Interrelationship Between Various Systems of Body

By Mr AK Shyam
The Human body is composed of eleven separate BUT interconnected systems –
Skeletal, muscular, circulatory, respiratory, digestive, excretory, nervous, integumentary, immune, endocrine and reproductive.  These systems work in tandem to maintain health.

Skeletal system

Skeletal system provides structure to the human body, stores minerals, produces blood cells and protects delicate organs.
It is made up of 206 bones connected with ligaments, muscles and tendons with softer cushion (cartilage).  Body movements are controlled by muscular system, while the stimulation of the system is by nervous system. 

Respiratory and circulatory systems deliver nutrients and oxygen to cells as well as remove waste products and aids immune system through circulation of white blood cells.  Immune system comprising of lymph organs (Spleen and thymus and the skin) protects body against pathogens.

Blood Circulation, Respiration

The Circulatory and Respiratory systems are closely interconnected as the latter firstly, brings fresh oxygen into the body through alveoli and secondly, removes carbon dioxide and other waste gases.  The excretory system eliminates both solid and liquid wastes including gaseous products.  This is affected through special tissues of the large intestine, bladder, kidneys, rectum, lungs and skin.

Digestive and Nervous Systems

The physical and chemical breakdown of food that we eat is through digestive system – mouth, teeth and salivary glands then pass through esophagus to stomach and small intestine for digestion.  Liver, pancreas and large intestine are also involved through digestive enzyme and bile and processing nutrients.

Messages to and from Brain is through neurons of the nervous system.  Nervous system controls body functions through electrochemical signals – Endocrine system acts as communication network using hormones as chemical messengers through blood stream.  Hormones have specific target organs either to start or stop performance of a specific function.

Finally, reproductive system is responsible for reproductive hormones and progeny continuation.

Statistics Of Physiology

We usually take 15 breaths in 60 seconds; 70 heart  beats;
brain conducts six million chemical reactions;
bone marrow produces 180 million blood cells and
skin sheds 10,000 particles of skin. 
The biological, physical, mental and emotional health of a human being is a result of – hundred trillion cells;
60 miles of blood vessels,
a 3 pound brain with 50-100 billion nerve cells;
2.5 billion heart beats in a life of 75 years. 

Skeletal System Muscular System Nervous System Respiratory System Digestive System Circulatory System Reproductive System
Gives body its basic framework Moves skeleton, maintain posture through steady contraction Brain Nose Mouth-tongue, teeth; Pharynx Diaphragm Heart Female: Vagina; Cervix; Ovary; Uterus
206 bones produce blood cells, store important minerals AND generate heat through cell metabolism Spinal Cord Lungs Stomach Spleen Lungs Male:Penis; Testis; epididymis Vas deferens
AND release hormones necessary for life   Meninges Pharynx Liver-Gallbladder Brain  
    Dura mater Bronchi Pancreas Small intestine Kidneys  
  1. Do we need a redesign of the body?

It is now clear that our body is a mix of interdependent systems and organized biochemical reactions.  Although considerable modifications occurred since evolution of the Homosapiens (Humans), the current technological and social change have taken toll on our life style and exposed considerable frailties (moral weakness).

Biologically, every new progeny is considered to be a gene combination of the parents.  When we consider this over the long period since human evolution, it is indeed pretty difficult to comprehend the genetic modification associated with the lifestyle of each generation.  Although we cannot dig too deep, we can at least take the modern era which seems entirely different from the one that we, the current senior citizens enjoyed.  Understandably, we see quite a difference leading to greater vulnerability due to the difference in our lifestyles.   That leaves us with the question – ‘Do we need a redesign of our body?’.

  • Basic understanding of the physiology

Despite the structure of human being the same, the physiology seems to be entirely different from person to person – some seem weak, others appear strong which is attributed to the immune system and understandably, the former fall prey to a number of complaints pretty quickly.

Have we ever cared about these intricate systems of the body and their co-ordination in keeping our body fit and healthy?

I am sure the answer is a big NO.  Because, we take it for granted and carry on until something goes wrong and that is when we, immediately rush to the Doctor and we follow his instructions very obediently.  But, have we ever thought of understanding the basics of our system so that we can if not abuse, take precaution in maintaining the balance of body systems.  Although “Ignorance is a bliss” sometimes, it is not so always.

