List of human anatomical features

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Embryology is the study of the development of an embryo. An embryo is defined as any vertebrate in a stage before birth or hatching. Embryology is more specific as it only encompasses the modern definition: an animal that is undergoing early development including the formation of primitive organ systems, the creation of fundamental tissues, and cleavage; especially involving the development of human individuals from the moment the blastocyst is implanted until the end of the eight week after conception. Past the eight week, the developing animal is called a fetus.

After the 1950s, with the DNA helical structure being discovered by James D. Watson and Francis Crick, (in collaboration with Rosalind Franklin and Maurice Wilkins) and the increasing knowledge in the field of molecular biology, developmental biology emerged as the field of study that correlates the genes and such morphological changes; in other words, which genes are responsible for each morphological change that takes place in an embryo, and how these genes are regulated.

Many principles of embryology apply to both invertebrate animals as well as to vertebrates.^[1] Therefore, study of invertebrate embryology has advanced the study of vertebrate embryology. However, there are many differences as well. For example, numerous invertebrate species release a larva before development is complete; at the end of the larval period, an animal for the first time looks like an offspring of its parents. Although invertebrate embryology is similar in some ways for different invertebrate animals, there are also countless variations. For instance, some insects proceed directly from egg to adult form whereas others develop through an elaborate sequence of changes.

Neuroembryology refers to the development of an embryos nervous system. At the middle of the third week the neural plate appears which originates from the ectoderm.

• Ontogeny
• Embryogenesis
• Recapitulation theory
• Prenatal development

• UNSW Embryology Large resource of information and media
• [2] Definition of embryo according to Webster

• Scott F. Gilbert. Developmental Biology. Sinauer, 2003. ISBN 0-87893-258-5.
• Lewis Wolpert. Principles of Development. Oxford University Press, 2006. ISBN 0-19-927536-X.

• Embryo Research UK philosophy and ethics website discussing the ethics of embryology
• Human embryo research Canadian website covering the ethics of human embryo research
• University of Indiana’s Human Embryology Animations

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Template:WikiDoc Cardiology News Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Angiology (from Greek: ἀγγειο, angio, “vessel”; and λόγος, logos, “knowledge”) is the medical specialty which studies the diseases of circulatory system and of the lymphatic system, i.e., arteries, veins and lymphatic vases, and its diseases.

Arterial diseases include the aorta (aneurysms/dissection) and arteries supplying the legs hands, kidneys, brain, intestines. It also covers arterial thrombosis and embolism; vasculitides; and vasospastic disorders. Venous diseases include venous thrombosis, chronic venous insufficiency, and varicose veins. Lymphatic diseases include primary and secondary forms of lymphedema. It also involves modification of risk factors for vascular disease like high cholesterol, high blood pressure.

High blood pressure, high cholesterol, heart attack, stroke and venous blood clots all fall under the specialty of vascular medicine. Hence a vascular medicine specialist should be able to address most of the major diseases in our age in a comprehensive manner, using a unique perspective.

Currently there is a shortage of practitioners in this field, mainly due to lack of training programs and lack of awareness in patients and physicians of this as a distinct medical specialty. With an increasing burden of vascular diseases in our aging population, the establishment of a critical mass of physicians with interest in vascular diseases is paramount.

In 2005, the first vascular medicine boards were administered by the American Board of Vascular Medicine.

• Medical ultrasonography – Doppler sonography

• American Board of Vascular Medicine
• Society for Vascular Medicine and Biology
• National Heart, Lung, and Blood Institute

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Arteries are muscular blood vessels that carry blood away from the heart.^[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life. Its proper functioning is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, maintenance of optimum pH, and the mobility of the elements, proteins and cells of the immune system. In developed countries, the two leading causes of death, myocardial infarction and stroke each may directly result from an arterial system that has been slowly and progressively compromised by years of deterioration. (See atherosclerosis).

The arterial system is the higher-pressure portion of the circulatory system. Arterial pressure varies between the peak pressure during heart contraction, called the systolic pressure, and the minimum, or diastolic pressure between contractions, when the heart rests between cycles. This pressure variation within the artery produces the pulse which is observable in any artery, and reflects heart activity.

