The kidney has several important functions including filtering out waste from the blood, regulating the water-electrolyte balance in the body and controlling the blood pressure. The basic functional unit of the kidney is the nephron which is made up of two main parts – the glomerulus and tubule. Firstly the head of the nephron, known as the glomerulus, collects fluid and substances that filter out from the blood capillaries next to it. Then the remainder of the nephron, the tubule, reabsorbs or secretes fluid and certain substances until the urine is formed and passed out of the kidney. This fluid and substances are either absorbed from, or passed out into the surrounding kidney tissue known as the interstitium. When the nephron is damaged, these mechanisms are severely disturbed. The damage may involve the entire kidney, or may be isolated to one part of the nephron like the glomerulus or tubule and/or surrounding tissue (interstitium). This ultimately disturbs the kidney’s functions to varying degrees.
A heart attack, or myocardial infarction (MI), is the death of a portion of the heart wall when there is an interruption in its blood supply. The heart wall is composed of three layers – the inner lining (endocardium), middle muscle layer (myocardium) and outer lining (epicardium) – and has its own supply of oxygen and nutrient-rich blood via the coronary arteries. There is usually underlying disease of the coronary artery, like atherosclerosis, where fatty plaques build up in the arterial wall. This is known as coronary artery disease and reduces the blood flow to portions of the heart wall. It is often asymptomatic if the extent of occlusion is less than 75% of the diameter of the arterial lumen.
About half of the deaths associated with a heart attack occurs within the first hour and these patients never reach the hospital. Not every myocardial infarction (heart attack) is fatal and the advances made in modern medicine has drastically reduced the mortality associated with a myocardial infarction. However, there is no avoiding that fact that a heart attack is a serious clinical event that permanently compromises heart function to some degree for the rest of the patient’s life. There are several complications that arise immediately after a heart attack and within days and even months thereafter, some of which may be life-threatening in the short to long term. All these complications further compromise the heart function and contribute to the overall presentation of the heart disease following a heart attack.
The heart muscle, known as the myocardium, constitutes the bulk of the heart wall. It is responsible for the pumping action of the heart which serves to distribute blood throughout the body. The heart is functioning throughout life, although its activity may increase or decrease during different periods of cardiac demand. Normally, the heart beats between 60 to 80 times per minute when the heart muscle contracts and then relaxes repeatedly.
There are four chambers in the heart – two atria and two ventricles. The right side of the heart receives dexoygenated blood from the body in the atrium and then the ventricles pumps it out to the lungs. Here carbon dioxide is discarded and oxygen absorbed. The now oxygenated blood from the lungs then returns to the left side of the heart. It enters the left atrium and then from the left ventricle it is pumped out to the rest of the body via the large artery known as the aorta. Small sinuses at the root of the aorta allows blood to enter the coronary arteries which provide the blood supply to the heart.
Hypertension is the elevated pressure exerted by the blood on the walls of the blood vessels. A sustained arterial pressure of 140/90 mm Hg (systolic pressure of 140 mm Hg and/or diastolic pressure of 90 mm Hg) or more is conventionally considered to be hypertension. It is the most common cardiovascular disease in the United States affecting over 20% of the American population.
Hypertension is primarily of two types, the primary or essential hypertension and the secondary hypertension. Essential hypertension is the most common type accounting for more than 90% of all hypertensive patients. The exact cause of essential hypertension is not clearly understood and it is considered to develop as a result of multiple factors. There are numerous types of drugs available to effectively control essential hypertension but no single drug has been successful in curing the disease. Secondary hypertension is a raised blood pressure that is associated with a definite recognizable cause like some other underlying disease. Many of the causes of secondary hypertension can be treated leading to complete cure of hypertension.
The hearts has its own electrical system to control the rate and rhythm of the heart beat. Impulses are generated in the sinoatrial node (SA node) and immediately cause the muscles of the atria to contract. This pushes blood into the ventricles. The impulse travels along the internodal pathways to the atrioventricular node (AV) node where it is delayed. This ensures that the ventricles do not contract at the same time as the atria. After a few milliseconds, the impulses leave the AV node and dissipate to the muscles of the ventricles thereby causing it to contract. Blood is then pushed out of the ventricles and into the pulmonary or systemic circulation.
The electrical system can increase or decrease the heart rate as needed throughout the day. The rhythm, however, stays the same – atria contract and then the ventricles a short while later. This process is continuous throughout life. Sometimes heart disease and other conditions may change the rate and rhythm of the heart activity and this causes various disturbances in circulation. These abnormal alterations of the rate and rhythm is known as an arrhythmia. Some arrhythmias are life-threatening and can disrupt heart activity to such a degree that normal heart function ceases altogether.
The heart has thick walls mainly composed of muscle in order for it to maintain its functioning of pumping blood throughout the body. This muscular layer is known as the myocardium and surrounded by the inner lining (endocardium) and outer layers (epicardium). The heart is working throughout life, contracting and relaxing, to ensure that blood is constantly in circulation.
Muscle cells in general are demanding of both oxygen and nutrients and the myocardium is no different. Although the heart is the central organ of circulation, the myocardium does not derive its oxygen supply from within the heart but is instead dependent on the coronary arteries for a constant flow of oxygen and nutrients. When any part of the body is deprived of an adequate blood supply, yet still has a sufficient flow to sustain life, it undergoes injury known as ischemia. In terms of the heart muscle this is known as myocardial ischemia.
