Download 7. Blood

Essentials of Human Anatomy
BLOOD
Chapter 9
Dr Fadel Naim
Ass. Prof. Faculty of Medicine
IUG
1
Blood
• Considered a connective tissue: contains
– Cells
– a liquid ground substance (called plasma)
– dissolved protein fibers.
• About four times more viscous (or thicker) than
water.
• Temperature of blood is about 1°C higher than
measured body temperature.
Blood Volume
• varies with
• body size
• changes in fluid concentration
• changes in electrolyte concentration
• amount of adipose tissue
• about 8% of body weight
• about 5 liters
Blood
• Whole blood can be separated:
– Liquid component
– cellular components
Components of Blood
• Erythrocytes (or red blood cells)
– form the lower layer of the centrifuged blood
– typically make up about 44% of a blood
sample
• Buffy coat
– makes up the middle layer
– thin, slightly gray-white layer composed of
cells called leukocytes (or white blood cells)
and cell fragments called platelets
– forms less than 1% of a blood sample
• Plasma
– straw-colored liquid that rises to the top
– generally makes up about 55% of blood
Components of Blood
• Erythrocytes and the components of the buffy coat are
called the formed elements.
• Formed elements and the liquid plasma compose whole
blood.
Functions of Blood –
Transportation
• Transports numerous elements and compounds
throughout the body.
– erythrocytes carry oxygen from the lungs to body cells
and then transport carbon dioxide from the cells back
to the lungs for expulsion from the body
– blood plasma transports
• nutrients that have been absorbed from the GI tract
• hormones secreted by the endocrine organs to their target
cells
– plasma
• carries waste products from the cells to organs such as the
kidneys, where these waste products are removed
Functions of Blood –
Regulation of Body Temperature
• Regulates body temperature.
– plasma absorbs and distributes heat throughout the
body
– for cooling the blood vessels in the dermis dilate and
dissipate the excess heat through the integument
– when the body needs to conserve heat, the dermal
blood vessels constrict, and the warm blood is
shunted to deeper blood vessels in the body
Functions of Blood –
Regulation of pH Levels
• pH is a measure of how alkaline or acidic a fluid is.
– Neutral pH is measured at exactly 7.
– Acidic fluids (e.g., orange juice) are between 0 and 7.
– Alkaline fluids (e.g., milk) are between 7 and 14.
• Blood plasma contains compounds and ions that may be
distributed to the fluid among tissues (interstitial fluid) to
help maintain normal tissue pH.
• Blood plasma pH is continuously regulated at a value of
7.4 the pH level required for normal cellular functioning.
Functions of Blood –
Maintenance of Fluid Levels
• Maintains normal fluid levels in the cardiovascular
system.
• Prevents fluid loss.
• Constant exchange of fluid between the blood plasma
and the interstitial fluid.
– If too much fluid is absorbed in the blood, high blood pressure
results.
– If too much fluid escapes the bloodstream and enters the
tissues, blood pressure drops to unhealthy low levels, and the
tissues swell with excess fluid.
• To maintain balance of fluid exchange between the
blood and the interstitial fluid, blood contains compounds
(such as salts and some proteins) to prevent excess fluid
loss in the plasma.
Functions of Blood –
Protection
• Leukocytes (white blood cells) help guard against
infection by mounting an immune response if a pathogen
or an antigen is found.
• Plasma transports antibodies, which are molecules that
can immobilize antigens until a leukocyte can completely
kill or remove the antigen.
• Platelets and blood proteins protect the body against
blood loss by forming blood clots on damaged vessels.
Components of Plasma
• Complex mixture of water, proteins, and other solutes.
• When the proteins are moved from plasma, the
remaining fluid is termed serum.
• Water makes up about 92% of plasma’s total volume.
– water facilitates the transport of materials in the plasma
Transports organic and
inorganic molecules,
formed elements, and heat
• Water
• Plasma proteins
• Other solutes
92%
7%
1%
Plasma Proteins
• The next most abundant materials in plasma are
the plasma proteins.
• Make up about 7% of the plasma.
– 6 and 8 grams of protein in a volume of 100 milliliters
of blood (referred to as g/dl)
• The plasma proteins include:
–
–
–
–
albumins
globulins
fibrinogen
regulatory proteins
Difference between Plasma and Interstitial Fluid
Plasma has more:
• Dissolved O2
O2 diffuses out into tissue
• Dissolved proteins (too big to cross caps.)
– Albumins
– Globulins
•  globulins
•  and  globulins
– Fibrinogen
Similar concentration: Salts & small molecules
Plasma Electrolytes
• absorbed from the intestine or released as by-products
of cellular metabolism
• sodium
• potassium
• calcium
• magnesium
• chloride
• bicarbonate
• phosphate
• sulfate
• sodium and chloride are most abundant
Formed Elements in the Blood
• Erythrocytes
– make up more than 99% of formed elements
– primary function is to transport respiratory gases in the blood
• Leukocytes
– make up less than .01% of formed elements
– contribute to defending the body against pathogens
• Platelets
– make up less than 1% of formed elements and
– help with blood clotting
Hematocrit
• Percentage of erythrocytes in the
blood.
• Values vary slightly and are dependent
on age and sex.
• Adult males range between 42% and
56% .
• Females range from 38% to 46%.
• Childrens’ hematocrit ranges also vary
and differ from adult values.
• Altitude can affect the hematocrit.
– body compensates by making more
erythrocytes
– more erythrocytes in the blood can
carry more oxygen to the tissues
Erythrocytes
• Mature erythrocytes lack nuclei.
• Transport oxygen and carbon dioxide to and from the
tissues and the lungs.
• Lack of nuclei enables them to carry respiratory
gases more efficiently.
Hemoglobin in Erythrocytes
• Every erythrocyte is filled with approximately 280 million
molecules of a red-pigmented protein called hemoglobin.
• Transports oxygen and carbon dioxide, and is
responsible for the characteristic bright red color of
arterial blood.
• Hemoglobin that contains no oxygen has a deep red
color that is perceived as blue because the blood within
these veins is observed through the layers of the skin
and the subcutaneous tissue.
Erythrocyte Life Cycle
• No organelles, therefore can not sustain itself.
• Finite life span of about 120 days.
• Daily:
– About 1% of oldest RBCs are removed
• Are phagocytized by liver and spleen.
– By macrophages
• Some components saved, some discarded
Blood Types
• Determined by membrane proteins in the RBC
cell membrane.
• Called surface antigens (agglutinogens).
• Most common group: ABO blood group
– Two antigens: A and B
• ABO blood types:
– Type A: have the A surface antigen
– Type B: have the B surface antigen
– Type AB: have both the A and the B surface antigens
– Type O: have neither the A or the B surface antigen.
Blood Types
• Antibodies (agglutinins) to the surface antigens are in
the plasma
• ABO group has anti-A antibodies and anti-B
antibodies
–
–
–
–
Type A: have anti-B
Type B: have anti-A
Type AB: has neither anti-A or anti-B
Type O: has both anti-A and anti- B
White Blood Cells
• leukocytes
• protect against disease
• interleukins and colony-stimulating factors stimulate
development
• granulocytes
• neutrophils
• eosinophils
• basophils
• agranulocytes
• lymphocytes
• monocytes
Platelets
• Irregular, membrane-enclosed cellular
fragments
– about 2 micrometers in diameter (less than onefourth the size of an erythrocyte).
• Sometimes called thrombocytes.
• Continually produced in the red bone marrow
by cells called megakaryocytes.
THE END