Blood

what type of connective tissue is blood?

a discontinuous tissue: cells are made in bone marrow and thymus but function elsewhere

composed of cells suspended in a liquid extracellular matrix, blood plasma, that can turn semisolid by clotting

which organs build and regulate blood plasma?

the liver and kidneys

what percentage of body weight does blood make up?

more than 10% (with blood and hematopoietic bone marrow)

what are the functions of blood?

O2 and CO2 transport (RBCs), immune defense (WBCs), vessel integrity and clotting (platelets)

what percentage of plasma is water?

about 90%

what are the low-molecular weight solutes in blood?

Na+, K+, Ca2+, HCO3-, glucose; concentrations and pH regulated by the kidneys and lungs

what are the functions of albumin in blood?

the most abundant plasma protein (3-5g/100 mL)

drives oncotic pressure, carries fatty acids, hormones, drugs

what is the function of fibrinogen in blood?

cleaved to fibrin and cross-linked into a clot; fluid left after clotting is serum

what are the functions of alpha and beta globulins?

transport metal ions, inhibit proteases, participate in inflammation

where are most plasma proteins synthesized?

in the liver

what values does the complete blood count (CBC) report?

RBC number, volume, and hemoglobin content plus the WBC differential (percentages of WBC types)

what is the normal differential for blood?

neutrophils 60-70%

lymphocytes 25-30%

monocytes 3-7%

eosinophils 1-3%

basophils 0-1%

what color ranges do Wright and Giemsa stains give?

eosinophilic red-orange, basophilic purple-black, neutrophilic pink-tan, and polychromatophilic blue-gray

what is the size of red blood cells?

about 7um across (range 6-8 um) and 2 um thick

what is the structure of a red blood cell?

biconcave disc shape produces central pallor; uniform staining signals loss of biconcavity

shape gives high surface to volume ratio for diffusion and passive deformability through capillaries under 7 um

no organelles; energy comes from glycolysis and the pentose-phosphate pathway

membrane skeleton - actin and spectrin tetramers linked by ankyrin and protein 4/1 to band 3 and glycophorin - maintains the disc

what percentage of whole blood and blood cells do red blood cells make up?

40-50% of blood volume

99% of all blood cells

what is the function of red blood cells in moving O2 and CO2?

CO2 diffusing into RBCs is converted by carbonic anhydrase to carbonic acid, which dissociates to HCO3-

the bulk of CO2 returns to the lungs as bicarbonate and the reaction reverses for exhalation

RBCs are the only formed elements that stay in blood for their entire lifespan

what is anemia?

reduced functional hemoglobin from fewer or smaller RBCs, or less hemoglobin per cell; causes weakness and fatigue

what is polycythemia?

raised hematocrit driven by low tissue O2 from lung disease or altitude

what is sickle cell disease?

point-mutant HbS polymerizes when deoxygenated; rigid sickled cells occlude vessels and survive under 20 days

what is Thalassemia?

imbalanced globin chains precipitate on the membrane; stiffened cells are culled in the spleen

what is hereditary spherocytosis?

defective spectrin, ankyrin, or band 3; spleen remodels cells into inflexible spheres without central pallor, often treated by splenectomy

what are granulocytes?

neutrophils, eosinophils, basophils: innate immunity, 12-15 um spheres with lobed nuclei and diagnostic granules

what are monocytes?

innate immunity; precursors of macrophages

what are lymphocytes?

B and T cells of adaptive immunity, plus NK cells of innate immunity

where do WBCs work?

outside the blood vessel: they circulate, exit, then act in tissue or undergo apoptosis

how are granulocytes separated?

by granule staining, which tracks directly with their function

what are the structural features of neutrophils?

most numerous WBC (about 60%); under a week in blood and about a day in tissue

multilobed nuclei - two to five lobes increasing with age → polymorphonuclear neutrophil (PMN)

what do the granules of neutrophils carry?

azurophilic primary granules carry defensins; specific secondary granules carry lysozyme and respiratory-burst enzymes

how do neutrophils act?

for tissue entry: selectins slow rolling, chemokines activate integrins, tight binding then diapedesis

chemotaxis to the source, then phagocytosis and killing by granule fusion and O2 radicals; spent cells become pus

what are some inherited defects of neutrophils?

failed respiratory burst produces granulomas; defective integrins cause leukocyte adhesion deficiency

what is the structure of eosinophils?

about 2% of WBCs

bilobed nucleus, bright orange secondary granules

what is the function of eosinophils?

they kill targets too large to engulf by exocytosing major basic protein, peroxidase, and collagenase onto IgE-coated parasites

eosinophil accumulation in airways drives chronic asthma through the same cytotoxic granules

what is the structure of basophils?

under 1% of WBCs

dark basophilic granules obscuring a multilobed nucleus

what is the function of basophils?

granules hold histamine, heparin, chemokines, and proteases, released when antigen cross-links surface IgE

results in raised vascular permeability and recruitment of other immune cells - useful in infection, destructive in allergy

what is the structure of monocytes?

about 5% of leukocytes and the largest blood cells at 12-20 um, with an indented kidney or U-shaped nucleusw

hat is the function of monocytes?

they circulate 1-2 days, enter tissue, and mature into macrophages that live for months and can divide

macrophages phagocytose pathogens and debris, release chemokines that recruit neutrophils, and present antigen to lymphocytes

what are the characteristics of lymphocytes?

about 30% of circulating WBCs; lifespan ranges form weeks to years

small lymphocytes (6-8 um, 85-95%) are T cells (65-75%) and B cells (5-25%), separable only with antibody reagents

large lymphocytes are NK cells and antigen-activated cells; B cells become antibody-secreting plasma cells

what is the structure of platelets?

anucleate fragments 2-3 um across with mitochondria, ER, lysosomes, microtubules, and an actomyosin cytoskeleton

granules store serotonin, platelet-derived growth factor, and clotting factors

how do platelets function?

endothelium keeps them inactive; exposed collagen at a rupture triggers avid binding and activation

activated platelets aggregate into plugs, reinforce and then contract the fibrin clot, and release repair factors for fibroblasts

about 10% of platelets maintain routine vessel integrity; the rest are reserve for larger wounds