Blood

Function Transport dissolved materials Regulates pH & electrolyte balance in interstitial fluid Restriction of blood loss Stabilizes body temperature Defense against pathogens

Components of Blood When settled, blood separates into 3 layers – Top liquid layer = plasma – Middle layer = “buffy coat” = white blood cells & platelets – Bottom solid layer = red blood cells Hematocrit is the % that is cells – 45% is average

Origin of Cells Hematopoietic stem cells in red bone marrow – RBCs – WBC Thrombopoietin stimulates proliferation of megakaryocytes – Break apart into platelets

Platelets Aka Thrombocytes Hemostasis = stoppage of bleeding – Smooth muscle contracts lessening loss – Platelets adhere to rough edges of injury = platelet plug Grab to each other Release serotonin which causes more contraction

Hemostasis Coagulation = blood clot formation Extrinsic – Blood exposed to broken vessels Intrinsic – Blood exposed to foreign substance Either triggers a chain of reactions leading to formation of fibrin – insoluble protein threads

Bruise comes from collected blood lost, but hemostasis prevents further loss Material eventually removed by phagocytes

Red Blood Cells Aka Erythrocytes 1/3 hemoglobin, rest is water, electrolytes, & enzymes Concave shape increases surface area & provides more access to hemoglobin Transport gases

White Blood Cells Aka leukocytes Protect against disease Can exit vessels via diapedesis and move on their own (amoeboid motion) 5 types; 2 categories – Granulocytes: granular cytoplasm – Agranulocytes: no granules is cytoplasm

Neutrophils Fine, light-purple granules Lobed nucleus (2-5 sections) First to arrive at infection site Phagocytize bacteria, fungi, & some viruses

Eosinophil Coarse, uniform, deep-red granules Bi-lobed nucleus Moderate allergic reactions & defend against parasites

Basophils Similar to eosinophils but with irregular, blue granules (often obscure nucleus) Release histamine & heparin Inflammation & clot inhibition to promote blood flow

Monocytes Largest, agranular, variety of nuclear shapes Leave bloodstream and become macrophages Phagocytize bacteria, dead cells, & debris

Lymphocytes Similar in size to erythrocytes Agranular, large spherical nucleus, thin ring of cytoplasm T cells Directly attack B cells Produce antibodies

White Blood Cell Count The proportion of WBCs is a diagnostic tool