The outermost layer is known as the tunica externa formerly known as “tunica adventitia” and is composed of connective tissue. Inside this layer is the tunica media, or media, which is made up of smooth muscle cells and elastic tissue. The innermost layer, which is in direct contact with the flow of blood is the tunica intima, commonly called the intima. This layer is made up of mainly endothelial cells. The hollow internal cavity in which the blood flows is called the lumen.

There are several types of arteries in the body:

The pulmonary arteries carry deoxygenated blood that has just returned from the body to the lungs, where carbon dioxide is exchanged for oxygen.

Systemic arteries deliver blood to the arterioles, and then to the capillaries, where nutrients and gasses are exchanged.

The aorta is the root systemic artery. It receives blood directly from the left ventricle of the heart via the aortic valve. As the aorta branches, and these arteries branch in turn, they become successively smaller in diameter, down to the arteriole. The arterioles supply capillaries which in turn empty into venules.

Arterioles, the smallest of the true arteries, help regulate blood pressure and deliver blood to the kidneys (capillaries).

Arterioles have the greatest collective influence on both local blood flow and on overall blood pressure. They are the primary “adjustable nozzles” in the blood system, across which the greatest pressure drop occurs. The combination of heart output (cardiac output) and systemic vascular resistance, which refers to the collective resistance of all of the body’s arterioles, are the principal determinants of arterial blood pressure at any given moment.

The capillaries are where all of the important exchanges happen in the circulatory system. The capillaries are a single cell thick to aid fast and easy diffusion of gases, sugars and other nutrients to surrounding tissues.

To withstand and adapt to the pressures within, arteries are surrounded by varying thicknesses of smooth muscle which have extensive elastic and inelastic connective tissues.

The pulse pressure, i.e. Systolic vs. Diastolic difference, is determined primarily by the amount of blood ejected by each heart beat, stroke volume, versus the volume and elasticity of the major arteries.

Over time, elevated arterial blood sugar (see Diabetes Mellitus), lipoprotein cholesterol, and pressure, smoking, and other factors are all involved in damaging both the endothelium and walls of the arteries, resulting in atherosclerosis or Diabetes Mellitus.

Among the ancient Greeks, the arteries were considered to be “air holders” that were responsible for the transport of air to the tissues and were connected to the trachea. This theory presumably arose from the fact that the arteries are empty after death: the last beat of the heart pushes the blood through the capillaries and into the veins.

In medieval times, it was recognized that arteries carried a fluid, called “spiritual blood” or “vital spirits”, considered to be different from the contents of the veins. This theory went back to Galen. In the late medieval period, the trachea,^[2] and ligaments were also called “arteries”.^[3]

William Harvey described and popularized the modern concept of the circulatory system and the roles of arteries and veins in the 17th century.

Alexis Carrel at the beginning of 20th century first described the technique for vascular suturing and anastomosis and successfully performed many organ transplantations in animals; he thus actually opened the way to modern vascular surgery that was before limited to vessels permanent ligatation.

• Peripheral arteries
• Arterial tree
• Blood

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

In the circulatory system, a vein is a blood vessel that carries blood toward the heart. The majority of veins in the body carry low-oxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood.

Veins function to return deoxygenated blood to the heart, and are essentially tubes that collapse when their lumens are not filled with blood. The thick, outer-most layer of a vein is comprised of collagen, wrapped in bands of smooth muscle while the interior is lined with endothelial cells. Most veins have one-way flaps called venous valves that prevent blood from backflowing and pooling in the lower extremities due to the effects of gravity. The precise location of veins is much more variable from person to person than that of arteries.

The total capacity of the veins is more than sufficient to hold the entire blood volume of the body; this capacity is reduced through the venous tone of the smooth muscles, minimizing the cross-sectional area (and hence volume) of the individual veins and therefore total venous system. The helical bands of smooth muscles which wrap around veins help maintain blood flow to the right atrium. In cases of vasovagal syncope, the smooth muscles relax and the veins of the extremities below the heart fill up with blood, failing to return sufficient volume to maintain cardiac output and blood flow to the brain.

