Download Red Blood Cells (Erythrocytes)

The Blood
Human blood has 2 main parts:
1) Plasma – a fluid that composes 55% of blood volume and functions to:
●Keep cells and tissues moist
●Transport soluble nutrients, wastes, antibodies and hormones
2) Cells – 3 kinds produced in the bone marrow
●Red Blood Cells (Erythrocytes)
●White Blood Cells (Leucocytes and Lymphocytes)
●Platelets
Plasma (55%)
White Blood
Cells (1%)
Red Blood Cells
(44%)
Blood component
Structure and function
Plasma
• the fluid medium through which the solid blood components, along with
dissolved
gases, nutrients, wastes, and hormones, are transported around the body
• contains a number of dissolved proteins that have different functions
• One protein is essential in blood clotting. Another group contains antibodies
that
provide immunity against diseases such as measles. Others regulate the
balance
of fluids in the plasma.
Erythrocytes (red blood
cells)
• contain hemoglobin, a molecule that enables the cell to bind oxygen molecules
• without hemoglobin, would supply enough oxygen to support life for about
4.5 seconds. With hemoglobin, life can continue for about five minutes. (This
seems like a short time, but blood is continuously transported back to the heart
and then on to the lungs, where the oxygen supply is renewed.)
• do not have a nucleus in their mature stage, allowing the cell to carry more
hemoglobin
Leukocytes (white blood
cells—different types)
• function mainly to protect the body against invading microorganisms and toxins
• are much fewer in number than red blood cells
• are of several types, and unlike red blood cells, contain a nucleus
• Some types destroy microorganisms by engulfing them and then using
enzymes
to digest the microorganism and the leukocyte itself; others are specialized in
producing antibodies that are an important part of the body’s immune system.
• Fragments of white blood cells and invading microorganisms are called pus.
Platelets
• small fragments of larger cells produced from cells in bone marrow
• function primarily to initiate blood clotting
• are irregularly shaped (a) and move easily through smooth blood vessels when
resting
• become active and rupture (b) if they encounter a sharp edge, such as a cut, as
they move through a blood vessel
• When the platelet membrane breaks, the platelet releases a substance that
reacts with proteins in the plasma to create a mesh of fibres (c).
• This mesh prevents further blood flow. After a few days, the fibres contract and
begin to close the wound to the blood vessel.
Fibrin
Platelet
Red Blood Cell