Definition Heartburn is a burning feeling in the neck, throat, or upper chest caused by irritation of stomach acid that occurs after eating (acid indigestion). Heartburn may get worse when lying down. Description The esophagus (food pipe) connects the throat and stomach. A thick band of muscles called the lower esophageal sphincter (LES) is located between the lower part of the esophagus and the...

Definition Heart valve replacement is a surgical procedure during which surgeons remove a damaged valvefrom the heart and substitute a healthy one. Purpose Four valves direct blood to and from the body through the heart: the aortic valve, the pulmonicvalve, the tricuspid valve, and the mitral valve. Any of these valves may malfunction because of a birth defect,...

Definition Heart valve repair is a surgical procedure used to correct a malfunctioning heart valve.Repair usually involves separating the valve leaflets (the one-way "doors" of the heartvalve which open and close to pump blood through the heart) or forcing them open with a balloon...

Definition Heart transplantation, also called cardiac transplantation, is the replacement of a patient's diseased or injured heart with a healthy donor heart. Purpose Heart transplantation is performed on patients with end-stage heart failure or some other life-threatening heart disease. Before a doctor recommends heart transplantation for...

Definition Heart surgery for congenital defects consists of a variety of surgical procedures that are performed to repair the many types of heart defects that may be present at birth and can go undiagnosed into adulthood. Purpose Heart surgery for congenital defects is performed to repair a defect, providing improved blood flow to the pulmonary...

Definition A heart murmur is an abnormal, extra sound during the heartbeat cycle made by blood moving through the heart and its valves. It is detected by the physician's examination using a stethoscope. Description A heart which is beating normal makes two sounds, "lubb" when the valves between the atria and ventricles...

Definition Heart failure is a condition in which the heart has lost the ability to pump enough blood to the body's tissues. With too little blood being delivered, the organs and other tissues do not receive enough oxygen and nutrients to function properly. Description According to the American Heart Association, about 4.9 million Americans are living with congestiveheart failure....

Definition Heart block refers to a delay in the normal flow of electrical impulses that cause the heart to beat. They are further classified as first-, second-, or third-degree block. Description The muscles of the heart contract in a rhythmic order for each heart beat, because electrical impulses travel along a specific route called the conduction system. The main...

Definition A heart attack is the death of, or damage to, part of the heart muscle because the supply of blood to the heart muscle is severely reduced or stopped. Description Heart attack is the leading cause of death in the United States. More than 1.5 millionAmericans suffer a heart attack every year, and almost half a million die, according to...

Definition A tuning fork is a metal instrument with a handle and two prongs or tines. Tuning forks, made of steel, aluminum, or magnesium-alloy will vibrate at a set frequency to produce a musical tone when struck. The vibrations produced can be used to assess a person's ability to hear various sound frequencies. Purpose A vibrating tuning fork held next to the ear...

Definition Hearing loss is any degree of impairment of the ability to apprehend sound. Description Sound can be measured accurately. The term decibel (dB) is a measure of loudness and refers to a unit for expressing the relative intensity of sound on a scale from zero, for a nearly imperceptible sound, to 130, which is the level at which sound causes pain in...

Definition A hearing aid is a device that can amplify sound waves in order to help a deaf or hard-of-hearing person hear sounds more clearly. There are two major types of hearing loss , conductive hearing loss and sensory hearing loss. Conductive hearing loss is often mechanical in nature,...

Definition A headache involves pain in the head that can arise from many disorders or may be a disorder in and of itself. Description Headaches can be categorized as primary or secondary. Primary headaches occur independently and are not the result of another medical problem. Secondary headaches are caused by illness, infection, or injury and account for less than 10 percent of all headaches. There...

Definition Injury to the head may damage the scalp, skull or brain. The most important consequenceof head trauma is traumatic brain injury. Head injury may occur either as a closed headinjury, such as the head hitting a car's windshield, or as a penetrating head injury,...

Definition The group of cancers found in the head and neck region, excluding tumors of the eyes and brain. Description The tumors associated with head and neck cancers are found in several regions, including the lips, tongue, mouth, nasal passages, pharynx, larynx (voice box), salivary glands, thyroid gland, and parathyroid glands. Many head and neck cancers...

Definition Hatha yoga is the most widely practiced form of yoga in America. It is the branch of yoga that concentrates on physical health and mental well-being. Hatha yoga uses bodily postures (asanas ), breathing techniques (pranayama ), and meditation (dyana ) with the goal of bringing about a sound, healthy body and a clear, peaceful mind....

Definition Hartnup disease is an inherited nutritional disorder with primary symptoms including a red, scaly rash and sensitivity to sunlight. Description Hartnup disease was first identified in the 1950s in the Hartnup family in London. A defect in intestines and kidneys makes it difficult to break down and absorb protein in the diet. This causes a condition very similar to pellegra...

Definition This test is done to help evaluate a person for hemolytic anemia. Purpose Haptoglobin is a blood protein made by the liver. The haptoglobin levels decrease in hemolytic anemia. Hemolytic anemias include a variety of conditions that result in hemolyzed, or burst, red blood cells. Decreased values can also indicate a slower type of red cell destruction unrelated...

Hantavirus infections are the cause of two serious diseases, hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS). There are at least fourteen types of hantaviruses, which differ only slightly from one another, and scientists are working to identify and classify previously unrecognised hantaviruses. Well-known hantaviruses are are: Hantaan, Seoul, Puumala,...

