Basic sciences

1   Anatomy is the study of the physical structure of organisms.In contrast to macroscopic or gross anatomy,cytology and histology are concerned with microscopic structures.
2   Biochemistry is the study of the chemistry taking place in living organisms, especially the structure and function of their chemical components.
3   Biomechanics is the study of the structure and function of biological systems by means of the methods of Mechanics.
4   Biostatistics is the application of statistics to biological fields in the broadest sense. A knowledge of biostatistics is essential in the planning,evaluation,and interpretation of medical research.It is also fundamental to epidemiology and evidence-based medicine.
5   Biophysics is an interdisciplinary science that uses the methods of physics and physical chemistry to study biological systems.
6   Cytology is the microscopic study of individual cells.
7   Embryology is the study of the early development of organisms.
8   Endocrinology is the study of hormones and their effect throughout the body of animals.
9   Epidemiology is the study of the demographics of disease processes,and includes,but is not limited to,the study of epidemics.
10  Genetics is the study of genes,and their role in biological inheritance.
11  Histology is the study of the structures of biological tissues by light microscopy,electron microscopy and immunohistochemistry.
12  Immunology is the study of the immune system,which includes the innate and adaptive immune system in humans,for example.
13  Medical physics is the study of the applications of physics principles in medicine.
14  Microbiology is the study of microorganisms,including protozoa,bacteria,fungi,and viruses.
15  Molecular biology is the study of molecular underpinnings of the process of replication,transcription and translation of the genetic material.
16  Neuroscience includes those disciplines of science that are related to the study of the nervous system.A main focus of neuroscience is the biology and physiology of the human brain and spinal cord.Some related clinical specialties include neurology,neurosurgery and psychiatry.
17  Nutrition science (theoretical focus) and dietetics (practical focus) is the study of the relationship of food and drink to health and disease,especially in determining an optimal diet.Medical nutrition therapy is done by dietitians and is prescribed for diabetes,cardiovascular diseases,weight and eating disorders,allergies,malnutrition,and neoplastic diseases.
18  Pathology as a science is the study of disease—the causes,course,progression and resolution thereof.
19  Pharmacology is the study of drugs and their actions.
20  Photobiology is the study of the interactions between non-ionizing radiation and living organisms.
21  Physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms.

Specialties
                        Main article: Medical specialty
  In the broadest meaning of "medicine",there are many different specialties.In the UK,most specialities will have their own body or college (collectively known as the Royal Colleges,although currently not all use the term "Royal") which have their own entrance exam.The development of a speciality is often driven by new technology (such as the development of effective anaesthetics) or ways of working (e.g. emergency departments) which leads to the desire to form a unifying body of doctors and thence the prestige of administering their own exam.

  Within medical circles,specialities usually fit into one of two broad categories: "Medicine" and "Surgery." "Medicine" refers to the practice of non-operative medicine,and most subspecialties in this area require preliminary training in "Internal Medicine".In the UK this would traditionally have been evidenced by obtaining the MRCP (An exam allowing Membership of the Royal College of Physicians or the equivalent college in Scotland or Ireland)."Surgery" refers to the practice of operative medicine,and most subspecialties in this area require preliminary training in "General Surgery." (In the UK: Membership of the Royal College of Surgeons of England (MRCS).)There are some specialties of medicine that at the present time do not fit easily into either of these categories, such as radiology,pathology,or anesthesia.Most of these have branched from one or other of the two camps above - for example anaesthesia developed first as a faculty of the Royal College of Surgeons (for which MRCS/FRCS would have been requi  red) before becoming the Royal College of Anaesthetists and membership of the college is by sitting the FRCA (Fellowship of the Royal College of Anesthetists).

Surgery
                  Main article: Surgery
  Surgical specialties employ operative treatment.In addition,surgeons must decide when an operation is necessary,and also treat many non-surgical issues,particularly in the surgical intensive care unit (SICU),where a variety of critical issues arise.Surgeons must also manage pre-operative,post-operative,and potential surgical candidates on the hospital wards.Surgery has many sub-specialties,including general surgery,cardiovascular surgery, colorectal surgery,neurosurgery,maxillofacial surgery,orthopedic surgery,otolaryngology,plastic surgery,oncologic surgery,transplant surgery,trauma surgery, urology,vascular surgery,and pediatric surgery.In some centers,anesthesiology is part of the division of surgery (for historical and logistical reasons),although it is not a surgical discipline.Other medical specialties may employ surgical procedures,such as ophthalmology and dermatology,but are not considered surgical sub-specialties per se.

