Chapter 18
“The River of Life”
• Only fluid tissue in the body
• Average adult has approximately 5L of
blood
• Blood serves as the body’s transport
system:
– Delivers oxygen & nutrients to cells
– Carries away carbon dioxide and metabolic
waste to lungs or kidneys for elimination
– Distributes hormones from glands to target cells
– Transports disease fighting substances
– Distributes body heat
Components
• Blood has both solid and
liquid components
• Categorized as connective
tissue
– Living blood cell (“formed
elements”) are suspended
in non-living fluid matrix
called plasma
Plasma
• Liquid portion of the blood
• 90% water, 8% plasma proteins & 2% hormones,
vitamins, minerals and other dissolved
substances
• Aside from antibodies, plasma proteins are made
by liver & serve a variety of functions
– Albumin contributes to osmotic pressure, helping to
keep water in blood stream
– Clotting proteins reduce blood loss when a vessel is
injured
– Antibodies help protect body from pathogens
• Composition kept relatively stable through
various homeostatic mechanisms
Formed Elements
• Leukocytes (WBCs)
– Largest
– Least abundant
• Erythrocytes (RBCs)
– Slightly smaller
– 99% of living blood
• Thrombocytes (platelets)
– Smallest
– 2nd most abundant
Erythrocytes
• Flexible, biconcave discs that lack a nucleus and
most organelles
• Contain the iron-containing protein hemoglobin,
which allows it to carry oxygen in the bloodstream
for distribution to cells
Overview of Leukocytes
• Only “complete” cells in the blood (contain
nuclei and standard organelles)
• Form an “army” to defend the body against
bacteria, viruses, parasites & tumor cells
• Not confined to blood vessels like RBCs, can
slip in/out, a process called diapedesis
• Respond to chemicals emitted by damaged
cells, positive chemotaxis, and move via
amoeboid motion to area of need
Leukocyte Levels
• In leukocytosis, a high WBC count (above
11,000/mm3), usually indicates an infection
• In leukopenia, a low WBC count, is
commonly caused by anticancer drugs and
corticosteroids
• In leukemia, bone marrow becomes
cancerous and WBCs are turned out rapidly
– These cells are immature and incapable of
carrying out disease carrying functions
– Body becomes susceptible to pathogens
Types of Leukocytes
• Granulocytes: granule-containing WBCs
– Eosinophils: absorb acidic stains, appear pink
– Basophils: absorb basic stains, appear purple
– Neutrophils: do not absorb acidic or basic stain well,
appear slightly pink or purple
• Agranulocytes: lack visible cytoplasmic granules
– Lymphocytes: pale cytoplasm forms thin rim around
large, deep purple-blue nucleus
– Monocytes: often kidney shaped, abundant gray-blue
cytoplasm & dark purple nucleus
Granulocyte (WBCs) Functions
• Neutrophils: active phagocytes; number
increases rapidly during short-term or acute
infections
• Eosinophils: Kill parasitic worms; increase
during allergy attacks; might phagocytyze
antigen-antibody complexes and inactivate
some inflammatory chemicals
• Basophils: Granules contain histamine
(vasodilator), which is discharged at sites of
inflammation
Agranulocyte (WBCs) Function
• Lymphocytes: part of immune system; B
lymphocytes produce antibodies; T
lymphocytes are involved in graph rejection,
fighting tumors and viruses, and activation of
B lymphocytes
• Monocytes: Active phagocytes that become
macrophages in the tissue; serve as a longterm “clean-up team”; increase in numbers
during chronic infections
Thrombocytes (Platelets)
• Initiate clotting cascade by clinging to broken area
• Help control blood loss from broken blood vessels
Video Clip
Hematopoiesis (Blood Cell Formation)
• Occurs in red bone marrow (myeloid tissue)
• In adults, found mainly in flat bones of skull and pelvis,
the ribs, sternum and proximal epiphyses of humerus
and femur.
Types of Blood Cells