Human body
Human body.
Analysis of the human body.
Cell.
Human body as a system.
The nervous system.
Sensory organs.
Respiratory system.
Cardio vascular system.
Lymphatic system.
Digestive system.
Endocrine system.
Urinary system.
Reproductive system.
Musculoskeletal system.
Skeletal system.
Muscles.
Skin.
Human body as a system.
Human Body.
The human body is possibly the greatest creation of nature.
Evolution, after experimenting for billions of years,
seems to have, incorporated the best of design features in the human body.
We can understand, the human body, in two different ways.
We can break it down, into smaller and smaller parts,
and understand it in an analytic way.
We can also understand it as a whole system,
comprising of different functional subsystems.
We will introduce the human body, using the analytic approach.
We will try to understand it, using the systemic approach.
The focus of this module, will be the systemic approach.
Analysis of the Human body.
If we break down, the human body, into smaller and smaller parts,
we will ultimately arrive at the cell.
The Human body, basically comprises of a large number of cells.
There are many trillions of cells in the human body.
Cells combine together to form tissues.
A tissue is an organised collection, of similar cells,
that carries out a specific function.
For example, the tissue, that joins the muscle, to the bone,
is called as a tendon.
The tendon performs the function, of anchoring the muscle to the bone.
Tissues combine together to form an organ.
An organ is a functionally specialised part of a human body.
For example, the heart is a specialised organ, whose function,
is to pump, and circulate blood, in the body.
Some of the organs in the human body, are:
Brain.
Nose.
Ear.
Tongue.
Heart.
Lungs.
Spine.
Hands.
Stomach.
Intestines.
Kidneys.
Liver.
Glands.
Bladder.
Reproductive organs.
Legs.
Skin.
Knowing all the parts,and its location in the body,
helps us to understand, the physical layout of the body.
It is like knowing the map of the body.
This is very useful, for certain purposes.
Cell.
The Cell is the basic unit of the body.
The design of the human cell,
is very similar to the design of animal cells.
It even has some similarities, to plant cells.
When nature designed the cell,
it retained the basic design of the cell, in many species.
Though the basic design of the human cell, is the same,
there are specialised variants, in different parts of the body.
These variants, are just specialists, of the same basic cell.
For example, we have specialised muscle cells, bone cells,
blood cells, nerve cells, skin cells, etc.
We will summarise, the parts and functions,
of the basic design of the cell.
Most of this, will be common to, all type of specialist cells.
A cell is a living unit.
It requires energy to live.
It generates this energy using food and oxygen.
In the process it creates waste, and carbon dioxide.
The food and oxygen, has to be supplied to the cell.
The waste and carbon dioxide, has to be collected and carried away.
The cell is enclosed in a cell membrane.
The cell membrane acts like a skin,
and protects the internal organs of the cell.
The membrane, selectively allows, certain substances,
like food and oxygen to enter the cell.
It selectively allows, certain substances,
like waste and carbon dioxide to exit the cell.
The control centre of the cell is the nucleus.
The nucleus contains the DNA.
DNA comprises of 23 pairs, of chromosomes.
The nucleus directs all activities of the cell.
It is something like a local headquarters.
It is also involved in cell division and growth.
The cell is filled with the watery fluid, called cytoplasm.
All the organelles of the cell, float in the cytoplasm.
Some of the major organelles, of the cell are:
Mitochondria.
This is the power house, of the cell.
It produces the energy required, for the cell to live.
Endoplasmic reticulum.
These produce the proteins and lipids,
and transport them, with in the cell.
Golgi complex.
This concentrates some secretions,
adds carbohydrates to some secretions,
and exports them from the cell.
Vacuoles.
These are like small store houses.
It stores secretion, and waste products.
These and other organelles perform the basic functions of a living cell.
Specialised tissues and organs, are built from these cells.
Tissues are collections of specialised cells.
Between the tissues, there is a fluid called the interstitial fluid.
Interstitial fluid is also called as tissue fluid.
Tissue fluid play a role, in transporting substances, to and from the cell.
Cellular respiration.
Cellular respiration, is the set of chemical reactions,
that takes place inside the cells.
These reactions convert, bio chemical energy,
from nutrients, to A T P.
A T P which stands for Adenosine Triphosphate, is a chemical compound.
The formula for A T P, is C10, H16, N5, O13, P3.
A T P is the unit of energy currency, within the cell.
It is used for intra cellular energy transfer.
Respiration is one of the key ways, that the cell generates,
useful energy, to fuel cellular activity.
Cellular respiration, is an exothermic reaction.
Heat is generated by cellular respiration.
It also creates, waste products.
Aerobic respiration, is one of the main methods, of cellular respiration.
Aerobic respiration, uses oxygen to break down,
carbohydrates, fats and proteins.
One example, of aerobic respiration, is the break down of glucose.
The chemical equation is,
C6 , H12, O6, + ,6O2, results in,
CO2, +, 6H2O, +, heat.
The glucose comes from the nutrients,
and oxygen comes from the air we breathe in.
The CO2 generated, is what we breathe out.
Cell Metabolism.
The set of life sustaining chemical transformations, within the cells,
is referred to, as cell metabolism.
Metabolism, can be divided into two categories.
Catabolism and anabolism.
Catabolism involves, taking in oxygen and nutrients,
breaking down the nutrient molecules,
producing energy to live,
and disposing off waste and carbon dioxide.
Anabolism, uses energy to construct components of cells,
such as, proteins, and nucleic acids.
Metabolism, is the basic process of life, that takes place continuously , in every cell.
Cell metabolism, is the basis for life itself.
The human body, basically comprises, of a large number of cells.
Collectively, the cell metabolism of all the cells,
can be referred to as a metabolism, of the human body itself.
Human body as a system.
Human body functions as a whole system.
It has many functional sub systems.
These functional sub systems are interrelated.
They work together, as a whole living system.
The major functional subsystems, of the human body are:
The nervous system.
The respiratory system.
The cardio vascular circulatory system.
The skeleton system.
The muscular system.
The digestive system.
The endocrine system.
The reproductive system.
