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SPRING 2015
cranium
oesophagus
striated
muscles
thoracic duct
diaphragm
phalanges
THE
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ISSUE
metatarsals
Spring 2015
uman
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I n t h is is s u e :
Editor: Freyja Taylor-Law
Design and art direction: Max Plathan
Address: Potential Plus UK, Suite 1.6,
Challenge House, Sherwood Drive, Bletchley,
Milton Keynes, MK3 6DP
Tel: 01908 646433
Email: [email protected]
Copyright 2015 Potential Plus UK. All rights
reserved. IGNIS is published by Potential
Plus UK (operating name for The National
Association For Gifted Children). Should you
wish to use articles or other material from
IGNIS we are happy to consider requests and
will require full source acknowledgement.
2
IGNIS
14–15
the lymphatic and
immune systems
the digestive system
4–5 systems of the body
6–7
the skeletal system
16–17
8–9 the muscular system
18–19 the urinary system
10-11 the circulatory system
12
the respiratory system
13
the nervous system
20
the endocrine system
21 the human body quiz
22 cool websites and
quiz solution
LIBROPHILIA
The Concise Human Body Book: An Illustrated Guide to
Its Structure, Function and Disorders
By Dorling Kindersley and Medi-Mation
Take an interactive tour of your body with this compact guide,
amazing 3D images reveal all your major systems in molecular
detail. Discover how the nervous system works, the intricate
construction of skeleton and muscles, and how your body protects
itself when you are under threat. Put yourself under the microscope
to see the body’s processes in action from a nerve impulse to blood
surging through an artery. Journey inside and examine what can
go wrong with the human machine: explore the causes for and
symptoms of diseases and ailments. An unmissable in-your-body
adventure, perfect for students and families.
The Complete Human Body
By Alice Roberts and Medi-Mation
Get under your skin with this access-all-areas guide to the human body.
Discover a breathtaking portrait of the human body as it’s never
been seen before, using the latest medical and microscopic
imaging. The Complete Human Body covers the development,
form, function and disorders of the human body, all brought to life
by incredible state-of-the-art 3D computer-generated artworks.
Take a detailed look at how your respiratory system works, discover
the anatomy up-close and learn about over 200 diseases and how
they afflict the human body. Perfect for students and families.
Body: An amazing tour of human anatomy
by Robert Winston
A jaw-dropping tour of the anatomy from Robert Winston, awardwinning author and TV presenter. From how your blood flows
through the heart to how your food is digested, take a trip
through your very own body and be astounded by its inner
workings. A free interactive CD shows the body and it’s
movements in 3D detail and acetate pages fold back to reveal
how our most important organs work. An irresistibly graphic,
top-to-toe body atlas.
IGNIS
3
Systems of the Body
Your body has various systems that perform different functions
and they all work together. These functions range from creating a
new human being to absorbing nutrients and getting rid of waste.
The Skeletal System
This solid structure of bones is supported
by cartilage and ligaments. It supports the
body and gives it its shape. This system also
protects the internal organs and allows us to
move. Red blood cells (erythrocytes) are also
generated by the skeletal system.
The Muscular System
The main function of the muscular system is
to produce movement and to help to hold the
shape of the body. The muscular system is
made up of muscles, organs made of fleshy
tissue and contractile cells. There are two main
types of muscle; smooth and striated. Smooth
muscles are controlled by the brain, but their
movement is not voluntary. Striated muscles
on the other hand control voluntary movement
and they are attached to bones. Finally,
there is the muscle tissue of the heart, called
myocardium, which is entirely unique and its
own separate class.
The Circulatory System
Blood is carried to and from the heart by the
circulatory system, as well as to the organs
and all of the cells in every part of the body.
The heart pushes blood though the arteries
and collects it back via the veins.
4
IGNIS
The Respiratory System
We need oxygen from the air in the outside
world and the respiratory system brings air
into our body through the upper airways and
then the lungs absorb the oxygen and expel
the carbon dioxide. This oxygenated blood
is sent to all of the cells in the body by the
circulatory system, and blood that needs
purifying returns to the lungs.
The Nervous System
The brain and the spinal cord make up the
central nervous system. There is a peripheral
nervous system made up of spinal nerves
and cranial nerves. These two systems send
sensations (from both inside the body and
outside) to the brain where they get processed
and responded to.
The Lymphatic System
This system has two main jobs – to defend
the body against foreign organisms and to
transport interstitial fluid and substances from
the digestive system into the bloodstream
through the lymphatic drainage system.
