Chapter 19 The Circulatory System I Blood

Cardiovascular System The cardiovascular system includes: Blood The Heart Blood Vessels –Large and small arteries and arterioles –Large and small veins and venules –Capillaries

Blood A liquid connective tissue made up of plasma and formed elements. BLOOD COMPOSITION: Serum: the liquid portion of blood after it has clotted ( fibrinogen has clotted). Plasma: liquid portion of blood Water – 92% by weight Proteins – 6-9 gm/dl; most abundant plasma solute Formed elements (rbc, wbc and platelets)

Blood fractions

Blood

Blood Proteins Albumin is the major contributor to plasma viscosity and osmolarity. Albumin- smallest and most abundant protein; serves to transport plasma solutes and buffer the pH of blood plasma. Fibrinogen- soluble precursor of fibrin, a sticky protein that forms framework for clotting. Globulins- 3 classes: alpha (α), beta (β) and gamma (γ) (smallest to largest) in molecular weight.

Formed Elements Red blood cells (rbc) = erythrocytes ~45-50% pcv* White blood cells (wbc) = leukocytes ~ < 1% pcv* –Granulocytes- neutrophils, eosinophils and basophils –Agranulocytes- lymphocytes and monocytes Thrombocytes = platelets part of buffy coat < 1% * = packed cell volume

Erythrocytes (RBC’s) Cell Structure: biconcave disc 7 μm diameter X 2 μm thick. -anucleated cells (no nucleus or other cellular organelles) Production: erythropoiesis is stimulated by erythropoietin hormone from kidneys. -From infancy on, all rbc’s are produced in red bone marrow. They are produced from pluripotent stem cells (PPSC). Contain 4 hemoglobin molecules/rbc; Life span of a rbc ~ days

Erythrocytes (RBC’s)

Hemoglobin Erythrocytes contains 4 hemoglobin molecules Hemoglobin is a complex molecular structure of two chains: α chain is 141 amino acids; β chain is 146 amino acids. Heme groups is bound to each chain and contains ferrrous iron (Fe+2). Iron is where O2 binds to each Hgb molecule binds ~ 250 million molecules O2 X 4 = 1 billion molecules O2 /rbc.

Hemoglobin molecular structure Star shapes are Heme (Fe+2) molecules Dark blue chain is β, light blue is α

Blood types Most familiar blood types is ABO groups and Rh group. Blood type antigens are carried on red blood cell membranes. Bloods A,B,O and AB comprise the ABO group O is “universal donor”; AB is “universal recipient”. Rh factor may be – or + and can result is immune reactions if not properly matched.

Hematopoiesis

Leukocytes (WBC’s) Cell Structure: 4,800 – 11,000/cm -Spherical cells containing a nucleus and other organelles. The nucleus of each cell type varies considerably in leukocytes and is quite conspicuous and helps in identifying each cell type. Production: -stimulated by two cytokines: (interleukin and colony stimulating factor [CSF]). -All wbc’s are produced from PPSC by a process called leucopoiesis. WBC’s are produced in red bone marrow and may remain there until needed in the body or they may migrate to other organs for further differentiation. Number ranking: NLMEB

WBC’s

Granulocytes Composed of wbc’s that contain granules in their cytoplasm: Neutrophils – most plentiful in blood 60% of wbc’s Eosinophils – 1 – 4% of wbc’s Basophils- least plentiful of all wbc’s ~ 0.5% wbc’s

Neutorphils Nucleus looks like sausage links – multilobed - account for 50% of wbcs- -3,000 to 7,000/cc -Life span- 6 hrs – few days - phagocytize bacteria

Eosinophils Bilobed nucleus Account for 1-4% of wbc Red staining granules Life span- 8 – 12 days Kill parasitic worms, active in allergies

Basophils Bilobed nucleus “U” or “S” Account for < 0.5% wbc Dark bluish-purple staining granules Life span- hrs. - days Contain histamine, and inflamatory substances

Agranulocytes Conspicuous granules are lacking in the cytoplasm. Composed of: Lymphocytes and Monocytes. Lymphocytes are most important in immune system in lymph nodes, Peyers patches, and spleen.

Lymphocytes Round nucleus fills most of cytoplasm Account for % of wbc Similar size to neutrophils Life span- hrs. to years Two types: “B” and “T” B cells mature in red bone marrow T cells start in red marrow and mature in Thymus gland

Monocytes Largest wbc’s in circulation Large “U: shaped or kidney shaped nucleus Account for 4-8% of wbcs Life span- months Active in clotting to plug holes until clot can form. Become macrophages after release from red bone marrow into circulation Macrophages are major phagocytes in body

Thrombocytes (platelets) Cellular fragments very small under microscope. ~ 250,000 platelets/ cc Contain serotonin, Ca++, enzymes and platelet growth factor. Stick together to form plugs and stop bleeding (hemostasis). and stop bleeding (hemostasis). Picture is of a megakaryocyte from which platelets are produced.

Blood clot of fibrin and platelets and other blood cells