Unit III: Homeostasis
Blood
Chapter 18
pp. 684 - 699
Review
1. The most effective buffer in the intracellular fluid is:
a.) phosphate; b.) protein; c.) bicarbonate; d.) carbonic acid
2. A blood pH of 7.2 caused by inadequate pulmonary ventilation
would be classified as _________.
3. Tubular secretion of hydrogen ions would cease if the acidity of
the tubular fluid fell below a value called the _________.
4. (T/F) The bicarbonate system buffers more acid than any other
chemical buffer.
5. Acids ____________ hydrogen ions in a solution, whereas,
bases _______ them.
Functions of Circulatory System
• Fundamental purpose: transport substances from place to place
• Transport
– O2, CO2, nutrients, wastes, hormones, and stem cells
• Protection
– Inflammation, WBCs, antibodies, and platelets
• Regulation
– fluid regulation, buffering, and heat
Blood Composition
• Adults have 4-6 L of blood
• Plasma –
– Water, proteins, nutrients, electrolytes,
nitrogenous wastes, gases, and hormones
Withdraw
blood
(Table 18.2 p. 687)
• Serum
– Lacks fibrinogen
Centrifuge
Plasma
(55% of whole blood)
Buffy coat: leukocytes
and platelets
(<1% of whole blood)
Erythrocytes
(45% of whole blood)
Formed
elements
Plasma Proteins
• 3 major categories of plasma proteins: (Table 18.3 p. 687)
– albumins - most abundant
• contributes to viscosity and osmolarity  influences blood
pressure, flow and volume
– globulins (antibodies)
• provide transport, clotting, and immunity
• alpha, beta and gamma globulins
– fibrinogen
• precursor of fibrin  help form blood clots
• Plasma proteins formed by liver
– except gamma globulins (produced by plasma cells)
Formed Elements of Blood
•Erythrocytes
•Platelets
•Leukocytes
–Granulocytes
Neutrophils
Eosinophils
Basophils
–Agranulocytes
Lymphocytes
Monocytes
Properties of Blood
• Viscosity – whole blood 5 times as viscous as water
• Osmolarity (total molarity of dissolved particles that can’t pass
through blood vessel wall)
– high blood osmolarity
• raises blood pressure
– low blood osmolarity
• lowers blood pressure
Properties of Blood
• Hematocrit – (packed cell volume)
– Females: 37-48%
– Males: 45-52%
• pH: 7.35 - 7.45
• RBC count:
– Females: 4.2-5.4 million/µL
– Males: 4.6-6.2 million/µL
• Total WBC count: 5000 – 10,000 /µL
• Volume/Body weight: 80-85 mL/kg
– Female: 4-5L
– Male: 5-6L
Erythrocytes (RBCs)
• Disc-shaped cell with thick rim
• Gas transport
– increased surface area/volume ratio
• due to loss of organelles during maturation
• increases diffusion rate of substances
– 33% of cytoplasm is hemoglobin (Hb)
• O2 delivery to tissue and CO2 transport to lungs
• Carbonic anhydrase (CAH)
Erythrocytes and Hemoglobin
• Common measurements:
– Hematocrit
– Red blood cell count
– hemoglobin concentration of whole blood
• men 13-18g/dL; women 12-16g/dL
• Values are lower in women
– androgens stimulate RBC production
– women have periodic menstrual losses
– Hematocrit is inversely proportional to % body fat
Erythropoiesis
• 2.5 million RBCs/sec (hematocrit value of 20mL of RBC/day)
• Development takes 3-5 days
– reduction in cell size, increase in cell number, synthesis of
hemoglobin and loss of nucleus
• Erythrocyte colony forming unit (ECFU)
– erythropoietin (EPO) 
• Erythroblasts multiply and synthesize hemoglobin 
• Discard nucleus to form a reticulocyte
– 0.5 to 1.5% of circulating RBCs
Erythrocyte Homeostasis
• Negative feedback control
– drop in RBC count causes kidney
hypoxemia
– EPO production stimulates bone
marrow
– RBC count  in 3 - 4 days
• Stimulus for erythropoiesis
– hemorrhaging, blood loss
– low levels O2
– abrupt increase in O2 consumption
– loss of lung tissue in emphysema
Anemia
•Inefficient amount of red blood cells
•Causes:
 inadequate erythropoiesis
•Kidney failure
•Iron-deficiency
•Vitamin B12 deficiency
 blood loss
 RBC destruction
•Consequences:
Hypoxia
Decreased blood osmolarity
Decreased blood viscosity
Erythrocyte Disorders
Sickle Cell Disease and Thalassemia
• Hereditary Hb ‘defect’ of African Americans and Mediteraneans
– recessive allele modifies hemoglobin structure
– sickle-cell trait - heterozygous for HbS
• individual has resistance to malaria
– sickle-cell disease - homozygous for HbS
• individual has shortened life
– low O2 concentrations  sickle shape
– stickiness  agglutination  blocked vessels 
– intense pain; kidney and heart failure; paralysis; stroke
Antigens and Antibodies
• Antigens (agglutinogens)
– unique molecules on all cell surfaces
• used to distinguish self from foreign
• Antibodies (agglutinins)
– secreted by plasma cells
– Appear 2-8 months after birth; reach maximum at 10 yr.
