Earth sciences today are closely linked to petroleum and mineral resources, climate research and to environmental assessment and remediation.

Atmospheric sciences

Though sometimes considered in conjunction with the earth sciences, due to the independent development of its concepts, techniques and practices and also the fact of it having a wide range of sub-disciplines under its wing, the atmospheric sciences is also considered a separate branch of natural science. This field studies the characteristics of different layers of the atmosphere from ground level to the edge of the time. The timescale of the study also varies from days to centuries. Sometimes the field also includes the study of climatic patterns on planets other than earth.

Oceanography

The serious study of oceans began in the early to mid-20th century. As a field of natural science, it is relatively young but stand-alone programs offer specializations in the subject. Though some controversies remain as to the categorization of the field under earth sciences, interdisciplinary sciences or as a separate field in its own right, most modern workers in the field agree that it has matured to a state that it has its own paradigms and practices. As such a big family of related studies spanning every aspect of the oceans is now classified under this field.

Materials science

The materials paradigm represented as a tetrahedron

Materials science is a relatively new, interdisciplinary field which deals with the study of matter and its properties; as well as the discovery and design of new materials. Originally developed through the field of metallurgy, the study of the properties of materials and solids has now expanded into all materials. The field covers the chemistry, physics and engineering applications of materials including metals, ceramics, artificial polymers, and many others. The core of the field deals with relating structure of material with it properties. 

It is at the forefront of research in science and engineering. It is an important part of forensic engineering (the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property) and failure analysis, the latter being the key to understanding, for example, the cause of various aviation accidents. Many of the most pressing scientific problems that are faced today are due to the limitations of the materials that are available and, as a result, breakthroughs in this field are likely to have a significant impact on the future of technology.

The basis of materials science involves studying the structure of materials, and relating them to their properties. Once a materials scientist knows about this structure-property correlation, they can then go on to study the relative performance of a material in a certain application. The major determinants of the structure of a material and thus of its properties are its constituent chemical elements and the way in which it has been processed into its final form. These characteristics, taken together and related through the laws of thermodynamics and kinetics, govern a material's microstructure, and thus its properties.

History

Some scholars trace the origins of natural science as far back as pre-literate human societies, where understanding the natural world was necessary for survival. People observed and built up knowledge about the behavior of animals and the usefulness of plants as food and medicine, which was passed down from generation to generation. These primitive understandings gave way to more formalized inquiry around 3500 to 3000 BC in the Mesopotamian and Ancient Egyptian cultures, which produced the first known written evidence of natural philosophy, the precursor of natural science. While the writings show an interest in astronomy, mathematics and other aspects of the physical world, the ultimate aim of inquiry about nature's workings was in all cases religious or mythological, not scientific.

A tradition of scientific inquiry also emerged in Ancient China, where Taoist alchemists and philosophers experimented with elixirs to extend life and cure ailments. They focused on the yin and yang, or contrasting elements in nature; the yin was associated with femininity and coldness, while yang was associated with masculinity and warmth. The five phases – fire, earth, metal, wood and water – described a cycle of transformations in nature. Water turned into wood, which turned into fire when it burned. The ashes left by fire were earth. Using these principles, Chinese philosophers and doctors explored human anatomy, characterizing organs as predominantly yin or yang and understood the relationship between the pulse, the heart and the flow of blood in the body centuries before it became accepted in the West.

Little evidence survives of how Ancient Indian cultures around the Indus River understood nature, but some of their perspectives may be reflected in the Vedas, a set of sacred Hindu texts. They reveal a conception of the universe as ever-expanding and constantly being recycled and reformed. Surgeons in the Ayurvedic tradition saw health and illness as a combination of three humors: wind, bile and phlegm. A healthy life was the result of a balance among these humors. In Ayurvedic thought, the body consisted of five elements: earth, water, fire, wind and empty space. Ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy.

Pre-Socratic philosophers in Ancient Greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 BC, although an element of magic and mythology remained. Natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. Thales of Miletus, an early philosopher who lived from 625 to 546 BC, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. In the 5th century BC, Leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. Pythagoras applied Greek innovations in mathematics to astronomy, and suggested that the earth was spherical.

