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Life is in the blood
by Andrew Hodge
Everyone knows that we must have enough blood flowing
around our body or else our bodily functions deteriorate and we die.
Yet for a long time the exact function of blood was little
understood. In what ways has modern science shown Leviticus 17:11 to be true?
Blood is fundamental to the function of every cell of
every component in our bodies. Cells need food to survive, grow, repair
themselves and to fulfill their specific functions, and, to reproduce.
Cellular food is transported in blood to provide energy
for all the cells’ needs.
As humans are multicellular organisms, having separate
specialized organs with highly sophisticated functions, transport and
communication between these structures is essential.
Coordination
Do the cells of the body tell the blood how it should
work? No. Does the blood carry around everything possible just in case? No.
The cells and the blood work together to provide optimum
conditions for correct functioning of all the cells — with their different
requirements — in all the tissues and organs of the whole body, including the
cells of the blood itself.
Blood provides this coordinated environment by regulating
acidity/alkalinity (pH), providing oxygen (and removing carbon dioxide and
other waste products), and carrying essential vitamins and minerals.
Also, blood has to be in the right places at the right
times, at the right temperature and pressure, and it carries regulatory
messages between organs via blood ‘messengers’ called hormones.
All this is organized within very specific limits — straying
outside these (through injury, disease, toxins, etc.) rapidly reduces
functionality.
Words matter
FLESH (as used in
many English translations of Leviticus
17:11): Hebrew בשר basar,
the tissues that make up the body, and (by extension) also the body, the living
creature.
TISSUE: a collection of
cells (not necessarily the same type) grouped for a specific function. e.g.
connective tissue, muscle tissue. Blood itself is, technically speaking, also a
tissue.
ORGAN: several types of
tissue functionally grouped together, e.g. liver, lung.
Hormonal feedback
Hormones, those important chemical messengers in the
blood, are involved in self-regulating feedback systems.
These systems stimulate hormone production in times of
lack, and suppress it in times of plenty.
For example, when we eat, the sugars in the intestine are
digested and absorbed into the local bloodstream. This blood then passes
through the pancreas and its higher sugar level stimulates production of the
hormone insulin.
As insulin is distributed in the bloodstream, it reduces
the blood sugar to normal levels again by increasing the amount of sugar that
all cells take in.
In fact, the brain relies almost entirely on sugar
(specifically glucose) for its energy supply; hence this feedback system is
absolutely critical for proper brain activity.
If the blood glucose ever drops too much, we lose
consciousness.
The body’s systems tend to be wisely over-engineered, so
that one might predict that there is also a system to cope with low sugar
levels, for example when we exercise and use sugar up.
This system uses the hormone glucagon (also from the
pancreas) and it works by releasing glucose into the blood from stores located
mostly in the liver.
There are about fifteen organs classed as
hormone-producing (endocrine) glands, and their products, carried by the
blood, affect either every cell in general or specifically target certain
cells.
Widely known examples are the male and female hormones
testosterone and estrogen, adrenaline (epinephrine in the US), the thyroid
hormone thyroxine, and many more.
Why is blood red?
The
red colour of blood reflects the colour of the hemoglobin inside the red blood
cells. This is because the hemoglobin contains iron.
The
‘heme’ of the hemoglobin molecule in vertebrates (creatures with a backbone) is
a porphyrin ring which surrounds ferrous iron atoms.
It
is the spatial relationship between heme, iron and globin which makes it
possible to bind oxygen molecules reversibly — one to each iron — and which
makes the system so efficient.
Targets
For example, thyroxine regulates the speed of metabolism
in every cell, and having the correct amount (within narrow limits) allows
normal cellular activity.
Too much and we become ‘hyper’, too little and we are slow
and lethargic.
Another example is gastrin. The target organ for gastrin
is that part of the inner lining of the stomach which produces hydrochloric
acid for digestion.
Food in the last part of the stomach stimulates the
production of gastrin, which is carried back by the blood to stimulate acid
production. This is a positive feedback mechanism in which blood is the
essential communicating link.
Anticipation
Blood also has a major role in body protection in that it
is an integral part of the immune or infection-fighting system, involving
antibodies and white blood cells. It also possesses a highly complex mechanism
to prevent its own loss from the body (clotting) and to prevent clotting inside
the body (thrombosis).
The capacity to quickly initiate clotting outside and to
limit — even reverse — clotting on the inside is provided by ‘cascades’ — cumulative
processes in which each step of the process is dependent on the one before it
(see box).
The cascades are of such complexity that new factors,
cofactors and regulators are being constantly added to our body of knowledge.
It is now known that there are more than a hundred factors or steps that make
up the clotting cascade.