Surgical training in the U.S. requires a minimum of five years of residency after medical school.Sub-specialties of surgery often require seven or more years.In addition,fellowships can last an additional one to three years.Because post-residency fellowships can be competitive,many trainees devote two additional years to research.Thus in some cases surgical training will not finish until more than a decade after medical school.Furthermore,surgical training can be very difficult and time consuming.

'Medicine' as a specialty
                                      Main article: Internal Medicine
Internal medicine is the medical specialty concerned with the diagnosis,management and nonsurgical treatment of unusual or serious diseases,either of one particular organ system or of the body as a whole. According to some sources,an emphasis on internal structures is implied.In North America,specialists in internal medicine are commonly called "internists".Elsewhere,especially in Commonwealth nations, such specialists are often called physicians.These terms,internist or physician (in the narrow sense,common outside North America),generally exclude practitioners of gynecology and obstetrics,pathology,psychiatry,and especially surgery and its subspecialities.

Because their patients are often seriously ill or require complex investigations,internists do much of their work in hospitals.Formerly,many internists were not subspecialized; such general physicians would see any complex nonsurgical problem; this style of practice has become much less common.In modern urban practice, most internists are subspecialists: that is,they generally limit their medical practice to problems of one organ system or to one particular area of medical knowledge. For example,gastroenterologists and nephrologists specialize respectively in diseases of the gut and the kidneys.

In Commonwealth and some other countries,specialist pediatricians and geriatricians are also described as specialist physicians (or internists) who have subspecialized by age of patient rather than by organ system.Elsewhere,especially in North America,general pediatrics is often a form of Primary care.

There are many subspecialities (or subdisciplines) of internal medicine:

1  Cardiology
2  Critical care medicine
3  Endocrinology
4  Gastroenterology
5  Geriatrics
6  Haematology
7  Hepatology
8  Infectious diseases
9  Nephrology
10 Oncology
11 Pediatrics
12 Pulmonology/Pneumology/Respirology
13 Rheumatology
14 Sleep medicine

  Training in internal medicine (as opposed to surgical training),varies considerably across the world: see the articles on Medical education and Physician for more details.In North America,it requires at least three years of residency training after medical school,which can then be followed by a one to three year fellowship in the subspecialties listed above. In general,resident work hours in medicine are less than those in surgery,averaging about 60 hours per week in the USA.This difference does not apply in the UK where all doctors are now required by law to work less than 48 hours per week on average.

Diagnostic specialties

1  Clinical laboratory sciences are the clinical diagnostic services which apply laboratory techniques to diagnosis and management of patients. In the United States, these services are supervised by a pathologist. The personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. Subspecialties include Transfusion medicine, Cellular pathology, Clinical chemistry, Hematology, Clinical microbiology and Clinical immunology.
2  Pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. As a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence-based medicine. Many modern molecular tests such as flow cytometry, polymerase chain reaction (PCR), immunohistochemistry, cytogenetics, gene rearrangements studies and fluorescent in situ hybridization (FISH) fall within the territory of pathology.
3  Radiology is concerned with imaging of the human body, e.g. by x-rays, x-ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography.
4  Nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances (radiopharmaceuticals) to the body, which can then be imaged outside the body by a gamma camera or a PET scanner. Each radiopharmaceutical consists of two parts: a tracer which is specific for the function under study (e.g., neurotransmitter pathway, metabolic pathway, blood flow, or other), and a radionuclide (usually either a gamma-emitter, or a positron emitter). There is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the PET/CT scanner.
5  Clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. These kinds of tests can be divided into recordings of: (1) spontaneous or continuously running electrical activity, or (2) stimulus evoked responses. Subspecialties include Electroencephalography, Electromyography, Evoked potential, Nerve conduction study and Polysomnography. Sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional.
Other major specialties
 The followings are some major medical specialties that do not directly fit into any of the above mentioned groups.

