Transcript Homeostasis: Blood

Unit III: Homeostasis
Blood
Chapter 17
pp. 575-585
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
Presence of Potassium in Blood
Hypokalemia
<2 mEq/L in blood:
• muscular
weakness
•paralysis
Hyperkalemia
Normal potassium
levels in serum
(3.5–5.5 mEq/L)
Factors Promoting Hypokalemia
Diuretics (Lasix)
Aldosteronism
↑ volume of urine overstimulates sodium
produced
retention & potassium
loss
>8 mEq/L in blood
• cardiac arrhythmias
Factors Promoting Hyperkalemia
Chronically low
body fluid pH
Kidney failure
Several drugs promote
diuresis by blocking Na
reabsorption at the
kidneys.
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:
– 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 (packed cell volume)
– 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
Events Occurring in the Red Bone Marrow
Multipotent stem cells
Start
Proerythroblasts stimulated
by erythropoietin (EPO)
Macrophages in liver,
spleen, and bone marrow
Fe2+
Amino
Heme acids
90%
Biliverdin
Bilirubin
10%
Fe2+ transported
in circulation
by transferrin
Average life span of
RBC is 120 days
RBC
formation
Erythroblast
Roughly four days of
differentiation
Hemolysis
Ejection of
nucleus
New RBCs
released into
circulation
Retilculocytes remain in the
bone marrow for 2 more days
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 :
RBC
Surface antigens
Opposing antibodies
Antigen-antibody complex
Hemolysis
ABO Blood Groups
• Your ABO blood type is determined by presence or absence of
agglutinogens on RBCs and agglutinins in blood plasma.
Type A
RBCs with antigen A only.
Surface
antigen A
Type B
RBCs with antigen B only.
Type AB
RBCs with both A and B
antigens.
Type O
RBCs lacking both A and B
antigens.
Surface
antigen B
Plasma contains anti-B
Plasma contains anti-A
antibodies, which will attack antibodies.
Type B surface antigens.
Plasma contains both
Plasma has neither
anti-A nor anti-B antibodies. anti-A and anti-B antibodies.
• most common/universal donor - type O
• Rarest/universal recipient - type AB
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
Hemolytic Disease of the Newborn
Rh–
mother
First Pregnancy of an Rh– Mother
with an Rh+ infant
Rh+
fetus
Maternal blood supply
and tissue
Rh+
fetus
These antibodies destroy
fetal RBCs  dangerous anemia.
Placenta
Fetal blood supply
and tissue
Exposure to fetal red
blood cell antigens
generally occurs
during delivery.
Second Pregnancy of an Rh– Mother
with an Rh+ Infant
Maternal anti-Rh antibodies present.
During First Pregnancy
Very few fetal cells
enter the maternal
circulation.
Rh–
mother
Need for blood cells ↑
During Second Pregnancy
Maternal
Leave bone marrow underdevelopment.
Maternal
antibodies
Hemorrhaging at Delivery
Maternal
Fetal
Hemolysis of
fetal RBCs
Fetal
Rh antigen on
fetal red blood cells
A woman’s first infant Maternal Antibody Production
is not affected.
Maternal antibodies
Maternal
to Rh antigen
Results of blood typing tests on blood samples from four individuals
Anti-A
Anti-B
Anti-D
Blood
type
A+
B+
AB+
O–