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The lesions of connective tissue

Scurvy is a disease caused by an acute lack of vitamin C. This leads to disruption of collagen synthesis, the connective tissue loses its strength. Symptoms are weakness, fatigue, weakening of muscle tone, rheumatic pain, loosening and loss of teeth; the fragility of the blood vessels leads to bleeding gums, bleeding in the skin. Treatment and prevention is normal providing of the body with vitamin C.

Collagenoses (connective tissue disease) are rheumatism, rheumatoid arthritis, systemic lupus erythematosus, systemic scleroderma, dermatomyositis. There is damage of all the structural components of connective tissue. All collagenoses are characterized by multiple organ lesions, vasculitis (inflammation and necrosis of the vascular wall), arthritis and immunity disorders.

The greatest recognition has the theory of infectious-allergic origin, in particular the concept of autoimmune origin.

Corticosteroid hormones and a variety of immunosuppressive drugs have the therapeutic effect.

Fibrosis is an abnormal growth of fibrous component of connective tissue, excessive accumulation of extracellular matrix with the appearance of scars of various organs. It is preceded by a sufficiently long phase of inflammatory disease, usually related to chronic action of damaging factors (ethanol in cirrhosis of the liver, inhalation of dust from pulmonary fibrosis, hyperglycemia in diabetic nephropathy, etc.).

Mucopolysaccharidosis (MPS) is a group of hereditary diseases of connective tissue due to metabolic disorders of glycosaminoglycans as a result of genetically determined deficiency of enzymes involved in their cleavage. Glycosaminoglycans are accumulated in large amounts in organs and tissues.

The main manifestations of MPS are the systemic failure of the skeleton, delayed physical development. The nervous system, eyes and internal organs are affected. There is a severe disturbance of child development and reducing life expectancy.

For the treatment hormones are prescribed: ACTH (adrenocorticotropic hormone) to inhibit the synthesis of mucopolysaccharides, thyreoidinum, prednisolone. Large doses of vitamin A and cardiac medications are used; there are attempts to treat with cytostatic agents.

More than 400 mutations of collagen are known; they are related to chondrodysplasia, some forms of osteoporosis and osteoarthritis.

Osteogenesis imperfecta is a rare disorder of connective and supporting tissue. The basis of the disease is mutations in one of two genes encoding collagen type I. The disease is characterized by abnormal fragility of the bones. In severe lesions multiple fractures occur already in utero, including fractures of the ribs. Many patients suffer from a shortened, deformed limbs, and fragile bell or barrel-shaped chest. In mild cases, there are some broken limbs, but often there are compression fractures of the spinal column.

Test Questions

1. List the functions of the extracellular matrix.

2. Describe the structure and biological role of main proteins of the extracellular matrix.



3. What enzymes play a major role in the catabolism of extracellular matrix proteins?

4. Explain the reasons for increased bleeding with a deficiency of vitamin C.

5. What compounds are called glycosaminoglycans? Give examples.

6. What role do proteoglycans in the cartilage of the articular surfaces?

7. Describe the biochemical changes of connective tissue with aging.


BLOOD BIOCHEMISTRY

The main functions of the blood are related to the fact that it is liquid movable tissue that moves through the blood vessels. The blood serves as a transport and communication tools for integration of metabolism of different organs. The main functions of blood include:

- respiratory function (transfer of O2 from the lungs to the tissues and CO2 from the tissues to the lungs);

- trophic function (transfer products of digestion from the intestine to different organs: the glucose and ketone bodies from the liver to the muscle, fat from the liver to adipose tissue, lactic acid from muscle to the liver, fatty acids from adipose tissue to different organs, etc.) ;

- excretory function (urea transport from the liver to the kidneys, bilirubin from different tissues to the liver, etc.);

- communicative (regulatory) function (the transfer of hormones and other regulatory agents to target organs).

Other functions of blood: protective, performed by antibodies and phagocytic leukocytes; involvement in the regulation of water-salt and acid-base balance; regulation of body temperature by heat exchange between the tissues and blood moving are also related with the movement of blood.

The total amount of blood in an adult is about 5 liters (about 7% of body weight). It consists of a liquid portion and formed elements: erythrocytes, leucocytes and platelets. After sells sedimentation by centrifugation, the light-transparent liquid remains. It is blood plasma. Plasma protein fibrinogen after keeping for some time becomes insoluble fibrin, which forms a clot. Fluid which is squeezed out of the bunch is the blood serum. The serum differs from the plasma in the way that it does not contain protein fibrinogen.

The plasma composition is a kind of mirror of metabolism, because changes in the concentration of metabolites in cells, even if they occur in individual organs, are reflected in the concentrations of these metabolites in the blood.

Blood plasma is approximately 10% aqueous solution of organic and mineral substances. The concentration of protein is about 7%, mineral salts, about 1%, the rest is various non-protein organic compounds: urea, bilirubin, indican, creatine, creatinine, uric acid, glucose, fructose, lactic acid, pyruvic acid, etc.

Plasma proteins are represented by five fractions: albumins, α1-globulins, α2-globulins, β-globulins and g-globulins. Each of these fractions is a mixture of different proteins. The most homogeneous is albumin fraction. g-globulin fraction contains primarily antibodies (immunoglobulins). Other fractions are heterogeneous. Most of the proteins in plasma are synthesized in the liver.

The fraction of albumin is more than half (55-60% or 40-50 g / l) of the blood plasma proteins. Albumins transport of many biologically active substances (hormones, fatty acids in the mobilization of fats from fat depots). They can bind with cholesterol and bile pigments. A significant portion of calcium in serum is also bound with albumins. Albumins play an important role in maintaining the oncotic pressure of blood. When the concentration of albumin in serum is less than 30 g/l it causes significant changes in oncotic pressure of blood that leads to edema. The concentration of albumin in the blood can decrease because of its excretion in the urine in kidney diseases (albuminuria). The human liver synthesizes and secretes into the blood up to 15 g of albumin per day. In some diseases of the liver (cirrhosis), albumin synthesis is disturbed. These states are also characterized by edema.

Globulins are presented by two fractions - euglobulins and pseudo-globulins. Euglobulin fraction consists mainly of g-globulins, and fraction of pseudo-globulins consists of α-, β- and g-globulins. Most of the antibodies found in the fraction of g-globulins. Immunoglobulins, or antibodies are synthesized by β-lymphocytes or by plasma cells formed from them. In a number of pathological conditions hyperproteinemiacan occur due to increasing levels of g-globulins: for example, as a result of infection.

In many diseases proportion of individual protein fractions of blood plasma is changed, although the total protein content in the blood serum remains within normal limits. This condition is called dysproteinemia.

 


Date: 2016-04-22; view: 490


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