Circulation and Gas Exchange
Section 11
The Heart

Your teacher will show you a short video on the heart
and the circulatory system

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Heart Chambers
Right
Left
Right atrium
Left atrium
Left ventricle
Right ventricle
Cardiac Muscle
Heart Valves
Semi-Lunar
valve
Right
Left
Semi-Lunar
valve
Tricuspid valve
Bicuspid valve
Valves prevent backflow of blood i.e. blood travels in one direction only
Heart Valves

The diagram shows that
blood is flowing from the
top chambers of the heart,
the atria, into the bottom
chambers, the ventricles.

To allow this to happen,
the tricuspid and
bicuspid valves must
open, while the SL
valves are closed.
Heart Valves

When blood is being
pumped out of the heart,
blood is forced from the
ventricles and out through
the arteries

The SL valves are open
and the tricuspid and
bicuspid valves are
closed to stop blood
flowing backwards
Coronary Arteries

These supply the heart with
food and oxygen to keep
it functioning

Heart tissue needs a blood
supply for respiration to
occur

If the blood supply to the
heart was interrupted, this
may result in a heart
attack
Right
Coronary
Artery
Aorta
Left
Coronary
Artery
Flow of blood
The Circulatory System

Blood enters the right side of the heart first
carrying blood low in oxygen through blood
vessels called the vena cava

Blood is then sent to the lungs to become enriched
in oxygen. The pulmonary artery takes blood to
the lungs

Blood comes back to the heart rich in oxygen via
the pulmonary vein

Blood rich in oxygen is now pumped out to the rest
of the body via the aorta

http://www.bbc.co.uk/scotland/education/bite
size/standard/biology/the_body_in_action/the
_need_for_energy_rev6.shtml
Left and Right Ventricles

The right ventricle wall
is thinner than the left
ventricle wall because it
only pumps blood to the
lungs so does not need a
lot of muscle

The left ventricle wall is
much thicker because it
pumps blood around the
body
Quick Quiz
1.
Name the heart chamber that receives blood from the body
2.
Which side of the heart deals with deoxygenated blood?
3.
In which chamber of the heart is blood pressure greatest?
4.
Name the valve that separates the right atrium from the right ventricle
5.
What happens to the coronary arteries if you don’t look after your
heart?
Answers
1.
Right atrium
2.
Right
3.
Left ventricle
4.
Tricuspid valve
5.
They become blocked
Types of Blood Vessel
•Arteries carry blood away from the heart.
•Arteries have a pulse – this is the movement of blood
being pushed out of the heart along an artery
•Arteries are under high pressure because of the
narrow cavity
Types of Blood Vessel
• Veins are blood vessels that carry blood to the heart
• Veins have valves to prevent the backflow of blood
(veins carry blood at low pressure)
Types of Blood Vessel
• Capillaries are blood vessels that connect arteries to veins
and allow gas exchange of materials between blood and the cells
of the body
Arteries, Capillaries, Veins
V.E.A.L.
VEINS ENTER (THE HEART)
ARTERIES LEAVE (THE
HEART)
Blood Vessels Around the Body
The Main Blood Vessels of the Body –
Copy and Complete this table
Blood Supply
Organ
Going to
Away from
Hepatic Artery
Hepatic Vein
Pulmonary Artery
Pulmonary Vein
Kidney
Intestines
The Main Blood Vessels of the Body
Blood Supply
Organ
Going to
Away from
Liver
Hepatic Artery
Hepatic Vein
Kidney
Renal Artery
Renal Vein
Lungs
Pulmonary Artery
Pulmonary Vein
Intestines
Mesenteric
Artery
Hepatic Portal Vein
Quick Quiz
1.
Use the words artery, capillary or vein to answer the following questions
Which one pulsates?
2.
Which one has valves?
3.
Which one has thick muscular walls?
4.
Which one is permeable?
5.
Which one carries blood to the heart?
6.
Which one carries blood at the lowest pressure?
7.
Which one can change its shape to control the flow of blood?
Answers
1.
Artery
2.
Vein
3.
Artery
4.
Capillary
5.
Vein
6.
Vein
7.
Artery
Structure and Function of the
Lungs
The Lungs
The Lungs

Air passes from our mouths to our lungs by passing down a
series of tubes

The largest is the trachea. This large pipe is held open by
rings of cartilage which is made of a tough, flexible material

The trachea branches into two smaller tubes, each called a
bronchus (pleural: bronchi) which lead to the lungs