The Digestive System
The digestive system is the path your food
takes from your mouth to your rectum and
anus. It includes the pharynx, oesophagus,
stomach, small intestine and large intestine.
The liver and pancreas help process
the ingested food to extract chemical
components. These can be welcome nutrients,
which are used by the body whilst others are
discarded.
Urinary System
This system keeps the body’s internal systems
in equilibrium, or homeostasis. It regulates
the amount of water in the body, discarding
any substances that are toxic or in surplus.
The main organs are the bladder and kidneys,
with the ureters transporting the urine from
the kidneys to the bladder, and the urethra
carrying the urine out of the body.
Endocrine System
This system is made up of the glands in your
body. It produces the body’s messengers
– hormones – which are secreted into the
bloodstream so they can head to the organ
they are sent to excite, stimulate or influence.
Reproductive System
Female
The internal organs of a woman's reproductive
system are the vagina, uterus, ovaries and
fallopian tubes. The function of these organs
is to produce ova and facilitate the fertilisation
of ovum by a spermatozoon and once this has
occurred a pregnancy results.
Male
The male reproductive organs contribute one
of the two cells needed for creating a new
human being. Two testicles and a penis are the
main organs.
IGNIS
5
The Skeletal System
This strong, resistant structure is made up of bones
and supporting cartilage and ligaments. Our form
and structure comes from our skeletal system, and it
protects our internal organs. We are also able to move
because of our skeletal system, in conjunction with our
muscular system. The bone marrow within the centre
of bones also produces blood cells.
There are several types of bones,
which are generally classified into
the following groups:
Clavicle
Humerus
Long bones
These are bones such as the femur. They are
longer than they are wide, and are the main bones
in the limbs. These bones grow more in childhood
than the other types and are responsible for most
of our height. They tend to have a central section
which lies between two end points called the
epiphyses.
Radius
Ulna
Short bones
These are bones such as the heel bones which are
about as long as they are wide and can often be
round or cubed in shape.
Flat bones
Femur
The ribs, hips and most bones of the cranium are
flat bones. They range in size and shape but they
are all very thin in one direction.
Irregular bones
These take various shapes that don't fit the pattern
of long, short or flat bones. For example the
coccyx and wedge-like sphenoid bones in the skull
are irregular bones.
Fibula
Tibia
Sesamoid bones
These bones are small and round. These form after
birth to protect tendons from stress and strain at
the joint. The patella is a sesamoid bone.
Cuneiforms
Metatarsals
Phalanges
6
IGNIS
Cranium
Parts of Bone
s
periosteum
bone marrow
Ribs
compact bone
Vertebrae
Pelvis
cancellous
(spongy) bone
Carpal bones
Metacarpal bones
Phalanges
At birth, every long bone is made of three individual
bones separated by cartilage. Each end of the bone
is called an epiphysis and the middle bone is called a
diaphysis. These bones grow towards each other and
eventually fuse.
Patella
Calcaneus (heel bone)
Talus
There are several layers that make up a bone. The
outer layer of periosteum is dense, connective tissue.
Inside the periosteum is the compact bone which is
one of the hardest materials in the body. It is made
of a matrix of hard mineral salts, reinforced with
tough collagen fibres. Beneath the compact bones
is the spongy bone. This is a network in the form
of a honeycomb. The bone tissue grows in columns
called trabeculae. There are spaces for bone marrow
in between these columns. Long bones also have a
hollow medullary cavity in the middle of the diaphysis
where red bone marrow is contained in childhood,
turning into yellow bone marrow in maturity.
IGNIS
7
The Muscular System
Your muscular system is responsible for the movement in your body.
You have three main types of muscle in your body – striated, visceral and cardiac.
Striated Muscles
Striated muscles are the muscles attached
to your skeletal system and there are
around 650 named muscles that fall into this
category, which make up almost half of your
body weight! They are the only voluntary
muscles in your body, which means they
are controlled consciously. Every action you
choose to perform, such as walking, running,
speaking, sitting is controlled by these
striated muscles. The fibres in striated muscle
are very strong and they contract rapidly.
The purpose of these muscles is to contract in
order to move parts of the body closer to
the bone that the muscle attaches to.
Most are attached to two bones by a tendon,
8
IGNIS
across a joint, and the muscle brings these
two bones closer - think of your arms or legs
bending. A tendon is a tough band of dense
connective tissue which attaches the muscle
to the bone firmly.
Striated muscles often do not work alone.
They tend to work in pairs or groups to
produce the movement your body requires.
