Physiology Flashcards
How many oxygen molecules can one RBC carry? How does it do so?
4 oxygen molecules
2 alpha and 2 beta chains binding to each heme group
What is hematocrit?
Relative volume of RBC out of total blood count
How is reticulocyte count useful?
Helps determine if erythropoietin is normal
Where is erythropoiesis done in a fetus?
Yolk sac but upon maturation, in liver, spleen and lymph nodes
Where is erythropoiesis done in a child less than 5 years old?
Bone marrow
Where is erythropoiesis done in a teenager?
Bone marrow
Sternum
Vertebrae
Proximal end of long bone
Where is erythropoiesis done in an adult?
Bone marrow
Sternum
Vertebrae
How is regulation of erythropoiesis done?
By the kidneys.
Low oxygen delivery stimulate kidney release more erythropoietin
What happens during erythropoiesis?
Growth factors stimulate hematopoietic stem cells to give rise to proerythroblasts
Proerythroblasts develop into erythroblasts
Erythroblast loses its nucleus to form normoblasts and reticulocytes
Reticulocytes continue to synthesis and leave bone marrow for differentiation
How do RBC destruct?
Self rupture occurs where a lack of protein synthesis causes membrane to be fragile
Rupture into tiny vessels of spleen
Macrophage takes up dying component
How is iron from RBC recycled and stored?
Recycled in bone marrow
Stored in liver
How is globin from RBC recycled?
Metabolized to AA
Released into circulation
How is heme from RBC excreted?
Degraded to bilirubin
Excrete via liver and bile into urine and feces
Define anemia and name a few conditions associated with anemia
Reduction below normal capacity of blood to carry O2 due to decreased erythrocytes and hemoglobin
Examples include:
- Malaria
- Aplastic anemia
- Hemorrhagic anemia
- Sickle cell disease
Define polycythemia
An excess circulating erythrocytes causing elevated hematocrit
What are some conditions associated with polycythemia?
Tumour
Adaptive mechanism to high altitude places
Dehydration
Define leukocytosis
WBC higher than normal, more than 1.1 x 10 cells/ mm3
Why are people with leukemia more prone to getting cancer?
Immature WBC found along bloodstream of leukemia patients
When bone marrow becomes occupied with cancerous leukocytes, WBC being immature displaces remaining healthy ones and can cause issues such as immune deficiency
What are the three phases of hemostasis?
Vasoconstriction
Platelet plug
Fibrin clot formation
Why does vasoconstriction occur?
Decrease blood loss
Gives time for platelet and coagulation phase to occur
What happens during vasoconstriction
Endothelial cell contracts to expose the basal lamina
What is the purpose of platelet plug?
Closure of leak by formation of temporary patch
Release of chemical mediators to regulate blood clot
Contraction of blood clot
What happens during the platelet plug phase?
Damage to endothelial walls expose collagen
Platelets activated and stick
Platelets then secrete more content
More platelets are activated and aggregate into a plug
Formation of platelet plug occurs
Explain in details how the platelet adhesion step occurs
Von willebrand factor binds platelet to exposed collagen
Adhesion then activates platelet causing morphological changes and trigger release of platelet agonist
What are some platelet agonist?
ADP: Attracts and activates more platelets
Tbx A2: Promotes aggregation and vasoconstriction
Draw the common coagulation cascade pathway
Refer to notes for answer
Draw the intrinsic coagulation pathway
Refer to notes for answer
Draw the extrinsic coagulation pathway
Refer to notes for answer
What is the function of thrombin?
Enhance own generation by acting as positive loop
Activate factor XIII to stabilize fibrin mesh
Platelet activation
Release PF3 from platelets to activate intrinsic pathway
How does clot retraction occur?
Clot squeezes serum out of fibrin cloth and close leak
How does repair of clot occur?
PDGF stimulate vascular smooth muscle cell to build new vascular walls
Endothelial cells stimulated by VEGF multiply and restore inner endothelial lining
Describe what happens during fibrinolysis
During clot formation, plasminogen is trapped in clot
Surrounding tissue and vascular endothelial cells slowly release tPA which cleaves inactive plasminogen to protease plasmin
Plasmin digest fibrin to dissolve clot
Macrophage removes remaining of clot
What are the regulators of blood clot? Describe its mechanism of action
Prostacyclin: Inhibit platelet aggregation and spread of clot
Serotonin: Inhibit ADP
Blood clot: Limits spread of thrombin and other procoagulants
What does PTT measure?
Intrinsic and common coagulation cascade
What does PT measure?
Extrinsic and common coagulation cascade
What is INR?
Ratio of PT to general population’s PT
