white blood cells and platelets

What are leukocytes?

White blood cells (WBCs) that function in body defense.

What percentage of total blood volume do leukocytes make up?

Less than 1%.

What type of cells are leukocytes?

Complete cells.

What process allows leukocytes to leave the bloodstream?

Diapedesis.

What is leukocytosis?

Elevated white blood cell count.

What is leukopenia?

Decreased white blood cell count.

What are granulocytes?

Leukocytes with cytoplasmic granules and lobed nuclei (PMNs).

What are agranulocytes?

Leukocytes lacking cytoplasmic granules (PBMCs).

High neutrophil count usually indicates what?

Bacterial infection.

What are eosinophils and what do they do?

2-4% of WBCs; attack parasites and involved in allergies and asthma.

What are basophils and what do they release?

Least common WBCs; release histamine for inflammation.

What are lymphocytes?

20-25% of WBCs; basis of adaptive immunity.

What do T lymphocytes do?

Directly attack virus-infected and tumor cells.

What do B lymphocytes do?

Produce antibodies as plasma cells.

What are monocytes?

3-8% of WBCs; become macrophages and perform phagocytosis.

What is leukopoiesis?

Formation of white blood cells.

Which stem cells produce lymphocytes?

Lymphoid stem cells.

Which stem cells produce granulocytes, monocytes, platelets, and RBCs?

Myeloid stem cells.

What are band cells?

Immature granulocytes.

What is leukemia?

Cancer where abnormal WBCs divide uncontrollably.

What are platelets?

Cell fragments from megakaryocytes involved in clotting.

How long do platelets live?

About 10 days.

What hormone regulates platelet formation?

Thrombopoietin.

What is hemostasis?

Process of preventing blood loss.

What are the three steps of hemostasis?

Vascular spasm, platelet plug formation, coagulation.

What is vascular spasm?

Vasoconstriction to reduce blood loss.

What do platelets bind to during plug formation?

Exposed collagen fibers.

What type of feedback loop occurs during platelet plug formation?

Positive feedback loop.

What is coagulation?

Conversion of blood from liquid to gel.

What are the three stages of clotting?

Formation of prothrombin activator, conversion of prothrombin to thrombin, conversion of fibrinogen to fibrin.

What are the two clotting pathways?

Intrinsic and extrinsic.

Which pathway is faster?

Extrinsic pathway.

What limits clot formation?

Rapid blood flow and clotting inhibitors.