Veins serve to return blood from organs to the heart. In systemic circulation oxygenated blood is pumped by the left ventricle through the arteries to the muscles and organs of the body, where its nutrients and gases are exchanged at capillaries, entering the veins filled with cellular waste and carbon dioxide. The de-oxygenated blood is taken by veins to the right atrium of the heart, which transfers the blood to the right ventricle, where it is then pumped to the pulmonary arteries and eventually the lungs. In pulmonary circulation the pulmonary veins return oxygenated blood from the lungs to the left atrium, which empties into the left ventricle, completing the cycle of blood circulation.

The return of blood to the heart is assisted by the action of the skeletal-muscle pump which helps maintain the extremely low blood pressure of the venous system. Fainting can be caused by failure of the skeletal-muscular pump. Long periods of standing can result in blood pooling in the legs, with blood pressure too low to return blood to the heart. Neurogenic and hypovolaemic shock can also cause fainting. In these cases the smooth muscles surrounding the veins become slack and the veins fill with blood, absorbing a large portion of the total blood volume, keeping blood away from the brain and causing unconsciousness.

Often the generalization is made that arteries carry oxygenated blood to the tissues, the tissues consume the oxygen, and the remaining deoxygenated blood is carried back to the heart for reoxygenation. This is an oversimplification: all veins carry oxygenated blood,^[1] although the blood carried by the veins is usually considerably less oxygenated than the blood carried by most arteries.

Veins are used medically as points of access to the blood stream, permitting the withdrawal of blood specimens (venipuncture) for testing purposes, and enabling the infusion of fluid, electrolytes, nutrition, and medications. The latter is called intravenous delivery. It can be done by an injection with a syringe, or by inserting a catheter (a flexible tube). In contrast to arterial blood which is uniform throughout the body, the blood removed from veins for testing can vary in its contents depending on the part of the body the vein drains. In example, blood drained from a working muscle will contain significantly less oxygen and glucose than blood drained from the liver. However the more blood from different veins mixes as it returns to the heart, the more homogeneous it becomes.

If an intravenous catheter has to be inserted, for most purposes this is done into a peripheral vein (a vein near the surface of the skin in the hand or arm, or less desirably, the leg). Some highly concentrated fluids or irritating medications must flow into the large central veins, which are sometimes used when peripheral access cannot be obtained. Catheters can be threaded into the superior vena cava for these uses: if long term use is thought to be needed, a more permanent access point can be inserted surgically.

The most common vein disorder is venous insufficiency, usually manifested by spider veins or varicose veins. A variety of treatments are used depending on the patient’s particular type and pattern of veins and on the physician’s preferences. Treatment can include radio-frequency ablation, vein stripping, ambulatory phlebectomy, foam sclerotherapy, sclerotherapy, lasers or compression.

Deep vein thrombosis is a condition where a blood clot forms in a deep vein, which can lead to pulmonary embolism and chronic venous insufficiency.

Phlebology is the medical discipline that involves the diagnosis and treatment of disorders of venous origin. Diagnostic techniques used include the history and physical examination, venous imaging techniques and laboratory evaluation related to venous thromboembolism.

The American Medical Association has added Phlebology to their list of Self-Designated Practice Specialties.

The pulmonary veins carry relatively oxygenated blood from the lungs to the heart. The superior and inferior venae cavae carry relatively deoxygenated blood from the upper and lower systemic circulations, respectively.

A portal venous system is a series of veins or venules that directly connect two capillary beds. Examples of such systems include the hepatic portal vein and hypophyseal portal system.

The blood carried by veins is dark red due to its high percentage of CO₂ as it returns to the heart (in contrast to the high levels of O₂ in arterial blood, which is bright red). Veins appear blue because the subcutaneous fat in the skin absorbs lower-frequency light, permitting only the highly energetic blue wavelengths to penetrate through to the dark vein and reflect off. This physical effect can also be seen in the iris of blue eyes (pigmentless iris in the front, dark retina in the back) and is called Rayleigh scattering.