The urinary system.
The skin system.
The nervous system.
The nervous system is a control and communication system,
of the human body.
The brain is the control centre, for the body.
There are nerves, running through out the body.
The nerves are the communication lines, of the body.
The brain sends, control commands, to all parts of the body,
through the nerves.
The nerves which perform the function,
of communicating the brain’s command, is called as the motor nerves.
The nerves communicate information, from through out the body, to the brain.
The nerves that communicate information to the brain,
is called as the sensory nerves.
The Brain.
Brain is the most important part of the body.
It is the control and command centre of the body.
It is like the corporate headquarters.
It is securely located inside the skull.
The brain comprises of a mass of soft nerve tissue.
Brain cells are called neurones.
The brain has billions of neurones.
Neurones have a way, to communicate, with the neighbouring neurones.
The neighbouring neurones, in turn can communicate,
with their neighbouring neurones.
The brain is like a internet of neurones.
One neurone can connect, to any other neurone.
Many neurones work together, to achieve an objective.
The brain should be understood, as a holistic organ.
The brain also has some recognisable parts.
They are the cerebrum, cerebral cortex, cerebellum, and medulla.
The cerebrum is the largest part of the brain.
The cerebrum has a right hemisphere, and a left hemisphere.
In common language, it is referred as the right brain and the left brain.
The cerebrum is the centre for thought and intelligence.
With in the cerebrum, some areas, seem to specialise,
in a specific function.
For example, some areas specialise in hearing, smell, sight, memory,
learning, motor and sensory functions.
Cerebral cortex, is located on the periphery of the cerebrum.
Cerebral cortex is involved in learning, reasoning, language and memory.
The cerebellum is located below the cerebrum, at the back of the brain.
The cerebellum controls the voluntary muscles.
The medulla is located, where the brain connects, to the spinal cord.
It controls involuntary living functions, like heart rate, and breathing.
Spinal Cord.
The brain communicates, with the rest of the body through nerves.
The spinal cord, is like a information highway, between the brain,
and most of the body.
The spine is the back bone of the body.
It comprises of number of hollow bones.
The main motor nerves, and the sensory nerves, pass through the spine.
Branches from these nerves, reach out, to most parts of the body.
Nerves.
Nerves are like wires, that run, through out the body.
They comprise of neurones.
The neurones in the nerves perform the function,
of transmitting information, in the nerves.
Neurones have a cell body, an axon, and dendrites.
The dendrites are like the in gates, for the neurone cell.
Information impulses travel through the dendrites, to the nerve cell body.
The axon is like the out gate, of the neurone.
Information impulses travel out through the axon.
There is a small gap, between the axon, of one neurone,
and the dendrite of another neurone.
This gap is called the synapse.
Specialised chemicals transmit the information,
from the axon of one cell, to the dendrite of the next cell.
These special chemical are called neurotransmitters.
We might be familiar, with drugs called painkillers.
Painkillers do not kill pain.
They inhibit, or suppress the sensation of pain,
from being transmitted, from one neurone to another.
So, though the pain is present, the brain does not feel it.
Sensory Organs.
We sense the environment, through sensory organs,
like the tongue, the nose, the ear, the eye, and the skin.
The sensory information, is transmitted to the brain,
via sensory nerves.
Tongue.
The tongue is the sensory organ for taste.
It senses the four basic type of taste, sweet, salty, bitter, and sour.
Apart from the basic tastes, the tongue can also sense,
spiciness or pungency.
For example, Chilli and pepper, induce this sensation.
Nose.
The receptors for smell, is located in the nose.
Olfactory nerves carry the sense of smell, to the brain.
The sense of smell along with the sense of taste,
influence our appetite for food.
Ear.
Sound is recognised by our ears.
Sound waves enter the auditory canal, and reach our ear drums.
Sound waves are pressure waves.
The sound waves cause the ear drums to vibrate.
These sound signals are carried to the brain, by the auditory nerves.
Eye.
Eyes contain the receptor cells, for light.
The light signals enter through the cornea.
The lens in the eye, helps to focus the image.
The retina captures the image signals.
The optic nerve transmit, the signals to the brain.
Skin.
The skin is a multi functionary organ.
One of the functions of the skin, is the sensory function.
It can sense sensations like heat, cold and pain.
The skin has millions of nerve endings.
Through these nerve endings, we are able to sense,
the environment throughout the body.
Respiratory System.
Ten seconds after a baby is born, it takes it’s first breath.
We take our last breath, before we die.
The period in-between is our life time.
The respiratory system, works non-stop, through out our life time.
Oxygen is critical, to our living.
The respiratory system breathes in oxygen.
Oxygen is used for the metabolism of cells.
Carbon dioxide, is the waste product,
of the metabolism in the cells.
The respiratory system breathes out carbon dioxide.
We breathe through our nose.
When we inhale, we take in, atmospheric air.
The atmospheric air contains Oxygen.
The air is transported to the lungs.
We have two lungs.
From the nose, the air travels via,
the pharynx, larynx, trachea and bronchus to the lungs.
These air vessels, are like the high ways, for transport of air.
The bronchus branches out into smaller air vessels,
called bronchioles.
The bronchioles fill small air balloons, called alveoli.
The lung contains about 2400 Km of tiny air ways.
It has about 300 to 500 million alveoli.
Since all this is located within our lungs,
you can imagine how small the bronchioles are,
and how tiny the alveoli are.
The cardio vascular system, pumps blood to the lungs.
Blood vessels also, branch out into tiny vessels, called capillaries.
The capillaries carrying the blood, surround the alveoli.
There are about 1000 km, of capillaries in the lungs.
The capillaries are very very thin, blood vessels.
The blood which comes to the heart, has carbon dioxide.
The carbon dioxide enters the alveoli, from the blood capillaries.
Oxygen in the alveoli, is absorbed, by the blood.
In this manner the blood exchanges, waste carbon dioxide,
for vital Oxygen.
This is the essential function, of the respiratory system.
The Oxygen rich blood, travels back to the heart.
From the heart, the Oxygen rich blood, is pumped to most of the cells,
in the human body.