Aristotelian natural philosophy (400 BC–1100 AD)

Aristotle's view of inheritance, as a model of the transmission of patterns of movement of the body fluids from parents to child, and of Aristotelian form from the father.

Later Socratic and Platonic thought focused on ethics, morals and art and did not attempt an investigation of the physical world; Plato criticized pre-Socratic thinkers as materialists and anti-religionists. Aristotle, however, a student of Plato who lived from 384 to 322 BC, paid closer attention to the natural world in his philosophy. In his History of Animals, he described the inner workings of 110 species, including the stingray, catfish and bee. He investigated chick embryos by breaking open eggs and observing them at various stages of development. Aristotle's works were influential through the 16th century, and he is considered to be the father of biology for his pioneering work in that science. He also presented philosophies about physics, nature and astronomy using inductive reasoning in his works Physics and Meteorology.

Plato (left) and Aristotle in a 1509 painting by Raphael. Plato rejected inquiry into natural philosophy as against religion, while his student, Aristotle, created a body of work on the natural world that influenced generations of scholars.

While Aristotle considered natural philosophy more seriously than his predecessors, he approached it as a theoretical branch of science. Still, inspired by his work, Ancient Roman philosophers of the early 1st century AD, including Lucretius, Seneca and Pliny the Elder, wrote treatises that dealt with the rules of the natural world in varying degrees of depth. Many Ancient Roman Neoplatonists of the 3rd to the 6th centuries also adapted Aristotle's teachings on the physical world to a philosophy that emphasized spiritualism. Early medieval philosophers including Macrobius, Calcidius and Martianus Capella also examined the physical world, largely from a cosmological and cosmographical perspective, putting forth theories on the arrangement of celestial bodies and the heavens, which were posited as being composed of aether.

Aristotle's works on natural philosophy continued to be translated and studied amid the rise of the Byzantine Empire and Abbasid Caliphate.

In the Byzantine Empire John Philoponus, an Alexandrian Aristotelian commentator and Christian theologian, was the first who questioned Aristotle's teaching of physics. Unlike Aristotle who based his physics on verbal argument, Philoponus instead relied on observation, and argued for observation rather than resorting into verbal argument. He introduced the theory of impetus. John Philoponus' criticism of Aristotelian principles of physics served as inspiration for Galileo Galilei during the Scientific Revolution.

A revival in mathematics and science took place during the time of the Abbasid Caliphate from the 9th century onward, when Muslim scholars expanded upon Greek and Indian natural philosophy. The words alcohol, algebra and zenith all have Arabic roots.

Medieval natural philosophy (1100–1600)

Aristotle's works and other Greek natural philosophy did not reach the West until about the middle of the 12th century, when works were translated from Greek and Arabic into Latin. The development of European civilization later in the Middle Ages brought with it further advances in natural philosophy. European inventions such as the horseshoe, horse collar and crop rotation allowed for rapid population growth, eventually giving way to urbanization and the foundation of schools connected to monasteries and cathedrals in modern-day France and England. Aided by the schools, an approach to Christian theology developed that sought to answer questions about nature and other subjects using logic. This approach, however, was seen by some detractors as heresy. By the 12th century, Western European scholars and philosophers came into contact with a body of knowledge of which they had previously been ignorant: a large corpus of works in Greek and Arabic that were preserved by Islamic scholars. Through translation into Latin, Western Europe was introduced to Aristotle and his natural philosophy. These works were taught at new universities in Paris and Oxford by the early 13th century, although the practice was frowned upon by the Catholic church. A 1210 decree from the Synod of Paris ordered that "no lectures are to be held in Paris either publicly or privately using Aristotle's books on natural philosophy or the commentaries, and we forbid all this under pain of excommunication."

In the late Middle Ages, Spanish philosopher Dominicus Gundissalinus translated a treatise by the earlier Persian scholar Al-Farabi called On the Sciences into Latin, calling the study of the mechanics of nature scientia naturalis, or natural science. Gundissalinus also proposed his own classification of the natural sciences in his 1150 work On the Division of Philosophy. This was the first detailed classification of the sciences based on Greek and Arab philosophy to reach Western Europe. Gundissalinus defined natural science as "the science considering only things unabstracted and with motion," as opposed to mathematics and sciences that rely on mathematics. Following Al-Farabi, he then separated the sciences into eight parts, including physics, cosmology, meteorology, minerals science and plant and animal science.

