The Human Body System
Presently we need to understand the human Body System whose functioning decides the state of our health. There are seven systems of the body which are given below:-
1. The Digestive System
2. The Excretory System
3.The Respiratory System
4. The Circulatory System
5. The Muscular System
6. The Skeletal System
7.The Nervous System
1. The Digestive System:-
The digestive system is one of the most important parts of the human body system. In this system, we know the food that we take comprises proteins, carbohydrates, Vitamins, Minerals, fats, and oils. Only a part of these substances is useful to the body and the rest, which is indigestible, must be got rid of, the food is chewed by teeth and after getting mixed with is saliva, is swallowed. Saliva is an alkaline fluid that is poured into the mouth from salivary glands. Digestion of food starts in the mouth itself. From the mouth, the food enters into an expanded cavity behind, the Pharynx, which is also common to the air passage at this level. It then passes into the esophagus. Like stomach and intestines, the esophagus is a muscular organ and can force the food along if necessary.
With the help of this muscle, a man can drink even if he is standing on his head. About nine inches long, the esophagus ends in the stomach. It is here that the second stage of digestion takes place.
From this position, the food reaches the stomach which is a hollow muscular organ lined by a glandular mucous membrane which secretes the gastric juice. Gastric juice is made up of hydrochloric acid, salts, pepsin, and water. The stomach mixes the food well by moving it round and round. At this stage, the proteins are changed to a form in which they can pass through the stomach wall and be absorbed readily to nourish the body. Carbohydrates are now acted upon, though not digested completely. Fat and oil are broken up and the oil is set free.
The stomach digestion may take two-three hours. The food then goes to the small intestine which is a long tube which, when uncoiled, may measure about 16 feet. Here we have to consider the action of three different digestive juices, e.g., the pancreatic juice, the bile and the intestinal juice, which is the secretion of the wall of the intestine into the lacteals, and into the blood. The bile and the pancreatic juices are produced by the liver and pancreas respectively.
The liver is the largest organ in the body, which is situated just underneath the diaphragm rather on the right side. Its weight is three to four pounds. There are fine tubes in the liver called bile duct into which the cells of the liver secrete bile, and the bile ducts join together and form Hepatic Duct which carries the bile to the duodenum.
Bile is a yellow fluid, containing mucus, water, and special salts. It acts on the fats and oils and breaks them up into very small drops. The liver is also a storehouse for sugar which it puts in the blood when it is required by the body. About seven inches long, there is another large gland reddish in color known as Pacers. It lies behind the stomach, and a tube form it called the Pancreatic Duct enters the duodenum near to where the bile duct enters. The pancreatic juice act on the protein, the starches, and the fats.
The intestine is an organ of digestion as well as of absorption. The food, now digested, can pass through the walls, of the intestine and is taken into the blood. It is then distributed all over the body. Food remains in the small intestine for about 12 hours and is slowly passed on towards the large intestine.
The large intestine is a 6 feet long tube. It is little concerned with digestion or absorption of food, for more of this has already been done. Food remains here from 24 to 36 hours. Due to the loss of water, the material in the large intestine now hardens as it reaches the rectum. Finally, the indigestible remnant is excreted out.
2. The Excretory System:-
In the human body system is designed to help get rid of the waste matter in the body when all juices have been extracted from the digested food. The Excretory system, there are two kidneys, situated one on each side of the backbone in the small space of the back or loin. It has the renal artery which brings blood to it, and the usual nerves, the lymphatic vessels, and the Urethra, the tube that takes urine from the kidney to the bladder. The bladder is the reservoir for urine.
Urine, a pale yellow fluid, carrying the waste nitrogen from our protein foods and also mineral salts, is secreted by the two kidneys. The kidney may be regarded as a pair of filters, through which about ½ liter of blood circulates every minute. In fact, the whole blood in the body passes down through the kidneys in five to six minutes. Urine is propelled down along the utters from the kidneys to the balder by successive waves of contraction in the muscular walls of these channels.
The bladder is an elastic membranous bag serving as a temporary reservoir of urine, secreted by the kidneys. The normal adult capacity is about a ½ liter. The urine is discharged into the bladder in intermittent jets every 20 seconds or so. The outlet below the bladder is normally closed by a tight ring of muscle called Sphincter. In empty, the bladder contracts and the sphincter relax to allow the efflux of urine.
