Atrophy Definitions – Types and comparisons

Atrophy definition

Atrophy is a reduction in size or mass, due to a reduction in the size of cells. It can also mean wasting away. The word is most commonly used in relation to muscle, although any organ in the body can atrophy.

Muscle Atrophy definition

Muscle atrophy is thinning and weakening of muscles mostly in limbs.

If you have ever been confined to a wheelchair or bed for a long time (maybe due to a broken limb), you would have noticed that the affected leg or hand was getting “thinner”. This “thinning” is caused by a reduction in the size of the muscles in that limb, known as muscle atrophy.
Muscle atrophy usually arises from disuse. If a particular muscle is not used, it begins to waste away. This wasting away is seen as a reduction in size of that particular body part. Muscle atrophy can also arise from neurogenic causes (that is, from the nerve that stimulates that muscle)

Neurogenic atrophy definition

Neurogenic atrophy is an atrophy caused by damage to the nerve stimulating that muscle. It is usually more severe than disuse atrophy and occurs more suddenly. Every muscle (and in fact, every organ in the body) is supplied by a particular nerve which stimulates the muscle to contract or relax. When the nerve is damaged by injury or disease, the muscle cannot move, because it can’t receive instructions from the brain or spinal cord. Lack of use over time will lead to atrophy.

Spinal Muscular Atrophy definition

Spinal Muscular Atrophy (SMA) is a genetic disease of the nerves which control voluntary movement. It is an inherited disease and affects about one in 10,000 newborns. Males are affected more than females.
People with SMA have a disruption of a gene called the survival motor neuron (SMN) gene which codes for the lower motor neurons (the nerves that control voluntary movement). The affected nerves are largely located in the spinal cord (hence the word “spinal”). They degenerate progressively, and as they do, the muscles they control lose the ability to move, leading to muscle atrophy and weakness. Muscle atrophy in SMA is progressive (that is, it gets worse gradually).
Atrophy in other structures
Atrophy is not confined to muscle alone. Any organ of the body can atrophy. However, atrophy takes on a new meaning when we refer to the brain and spinal cord. Here, atrophy refers to the loss of neurons and their connections, leading to shrinkage.

Brain Atrophy definition

Brain atrophy in simple words is shrinking of Brain size.

Brain atrophy is a feature in many diseases affecting the brain. It can be generalized (meaning that the whole brain is shrunken), or focal (i.e. affecting only a part of the brain). The symptoms that follow depend on the part of the brain affected, the functions it controls and the severity of atrophy. For example, if the cerebellum is affected, the person may develop an unsteady gait.
Brain atrophy occurs naturally as we age, but progresses faster from around the age of 60.

Multiple System Atrophy definition

Multiple system atrophy is a neurodegenerative disease (that is, caused by degeneration of nerve or brain cells). Specific portions of the brain and spinal cord are lost rapidly. It is a very serious and highly fatal disease. It is characterized by uncoordinated movements and unsteady gait. People with MSA may get dizzy or faint when they stand up from a sitting position and might have poor bladder control. Its cause is not known. It occurs in adulthood and men are more affected than women.

Posterior cortical Atrophy definition

Posterior cortical atrophy is  a degeneration of nerve cells in the posterior (back) area of the brain. This area controls vision, so people with PCA may have blurred vision and difficulty with reading, which are the early signs.This is a progressive disease of the brain similar to Alzheimer’s disease.
Posterior cortical atrophy typically affects people at a younger age than Alzheimer’s. The cause is not known.
As the disease progresses, patients will have problems with coordinating their movement, recognizing people or objects and remembering things.

Spinal cord Atrophy definition

Spinal cord atrophy is usually a “narrowing” of the spinal cord when magnetic resonance imaging (MRI) is done. It can be caused by an injury to the spinal cord (maybe due to a car crash or very bad fall). The injury may cause the death of cells at the site, leading later to atrophy. Atrophy of the spinal cord is also a feature in diseases such as multiple sclerosis.

The spinal cord is a long, roughly cylindrical structure located inside the backbone. It extends from the base of the skull to a level around the top of the hip bone. It is an extension of the medulla oblongata of the brain. It serves as a pathway for the transmission of messages from the brain to other parts of the body and vice versa.

Optic nerve Atrophy definition

Optic nerve atrophy is a condition caused by degeneration of the nerve cell projections that carry messages from the retina of the eye to the brain. It is a common end-point of many conditions affecting the eyes. The optic nerve cells themselves are located in the retina, but their projections (called axons) extend all the way to the brain. These axons do not regenerate if they’re damaged. Damage to the axons can be caused by an injury, a tumor or conditions such as glaucoma, multiple sclerosis or increased pressure within the skull.
People with optic nerve atrophy have vision problems, though the severity of their symptoms will vary according to the cause. Optic nerve atrophy can be diagnosed when the eye is examined with an ophthalmoscope.

Hypertrophy definition

Hypertrophy is the direct opposite of atrophy. It is the increase in the size of an organ or structure due to an increase in the size of the cells that make up that organ.

Muscle hypertrophy definition

Muscle hypertrophy is an increase in muscle size caused by an increase in the size of the cells in that muscle. Muscle, like every part of the body, is composed of tiny cells too small to be seen by the naked eye. Muscle hypertrophy occurs naturally as a part of the normal body changes in puberty. This type of hypertrophy is however more pronounced in males and stops when full adult size is attained.If you lift weights for some time, you would begin to notice an increase in the size of your muscles, particularly your biceps and chest muscles. This increase is known as muscle hypertrophy.
Muscle hypertrophy can also be stimulated by exercise. Rigorous exercise of a muscle, (as in strength training) uses up the oxygen available to the muscle, creating an aerobic condition (anaerobic simply means “without oxygen”). Repeated exposure to anaerobic conditions makes the muscle cells to increase in size, as an adaptive process to reduce fatigue.

Prostate hypertrophy definition

Enlarged prostate gland is Prostate hypertrophy also called as Prostate hyperplasia.

The prostate is a small organ, about the size of a walnut, located just beneath the bladder in males. It surrounds the urethra, the tube through which urine passes from the bladder to the outside.Prostate hyperplasia is increase in size due to an increase in the number of cells.

Prostate hyperplasia may be benign (non-cancerous) or due to cancer of the prostate.
Benign prostate hyperplasia (BPH) occurs naturally as men age. In fact, almost half of all men have some proliferation of prostate cells by the age of 60, which invariably leads to prostate enlargement. However, prostate enlargement, while being common, does not affect all men equally. As the prostate enlarges, it presses on the urethra, leading to problems with urine flow such as dribbling and incomplete bladder emptying.

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