For example, your upper arm muscles
are called your biceps and triceps. When
your biceps (on the front of the arm) are
contracted, your triceps (on the back of your
arm) are relaxed – this lifts your forearm up.
When you wish to put your forearm down,
your triceps contract and your biceps relax.
Visceral Muscles
Visceral, or smooth muscle, is found on
the inside of organs such as your blood
vessels, stomach and intestines. Visceral
muscles contract to move substances
through the organ – such as food, waste
and blood. It is the weakest type of
muscle tissue, and it is controlled by the
unconscious part of your brain – you can't
control what it does just by thinking about
it! This muscle type is often referred to
as 'smooth' as it appears smooth when
looked at with a microscope, which is very
different to the banded appearance of
skeletal and cardiac muscle.
Cardiac Muscle
Cardiac muscle is also striated, like
skeletal muscle – they have dark and
light stripes when looked at under a
microscope. This tells us that the muscle
is extremely strong (like skeletal muscles),
unlike the visceral muscles in our organs.
Cardiac muscle is found exclusively in
the heart and its job is to pump blood
throughout our whole body. Again, these
muscles are involuntary – we cannot
control them just by thinking about it.
Although there are hormones in your
body and signals from your brain that tell
your cardiac muscle to change the rate
at which it is contracting, your cardiac
muscle tells itself when to contract. You
have a 'pacemaker' in your heart, which
tells the other cardiac muscles when to
contract. This pacemaker is also made
of cardiac muscle tissue. Because the
muscle tissue can tell itself to contract,
it is considered to be 'autorhythmic'.
IGNIS
9
The Circulatory System
The function of your circulatory system is to carry
your blood to and from all of the organs in your
body. It consists of your heart, blood vessels and
all of the blood in your body (around 5 litres). By
transporting the blood around your body, it is
ensuring that oxygen, nutrients, hormones and
waste products are transported throughout the
body to the correct places. The circulatory system
is powered by your body’s hardest working organ
– your heart – this is your body’s engine.
Blood Vessels
Blood vessels are your body's transport systems
– they allow blood to flow quickly from the heart
to every area of your body and back again. The
amount of blood flow that passes through the
vessel will determine the size of the blood vessel.
All blood vessels contain a hollow area through
the middle where the blood is able to flow – this
is called the lumen. Surrounding the lumen is
the wall of the vessel, which can be thin or thick,
depending on the function of the vessel.
The Heart
The muscula
r pumping o
rgan, located
between you
r lungs in the
middle of yo
chest is your
ur
heart. The ve
ry bottom tip
of your heart
is called its a
pex, and this
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g
that about tw
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o
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ted on your
side, with th
left
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on your righ
heart has fo
t. Your
ur main cham
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right atriums,
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which are on
the top half
your heart, a
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nd the left a
nd right ven
which are on
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alf of your h
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TO YOUR BO
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right atrium
NGS
left atrium
FROM LUNG
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There are three main types
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TO YOUR LU
BODY
right ventricle
the septum
left ventricle
ARTERIES AND ARTERIOLES
Arteries are muscular elastic blood vessels that
bring oxygenated blood from the heart to all of
the cells of the body. The blood is usually highly
oxygenated. Blood is pushed into the arteries
with great force, and arteries need to be able
to withstand this. Therefore, artery walls are
much thicker, more elastic and more muscular
than other vessels. There are smaller arteries
that are more muscular in their walls as they
contract and expand in order to regulate blood
flow to different parts of the body depending on
circumstances.
Arterioles are even narrower arteries that
branch off from arteries and carry the blood into
capillaries. The blood pressure in arterioles is
lower than in arteries, as there are more of them,
less blood flowing through them, and they are
further from the heart. These arterioles are also
capable of controlling the blood flow through
them, regulating blood flow and pressure.
10 IGNIS
VEINS AND VENULES
Veins are the conduits that transport
deoxygenated blood back to the heart after it
has travelled to different areas of the body. They
are the blood counterparts of arteries. Because
it is the arteries, then the arterioles, then the
capillaries that absorb the force of the heart's
contractions, by the time blood gets to veins
and venules, there is very little blood pressure.
This means veins can have thinner walls with
less elasticity. Some veins have one-way valves
which prevent blood from flowing back away
from the heart, forcing the blood to travel in only
one direction. As skeletal muscles in your body
contract and move, they squeeze veins and help
push the blood through those valves and back
to your heart. Venules are similar to arterioles
in that they are small vessels, but instead of
connecting to arteries they connect to veins.