– Transfusion reaction
• Agglutination
– antibody molecule binds to >2 antigens
– Antigen-antibody complex
ABO Blood Groups
• Your ABO blood type is determined by presence or absence of
agglutinogens on RBCs and agglutinins in blood plasma.
Antigen on RBC Antibody in plasma
– type A:
A
anti-B
– type B:
B
anti-A
– type AB:
A and B
neither
– type O:
neither
anti-A and anti-B
• most common/universal donor - type O
• Rarest/universal recipient - type AB
Type A
Type B
Type AB
Type O
© Claude Revey/Phototake
ABO Group Genetics
• A and B alleles are dominant over O; but codominant to each other
Genotype
AA
AO
BB
BO
AB
OO
Antigen
A
A
B
B
A and B
Neither
Phenotype
A
A
B
B
AB
O
A
AB
AB
AB
B
A
A
B
B
Rh Group
• 3 antigens: C, D, E
• Rh (D) agglutinogens
– Rh+ blood type has D agglutinogens on RBCs
– Rh frequencies vary among ethnic groups
• Anti-D agglutinins not normally present
– form in Rh- individuals exposed to Rh+ blood
• no problems with first transfusion or pregnancy
Leukocytes (WBCs)
•
•
•
•
5,000 to 10,000 WBCs/L
Conspicuous nucleus
Travel in blood before migrating to connective tissue
Protect against pathogens
Leukocyte Descriptions
• Granulocytes
– neutrophils (60-70%) - fine granules; 3 to 5 lobed nucleus
•  in bacterial infections
– eosinophils (2-4%) - large rosy granules; bilobed nucleus
•  in parasitic infections or allergies
– basophils (<1%) - large, violet granules
•  in chicken pox, sinusitis, diabetes
• Histamine and heparin
Leukocyte Descriptions
• Agranulocytes
– lymphocytes (25-33%) - round, uniform dark violet nucleus
•  in diverse infections and immune responses
– monocytes (3-8%)
• largest WBC; ovoid, kidney-, or horseshoe- shaped nucleus
•  in viral infections and inflammation
Leukopoiesis
• Leukocyte life cycle
– pluripotent stem cells  CFU’s
• myeloblasts – form neutrophils, eosinophils, basophils
• monoblasts - form monocytes
• lymphoblasts - form 3 types of lymphocytes
– Colony-stimulating factors (CSF)
• WBCs provide long-term immunity (decades)
Abnormal Leukocyte Counts
• Leukopenia - low WBC count (<5000/L)
– causes: radiation, poisons, infectious disease
– effects: elevated risk of infection
• Leukocytosis = high WBC count (>10,000/L)
– causes: infection, allergy and disease
– differential count - distinguishes % of each cell type
• Leukemia = cancer of hemopoietic tissue
– myeloid and lymphoid - uncontrolled WBC production
– acute and chronic - death in months or  3 years
– effects – deficiency of competent formed elements; impaired
clotting
Platelets
• Small fragments of megakaryocyte
– no nucleus
– 40% stored in spleen
• Normal Count - 130,000 to 400,000 platelets/L
• Functions:
– vasoconstrictors
– platelet plugs
– secrete clotting factors
– initiate formation of clot-dissolving enzyme
– phagocytize bacteria; chemically attract neutrophils and
monocytes to sites of inflammation
– secrete growth factors
Hemostasis
• All 3 pathways involve platelets
Hemostasis
Vascular Spasm
• Causes
– pain receptors
– smooth muscle injury
– platelets release serotonin (vasoconstrictor)
• Effects
– prompt constriction of a broken vessel
• pain receptors - short duration
• smooth muscle injury - longer duration