Transcript Blood 1

Blood Functions
• Blood maintains:
– Appropriate body temperature by absorbing
and distributing heat to other parts of the body
– Normal pH in body tissues
– Adequate fluid volume in the circulatory
system
Blood Functions: Protection
• Blood prevents blood loss by:
– Activating plasma proteins and platelets
– Initiating clot formation when a vessel is broken
• Blood prevents infection by:
– Synthesizing and utilizing antibodies
– Activating complement proteins & WBCs to defend the
body against foreign invaders
Physical Characteristics of Blood
• Average volume:
– 5–6 L for males; 4–5 L for females
• The pH is 7.35–7.45
• Accounts for approximately 8% of body weight
Composition of Blood
• Blood is the body’s only fluid tissue
(connective tissue)
• 2 major components
– Liquid = plasma (55%)
– Formed elements (45%)
• Erythrocytes, or red blood cells (RBCs)
• Leukocytes, or white blood cells (WBCs)
• Platelets – cell fragments
Components of Whole Blood
Plasma
(55% of whole blood)
Buffy coat:
leukocyctes and
platelets
(<1% of whole blood)
1 Withdraw blood
and place in tube
2 Centrifuge
Erythrocytes
(45% of whole blood)
Formed
elements
Blood Plasma
• Blood plasma components:
– Water = 90-92%
– Proteins = 6-8%
• Albumins-maintain osmotic pressure of the blood
• Globulins-used for transport purposes
• Fibrinogen-a clotting protein
– Organic nutrients – glucose, carbohydrates, amino
acids
– Electrolytes – sodium, potassium, calcium, chloride,
bicarbonate
– Non-protein nitrogenous substances – lactic acid, urea,
creatine
– Respiratory gases – oxygen and carbon dioxide
Formed Elements
– Only WBCs are complete cells
– RBCs have no nuclei or organelles, and
platelets are just cell fragments
• Most F.E. survive in the bloodstream for
only a few days
• Most do not divide but are renewed by
cells in bone marrow
Erythrocytes (RedBloodCells)
• Biconcave disc
– Folding increases surface area (30% more surface area)
• Anucleate, no centrioles, no organelles
– No cell division
– No mitochondria means they generate ATP anaerobically
• This prevents consumption of O2 being transported
• Filled with hemoglobin (Hb) - 97% of cell contents
– Hb functions in gas transport
• Most numerous of the formed elements
Erythrocyte Function
• Erythrocytes are dedicated to respiratory gas
transport
• Hb reversibly binds with oxygen and most oxygen
in the blood is bound to Hb
• Composition of Hb
– A protein called globin
– A heme molecule (a metal complex with iron as the
central metal atom, that can bind or release molecular
oxygen.)
Production of Erythrocytes
• Hematopoiesis – blood cell formation
– Occurs in the red bone marrow
• Axial skeleton and girdles
• Epiphyses of the humerus and femur
Erythrocyte Disorders
• Anemia – blood has abnormally low oxygen-carrying
capacity
• There are many forms of anemia, each with its own
cause.
• Anemia can be temporary or long term, and it can
range from mild to severe.
– Blood oxygen levels cannot support normal
metabolism
– Signs/symptoms include fatigue, paleness,
shortness of breath, and chills
Leukocytes (White Blood Cells)
– Protect the body from infectious
microorganisms
– Can leave capillaries
– Move through tissue spaces
– Many are phagocytic- that engulf and absorb waste
material, harmful microorganisms, or other foreign
bodies in the bloodstream and tissues.
