Transcript Circulation and Gas Exchange

Circulation and Gas Exchange
The Heart
• The heart is a muscular organ that is
divided into 4 chambers:- 2 atria and 2
ventricles. (left and right)
• The left ventricle wall is very thick and
muscular since it has to pump blood all
round the body.
• The right ventricle wall is less thick since it
just pumps blood to the lungs.
• The heart has 4 heart valves.
• 2 of the valves are between the atria and
ventricles. On the left hand side is the
bicuspid valve. On the right hand side
is the tricuspid valve.
• The 2 other heart valves are at the origins
of the pulmonary artery and the aorta –
these are the semi-lunar valves.
• The valves ensure that blood is only able
to flow in one direction. They prevent
backflow of blood.
Semi lunar valves
aorta
Pulmonary
artery
Vena
cava
Right
atrium
Pulmonary
vein
Left
atrium
Bicuspid
valve
Tricuspid
valve
Right ventricle
Left ventricle
• Since the heart wall is made of muscle it
must get its own supply of oxygenated
blood.
• The heart is supplied by the coronary
arteries. (a branch of the aorta).
• If a coronary artery becomes blocked, the
heart does not get a supply of oxygen
and this may result in death of the tissue.
Path of Blood Flow Through the Heart
• Blood arrives at the heart via the vena cava.
• This blood is low in oxygen (deoxygenated.)
• From the vena cava it enters the right atrium
then the right ventricle.
• It exits the heart by the pulmonary artery where
it is carried to the lungs to pick up oxygen.
• The blood becomes oxygenated.
• From the lungs it goes back to the heart via the
pulmonary vein.
• It enters the left atrium, then the left ventricle.
• The blood leaves the heart in the aorta where it
is delivered to the rest of the body.
Head &
Body
Lungs
Pulmonary
vein
Vena cava
Pulmonary
artery
Left atrium
Head &
Body
Right atrium
Right
ventricle
Left
ventricle
Aorta
Semi lunar valves
aorta
Pulmonary
artery
Vena
cava
Right
atrium
Pulmonary
vein
Left
atrium
Right ventricle
Left ventricle
Circulation & Blood Vessels
ARTERIES
• Arteries carry blood away from the heart.
• Arteries carry oxygenated blood to organs and tissues –
(except the pulmonary artery)
• Where an artery lies just under the skin the beating of
the heart can be felt. Each push of blood is called a
pulse.
• Artery walls are very thick and muscular since they have
to withstand blood travelling at high pressure.
VEINS
• Veins carry blood to the heart
• Veins carry deoxygenated blood from
organs and tissues (except the pulmonary
vein)
• Veins have valves present to stop the
blood flowing backwards.
CAPILLARIES
• Arteries split into a network of tiny thin walled
vessels called capillaries.
• Capillaries are 1 cell thick, they are long, narrow
and thin to provide a large surface area.
• Capillaries carry food and oxygen to every cell.
• Gaseous exchange happens at each cell
(oxygen in, carbon dioxide out) and waste is
removed back into the blood.
• Capillaries will reunite to form
larger vessels and then into veins.
Blood leaves the heart in arteries, flows through
capillaries and returns to the heart in veins
Circulation
• Complete the blood vessels cut out sheet.
• You need to know the difference between arteries, veins
and capillaries and the structural adaptations related to
their function.
• You need to know the next diagram too – and the names
and positions of these vessels;
• Pulmonary artery; pulmonary vein; aorta, vena cava;
hepatic vein; mesenteric artery; hepatic portal vein; renal
artery and renal vein.
• (You will need to add in the mesenteric artery to your
diagram. You can colour the oxygenated blood red and
deoxygenated blood blue)
gut
Deoxygenated
blood
Mesenteric
artery
Oxygenated
blood
The Lungs
•
•
•
•
•
The lungs are spongy/hard organs enclosed in
the _______________.
The _______________ (windpipe) branches
into two ___________ each of which enter one
lung.
The _______________ split into smaller and
smaller tubes called _______________.
The function of the cartilage is to
_______________.
The bronchioles end in very thin air sacs called
__________.
Nasal cavity
mouth
rib
larynx
Trachea
(lined with
rings of
cartilage)
Intercostal
muscles
Bronchus
Bronchioles
Alveoli (air sacs)
diaphragm
heart
Gas Exchange in the Alveoli
• The alveoli (air sacs) are lined with
moisture.
• Oxygen dissolves in this moisture and
diffuses into the blood.
• Carbon dioxide diffuses from the blood
back into the alveoli.
• Using a red pencil, colour in on the
diagrams which blood vessels contain
oxygen.
• Using a blue pencil, colour in on the
diagram which blood vessels contain
carbon dioxide.
• For example…. See next slide
Features of alveoli which allow efficient gas
exchange.
•
•
•
•
Large surface area
Thin walls
Moist surfaces
Good blood supply
• These features of the alveoli ensure
efficient gas exchange between the
alveoli and the blood stream
BEGINNINGS
ENDINGS
E Oxygen diffuses into the
sacs because there is a higher CO2
concentration in the blood.
B The air sacs are thin
air sacs, they make a very large surface area.
D The air sacs have many
which is moist so that gases can dissolve.
