- How does the muscular system
- heart What does the mass of the myocardium
- mechanism heartbeat
- What affects the contractility of the process?
- Properties myocardial infarction
- Types defeat
- Features myocarditis
- Violations of myocardial metabolism
- When a myocardial hypertrophy?
- defeat myocardial ischemia
- How does the myocardium with coronary artery thrombosis?
- Can you confirm necrosis laboratory methods?
If we forget about the lyrical digressions, the heart is a hollow organ, "suspended" and mounted in a special bag of powerful ligaments.About the size of a normal heart can be judged by comparison with the volume of human fist.For
organism indispensable function performed by the pumping - pumping blood, thereby providing the transport of oxygen and nutrients to all tissues, the delivery for processing waste.
How does the muscular system of the heart
myocardium - the thickest layer of the heart, is located midway between the endocardium (inner layer) and epicardium outside.feature is the ability of the heart atria and the ventricles to contract on their own, independently of each other, even to "work" offline.
contractile capacity is provided by special fibers (myofibrils).They combine the features of skeletal and smooth muscle tissue.Therefore:
- distribute the load evenly across all departments;
- have striated striation;
- ensure non-stop operation of the heart all human life;
- reduced independently of the influence of consciousness.
core muscle cells make up the myocytes
Each cell has an elongated kernel with a large number of chromosomes.Due to this more myocytes "tenacious" in comparison with other cells and tissues are capable of withstanding considerable loads.
atrial and ventricular myocardium are of different density:
- in the atria, it consists of two layers (superficial and deep), which differ in the direction of the fibers are arranged laterally transverse or circular myofibrils, and inside - longitudinal.
- ventricles provide an additional third layer lying between the first two, with the horizontal direction of the fibers.This mechanism reinforces and supports the force of contraction.
What does the mass of the myocardium of the heart
total mass of an adult - 300 The development of methods of ultrasonic diagnosis has allowed to calculate the weight of that part relating to the myocardium.The average index of myocardial mass for men - 135 g, women - 141, the exact weight is determined by the formula.It depends on:
- size of the left ventricle in the diastolic phase;
- thickness of the interventricular septum and posterior wall.
even more specific for the diagnosis of an indicator such as myocardial mass index.To the left ventricle normal men is 71 g / m2, women - 62. This value is calculated automatically when the computer making the human growth data, body surface area.
heart Through the development of electron microscopy found the internal structure of the myocardium, myocyte structure providing contractility property.Revealed thick and thin protein chains, called "actin" and "myosin".When actin fibers slide on myosin, muscle contraction occurs (systole phase).
biochemical mechanism of reduction is the formation of a common substance "actomyosin".An important role is played by potassium.Coming out of the cells, it promotes the connection of actin and myosin and the energy absorption by them.
Energy balance in myocytes maintained by replenishment relaxation phase (diastole).This process involves biochemical components:
- enzymes and coenzymes (in their role particularly important B vitamins),
- lactic and pyruvic acid,
- ketone bodies.
- amino acids.
What affects the contractility of the process?
Any diastolic dysfunction violates the energy production, the heart loses its "feeding", not resting.On myocyte metabolism is influenced by:
- nerve impulses coming from the brain and spinal cord;
- lack or excess of "components" for biochemical reactions;
- violation of receipt of necessary substances in coronary vessels.
myocardial perfusion is carried out on coronary artery extending from the base of the aorta.They are sent to different departments of the ventricles and atria, split into small branches that feed the deeper layers.An important adaptive mechanism - a system of collateral (auxiliary) vessels.It reserved the artery, normally located in the sleeping state.For inclusion in mainstream circulation should break down the main vessels (spasm, thrombosis, atherosclerotic damage).It is this provision is able to limit the infarction zone, provides compensation in the event of food thickening of myocardial hypertrophy.Support
satisfactory contractility is required for prevention of heart failure.
properties of heart muscle
Besides contraction, myocardium has other exceptional properties that are unique to the muscular tissue of the heart:
- conductivity - equates myocytes to the nerve fibers, as they are also able to conduct impulses, passing them from one site to the other.
- excitability - for 0.4 seconds.excitement comes in the whole muscular structure of the heart and provides a complete ejection of blood.The correct heart rhythm depends on the appearance of excitation in the sinus node, located in the back of the right atrium and further the pulse on the fibers to the ventricles.
- automatism - the ability to independently form the focus of excitation, bypassing the established direction.This mechanism is a violation of the right rhythm, as other areas take on the role of the driver.
hearth called "ectopic" detected on an electrocardiogram
Other myocardial diseases accompanied by minor or severe disorders of these functions.They determine the clinical characteristics of the course and require a special approach to the treatment.
consider the pathological changes in the myocardium and their role in the occurrence of certain diseases of the heart muscle.
All myocardial injury are divided into:
- noncoronary myocardial disease - characterized by lack of communication with the defeat of the causes of coronary arteries.These include inflammatory disease or myocarditis, degenerative and non-specific changes in the myocardium.
- Koronarogennye - the consequences of impaired patency of the coronary vessels (foci of ischemia, necrosis, focal or diffuse Cardiosclerosis, scarring).
myocarditis Myocarditis often found in men, women and children.Most often they are associated with inflammation of certain sites (focal) or just heart muscle layer (diffuse).The causes are infectious diseases (influenza, rickettsioses, diphtheria, scarlet fever, measles, typhus, sepsis, poliomyelitis, tuberculosis).
preventive work to form a sufficient protective response through vaccination possible to limit the disease.However, there remain serious problems in the heart after nasal diseases due to the development of chronic rheumatic process.Non-rheumatic myocarditis associated with severe stage uremic coma, acute nephritis.Chance of autoimmune nature of the inflammatory response, flowing like an allergy.