Later philosophers made their own classifications of the natural sciences. Robert Kilwardby wrote On the Order of the Sciences in the 13th century that classed medicine as a mechanical science, along with agriculture, hunting and theater while defining natural science as the science that deals with bodies in motion. Roger Bacon, an English friar and philosopher, wrote that natural science dealt with "a principle of motion and rest, as in the parts of the elements of fire, air, earth and water, and in all inanimate things made from them." These sciences also covered plants, animals and celestial bodies. Later in the 13th century, a Catholic priest and theologian Thomas Aquinas defined natural science as dealing with "mobile beings" and "things which depend on a matter not only for their existence but also for their definition." There was wide agreement among scholars in medieval times that natural science was about bodies in motion, although there was division about the inclusion of fields including medicine, music and perspective. Philosophers pondered questions including the existence of a vacuum, whether motion could produce heat, the colors of rainbows, the motion of the earth, whether elemental chemicals exist and wherein the atmosphere rain is formed.

In the centuries up through the end of the Middle Ages, natural science was often mingled with philosophies about magic and the occult. Natural philosophy appeared in a wide range of forms, from treatises to encyclopedias to commentaries on Aristotle. The interaction between natural philosophy and Christianity was complex during this period; some early theologians, including Tatian and Eusebius, considered natural philosophy an outcropping of pagan Greek science and were suspicious of it. Although some later Christian philosophers, including Aquinas, came to see natural science as a means of interpreting scripture, this suspicion persisted until the 12th and 13th centuries. The Condemnation of 1277, which forbade setting philosophy on a level equal with theology and the debate of religious constructs in a scientific context, showed the persistence with which Catholic leaders resisted the development of natural philosophy even from a theological perspective. Aquinas and Albertus Magnus, another Catholic theologian of the era, sought to distance theology from science in their works. "I don't see what one's interpretation of Aristotle has to do with the teaching of the faith," he wrote in 1271.

Newton and the scientific revolution (1600–1800)

By the 16th and 17th centuries, natural philosophy underwent an evolution beyond commentary on Aristotle as more early Greek philosophy was uncovered and translated. The invention of the printing press in the 15th century, the invention of the microscope and telescope, and the Protestant Reformation fundamentally altered the social context in which scientific inquiry evolved in the West. Christopher Columbus's discovery of a new world changed perceptions about the physical makeup of the world, while observations by Copernicus, Tyco Brahe and Galileo brought a more accurate picture of the solar system as heliocentric and proved many of Aristotle's theories about the heavenly bodies false. A number of 17th-century philosophers, including Thomas Hobbes, John Locke and Francis Bacon made a break from the past by rejecting Aristotle and his medieval followers outright, calling their approach to natural philosophy as superficial.

The titles of Galileo's work Two New Sciences and Johannes Kepler's New Astronomy underscored the atmosphere of change that took hold in the 17th century as Aristotle was dismissed in favor of novel methods of inquiry into the natural world. Bacon was instrumental in popularizing this change; he argued that people should use the arts and sciences to gain dominion over nature. To achieve this, he wrote that "human life [must] be endowed with new discoveries and powers." He defined natural philosophy as "the knowledge of Causes and secret motions of things; and enlarging the bounds of Human Empire, to the effecting of all things possible." Bacon proposed scientific inquiry supported by the state and fed by the collaborative research of scientists, a vision that was unprecedented in its scope, ambition and form at the time. Natural philosophers came to view nature increasingly as a mechanism that could be taken apart and understood, much like a complex clock. Natural philosophers including Isaac Newton, Evangelista Torricelli and Francesco Redi conducted experiments focusing on the flow of water, measuring atmospheric pressure using a barometer and disproving spontaneous generation. Scientific societies and scientific journals emerged and were spread widely through the printing press, touching off the scientific revolution. Newton in 1687 published his The Mathematical Principles of Natural Philosophy, or Principia Mathematica, which set the groundwork for physical laws that remained current until the 19th century.