• Two major types of leukocytes
– Granulocytes: Neutrophils, Eosinophils, Basophils
– Agranulocytes: Monocytes, Lymphyocytes
• Leukemia - a cancer of WBC
Granulocytes
– Contain cytoplasmic granules that stain
specifically with Wright’s stain
– Are larger and usually shorter-lived than
RBCs
– Have lobed nuclei
– Are all phagocytic cells
Granulocytes: Neutrophils
• Account for 65-75% of total WBC’s
• Neutrophils have two types of granules
that:
Contain peroxidases, hydrolytic enzymes, and
defensins (antibiotic-like proteins)
• Neutrophils are our body’s bacteria slayers
Granulocytes: Eosinophils
• Eosinophils account for 1–4% of WBCs
– Function:
• Lead the body’s counterattack against parasitic
infections
• Lessen the severity of allergies by phagocytizing
immune complexes (ending allergic reactions)
Granulocytes: Basophils
• Account for 0.5-1% of all WBCs
– Have large, purplish-black granules that
contain histamine
• Histamine – inflammatory chemical that acts as a
vasodilator and attracts other WBCs
(antihistamines counter this effect)
Agranulocytes: Lymphocytes
• Account for 20-25% or more of WBCs
and:
– Found mostly in lymphoid tissue (some
circulate in the blood)
• Most important cells of the immune
system
• Involved in graph rejection, fighting
tumors and viruses
• There are two types of lymphocytes: T
cells and B cells
– T cells - attack foreign cells directly
– B cells give rise to plasma cells, which
produce antibodies
Monocytes
• Account for 3–7% of leukocytes
– They are the largest leukocytes
– They have purple-staining, U- or kidney-shaped
nuclei
– They leave the circulation, enter tissue, and
differentiate into macrophages
– Increase in # during chronic infections.
Platelets
• Platelets are fragments of megakaryocytes
• Platelets function in the clotting
mechanism –form a temporary plug that
helps seal breaks in blood vessels.
Platelet
Human Blood Groups
• RBC membranes have glycoprotein
antigens on their external surfaces
• These antigens are:
– Unique to the individual
– Recognized as foreign if transfused
into another individual
– Promoters of agglutination and are
referred to as agglutinogens
• Presence or absence of these
antigens is used to classify blood
groups
ABO Blood Groups
• The ABO blood groups consists of:
– Two antigens (A and B) on the surface of the RBCs
– Two antibodies in the plasma (anti-A and anti-B)
• Agglutinogens (antigens) and their corresponding
antibodies cannot be mixed without serious
reactions
Group A – has only the A antigen on RBCs (and B antibody in
the plasma)
Group B – has only the B antigen on RBCs (and A antibody in
the plasma)
Group AB – has both A and B antigens on RBCs (but neither A
nor B antibody in the plasma)
Group O – has neither A nor B antigens on RBCs (but both A
and B antibody are in the plasma)
• The universal donor has Type O
negative blood.
• The universal recipient has Type AB
positive blood.
Transfusion Reactions
• Transfusion reactions occur when mismatched blood
is infused
• Donor’s cells are attacked by the recipient’s plasma
agglutinins causing:
– Diminished oxygen-carrying capacity
– Clumped cells that impede blood flow
– Ruptured RBCs that release free hemoglobin into the
bloodstream
• Circulating hemoglobin precipitates in the kidneys
and causes renal failure
Rhesus (Rh) factor
• Is an inherited trait that refers to a specific
protein found on the surface of RBCs.
• If your blood has the protein, you're
Rh(+)— the most common Rh factor. If
your blood lacks the protein, you're Rh(-).
• Rh factor doesn't affect your health.
Rhesus (Rh) factor cont.
• When pregnant, blood from the baby can cross into the bloodstream. If
you're Rh(-)and your baby is Rh(+) your body will react to the baby's blood
as a foreign .
• Your body will create antibodies against the baby's Rh-positive blood.
• These antibodies usually don't cause problems during a first pregnancy.
• The antibodies stay in your body once they have formed. Thus, Rh
incompatibility is more likely to cause problems in later pregnancies (if the
baby is Rh-positive).
• The Rh antibodies can cross the placenta and attack the baby's red blood
cells. This can lead to hemolytic anemia in the baby, which is a condition
in which red blood cells are destroyed faster than the body can replace
them.
• Without enough red blood cells, the baby won't get enough oxygen. This
can lead to problems and can be fatal.