Such details add to our appreciation of how finely
balanced, effective and versatile the system is. But a greater marvel is that
such a system, which is there in anticipation of blood loss, internal injury or
disease, should be there at all.
Unique red blood cells
Having
a molecule such as hemoglobin which can handle oxygen so quickly and
reversibly, when required, is amazing.
Red blood cells (RBCs or erythrocytes) form the majority
of the cells in the blood — and a quarter of all cells in the human body.
They are unique among all others — in mammals, they have
no nucleus and none of the usual energy-producing structures in the cell
outside the nucleus. This is a design feature of mammals (creatures which, like
us, suckle their young).
Normally, a cellular nucleus carries the DNA which
instructs the cell on how to perform its functions, including repair and
reproduction, at the appropriate times.
RBCs cannot do this because instead they are especially
designed to carry oxygen, and in humans, having a nucleus would hinder this
essential function. So, the nucleus is lost after formation, leaving them with
their characteristic biconcave shape.
Blood bytes*
There
are about 4–6 million red blood cells (RBCs) in every cubic millimetre of
blood; 20–30 trillion of them in each person.
Every
day about 1% of these are changed. New RBCs take about 7 days to form in the
bone marrow, and are produced at the staggering rate of about 2 to 3 million
every second.
Each
RBC lasts about 120 days before its components are recycled to form new RBCs.
During
its 4-month lifetime, each red cell travels some 500 km (300 miles) around the
body, passing through the heart about 14,000 times per day.
Most
of our blood vessels are the microscopic capillaries. If the blood vessels in
one person were laid end to end, they would be about 150,000 km (100,000 miles)
in length — enough to circle the earth at the equator about four times!
*All
figures are for a healthy adult
Two reasons have been suggested for this. First, the
relative size of RBCs (6–8 µm diameter and just 2 µm thick) and capillaries
(tiny blood vessels) is such that red blood cells often have to deform in order
to squeeze through.
A nucleus (about 6 µm on average) could prevent passage of
the cell and make it get stuck, blocking the circulation.
Second, the shape and deformability of the red blood cell
is optimized for the carrying and delivery of oxygen, and it maximizes the
amount of hemoglobin that can be packed into the cell.
Nevertheless birds, which have a very high oxygen
requirement, do fine with nucleated RBCs, so there are other design features in
birds that compensate for this.
The system of the red blood cells giving oxygen to the
cells of the tissues is reversed when the red blood cell reaches the lungs,
where it gives up its carbon dioxide (though this is mostly carried by plasma)
and takes on a new load of oxygen.
At rest, all the blood (5 litres in an adult) completes a
circuit within a minute (spending 1 to 3 seconds in the capillaries).
With exercise, circulation is as quick as every 10
seconds. Having a molecule such as hemoglobin which can handle oxygen so
quickly and reversibly, when required, is amazing.
Conclusion
So, is the life of the flesh in the blood? Although not
confirmed by science until modern times, this statement from Leviticus 17:11 has always been true.
Blood actively maintains life by providing a vital
function for all cells, tissues and organs, and thus the life of the whole
body.
The more we find out about the astounding functional
design and complexity of blood, the more marvellous it becomes to us, and the
more honour and praise is due its Creator.
The
function of the blood clotting system is to prevent the escape of blood from a
damaged vessel. To do this, the blood has a special and very complex repair
procedure in place.
Once
initiated by a cut, the first component in the process is activated, which in
turn activates the next component, and so on, in a series of cumulative,
mutually-dependent steps.
This
physiological chain of production, or cascade, results in the formation of a
solid obstruction (a clot) in order to seal over the damage.
Some
of the main components of the clotting cascade are the proteins fibrinogen,
prothrombin, Stuart (anti-hemophilic) factor and proaccelerin. None of these
are used for any other purpose in the blood.
The
system is very finely tuned to result in a repair process that achieves just
the repair needed at just the right place and time to stop bleeding and begin
the process of healing.
Importantly,
the process is also self-limiting to ensure that coagulation (clotting) of the
entire blood supply does not occur.
The
Intelligent Design advocate Michael Behe, in his book Darwin’s Black
Box, has noted that the clotting cascade is an example of irreducible
complexity.
The
removal or degradation of just one, any one, of the components or steps would
cause the cascade to fail. Obviously, this would have dire consequences for the
organism.
It
is exceedingly difficult to see how the clotting cascade could have evolved, as
any postulated simplified or ‘primitive’ version of the process would result in
failure.
Andrew Hodge, M.B., B.S., Fracs
Dr Hodge is retired from his
former post as Head of the Cardiothoracic Surgical Service at the Fremantle
Hospital in Western Australia. A long-time supporter of Creation
Ministries International, he has written for both Creation magazine
and Journal of Creation.
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