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 <
1%
Erythrocytes (RBC’s)
Cell Structure: biconcave disc 7 μm diameter X 2 μm
thick.
-anucleated cells (no nucleus or other cellular
organelles)
Production: erythropoiesis is stimulated by
erythropoietin hormone from kidneys.
-From infancy on, all rbc’s are produced in red bone
marrow. They are produced from pluripotent stem
cells (PPSC).
Contain 4 hemoglobin molecules/rbc;
Life span of a rbc ~ 100- 120 days
Erythrocytes (RBC’s)
Hemoglobin
Erythrocytes contains 4 hemoglobin molecules
Hemoglobin is a complex molecular structure of
two chains: α chain is 141 amino acids; β chain
is 146 amino acids.
Heme groups is bound to each chain and
contains ferrrous iron (Fe+2).
Iron is where O2 binds to each Hgb molecule
binds ~ 250 million molecules O2 X 4 = 1 billion
molecules O2 /rbc.
Hemoglobin molecular structure
Star shapes are Heme (Fe+2) molecules
Dark blue chain is β, light blue is α
Blood types
Most familiar blood types is ABO groups and Rh
group.
Blood type antigens are carried on red blood
cell membranes.
Bloods A,B,O and AB comprise the ABO group
O is “universal donor”; AB is “universal
recipient”.
Rh factor may be – or + and can result is
immune reactions if not properly matched.
Hematopoiesis
Leukocytes (WBC’s)
Cell Structure: 4,800 – 11,000/cm
-Spherical cells containing a nucleus and other
organelles. The nucleus of each cell type varies
considerably in leukocytes and is quite conspicuous
and 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.
Number ranking: NLMEB
WBC’s
Granulocytes
Composed of wbc’s that contain granules in
their cytoplasm:
Neutrophils – most plentiful in blood 60% of
wbc’s
Eosinophils – 1 – 4% of wbc’s
Basophils- least plentiful of all wbc’s ~ 0.5%
wbc’s
Neutorphils
Nucleus looks like
sausage links –
multilobed
- account for 50% of
wbcs- -3,000 to
7,000/cc
-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
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/ cc
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