Body systems

A large white blood cell in the tissues that swallows and digests germs, dead cells and debris.

A small spot; most often the macula lutea, the small yellowish area at the center of the retina that gives sharp central vision.

An eye disease in which the macula, the center of the retina used for sharp, straight-ahead vision, slowly breaks down.

Harm from a blood magnesium level that rises too high, usually during magnesium sulfate treatment.

A mental illness in which a person has a low mood or loses interest in almost everything for at least two weeks.

A body part or organ that formed in an abnormal way before birth.

A cancer, or the quality of being malignant: cells that grow out of control, invade nearby tissue and can spread to distant sites.

Cancerous: describing a tumor whose cells grow out of control, invade nearby tissue and can spread through the body.

A rare inherited reaction to certain general anesthesia drugs in which the muscles' metabolism speeds up out of control.

The outermost and largest of the three tiny bones of the middle ear, attached to the eardrum; also called the hammer.

A tear in the lining where the esophagus meets the stomach.

Poor nutrition from too little, too much or the wrong balance of nutrients.

A bite in which the upper and lower teeth do not meet as they should when the jaw closes.

The milk-making gland of the breast, a modified sweat gland arranged in about 15 to 20 lobes that drain to the nipple.

The lower jawbone, the only bone of the skull that moves.

A period of unusually high energy, mood and activity that is clearly different from the person's usual self.

The soft tissue inside bones; red marrow makes blood cells and yellow marrow stores fat.

A strong wave of contraction that sweeps the contents of the colon a long way toward the rectum, usually a few times a day around meals.

An immune cell in the tissues that releases histamine and other chemicals during allergic reactions and inflammation.

Surgery to remove all or part of a breast.

Chewing: grinding food between the teeth so it can be swallowed.

Inflammation of the breast tissue, often with infection, most common in people who are breastfeeding.

The rounded part of the temporal bone behind the ear, the mastoid process, which holds small air pockets that open into the middle ear.

Infection of the mastoid air cells in the bone behind the ear, usually spread from a middle ear infection.

Having to do with a mother, or with a woman during pregnancy, birth and the weeks after.

The process of becoming fully grown or developed.

One of the two bones that join to form the upper jaw, holding the upper teeth.

A spot on the lower right abdomen about one-third of the way from the front of the hip bone to the navel.

The average pressure in the arteries over one heartbeat, used as a measure of how well blood reaches the organs.

A very contagious illness caused by the measles virus; also called rubeola.

An opening or passage in the body, such as the urinary opening or the ear canal.

Breathing support from a machine, a ventilator, that pushes air into the lungs through a tube or a mask.

A newborn's first stools: thick, sticky and dark green to black.

Toward the middle line of the body.

A nerve of the brachial plexus that runs down the middle of the forearm and through the carpal tunnel into the hand.

The space in the middle of the chest between the two lungs, holding the heart, the great vessels, the trachea, the esophagus and the thymus.

The inner part of an organ; most often the medulla oblongata, the lowest part of the brainstem.

The hollow center of a long bone's shaft, which holds the bone marrow; also called the medullary canal.

Cell division that makes eggs or sperm, each with half the usual number of chromosomes.

The dark pigment that gives color to the skin, hair and eyes.

A cell in the bottom layer of the skin's outer layer that makes melanin, the pigment that gives skin and hair their color.

A hormone made by cells in the zone between the two lobes of the pituitary that makes melanocytes produce more melanin, darkening the skin.

A cancer that starts in melanocytes, the cells that give skin its color.

A hormone made by the pineal gland in the brain, mostly at night, that helps control the sleep-wake cycle.

Black, sticky stool that looks like tar.

A thin layer of tissue that covers, lines or separates parts of the body, or the outer layer of a cell.

A person's first menstrual period.

An inner ear disorder with attacks of vertigo, hearing loss, tinnitus and a feeling of fullness in the ear.

The three thin layers of tissue that cover and protect the brain and spinal cord.

Inflammation of the meninges, the membranes that cover the brain and spinal cord.