Science tells us the body of human being is formed by the union of two microscopic structures-the sperm (the male gamete) and the ovum(the female gamete). Sperms are produced in the genital system of the male parent and when man and woman unite, one sperm only unites with the ovum in the body of the female parent. The union between them results in a single cell called zygote . Zygote develops in size in the womb of the mother. This single cell divides itself giving birth to various complex organs. The child at the time of birth is only a mass of innumerable cells arranged into various groups (tissues).
Human body consists of five main types of tissues the epithelial tissue, the connective tissue, muscles, nerves and bones. The epithelial tissue is the inner as well as the outer surface of various organs and glands in the body and protects them. Various secretions in the body like the saliva, digestive juices, and hormones of the endocrine glands are supposed to be produced in the epithelial tissue. The connective tissue fills the gaps between other tissues. It contains stored fat and gives support to various organs. The storage of fat provides energy at the time when the intake of food is reduced or stopped. It is due to this that we can live without food for some weeks. Muscles, about 500 in number, give shape to the body and help in performing various movements. The strength of the body depends upon their development and that is why a strong person has well developed muscles while a weak one has poorly developed ones.
The muscles are of three types- the skeletal, the smooth and heart muscle. The skeletal muscles(or voluntary one) are attached to the bony framework. The smooth muscles are the walls of the hollow visceral organs like the stomach, the bladder, the intestines, etc. and the blood vessels and lungs. These muscles cannot be contracted voluntarily, and are thus called involuntary muscles. The heart muscles(cardiac muscle) are composed of a special kind of strong fibers as heart is the only organ which never stops working from birth to death.
The nervous system tissue performs the function of conducting stimuli from various body parts to the brain and impulses in the reverse direction. Those which carry the stimuli caused by pain, pressure, temperature, etc. towards the spinal cord or brain are called afferent or sensory nerves, while those carrying impulses from the spinal cord or the brain to some muscle or organ, are called efferent or motor nerves.
Bones give shape to body
The bones, more than 200, shape the body. The framework formed by them is known as skeleton. Without them, the body would have been a mere mass of the tissue. They are there to protect delicate parts of the body and make its movement possible. They may be either hard or soft. The soft ones are called cartilage . The nasal septum which divides the nose into tow nostrils, the external ears, the end portions of the ribs and chest bone, are some of the examples of cartilage which makes bending or extension of those parts possible.
The backbone is not a single piece, but is composed of a chain of different pieces called the vertebrae . Vertebral column has 33 vertebrae. The first seven are called cervical because they are in the neck. The next 12 are dorsal. Then 5 are lumbar. Below these are 5 sacrum and the last is coccyx formed by 4 vertebrae. Through the hollow of the vertebrae column passes the spinal cord.
That is why; it is possible for human beings to bend the back forward or backward and to the sides. The large bones are hollow from inside. That has two advantages, namely, first, that increase the strength of the bones , and secondly, it reduces their weight.
The bones of the upper and lower limbs are connected to the trunk at the shoulder and at the pelvis. The upper limb has arms, forearm and heads and lower limb has thighs, legs and feet.
Cell, the smallest but the basic unit of our body, has a nucleus and jilly-li9ke cytoplasm. This very nucleus is responsible for hereditary qualities in man.
A cell has a life common with the whole body and also an individual life. It is the unit of which the body is made up. The cell gets wear and tear while one works and is repaired by rest and by nourishment through food and drink and oxygen. A drop of blood, it is said, has about 5,000,000 cells. They are made up of protoplasm.
Blood constantly supplies oxygen and essential nutrients to the cells and carries away waste products.
The various functions in the human body can well be compared to those being carried out in a complicated machine. Rather, the human machine is very much more complicated than the machines we know of or work on because the former consists of physical as well as physiological factors. For keeping the body in perfect working order, so many functions have to go on hand in hand.