C Because there are so many
to let gases through easily
A The air sac is lined with mucus
blood capillaries in close contact with them
F Carbon dioxide diffuses into
the air
blood because there is a higher O2
concentration in the air sacs.
The letters give the running order ….check your answers
BEGINNINGS
ENDINGS
E Oxygen diffuses into the
1 sacs because there is a higher CO2
concentration in the blood.
6
B The air sacs are thin
2
air sacs, they make a very large
surface area.
4
D The air sacs have many
3
which is moist so that gases can dissolve.
5
C Because there are so many
4
to let gases through easily
2
A The air sac is lined with mucus
5 blood capillaries in close contact with
them
3
F Carbon dioxide diffuses into
the air
6
blood because there is a higher O2
concentration in the air sacs.
1
Features of a capillary network which
allow efficient gas exchange in tissues
• They have a large surface area.
• They are in close contact with the body cells.
• They have thin walls.
• These properties of the capillary network allow
efficient gas exchange to occur between the
blood stream and the body cells.
THE BLOOD
Composition of the Blood
Blood contains:• Red blood cells
• White blood cells
• Plasma
• Platelets
• Oxygen is carried in the red blood cells.
• Carbon dioxide is carried in the plasma.
• The concentration of carbon dioxide carried in
the plasma is limited since it combines with
water to form an acid.
• Too much acid in the blood would lead to
problems since blood functions best between pH
7.36 and 7.44.
• Most carbon dioxide is transported in blood
plasma as bicarbonate ions. (Some CO2 is
carried in the red blood cells attached to other
molecules)
• Soluble food such as glucose and amino
acids are also transported dissolved in the
plasma.
Function of Haemoglobin
  Haemoglobin is found in red blood cells.
 In high oxygen concentrations haemoglobin
combines readily with oxygen to form oxyhaemoglobin
  This happens in the lungs
  In low oxygen concentrations, oxyhaemoglobin
releases its oxygen to the body cells.
  Blood with oxygen is bright red.
  Haemoglobin carries oxygen to the tissues of the
body.
Colour in the
blood high in
oxygen red and
the blood low
in oxygen blue.
• So:Association (in lungs)
Haemoglobin + oxygen
oxyhaemoglobin
Dissociation (in
tissues)
Associate = to combine with oxygen
Dissociate = to release oxygen
White Blood Cells
• Are less numerous than RBC’s
• They contain nuclei, can change shape and
squeeze through tiny pores in capillary walls.
• They are suited to their function of defending
the body since they can reach the site of
infection outwith the circulation.
• Two types of white blood cell are monocytes
and lymphocytes.
monocytes
lymphocytes
Phagocytosis
• Is the process by which bacteria are engulfed
and destroyed by phagocytic cells such as
monocytes and macrophages (Macrophages
are cells that come from monocytes)
• The macrophage will engulf a bacterial cell and
then digest it.
• During infection, 100’s of monocytes and
macrophages migrate to the infected area and
engulf many bacteria by phagocytosis. Dead
bacteria and these cells often accumulate at a
site of injury forming pus!
Bacterium
giving out
chemical
macrophage
Lysosome (structure
containing digestive
enzymes)
Vacuole
forming
Trapped
bacterium
Bacteria being
digested by enzymes
from lysosomes
Lysosomes move
towards and fuse
with vacuole
Immunity and Antibodies
• Immunity is an organism’s ability to resist
infectious disease.
• Phagocytosis is an example of nonspecific immune response since it
provides general protection against a
wide range of micro-organisms.
• Antibody production is an example of
specific immune response as they are
specific to a particular antigen.
ANTIGEN
A molecule that is recognised as alien to the
body by the body’s lymphocytes.
ANTIBODY
The presence of an antigen in the body stimulates the
lymphocytes to produce antibodies.
An antibody is a Y-shaped molecule. Each arm has a
receptor site whose shape is specific to a particular antigen.
When an antibody meets its complementary antigen, they combine at
their specific sites like a lock and key and the antigen is rendered
harmless. It will then be engulfed by phagocytosis.
Antibody
Receptor
sites
virus
lymphocyte
antigen
Virus gains access
to body & multiplies
inside the cell
Some viral particles
become attached to
their antigens to
lymphocytes
Lymphocytes respond to this antigen by
multiplying and producing cells that mass
produce a specific type of antibody
Antigens meet
antibodies
Antigens combine with
antibodies at receptor sites
and become a harmless
complex later engulfed by
a phagocyte.
Primary and Secondary Responses
• When a person is infected by a diseasecausing organism, the body responds by
producing antibodies.
• This is the primary response.
• Because it takes a while before the
antibodies appear, the primary response is
often unable to prevent the person from
suffering the disease.
• If the person survives and are exposed to the
same disease-causing antigen in the future, a
secondary response happens.
• This happens because the body has memory
cells which remember the antigen.
• This time the disease is usually prevented.
• During the secondary response
– Antibody production is more rapid
– The concentration of antibodies produced reaches a
higher level
– The higher concentration of antibodies is maintained
for a longer time
Increasing
concentration of
antibodies
Secondary
Response
Primary
Response
0
10
20
30
40
0
10
Time (days)
First exposure
to antigen
Second exposure
to antigen
20
30
Some later time
in a person’s life
(days)