Chapter 19
The Circulatory System I
Blood
Cardiovascular System
The cardiovascular system includes:
Blood
The Heart
Blood Vessels
–Large and small arteries and arterioles
–Large and small veins and venules
–Capillaries
Blood
A liquid connective tissue made up of plasma
and formed elements.
BLOOD COMPOSITION:
Serum: the liquid portion of blood after it has
clotted ( fibrinogen has clotted).
Plasma: liquid portion of blood
Water – 92% by weight
Proteins – 6-9 gm/dl; most abundant plasma solute
Formed elements (rbc, wbc and platelets)
Blood fractions
Blood
Blood Proteins
Albumin is the major contributor to plasma
viscosity and osmolarity. Albumin- smallest
and most abundant protein; serves to
transport plasma solutes and buffer the pH of
blood plasma.
Fibrinogen- soluble precursor of fibrin, a sticky
protein that forms framework for clotting.
Globulins- 3 classes: alpha (α), beta (β) and
gamma (γ) (smallest to largest) in molecular
weight.
Formed Elements
Red blood cells (rbc) = erythrocytes ~45-50%
pcv*
White blood cells (wbc) = leukocytes ~ < 1%
pcv*
– Granulocytes- neutrophils, eosinophils and
basophils
– Agranulocytes- lymphocytes and monocytes
– Thrombocytes = platelets (part of buffy coat)
* = packed cell volume
Erythrocytes (RBC’s)
4.2 – 6.2 million per mm3
Cell Structure: biconcave disc 7.5 μm diameter,
X 2 μm thick.
anucleated cells (no nucleus or other cellular
organelles)
Production: erythropoiesis is stimulated by
erythropoietin, a hormone from kidneys.
-From infancy on, all rbc’s are produced in red bone
marrow. They are produced from pluripotent stem
cells (PPSC).
Contain 280 million hemoglobin molecules/rbc;
Life span of a rbc ~ 100- 120 days
Erythrocytes (RBC’s)
Hemoglobin
Hemoglobin (Hgb) is a complex molecular structure of four polypeptide chains: 2 α chains and 2
β chains.
Each α chain contains 141 amino acids; β chain
contains 146 amino acids.
One heme group is bound to each chain and
contains ferrous iron (Fe+2).
Oxygen binds to Fe+2. Each Hgb molecule binds
four oxygen atoms. Therefore each RBC can
transport about 4 x 280 million oxygen atoms
Hemoglobin molecular structure
Star shapes are heme groups containing Fe+2
Dark blue chain is β, light blue is α
Blood types
Most familiar blood types are ABO groups and
Rh group.
Blood type antigens are carried on red blood
cell membranes.
Blood types A,B,O and AB involve the ABO
group
O is “universal donor”; AB is “universal
recipient”.
Rh factor may be present (+) or absent (-) and
immune reactions can result if not properly
matched.
Hematopoiesis
Leukocytes (WBC’s)
Cell Structure: 4,800 – 11,000/mm3
-Spherical cells containing a nucleus and other
organelles. The nucleus of each cell type varies
considerably in leukocytes and is quite conspicuous,
thus helps in identifying each cell type.
Production:
-stimulated by two cytokines: (interleukin and colony
stimulating factor [CSF]).
-All wbc’s are produced from PPSC by a process
called leucopoiesis. WBC’s are produced in red
bone marrow and may remain there until needed in
the body or they may migrate to other organs for
further differentiation.
Percentage ranking: NLMEB
Differential Leukocyte Count
Smear a drop of blood over a slide
Stain the blood smear with Wright’s stain
- gentian violet stains nuclei violet
- eosin stains proteins pink
Count 100 leukocytes, tallying each type
neutrophils: 60 – 70% of total count
lymphocytes: 20 – 25 %
monocytes: 3 – 8 %
eosinophils: 2 – 4 %
basophils: 0.5 – 1 %
WBC’s
Granulocytes
Leukocytes that contain granules in their
cytoplasm:
Neutrophils – most plentiful in blood (60 – 70 %)
Eosinophils – 1 – 4% of wbc’s
Basophils- least plentiful of all wbc’s ~ 0.5%
wbc’s
Neutrophils
Nucleus looks like sausage links – multilobed
- about 60% of wbcs: 3,000 to 7,000/mm3
-Life span: 6 hrs – few days
- phagocytize bacteria
Eosinophils
Bilobed nucleus
Account for 1-4% of wbc
Red staining granules
Life span- 8 – 12 days
Kill parasitic worms, active in allergies
Basophils
Bilobed nucleus “U” or “S”
Account for < 0.5% wbc
Dark bluish-purple staining
granules
Life span- hrs. - days
Contain histamine, and
inflamatory substances
Agranulocytes
Conspicuous granules are lacking in the
cytoplasm.
Composed of: Lymphocytes and Monocytes.
Lymphocytes are most important in immune
system in lymph nodes, Peyers patches, and
spleen.
Lymphocytes
Round nucleus fills most of
cytoplasm
Account for 25-33 % of wbc’s
Similar size to neutrophils
Life span- hrs. to years
Two types: “B” and “T”
B cells mature in red bone
marrow
T cells start in red marrow and
mature in Thymus gland
Monocytes
Largest wbc’s in circulation
Large “U: shaped or kidney
shaped nucleus
Account for 4-8% of wbcs
Life span- months
Active in clotting to plug
holes until clot can form.
Become macrophages after release from red
bone marrow into circulation
Macrophages are major phagocytes in body
Thrombocytes (platelets)
Cellular fragments very small under
microscope.
~ 250,000 platelets/ mm3
Contain serotonin, Ca++,
enzymes and platelet growth
factor.
Stick together to form plugs
and stop bleeding (hemostasis).
Picture is of a megakaryocyte from which
platelets are produced.
Blood clot of fibrin and platelets and
other blood cells