CAPILLARIES
These are the branchin
are the smallest and th
and also the most comm
in your body has capilla
it. Capillaries connect to
and venules on the oth
crucial to the exchange
waste and so they mus
to the cells of the tissue
exchange.
Blood
Did you know that your body contains around 5 litres of blood? Your blood is technically a liquid
connective tissue – it transports many substances through your body and helps to maintain
homeostasis - the control of your internal conditions such as nutrient, water, waste and gas levels.
Your blood is made up of red blood cells,
white blood cells, platelets and liquid plasma
(which is actually yellow!)
red blood cells
white blood cells
platelets
Fo r ev ery cu bi c
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4,5 0 0 -11,0 0 0
15 0,0 0 0 - 4 0 0
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O n an av erag e da
plasma
Red blood cells are biconcave – they are like discs
with a curve on both sides into the middle, so that
the centre is the thinnest part. This means they can
bend and take on a bell shape to
pass through the thinnest blood
vessels. It also gives them a high
surface area to volume ratio.
Immature red blood cells begin
ngs of the arterioles. They
with a nucleus, but this is pushed
hinnest blood vessels
mon. Nearly every tissue
out of the cell when it is fully
aries running through
mature, to make it as flexible as
o arterioles on one end
it is and give it its shape. This
her. These capillaries are
does however mean that they
e of oxygen, nutrients and
carry no DNA, meaning that they
st carry blood very close
es in order to make this
cannot repair themselves when
they become damaged.
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10,0 0 0 m ill io n
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Red Blood Cells
Red blood cells are also known as erythrocytes,
and are the most common type of blood cell and
make up around 45% of your blood. They are known
as phantom cells as all that they contain is a large
amount of haemoglobin – a protein that has a great
affinity for combining with oxygen. Red blood cells
cannot reproduce themselves, and must be replaced
by new blood cells that are produced inside of red
bone marrow from stem cells at the amazing rate of
about 2 million cells every second!
yo u have :
n re d bl oo d ce lls
te bl oo d ce lls
io n pl atel ets
White Blood Cells
White blood cells are also known as leukocytes.
These make up only a small percentage of the total
number of cells in your blood stream. However,
white blood cells are extremely important to your
body's immune system.
There are two major classes of white blood cells:
Granular leukocytes
There are three types of granular leukocytes;
neutrophils, eosinophils and basophils. Neutrophils
contain digestive enzymes that neutralise bacteria
invading the body, eosinophils contain enzymes
that digest viruses that antibodies in the blood have
bound to and basophils release histamine in order to
intensify allergic reactions, protecting the body from
any parasites.
Agranular leukocytes
There are two main types of agranular leukocytes
– monocytes and lymphocytes. Monocytes develop
into microphages and engulf and ingest pathogens
from infections and wounds. Lymphocytes include B
cells that produce antibodies to fight of infections by
pathogens and T cells that fight off viral infections.
IGNIS
11
The Respiratory System
The main function of the respiratory
system is to supply your blood with oxygen
so that the blood can deliver this oxygen
to all parts of the body. We do this through
breathing - we inhale oxygen and exhale
carbon dioxide, both of which are usually
involuntary and automatic. This exchange
of gases is the respiratory system’s way of
getting oxygen to the blood.
When you breathe in, the air enters in through
your nasal cavity or mouth. It is then warmed
and cleaned. From there it heads through the
pharynx, where your tonsils intercept any harmful
organisms and destroy them.
From here, the air then passes through your
larynx. The epiglottis, the upper part of the larynx,
stops food from going through into the larynx
when you are swallowing. The air then follows into
the oesophagus.
As it goes down the air reaches the trachea, also
known as the windpipe, which is a tube lined with
cilia that transports the air in and out of the lungs.
The trachea has rings of cartilage all the way along
it that prevent it from being squashed or crushed.
Cilia are special hairs that prevent dust or dirt
getting into the lungs. They move back and forth,
carrying mucus up and out. Mucus, which is a
sticky fluid, collects the dust and we expel it when
we sneeze, cough, spit or swallow.
The trachea branches out into two main bronchi,
and each of these is divided into smaller branches,
called bronchioles, and then into pulmonary
alveoli, which are like little sacks where the gases
are exchanged.
The oxygen passes into the blood at the alveoli
and then is transported to the tissues all over the
body. The carbon dioxide passes back from the
bloodstream into the alveoli to travel back up and
be exhaled.
12
IGNIS
Your diaphragm is a sheet of muscles that lies across
the chest cavity – it helps to push the carbon dioxide
out and pulls the oxygen in. As the diaphragm contracts
and relaxes, breathing takes place. When the diaphragm
contracts, oxygen is pulled into the lungs. When the
diaphragm relaxes, carbon dioxide is pumped out of
the lungs.
