Acclimatization to altitude: The process of adapting to the decrease in oxygen concentration at a specific altitude. A number of changes must take place for the body to operate with decreased oxygen. These changes include increasing the depth of respiration; increasing the pressure in the pulmonary arteries, forcing blood into portions of the lung that are normally not used at sea level; manufacturing additional oxygen-carrying red blood cells; and manufacturing extra2,4-DPG, a substance that facilitates the release of oxygen from hemoglobin to the body tissues. Acclimatization generally takes 1 to3 days and occurs after any significant altitude change above 1,220 meters (approximately4,000 feet). Acclimatization is the body’s natural means of correcting altitude sickness and the rate of acclimatization depends on the altitude, rate of ascent, and individual susceptibility.
- Accessory neuropathy
Accessory neuropathy: A disease of the accessory nerve, paralysis of which prevents rotation of the head away from one or both sides and causes the shoulder to droop. Damage can be confined to the accessory nerve, or it may also involve the ninth and tenth cranial nerves, which exit the skull through the same opening.
Accoucheuse: French for a woman who is an obstetrician (a physician skilled in the art and science of managing pregnancy, labor and the time after delivery) or a midwife (today a non-physician trained to assist a woman during childbirth). The ending “-euse” is feminine and indicates that the accoucheuse is a woman.
Accommodation: In medicine, the ability of the eye to change its focus from distant to near objects (and vice versa). This process is achieved by the lens changing its shape. Accommodation is the adjustment of the optics of the eye to keep an object in focus on the retina as its distance from the eye […]
Acellular: Not made up of cells or divided into cells. Or lacking intact cells as, for example, an acellular vaccine which may contain cellular material but not complete cells.
- Acellular vaccine
Acellular vaccine: A vaccine that may contain cellular material but does not contain complete cells.