Veins can be classified into:

• portal vein vs. non-portal (most common)
• superficial veins vs. deep veins
• pulmonary veins vs. systemic veins

List of important named veins

• Jugular veins
• Pulmonary veins
• Portal vein
• Superior vena cava
• Inferior vena cava
• Iliac vein
• Femoral vein
• Popliteal vein
• Great saphenous vein
• Small saphenous vein

Names of important venule systems

• Portal venous system
• Systemic venous system

• Peripheral vein
• Deep vein
• Deep vein thrombosis
• Superficial vein
• Varicose veins
• Pulmonary circulation

• Merck Manual article on veins.
• American College of Phlebology

• Phlebology – international journal of venous diseases
• Phlebology: The Journal of Venous Disease

The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.

List of contributors:

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Neurology is a medical speciality dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue, such as muscle.^[1] Physicians who specialize in neurology are called neurologists, and are trained to investigate, or diagnose and treat, neurological disorders. Pediatric neurologists treat neurological disease in children. Neurologists may also be involved in clinical research, clinical trials, as well as basic research, and translational research. In the United Kingdom, contributions to the field of Neurology stem from various professions; saliently, several biomedical research scientists are choosing to specialise in the technical/laboratory aspects of one of neurology’s subdisciplines.

Neurological disorders are disorders that affect the central nervous system (brain and spinal cord), the peripheral nervous system, or the autonomic nervous system.

Major conditions include:

• Behavioral/cognitive syndromes
• Headache disorders such as migraine, cluster headache, and tension headache
• Seizure disorders
• Neurodegenerative disorders including

• Alzheimer’s disease
• Parkinson’s disease
• Huntington’s disease
• Amyotrophic lateral sclerosis (Lou Gehrig’s disease)

• Cerebrovascular disease such as

• Transient ischemic attack
• Stroke

• Sleep disorders
• Cerebral palsy
• Infections of the brain (encephalitis), brain meninges (meningitis), and spinal cord (myelitis)
• Infections of the peripheral nervous system
• Neoplasms – tumors of the brain and its meninges (brain tumors), spinal cord tumors, tumors of the peripheral nerves (neuroma)
• Movement disorders such as

• Parkinson’s disease
• Huntington’s disease
• Hemiballismus
• Tic disorder
• Gilles de la Tourette syndrome

• Demyelinating diseases of the

• Central nervous system such as multiple sclerosis
• Peripheral nervous system such as Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP)

• Spinal cord disorders – tumors, infections, trauma, and malformations (e.g., myelocele, meningomyelocele, tethered cord)
• Disorders of peripheral nerves, muscle (myopathy), and neuromuscular junctions
• Traumatic injuries to the brain, spinal cord, and peripheral nerves
• Altered mental status, encephalopathy, stupor, and coma
• Speech and language disorders

A neurologist’s educational background and medical training varies with the country of training. In the United States and Canada, neurologists are physicians who have completed postgraduate training in neurology after the completion of medical school and attainment of the allopathic (MD, MBBS, MBChB, etc) or osteopathic (DO) degree.

Neurologists complete a minimum of 10 years of post secondary education and clinical training. In the majority of cases this training includes obtaining an undergraduate degree (a few medical schools will admit students with as little as two years of undergraduate education), a medical degree (4 years), and then completing a four-year residency in neurology. The four-year residency consists of one year of internal medicine training followed by three years of training in neurology.

Many neurologists also have additional subspecialty training (fellowships) after completing their residency in one area of neurology such as stroke, epilepsy, neuromuscular, sleep medicine, pain management, neuroimmunology, clinical neurophysiology, or movement disorders.

During a neurological examination, the neurologist reviews the patient’s health history with special attention to the current condition. The patient then takes a neurological exam. Typically, the exam tests mental status, function of the cranial nerves (including vision), strength, coordination, reflexes, and sensation. This information helps the neurologist determine if the problem exists in the nervous system and the clinical localization. Localization of the pathology is the key process by which neurologists develop their differential diagnosis. Further tests may be needed to confirm a diagnosis and ultimately guide therapy and appropriate management.