During exhalation, the carbon dioxide, taken in by the alveoli,
is breathed out.
A complete breath, comprises of an inhalation and an exhalation.
The breathing process is controlled by the brain.
The breathing process is completely automated, and regulated,
by the medulla in the brain.
Thanks to this automation, we can never forget to breathe,
even in our sleep.
Cardio vascular system.
The Cardio vascular system, is the transportation system,
of the human body.
It transports nutrients and oxygen, to the cells.
It carries away, carbon dioxide, and waste from the cells.
The cardio vascular system comprises of the heart and the blood vessels.
The Heart.
The heart is the most important organ, of the cardio vascular system.
Blood vessels, called veins, transport blood to the heart.
This blood contains carbon dioxide and waste.
The heart pumps this blood, to the lungs.
The lungs exchange waste carbon dioxide, for vital oxygen.
Oxygen rich blood comes back to the heart.
The heart then, pumps the oxygen rich blood to the cells.
Medical professionals, who specialise in the heart, are called cardiologists.
The heart has four major chambers.
The heart can be thought of having a left part, and a right part.
It also has a top part, called the atria.
and a bottom part, called the ventricle.
So, the four chambers are:
The left atrium,
The right atrium,
The left ventricle,
The right ventricle.
The heart is the blood pump of the body.
It pumps blood to the cells, and receives blood coming from the cells.
It pumps blood to the lungs, and receives blood from the lungs.
The pumping action of the heart, is through contraction and relaxation.
The contraction phase, is called systole.
The pressure it exerts when contracting is called the systolic pressure,
which is a higher pressure.
The contraction phase, is called diastole.
This pressure is called diastolic pressure, which is lower.
Blood pressure is measured in millimetres of mercury.
Typical blood pressure, is around 120 by 80.
120 refers to the systolic pressure.
80 refers to the diastolic pressure.
A complete cycle of a systole, and diastole, constitutes a cardiac cycle.
In common terms, we call it a heart beat, or a pulse.
Heart normally beats, about 80 times a second.
But this can vary.
When we run, or when we get angry, our heart beat rate increases.
Blood Vessels.
Blood vessels does the actual transportation of the blood,
to and from the heart.
The system of blood vessels, is called as vascular system.
The arteries carry blood away from the heart.
The veins carry blood to the heart.
The arteries have thick, muscular, elastic walls.
They are the high ways for oxygenated blood.
Arteries branch out into arterioles, which are thinner.
Arterioles branch off, into capillaries, which are very very thin.
Capillaries reach the blood, to almost all the cells in the body.
From the capillaries, oxygen and nutrition is transferred to the cells.
Carbon dioxide and waste products, like urea and creatinine, is transferred,
from the cells to the blood.
This blood travels back, to the heart, in a separate route.
Capillaries, Venules and veins, carry blood back to the heart.
The blood circulation system, is a one way system.
There are separate blood vessels, to carry oxygenated blood, from the heart.
There are separate blood vessels, to carry deoxygenated blood, to the heart.
Blood.
Plasma is the liquid carrier, of the blood.
Plasma is a pale yellow coloured fluid, in which the blood cells, are suspended.
The blood also transports many other materials, through out the body.
Blood in the arteries transport oxygen, from the heart, to the cells.
Blood in the veins transport carbon dioxide, from the cells to the Heart.
Blood transports nutrients, glucose, amino acids,
fatty acids, mineral salts, etc.
It transports messenger chemicals, like hormones.
It transports waste products like urea, and lactic acid.
Blood regulates the acidity levels.
It is slightly alkaline, with a Ph ranging from 7.35 to 7.45.
Blood also plays a role, in regulation of body temperature.
Blood cells are regenerated, by the body.
We can donate blood, for patients who need them.
This does not cause, any health problems, to the donor.
The body can easily regenerate the blood, which is donated.
Blood Cells.
The blood cells are produced, in the bone marrow, and lymphatic glands.
There are basically three types of blood cells.
Erythrocytes or red blood cells, (RBC in short).
Leukocytes or white blood cells, (WBC in short).
Thrombocytes or platelets.
Red blood cells have haemoglobin, which gives it, its red colour.
Haemoglobin carries the oxygen molecules.
There are about 5 million red blood cells, in one cc of blood.
The life span of RBCs are about 100 to 120 days.
White blood cells help fight infection.
They attack foreign micro organisms, which infect the body.
White blood cells, are part of the immune system.
Most of the time they work silently, to protect our body.
We would not be aware of many potential threats,
because they are eliminated, by white blood cells, before they cause harm.
There are about 8000 white blood cells, in a cc of blood.
Platelets are involved, in blood clotting.
When we have a small cut, it is the platelets,
which clot the blood, and plug the leak.
This stops the bleeding, and prevents further blood loss.
There are about two hundred thousand to four hundred thousand,
platelets in one cc of blood.
Blood Groups.
Different persons have slightly different blood groups.
Some of the most common blood groups are,
Blood group AB.
This blood has both A and B antigens.
Antigen stands for anti body generator.
Blood group A.
This blood has A antigen.
Blood group B.
This blood has B antigen.
Blood group O.
This blood has neither A or B antigen.
Another factor which determines the blood group, is called the Rh factor.
If the Rh protein is present, it is called RH positive.
If it is absent, it is called Rh negative.
Blood groups are normally classified, using both these factors.
So blood group can be O positive, A negative, B positive, etc.
When we donate blood, it is preserved in a blood bank.
All blood groups, are not compatible, with each other.
Some blood groups, are compatible with each other.
Before giving blood to a patient, professionals check the compatibility.
In emergencies, the media typically announces,
that blood of a particular blood group, that is required.
It is a good practice, to record and keep our blood group, in our ID cards.
Blood Circulation.
Blood is continuously circulated in the body.
The heart which acts like a pump, is central to this circulation.
Deoxygenated blood comes into the right atrium of the heart.
This blood enters the right ventricle.
From here it is pumped to the lungs.
Carbon dioxide is removed from the blood, and oxygen is added, by the lungs.