Another important agent for excretion of the waste material from the body is the skin. It has two layers, the top one called the Epidermis and the inner one called the Dermis or true skin. The latter is richly supplied with blood vessels. The skin is designed to:
(A). Protect the body;
(B). Act as an organ of excretion by means of sweat glands. It thus helps to regulate the temperature of the body; and
(C). to give a sense of touch.
The skin has hair and sense organs. The latter are little lumps in the Dermis which are nerve endings. They report to the nervous system when anything comes into their contact. The skin also has two kinds of glands, the Sebaceous Glands, which secrete an oily substance serving as a lubricant to the skin and the Sweet Glands which make the skin an excretory organ. The function of the latter is to take up a sweat from the blood and pour it out of the skin. Though mostly water, the sweat contains salts, fats and tiny bits of dead scales.
Bowels are the intestines, both large and small which serve to complete the digestion of food and to allow its absorption into the blood-steam. The useless food remains are gradually moved onwards and are hardens in the large intestine wherefrom they are ready to be thrown out. The failure of the bowel function is called constipation.
Lungs comprise two elastic spongy masses, almost filling the chest cavity. These are important agents to cleanse the system of impurity. Lungs throw off carbon dioxide, water and also some organic matter. They are, therefore, organs of excretion in addition to being organs of respiration.
3. The Respiratory System:
The Respiratory system is a part of the human body system. This system comprises of the lungs and the passages leading to them. The purpose of breathing is the entry and exit of air to and from the lungs. In in-breathing, the chest cavity is enlarged and the air enters; in out-breathing, the chest cavity reverses its action and the air is thrown out. The object of breathing is to bring oxygen of the air into contact with the blood with the purpose of giving some oxygen to the blood, and taking of waste products from the blood.
The air, in going to the lungs, has to go through various passages. They are nose or mouth, and the larynx or Voice Box.
We breathe through the nose or mouth. There are two passages leading downwards from the nose and mouth into the body- one takes food and water to the stomach and the other takes air to the lungs.
Larynx or Voice box is commonly known as “Adam’s Apple” and can easily be felt in the throat. It is a cavity holding vocal cords, just at its junction with the pharynx. The vibration of the cords produces vocal sounds. The air passes from the voice box to the lungs by means of the windpipe which is about four inches long and one inch wide. It has rings of gristles which keep it open. It has rings of gristles which keep it open. The windpipe at the lower end is divided into two branches that go both the lungs.
The functioning of the lungs has already been described while discussing the Excretory System. Here the functioning of lungs as the respiratory organ is slightly more complicated. In the lungs, the air gets very close to the blood that comes from the muscles by way of the heart. The impure blood, dark red in color, has too much carbon dioxide in it. This blood comes from the tissues which have taken the oxygen from it but have loaded it with carbon dioxide. In the tissues, oxygen is used every minute to burn up food material, resulting in the production of a considerable quantity of carbon dioxide.
The lung’s function is to reverse this state of affairs, i.e., restoring its oxygen quota and expelling the excess carbon dioxide. Thus the venous blood is rendered arterial in its passage through the lung capillaries. It goes back to the heart and is ready to do its work again. The new oxygen, taken by the blood all over the body, is picked up again by its muscles which need it for their normal functioning.
4. The Circulatory System:-
In the human body system, the Circulatory system work to comprises of the blood and heart and their functions. The blood is continuously propelled by the contraction of the heart and is driven into the arteries. The arteries are elastic tubes which by their recoil help the distribution of the blood to all parts.
The blood is a clear fluid comprising innumerable solid bodies called corpuscles. The corpuscles are of two kinds, red and white and are cellular shaped. The red corpuscles carry Hemoglobin which constitutes protein and a little iron. When combined with oxygen, hemoglobin forms a bright red substance and with carbon dioxide, it forms a bluish compound. The white corpuscles are living organism, small jelly-like creatures each with a nucleus. They are of great importance as they eat up the disease germs that enter the body. They are capable of independent movement in the bloodstream and within the tissue and can swallow up dead bacteria and foreign particles.
