Download Blood – Part 2 - Mount Carmel Academy


WBCs are classified into
two major groups,
depending on whether or
not they contain visible
granules in their
cytoplasm.
1. Granulocytes – Granule
containing WBCs.
2. Agranulocytes – Lack
visible cytoplasmic
granules.

Granulocytes – Granule
containing WBCs.
› Have lobed nuclei
 Typically consist of several rounded nuclear
areas connected by thin strands of nuclear
material.
› The granules in their cytoplasm stain
specifically with Wright’s stain.
› Granulocytes include the:
1. Neutrophils
2. Eosinophils
3. Basophils
Multilobed nucleus.
 Very fine granules that
respond to both acid
and basic stains.
 The cytoplasm as a
whole stains pink.
 Avid phagocytes at
sites of acute infection.


Blue-red nucleus.
› Resembles an old
fashioned telephone
receiver.
Large brick-red
cytoplasmic granules.
 Their number increases
rapidly during allergies
and infections by
parasitic worms
(ex: tapeworms and
flatworms)

Rarest of the WBCs.
 Contain large histaminecontaining granules that
stain dark blue.

› Histamine – Inflammatory
chemical that makes
blood vessels leaky and
attracts other WBCs to
the inflammatory site.

Agranulocytes – lack visible
cytoplasmic granules.
› Their nuclei is closer to the norm – that is
spherical, oval, or kidney shaped.
› The agranulocytes include:
1. Lymphocytes
2. Monocytes
Have a large, dark
purple nucleus that
occupies most of
the cell volume.
 Slightly larger than RBCs.
 Tend to take up residence
in lymphatic tissues, where
they play an important role
in the immune response.

Largest of the WBCs.
 Except for their more abundant
cytoplasm and indented nucleus, they
resemble large lymphocytes.
 When they migrate into the tissues, they
change into macrophages with huge
appetites.
 Macrophages are very important in
fighting chronic infections.


Platelets – One of the
irregular cell fragments of blood.
› Not cells in the strict
sense; They are fragments of bizarre
multinucleate cells called megakaryocytes.
 Megakaryocytes rupture releasing thousands
of anucleate “pieces” that quickly seal
themselves off from the surrounding fluids.
Appear as darkly
staining, irregularly
shaped bodies
scattered among the
other blood cells.
 Needed for the
clotting process.


Hematopoiesis –
Blood cell formation.
› Occurs in red bone
marrow.
 This tissue is found chiefly in the:
1.
2.
3.
4.
Flat bones of the skull and pelvis
Ribs
Sternum
Proximal epiphyses of the humerus and femur
› After the cells mature, they are discharged
into the blood vessels surrounding the area.

All the formed elements arise from a
common type of stem cell, the
hemocytoblast.
› Hemocytoblasts resides in the bone marrow.
› Their development differs and once a cell is
committed to a specific blood pathway it
cannot change.
Because they are anucleate,
RBCs are unable to synthesize
proteins, grow, or divide.
 As they age, RBCs become
more rigid and begin to fragment, or fall
apart in 100-120 days.
 Their remains are eliminated by phagocytes
in the liver, spleen, and other body tissues.
 Lost cells are replaced by the division of
hemocytoblasts.


The developing RBCs divide many times
and then begin synthesizing huge amounts
of Hb.
› When enough Hb
has been accumulated, the nucleus
and most organelles
are ejected and the
cell collapses inward.

The entire developmental process from
hemocytoblast to
mature RBC takes 3-5 days.

The rate of erythrocyte
production is controlled
by a hormone called
erythropoietin.
› Normally a small amount
of erythropoietin circulates in the blood at all
times, and RBC are formed at a fairly constant
rate.
› The kidneys play the major role in producing this
hormone.
 If blood levels of O2 begin to decline, the kidneys
step up their release of erythropoietin.
 An excessive amount of O2 in the bloodstream,
depresses erythropoietin release.

The formation of leukocytes is stimulated
by two hormones:
1. Colony Stimulating Factors (CSFs)
2. Interleukins

The production of
platelets is accelerated by the hormone
thrombopoietin.