Blood: It’s more than just red stuff. Plasma: 55% The fluid portion of blood. Water accounts for over 90% (so then what is “serum”?) Plasma with the clotting factors removed. Contains: Electrolytes- to maintain osmotic balance, buffer Nutrients Respiratory gases Hormones So, if blood is 55% plasma, the rest must be ….._________ CELLS!

Blood: Erythrocytes- also called Red Blood Cells (RBCs) Erythrocytes- also called Red Blood Cells (RBCs) So, what about those cells? Leukocytes- Leukocytes- Transport oxygen (which binds to Hemoglobin) Lack nuclei or mitochondria also called white blood cells (WBCs) Function in defense and immunity DO have nuclei & mitochondria Basophils Lymphocytes Eosinophils Neutrophils Include: Actually spend most of their time in interstitial fluid and the lymphatic system.

A “Blood’s life”…… White blood cell life spans vary depending on: White blood cell life spans vary depending on: Type of WBC Immunity demands put upon the organism Red blood cell life span? Red blood cell life span? …about 3 months. Destroyed by phagocytes in the liver and spleen New cells are formed from “multipotent” stem cells in bone marrow (mostly flat bones: ribs, pelvis, sturnum) Production accelerated by negative feedback: Low Oxygen levels in tissues  Kidney secretes EURITHROPOIETIN  Stimulates RBC production!

Clotting: a real fixer-upper… Clotting: a real fixer-upper… Platelets: Platelets: 1.Clump & stick to the jagged edges of the cut. Provides immediate but temporary “plug” 2. Release clotting factors which catalyze the reaction: Fibrinogen  Fibrin Fibrin aggregates to form the clot 3. Also releases PDGF Who remembers what THAT stands for??? ______________ ______________ ____________ ______________ PlateletDerivedGrowthFactor! Plasma membrane receptors (called tyrosine kinases) that allow the signal transduction and inevitably the cell division stimulation to occur….allow a cell to skip the G1 checkpoints in order to divide!