Human Health And Systems Flashcards
ingesting/eating
Food is taken in by the body
Digestion
Food is broken down
Absorption
Digested food passes into the bloodstream
Assimilation
Using the food in the cells of the body
Elimination
Getting rid of the undigested food
Chemical digestion
Enzymes. Involves the use of chemicals called enzymes to break down food. Enzymes are chemicals that speed up reactions without being used up in the reaction
Substrate. Enzymes act on a substrate and break it down into a product
Plasma
Liquid part of the blood
Mostly water
Function: to transport chemicals and heat
Useful Chemicals food hormones
Waste Chemicals CO2 salts urea
Heat generated from chemical reactions transported around to maintain
Also carries red and white blood cells and platelets
Red blood cells
Round, flattened discs, curve inward
near centre
• Small, no nucleus, formed in bone
marrow
• Very numerous – approx 5million per drop
blood
• Function : transport oxygen to cells
• Red colour comes from haemoglobin
they contain.
• Haemoglobin picks up oxygen in the
lungs
• It later releases it in other parts - e.g.
muscle
White blood cells
Larger than Red Blood Cells
but fewer in number
• No definite shape – shape
can change
• They are also made in the
bone marrow
• Function : to fight infection
• Some can surround micro-organisms and destroy them
• Others produce proteins called antibodies
• Antibodies help to destroy micro-organisms such as
bacteria
Platelets
Smaller than red or white blood
cells
• They are formed in the bone
marrow
• They are formed from larger
cells breaking down into pieces
• Function: help to form blood
clots
• When a blood vessel is injured, platelets help to form a clot
• Clotting prevents loss of blood, and prevents micro-
organisms getting in
• Clots are temporary barriers while repair and healing is
taking place
System of tubes + pump
Blood being a fluid, needs tubes in
which to flow
• These tubes are called blood
vessels
• They come in three main types:
– Arteries
– Veins
– Capillaries
• Good blood flow requires the aid of a good pump
• In the human circulatory system this pump is the heart
• In an average lifetime, the heart beats more than 2.5 billion
times, without ever pausing to rest
Arteries
Carry blood AWAY from the heart
• Flow of blood is strong and at high pressure
• Artery walls are thick and strong to withstand this
pressure
• Blood is under pressure – forced to move in one direction
• There is no need for valves in arteries to prevent
backwards flow
• All arteries (except pulmonary artery) carry oxygenated blood
Veins
Carry blood BACK to the heart
• Flow of blood is weaker and pressure is low
• Vein walls are thinner and weaker than artery walls
• Pressure is low, so there is a danger of backward flow of
blood, especially when flow direction is against gravity
• Valves in veins at regular intervals, allow blood to flow
forwards, but prevent reverse flow
• All veins (except pulmonary vein) carry deoxygenated blood
Capillaries
These are tiny blood vessels
• There are a huge number of them in the body
• Capillaries are found between arteries and veins
• Capillaries have very thin walls which allow materials to
pass in and out with the surrounding cells and tissue
Heart
Is an organ about the size of a
clenched fist
• Function: pumps blood around
the body
• It pumps blood by contracting
periodically
• Cardiac muscle provides the
contraction
• Unlike regular muscle, cardiac muscle doesn’t tire easily
• Resting heart rate in adults is about 72 bpm(beats per minute)
• In exercise, the heart beats faster, so that the blood can
carry chemicals faster around the body e.g. Oxygen
Pulse rate
When the heart contracts, it
squeezes blood into the arteries
under pressure.
• As blood flows down the arteries,
surges of pressure can be felt where
the arteries are close to the surface
• Areas where it can be felt are:
– At the wrist
– Inner arm near elbow joint
– At the sides of the neck
• A surge of blood felt at these locations is called a pulse
• The pulse rate is at the same pace as the heart rate
Two blood circuits
The human circulatory system has
what is known as Double Circulation
• Blood passes through the heart twice
on its journey around the body
• It consists of two circuits:
• 1: Pulmonary Circulation
– Blood leaves the heart
– goes to the lungs to become oxygenated
– returns to the heart
• 2: Systemic Circulation
– Blood leaves the heart
– travels to other parts of the body
– returns to the heart
Structure of the heart
The heart is split down the
middle into two sides by the
septum
• Each side has an upper
chamber called an atrium
(plural atria)
• Each side also has a lower
chamber called a ventricle.
• This makes a total of 4
chambers
• Valves between the upper
and lower chambers ensure
that blood only flows in one
direction
Left versus right
Heart diagrams are
always shown as if facing
the person
• The left side of the heart
appears on the right of
the diagram, and vice
versa
• The left side of the heart always pumps oxygenated
blood (shown in red), received from the lungs, and pumps it
to the body.
• The right side always pumps deoxygenated blood (shown
in blue), received from the body, and pumps it to the lungs
Blood vessels of the heart
The vena cava (veins)
bring blood from the body
into the right atrium.
• The right ventricle pumps
blood into the pulmonary
artery, which leads to the
lungs.
• The pulmonary vein returns blood from the lungs to the
left atrium.
• The left ventricle pumps blood into the aorta (an artery)
which leads to all other parts of the body.
• Both the pulmonary artery and the aorta have valves at the
base to prevent blood flowing back into the heart.
Respiration
• We’ve learned in
digestion that food is
absorbed into our
bloodstream and
carried around to all
the cells in our body!
• The process that
releases energy from
this food is
RESPIRATION.
