Thymus 3p1y13

Thymus The Gland that Protects You Long after It’s Gone  Pinkish-gray organ has two thymic lobes.  The thymus reaches its maximum weight (about 1 ounce)

during puberty  Throughout the childhood years, white blood cells called lymphocytes through the thymus, where they are transformed into T cells  Once T cells have fully matured in the thymus, they migrate to the lymph nodes (groups of immune system cells) throughout the body, where they aid the immune system in fighting disease  Some lymphocytes, regardless if they reside in the lymph nodes or thymus can develop into cancers (known as Hodgkin disease and non-Hodgkinlymphomas)

Cont’n  Though the thymus gland is only active until puberty, its

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double-duty function as an endocrine and lymphatic gland plays a significant role in your long-term health The thymus gland, located behind your sternum and between your lungs After puberty, the thymus starts to slowly shrink and become replaced by fat Thymosin is the hormone of the thymus, and it stimulates the development of disease-fighting T cells It will not function through out a full lifetime Has a big responsibility when it’s active it helps the body protect itself against autoimmunity The thymus is special in that, unlike most organs, it is at its largest in children

Two main kinds of cancer that can develop in the thymus 1. Thymoma- is a tumor in which the cancerous cells look very similar to those of normal thymus tissue associated with autoimmune diseases in which the immune system attacks healthy tissue. Thymomas are generally benign, but they can become malignant 2. Thymic carcinomas-have cells that do not resemble thymus cells are particularly dangerous because they grow more rapidly and are more likely to spread to other tissues 

Both thymomas and thymic carcinomas can be present without causing any symptoms

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When cancer of the thymus gland does cause symptoms it can lead to a cough and chest pain

What is myasthenia gravis?  Myasthenia gravis -is a chronic autoimmune neuromuscular disease

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characterized by varying degrees of weakness of the skeletal (voluntary) muscles of the body The name myasthenia gravis, which is Latin and Greek in origin, literally means "grave muscle weakness" With current therapies, however, most cases of myasthenia gravis are not as "grave" as the name implies Most individuals with myasthenia gravis have a normal life expectancy The hallmark of myasthenia gravis is muscle weakness that increases during periods of activity and improves after periods of rest Certain muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are often, but not always, involved in the disorder The muscles that control breathing and neck and limb movements may also be affected

What causes myasthenia gravis? a. A defect in the transmission of nerve impulses to muscles b. When antibodies blocks, alter, or destroy the receptors for acetylcholine at the Neuromuscular junction which prevent the muscle for contraction from occurring c. An autoimmune disease because the immune system which normally protects the body from foreign organisms—mistakenly attacks itself What is the Role of the Thymus Gland in Myasthenia Gravis? a. In adults with myasthenia gravis, the thymus gland remains large and is abnormal b. It contains certain clusters of immune cells indicative of Lymphoid Hyperplasia—a condition usually found only in the spleen and lymph nodes during an active immune response c. Some individuals with myasthenia gravis develop thymomas (tumors of the thymus gland)

Symptoms of myasthenia gravis? a. Weakness of the eye muscles. b. In others, difficulty in swallowing and slurred/impaired speech (dysarthria) c. Drooping of one or both eyelids (ptosis) d. Blurred or double vision (diplopia) e. Unstable or waddling gait f. A change in facial expression g. Shortness of breath h. Weakness is the arms, hands, fingers, legs, and neck

 Who gets myasthenia gravis?  It occurs in all ethnic groups and both genders  It most commonly affects young adult women (under 40) and older   

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men (over 60) It can occur at any age In neonatal myasthenia, the fetus may acquire immune proteins (antibodies) from a mother affected with myasthenia gravis Generally, cases of neonatal myasthenia gravis are temporary and the child's symptoms usually disappear within 2-3 months after birth Other children develop myasthenia gravis indistinguishable from adults Myasthenia gravis in juveniles is uncommon. Myasthenia gravis is not directly inherited nor is it contagious Occasionally, the disease may occur in more than one member of the same family Rarely, children may show signs of congenital myasthenia or congenital myasthenic syndrome

Cont’n  These are not autoimmune disorders, but are

caused by defective genes that produce abnormal proteins instead of those which normally would produce acetylcholine, acetylcholinesterase (the enzyme that breaks down acetylcholine), or the acetylcholine receptor and other proteins present along the muscle membrane.

How is myasthenia gravis diagnosed? a. Diagnosing myasthenia gravis include a review of the individual's medical history, and physical and neurological examinations b. The physician looks for impairment of eye movements or muscle weakness without any changes in the individual's ability to feel things c. Several tests to confirm the diagnosis. d. A special blood test detect the presence of immune molecules or acetylcholine receptor antibodies e. The edrophonium test f. Version of nerve conduction study which tests for specific muscle "fatigue" by repetitive g. Single fiber electromyography (EMG) h. Diagnostic imaging of the chest, using computed tomography (CT) or magnetic resonance imaging (MRI) i. Pulmonary function testing

 How is myasthenia gravis treated?

a. Anticholinesterase agents such as neostigmine and pyridostigmine, b. Immunosuppressive drugs such as prednisone, azathioprine, cyclosporin, mycophenolate mofetil, andtacrolimus c. Thymectomy, the surgical removal of the thymus gland d. Plasmapheresis, a procedure in which serum containing the abnormal antibodies is removed from the blood while cells are replaced What are myasthenic crises?  Occurs when the muscles that control breathing weaken to the point that ventilation is inadequate, creating a medical emergency and requiring a respirator for assisted ventilation