Definition Hand-foot-and-mouth disease is an infection of young children in which characteristic fluid-filled blisters appear on the hands, feet, and inside the mouth. Description Coxsackie viruses belong to a family of viruses called enteroviruses. These viruses live in the gastrointestinal tract, and are therefore present in feces. They can be spread easily from one person to another when poor hygiene...

Definition Hammertoe is a condition in which the toe is bent in a claw-like position. It can be present in more than one toe but is most common in the second toe. Description Hammertoe is described as a deformity in which the toes bend downward with the toe joint usually enlarged. Over time, the joint enlarges and stiffens as it rubs against shoes. Other foot structures involved include the overlying...

Definitions A hallucination is a sensory perception without a source in the external world. The English word "hallucination" comes from the Latin verb hallucinari, which means "to wander in the mind."Hallucinations can affect any of the senses, although certain diseases or disorders are associated with specific types of hallucinations. It is important to distinguish between hallucinations and...

Definition Hairy cell leukemia is a disease in which a type of white blood cell called the lymphocyte, present in the blood and bone marrow, becomes malignant and proliferates. It is called hairy cell leukemiabecause the cells have tiny hair-like projections when viewed under the microscope. Description Hairy cell leukemia (HCL) is a rare cancer. It was...

Definition Hair transplantation is a surgical procedure used to treat baldness or hair loss (alopecia). Typically, tiny patches of scalp are removed from the back and sides of the head and implanted in the bald spots in the front and top of the head. Purpose Hair transplantation is a cosmetic procedure performed on men and occasionally on women who have significant hair loss,...

Definition Histamine H-2 receptor blockers act by stopping the pathway that leads to the secretion of stomach acid. There are two kinds of pathways that react to stimulation by histamine. Histamine is produced in the body and released by mast cells in response to some types of injury or to the presence of an antigen. When histamine reaches the H-1 receptors, the reaction results in dilation...

Definition Hyperglycemia is a complex metabolic condition characterized by abnormally high levels of blood sugar (blood glucose) in circulating blood, usually as a result of diabetes mellitus (types 1 and 2), although it can sometimes occur in cystic fibrosis and near-drowning (submersion injury). Description Hyperglycemia, also known as diabetic ketoacidosis, is a condition...

Hysteria is a neurosis in which the patient lacks control of his emotions. He may sincerely think he has some disease while he is physically well. He may have convincing symptoms that usually go with the disease which he subconsciously adopts. The type of person susceptible to hysteria is one who finds it difficult to face life's unpleasant realities. Whatever form hysteria takes, it is of a nature to...

The commonest cause of hoarseness is laryngitis, which usually occurs in connection with a common cold or a sore throat.  In cancer of the larynx, hoarseness is one of the earliest signs. Cancer of the larynx not only threatens the loss of the patient's larynx (leaving him without a voice), but threatens life. Persisting hoarseness without obvious cause is reason enough to arrange an early appointment...

Usually hiccups occur at intervals of several seconds, the attack lasting a few minutes and causing no harm. The symptom may become very troublesome, however, when it occurs in connection with a serious illness or following surgery. In some such cases the attack of hiccups may last for hours and may weaken the patient, even endangering his life. For a discussion of the treatment of hiccups, see more on ...

A hernia is the protrusion of a part of an organ through an abnormal opening in the tissues that surround or cover it. In the usual case, a hernia is a protrusion of a loop of the intestine through a weak place in the abdominal wall so that there appears a bulging, tender mass of tissue covered by skin. A hernia may be external or internal, the common internal type consisting of a protrusion of a part of the...

Heatstroke or Sunstroke Fortunately, true heatstroke is rare. It occurs in susceptible persons who have had a prolonged exposure to excessive heat or sun in a situation where circulation of air is inadequate. There is sudden loss of consciousness, very high fever, and absence of sweating. Convulsions, coma, and death may result. Often there are warning symptoms of weakness, headache, dizziness, nausea, and...

This type of prostration occurs when persons have been exposed to excessive heat and have perspired freely but have not taken sufficient salt (sodium chloride) or water to replace losses. This leaves the circulatory system at a disadvantage because the volume of body fluid has been reduced until the blood circulation through the small skin vessels is not brisk enough to keep the body cool. The skin feels cool...

This disorder is characterized by sudden cramps in the abdomen and the extremities when a person has been doing heavy work in a temperature above 1000 F. (380 C.) and has been perspiring profusely. It is the least serious of the three disorders caused by excessive heat. The condition results from a loss of salt from the body through excessive perspiration. It can be prevented or treated by taking salt tablets

(See Dyspepsia.) This symptom may be caused by a stretching of the esophagus (usually the lower part) either by swallowing too much food or drink in a single swallow or by the regurgitation of stomach contents into the lower esophagus. Heartburn does not indicate excess acidity in the stomach, for it may occur in persons who lack acid in their gastric juice. It occurs commonly in connection with dyspepsia.

The rate of heartbeat normally varies between 60 and 120per minute, depending on how active, physically and emotionally, the person is at the moment. When sitting quietly, the average healthy person's heart beats about 72 times per minute. Irregular heartbeat, or a rate abnormally slow or abnormally fast, or a rate which changes suddenly, can occur in either normal or diseased hearts. Such changes of rhythm...

Headache is one of mankind's commonest symptoms. The usual types of headache occur in response to the stresses, tensions, and thwartings of competitive living. The migraine type of headache is a severe, incapacitating headache which recurs periodically. It is usually associated with nausea, vomiting, dizziness, dryness of the mouth, changes in body temperature, changes in function of the digestive organs,...