A group of organs in the body is busy acquiring food, its digestion, assimilation and utilization in the body; another group has the duty to supply nutrients to every part of the body and collect waste materials from all over. Yet a third group is engaged in throwing out of the waste form the body. A fourth group of organs obtains oxygen and supplies it to every tissue and organ. All these functions are helped by a fifth group of organs called the endocrine glands . Yet an overall control of all the functions going on in the human body in co-operation with one another is the business of a separate group of organs. These various groups are the digestive, circulatory, excretory, respiratory, endocrine, and the nervous systems. Herein in brief is the working of these systems to understand the influence of yogic exercises on human organism.
Digestive system
Mouth, pharynx, food pipe, stomach, duodenum, small and large intestines are parts of this system. The human body needs carbohydrates, proteins, fats, mineral salts and vitamins to get energy and get going. Carbohydrates we get from cereals, potatoes and sugar. Proteins are provided in ample quantity by pulses, dried nuts, eggs, meat, fish, milk etc. Meat, eggs, fish give fat to the body. Minerals like calcium, magnesium, phosphorus, sodium, iodine, etc are already present in human body. And vitamins are obtained from fruits, vegetables ,milk etc.
Besides these, the human body needs water to maintain temperature at normal state .Saliva secreted by salivary glands, blood, pancreatic and bile juices provide ample quantity of water to the body.
When one starts eating, teeth cut food into pieces into finer form and are moistened by saliva so that it goes down the throat. The food then passes through the pharynx to the stomach where it remains for about two hours and is processed by digestive juices secreted by stomach walls. Then it passes to duodenum. Those juices break down fats, proteins and carbohydrates and they get assimilated in constituents and the remaining part goes to large intestine assimilated part of food is stored in liver and passed on to various organs through blood.
Circulatory system.
This system includes heart (which pumps the blood to variou
s parts) and blood vessels (which carry the blood from heart and back to it again). The heart is the only organ which goes on functioning incessantly from birth to death/ It has four compartments. The upper right compartment receives impure blood from the body and sends for purification to the lungs. The purified blood from the lungs goes to the upper left compartment and thence to the lower left one,. From where it is pumped to all parts of the body through arteries, their branches and sub branches. These sub-branches divide further into capillaries which are very thin walled. The capillaries ramify into various muscles, organs and tissues. Due to the thinness of their walls, the capillaries allow the nutrients and oxygen in the blood to come out of them, and be supplied to the tissues. In return, the carbon dioxide and other waste materials from the tissues diffuse into capillaries. Minute sub-branches of veins and is ultimately returned to the heart. The veins have to raise the blood from the lower extremities, pelvic region, trunk and abdomen against the force of gravity. This is done with the help of valves situated in the veins.
Human blood has nearly 90 percent water, in which red blood corpuscles,, the white blood cells , and the blood platelets float. The R.B.C.s contains scarlet colored substance hemoglobin which carries oxygen. The W.B.C.s acts an s defense force. They fight foreign cells such as bacteria and other microorganisms which if allowed to infest the body can cause many diseases. The blood platelets help in the coagulation of blood, when it comes out of the blood vessels due to cuts and wounds. The circulatory system thus supplies nutrients to various parts of the body and collects waste materials from them, maintains body temperature at the normal level, and supplies oxygen to every part and collects carbon dioxide.
Respiratory system
This system starts from the nose and is composed of the larynx the windpipe (trachea), its two branches (called bronchi ) and the lungs. Its function is to make available oxygen to the body. Life can not go on without biochemical processes which in turn, cannot go on without energy. This energy is received from the food we eat, especially the carbohydrates, fats, and proteins.
The end products of these constituents supplied to each tissue to blood. The energy stored in these products can be used for purpose of life activity of any tissue but only through oxidation. In this process oxygen combines with the substance containing energy, and releases energy along with water vapor and carbon dioxide. This process has to go on continually in every living tissue.
Thus it is clear hat we cannot live without oxygen for more than a few minutes. The carbon dioxide produced in the process of oxidation is poisonous gas and must be removed from the body as quickly as possible It is collected in the blood flowing in the capillaries.
