NUR 195 Ch 19 Nursing Assessment:
Hematologic Function
Anatomic & Physiologic Overview - correct answer ✔✔- Hematologic system consists of blood & site
where blood is produced (e.g. bone marrow & reticuloendothelial system or RES)
- RES: complex sys of cells throughout body capable of phagocytosis
- Blood: specialized organ that differs from other organs in that it exists in a fluid state; composed of
plasma & various types of cells
- Plasma: fluid portion of blood; thin, colorless, contains various proteins, other factors necessary for
clotting, electrolytes waste products, & nutrients
- 55% of blood volume is plasma & 45% consists of various cellular components
Blood
(Table 19-1) - correct answer ✔✔- Cellular component of blood consist of 3 primary cell types:
erythrocytes (RBCs), leukocytes (WBCs), & thrombocytes (platelets)-- Approx 45% of blood volume
- Blood cells have short lifespan, so they need to be continuously replenished by the process called
hematopoiesis (formation & production of blood cells)--the primary site of this process is bone marrow
- RBCs live for 120 days, WBCs live from days to yrs depending on type, & platelets live 7-10 days
- Adult bone marrow produces approx 175 bill. RBCs, 70 bill. neutrophils (mature WBCs), & 175 bill.
platelets each day
- When body needs more blood cells, in infection or bleeding, marrow increases production of cells
required
- Blood is approx 7-10% of normal body weight & amounts to 5-6L of volume
- Blood carries O2 absorbed from lungs & nutrients absorbed from GI tract to body for cellular
metabolism; it also carries proteins (e.g. hormones, antibodies) to their sites of action as well as waste
products from cellular metabolism to lungs, liver, & kidneys for elimination
- Excessive clotting is equally as dangerous as excessive blood loss b/c it can instruct blood flow to vital
tissues--to prevent this, the body has fibrinolytic mechanism that dissolves clots formed in blood vessels
- The balance b/w clot formation & clot dissolution (fibrolysis) is called hemostasis
Bone Marrow
, (Figure 19-1) - correct answer ✔✔- W/ aging, marrow activity is usually limited to the pelvis, ribs,
vertebrae, & sternum
- Marrow: accounts from 4-5% of total body weight; consists of islands of cellular components (red
marrow) separated by fat (yellow marrow); highly vascular
- As adults age, the proportion of active marrow is gradually replaced by fat; but in the healthy person,
the fat can again be replaced by active marrow when more blood cell production is required
- In adults w/ disease that causes bone marrow destruction, fibrosis, or scarring, the liver & spleen can
also resume production of blood cells by process known as extra medullary hematopoiesis
- Stem Cells: primitive cell, capable of self-replication & differentiation into myeloid (differentiate into
RBCs, WBCs, & platelets) or lymphoid (differentiate into T or B lymphocytes) stem cell
- Defect in a myeloid stem cell can cause problems w/ RBC, WBC, & platelet production
Erythrocytes ( RBCs)
(Figure 19-2) - correct answer ✔✔- Normal RBC: biconcave disk shape; diameter approx 8um; flexible &
can easily pass through capillaries so that it can be as small as 2.8um in diameter; membrane is thin so
gases (like O2 & CO2) can easily diffuse across it; disk shape provides a large surface area that facilitates
absorption & release of O2 molecules
- Mature RBCs: consist primarily of hemoglobin (contains iron & makes up 95% of cell mass); have no
nuclei; large amount of hemoglobin allows red cel to perform principal function of O2 transport
- Reticulocytes: slightly immature RBCs; an elevation of these may occur as response to an increase
demand for RBCs or in some disease states
- O2- carrying hemoglobin molecule is made up of 4 subunits, each containing a heme portion attached
to glob in chain--iron is present in heme component
- Heme: important property is its ability to bind to O2 loosely & reversibly
- Oxyhemoglobin: combined form of O2 & hemoglobin; found in arterial blood; brighter red than
hemoglobin that contains lesser amounts of O2 (reduced hemoglobin)--this is why arterial blood is
brighter than venous blood
- In venous blood, hemoglobin combines w/ hydrogen ions produced by cellular metabolism & thus
buffers excessive acid
- Whole blood normally contains 15g of hemoglobin per 100mL of blood
Erythropoiesis - correct answer ✔✔- Erythroblast: arise from primitive myeloid stem cells in bone
marrow; is an immature nucleated cell that accumulates hemoglobin & gradually loses nucleus--known
as reticulocyte at this stage; further maturation into a RBC entails loos of dark-staining material within
cell & slight shrinkage--mature RBC is then released into circulation
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