The oxygenated blood comes to the left atrium.
From here it is pushed into the left ventricle.
From the left ventricle blood is pumped at a higher pressure to the arteries.
From the arteries, it branches out to the arterioles.
From the arterioles, it branches out, to the capillaries.
Blood from the capillaries, reaches the cells.
Oxygen and nutrients from the blood, enters the cell.
Carbon dioxide and waste, is transferred to the blood.
Now the blood is deoxygenated.
Substances from the blood, do not directly enter the cell.
From the blood, it is transferred to the interstitial, or tissue fluid.
From the tissue fluid, it enters the cell.
The deoxygenated blood cannot take the same route back.
It is a one way system.
The deoxygenated blood, enters separate capillaries.
The capillaries join up into venules.
The venules join into the veins.
The veins reach the heart.
This blood enters the right atrium.
Now the blood circulation cycle is complete.
During the circulation, the blood also passes through some organs,
like the kidneys, liver, etc.
Lymphatic system.
Tissue in the body, is a collection of specialised cells.
Between these cells there is a fluid, called the interstitial fluid.
Interstitial fluid is also called as tissue fluid.
Exchange of substances, between the blood vessels, and the cells,
takes place via the tissue fluid.
There is a separate set of vessels,
to carry part of the tissue fluid, and return it, to the blood stream.
This is done by the lymphatic system.
The lymphatic system, is also the crucial part,
of the body’s immune function.
The lymph fluid, starts of as a clear blood plasma like fluid.
As it passes through, the lymphatic system,
it acquires other substances, specially white blood cells.
The lymphatic system comprises of:
Lymphatic capillaries.
Lymphatic vessels.
Lymphatic nodes.
Lymphatic tissue and organs.
Lymphatic ducts.
Lymphatic capillaries and vessels carry the lymph fluid.
Lymphatic ducts, return the lymph fluid, via the veins,
to the blood circulation system.
In this manner the tissue fluid, returns to the blood stream.
Lymph nodes are found under the arms, in the neck, and in the groin.
Lymphatic tissues is found in the spleen, tonsils, and the thymus.
Lymph nodes and tissues, are important part, of the body’s immune system.
Immune system.
White blood cells, in the lymphatic system, is also called as lymphocytes.
They are produced, mainly in the thymus and the bone marrow.
The lymphatic system plays a role, in the circulation of white blood cells.
White blood cells, perform the immune functions, of the body.
The immune system, protects the body from infections.
There are mainly 3 types of lymphocyte cells.
N K cells, or natural killer cells.
B cells.
T cells.
These white blood cells, work in slightly different ways.
But they have a common purpose.
They identify, and eliminate foreign cells.
Foreign cells, which are harmful to the body, are called pathogens.
When we get an infection, our body is invaded by pathogens.
White blood cells identify them, and eliminate them.
The immune system works in a complex and fascinating way.
Part of our immune system, is inherited.
Part of it, is passed on to the baby, through mother’s milk.
Another part, is learnt by the body,
as it encounters new infections.
It is fascinating to know, that the body develops,
specific immune cells, for every type of infection, it encounters.
They are called anti bodies.
Through our life time, we might acquire, hundreds of anti bodies.
Once a anti body is designed, it remains through out our life time.
The immune system is always at work, though most of the time,
we are unaware of it.
Vaccination is a way, to prevent future infections.
Babies and young children, are vaccinated, to protect them,
from many known illnesses.
Vaccination is a crucial part, of preventive health care.
Vaccination, makes use of the body’s natural immune system.
When a micro dose, of a infecting agent is administered, to the body,
the body develops, a life long immunity to the illness.
The immune system, develops a specific antibody, for the specific pathogen.
This is possibly one of the greatest achievements, of modern medicine.
Many dangerous illnesses, have been dramatically reduced,
due to vaccination.
The disease called small pox, has been totally eliminated.
It is estimated, that before vaccination, small pox killed,
about 1 billion people.
The lymphatic circulation system, is an auxiliary circulation system.
The lymph in the system, joins back the main blood circulation system.
The blood has both red blood cells and white blood cells.
In the blood, they are called erythrocytes and leukocytes.
Digestive system.
The body primarily requires oxygen and nutrients.
The respiratory system, provides the oxygen.
The digestive system, provides the nutrients.
The cardiovascular system, provides the transportation.
We need energy to live.
This energy comes from the food we eat.
The food we eat, cannot be directly used by the body.
The body uses, some basic carbohydrates, proteins and fats.
Fats are also referred to as lipids.
These constitutes the major portion of the nutrients,
that the body needs.
The body also requires small quantities of minerals and vitamins.
Most of this, also comes from the food we eat.
The function of the digestive system, is to convert all the exotic food,
to the basic form, that the cells can use.
The menu card for the body, has only very few items.
The digestive system is also called, as the gastrointestinal system.
There is a dedicated path way for the food in the body.
It starts from the mouth, and extends up to the anus.
This path way, is called the gastrointestinal tract,
or alimentary canal.
Mouth.
The process of digestion, begins in the mouth.
The teeth in the mouth chews the food.
This mechanically breaks the food, into smaller particles.
The tongue is a sensory organ.
It has taste buds.
These buds can recognise, many different tastes.
The taste signals, are transmitted to the brain.
If we like it, we feel good.
The exotic part of the food, ends here.
After that it is all about,the practical problem,
of digesting the food, or converting it,
to cater to the menu card, of the body.
The mouth has salivary glands.
Salivary glands release enzymes.
Enzymes are digestive chemicals.
They chemically break down the food.
This starts the process of practical digestion.
Stomach.
Food from the mouth, travels through the oesophagus, to the stomach.
The stomach is like a mini mixing machine.
It keeps churning the food, and makes it into a nice paste.
This paste is called the gastric chyme.
It also releases, powerful gastric juices, and hydrochloric acid.
These gastric juices, help to chemically digest the food.
In this process, complex food molecules,
are broken down into basic food molecules.
The stomach is one of the few parts, of the body,
which does not continuously work.
After digesting a meal, it takes rest.
Intestine.
