17 10-19 Flashcards
Classes of Leukocytes
Granulocytes, Agranulocytes
Structural characteristics of leukocytes
3
Only formed elements that are complete cells - have nucleus and other organelles.
1.5-3x bigger than RBCs,
less than 1% of blood volume.
Function of leukocytes
Protect from bacteria, viruses, parasites, toxins, tumor cells
4 characteristics of circulating WBCs
- Can migrate out of the bloodstream (diapedesis), but most are found in tissues
- All are capable of amoeboid movement
- All are attracted to specific chemical stimuli (positive chemotaxis)
- Neutrophils/monocytes/macrophages are capable of phagocytosis
Leukocytosis
A WBC count of over 11k - normal in a homeostatic response to an infection.
Leukocytes in order from most to least abundant
Never let monkeys eat bananas
Granulocytes
4
Neutrophils/eosinophils/basophils.
Lobed nuclei (round with connecting strand),
granules stain visibly,
all phagocytic to some degree
Agranulocytes
Lymphocytes/monocytes. Lack visible granulocytes
Neutrophils
4
Actively phagocytize bacteria
chemically attracted to sites of inflammation,
multilobed nucleus (PMN),
granules contain defensin, respiratory burst.
Eosinophils
4
Kill parasitic worms with enzymes
phagocytize antigen-antibody complexes
are involved in allergic reaction by promoting inflammation,
levels often high in autoimmune/eczema
Basophils
5
Release histamine and other mediators.
Found in CT,
promote vasodilation in inflammation
Release heparin (anticoagulant) to inhibit blood clotting,
similar to mast cells (both bind to IgE) but arise from different cell,
Lymphocytes
4
Mount immune response by direct cell attack or via antibodies.
nucleus most of cell volume,
Includes T-lymphocytes/B-lymphocytes/NK cells,
hang out in lymphatic tissue
T cells
Manage and direct immune response and specialize in cellular immunity.
Act directly against virus-infected and tumor cells.
B cells
Play a role in humoral immunity.
Give rise to plasma cells which produce antibodies/immunoglobulins.
NK cells
Defense against infected and abnormal body cells.
Monocytes
Phagocytosis, develop into macrophages.
3-8% of leukocytes,
largest leukocytes,
kidney shaped nucleus,
“big eater” of bacteria/viruses/dead cells,
activate T cells.
New monocytes circulate in the blood for only a few hours before they migrate into the tissue to become macrophages. Some macrophages are fixed - some wander.
Leukopoiesis
4 different CSFs (colony stimulating factors) have been identified that stimulate formation of WBCs.
Interleukins are involved in leukopoiesis.
Differentiation occurs along two pathways: Lymphoid and Myeloid stem cells.
Hematopoietic stem cell/hemocytoblast –> myeloid or lymphoid
Leukopenia
Abnormally low WBC count
Leukemia
Clones of a single WBC that remain unspecialized and divide out of control.
Infectious mononucleosis
WBC issue arising from Epstein-Barr. Viral
Structure of platelets. 4
Not cells in a strict sense - they are cytoplasmic fragments of megakaryocytes.
Smaller than RBCs
contain mitochondria/SER but no nucleus (and age quickly because no nucleus).
Granules contain chemicals that aid in clotting process.
Function of platelets
Critical to clotting process - form seal/plug when a blood vessel breaks. Seal small tears in blood vessels.
Thrombopoiesis
2 points, 3 steps
Hormone thrompoietin regulates formation.
Repeated mitoses of the megakaryocytes without cytokinesis.
- Megakaryocyte presses against a sinusoidand sends cytoplasmic extensions thru.
- Extensions rupture releasing fragments into the blood.
- Plasma membranes seal around the cytoplasm to form platelets.