Maintaining a Balance
Topic 7: Components of Blood
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
DOT POINT
There is no DOT Point directly linked to this topic, however
this topic will provide you with the background knowledge you
need to know in order to understand the topics that follow.
Introduction
Both plants and animals require a transport system to distribute
food and oxygen to active cells and to remove carbon dioxide and
any other wastes products that may accumulate due to metabolic
processes.
allaboutwildlife.com
Introduction
Unicellular organisms and small multicellular organisms rely on
the processes of diffusion, osmosis and active transport of
substances directly between the surface of the organism and the
environment.
microscopy-uk.org.uk
Introduction
In most multicellular
organisms, transport of
substances in this way is not
adequate, due to their large
surface area to volume ratio.
The distance that substances
must move between the centre
of the body of a large organism
and its outer surface is to large
to simply rely on diffusion,
osmosis and active transport.
dongettyphoto.com
Introduction
Therefore specialised transport systems have developed in
complex plants and animals to carry substances. The common
features of a transport system are:
1. A suitable transport medium (fluid)
2. The presence of vessels in which substances can be carried
3. A driving mechanism to ensure that substances move in the
correct direction.
extraordinarylight.blogspot.com
Plants
Plants produce their own food in leaves and this food must be
carried in a dissolved form, to all parts of the plant. Chemical
substances that are needed for photosynthesis must be carried
from the roots, where they enter the plant to the leaves where
they are used. The transport tissue in plants is known as vascular
tissue and consists of xylem and phloem.
commons.wikimedia.org
Animals
In animals, transport of chemicals occurs in a fluid medium such
as blood and the same fluid circulates around the body. The role
of the transport system is to pick up nutrients such as digested
food and oxygen, and distribute them to parts of the body where
they are needed.
gumtree.com.au
Animals
Blood also picks up wastes such as carbon dioxide from the cells
and carry them to excretory organs where they can be removed
from the body. In mammals, the transport system is known as
the cardiovascular system which is made up of the following:
 A pump (the heart) to move the blood in the correct direction
 A series of vessels (arteries and veins) that act like highways
which direct the blood throughout the body.
heraldsun.com.au
Blood as a Medium
Blood is a fluid transport medium that flows through the
cardiovascular system in all vertebrates and some invertebrates.
It is a complex fluid which consists of blood plasma and blood
cells.
gizmag.com
Blood as a Medium
If whole blood is spun in a
centrifuge, it separates into its
component parts: 45% cells and
55% watery plasma. At the
bottom of the tube, the heavier
cells settle out and appear dark
red in colour due to the
presence of red blood cells. The
fluid part or plasma is lighter in
colour (pale yellow) and
contains many substances
dissolved or suspended.
sciencephoto.com
Blood as a Medium
Blood has a temperature of 38C and
has a pH of 7.35. The volume of
blood in the human body varies from
one person to the next but an adult
has approximately 5 litres of blood.
For normal functioning of the body
and its enzymes, these levels of
temperature, pH and volume must be
carefully maintained.
scranton.edu
The Composition of Blood
Blood contains three main types of cells:
1. Red blood cells
2. White blood cells
3. Platelets
All blood cells are produced
in bone marrow
lesleypaulvj.blogspot.com
The Composition of Blood
Red Blood Cells:
 There are approximately 4-6 million red blood cells per
millilitre (mL) of blood and their main function is to transport
oxygen. 1 mL is the amount of liquid that could fit into a cm
cube.
gcse.com
The Composition of Blood
Red Blood Cells:
 RBC’s form in bone marrow, at first each cells has a nucleus,
but as the cell matures, the nucleus disappears and a red
pigment called haemoglobin develops inside the cell.
embryology.med.unsw.edu.au
The Composition of Blood
Red Blood Cells:
 As a result of the absence of a
nucleus, the mature RBC’s
are small, with a diameter of
approximately 7μm
(micrometers). RBC’s are
round but they are biconcave
rather than spherical. This
picture is a scanning electron
micrograph of a red blood
cells.
legacy.owensboro.kctcs.edu
The Composition of Blood
Red Blood Cells:
 RBC’s have a life span of about 4 months. When they die, they
are broken down and replaced by newly formed blood cells
from the bone marrow.
fi.edu
The Composition of Blood
Red Blood Cells:
 Haemoglobin is an
iron-containing protein
molecule that gives red
blood cells their colour.
It consists of two parts: a
protein (globin) and a
pigmental iron compound
called the haem group.
hyperbaric-oxygen-info.com
The Composition of Blood
Red Blood Cells:
 Iron is therefore essential for the formation and maturation of
red blood cells. Haemoglobin has an affinity for oxygen and
readily combines with it to form oxyhaemoglobin.
open.jorum.ac.uk
The Composition of Blood
Red Blood Cells:
 Haemoglobin releases oxygen easily in areas of low oxygen
concentration. RBC’s are also about to transport a small
amount of carbon dioxide in the blood and they help maintain
the pH balance of the blood.
cikgurozaini.blogspot.com
The Composition of Blood
White Blood Cells:
 White blood cells, also produce in bone marrow, function as
part of the immune system. Their main role is to protect the
body against invading organisms. There are approximately
4000-11000 white blood cells per mL of human blood.
hepatitiscnewdrugs.blogspot.com
The Composition of Blood
White Blood Cells:
 When the number of white blood cells is higher, it is often
indicative of an infection. Leukaemia, a form of cancer of
white blood cells, also greatly elevates the white blood cell
count.
flannerys.com.au
The Composition of Blood
White Blood Cells:
 WBC’s are larger than RBC’s (about 50% bigger) and not as
abundant. All white blood cells have a nucleus, in some cells it
might be an unusual shape. In prepared microscope slides of
blood, the staining technique imparts a purple colour to the
nucleus.
fi.edu
The Composition of Blood
Platelets:
 Platelets are fragments of special cells, also produced in the
bone marrow. They are disc shaped, about half the size of
RBC’s and there about 400000 per mL of blood.
biomed.brown.edu
The Composition of Blood
Platelets:
 Platelets function in the clotting of
blood. They stick to each other and to
blood fibres at the site of a wound. This
contact causes them to break open and
they release an enzyme, thromboplastin
which sets in progress a sequence of
steps to seal the blood vessels and cause
they blood to clot, preventing excessive
blood loss.
usborne-quicklinks.com
The Composition of Blood
Another component of Blood
that is not a ‘cell’ is called
Plasma:
 Plasma is the yellow, watery
fluid part of blood. It consists
of about 90% water and the
other 10% consists mainly of
proteins. Plasma makes up
most of the volume of blood
and it carries many substances
in either dissolved or
suspended form.
shs-bio-6th-wood.wikispaces.com
The Composition of Blood
Plasma carries:
 proteins
 nutrients
 gases
 waste products
 ions (salts)
 hormones
 Other substances such as vitamins
bloodservices.ca
Activity/Homework
-Students are to complete 2.1.1 Composition of Blood
Worksheet