The intestines are a long tubular digestive tract.
They are wrapped up, into a compact form, and located below the stomach.
There are two main intestines,
the small intestine,
and, the large intestine.
The chyme, the semi digested food, from the stomach enters the small intestine.
Most of the digestion is completed in the small intestine.
The small intestine is about 6 m long.
The first part of the small intestine, is called the duodenum.
It receives digestive juices from the pancreas and the gall bladder.
This helps to break down the food further.
It also releases alkaline bicarbonate,
which neutralises, the acid produced in the stomach.
From the duodenum, the food passes to the jejunum.
Now the food has been reduced to sugars, amino acids, and fatty acids.
These are the basic food, that the cells require.
These are possible to be absorbed by the blood.
Small projections into the jejunum, called the villi, absorb these basic foods.
These are then transferred, to the blood stream.
The third part, of the small intestine is called the ileum.
The final absorption of basic food, takes place here.
This includes vitamin B 12 and bile acids.
The progress through the small intestine, is complete here.
From the small intestine, the food passes to the large intestine.
The large intestine, is about 1.5 m long.
In the large intestine, water, salts, and some vitamins, are absorbed.
This completes the digestion cycle.
The food absorbed from the digestion system,
is carried to all the cells, by blood.
The digestion which started in the mouth, ends here.
What is left, is waste matter, which is disposed off.
Liver.
The liver is a multi purpose, chemical gland.
It performs many functions.
Some of them are:
Glycogen storage.
Plasma protein synthesis.
Removal of harmful substances, or detoxification.
Manufacture of bile, which breaks down fats.
Maintaining blood, glucose levels.
Producing blood clotting proteins.
Storing of iron.
Storing of vitamins, A, D, E and K.
and so on.
There is a large amount of metabolic activity which happens in the liver.
This results in heat production.
The liver is the main heat producing gland in the body.
Gallbladder.
The gallbladder concentrates and stores the bile,
produced in the liver.
It then releases the bile, needed for digestion.
After a fatty meal, more bile is required for digestion.
Pancreas.
The pancreas is a gland, located behind the stomach.
It produces digestive enzymes, used in the small intestine.
These enzymes help to further breakdown,
carbohydrates, proteins, and lipids.
Pancreas is a multifunction organ.
It also produces hormones, like insulin, glucagon, somatostatin, etc.
The digestive system as a whole, plays the important role,
of converting the food we eat,
to the nutrients, that the cells in the body needs.
The nutrients from the digestive system are transported,
by the blood, in the cardiovascular system,
to the cells.
Endocrine system.
One way that the brain, communicates with, and controls the body,
is through the nervous system.
For example, heart beat, breathing, muscle movement, etc,
is controlled through the nervous system.
The nervous system uses electrical signals, to communicate with the body.
There is another way that the brain, communicates with, and controls the body.
This system is called the endocrine system.
The endocrine system, is a chemical messenger system.
Hormones are the chemical messengers.
Hormones are produced, or secreted by the endocrine glands.
The endocrine system, is composed of endocrine glands, and hormones.
These hormones are released into the blood stream.
Endocrine glands are present, in the brain, and other parts of the body.
Endocrine glands in the brain, control the functioning, of the endocrine glands,
in the other parts of the body.
The brain, through the endocrine system,
regulates many body functions.
Blood is the transport mechanism, for the chemical messenger hormones.
The endocrine glands, in the brain, sends command signals,
to the other endocrine glands.
Each command signal, is a specific hormone, which is targeted,
to a specific gland.
For example, thyroid simulating hormones, are targeted,
to the thyroid gland.
When a gland receives, a control message hormone,
it responds by producing more, or, less, of certain other hormones or chemicals.
For example, the pancreas, may be instructed, to produce,
more digestive chemicals.
The brain receives feedback, via chemical messages in the blood.
The glands in the brain interprets, these messages,
and sends out further instructions to the glands.
The instruction can be to stimulate, or produce more, hormones or chemicals.
The instruction can be to inhibit, or produce less, hormones or chemicals.
This way the glands in the brain, are able to control, all the glands in the body.
In this manner the brain, through the endocrine system,
is able to control, and regulate, many functions in the body.
Some examples, of the functions,
that the endocrine system controls and regulates are :
body growth,
blood sugar,
metabolism,
reproduction,
sleep, etc.
The main glands in the endocrine system are :
Pituitary gland.
Pineal gland.
Hypothalamus.
Thyroid gland.
Thymus .
Pancreas.
Adrenaline gland.
Ovaries.
Testes.
Pituitary gland.
The pituitary gland is a kind of master gland.
It is located in the brain, behind the eyes.
It works in conjunction, with the hypothalamus, and the pineal gland,
which is also located in the brain.
The glands in the brain perform the control functions,
of the endocrine system.
They produce hormones, which control other glands.
These control hormones, stimulate or inhibit secretion of hormones or chemicals,
by the other glands.
Some of the regulatory functions of the pituitary gland are :
Growth.
Blood pressure.
Pregnancy.
Reproductive function.
Thyroid gland function.
Metabolism of the body.
Water balance.
Solute concentration.
Body Temperature.
Pain relief, etc.
Hypothalamus.
The hypothalamus is part of the brain.
It releases hormones that stimulates, or inhibits,
the release of hormones, by pituitary glands.
Pineal gland.
The pineal gland is located near the hypothalamus, in the brain.
It produces hormones, which modulates, sleep pattern.
The twenty four hour, day night rhythm, is called the circadian rhythm.
The body is aware of the circadian rhythm.
This is made possible by the hormones released, by the pineal glands.
Thyroid gland.
The thyroid gland is located in the neck.
It produces a hormone, which regulates growth.
It also regulates, the general metabolic rate, of the body.
The body’s metabolism is determined, by the cellular metabolism.
This is controlled by the thyroid gland.
Calcium plays a role, in nerve impulses, and muscle movement.
The amount of calcium and phosphorus in the body,
is also controlled, by the thyroid gland.
Thymus.
The thymus is located in the chest area.
The thymus is the key component, of the immune system.
It is also a gland, in the immune system.
