Unit III: HomeostasisBlood

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

Centrifuge

Withdrawblood

Plasma(55% of whole blood)

Buffy coat: leukocytesand platelets(<1% of whole blood)

Erythrocytes(45% of whole blood)

Formedelements

Blood Composition

• Adults have 4-6 L of blood

• Plasma – – Water, proteins, nutrients, electrolytes,

nitrogenous wastes, gases, and hormones (Table 18.2 p. 687)

• Serum– Lacks fibrinogen

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:HypoxiaDecreased blood osmolarityDecreased 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 Antigen Phenotype

AA A A

AO A A

BB B B

BO B B

AB A and B AB

OO Neither O

A AB

BAB BA

AB A 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

HemostasisVascular 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