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Blood
and
Body Fluids
Cardiac muscle: note the branching nature of
the cardiac muscle fibres
The Blood Vessels
The Reds and The Whites
White
blood cell
(granular)
Red Blood Cells
In an average healthy
person, approximately 45 per
cent of the blood volume is
cells, among them red cells
(the majority), white cells,
and platelets.
A clear, yellowish fluid
called plasma makes up
the rest of blood.
Plasma, 95 per cent of
which is water, also
contains nutrients such
as glucose, fats,
proteins, and the amino
acids needed for protein
synthesis, vitamins, and
minerals.
The level of salt in plasma
is about equal to that of
sea water.
Plasma and Tissue Fluid Recirculation
As we have just seen, the pale yellow liquid known
as plasma contains:
•Water (95%!)
•Nutrients (Can you name the main one?)
•Waste (And what’s this called?)
•Plasma proteins
•Cells (The Reds and The Whites)
What are ALBUMINS? Where do they go?
So what is tissue fluid?
Blood enters capillaries at HIGH PRESSURE
Plasma is forced out of the capillaries through gaps
between the capillary endothelial cells
Plasma proteins and red blood cells DO NOT pass through.
Look at this table and try
to work out why they
Substance
Relative Molecular
Mass
don’t pass out of
water
18
the capillaries:
glucose
180
Haemoglobin
68000
Albumin
69000
If fluid passes out of the capillaries into the tissues, how
does it re-enter the circulatory system?
Plasma protein concentration at the
venous end of capillaries is HIGH.
Osmotic pressure draws fluid back into
the capillary
This system accounts for 90% of the
tissue fluid returned into the
circulation.
What happens to the other 10%?
Another system of vessels exists in the body! The
smallest branches of these vessels lie in the body
tissues and ‘collect’ fluid:
Lymph vessels or lymphatics
The fluid is called LYMPH and contains proteins which
have originated from the tissues themselves
The lymphatics ‘empty’ into branches of the
vena cava (called the subclavian veins)……….so
the remaining 10% of fluid finds its way back
into the circulation!
Why does tissue fluid (and therefore lymph)
vary from one part of the body to another?
Compare the tissue fluid around liver cells
and around intestinal villi…….What do
you think that you will find?
Flow of lymph depends on contraction of muscle
around the vessels. Lymph vessels also have
valves. Why?
Why is lymph flow MASSIVELY SLOWER
than blood flow in the body?
Policing of Tissues
The circulation of blood, tissue
fluid and lymph allows the
whole body to be continually
checked for invaders
In addition to patrolling surveillance,
there are specific ‘checkpoints’, the
LYMPH NODES
White Blood Cells: The Facts
•WBCs are larger than Red Blood Cells
•There are fewer WBCs than RBCs, about one
white for every 600 red
•Their main job is to protect the body against
infection
•Like RBCs, they are made in the bone
marrow
•Unlike RBCs, they contain a central nucleus
and many can change shape
•There are several kinds of WBCs
White blood cells are known as
LEUCOCYTES
(lew-ko-sites)
Broadly speaking, they can be divided into two categories:
PHAGOCYTES
LYMPHOCYTES
•Destroy invading
microorganisms by
phagocytosis
•Smaller than
phagocytes
•Recognised by
granular cytoplasm
and lobed nuclei
•Only small amount of
cytoplasm
•Large round nucleus
•Destroy invaders by
producing antibodies
or by killing invaders
directly.
The Phagocytes…….
1.Neutrophils: Form about 60% of all WBCs.
Patrol the circulation and the tissues by
squeezing out of capillaries. Released in
large numbers during an infection. Short
lived.
2. Eosinophils: Respond to parasitic
infections and allergic conditions
3. Monocytes: The precursors for
macrophages. Once circulating monocytes
enter tissues, they are converted into
macrophages. Macrophages break up
invaders to expose antigens to
lymphocytes.
White
Blood
Cell
If the body is wounded, white blood cells pass
through the walls of blood vessels where they
attack and engulf invading bacteria
The Lymphocytes……..
•Each type is specialised to respond to one antigen.
•Circulate throughout blood and lymph, so come into contact with
any pathogens and each other.
•B and T cells interact with each other for effective defence.
B Cells: Divide and secrete antibodies into the blood
T Cells: Subdivided into T Helper Cells and T Killer Cells:
T Helper Cells:
Release chemicals
which stimulate B Cells
T Killer Cells:
Attach to diseased cells in the
body and release toxin to kill
cell and pathogen
White Blood Cells
Platelets
Inactivated platelet
Red blood cell
Platelets are derived from special blood cells in the bone
marrow
They help repair torn blood vessels and clot blood
following an injury
When there is no injury, they circulate in the blood in an
‘inactivated’ state
Activated platelets have ‘processes’ which
help plug the wound
Red Blood Cells: Revision
Biconcave disc
7 micrometres
diameter
No nucleus
No mitochondria
Oxygen carried by
haemoglobin
Can you identify these cells?
Platelet Monocyte T-Lymphocyte
Red Blood Cell
Now try and identify these
White Blood Cells:
(The images have been photographed
using a light microscope)
Neutrophil
Neutrophil
Neutrophil
Lymphocyte
Eosinophil
Neutrophil
Eosinophil
Monocyte
Neutrophil
Lymphocytes
Neutrophils
Lymphocyte
Basophil