A throat infection is one of the most common upper respiratory tract conditions affecting every person at some point in life. The most common pathogens are viruses and then bacteria. Among the different types of bacteria, it is the group A streptococci (Streptococcus pyogenes) that are more commonly involved in a sore throat. The infection causes widespread inflammation of the throat (pharynx) and is therefore known as streptococcal pharyngitis or commonly as strep throat. The immune system elicits the appropriate response against the infection and antibiotics also help with fighting off the infection. Sometimes the immune activity against becomes disrupted and is then directed towards the body’s own tissues. Rheumatic fever occurs a period after the strep throat infection and affects many organs and systems.
The immune system has several mechanisms to neutralize invading microorganisms, limit the damage to the body and totally eradicate the infection. This immune response is a carefully coordinated sequence of events that ensures that the invaders are specifically targeted and the body’s tissues are spared. However, sometimes this process is disrupted and the immune system causes damage of otherwise healthy tissue. Rheumatic fever is one example of this inappropriate response and tends to arise several weeks after a certain type of bacterial throat infection. Inflammation is widespread and involves many systems of the body, including the heart. It is an acute reaction that can last several weeks and usually does not cause any permanent damage to any part of the body, except for the heart valves in some cases.
The joints experience a significant amount of stress and strain throughout life. From bearing the body weight to endlessly moving in daily activity, joints are prone to a range of injuries and diseases as is the case with any part of the body. Joint pain is known as arthralgia and may affect any joint in the body. It can be associated with other signs and symptoms like stiffness, swelling of the joint, redness of the overlying skin and decreased mobility. Pain may occur in small or large joints only or in both simultaneously. Similarly, the pain may be isolated to a single joint (monoarticular pain) or affect several joints at the same time (polyarticular pain). Some types of injury and certain diseases tend to affect specific joints, while at other times the disorder may not be as discriminatory and there is generalized arthritis.
Joints are the flexible parts of the body that allow for various degree of movements between two or more bones. In order to understand the anatomy of the wrist and hand joints, it is first important to identify all the bones in this part of the upper limb. The bones of the forearm include the radius and ulna which extend from the elbow joint to the wrist joint where it articulates with the wrist bones (carpal bone).
The wrist itself is known as the carpus and is made up of eight carpal bones. It also articulates with the hand bones known as the metacarpals of which there are five in the human hand. These metacarpals in turn articulate with the finger bones known as the phalanges (singular ~ phalanx). In the four fingers, excluding the thumb, there is three finger bones known as the proximal, middle and distal phalanges. The thumb has only two finger bones – the proximal and distal metacarpals.
The heart valves are important structures in the heart and at its junction with the major arteries. By opening and closing at different stages of heart contraction, these valves ensure that blood flows in one direction through the heart. There are four main valves in the heart and blood vessels – one between the atrium and ventricle on each side (atrioventricular or AV valve) and one in each large artery that carries blood out of the ventricles (semilunar valve).When the valve closes, blood cannot flow backward (regurgitation) but also needs to open fully and not impair flow of blood in the correct direction.
Hypertension is a blood pressure measuring 140/90 mmHg or greater most of the time. Blood pressure fluctuates throughout the day but normally does exceed levels above 130/80 mmHg except in acute stress or shock. A normal blood pressure may even drop as low as 100/60 mmHg during relaxed periods and sleep. With hypertension the persistently high blood pressure has a host of effects on the body. In the short term this is not often life threatening particularly if it is a moderate elevation. However, if chronic hypertension is left untreated, it can be detrimental to many organs and systems in the body. Irrespective of the cause, the heart is also affected by hypertension and may undergo various changes that can impair its functioning.
The heart receives blood in its atria and pushes out blood from its ventricles. There are four such chambers in the heart – right and left atria (singular ~ atrium) and the right and left ventricles. The right side of the heart (right atrium and right ventricles) handles deoxygenated blood (blood that is low in oxygen). This is also known as the pulmonary circulation. The left side of the heart (left atrium and ventricle) handles the oxygenated blood (blood rich in oxygen) which is also referred to as the systemic circulation. The blood on either side is kept separate so that deoxygenated and oxygenated blood does not mix. A wall between the right and left side of the heart, known as the atrioventricular (AV) septum, ensures that blood stays in its respective side. However, if there is any abnormality during fetal heart development, this septum may be compromised.
Congenital heart defects arise in the fetal stage in life when the development of the heart and/or great blood vessels is disrupted in some manner. This leads to a structural abnormality in the heart or vessels which depending on the type and extent may case mild to severe symptoms or can even be life threatening. The heart is a a muscular pump with four chambers – two atria that receive blood and two ventricles that push out blood. The atrium and ventricle on each side are separated by heart valves which open and close at different stages of the cardiac cycle. Similarly the ventricles and arteries communicating it are separated by valves.
However, the atria and ventricles are kept separate from each other by the atrioventricular (AV) septum. This means that the blood from the right atrium or ventricle cannot mix with the blood in the left atrium or ventricle. The septum is essential to keep oxygen deficient blood in the right chambers of the heart separate from the oxygen rich blood in the left chambers. In certain types of congenital heart defects, the septum is compromised thereby allowing for a mixing of the blood.
continue reading Left-to-Right Cardiac Shunts (Heart) Types and Symptoms
The terms congenital and acquired are frequently used in medicine to describe a disorder, disease or defect that is either present from birth (congenital) or develops during the course of life (acquired). Congenital defects stem from fetal development but is often only obvious after birth once the baby’s body has to sustain life independent of the mother. However, with modern investigative techniques, many congenital disorders can be detected during fetal life and the appropriate measures taken prior to birth in certain cases. Congenital diseases or defects can affect any part of the body or organ and the heart and great blood vessels are no exception. These diseases and defects can be life-threatening and require intervention in fetal life or immediately after birth while in some cases it may only manifest later in life or adulthood.
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