Ch 11 Blood
Functions of Blood
• Deliver O2
• Remove metabolic wastes
• Maintain temperature, pH, and fluid volume
• Protection from blood loss- platelets
• Prevent infection- antibodies and WBC
• Transport hormones
Plasma-55%
Buffy coat-<1%
Red Blood Cells -45%
Composition of Blood
• Erythrocytes (red blood cells)
• Leukocytes (white blood cells)
• Platelets (thrombocytes)
90% Water
8% Solutes:
• Proteins
• Albumin (60 %)
• Globulins (38%)
• Fibrinogens (4%)
• Gas
• Electrolytes
• Organic Nutrients
• Carbohydrates
• Amino Acids
• Lipids
• Vitamins
• Hormones
• Metabolic waste
• CO2
• Urea
• Platelets
• Leukocytes
(WBC)
•
•
•
•
Small fragments of megakaryocytes
Formation is regulated by thrombopoietin
Blue-staining outer region, purple granules
Granules contain serotonin, Ca2+, enzymes,
ADP, and platelet-derived growth factor
(PDGF)
Platelets
Stem cell
Hemocytoblast
Developmental pathway
Promegakaryocyte
Megakaryoblast
Megakaryocyte
Platelets
Figure 17.12
• Erythrocytes (red blood cells)
Erythrocytes
Erythrocyte7.5m in dia
 Anucleate
 Function- transport respiratory gases
 Life span 100-120 days and then
destroyed in spleen (RBC recycling
center)
Hemoglobin
Hematopoiesis
The process of blood cell formation
• Location: red bone marrow of
axial skeleton
Erythropoiesis
Process of red blood cell formation
Hematopoiesis: Blood Cell Production
Hormones and growth factors push the
cell toward a specific pathway of blood
cell development
Hemocytoblasts
•
Erythropoiesis
Phases in development
1. Ribosome synthesis
2. Hemoglobin accumulation
3. Ejection of the nucleus and formation of
reticulocytes
• Reticulocytes then become mature erythrocytes
Stem cell
Hemocytoblast
Committed
cell
Developmental
Phase 1
Ribosome
synthesis
Proerythroblast
Early
erythroblast
pathway
Phase 2
Hemoglobin
accumulation
Late
erythroblast
Normoblast
Phase 3
Ejection of
nucleus
Reticulo- Erythrocyte
cyte
Regulation of Erythropoiesis
• Too few RBCs leads to tissue hypoxia
• Hypoxia: low oxygen levels
• Too many RBCs increases blood viscosity
• Viscosity: Thick, Sticky, semifluid
• Balance between RBC production & destruction
depends on:
• Hormonal controls
• Adequate supplies of iron, amino acids, and B
vitamins
Regulation of Erythropoiesis
• Causes of tissue hypoxia:
• Hemorrhage or increased RBC destruction
• Insufficient hemoglobin (e.g., iron deficiency)
• Reduced availability of O2 (e.g., high altitudes)
Hormonal Control of Erythropoiesis
• Erythropoietin (EPO)
• Stimulates
erythropoiesis
• Released by kidneys
in response to hypoxia
Hormonal Control of Erythropoiesis
• Effects of EPO
• More rapid maturation of committed bone
marrow cells
• Increased circulating reticulocyte count in
1–2 days
• Testosterone also enhances EPO
production, resulting in higher RBC counts
in males
Formation & Destruction of RBCs
Leukocytes
4,000-11,000 cells/mm 3
Never let monkeys eat bananas
Granulocytes: granules in cytoplasm
Neutrophils- 40-70%
Eosinophils- 1-4%
Basophils- <1%
Agranulocytes: no granules in cytoplasm
Monocytes- 4-8%
Lymphocytes- 20-45%
Neutrophil
Basophil
Lymphocyte
Eosinophil
Monocyte