Human Body^129
Integumentary Hair, skin, and nails protect the body from germs,
system injury, heat loss, and drying out.Skeletal A framework of bones and connective tissues that
system supports the body and, with muscles, enables it to move.
Muscular The system of muscles (involuntary and voluntary) that
system contract to make the body move.
Nervous The brain, nerves, sense organs, and related tissues
system enable the body to detect and respond to changes.
Endocrine A system of glands that regulates body processes by
system secreting chemicals, called hormones, into the blood.Circulatory The heart and blood vessels transport blood to the
system body’s cells to deliver nutrients and remove waste.Lymphatic A system that returns body fluids to the bloodstream
system via nodes, where the fluids are screened for germs.Immune An internal defence mechanism, consisting of cells and
system tissues that destroy invading germs and abnormal cells.Respiratory The lungs and airways leading to the lungs, which
system take oxygen into the body and expel carbon dioxide.
Digestive The mouth and most of the abdominal organs work to
system break down food into molecules the blood can absorb.
Urinary The kidneys remove unwanted chemicals from the blood
system and expel them via the bladder and urethra.
Reproductive The organs involved in sexual reproduction – the penis
system and testes in men; ovaries, uterus, and vagina in women.WHAT ARE ORGANS MADE OF?
Every organ contains several different tissues. The
stomach, for example, consists mostly of muscle cells,
which contract to churn food around. The inner lining
of the stomach is made of epithelial tissue, which is
continually worn away and replaced. There are also
glands that secrete digestive juices, blood vessels,
nerves, and connective tissue to hold it all together.HOW IS ULTRASOUND USED?
Ultrasound scanning is one of the most common
imaging techniques. High-frequency sound
waves are bounced off internal organs and
the pattern of echoes is displayed on
a TV screen. Ultrasound scanners are
good for studying moving liquids, such
as blood or fluid in the uterus (womb).WHAT IS A CT SCAN?
A computed tomography (CT) scan is a computer-
generated image built from X-ray beams. A machine
slowly moves over the area of the body examined,
taking X-ray pictures from many angles. A computer
then analyses the X-rays to build up a detailed cross-
section of the body, including its soft tissues.DO X-RAYS SHOW ONLY BONES?
No, X-rays can also be used to look at soft tissues,
such as the breast or blood vessels, to check if
they are healthy. For blood vessels, a harmless
dye that absorbs X-rays is first injected into the
vessels – X-rays will then show their outline.
This type of image is called an angiogram.HOW DO ORGANS WORK TOGETHER?
Organs work together in teams, called systems, to
carry out tasks. For instance, the stomach, intestines,
and pancreas are part of the digestive system,
breaking down food into molecules that the body can
absorb. Some systems work together – the skeletal and
muscular systems combine to enable us to move.Modern imaging techniques enable doctors to see inside the body
without cutting it open. There are many different techniques, each
suited to looking at particular tissues or processes.Tissues are grouped together into larger
structures called organs, which carry out
specific tasks. The heart, for instance,
is an organ designed to pump blood.FIND OUT MORE. Cells 73 • Genetics 209 • Mammals 120–123
IMAGING
X-RAY OF BROKEN ARM 1
This X-ray shows the badly
fractured (broken) radius and
ulna bones of the forearm.
X-rays are a form of radiation
that passes through soft parts of
the body, but shows up dense
material such as bones and teeth.4 ULTRASOUND OF A FOETUS
Ultrasound scanners are routinely used to
monitor unborn babies, to check their growth
and the development of organs, such as the heart.1 PET SCAN OF THE BRAIN
Positron emission tomography
(PET) uses injected radioactive
substances to reveal activity in
organs and tissues. The coloured
areas above show the parts of
the brain used during speech.ORGANS
Muscles
(in blue) enable the
body to move
BODY SYSTEMSbody