Why do we yawn?
When you are too tired, your lungs do not take in enough
oxygen from the air you inhale. This means you do not
have enough oxygen coming into your body, and when
your brain senses this shortage, it sends a message that
causes you to take a big long breath, or a yawn!
Why do we sneeze?
Sneezing is a bit similar to a cough, it helps to remove
something that is irritating the mucous membranes of
the nose.
What are hiccups?
This is when your diaphragm suddenly moves, and this
is involuntary. This can happen if your diaphragm gets
irritated, you eat too quickly or many other things. When
you breathe in, the air enters in through your nasal cavity
or mouth. It is then warmed and cleaned. From there it
heads through the pharynx, where your tonsils intercept
any harmful organisms and destroy them.
The Nervous System
Your nervous system is the most complex system
in your body – much of which is still a mystery
to us. Your nervous system is what controls
your whole body and also manages all of your
intellectual activities such as memory, choice and
emotions. The nervous system consists of the
brain, spinal cord, sensory organs and all of the
nerves which connect to the rest of the body. The
central nervous system consists of the brain and
spinal cord and the peripheral nervous system
consists of the sense organs and sensory nerves.
The Central Nervous System (CNS)
The Peripheral Nervous System (PNS)
Your brain consists of a cerebrum, cerebellum
and spinal bulb. Your spinal cord along with your
brain receives information from your sense organs
and sends out instructions to all of your muscles
and other organs. The central nervous system is
also responsible for processing and coordinating
nervous signals that are transmitted from the
peripheral nervous system.
The peripheral nervous system provides
information to the central nervous system and also
coordinates your movement. It informs your CNS
about external changes detected by your senses
and internal changes such as having a full bladder.
It sends instructions for your conscious movement
such as walking, sitting, running and also controls
the functioning of your internal organs.
Neurons
Cells of the nervous system are called neurons.
They transmit impulses in the form of electrical
signals and carry information to the brain.
Your brain has around 100 billion neurons
that come in many different shapes and sizes.
Each neuron in your brain can be connected
with several thousand other neurons and can
receive up to 100,000 signals a second. They
are similar to other cells in your body in many
ways, but they are also very different. Neurons
have special cell parts called dendrites and
axons. Dendrites are the branches through
which a neuron receives signals from other
neurons. There can be around 200 dendrites
per neuron, but this varies. The axon is the
nerve fibre that transmits impulses.
There are three main types
of neurons, based on how
complicated their axons and
dendrites are:
1. Unipolar
These have two branches of
the same axon that extend
from one cell body
2. Bipolar
These neurons have two
completely separate axons
that extend from each end
of a cell body
3. Multipolar
These have one axon with
a number of dendrites
extending from a cell body.
IGNIS
13
The Lymphatic and Immune Systems
The lymphatic and immune systems, although
technically two different systems, are very closely
related. The immune system is our defence system
– it defends us against foreign organisms, bacteria,
fungi and parasitic animals. The lymphatic system is
a system of nodes, capillaries and vessels, along with
other organs, that transport a fluid called ‘lymph’
from the tissues as it returns to the bloodstream.
The lymphatic tissue in these organs filters and
cleans the lymph of debris and pathogens. The
lymph also contains cells called lymphocytes and
macrophages which are part of your immune system.
Invaders
The types of invaders your immune system and
lymphatic system are trying to fight off are:
Protozoa
There are also living organisms that
normally live in the soil or water.
They can produce a range of diseases
including malaria and diarrhoea.
Bacteria
Bacteria are life forms found in billions
everywhere you look. Not all bacteria
are harmful but bacteria known as
germs are pathogenic and release
poisonous substances called toxins.
Viruses
Viruses are not living things, they are
more like chemical packages. They
are made up of genetic material and
when they enter the body they invade
a cell and then reproduce and spread.
14 IGNIS
Immune Response
Your lymphatic system generates
cells called lymphocytes, which are
also found in your blood, as well as
macrophages. These are what make up
your immune system. B lymphocytes
learn information from the surface
of invading bacteria that they use
to recognise other similar bacteria
and Macrophages engulf and ingest
invading bacteria.
When a pathogen is recognised,
B lymphocytes are activated and
begin dividing themselves into memory
cells and plasmatic cells. Memory cells hold on to
the antigen information and when there is a new
invasion they begin dividing rapidly in order to
deal with it. The plasmatic cells secrete thousands
of special antibody molecules per second, which
the blood then carries to wherever the infection is.
