TY - CHAP M1 - Book, Section TI - Blood A1 - Mescher, Anthony L. Y1 - 2021 N1 - T2 - Junqueira's Basic Histology Text and Atlas, 16e AB - Blood SUMMARY OF KEY POINTSThe liquid portion of circulating blood is plasma, while the cells and platelets comprise the formed elements; upon clotting, some proteins are removed from plasma and others are released from platelets, forming a new liquid termed serum.Important protein components of plasma include albumin, diverse α- and β-globulins, proteins of the complement system, and fibrinogen, all of which are secreted within the liver, as well as the immunoglobulins.RBCs or erythrocytes, which make up the hematocrit portion (~45%) of a blood sample, are enucleated, biconcave discs 7.5 μm in diameter, filled with hemoglobin for the uptake, transport, and release of O2, and with a normal life span of about 120 days.WBCs or leukocytes are broadly grouped as granulocytes (neutrophils, eosinophils, basophils) or agranulocytes (lymphocytes, monocytes).All leukocytes become active outside the circulation, specifically leaving the microvasculature in a process involving cytokines, selective adhesion, changes in the endothelium, and transendothelial migration or diapedesis.All granulocytes have specialized lysosomes called azurophilic granules and smaller specific granules with proteins for various cell-specific functions.Neutrophils, the most abundant type of leukocyte, have polymorphic, multilobed nuclei, and faint pink cytoplasmic granules that contain many factors for highly efficient phagolysosomal killing and removal of bacteria.Eosinophils have bilobed nuclei and eosinophilic-specific granules containing factors for destruction of helminthic parasites and for modulating inflammation.Basophils, the rarest type of circulating leukocyte, have irregular bilobed nuclei and resemble mast cells with strongly basophilic-specific granules containing factors important in allergies and chronic inflammatory conditions, including histamine, heparin, chemokines, and various hydrolases.Lymphocytes, agranulocytes with many functions as T- and B-cell subtypes in the immune system, range widely in size, depending on their activation state, and have roughly spherical nuclei with little cytoplasm and few organelles.Monocytes are larger agranulocytes with distinctly indented or C-shaped nuclei, which circulate as precursors of macrophages and other cells of the mononuclear phagocyte system.Platelets are small (2-4 μm) cell fragments derived from megakaryocytes in bone marrow, with a marginal bundle of actin filaments, alpha granules and delta granules, and an open canalicular system of membranous vesicles; rapid degranulation on contact with collagen triggers blood clotting. SN - PB - McGraw Hill CY - New York, NY Y2 - 2024/03/28 UR - accessmedicine.mhmedical.com/content.aspx?aid=1184200517 ER -