The thymus is involved, in the production of white blood cells.
White blood cells produce antibodies.
Antibodies fight invasive harmful bacteria or pathogens.
Pancreas.
The pancreas is located in the abdomen, behind the stomach.
Pancreas produces the hormones, insulin and glucagon.
The hormone Insulin acts to lower blood sugar.
The hormone Glucagon acts to raise blood sugar.
By releasing appropriate hormones, the pancreas regulates the amount,
of blood glucose levels.
The pancreas is also a part of the digestive system.
It secretes digestive enzymes.
Digestive enzymes help to further break down, carbohydrates, proteins,
and lipids, into nutrients which can be absorbed, by the small intestine.
Adrenal gland.
The adrenal glands are located above the kidneys.
They help the body grow, and adapt to stress.
It produces adrenaline.
Adrenaline is involved in the flight or fight response, of the body.
When we perceive a threat, we decide whether to fight or flee.
Adrenaline is involved in this response.
Release of adrenaline, increases the heart beat rate.
The adrenal gland also helps the kidney,
in controlling the amount of salts and substances, in blood.
Ovaries.
The ovaries are involved, in the release of,
the female reproductive egg, called the ovum.
They also play a role, during pregnancy.
Testes.
The testes produces a hormone, which contains,
male reproductive cells, called sperm.
All the endocrine glands, work together as a system.
The endocrine glands in the brain, acts as the control gland.
All the other gland respond, by producing the appropriate hormones or chemicals.
This in turn, regulates body functions.
The blood acts as a transport system, for the messenger hormones.
The brain receives feedback, via the blood, and depending on the feedback,
sends further control hormones, to the glands.
Urinary System.
The main function of the urinary system,
is to dispose off, the soluble waste from the body.
Solid waste, is disposed off by the digestive system.
Soluble waste, is disposed off by the urinary system.
The urinary system comprises of :
The Kidneys,
The Ureters,
The Bladder,
The Urethra.
Kidneys.
Kidneys are organs, located in the abdominal cavity.
We have two kidneys which perform, identical functions.
Blood from the blood vessels pass through the kidneys.
The main function of the kidneys,
is to remove metabolic waste, from the blood.
The kidney is a multi function organ.
It also:
Assist in the regulation of blood pressure.
Maintains the balance of body fluids.
The nephron is the basic working unit of the kidney.
Blood enters the nephron under pressure.
The blood is filtered by the nephron.
Most of the water, and required substances,
are returned back, for circulation.
Waste products, like urea and ammonia, is removed from the blood.
Other unwanted or excess substances, are also removed.
The kidney varies, the amount of substances, removed or recirculated.
This way the kidney, is able to perform, a regulating function,
for some selective substances.
For example, excess glucose from the blood, is removed.
The liquid, containing the waste soluble substances, is called urine.
The urine is sent to the urinary bladder, via the ureters.
The urine is disposed off, via the urethra.
Reproductive system.
When a male sperm cell fertilises, a female ovum cell,
a new life is born.
Reproduction, is a defining feature of life itself.
The male reproductive cells, are present in the sperm.
These cells are the father cells.
Every cell has DNA at it’s core.
DNA comprises of 23 pairs of chromosomes.
One pair of chromosomes, is related to gender.
The gender chromosomes, in the sperm cells,
have one ‘X ‘chromosome and one ‘Y’ chromosome.
The sperm is produced in the testes.
The ovaries mature the female reproductive cell.
It is called the ovum.
The gender chromosomes in the ovum, has two ‘X’ chromosomes .
It is the mother cell.
The ovaries release, one ovum at a time, at periodic intervals.
This ovum, enters the fallopian tubes.
Millions of sperm cells are released by the male.
Only a few of them, might manage to reach the fallopian tube.
Here, it might get to meet the ovum, and fertilise it.
If fertilisation succeeds, it is called conception.
When fertilised, the sperm cell, fuses with the ovum cell.
The resulting cell, is called a zygote.
During fertilisation, the sperm cell, may contribute,
a ‘X’ chromosome, or a ‘Y’ chromosome to the ovum.
If it contributes a ‘X’ chromosome, the resultant zygote,
will have a gender chromosome, with two ‘X’ chromosomes.
In this case, the gender of the resulting zygote, will be female.
If the sperm cell, contributes a ‘Y’ chromosome, to the ovum,
the resultant zygote, will have one ‘X’ chromosome, and one ‘Y’ chromosome.
In this case, the gender of the resulting zygote, will be male.
By this wonderfully simple design, nature ensures,
that about half the population, is female,
and the other half of the population, is male.
This is because, the probability of the sperm cell,
contributing a ‘X’ or a ‘Y’ chromosome, is 50%.
The zygote travels to the uterus.
It gets implanted , in the wall of the uterus.
The uterus will be the home, for the new life, till it is born.
The uterus is also called as the womb.
The zygote, is a single cell.
It reproduces itself.
Initially these cells are undifferentiated cells.
These undifferentiated cells, are called as embryonic stem cells.
These stem cells multiply, and grow in numbers.
Later, these cells differentiate,
and become differentiated cells,
of specific tissues like muscle, heart, liver, kidney, etc.
In the first eight weeks of development,
the new life, is called as an embryo.
After that, it is called the foetus.
The foetus is only about 3 cm in size, and weighs about 8 grams.
At this stage, the cells have become specialised.
Now we can hear faint heart beats, of the foetus, via ultrasound.
All the organs, of the human body, start developing at this stage.
The foetus grows for 35 to 38 weeks in the uterus.
The placenta connects the foetus, to the uterine wall.
The umbilical cord connects the foetus to the placenta.
The mother’s body supplies all nutrients and the oxygen,
to the foetus, via the umbilical cord.
In this naturally wonderful process, the foetus grows,
into a baby.
The gestation period of growth, of 35 to 38 weeks,
is also know as the pregnancy period.
After the completion of the gestation period,
a brand new baby is born.
This is the beginning of independent life, for the baby.
Musculoskeletal system.
The skeletal system, gives a structure and shape, to our body.
The skeleton is the collection of bones, in our body.