Co2 removal: we inhale air into the body through the nose. It goes to the larynx and then to the windpipe. The windpipe is divided into two branches, one of which goes to the left lung, and the other to the right one. The branches get further divided in the lungs. At the ends of the minute sub-branches are borne the air sacks or cells (alveoli) which are surrounded by capillaries, through which the blood flows from the heart to the lungs, and back again to the heart. The wall of the air sacks is absorbed in blood in the capillaries, and the carbon dioxide and water vapor from the capillaries enters the air sacks.
Lungs expanded and contract during respiration because they are formed of elastic tissues. They are contained in thoracic cavity which is protected on all sides by the ribs. The base if this cavity is made by a dome-shaped band of a muscle called the diaphragm , which plays an important role in respiration. The cavity below the diaphragm is called the abdominal cavity . The cavity accommodates organs like the stomach, duodenum, liver, pancreas, kidneys and intestines.
Thus wee see respiration process consists of inhalation, exhalation and pause. During inhalation the thoracic cavity increases in volume due to an elevation and extension of the ribs, along with a descent of the diaphragm downward. The lungs expand due to this and air rushes in through the nose to fill the vacuum created thus. The lungs then contract automatically after a while due to their elastic recoil expelling some amount of air during exhalation. The is followed by pause, and then another round of inhalation and exhalation takes place. Carbon dioxide and water vapor are got rid of through exhalation.
Excretory system
Kidneys, ureters, bladder, urethra, skin and the large intestines form the excretory system. Kidneys (two in number) are situated in the abdominal cavity of the two sides of the body. They have a network of very minute tube like structures through which blood
Is strained and the unwanted materials like extra amount of water, salts, waste products and other biochemical processes are separated from the blood. Urine which is formed goes down from the kidneys through two tubes called the ureters to the bladder. The urine is passed out of the body through a duct called urethra.
Skin gets rid of excess salts and water in the blood. This is done by minute glands called sweat glands, situated under the skin. When the blood flows through the sweat glands they separate some salts and water along with some other unwanted materials from the blood. The separated fluid comes to the surface in the form of sweat and evaporates. This helps to keep the body temperature normal.
Endocrine system
There are many glands in the body situated at various places. Important among them are the pituitary, the pineal (both in the head), the thyroid, the parathyroid (both in the neck), the thymus(in the thoracic cavity), adrenals, and the sex glands(in the abdominal cavity). These glands do not have any ducts to carry hormones(fluids) and they are also called ductless glands. The hormones produced in the endocrine glands mix directly in the blood flowing through them and are thus made available to different organs and tissues of the body .The hormones(e.g pituitrin, thyroxin, adrenalin) are essential for a proper development of the body and are concerned with the functions like metabolism, and the lungs and so on. Their deficiency as well as excess may lead to many disorders.
Nervous system
This is the main system controlling the various departments of an organized unit. It has two main divisions the central nervous system and the autonomous nervous system . In the former are brain, the medulla, the spinal cord, and the nerves while the latter consists of two chains of knot like structures called ganglia , running along the two sides of the backbone. The automatic nervous system controls the functions of heart, digestive organs, kidneys, endocrine glands etc.
The brain is divided into tow main parts, namely, the large brain (cerebrum) and the small brain (cerebellum). The large brain has various specified areas where specific stimuli (e.g. those concerning sight, smell, hearing, taste and touch, etc.) are received and registered, as well as the individuals response to them are decided. The phenomena o
memory, emotions, consciousness, etc are also controlled by it. The small brain maintains the balance of the body coordinates in the movements of various body parts. Centers which control the action of the heart and the lungs are situated in the medulla.
The spinal cord is a rope-like mass of nervous tissue running from the medulla
downward through the backbone. It has branches on both sides spread all over the body. They send stimuli toward the spinal cord as well as impulses from the brain or the controlling centers to the organs and tissues. They are respectively called the sensory and Motor nerves.