Blood pressure

Blood pressure

The heart is a vital organ that pumps blood to different parts of the body. The outflow of the blood takes place when the heart's left ventricle contracts. Then blood is forced into the arteries which expand to receive blood. These arteries have a muscular lining which resists this pressure. Thus blood is squeezed out of them into the smaller vessels of the body. By blood pressure we mean the amount of pressure that blood exerts on the walls of the arteries. The amount of pressure depends upon the strength of the heart muscle, the amount of blood in the circulatory system and the condition of the arteries. There are two kinds of pressures - systolic and diastolic. Systolic is the maximum pressure that occurs when the left ventricle contracts. Diastolic is the minimum pressure that occurs just before the heartbeat which follows. When a doctor measures blood, pressure, he uses an instrument in which a column of mercury rises or falls under the pressure. It is marked in millimeters. The average systolic pressure in a young man is about 120 mm of mercury and the diastolic pressure is about 80. These figures are usually stated as 120/80 or 120 over 80.

Blood pressure usually rises with age because the arteries become less flexible. Anxiety or exercise may also cause pressure to rise temporarily. It is also increased by a number of diseases. A person is said to have high blood pressure or hypertension if it exceeds the figure of 100 plus his age or if the diastolic pressure exceeds 100. High blood pressure can cause heart failure, apoplexy, or kidney diseases. It· may also burst a blood vessel in the eye or the brain, thus causing blindness or a hae­morrhage. Symptoms of high blood pres­sure are headaches, hot flashes and anger. Abnormally low blood pressure occurs when a person has an heart attack or loses large amount of blood because of some injury etc. When the blood pressure falls considerably, the oxygen supply to the brain and other parts also gets reduced. This can cause death. Physicians use drugs which contract the muscular walls of the blood vessels' to raise the blood pressure. Abnormal high blood pressure may be due to the constriction of arteries or due to damage to one or both kidneys. Excessive weight and lack of exercise can also contribute to hypertension. Temporary high blood pressure can be due to excitement or emotional stresses.

Cholesterol

Cholesterol

Cholesterol is an organic compound belonging to the steroid family and occurring either in a free state or as esters of fatty acid in practically all animal tissues. The molecular formula for cholesterol is C₂₇H₄₆0. In a normal man it is about 0.3 percent of his average weight. It is the starting material from which the body produces bile acids, steroid hormones and pro-vitamin substances in the body. It is used by our body to help the digestive system as well.

Cholesterol was discovered in 1812. Its name arises from its occurrences in gallstones derived from the Greek word chole-stereos-al meaning bile-solid. The synthesis of cholesterol occurs in various tissues and organs particularly, the brain, liver and arteries.

The increase in its quantity beyond a certain level can be harmful for our body. Excess of fat and cholesterol get deposited in the walls of arteries causing blockage and hardness thus obstructing the free flow of blood. Due to this, quantity of blood flowing in the arteries decreases and consequently the oxygen supply to vital parts of our body is also decreased. This condition is medically termed as arteriosclerosis. Small blood clots that would normally pass through blood vessels may get trapped by high cholesterol deposits.

We know that coronary arteries play a vital role for the heart to function. They provide oxygen and carry blood to the heart. If a coronary artery gets blocked that particular part of the heart may stop functioning leading to a major heart attack which can even prove fatal.

Cholesterol in blood can be controlled by a regulated diet. A high concentration of cholesterol is present in the foods of animal origin like meat, egg, butter etc. Doctors advise to avoid high-cholesterol foods by substituting unsaturated foods like fruits, vegetables, cereals and so on.

Lowering cholesterol levels in the blood can help to reduce the risk of heart attacks. Several other measures can be taken to maintain the desirable cholesterol level. This includes giving up smoking, regular exercises, avoidence of overeating and fatty substances.

Teeth

Teeth

The teeth are hard, bonelike structures found in the mouths of most vertebrates. They are made to cut, tear or crush food so that it can be swallowed. Cutting teeth are called incisors, tearing teeth are called canines and the crushing teeth are called pre-molars and. molars. Meat-eating animals have large canines for tearing flesh. Plant-eaters have sharp incisors and large molars for snapping off and grinding stringy stalks. Humans have all the three kinds of teeth because we eat all kinds of food.

Human beings get two sets of teeth during their life time - primary teeth and permanent teeth. Primary teeth are also called deciduous or milk teeth. There are 10 on top and 10 on the bottom. As one grows, these teeth become loose and fall out. They are replaced by a permanent set of 32 teeth. There are three layers in a tooth. At the centre is a space full of nerves and blood vessels called 'pulp cavity'. Around it there is a bony wall of 'dentine'. On top of it is a layer of hard, shiny 'enamel'. There are two parts of a tooth. The part of the tooth that you can see above the gum is called the 'crown'. Below the gum is the root of the tooth. The root is fixed in the jawbone by a layer of bone called cement.

Frequent and excess eating of sugar and sweets is not conducive for healthy teeth. Bits of sugar stay around your teeth, no matter how much you chew. Bacteria are always present in your mouth, and they act on the sugar to produce an acid. This acid attacks the enamel and in time makes cavities in your teeth. Very cold and hot drinks are also harmful for teeth. We get tooth decay if we allow too much damage to the tooth by eating-sweets in excess and by not brushing our teeth regularly.

Dream

Dream

All our dreams have something to do with our emotions, fears, longings, wishes, needs and memories. But something on the 'outside' may influence what we dream. If a person is hungry, tired, or cold, his dreams may well include these feelings. If the covers have slipped off your bed, you may dream you are on an iceberg. There are people called psychoanalysts who have made a special study of why people dream. They believe that dreams are expressions of wishes that didn't come true. In other words, a dream is a way of having your wish fulfilled. During sleep, according to this theory, our inhibitions are also asleep.

Growing

Growing

The average baby is about one foot, eight inches long at birth. Over the next twenty years, man triples the length of the body he was born with and reaches an average height of about five feet, eight inches. But why doesn't he just keep on growing and growing? In the body there is a system of glands called the endocrine glands which control our growth. The endocrine glands are: the thyroid in the neck, the pituitary attached to the brain, the thymus which is in the chest and the sex glands. The pituitary gland is the one that stimulates our bones to grow. If this works too hard our arms and legs would grow too long and our hands and feet too big. If the gland doesn't work hard enough, we would end up as midgets.

We continue to grow, but only slightly, after the age of 25, and we reach our maximum height at about the age of 35 or 40. After that, we shrink about half an inch every ten years. The reason for this is the drying-up of the cartilages in our joints and in the spinal column as we get older.

Cells

Cells

Apart from water the rest of the body is built from a huge number of complicated chemicals. These chemicals, together with water, are assembled into tiny building blocks called cells. Each cell is self-contained and has a particular function of the body. There are more than 50,000 billion cells in our body. The shape and appearance of a cell depends on what type of job it has to do. Nerve cells are long and thread – like and can carry messages around the body along the nervous system. Red blood cells are so tiny that they can only be seen under a microscope and are like flattened discs.

The sole function of the blood cell is to combine with oxygen in the lungs and to exchange the oxygen for carbon dioxide in the tissues. White blood cells are shapeless so they can squeeze between other cells and attack invaders such as bacteria. Other cells control the production of essential substances called proteins.