The antibodies are also known as immunoglobin
and they are special protein molecules that are
the shape of a Y. Each Y's arms are unique to a
particular type of antibody, and each specific
antibody attaches with these arms to a specific
antigen. These antibodies are there to mark out
invaders so that macrophages can destroy them.
Lymphatic Network
As your blood passes through the tissues in your
body, it enters capillaries to transfer nutrients,
gases and waste. Blood plasma also diffuses
through the capillary walls and enters the spaces
between cells in the tissue. Although some of
this plasma diffuses back into the blood, some
of the fluid becomes embedded. To prevent the
build up of these excess fluids, small vessels
called lymphatic capillaries also extend into these
tissues to absorb these fluids and return them
back to circulation around the body. This liquid
left in the tissues is called lymph. Lymph is very
similar to plasma – it is mostly water and contains
proteins, cellular waste and hormones. It also
contains bacterial cells that are picked up from
diseased tissues in the body, as well as the white
blood cells that are fighting these pathogens.
The vessels that transport this lymph (lymphatic
capillaries) are similar to veins. They have thin
walls and valves to help move fluid under low
pressure. The skeletal muscles also help to push
lymph back through the capillaries in the same
way as veins.
Lymph Nodes and Ducts
These are small, round glands about 1 centimetre
in diameter. They are distributed throughout the
body – in your neck, armpits, groin and behind
your knees, as well as around your thorax and
abdomen. These lymph nodes work like filters
for the lymph that arrives at them from several
lymph vessels. There are special fibres inside the
lymph nodes that act like a net to catch any cells
or debris that are in the lymph. Macrophages
and lymphocytes in the lymph node attack and
kill microbes that get caught inside. The filtered
lymph is then carried out of the node towards
lymph ducts. There are two main lymph ducts –
the Thoracic duct and the Right Lymphatic Duct.
These return lymph back to the blood supply so
that it can be recirculated as plasma.
Other External Defences
As well as your lymphatic and immune system,
you also have some natural external defences that
aim to prevent infections before they get inside
your body. Your skin is your first defensive barrier
that is there to protect you. You also have various
glands that secrete mucus, tears, saliva and
sebum which trap, move and can kill bacteria.
Your stomach acid also kills microbes found on food.
IGNIS
15
Six ma
take pl
The Digestive System
1. inges
2. secre
3. mixin
4 . diges
5. absor
6. excre
Your digestive system is a group of organs that work
together to transform food into fuel for your entire
body. You begin by ingesting food through the mouth
and oesophagus, continue digestion in your stomach,
small intestine and large intestine, and then your
faeces are evacuated through your rectum and anus.
1
YOUR MOUTH
1
This is where your food first arrives – the oral cavity.
Your tongue, teeth and salivary glands all aid in the
digestion of your food. The tongue and teeth are the
very first specialists that your food encounters. Your
tongue tastes and positions the food, which is then
cut and ground by your 32 (adult) teeth. Your saliva
moistens the food, and also begins digesting the
carbohydrates, while the palate prevents food from
passing up into your nose. The tongue then pushes the
chewed food (or bolus) to the back of your oral cavity
and into the pharynx.
2
YOUR THROAT
Your throat, also known as your pharynx, is a funnel
shaped tube that connects from your mouth to your
oesophagus. It passes the chewed food to your
oesophagus, but also contains a flap of tissue called
your epiglottis, which acts as a switch to send food to
the oesophagus and air to the larynx.
3
OESOPHAGUS
This thick muscular tube is part of the upper
gastrointestinal tract. It carries the food down into
the stomach using peristalsis – a wave like muscular
motion. It has a sphincter muscle at the bottom, which
is a muscular ring, which prevents food coming up
from the stomach.
16
IGNIS
3
7
6
5
ajor function
s
lace:
stion
etion
ng and movem
ent
stion
rption
etion
2
4
STOMACH
5
SMALL INTESTINE
6
THE LIVER
7
THE GALLBLADDER & PANCREAS
8
THE LARGE INTESTINE
This is the first section of the digestive system that is located
in the abdomen. It is the shape of an empty bag, curved like
a bagpipe. In a normal person, your stomach is about the
size of two of your own fists alongside one another. It is a
storage tank for food so that your body can digest it properly.
Gastric juices and enzymes subject the swallowed food to
intense chemical reactions whilst also mixing it completely.
Peristalsis moves the food from the stomach to the
duodenum, which is the initial section of the small intestine.
