White Blood Cells and Platelets

Question 1

Leukocytes

Answer 1

• WBCs (white blood cells, less than 1% of blood volume)
• The only formed element that are complete cells
• Critical for our defense against disease

Question 2

Diapedesis

Answer 2

• When WBCs leave the blood to enter the tissues
• Moving through tissue in an ameboid movement in extracellular fluids

Question 3

Leukocytes functions

Answer 3

• Exhibit positive chemotaxis
• Leukocytosis

Question 4

Positive chemotaxis

Answer 4

The following of WBCs to chemical trails of molecules from damaged cells as they migrate towards tissue damage and infection

Question 5

Leukocytosis

Answer 5

An elevated WBC count
Characteristic of infection as different types of WBCs are activated by different types of infection

Question 6

Granulocytes

Answer 6

• Major group of leukocytes
• Large cells with lobed nuclei and visibly staining granules
• Phagocytic
• Also known as Polymorphonuclear cells (PMNs)

Question 7

Agranulocytes

Answer 7

• Lymphocytes and monocytes that lack visibly staining granules
• Also known as Peripheral Blood Mononuclear Cells (PBMCs)

Question 8

Neutrophils

Answer 8

• 55-70% of all leukocytes (active phagocytes)
• Increased count is indicative of a bacterial infection
• pinkest-looking cell with a multi-blob (nucleus)

Question 9

Eosinophils

Answer 9

• 1-4% of leukocytes
• Attack parasites in loose connective tissue (asthma and allergies)
• Effective against multicellular endoparasites (worms)
• Reddest looking leukocyte, more grainy than neutrophils

Question 10

Basophils

Answer 10

• Least numerous types of leukocyte (0.5-1%)
• Release histamine to promote inflammation
• Associated with multicellular exoparasites (ticks)
• Almost entirely purple, nucleus not visible under microscope

Question 11

Lymphocytes

Answer 11

• 20-40% of leukocytes
• T lymphocytes: directly attack infected cells and tumour cells
• B lymphocytes: Bind antigens and produce antibodies as plasma cells
• Natural killer (NK) cells: similar functions as T cells but are part of the innate immune response

Question 12

Monocytes

Answer 12

• 2-8% of leukocytes
• Enter tissues and activate lymphocytes
• Common in chronic infections and inflammatory autoimmune diseases
• Active phagocytic macrophages to clean up dead cells

Question 13

Leukopoiesis

Answer 13

Formation of white blood cells
- Regulated by the production of interleukins and colony-stimulating factors (CSF)

Question 14

Differentiation of hemocytoblasts

Answer 14

2 Pathways of leukopoiesis
- Lymphoid stem cells develop into lymphocytes
- Myeloid stem cells develop into all other WBCs, platelets and RBCs

Question 15

Band cells

Answer 15

Immature granulocytes like reticulocytes are immature erythrocytes

Question 16

Leukopenia

Answer 16

• An abnormally low WBC count from drugs like glucocorticoids or anticancer cells

Question 17

Leukemia

Answer 17

• Cancers in which clones of a single WBC remain unspecialized and divide out of control

Question 18

Infectious mononucleosis

Answer 18

Disease caused by Epstein-Barr virus that provokes the body to create lots of B cells and they all get infected

Question 19

Platelets

Answer 19

Not complete cells, but fragments of megakaryocytes (bone marrow cells)
- Lifespan of approximately 10 days
- Critical to the blood clotting process

Question 20

Thrombopoietin

Answer 20

A hormone that regulates the formation of platelets by the repeated mitoses of megakaryocytes without cytokinesis

Question 21

Hemostasis

Answer 21

• Prevention of blood loss
  3 Steps:
• Vascular spasms
• Platelet plug formation
• Coagulation (blood clotting)

Question 22

Vascular spasms

Answer 22

Immediate vasoconstriction by the smooth muscle in response to blood vessel injury, causing less blood to flow so other mechanisms can begin

Question 23

Platelet plug formation

Answer 23

When the endothelium is damaged, platelets stick to exposed collagen fibres forming the platelet plug
- When activated, the platelets swell, become spiked and stick to each other and the damaged blood vessel wall
- This activates a positive feedback loop

Question 24

Coagulation

Answer 24

A multi-step process where the blood goes from liquid to gel
- Reinforces platelet plugs with fibrin threads
- Pro/anticoagulant; factors that promote or inhibit clot formation

Question 25

3 stages of the clotting process

Answer 25

• Formation of prothrombin activator through intrinsic/extrinsic pathways
• Prothrombin activator catalyzes the transformation of prothrombin to thrombin
• Thrombin converts soluble fibrinogen to fibrin, fibrin causes the plasma to turn into gel, thrombin also activates the fibrin stabilizing factor to cross-link fibrin into a strong mesh to stabilize the clot

Question 25

Intrinsic pathway

Answer 25

• This is called this because all factors necessary are present in the blood
• This is a slower clotting pathway but can clot blood
• Does not play a major role in injuries

Question 26

Extrinsic pathway

Answer 26

• triggered through an endothelium-derived glycoprotein tissue factor (TF)
• Can occur rapidly by bypassing some steps of the intrinsic pathway
• Much more important for clotting blood

Question 27

Clot retraction

Answer 27

The contractile proteins (myosin and actin) within platelets contract and pull on neighbouring fibrin strands, squeezing the plasma to clot and pulling damaged tissue edges together

Question 28

Platelet-derived growth factor

Answer 28

This stimulates repair by endothelial cell division

Question 29

Fibrinolysis

Answer 29

This removes unneeded clots through the action of the fibrin-digesting enzyme, plasmin

Question 30

Factors limiting clot formation

Answer 30

• Rapidly moving blood spread apart clotting factors before they can start clotting
• Activated clotting factors are inhibited by other compounds in the blood, they need to have a minimum concentration for clotting to occur
• Vascular endothelium being smooth and intact prevents platelets from clotting