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B5: The Living Body
•Exoskeletons in animals such as insects,
arthropods, are made from Chitin.
•Internal skeletons in mammals are made of bone,
which is formed by calcium and phosphorous.
•Some vertebrates like sharks have internal
skeletons that are made from cartilage. This makes
the shark more flexible, and it also makes them
more buoyant, because cartilage is less dense than
bone.
•Human skeletons start off as cartilage. Over time
calcium and phosphorous replace the cartilage,
forming bone.
•This process is called OSSIFICATION.
•Humans are left with some cartilage art the end of
long bones, nose and ears. Hoe much cartilage is
left indicates how much a person has left to grow.
Structure of a long bone
•Cartilage absorbs
• The spongy texture of the cancellous bone
shock and helps bones
compromises strength and it being light enough to
to slide over each
move easily. This stores the red bone marrow,
other.
where red blood cells are made.
•In the marrow cavity, yellow bone marrow is held, •When bones become
demineralised, they
where white blood cells are made.
become brittle and
•Long bones such as the femur are hollow. Their
prone to fractures. This
strength comes from the compact bone, which is
is called
dense.
OSTEOPEROSIS.
B5: The Living Body
• Cartilage reduces friction and acts as a shock absorber.
•Ligaments join bones to bones
•Tendons join bone to muscle, enabling movement
•Synovial membrane produces synovial fluid which lubricates the joint
There are FIXED JOINTS like the hip girdle and the
vertebral column.
There are MOVEABLE JOINTS like the knee.
BALL AND SOCKET JOINTS allow movements
forwards, backwards and sideways, like the hip and
shoulder.
HINGE JOINTS allow movement in only one
direction, the knee and elbow for example.
Circulatory systems
•
Animals like Amoeba are so small that all
parts of their body can get oxygen
without them needing to have a blood
circulatory system.
Some animals, such as insects do not have
lungs. The oxygen is taken straight to the
cells through special tubes. Insect blood
does not carry oxygen and it does not
travel in blood vessels. This is an OPEN
CIRCULATORY SYSTEM.
• Fish have a SINGLE CLOSED
CIRCULATORY SYSTEM. Their blood
picks up oxygen form the gills and then
the blood travels in a single circuit. This
is a SINGLE CIRCULATORY SYSTEM.
• All humans have a DOUBLE
CIRCULATORY SYSTEM, the blood goes
round in two circuits; from the heart to
the lungs, then from the heart to the rest
of the body.
ARTERIES, VEINS and
CAPPILARIES are the blood
vessels.
A closed circulatory system
is when blood in blood
vessels carry oxygen around
the body. An open system
can be found in an insect and
is where blood does not
travel in blood vessels and
does not carry oxygen.
The Heart and the
Cardiac Cycle
The pacemaker of the heart consists of two groups of cells, the SINOATRIAL NODE and the
ATROVENTRICULAR NODE. They produce electrical nerve impulses which make the heart beat.
The Cardiac Cycle
1.
Blood flows into the atria from the Vena
Cava and pulmonary veins.
2.
A small electrical current is created by
the SAN.
3.
The current spreads through the muscle
cells of the atria making them contract.
Blood is forced into the ventricles.
4.
The current then stimulates the AVN to
produce an electrical impulse.
5.
The current spreads through the muscle
cells of the ventricles making them
contract.
6.
Blood flows into the aorta and pulmonary
veins.
7.
The cycle begins again as blood flows
into the atria.
The P wave is the impulse causing atria
to contract. QRS is the impulse causing
ventricles to contract. T is the recovery
before the next heartbeat.
Electrocardiograms
•Electrocardiograms (ECGs) are used to record the electrical impulses
produced by the pacemaker cells in the heart.
•ECHOCARDIOGRAMS are another way doctors can investigate heart
functions.
•An echocardiogram is an ultrasound scan of the heart. This can be used
to detect valve problems in the heart, holes in the heart and artery
blockage.
These ECGs show irregularities in the heart beats
of the patients. The ECG on the left is that of
somebody who has had a heart attack – this is
diagnosable because of the upside down T wave.
The ECG below is that of somebody with
Tachycardia, because the waves are of variable
heights and there is a high frequency of waves.
This means that the heart is beating faster than
normal, and the strength of the electrical impulses
sent tot the ventricles is varying.
•The heart rate varies depending on your level of physical activity.
•When the heart beat increases, it supplies oxygen more quickly to
muscles that need them.
•The stimulus of this heart beat increase is CO2. This is produced
as muscles work, and the heart beats faster to get the CO2 out of
the body.
•The hormone ADRENALINE can also increase the heart rate. It is
released into the bloodstream at certain times, when we are
stressed or excited for example.