This is a long, thin tube, around 10 feet long and an inch
in diameter. This is where the lower gastrointestinal tract
begins. It is all coiled up like a garden hose and its interior
surface is covered in millions of hairlike structures called
villi. Each has a lymphatic vessel and a network of vessels
delivering nutrients to it. The villi absorb nutrients and help to
increase the surface area of the small intestine – increasing
the absorption of nutrients.
Your liver is roughly triangular which is located to the right
of your stomach. It is the largest gland in the human body
and the second largest organ. The liver's main function with
regards to digestion is to produce bile and secrete it into the
small intestine. Bile helps with the digestion of fats. The liver
also regulates glucose levels, regulates the metabolism of
proteins and is a large blood filter, storing vitamins A, D, E and K.
4
8
The gallbladder is pear-shaped, small organ that stores and
recycles excess bile so that it can be reused. The pancreas is
a large gland that secretes digestive enzymes into the small
intestine that breaks down fats, proteins and carbohydrates.
This long, thick tube (about 2 ½ inches in diameter) is about
5 feet long. It absorbs water and contains bacteria that help
break down waste so that it can extract small amounts of
nutrients. The faeces then leave the large intestine through
the anal canal.
IGNIS
17
The Urinary System
The basic organs of the urinary system are the
kidneys, ureters, bladder and urethra. The function
of the urinary system is to regulate homeostasis –
keeping the equilibrium between chemicals in the
body and water. The kidneys produce and secrete
urine, which is eliminated from the body. It is
harmless and sterile and composed mostly of water
and salts, and around 2% urea. Ureters carry the
urine through the body to where it is stored in the
bladder, from which it is passed to the urethra, from
which it will be expelled from the body.
The Kidneys
These bean shaped organs regulate the amount of water and
minerals in the blood. They produce urine that carries away the
waste that the kidneys discard. It is their job to ensure that the
composition of the bodily fluids is constant. They also regulate
the pressure of the arteries. Around 1,750 litres of blood is
processed by the kidneys every day and around 1.5 litres of urine
is produced by them. Although they only account for 1% of your
total body weight, they consume 25% of your energy!
Each kidney contains around 1 million individual nephrons
– these are the microscopic functional units that filter the
blood. Arterioles in the kidneys deliver blood to a bundle of
capillaries surrounded by a capsule, which is called a glomerulus.
When blood flows through the glomerulus, lots of the blood's
plasma is pushed out of the capillaries and into the capsule.
The blood cells and a small amount of plasma are left to flow
through the capillaries, and the liquid pushed through into the
glomerulus flows through several tubules lined with filtering
cells, surrounded by capillaries. The cells absorb some water and
substances and return it to the blood in the capillaries, and then
the waste products in the blood are secreted into the fluid in the
capsule. At the end of the process, the filtrate in the tubule is
urine, containing just water and waste, and the blood exiting via
the capillaries has reabsorbed nutrients and most of the water.
18
IGNIS
Ureters
This pair of tubes carry urine from the kidneys to the urinary bladder.
They are around 11 inches long and run on the left and right side of
your body, parallel to your spine.
Urinary Bladder
This is another sac-like organ that is hollow in the middle, where it stores
urine. As the hollow space fills, the elastic walls of the bladder are stretched
to accommodate anything from 600-800ml of urine.
Urethra
The tube through which your urine passes out of your body from the
bladder is called the urethra. This is different in males and females. In
females, it is only around 2 inches long, and it ends just above the vaginal
opening. In males, the urethra is around 9 inches long, and ends at the tip of
their penis. In the case of males, the urethra is also part of the reproductive
system as it also carries sperm out of the body.
There are two sphincter muscles that control the flow of urine through
the urethra. The internal sphincter is made of smooth muscle and opens
involuntarily whenever the bladder reaches a certain level – this is what tells
us we need to urinate. The external sphincter is made of skeletal muscle
and we can open it to allow urine out or hold it closed to delay urination.
IGNIS
19
The Endocrine System
The endocrine system consists of all of the
glands inside the body that secrete around
50 hormones into the blood. The glands are
controlled by the nervous system as well as
by chemical receptors in the blood and other
hormones secreted from other glands! These
hormones activate and stimulate different
organs and control metabolism, reproduction
and development. The chemicals control lots
of the body’s processes.
The Hypothalamus
Adrenal Glands
The hypothalamus is part of the brain and it
serves many functions in the nervous system,
as well as controlling the endocrine system
through the pituitary gland. It has special cells
called neurosecretory cells which are neurons
that secrete hormones. The hormones it releases
affect the pituitary gland.