Histologically among muscle cells exhibit:
- granulomas typical structure for rheumatism;
- swelling from an accumulation of basophils and eosinophils;
- death of muscle cells with the growth of connective tissue;
- accumulation of fluid between cells (serous, fibrinous);
- areas dystrophy.
result in all cases is impaired myocardial contractility.
clinical picture is diverse.It consists of the symptoms of cardiac and vascular disease, arrhythmias.Sometimes simultaneously affects the endocardium and pericardium.
usually more likely to develop right heart failure by type, as the myocardium of the right ventricle is weaker and the first fails.
pain in the heart - the main symptom of myocarditis
Patients complain of shortness of breath, palpitations, a feeling of disruption against the backdrop of an acute illness or after infection.
Rheumatic inflammation is always accompanied by endocarditis, the process necessarily extend to the valve unit.If you delay treatment formed defect.For a good response to therapy typical temporal rhythm and conduction disturbances without consequences.
Disorders myocardial metabolism
metabolic disorders often accompany myocarditis and coronary heart disease.Find out what is primary, not predstavlyaetcya possible, so this is related pathology.Due to the lack of materials for energy production in cells, lack of oxygen in the blood at a thyrotoxicosis, anemia, beriberi myofibrils are replaced by scar tissue.
heart muscle begins to atrophy, weaken.This process is typical for the elderly.A special form is accompanied by the deposition of pigment lipofuscin in the cells, so that when the histology of the heart muscle changes color to red-brown, and the process is known as "brown myocardial atrophy."Simultaneously degenerative changes are found in other organs.
When a myocardial hypertrophy?
most common cause hypertrophic changes in the heart muscle is hypertension.Increased vascular resistance causes the heart to work against high loads.
For the development of concentric hypertrophy is characterized by: the volume of the left ventricle cavity kept unchanged at a total growth of sizes.
Symptomatic hypertension with kidney disease, endocrine disorders are less common.Moderate thickening of the ventricular wall hinders germination vessels in the mass depth, so the state is accompanied by ischemia and anoxia.
Cardiomyopathy - diseases with unknown causes, combine all the possible mechanisms of myocardial damage by increasing degeneration, leading to an increase in ventricular cavity (dilated form), to severe hypertrophy (restrictive, hypertrophic).
left ventricular muscle reaches a thickness of 3 cm
particular embodiment cardiomyopathy - a sponge or non-compact myocardium of the left ventricle is congenital in nature, often associated with other malformations of the heart and blood vessels.Normally, the non-compact myocardium is a stake in the heart mass.It increases in hypertension, hypertrophic cardiomyopathy.
Pathology revealed only in adulthood the symptoms of heart failure, arrhythmias, embolic complications.When the color Doppler image is obtained in the study of several projections and noncompact plots measured thickness during systole and diastole did not.
defeat myocardial ischemia
In 90% of cases in the coronary arteries in coronary disease found atherosclerotic plaques, overlapping feeding artery diameter.A role played by metabolic changes under the influence of impaired nervous regulation - the accumulation of catecholamines.
When infarction angina condition can be described as a forced "hibernation" (hibernate).Hibernating myocardium is an adaptive response to oxygen deficiency, the molecules of adenosine triphosphate, potassium ions, the main suppliers of calories.There is local areas with prolonged poor circulation.
maintain a balance between the reduction of contractility in accordance with circulatory disorders.In this case, the cells are viable myocytes and can fully recover with improved nutrition.
«stunned myocardium» - a modern term used to describe the condition of the heart muscle recovery after coronary circulation in the area of the heart.The cells for several days accumulate energy, impaired contractility in this period.It should be distinguished from the phrase "myocardial remodeling," which means the actual changes in myocytes exposed to pathological causes.
How does the myocardium with coronary artery thrombosis?
prolonged spasm or blockage of the coronary arteries cause necrosis of the muscle area, which they supply blood.If this process is slow, collateral vessels will take the "work" and prevent necrosis.
Most often affects the left ventricle in the basin of the anterior descending artery
infarct located in the top, front, rear and side walls of the left ventricle.Rarely captures the septum and right ventricle.Necrosis occurs in the bottom wall in the right coronary artery occlusion.
If clinical signs and ECG pattern converge to confirm the form of the disease, the diagnosis can be sure and use a combination treatment.But there are cases that require confirmation of the doctor's opinion, primarily with the help of precise indisputable markers of myocardial necrosis.Generally, diagnosis is based on the quantitative determination of a more or less specific to necrotic tissue decay products, enzymes.
Can you confirm necrosis laboratory methods?
development of modern biochemical diagnosis of myocardial possible to identify the standard of myocardial necrosis markers for early and late manifestations of heart attack.
recognized as the most significant growth in the dynamics of the content of substances in 6-9 hours, 9-12 hours after the onset of pain
The early markers include:
- Myoglobin - increased in the first 2 hours for optimum utilization indexmonitor the effectiveness of the action of fibrinolytic therapy.
- creatine phosphokinase (CPK) - a fraction of the cardiac muscle is only 3% of the total weight, so if you can not only define this part of the enzyme, the diagnostic value of the test does not.When myocardial necrosis increased in the second or third day.The growth rate is possible in renal failure, hypothyroidism, cancer.
- Heart type of protein, fatty acid binding - except there infarction in the aortic wall, diaphragm.It regarded as the most specific indicator.
late markers are considered:
- Lactate dehydrogenase, the first isoenzyme - reaches the highest level to the sixth or seventh day, then decreases.The test is recognized as a low specificity.
- aspartate aminotransferase - peaks to the 36th hour.Due to the low specificity is used only in conjunction with other tests.
- cardiac troponin - are stored in the blood up to two weeks.