Blood

Question 1

List the 5 functions of blood

Answer 1

• transport of dissolved substances
• regulation of pH + ions
• restriction of fluid losses at injury sites
• defense against toxins + pathogens
• stabilises body temp

Question 2

What are the 2 components of blood as percentages

Answer 2

• 55% plasma
• 45% formed elements -> erythrocytes, leukocytes + thrombocytes

Question 3

What is hematocrit a measure of

Answer 3

% RBC in whole blood

• male = 47%
• female = 42%

Question 4

List the 2 branches of cells hemacytoblasts differentiate into

Answer 4

1. myeloid stem cells
   -> RBCs, platelets, eosinophils, basophils, neutrophils + monocytes
2. Lymphoid stem cells
   -> lymphocytes

Question 5

List the characteristics of RBCs

Answer 5

• 99% of formed elements
• high SA:V ratio
• no mito. / enucleate
• can bend or flex to enter small capillaries
• haemoglobin binds to CO2 + O2

Question 6

Describe the regulation of erythropoiesis

Answer 6

Controlled by erythropoietin (EPO)
- requires amino acids, iron, B12, B6 + folic acid

Question 7

List circumstances when EPO would be released

Answer 7

• anaemia
• decreased blood flow to kidney
• damage to respiratory surface in lung
• decreased O2 in lungs

Question 8

Describe the function of leukocytes

Answer 8

• accumulate at sites of infection/inflammation + initiate a response

Question 9

Describe the characteristics of thrombocytes

Answer 9

• cell fragments involved in human clotting system
• disc shaped / no nuclei
• removed by spleen

Question 10

List the 3 functions of platelets

Answer 10

• release important clotting chemicals
• temporarily patch damaged vessels
• actively contract tissue after clot formation

Question 11

List the 3 phases of hemostasis

Answer 11

• vascular phase
• platelet phase
• coagulation phase

Question 12

Describe the vascular phase of hemostasis

Answer 12

• vascular spasm (lasts up to 30 mins)
  -> contraction of smooth muscle of blood vessel wall caused by:
• damage to smooth muscle/endothelium
• activation of platelets
• reflexes initiated by pain receptors

Question 13

Describe the platelet phase of hemostasis

Answer 13

• beings within 15 secs of injury
• platelet plug formation -> platelets adhere to damaged tissue in vessel wall
• platelets activated + extend projections to attach to each other (+ve feedback loop)
• clotting compounds released

Question 14

Describe the coagulation phase of hemostasis

Answer 14

• begins 30+ secs after injury
• clotting factors eg. enzymes promote production of prothrombinase
  -> converts prothrombin (produced by liver) into thrombin
  -> thrombin converts soluble fibrinogen into fibrin
  -> fibrin forms threads which trapped formed elements + form clot

Question 15

Explain how clot retraction + repair occurs

Answer 15

• platelets pull on fibrin threads -> clot contracts drawing wound edges closer together
• fibroblasts form connective tissue + new endothelial cells repair vessel lining -> clot eventually dissolved through action of plasmin