CASE 1
1. What is the composition of blood? (And in which concentration)
Blood consists of different components:
Plasma, this is the extracellular Matrix.
• Main component is water → around 92%
• Proteins → around 7%
Plasma proteins have many functions, e.g. blood clotting and defense against
foreign invaders. They can also act as carriers for different molecules (steroid
hormones, cholesterol, drugs, certain ions). Also some plasma proteins act as
hormones or extracellular enzymes.
The most important proteins:
o 60% → Albumins
o Globulins
o Fibrinogen → The clotting protein
o Transferrin → Iron-transporting protein
• The resting 1% is:
o Dissolved organic molecules
o Ions
o Trace elements
o Vitamins
o Dissolved oxygen
o Carbon dioxide
Then, blood also contains cellular elements besides of the blood plasma.
There are three main cellular elements:
1. Red blood cells → Erythrocytes
o Don’t have a nuclei when they are in the bloodstream
o Main function → Transporting oxygen from lungs to tissues and carbon
dioxide from tissues to lungs.
2. White blood cells → Leukocytes
o Main function → Immune responses, defending the body against foreign
invaders (parasites, bacteria and viruses)
In blood there are 5 types of mature white blood cells: Phagocytes → They
• Monocytes → Monocytes that leave the circulation can engulf and ingest
and enter the tissues develop into macrophages. foreign particles (like
• Neutrophils bacteria)
• Eosinophils Granulocytes→
• Basophils → Tissue basophils are called mast cells. Contain cytoplasmic
inclusions that give
• Lymphocytes → Also called Immunocytes them a granular
because they do specific immune responses appearance
directed against invaders.
3. Platelets → Thrombocytes
o Main function → Coagulation, which is the process by which blood clots
prevent blood loss in damaged vessels.
,But, in which
concentration
does this
plasma and
different sorts
of blood cells
occur in the
human blood?
→ Plasma =
58%
→ White blood
cells = <1%
→ Red blood
cells = 42%
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2. How are different blood cells made?
The production of blood cells is called hematopoiesis.
The process happens in the bone marrow of a person → This is a soft tissue that fills the
hollow center of bones. In this bone marrow, a certain cell type can be found which is the
precursor cell type where all the blood cells originate from.
→This particular cell is called a pluripotent hematopoietic stem cell. The
hematopoiesis starts when this cell starts dividing and specializing.
First the pluripotent hematopoietic stem cells become uncommitted stem cells,
which on their turn specialize in two different type of cells: the Committed
progenitor cells and the Lymphocyte stem cells.
From the lymphocyte stem cells only lymphocytes are made, the rest of the blood
cells and platelets are made from the committed progenitor cells.
Two important cells two remember are the cells out of which red blood cells and
platelets are made:
o Erythroblast → Erythrocyte
o Megakaryocyte → Platelets
The two type of stem cells that form out of the pluripotent hematopoietic stem cell can also
be divided into lymphocyte stem cells and myeloid stem cells.
,As already said, all the blood cells come from one pluripotent stem cell and then specialize
before they go into the blood stream.
But → Certain blood cells also have to go to the thymus where they specialize
before they go into the blood stream. The white blood cells that are made here are
called the T-cells.
The bone marrow can be active, then it has a red color and it contains a lot of hemoglobin.
But it can also be inactive, then it has a yellow color because of a high amount of adipocytes.
The hematopoiesis is controlled by cytokines → These are peptides or proteins released
from one cell that affect the growth or activity of another cell.
The leukopoiesis is highly influenced by cytokines, e.g.: the interleukins (for
interaction between white blood cells) and the colony-stimulating factors (regulate
leukopoiesis).
Platelet production → regulated by thrombopoietin (TPO)
Red blood cell production → regulated by erythropoietin
Hematopoiesis can easily be shown as:
In babies, the blood production also finds place in the liver and spleen. After the birth, only
the bone marrow produces blood cells, and by aging the amount of places where
hematopoiesis takes place decrease to only some specific bones.
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, 3. What are the roles of the different blood cells?
Red blood cells (Erythrocytes) → Main function is to facilitate oxygen transport form the
lungs to cells, and the carbon dioxide transport from cells to lungs.
• Red blood cells don’t have a nucleus, also other organelles such as mitochondria
break down and leave the cell.
• In the blood circulation, also
reticulocytes are found, which
are the precursor of the
erythrocytes and will develop into
a mature red blood cell in 24h.
• They have a flat shape, just like
biconcave disks. The
cytoskeleton gives the red blood
cell its shape.
• The main component of red
blood cells is
hemoglobin (Hb). This a large protein complex with four
protein chains, which are all wrapped around a heme group.
In total there are four heme groups per hemoglobin complex,
which are all identical, with an iron atom (Fe) in the center.
• If the hemoglobin level in the blood is too low, there is a
decrease in the oxygen transport. This can also happen
when hemoglobin molecules are abnormal, causing cells
with another shape, e.g. sickle cell disease.
Platelets → Main function is the coagulation.
• Platelets are small fragments of cells
called megakaryocytes, which are large
polyploid cells because they undergo 7x
mitosis without division.
• Platelets aren’t cells, they are colorless
and don’t have a nucleus. They have
mitochondria, smooth ER and a lot of
granules.
• Platelets don’t live long, about 10 days,
and they are only active when damage occurs to the walls of blood vessels.
• Platelets are involved in a process called hemostasis → process of keeping blood
within a damaged blood vessel.
This process happens in three major steps:
1. Vasoconstriction → Blood flow and pressure are temporarily decreased within
the blood vessel.
2. Temporary blockage of a break by a platelet plug → First platelet adhesion
starts and the platelets are activated and thereby release cytokines.
3. Coagulation → formulation of a clot that seals the hole until tissues are
repaired. Fibrin is highly involved in this step.
