Blood

Question 1

List the three sites of hemopoiesis in the body, in the order in which they occur during development.

Answer 1

1)yolk sac, 2)liver, 3)red marrow

Question 2

What determines whether a hematopoietic stem cell develops via the lymphoid or myeloid pathway?

Answer 2

the action of lymphokines or growth factors that bind to receptors in the cell membrane of the HSC

Question 3

Indicate whether each of the following develops via the lymphoid or myeloid pathways. a) erythrocytes

b) thrombocytes
c) neutrophils
d) monocytes e) basophils
f) eosinophils g) lymphocytes

Answer 3

a) erythrocytes (M)
b) thrombocytes (M)
c) neutrophils (M)
d) monocytes (M)
e) basophils (M)
f) eosinophils (M)
g) lymphocytes (L)

Question 4

A typical RBC last for about ______ (time).

Answer 4

120 days

Question 5

5) Describe the mechanism by which erythropoiesis is regulated (2 marks).

Answer 5

· the kidneys produce the hormone erythropoietin in response to low blood O2
· EPO stimulates development of erythrocytes from hematopoietic stem cells

Question 6

Describe three cellular events that occur during erythropoiesis.

Answer 6

1) hemoglobin synthesis
2) ejection of nucleus
3) loss of organelles including mitochondria (no oxidative phosphorylation)

Question 7

erythropoiesis is completed in about ________(time).

Answer 7

7-8 days

Question 8

List three substances that are required in the diet for synthesis of hemoglobin.

Answer 8

1) Iron
2) Vitamin B12
3) Folic acid

Question 9

Describe the roles of each of the following (1 mark each):

a) gastroferritin
b) transferrin
c) ferritin

Answer 9

a) a protein produced by the stomach that binds to dietary iron and assists its absorption from the small intestine
b) a blood protein that absorbs iron (mainly absorbed from intestine) and transfers it to other tissues (mainly the red bone marrow and liver)
c) a protein in the liver that binds to iron and allows it to be stored in hepatocytes until needed

Question 10

Describe how (and where) erythrocytes are degraded (3 marks).

Answer 10

• ageing erythrocytes are engulfed by macrophages in the spleen
• globin is digested to form amino acids( re-used)
• iron of heme is bound to transferrin and stored in spleen and liver
• porphyrin of heme is converted to bilirubin and transported to liver
• bilirubin is combined with sugars (conjugated) and released into bile
• bilirubin is converted to yellow compounds and excreted in urine
• or to brown compounds in the digestive tract by the action of bacteria

Question 11

List the three main stages of hemostasis.

Answer 11

• vascular spasm
• formation of platelet plug
• coagulation

Question 12

List two chemical vasoconstrictors that are released during hemostasis and the structures
that releases them (2 marks).

Answer 12

• thromboxanes (prostaglandins) and serotonin from platelets and
• endothelin from damaged endothelial cells

Question 13

Describe what platelet activation is, what causes it, and its effect (3 marks).

Answer 13

• platelets are activated by contact with collagen
• activation results in release of substances that cause platelets to adhere to each other and to collagen and fibrin (ADP and thromboxanes (prostaglandins)
• a platelet plug blocks the flow of blood from a damaged vessel and forms the form for attachment of fibrin and cells (thrombus)

Question 14

The final stage of coagulation involves the conversion of _______ to ________; a reaction
that is catalyzed by _____________.

Answer 14

a) fibrinogen
b) fibrin
c) thrombin

Question 15

Outline the two main ways in which coagulation can be initiated (2 marks).

Answer 15

• the release of tissue factor (III) from damaged cells

- the release of factor XII from platelets that are activated by contact with collagen

Question 16

List four sources of coagulation factors (2 marks).

Answer 16

1) secreted into the blood by the liver
2) released into the blood by activated platelets
3) released by damaged tissues
4) calcium from diet

Question 17

Describe the roles of calcium in coagulation.

Answer 17

calcium is needed for activation of factors in both the extrinsic and intrinsic pathways; therefore it is required for coagulation to occur

Question 18

Why is factor X sometimes called the “common factor?”

Answer 18

factor X is activated by either the intrinsic or extrinsic mechanism

Question 19

Explain what clot retraction is, what causes it and the role it plays in hemostasis.

Answer 19

• the decrease in volume of the clot due to gradual contraction of actin and myosin within platelets
• results in edges of wound being pulled together and serum being squeezed out of clot

Question 20

Name two anticoagulants produced by the body and where they are produced.

Answer 20

antithrombin: produced by liver, slowly inactivates thrombin
heparin: produced by basophils and endothelial cells

Question 21

Outline the process of fibrinolysis, the molecules involved, how they are activated and the
general role of fibinolysis (3 marks).

Answer 21

• fibrinolysis is the enzyme-catalyzed conversion of fibrin strands to soluble fibrin
• it is catalyzed by the enzyme called plasmin
• plasmin is formed from the plasma protein plasminogen by the action of tPA (tissue plasminogen activator)
• tPA is released from cells of damaged tissue