1. Hematopoeisis and Hemostasis
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2. Hematopoiesis The process of blood cell formation
Includes all blood cells- red and white
Occurs in red bone marrow from stem cells known as hemocytoblasts
Hemocytoblast differentiation
Lymphoid stem cell produces lymphocytes
Myeloid stem cell produces all other formed elements
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3. Figure 10.4 The development of blood cells.
Hemocytoblast
stem cells
Lymphoid
stem cells
Myeloid
stem cells
Secondary stem cells
Basophils
Erythrocytes
Platelets
Eosinophils
Lymphocytes
Monocytes
Neutrophils

4. Production controls over formed elements
Because RBCs are anucleate they cannot divide, grow, or synthesize proteins
Life span of 100 to 120 days
phagocytes in the spleen/liver eliminate remains
New RBCs produced by hemocytoblasts in the red bone marrow (a 3-5 day process)
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5. Control of Erythrocyte Production
erythropoietin : hormone that controls RBC production rate
Produced by kidneys in response to O2 levels
Targets bone marrow to mfr RBCs
negative feedback maintains blood oxygen levels (see figure 10.5 on page 346)
works by increasing/decreasing erythropoietin release
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6. Figure 10.5 Mechanism for regulating the rate of RBC production.
Slide 1
IMBALANCE
Homeostasis: Normal blood oxygen levels 1
Stimulus 5
O2–carrying
ability of blood
increases.
Low blood O2–carrying
ability due to
• Decreased RBC count
• Decreased amount of
hemoglobin
• Decreased availability
of O2
IMBALANCE 4
Enhanced
erythropoiesis
increases RBC
count. 2
Kidney (and liver,
to a smaller extent)
releases erythropoietin. 3
Erythropoietin
stimulates red bone
marrow.

7. Production of WBCs and Platelets
A group of Colony stimulating factors (CSFs) and interleukins prompt bone marrow to generate leukocytes
CSFs are specific to the types of WBCs they act on
used to stimulate cell production in cancer patients undergoing chemo or radiation therapy
Hormone thrombopoietin stimulates production of platelets from megakaryocytes
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8. Hemostasis- blood clotting
involves three phases:
Vascular spasms
Platelet plug formation
Coagulation (blood clotting)
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9. Vascular Spasms Vasoconstriction causes blood vessel to spasm
Narrowing of the blood vessel
Slows blood loss
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10. Figure 10.6 Events of hemostasis.
Slide 2
Step 1
Vascular spasms occur.
Smooth muscle contracts, causing vasoconstriction.

11. Platelet Plug Formation
Collagen fibers are exposed by a break in a blood vessel
Platelets become “sticky” and cling to fibers
Anchored platelets release chemicals to attract more platelets
A positive feedback mechanism
Platelets pile up to form a platelet plug (white thrombus)
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12. Figure 10.6 Events of hemostasis.
Slide 3
Step 2
Platelet plug forms.
Injury to lining of vessel exposes collagen fibers; platelets adhere.
Collagen
fibers
Platelets release chemicals that make nearby platelets sticky; platelet plug forms.
Platelets

13. Coagulation
Clotting factors in blood plasma and injured tissue cells interact with Ca²⁺ to produce the enzyme thrombin
Thrombin catalyzes the joining of fibrin molecules to make a meshwork that traps RBCs and platelets
This forms the clot, which is broken down after repair of damaged tissue
This mechanism is controlled so that the presence of the clot inactivates the factors that initiated the response
To avoid clotting of all blood in the body
cascade.html
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14. Figure 10.6 Events of hemostasis.
Slide 4
Step 3
Coagulation events occur.
Clotting factors present in plasma and released by injured tissue cells interact with Ca2+ to form thrombin, the enzyme that catalyzes joining of fibrinogen molecules in plasma to fibrin.
Fibrin
Fibrin forms a mesh that traps red blood cells and platelets, forming the clot.

15. Figure 10.7 Fibrin clot.

16. Undesirable Clotting Thrombus Embolus Potential causes:
A clot in an unbroken blood vessel
Can be deadly in areas such as the heart
Embolus
A thrombus that breaks away and floats freely within the bloodstream
Potential to clog vessels in critical areas
Potential causes:
Burns
Physical blows
Fatty material (plaque)
Slow blood flow
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17. Bleeding Disorders Thrombocytopenia Liver problems Hemophilia
Platelet deficiency
Results from bone marrow suppression
Cancer, radiation, drugs, autoimmune condition, bacteria
Evidenced by petechiae (purplish skin blotches)
Liver problems
due to cirrhosis, hepatitis, or low Vitamin K stores
Liver synthesizes the clotting proteins
Hemophilia
Hereditary bleeding disorder
Normal clotting factors are missing
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