Then, what is it that makes our body vulnerable to disease? If only our immune system recognizes and attacks million foreign elements, we perhaps could be free from it, right.  The logical question is if one lives hundred years, why not two hundred years?

Though there are 11 different systems that are responsible for the humans to survive, I wish to consider just three of them namely, Digestive, circulatory and nervous system for this discussion and attempt to resolve the basic question that bothers many of us.

  • Integration among Digestive, circulatory and Nervous systems:

Many of us are aware of the quote, “you are what you eat’.  When we look at this seriously, it reflects the kind of food we eat as they are the primary drivers of energy.  As vegetarians, we consume a lot of vegetables and fruits often and they being natural provide the necessary ingredients to the body to drive through the day. The quality of ingredients depends on the type of vegetables as each of them supplies different elements to our body.   We also hear about sattvic diet that contain the quality (guna) sattva, further,  foods that decrease the energy of the body are considered tamasic, while those that increase the energy of the body are considered rajasic.  Rajasic food denotes activity, decision-making, energy that is required for tasks and mental robustness. The foods in this category activate the various functions of the body and energizes almost all the systems, specially, nervous system.  In addition to vegetables (sweet potato, sprouts, lettuce etc. ) and fruits (mango, pomegranate, coconut etc.)  grains, beans and dairy belong to Sattvic category.  Sour apple, apple, banana, guava etc and potato, cauliflower, spinach, tamarind are a few examples of rajasic category.  Sattvic foods help the mind become clear and stay focused,  Rajasic foods generate more fire, outward motion, creativity, aggression, and passion and  Tamasic foods increase inner darkness and confusion. They slow us down, depress us and enhance inertia.

The digestion time varies not only between individuals but, even between men and women.  It normally takes 6-8 hours for the food to pass through stomach, small intestine before entering into large intestine (Colon) where further digestion takes place along with water absorption before the undigested food is eliminated. The food gets ground and churned in the stomach to small particles; then processed by different chemicals that are designed for specific components.  Proteins, fats and Sugars (carbohydrates) are digested by pancreatic enzymes.  This powerful digestive system is aided by liver (bile juice) and pancreas (Insulin and Glucagon) which release powerful enzymes.  The food broken into small molecules are easy to be absorbed by the body for energy, growth, repair and regulation.

Initially, mouth composed of tongue, teeth and palate facilitate food to be broken into small pieces which are easy to swallow and ready for enzyme action lower down.  Food then passes through Esophagus which is 25 cm long and the food muscles push the food into the stomach. Interestingly, there is ONE way traffic of food into the stomach and by some means do not allow the reverse flow. When the muscle loses its power that may lead to several stomach problems.  Stomach is literally a mixer.  Most of the digestive process is completed in the small intestine.  The small intestine (5 meters in length and 1 inch dia) consists of Villi and microvilli are super effective in absorbing the digestive food.   The undigested food then passes into the large intestine (1.5 m) comprising of caecum, Ascending/Transverse and descending colon. The food then passes into sigmod colon, rectum and finally anal canal.  Water is absorbed in the large intestine and several gut bacteria play an important role in producing propionate and bytyrate and vitamin K for their nourishment.

What has been described above is just an outline of what goes on in the digestive system WHICH is the primary source of energy to the human body.  What has not been included is the chemistry part of the digestive process.  But, it is just enough to conclude that this energy producing system is the precursor for many other functions that the body performs in the life of human beings.

They not only provide the right ingredients to the circulatory systems but also activate the nervous system.   Thus, the nutritional essences of the food we eat are extracted into the circulatory system.  Once this is completed, the unwanted waste including toxins are emptied into the large intestine and the urinary system.

Even in this system of digestion process, opening of larynx is pretty vital and it is open when we eat and closes once we finish eating.  This is indeed a wonderful co-ordination between digestive and nervous system. There are many such trivial sensors in our body without which we cannot function as well as we do.

