InSight
The components of blood
Figure 10.1
THE PLANNER
Plasma
(liquid)
55% of
blood volume
Formed
elements
45% of
blood volume
Buffy coat
Blood has both liquid and cellular parts. Blood cells come in various types
and densities. Here, the density of blood cells is expressed as the number
of cells per microliter (^L). One drop of blood equals about 50 nL.
Plasma components (by weight) and their functions
Water
(91.5%)
Proteins
(7% )
Other solutes
(1.5%)
Water acts as a solvent for carrying other substances and absorbs
heat
Albumin, globulins, and fibrinogen maintain osmotic balance and
pH buffering, help with blood clotting, and help transport antibodies
and lipids
Other solutes include:
• Electrolytes (Na+, K+, and Cl-), which help with osmotic balance, pH
buffering, and regulation of membrane permeability
• Nutrients (glucose and fatty acids)
• Respiratory gases (O2, CO2, N2)
• Regulatory substances, such as hormones
• Waste products (urea, uric acid)
Formed elements and their functions
(number per microliter of blood)
The buffy coat is composed of white blood cells and platelets
White blood cells
White blood cells fight invading microbes and eliminate cell
(5,000-10,000/gL)
debris; they make up less than 0.2% of formed elements
Lymphocytes (20-25% of total white blood cell
(WBC) count; 6-16pm in diameter) have a round
nucleus and attack viruses and bacteria
Eosiniphils have a nucleus with 2 lobes and are
involved in allergic reactions, phagocytosis of
antigen-antibody complexes, and defense
against worms
Neutrophils have a nucleus with 2-5 lobes and
destroy bacteria by phagocytosis and chemicals
Basophils have a nucleus with 2 lobes and secrete
heparin, histamine, and serotonin that intensify
allergic reactions
Monocytes have a horseshoe-shaped nucleus and
destroy microbes and cell debris by phagocytosis
Platelets
(150,000-400,000/|tL)
Red blood cells
(4-6 million/pL)
Platelets are cell fragments that are important in
blood clotting, although they make up less than
1 % of formed elements
These disc-shaped cells contain a protein called
hemoglobin and transport most of the O2 and CO2
in the blood; they make up most of the formed
elements
Blood Functionally Connects the Body Organ Systems
289
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