Interdependence means being dependent on each other. In effect, the human body consists of a number of interacting ‘systems’ which are the skeleton and the muscular, nervous, endocrine, circulatory, cardiovascular, respiratory, lymphatic, digestive, urinary, and reproductive systems. Within these systems one also finds organs which work in unison.
The body depends on the skeleton’s rigid framework for support and the internal organs count on it for protection while the muscles use the skeleton for anchorage.
There are three types of muscular movements: skeletal, smooth, and cardiac.
Skeletal movement, initiated by the nervous system, is assured by the muscles attached to the skeleton. The digestive system, the bladder and blood vessels rely on the smooth muscle and the heart functions with the cardiac muscle.
The nervous system
The brain and the spinal cord which comprise the central nervous system (CNS) bank on sense organs (eyes, nose, and ears) to send them signals which they integrate.
Endocrine and circulatory systems
The endocrine system composed of glands (hypothalamus, pituitary, and thyroid), pancreas, kidney, ovaries (female only), testes (male only), adrenal, parathyroid, pineal body and brain secrete hormones directly into the circulatory system to be carried in the bloodstream towards appropriate tissues.
The heart counts on the arteries through which it pumps out the blood in the blood vessels. The lungs supply the blood oxygen and the guts nutrients which the blood carries to all cells in the body.
The cardiovascular system also relies on the blood to remove waste products from the cells; then tissues and the kidneys excrete them as urine and the lungs as carbon dioxide. The heart bets on the veins to carry deoxygenated blood to it. (It is interesting to note that the whole circuit lasts only about one minute.)
Human respiration turns to muscle reflex that makes the diaphragm and internal intercostal muscles to contract. As volume increases in the chest cavity, the air pressure inside it drops. Air then rushes in through the nose, down the trachea, and into the lungs, making the exchange of oxygen and carbon dioxide to take place.
Lymphatic and circulatory systems
Lymph vessels, lymph nodes, and its lymphoid organs (the spleen and the tonsils) remove excess fluid from the body’s tissues and return it to the circulatory system. (Note that this helps to fight infection.)
Digestive and urinary systems
The mouth is the beginning of the digestive tract. As one goes down, one finds the salivary glands, epiglottis, oesophagus, liver, stomach, gall-bladder, pancreas, small intestine, large intestine, appendix, rectum, and the anus.
In the mouth one finds the teeth which take care of biting and chewing and the tongue which shapes food into a readily swallowed bolus.
The windpipe depends on the epiglottis, a flap of cartilage at the root of the tongue, to become depressed during swallowing and cover it.
Apart from the mouth, the digestive tract includes the oesophagus (which links the throat to the stomach), stomach, small and large intestines (the lower parts of the alimentary canal from the end of the stomach to the anus), rectum (the final excretory opening at the end of the alimentary canal).
Through a system of ducts, the digestive tract is connected to the salivary glands (which secrete liquid into the mouth to ensure lubrication, aid chewing and swallowing, and facilitate digestion), the gall bladder (which stores bile after it is secreted by the liver and before it is released into the intestine) and the pancreas (which provides bile and enzymes to aid digestion), and to the liver, which help to metabolize food products into a form that can be stored, for example, as fat and proteins. In the large intestine, undigested food is solidified into faeces which will be excreted via the anus.
The kidneys filter blood to form urine by which waste products will be excreted. Ureters carry the urine to the bladder which stores it for discharge. For this to happen, the bladder contracts, the bladder and urethral outlets (sphincters) relax, and the urine is expelled. (Note that a woman’s bladder is smaller and lower in the pelvis than a man’s, and her urethra is about one-fifth the length of a man’s.
The reproductive organs produce sex cells (ova in the female’s ovaries, spermatozoa in the male’s testes), which ensure fertilization of an ovum through sexual intercourse. Then the uterus (womb) receives the ovum. (This provides a safe environment for the developing foetus during the 9-month gestation period.)
Lesson for humanity
We find that while each of the systems of the body and the various organs have specific roles to play in the body, they don’t work in isolation. When a system or organ finishes its work, it relies on the others to continue from where it left off. This also depends on others to carry on the work. This interdependence helps the body to work in perfect harmony and assure its survival.
Is there a lesson here for families, people, communities, nations, and continents to learn to cooperate with each other for the good of the world? Your answer is as good as mine.