1  Anesthesiology (also known as anaesthetics): concerned with the perioperative management of the surgical patient. The anesthesiologist's role during surgery is to prevent derangement in the vital organs' (i.e. brain, heart, kidneys) functions and postoperative pain. Outside of the operating room, the anesthesiology physician also served the same function in the labor & delivery ward, and some are specialized in critical medicine.
2  Dermatology is concerned with the skin and its diseases. In the UK, dermatology is a subspecialty of general medicine.
3  Emergency medicine is concerned with the diagnosis and treatment of acute or life-threatening conditions, including trauma, surgical, medical, pediatric, and psychiatric emergencies.
4  Family medicine, family practice, general practice or primary care is, in many countries, the first port-of-call for patients with non-emergency medical problems.
5  Obstetrics and gynecology (often abbreviated as OB/GYN (American English) or Obs & Gynae (British English)) are concerned respectively with childbirth and the female reproductive and associated organs. Reproductive medicine and fertility medicine are generally practiced by gynecological specialists.
6  Medical Genetics is concerned with the diagnosis and management of hereditary disorders.
7  Neurology is concerned with diseases of the nervous system. In the UK, neurology is a subspecialty of general medicine.
8  Ophthalmology exclusively concerned with the eye and ocular adnexa, combining conservative and surgical therapy.
9  Pediatrics (AE) or paediatrics (BE) is devoted to the care of infants, children, and adolescents. Like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery.
10 Physical medicine and rehabilitation (or physiatry) is concerned with functional improvement after injury, illness, or congenital disorders.
11 Psychiatry is the branch of medicine concerned with the bio-psycho-social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. Related non-medical fields include psychotherapy and clinical psychology.
12 Preventive medicine is the branch of medicine concerned with preventing disease.
12.1 Community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis.
12.2 Occupational medicine's principal role is the provision of health advice to organizations and individuals to ensure that the highest standards of health and safety at work can be achieved and maintained.
12.3 Aerospace medicine deals with medical problems related to flying and space travel
Interdisciplinary fields
                              Some interdisciplinary sub-specialties of    


Medicine include:

1  Addiction medicine deals with the treatment of addiction.
2  Medical ethics deals with ethical and moral principles that apply values and judgments to the practice of medicine.
3  Bio medical Engineering is a field dealing with the application of engineering principles to medical practice.
4  Clinical pharmacology is concerned with how systems of therapeutics interact with patients.
5  Conservation medicine studies the relationship between human and animal health, and environmental conditions. Also known as ecological medicine, environmental medicine, or medical geology.
6  Disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation and management.
7  Diving medicine (or hyperbaric medicine) is the prevention and treatment of diving-related problems.
8  Evolutionary medicine is a perspective on medicine derived through applying evolutionary theory.
9  Forensic medicine deals with medical questions in legal context, such as determination of the time and cause of death.
10 Gender-based medicine studies the biological and physiological differences between the human sexes and how that affects differences in disease.
11 Hospice and Palliative Medicine is a relatively modern branch of clinical medicine that deals with pain and symptom relief and emotional support in patients with terminal illnesses including cancer and heart failure.
12 Hospital medicine is the general medical care of hospitalized patients. Physicians whose primary professional focus is hospital medicine are called hospitalists in the USA.
13 Laser medicine involves the use of lasers in the diagnostics and/or treatment of various conditions.
14 Medical humanities includes the humanities (literature, philosophy, ethics, history and religion), social science (anthropology, cultural studies, psychology, sociology), and the arts (literature, theater, film, and visual arts) and their application to medical education and practice.
15 Medical informatics, medical computer science, medical information and eHealth are relatively recent fields that deal with the application of computers and information technology to medicine.
16 Nosology is the classification of diseases for various purposes.
17 Nosokinetics is the science/subject of measuring and modelling the process of care in health and social care systems.
18 Pain management (also called pain medicine, or algiatry) is the medical discipline concerned with the relief of pain.
19 Pharmacogenomics is a form of individualized medicine.
20 Sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality.
21 Sports medicine deals with the treatment and preventive care of athletes, amateur and professional. The team includes specialty physicians and surgeons, athletic trainers, physical therapists, coaches, other personnel, and, of course, the athlete.
22 Therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health [1].
23 Travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments.
24 Urgent care focuses on delivery of unscheduled, walk-in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department. In some jurisdictions this function is combined with the emergency room.
25 Veterinary medicine; veterinarians apply similar techniques as physicians to the care of animals.
26 Wilderness medicine entails the practice of medicine in the wild, where conventional medical facilities may not be available.
27 Many other health science fields, e.g. dietetics