Chapter 17: Blood Flashcards
What are the three main functions of blood?
transport, regulation and protection
Transport Function
distribute o2, nutrients, and hormones to cells and metabolic wastes (co2 and nitrogenous wastes) to elimination sites
Regulation Function
maintains normal body temp, pH of body fluids and fluid volume in blood vessles
Protection Function
prevents blood loss and defends body against invading microorganisms
Characteristics of Blood
sticky, viscous fluid with a metalic taste (due to iron); color ranges from bright red (o2 rich, arteries) to dark red (o2 poor, veins); pH ranges from 7.35-7.45 (blood is slightly basic); volume varies by sex (5-6L in adult male and 4-5L in adult female)
Composition of Blood
consists of plasma (liquid portion) and 3 formed elements: erythrocytes, leukocytes, and platelets; components can be separated by centrifugation (WBC is the buffy coat); hematocrit values- healthy male 42-52%, healthy females 37-47%
Plasma
90% water and 10% solutes
What are the solutes found in plasma?
electrolytes (ions, na, k, ca, cl, hco3- bicarbonate); plasma proteins (albumin, globulins, fibrinogen, and most produced by liver); nitroginous substances (urea, uric acid, creatinine); nutrients (glucose, amino acids, fatty acids and glycerol, vitamins); respiratory gases (o2 and co2); hormones (steroids and TH transported by plasma protein)
Structure of Erythrocytes
biconcave disc (~7.5 micrometer diameter); at maturity lack a nucleus (anucleate) and mitochondria (so they only produce ATP by glycolysis); packed with hemoglobin molecules; each of which contains 4 heme hroups and 4 globin chains; life span about 120 days (filtered and recycled by spleen)
Function of Erythrocytes
transports respiratory gases; 98% of o2 transported from lungs to tissues is bound to the iron atom of heme; 20% of co2 transported from tissues to lungs is bound to globin (carbaminohemoglobin)
Erythropoiesis
RBC production; occurs in red bone marrow; derived from hematopoietic stem cell (aka heocytoblasts) (all blood cells come from this); mostly in axial skeleton
Phases of Erythropoiesis
hematopoietic cells to myoblast to proerythroblast (once at this phase it is committed to forming a RBC); phase 1- ribosome synthesis; phase 2- hemoglobin accumulation then phase 3- ejection of nucleus then a reticulocyte and then it enters the blood; whole process takes 15 days; process requires nutrients, vit. b12, folic acid, adnd iron
What regulates erythropoiesis?
erythropoietin (EPO) hormone synthesized by the kidney
Erythropoietin Mechanism
1) stimulus- hypoxia (inadequate o2 delivery) due to decreased RBC, decreased hemoglobin, decreased availability of o2; 2) kidney releases erythropoietin; 3) stimulates red marrow; 4) enhanced erythropoiesis increases RBC; 5) o2 carrying ability of blood rises
Fate of RBCs
aged and damaged red blood cells are engulfed by macropahges of spleen, liver, and bone marrow; hemoglobin is broken down; iron and amino acids are recycled; bilirubin is a waste product that the liver uses to make bile
Erythrocyte disorders are classified as either….
anemia or polyathemia
Anemia
reduced o2 carrying capacity of blood caused by blood loss, insuffience RBC production, or excessive destruction of RBC
Hemorrhagic Anemia
may be acute (rapid blood loss) or chronic (slow and persistent)
Iron Deficiency Anemia
inadequate intake or malaabsorption of iron
Pernicious Anemia
autoimmune disease; imune cells attack stomach mucosa cells that produce intrinsic factor (required for intestinal cells to absorb b12); mostly seen in elderly
Renal Anemia
lack of EPO (erythropoietin)
Aplastic Anermia
destruction or inhibition of red bone marrow; one of the reasons they do cancer treatments in cycles and not continuous
Thalassemias
genetic; one of the 2 beta globulin chain is absent or defective resulting in fragile RBC that rupture prematurely
Sickle Cell Anemia
genetic; beta globulin gene corder for production of beta globulin chains that have 1 amino acid substitution (val is swapped for glu at position 6); RBC rupture prematurely