Physiology

Question 1

How many oxygen molecules can one RBC carry? How does it do so?

Answer 1

4 oxygen molecules
2 alpha and 2 beta chains binding to each heme group

Question 2

What is hematocrit?

Answer 2

Relative volume of RBC out of total blood count

Question 3

How is reticulocyte count useful?

Answer 3

Helps determine if erythropoietin is normal

Question 4

Where is erythropoiesis done in a fetus?

Answer 4

Yolk sac but upon maturation, in liver, spleen and lymph nodes

Question 5

Where is erythropoiesis done in a child less than 5 years old?

Answer 5

Bone marrow

Question 6

Where is erythropoiesis done in a teenager?

Answer 6

Bone marrow
Sternum
Vertebrae
Proximal end of long bone

Question 7

Where is erythropoiesis done in an adult?

Answer 7

Bone marrow
Sternum
Vertebrae

Question 8

How is regulation of erythropoiesis done?

Answer 8

By the kidneys.
Low oxygen delivery stimulate kidney release more erythropoietin

Question 9

What happens during erythropoiesis?

Answer 9

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

Question 10

How do RBC destruct?

Answer 10

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

Question 11

How is iron from RBC recycled and stored?

Answer 11

Recycled in bone marrow

Stored in liver

Question 12

How is globin from RBC recycled?

Answer 12

Metabolized to AA

Released into circulation

Question 13

How is heme from RBC excreted?

Answer 13

Degraded to bilirubin

Excrete via liver and bile into urine and feces

Question 14

Define anemia and name a few conditions associated with anemia

Answer 14

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

Question 15

Define polycythemia

Answer 15

An excess circulating erythrocytes causing elevated hematocrit

Question 16

What are some conditions associated with polycythemia?

Answer 16

Tumour

Adaptive mechanism to high altitude places

Dehydration

Question 17

Define leukocytosis

Answer 17

WBC higher than normal, more than 1.1 x 10 cells/ mm3

Question 18

Why are people with leukemia more prone to getting cancer?

Answer 18

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

Question 19

What are the three phases of hemostasis?

Answer 19

Vasoconstriction
Platelet plug
Fibrin clot formation

Question 20

Why does vasoconstriction occur?

Answer 20

Decrease blood loss

Gives time for platelet and coagulation phase to occur

Question 21

What happens during vasoconstriction

Answer 21

Endothelial cell contracts to expose the basal lamina

Question 22

What is the purpose of platelet plug?

Answer 22

Closure of leak by formation of temporary patch

Release of chemical mediators to regulate blood clot

Contraction of blood clot

Question 23

What happens during the platelet plug phase?

Answer 23

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

Question 24

Explain in details how the platelet adhesion step occurs

Answer 24

Von willebrand factor binds platelet to exposed collagen

Adhesion then activates platelet causing morphological changes and trigger release of platelet agonist

Question 25

What are some platelet agonist?

Answer 25

ADP: Attracts and activates more platelets

Tbx A2: Promotes aggregation and vasoconstriction

Question 26

Draw the common coagulation cascade pathway

Answer 26

Refer to notes for answer

Question 27

Draw the intrinsic coagulation pathway

Answer 27

Refer to notes for answer

Question 28

Draw the extrinsic coagulation pathway

Answer 28

Refer to notes for answer

Question 29

What is the function of thrombin?

Answer 29

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

Question 30

How does clot retraction occur?

Answer 30

Clot squeezes serum out of fibrin cloth and close leak

Question 31

How does repair of clot occur?

Answer 31

PDGF stimulate vascular smooth muscle cell to build new vascular walls

Endothelial cells stimulated by VEGF multiply and restore inner endothelial lining

Question 32

Describe what happens during fibrinolysis

Answer 32

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

Question 33

What are the regulators of blood clot? Describe its mechanism of action

Answer 33

Prostacyclin: Inhibit platelet aggregation and spread of clot

Serotonin: Inhibit ADP

Blood clot: Limits spread of thrombin and other procoagulants

Question 34

What does PTT measure?

Answer 34

Intrinsic and common coagulation cascade

Question 35

What does PT measure?

Answer 35

Extrinsic and common coagulation cascade

Question 36

What is INR?

Answer 36

Ratio of PT to general population’s PT