Without the skeleton, we will be like a sponge.
The muscle system, works along with the skeletal system.
This helps our body, to move.
Of course, we can do many things, apart from mere movement.
We can walk, run, play, dance, etc.,
If we watch a gymnast, a yoga practiser, or a classical dancer,
we can appreciate, all the wonderful things that our body can do.
All this is possible, thanks to our musculoskeletal system.
Bones are rigid, structural elements of the skeleton.
Joints connect the bones.
A ligament, is a fibrous tissue, that connects one bone to another bone.
Muscles are the tissues, which enables us to produce force and motion.
Tendons are the tissue, which connects the muscle to the bone.
The bones, the joints, the ligaments, the muscles, and the tendons,
together constitute the musculoskeletal system.
Skeletal system.
A human skeleton has more than 200 bones.
If we just had bones, we will be rigid, like a statue.
It is the joints, which connect the bones, which gives us the flexibility.
We have more than 300 joints, in our body.
If we look around our body, we find that, we can flex most of the parts.
The flexibility that we have, is three dimensional.
This is not only a great advantage, but also makes our movement,
graceful and elegant.
If we compare a robot’s movement, with a classical dancer,
we will be able to appreciate the grace of movement,
that the human body has.
Bone.
Bone is a dense tissue, mainly of the mineral, calcium phosphate.
The exterior of the bone is extremely hard.
It is called the compact bone.
Beneath that we have a softer bone, called the spongy bone.
The bone marrow, is comprised of spongy bone.
On the whole, the bone is a rigid element.
It does not bend.
When we bend our hand, the bone is rigid, but the joints,
make our hand flexible.
Skeleton.
All the bones in the body, along with the joints form the skeleton.
The skeleton is preserved, even after death.
The fossils that we discover, of the ancient bodies, is mainly the skeletal bones.
Scientists are able to study, ancient life forms, by studying the fossils.
For example, we might have seen a reconstructed form,
of a dinosaurs in a museum.
A human skeleton gives us, a distinctive form and shape.
The skeleton of we homo sapiens, can be easily differentiated from other animals.
Scientists are able to identify, even extinct animals,
based on excavated bone fossils.
Some bones have a protective function.
The brain comprises of very soft tissue,
it can be easily squashed, if we apply pressure.
Fortunately, we have a skull, which protects our brain.
The lungs and the heart, are also delicate organs.
These organs are protected, by our rib cage.
We have more than 200 bones and 300 joints.
Each of them perform, some unique function.
The bones in the hands and the legs, act like levers.
Some are worth a special mention.
Spine.
The spine or the back bone, is called the vertebral column.
It comprises of smaller bones, called vertebrae.
Most of them are flexible, and they are called as articulating vertebrae.
We have 24 flexible or articulating vertebrae.
Between these vertebrae, we have inter vertebral discs.
Inter vertebral discs are sponge like tissues.
This is what makes the spine flexible.
We can bend the spine in many ways, even rotate it.
We can look at some yoga postures, to understand, how flexible the spine is.
There is another interesting thing about our spine.
It is vertical.
We are the only animal, which learnt to stand.
The first species, which learnt to do that, was called the Homo Erectus.
This learning happened, over thousands of years of evolution.
But it was worth it.
Once we learnt to stand, we learnt to walk, on two feet.
This was a major achievement.
We no longer required, our fore legs to walk.
They became free.
They evolved, into hands, which is another amazing,
evolutionary design, of nature.
The spine, played a crucial role, in the evolution of man, from animal.
The spine has, another important function.
It is hollow, it is like a flexible hollow pipe.
The brain communicates, with the body, through the spinal cord.
The spinal cord, is like the information highway, of the nervous system.
All the control communications to the nerves, in the body,
goes through the spinal cord.
All the sensory information from the body, travels to the brain,
through the spinal cord.
The spinal cord is very delicate.
It passes through the hollow portion of the spine.
The bones of the spine, protect the spinal cord.
The spine is a important part of the skeletal system.
It is aptly called the back bone.
Bone marrow.
Apart from providing rigidity and flexibility, nature has designed,
an additional function for the bones.
Bone marrow, is the flexible tissue, in the interior of the bones.
Red blood cells are produced in the bone marrow.
New blood cells have to be continuously generated,
to replace expired blood cells.
Billions of blood cells, are produced by the bone marrow every day.
The bone marrow, is also involved, in producing white blood cells, or lymphocytes.
White blood cells are a key components, of the lymphatic system.
So, the bone marrow, is a part of the lymphatic system.
Muscles.
Muscles are soft tissues, through out most of our body.
Muscles function, along with the skeletal system,
to produce, force and motion.
It is the force exerted, by the muscles, which enables us,
to walk, run, play, lift, and many more functions which we perform routinely.
Muscles can be classified as voluntary, and involuntary.
Voluntary muscles, are controlled by conscious thought.
Our skeletal muscles, are voluntary muscles.
They are controlled by our conscious thought process.
Involuntary muscles, function automatically, without our conscious thought.
The heart muscles, are an example of involuntary muscles.
Though the heart muscles, work non stop, it does so, without conscious thought.
The heart muscle are also called as cardiac muscles.
The muscles, which are attached, to our skeleton, are called skeletal muscles.
These muscles, are comprised of muscle fibres.
A muscle has many tightly packed muscle fibres.
It is something like a rope, which has fibres.
Muscles can elongate, or shorten.
Skeletal muscles typically work in pairs.
When one muscle elongates, the complementary muscle, shortens.
Together, they are called as muscle contraction.
This combination enables force and action.
When we bend our hand, we can see our biceps bulging up.
This muscle, is shortening, when we bend our hand.
When we straighten our hand, the muscle elongates.
Muscle elongation and shortening, together is called muscle contraction.
Muscles in our forearms, wrists, thighs, legs, etc.,
work in a similar fashion.
Muscles also enable us, to rotate our neck, hands, legs, etc.
Rotation is also achieved, by the complementary actions,
of lengthening and shortening muscles.
We have more than 300 pairs of skeletal muscles,
attached to our skeleton.