The hormone adrenaline is what wakes your
body up when you feel at risk or before you kiss
someone. This is produced by your adrenal glands,
which are found by your kidneys. It increases your
cardiac rhythm, the pressure in your arteries and
the flow of blood to your muscles.
The Pituitary Gland
The pituitary gland is also known as the master
gland as it controls the rest of the endocrine
glands. It has an anterior lobe and a posterior lobe.
It is a small pea-sized lump of tissue connected
to the hypothalamus. There are lots of blood
vessels surrounding it to carry the hormones that
it releases through the body. Your pituitary gland
is also associated with psychological behaviours
such as affection.
The Pineal Gland
This is a small mass of glandular tissue found
below the brain. It helps to regulate our sleep-wake
cycle, known as the circadian rhythm, by producing
melatonin. The pineal gland is told not to release
melatonin when the photoreceptors in your retina
are stimulated – when they receive light. When
you are in low light or darkness, the pineal gland
produces melatonin, causing you to feel drowsy.
20 IGNIS
The Pancreas
The pancreas increases the glucose level in your
blood before you kiss someone. It is in charge of
the two hormones that control your blood sugar
level – glycogen and insulin. Glycogen increases
the blood sugar levels in the bloodstream and
insulin lowers blood glucose levels after a meal.
Pheromones
These are chemical substances released
by the glands in your skin that are related
to sexual attraction. They transmit
sensations of excitation, attraction and
also, unfortunately, rejection.
Oxytocin
Oxytocin is the hormone that
influences basic body functions – birth,
breast-feeding and being in love. It is
commonly associated with affection
and tenderness, and it stimulates the
formation of bonds of affection.
Quiz
solutions o
n
the back p
age
Click a question to jump to the page
where you can find out the answer!
Q1. What are the three types of
muscle?
Q11. What are arteries?
Q2. What function does the
epiglottis have?
two types of muscle are
Q12. What
striated?
Q3. Which of these three groups
are not living things - Viruses,
bacteria and protozoa?
Q4. What vitamins does the liver
mainly store?
Q5. What is the function of a
ureter?
is the very bottom tip of
Q13. What
your heart called?
how many litres of
Q14. Roughly
blood are in your body?
is the technical name for
Q15. What
platelets?
What are epiphyses?
how much of plasma
Q16. Roughly
is water?
Q7. What percentage of your blood
do red blood cells make up?
how many red blood
Q17. Roughly
cells are made every second?
Q8. What is the technical name for
red blood cells?
shape are red blood
Q18. What
cells?
Q9. What are white blood cells also
known as?
Q6. are the two major classes
Q10. What
of white blood cells?
Q19. What are pheromones?
are the two hormones
Q20. What
that control blood sugar level?
IGNIS
21
!
s
e
t
i
s
b
e
Cool w
Healthline – Body Maps
www.healthline.com/human-body-maps
BodyMaps is an interactive visual search tool that allows users to
explore the human body in 3-D. With easy-to-use navigation, users
can search multiple layers of the human anatomy, view systems
and organs down to their smallest parts, and understand in detail
how the human body works.
Visible Body
www.visiblebody.com/index.html
This site holds a 'learn anatomy site', has free anatomy e-books and
anatomy apps to download. Visible Body's 3D anatomical models
of the human body are the foundation of their content. Their
award-winning and best-selling apps cover gross anatomy and
microanatomy, as well as physiological processes and pathologies.
National Geographic – Explore the Human Body
www.science.nationalgeographic.com/science/healthand-human-body/human-body/
The National Geographic human body site has videos, articles,
news, interactives, quizzes and photos. There really is a lot here to
investigate and satisfy your enquiring mind!
QUIZ SOLUTION:
1. Cardiac, visceral (or smooth) and
skeletal (or striated)
2. The epiglottis stops food from going into
the larynx
3. Viruses
4. A, D, E and K
5. The ureters are tubes that transfer urine
from the kidneys to the urinary bladder
6. Epiphyses are the two end points of a
long bone
7. 45%
8. Erythrocytes
9. Leukocytes
10. Granular leukocytes and agranular
leukocytes
11. Arteries are muscular elastic blood
vessels that bring oxygenated blood
from the heart to all of the cells of the
body.
12. Cardiac and striated/skeletal.
13. It’s apex.
14. 5
15. Thrombocytes
16. 90%
17. 2 million cells every second!
18. Biconcave
19. These are chemical substances released
by the glands in your skin that are
related to sexual attraction.
20. Glycogen and insulin.