  • Chemistry of the digestive system

The entire process of digestion although looks pretty simple, it is not so.  The system is supported by digestive organs – the liver and pancreas.  The process from the beginning to the end involves a number of enzymes and Chemicals.  Firstly, mouth- Saliva contains Amylase and lipase – Starch into simple sugars and Fats into simple lipids.   Taste buds provide information on taste – Bitter, sour, salt and sweet.  Esophagus muscular structure is such that it is constricted towards the stomach facilitating one way traffic.  Stomach is connected to Esophagus at the upper end and Duodenum at the lower end.  Stomach releases Hydrochloric acid, Sodium chloride and enzyme pepsinogen.  As they are powerful acids, they may damage stomach wall which is prevented by Mucus secreted by gastric lands which secretes bicarbonate to counter Hydrochloric acid.  Pylorus at the beginning of the duodenum restricts food until one hour of eating.  It is now that Liver, pancreas gall bladder, small intestine wall get into action.   Bile secretions – water, bile salts, bile pigments ad mucus are emptied into duodenum.  Gall bladder is responsible for fat digestion.  Pancreas has both exocrine and endocrine.  Exocrine secretes Chymotrypsinogen, Trypsinogen, Amylase and Lipase.  Chymotrypsin and Trypsin are the active parts of the former two which digests protein; Amylase digest carbohydrates and Lipase digests fats.  Proteins, carbohydrates and fats are digested slowly in the small intestine. There are brush border enzymes composed of Dextrinase, Glocoamylase, Maltase, Sucrase and Lactase.

  • Interrelationships between Respiratory, circulatory and Nervous system.

While I have dealt the Digestive system separately, it is not to be treated separately while considering the overall functioning of the human body.  The digestive system which is the precursor of energy to the body is ably supported by the other three closely related systems.  Respiratory system, we know is responsible for supply of oxygen and expelling carbon dioxide.  It also works with circulatory system to pump oxygen-rich blood to all cells in the body.  The figures speak the truth – beats 1600-24000 time a day and exchanges 110 litres of air.  The system is quite complex like the digestive – the vocal cords divides the upper respiratory tract (nose & Nasal cavity, Pharynx and Larynx –above vocal cords) and lower respiratory tract (Larynx – below the vocal cords, Trachea, Bronchi, Bronchioles and Alveoli).  Majority of the gas exchange happens at the Alveoli.

This has a close interaction with the circulatory system – Right and Left pulmonary arteries pump deoxygenated blood to the lungs.  About 5 litres of blood is pumped into 250-399 million alveoli per minute.  The entire process of deoxygenated blood getting converted to oxygenated blood takes fraction of a second.

For both the above systems to function properly nervous system is very important – it exerts profound influence on digestive processes – motility, ion transport associated with secretion and absorption and gastrointestinal blood flow.  The enteric nervous system along with sympathetic and parasympathetic nervous systems constitutes autonomic nervous system.  Digestive processes provide the building blocks for some neurotransmitters – autonomic nervous system controls the tone of the digestive tract. The brain controls drinking and feeding behavior. … The digestive system sends sensory information to the brain.

  • Natural system and Health care

We pass through many stages in our life starting with childhood to old age.  During this journey, we unknowingly abuse the body to a great extent as we take everything for granted.  In our pursuit of material assets, we often tend to neglect our wellbeing.   We all have gone through the minor to major setbacks of this wonderful human body.  In order to balance, we had no option but to bank on the available options in the form of Ayurveda, Homeopathy and also to a great extent Allopathy.

In this effort to maintain our health, we feed many foreign elements into this natural system – not realizing either the short or long term impact.   It is this lack of understanding that lands us into more serious problems as the treatment we receive is not holistic – doctors fail to treat any complaint holistically as it is mostly focused on the immediate complaint on hand.

Imagine a system where these foreign elements with their chemistry supersede the natural chemistry of the body, the problem becomes much more complex and hits upon a the body system.  This leads to a chain of reaction and imbalance sets in.  I was trying to correlate the repercussion of ‘Lower Hemoglobin” level in the human body.   I soon realized that this has bearing on the Creatinine level which is synthesized in the Kidney/Liver/Pancreas and transported in blood to other organs (Brain and muscle). Phosphocreatine of the muscle generates creatinine through muscle contraction.  Higher creatinine level has a direct bearing on the kidney functioning and leads to serious problem of a regular dialysis. 

Unfortunately, no one understands the reason for lower hemoglobin level and they treat the subject as an experimental material – trying all sorts of things.  This is just an example.  But, there are many more serious problems that we see around for which the doctors have no answer as they don’t look at it holistically.


Having understood the Human systems and their close co-ordination, is it not time for us to attempt an understanding the basics of this so that we could avoid feeding foreign elements into the wonderful natural system at least to the extent possible.
A K Shyam 373, Canara Bank Layout I Main, 1st Cross, Vidyaranyapura Post, Bengaluru-560097 [email protected]

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