Ligaments are the muscles, which attach one bone to another.
The muscles are attached to the bone, by tendons.
We have many muscles, which help to produce force and motion.
Some examples of these muscles are:
Deltoids, Triceps, Biceps, Trapezius, in our shoulders and hands.
Sartorius, Quadriceps, Tibialis anterior, Hamstring, in our legs.
Muscle contractions, are controlled by impulses, from the nerves.
These impulses mostly originate, from the brain.
The motor cortex, in the brain, controls the muscles.
Different parts of the motor cortex, controls different parts, of our body.
If we think, that we want to wiggle our toes,
our toes wiggle.
If we think, that we want to wiggle our index finger,
the brain is able to wiggle, exactly the exact finger.
This sounds obvious to us.
But, if we think about it, we realise that the brain,
somehow knows where exactly, each muscle is,
and what it is doing.
This muscle sense of the motor cortex brain,
is called proprioception.
We are able to touch, our fingers, from two hands,
behind our back, without being able to see it.
This is due to the power of proprioception.
We play a game of football, without thinking too much about,
controlling muscles.
Our thoughts are some how converted, to electrical impulses.
The brain also receives impulses, from the muscles.
The process by which, the brain, controls and coordinates,
all our muscles, is a fascinatingly complex process.
We are yet to invent a robot, which can mimic a good goal keeper.
We can train our brain, to better coordinate and control our muscles.
This itself, is a type of intelligence.
A classical dancer, or a gymnast, are examples, of persons,
who have trained their mind and body, to a higher level.
Muscles were designed by nature, to do work.
When we use our muscles, they actually get better and stronger.
If we don’t use it, they tend to weaken.
Aerobic exercise, is the main way, that muscles get exercised.
Aerobic exercise, uses oxygen.
Nutrients like glucose, are broken down to produce A T P.
A T P is a ready source of energy, for the cells.
This process is called aerobic respiration.
It takes place in the mitochondria.
Walking, running, playing are examples of aerobic activity.
When we engage in these aerobic activities, we breathe more deeply.
The other form of exercise, is called anaerobic exercise.
This form of exercise, does not require much oxygen.
The muscles, use the glucose and the A T P, to generate energy.
Stretching, weightlifting are examples, of anaerobic exercise.
Many activities, are a mix of aerobic and anaerobic exercise, of the muscles.
In earlier times, our muscles got naturally exercised.
In those times, we used to do most of our work manually.
Walking, working in the fields, at home, etc. naturally exercised our muscles.
In modern times machines do most of the work.
This in a way, is very convenient and comfortable, for us.
But, this makes our muscles idle, which is not good for a healthy body.
We need to find some way of exercising our muscles.
There are many enjoyable ways, by which we can exercise our muscles.
Hiking , gardening, playing, dancing, are examples of enjoyable activity,
when muscles get aerobic exercise.
All the sub systems of the body, actually work together, as a system.
We study them as different subsystems, only to understand it better.
The actual function of any part of a human body,
is a incredible coordination of many subsystems.
We will take one simple example, the hand.
The hand is a very important part, in human evolution.
We first learnt to walk on two legs,
freeing up our fore legs.
These fore legs evolved into hands.
We can proudly say, that we have the best designed hands, by nature.
No other animal, has hands, which is as sophisticated as our hands.
If something goes out of our control,
We say “It is gone out of our hands”.
This seems to imply that if our hands can do it,
we can do it.
This was specially true, during our earlier stages of our evolution.
It is with our hands, that we learnt to make tools,
and manipulate and master our environment.
Hand.
We have 5 fingers, in each hand.
Our hands have about 30 bones, and about 30 joints.
It has more than 120 ligaments.
It has more than 30 muscles.
It has more than 40 nerves.
It has more than 30 arteries.
All these work together, in a co-ordinated way, to accomplish a task.
All this forms an amazing complex mechanism.
No other animal, has hands as sophisticated as ours.
We should be proud, of our humble hands.
We are yet to invent a robot, which is anywhere close,
to the sophistication of our hands.
Motor cortex in the brain, controls the movements in the body.
25% of the motor cortex, is devoted to controlling the hands.
It gives us an idea, how important, our hands are.
Thanks to our hands, we learnt to make tools.
Using tools, we learnt, new ways to gather food, and hunt.
Even today, we use this sophisticated mechanism,
to perform many complex tasks.
One example, is writing itself, which if we think about it,
is an amazingly complex task, which we easily achieve.
The hand is just one example, of how several sub systems,
of the body, work together.
To better understand the working of the body,
we should always keep in mind,
that many subsystems, are working together.
This makes, the understanding of the body, more interesting and fascinating.
Skin.
We now know, that we have a wonderful body.
We just need a container, for all the sub systems, we discussed.
The skin performs, the function of holding, all our body parts together.
Apart from this, the skin performs, some other useful functions:
It Protects the body, by preventing foreign particles from entering it.
The sweat glands, in the skin help in excreting, water and waste products.
It is involved in the process of producing vitamin D.
It helps to regulate body temperature.
The human body maintains a temperature, of about 37 degree centigrade.
When the temperature goes higher, the body loses heat, through the skin,
sweat glands and hair.
When the temperature becomes lower, the body conserves heat.
This process by which, the temperature is maintained,
at almost constant level, is called as a homeostatic process.
There are many processes in our body, which are homeostatic processes.
Skin is also an important sensory organ.
Many nerve endings terminate in the skin.
The skin can sense heat, cold, pressure etc.,
These sensory signals are conveyed, by the sensory nerves, to the brain.
Human body as a system.
A system can have many subsystems.
A system works as a whole.
The whole, is not the sum of all the parts,
It is much, much, more.
A system as a whole is much more complex, sophisticated, and valuable,
than the subsystems.
In our fascinating body,
The Cells, The Nervous system, The Sensory Organs, The Respiratory System,
The Cardio vascular system, The Lymphatic system, The Digestive System,
The Endocrine system, The Urinary System, The Reproductive system,
The Musculoskeletal system, and the skin,
all work together, as a harmonious whole.