Each bronchi divides into smaller and smaller branches called
bronchioles. Bronchioles end in tiny air sacs called alveoli
Alveoli

The alveoli are important for gas exchange. When air rich in
oxygen enters the lungs it diffuses across the alveoli and into
the bloodstream

At the same time, carbon dioxide in the blood diffuses out of
the blood and into the air sacs
Blood capillary
Alveoli

The alveoli are well adapted for gas exchange because:
1.
They have very thin membranes so the gases do not have far
to diffuse
2.
They have a rich blood supply of blood capillaries very close
to each alveolus
3.
They have a moist lining, which allows gases to dissolve in the
body fluids
4.
Taken together they have a very large surface area
Gas Exchange Summary
Composition and Functions of Blood
Blood Composition

Blood is made up of three main
parts:
 plasma
 red blood cells
 white blood cells

Plasma is the liquid part of
blood that contains many
dissolved substances such as
sugars, salts, amino acids, proteins,
vitamins, water, carbon dioxide
and urea
Transport of Carbon Dioxide

Carbon dioxide is the waste gas produced as a result of respiration

This waste gas is carried in the blood and then carried to the lungs
where it is breathed out

Carbon dioxide can be transported to the lungs in the following ways:

Dissolved in plasma (80% of CO2 is carried in this way)
 Dissolved carbon dioxide makes the blood acidic, lowering the pH of the
blood. Any change in pH is not tolerated by the body so the excess CO2
is excreted by breathing rate increasing

Carried by red blood cells (RBCs)
 A pig,ment in red blood cells called haemoglobin carries the remaining
CO2 to the lungs
Transport of Oxygen

Oxygen is carried by a special pigment found in red blood
cells (RBCs) called haemoglobin

Haemoglobin gives red blood cells their red colour

RBCs are donut shaped – this shape increases the
surface area for gas exchange to occur
Haemoglobin Structure

Haemoglobin is made of 4
polypeptide units

Each unit contains a haem group
that can carry oxygen

Atoms of iron found inside the
haem group allow oxygen to be
attached

Iron salts from dietary sources e.g.
red meat, green vegetables etc are
important for oxygen uptake
Polypeptide unit
Haem group
Haemoglobin and Oxygen

Haemoglobin binds well (associates) with oxygen, but it
readily releases it (dissociates) as well. This makes it ideal for
carrying oxygen.

If the surrounding oxygen concentration is high, as in the
lungs, haemoglobin combines with oxygen to form
oxyhaemoglobin. This makes blood bright red in colour

Haemoglobin + Oxygen
Oxyhaemoglobin
Haemoglobin and Oxygen

When the surrounding oxygen concentration is low, as in
muscle tissue, haemoglobin readily detaches from oxygen.

Oxyhaemoglobin

Oxygen has diffused into cells

Haemoglobin is dark red in colour
Haemoglobin + Oxygen
Haemoglobin and Oxygen

Haemoglobin + Oxygen
Oxyhaemoglobin
Body Defences
White Blood Cells - Macrophages

A macrophage is a special type of large white blood
cell which can engulf and digest bacteria

Macrophages surround and digest bacteria that is
not normally part of the body

Phagocytosis is the process by which white blood
cells engulf and breakdown bacteria and other
unwanted matter
Phagocytosis (“cell-eating”)
Macrophage
Bacterial
particles
Lysosome containing
digestive enzymes
http://student.ccbcmd.
edu/~gkaiser/biotutori
als/eustruct/phagocyt.
html
White Blood Cells - Lymphocytes

Lymphocytes are white blood cells that
produce antibodies

Antibodies are special proteins that
attach to invading viruses and bacteria and
destroy them

Antibodies are similar to enzymes in
that they are specific to the virus or
bacteria that they attach to

Because they are specific, we have many
different antibodies to fight many different
viruses
Virus or
bacteria
Antibody
Quick Quiz
1. What is the name given to the fluid portion of the
blood?
2. Name three substances dissolved in the plasma
3. How is carbon dioxide carried in the blood?
4. What effect does carbon dioxide have on the pH of the
blood?
5. What kinds of cells produce antibodies?
6. What kinds of cells carry out phagocytosis?
Answers
1.
Plasma
2.
Carbon dioxide, glucose, amino acids
3.
In the plasma and in the red blood cells
4.
It lowers it
5.
Lymphocytes
6.
Macrophages