Some modern scholars, including Andrew Cunningham, Perry Williams and Floris Cohen, argue that natural philosophy is not properly called a science, and that genuine scientific inquiry began only with the scientific revolution. According to Cohen, "the emancipation of science from an overarching entity called 'natural philosophy' is one defining characteristic of the Scientific Revolution." Other historians of science, including Edward Grant, contend that the scientific revolution that blossomed in the 17th, 18th and 19th centuries occurred when principles learned in the exact sciences of optics, mechanics and astronomy began to be applied to questions raised by natural philosophy. Grant argues that Newton attempted to expose the mathematical basis of nature – the immutable rules it obeyed – and in doing so joined natural philosophy and mathematics for the first time, producing an early work of modern physics.

Isaac Newton is widely regarded as one of the most influential scientists of all time.

The scientific revolution, which began to take hold in the 17th century, represented a sharp break from Aristotelian modes of inquiry. One of its principal advances was the use of the scientific method to investigate nature. Data was collected and repeatable measurements made in experiments. Scientists then formed hypotheses to explain the results of these experiments. The hypothesis was then tested using the principle of falsifiability to prove or disprove its accuracy. The natural sciences continued to be called natural philosophy, but the adoption of the scientific method took science beyond the realm of philosophical conjecture and introduced a more structured way of examining nature.

Newton, an English mathematician, and physicist, was the seminal figure in the scientific revolution. Drawing on advances made in astronomy by Copernicus, Brahe, and Kepler, Newton derived the universal law of gravitation and laws of motion. These laws applied both on earth and in outer space, uniting two spheres of the physical world previously thought to function independently of each other, according to separate physical rules. Newton, for example, showed that the tides were caused by the gravitational pull of the moon. Another of Newton's advances was to make mathematics a powerful explanatory tool for natural phenomena. While natural philosophers had long used mathematics as a means of measurement and analysis, its principles were not used as a means of understanding cause and effect in nature until Newton.

In the 18th century and 19th century, scientists including Charles-Augustin de Coulomb, Alessandro Volta, and Michael Faraday built upon Newtonian mechanics by exploring electromagnetism, or the interplay of forces with positive and negative charges on electrically charged particles. Faraday proposed that forces in nature operated in "fields" that filled space. The idea of fields contrasted with the Newtonian construct of gravitation as simply "action at a distance", or the attraction of objects with nothing in the space between them to intervene. James Clerk Maxwell in the 19th century unified these discoveries in a coherent theory of electrodynamics. Using mathematical equations and experimentation, Maxwell discovered that space was filled with charged particles that could act upon themselves and each other and that they were a medium for the transmission of charged waves.

Significant advances in chemistry also took place during the scientific revolution. Antoine Lavoisier, a French chemist, refuted the phlogiston theory, which posited that things burned by releasing "phlogiston" into the air. Joseph Priestley had discovered oxygen in the 18th century, but Lavoisier discovered that combustion was the result of oxidation. He also constructed a table of 33 elements and invented modern chemical nomenclature. Formal biological science remained in its infancy in the 18th century, when the focus lay upon the classification and categorization of natural life. This growth in natural history was led by Carl Linnaeus, whose 1735 taxonomy of the natural world is still in use. Linnaeus in the 1750s introduced scientific names for all his species.

19th-century developments (1800–1900)

The Michelson–Morley experiment was used to disprove that light propagated through a luminiferous aether. This 19th-century concept was then superseded by Albert Einstein's special theory of relativity.

By the 19th century, the study of science had come into the purview of professionals and institutions. In so doing, it gradually acquired the more modern name of natural science. The term scientist was coined by William Whewell in an 1834 review of Mary Somerville's On the Connexion of the Sciences. But the word did not enter general use until nearly the end of the same century.

Modern natural science (1900–present)

According to a famous 1923 textbook Thermodynamics and the Free Energy of Chemical Substances by the American chemist Gilbert N. Lewis and the American physical chemist Merle Randall, the natural sciences contain three great branches:
Aside from the logical and mathematical sciences, there are three great branches of natural science which stand apart by reason of the variety of far reaching deductions drawn from a small number of primary postulates — they are mechanics, electrodynamics, and thermodynamics.
Today, natural sciences are more commonly divided into life sciences, such as botany and zoology; and physical sciences, which include physics, chemistry, astronomy, and Earth sciences.
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