The main function of blood is the following:
(a). It carries oxygen to every part of the body that requires it.
(b). It carries impurities from all parts of the body to the excretory organs namely the lungs, the kidneys, and the skin.
(c ). It carries food from the digestive system to all tissues.
(d). It carries heat to all parts of the body.
The heart is a hollow, muscular and somewhat conical four-chambered force pump enclosed in a fibrous bag. It is situated in the chest between the lungs and weighs about 300gms. The heart is divided into two parts by a wall running from top to bottom with no direct connection between the parts. These parts are themselves divided into two parts, upper and lower but have valves between them. The upper portions are called Auricles and the lower one’s Ventricles.
The motive power of the circulation is the pumping action of the heart which acts as a boosting mechanism set in the middle of a pipeline. When the blood reaches the tissues it loses all its oxygen and is loaded with waste material from the tissues. The impure blood reaches the heart by means of capillaries and veins, with the beat of the heart, it enters into the Right Auricle and then to the Right Ventricle from where it is taken b the pulmonary Artery to the lungs. In the lung capillaries, the blood comes into contact with oxygen and it purifies.
The purified blood is now brought back to the heart by means of pulmonary Vein. It now enters the left Auricle and when auricles are squeezed during the heart-beat, the blood passes to the Left Ventricle and then commences its journey again to all parts of the body. Thus with the contraction of the right and left auricles, the venous blood from the body and aerated blood from the lungs is pumped into their respective ventricles. And when the right and left ventricles contract, venous blood is pumped into the lungs and the aerated blood into the aerated blood into the main vessels. These rhythmic contractions and dilatations, followed by an equivalent pause are called pulse or heartbeat.
5. The Muscular System:-
Muscles are attached to the bones and consist of bundles of fleshy fibers capable of contraction of shortening when required. Such contractions help the various limbs of the body to move. The human body system muscles are of two kinds namely the voluntary muscles whose movements are controlled by human will and the involuntary muscles which perform their function without any conscious effort of the will. These include the heart, the muscles of the stomach and those of the intestines. Their movements are rhythmic and we are not conscious of their actions.
6. The Skeletal System:-
The bony skeleton supporting the human body system is constructed to strengthen the muscles which produce movement in the body to give shape. The forelimbs of the human body are supporting by bones forming a shoulder girdle and similarly the leg bones forming a shoulder girdle and similarly, the leg bones are connected to others forming a pelvic girdle. Ribs connected to the backbone serve to protect certain internal organs, including the heart and the lungs. Man’s structural superiority over other animals is due to the straight femur or thigh bone and his erect poies of the head.
The above features enable the man to walk in an erect position so that his hands are free to perform other functions. These structural advantages and the formation of his skull and lower jaw are responsible for an increase in brain power and intelligence in man, compared with the other animals.
The human body system consists of 206 bones of various sizes. The bones are composed of cells, which are softer in early childhood than in adult life. Where bones meet there is a joint, which may simply be an immovable joint as that of the knee. The movable joints are necessary for the motion of the human body.
7. The Nervous System:-
The Nervous system is the most important system since it commands the rest of the body what to do and how to work together. While the central Nervous system resides in the skull and the spine, the nerves are spared all over the human body system. The nervous system of man is a network pervading the whole body, having a two-way connection with the central control and enabling the individual to give a coordinated response to any stimulus from outside. Thus nerves that carry the messages to the muscles with orders to perform a particular action are called Motor Nerves.
The brain is the chief centre of the nervous system and is contained within the skull. The brain substance consists of grey and white matter, the grey matter forming a thin, superficial layer. It consists of three parts:
- The cerebrum or bigger brain, which govern our consciousness, thought emotions, will, sight, hearing, sensation of pain and memory through the grey matter,
- The cerebellum or the smaller brain is connected with the coordination of the action, nervous and muscular, by which the movement of the body is carried on.
- The Medulla Oblongata houses the centers of nervous tissue connected with reflex action consisting of movements that take place automatically such as breathing and heart activity.
The spinal cord consists mostly of nerves. This is like a continuation of the medulla and runs down the back, surrounded by the bony arch of the spinal column. The organ is capable of making simple decisions, called the reflex action.
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