Neurologists are responsible for the diagnosis, treatment, and management of all the above conditions. When surgical intervention is required, the neurologist may refer the patient to a neurosurgeon, an interventional neuroradiologist, or a neurointerventionalist. In some countries, additional legal responsibilities of a neurologist may include making a finding of brain death when it is suspected that a patient is deceased. Neurologists frequently care for people with hereditary (genetic) diseases when the major manifestations are neurological, as is frequently the case. Lumbar punctures are frequently performed by neurologists. Some neurologists may develop an interest in particular subfields, such as dementia, movement disorders, headaches, epilepsy, sleep disorders, chronic pain management, multiple sclerosis or neuromuscular diseases.

There is some overlap with other specialties, varying from country to country and even within a local geographic area. Acute head trauma is most often treated by neurosurgeons, whereas sequela of head trauma may be treated by neurologists or specialists in rehabilitation medicine. Although stroke cases have been traditionally managed by internal medicine or hospitalists, the emergence of vascular neurology and endovascular neurosurgery as disciplines have created a demand for stroke specialists. The establishment of JCAHO stroke centers have increased the role of neurologists in stroke care in many primary as well as tertiary hospitals. Some cases of nervous system infectious diseases are treated by infectious disease specialists. Most cases of headache are diagnosed and treated primarily by general practitioners, at least the less severe cases. Similarly, most cases of sciatica and other mechanical radiculopathies are treated by general practitioners, though they may be referred to neurologists or a surgeon (neurosurgeons or orthopedic surgeons). Sleep disorders are also treated by pulmonologists. Cerebral palsy is initially treated by pediatricians, but care may be transferred to an adult neurologist after the patient reaches a certain age.

Clinical neuropsychologists are often called upon to evaluate brain–behavior relationships for the purpose of assisting with differential diagnosis, planning rehabilitation strategies, documenting cognitive strengths and weaknesses, and measuring change over time (e.g., for identifying abnormal aging or tracking the progression of a dementia).

In some countries, e.g. USA and Germany, neurologists may specialize in clinical neurophysiology, the field responsible for EEG, nerve conduction studies, EMG, and evoked potentials. In other countries, this is an autonomous specialty (e.g. United Kingdom, Sweden).

Although many mental illnesses are believed to be neurological disorders affecting the central nervous system, traditionally they are classified separately, and treated by psychiatrists. In a 2002 review article in the American Journal of Psychiatry, Professor Joseph B. Martin, Dean of Harvard Medical School and a neurologist by training, wrote that ‘the separation of the two categories is arbitrary, often influenced by beliefs rather than proven scientific observations. And the fact that the brain and mind are one makes the separation artificial anyway.’ (Martin JB. The integration of neurology, psychiatry and neuroscience in the 21st century. Am J Psychiatry 2002; 159:695-704)

There are strong indications that neuro-chemical mechanisms play an important role in the development of, for instance, bipolar disorder and schizophrenia. As well, ‘neurological’ diseases often have ‘psychiatric’ manifestations, such as post-stroke depression, depression and dementia associated with Parkinson’s disease, mood and cognitive dysfunctions in Alzheimer’s disease, to name a few. Hence, there is no sharp distinction between neurology and psychiatry on a biological basis – this distinction has mainly practical reasons and strong historical roots. (such as the dominance of Freud‘s psychoanalytic theory in psychiatric thinking in the first three quarters of the 20th century – which has since then been largely replaced by the focus on neurosciences – aided by the tremendous advances in genetics and neuroimaging recently.)

• European Federation of Neurological Societies
• European Journal of Neurology
• National Institute of Neurological Disorders and Stroke (NINDS)
• Fast-MAG The Field Administration of Stroke Therapy – Magnesium Phase 3 Clinical Trial
• Journal of The American Stroke Association
• Therapeutic Guidelines – Neurology
• Revista de neurologia

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