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Feedback Control of Erythropoiesis

  • Imbalance

  • Stimulus

  • Reduces O2 levels in blood

  • Kidney releases erythropoietin

  • Erythropoietin stimulates red bone marrow

  • Enhanced erythropoiesis increases RBC count

  • Increases O2-carrying ability of blood

  • Normal O2 levels

What are 3 stimulae of the feedback control of erythropoiesis?
  • Hypoxia due to decreased RBC count
  • Decreased availability of O2 to blood
  • Increased tissue demands for O2
Do RBCs have oxidative capacity?
No
What fuels RBCs
Glucose
What does myeloid produce?

  • RBCs

  • Platelets

  • WBCs

What does lymphoid produce?
WBCs
Glycoprotein produced by the parietal cells of the stomach
Intrinsic Factor
Intrinsic factor is necessary for absorption of what?
Vitamin B12
How does intrinsic factor work?
It binds to B12 to protect it from gastric enzyimes
What decreases intrinsic factor?
Autoimmune attack of the parietal cells by Abs, leading to atrophic gastritis
Why can't Fe circulate freely, unbound?
Free iron recycled from RBCs causes the generation of O2 free radicals, which damage cells.
How is Fe transported in the blood?
Transferrin
What is Fe bound with in the liver?
Ferritin
Average lifespan of a RBC
120 days (~4 months)
Average lifespan of a platelet
10 days
Major reserve for RBCs and platelets
Spleen
4 Phases of Hemostasis
  • Vasoconstriction
  • Platelet Plug Formation
  • Activation of Clotting Cascade
  • Formation of a Blood Clot
Where do the intrinsic and extrinsic clotting pathways converge?
X - Xa
How do you assess the intrinsic clotting pathway?
PTT
What does PTT stand for?
Partial Thromboplasm Time
Which factors does the intrinsic pathway involve?

  • VIII

  • IX

Is the intrinsic pathway fast or slow?
Slow
How do you assess the extrinsic pathway?
PT
What does PT stand for?
Prothrombin Time
How is damage caused in the extrinsic pathway?
Sources external to the blood
Is the extrinisic pathway fast or slow?
Fast (clots form in 15 seconds)
Activation of the intrinsic pathway is caused by?
Contact with damaged blood vessel surface
Activation of the extrinsic pathway is caused by?
Damaged tissue
What is the end result of the intrinsic and extrinsic pathways?
Fibrine Clot
Once a clot is no longer needed, it is broken down
Fibrinolysis
What is the end product of fibrinolysis?

  • Fibrin Degradation Products (FDPs)

  • Fibrinogen

How are FDPs cleared?
By liver macrophages (Kupfer cells) and spleen macrophages
A balance between ______ and _____ creates normal hemostasis

  • Coagulation

  • Fibrinolysis

After RBCs die, what happens to heme?
Heme is converted to bilirubin, then it is taken to the liver for conjugation. It is then disposed of primarily in the feces and secondarily in the urine.
Conversion of bilirubin to a water-soluble form
Conjugation
Where does conjugation take place?
Liver
How is bilirubin excreted?

  • Feces (primary)

  • Urine (secondary)

After RBCs die, what happens to Fe?
It is released for recycling
The spleen is the site of RBC _____ in the fetus
Synthesis
The spleen is the site of RBC _____ in the adult
Clearance
White and red pulp sinuses of the _____ act as a strainer to selectively lyse out old RBCs
Spleen
The spleen can hold about _____ of blood for time of need
200cc
Asplenic individuals are at greater risk for what?
Infection
Does the spleen contain WBCs?
Yes
Where are all blood clotting factors produced?
Liver
Vitamin-K-dependant blood clotting factors

  • 2

  • 7

  • 9

  • 10

Blood can be stored in what organs for use in times of need?

  • Spleen

  • Liver

Conjugation is dependant upon the _____ of the liver.
Health
How does the liver store Fe?
Ferritin
What does the normal oxyhemoglobin dissociation curve tell us?
Relationship between PaO2 and Hgb saturation (the affinity between O2 and Hgb)
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