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Phys Exam 3: Ch 32

Red Blood cells

QuestionAnswer
What are the contents of a RBC, and what are the fxns of its components? Cytoplasm contains: (1) Hb - carries 4 O2 molecules per molecule Hb; (2) Carbonic anhydrase, to form bicarb, to cary CO2 from tissues to lungs
What is the concentration of RBCs? 4.5-5.2x10^6 RBC/mm^3
Where are RBCs produced before birth? Mostly liver, but also spleen & lymph nodes
Where are RBCs produced after birth? Bone marrow; before age 5: marrow of all bones; In adults: marrow of axial bones (skull, ribs, sternum, pelvis), and only the proximal ends of long bones
What is the average life span of RBCs? 100-120 days
Calculate the production rate of RBCs (5x10^6/mm^3)/120 days = 1.5x10^8/min per day
Lay out the RBC family tree Hematopoietic stem cell --> committed stem cell --> erythroblast --> erythrocyte
What is the fxn of erythropoietin (EPO)? EPO is a "differentiation enhancer": is required for differentiation into proerythroblasts (CFU-E)
What is an Hematopoietic stem cell (HSC)? uncommitted stem cells; basis of all blood cells
What are colony-forming unit-erythrocytes (CFU-E)? A committed stem cell
What is an erythroblast? cell fills w/Hb; nucleus condenses
What is a reticulocyte? some organelles remain, cell leave marrow by diapedesis into capillaries
What can the reticulocyte count be used to measure? Usedas index to rate of RBC formation
What is an erythrocyte? Mature RBC
What stimulates differentiation of HSCs? Response to decreased O2 levels, the juxtaglomerular cells of the kidneys secrete EPO
What stimulates secretion of EPO? Secreted in response to lower O2 delivery to the juxtaglomerular cells of the kidney; due to hemorrhage, anemia, high altitude, cardiac failure
Discuss injection of EPO To increase [RBC] and O2 delivery to tissues - in severe anemia, after chemo, or to enhance athletic performance
How can an elevated hematocrit cause blood vessel blockage? Elevated hematocrit + dehydration increases viscosity --> blockage
What structures are missing from an RBC? Nucleus, mitochondria, and ER
How is ATP produced in RBCs? Anaerobic glycolysis
Describe recycling of Hb after RBCs burst After cells burst in the spleen, the resident macrophages phagocytize Hb; Kupffer cells in the liver also do this
Where to worn-out RBCs burst? Spleen, mostly
Review RBC life cycle image
Describe disposal of Hb Globin is broken into AAs; Iron is transported on transferrin to tissues and stored on ferritin; Heme group is converted to bilirubin and secreted into bile, bile is secreted into the intestine
Where is iron stored? Mostly in liver, also pancreas, heart
Discuss how the body prevents the toxic bilirubin from depositing in the brain Bilirubin deposits in the brain are toxic, some is converted to urobilin in the intestine, reabsorbed, and excreted
What causes jaundice? Heme converted to bilirubin is not all going into bile, instead into blood
Discuss Hemochromatosis Excess Fe absorption and storage
What causes Hemochromatosis Genetic, excess Fe intake, deficiency of hepcidin (a protein that blocks Fe transport across the gut); Fe is excreted only by epithelial shedding and menstruation; Free ion catalyses formation of free radicals and is toxic
What are the sx of Hemochromatosis? Cirrhosis of the liver, diabetes, cardiomyopathy, arthritis, joint pain
How do you detect Hemochromatosis? Serum ferritin levels, MRI
What is the tx for Hemochromatosis? Phlebotomy (removal of a volume of blood), chelating agents (binds Fe from diet), and long term nutritional therapy
What is Anemia? A Hb deficiency in the blood
What is Iron Deficiency Anemia? Low Fe absorption; intestinal Fe absorption is normally very slow
What is Hemorrhagic Anemia? Excess blood loss
How is diabetes caused by Hemochromatosis? Fe is stored in pancreas, causing destruction of Beta cells by free radicals
How is cardiomyopathy caused by Hemochromatosis? Fe is stored in heart tissue, causing destruction of myocytes by free radicals
What is Pernicious Anemia? Vitamin B12 deficiency
What is Aplastic Anemia? Bone marrow deficiency
What is Sickle Cell Anemia? Abnormal Hb
What is Hemolytic Anemia? Destruction of RBCs
What causes Iron Deficiency Anemia? Most common cause in US is hemorrhage (menstruation, GI bleeding due to ulcer, polyp, tumor); Most common cause world-widen is parasitic infection (schistosomiasis, hookworm, amoeba; is Urinary and GI type of anemia
What is the most common Anemia? Iron Deficiency Anemia
What are the sx of Iron Deficiency Anemia? small RBCs w/reduced Hb content (microcytic, hypochromic)
What causes Aplastic Anemia? Damage to bone marrow by chemicals, radiation, infection, autoimmune disease; 50% of cases have unknown cause
What is/are the population(s) most affected by Aplastic Anemia? teens (autoimmune) and the elderly (accumulated damage, unknown causes)
What is the most common cause of death due to Aplastic Anemia? Radiation exposure
What are the tx of Aplastic Anemia? Immunosuppressive theray, stem cell transplant
What causes the vitamin B12 deficiency of Pernicious Anemia? Autoimmune destruction of parietal cells of the stomach that produce Intrinsic Factor
What are the sx of Pernicious Anemia? Enlarged, fragile, and fewer RBCs (megaloblastic); demyelination and neuropathy, paresthesia, ataxia, depression, paralysis
Describe Intrinsic Factor A glycoprotein secreted by the parietal cells of the stomach, binds to to vitamin B12 in food, blocks digestion of B12, binds to intestinal cells and enables absorption of B12
Describe the fxn of vitamin B12 regenerates folate, another B12 enzyme is essential for myelin production
Tx of B12 deficiency vitamins, injection of B12
Why is folate important? required for thymine production & DNA synthesis
Describe Sickle Cell Anemia 1 AA change in Hb sequence produces HbS; in conditions of low O2 (exercise, exertion) HbS forms long crystals inside the RBCs; these rigid RBCs jam in the capillaries, esp in joints
What does Sickle Cell Anemia cause? Ischemia, more crystal formation, pain, enlarged spleen, kidney damage, infarctions, strokes
Why does Sickle Cell Anemia still around? Malaria parasite cannot reproduce in RBCs w/HbS, so a heterozygote has a survival advantage
Describe how Malaria causes Hemolytic Anemia Parasite lives w/in liver cells & RBCs; after asexual multiplication the host cell is lysed and the progeny infects other cells, cell lysis releases histamine causing shock; decreased [RBC] causes anemia
What are some causes of Hemolytic anemia? Malaria, Rh disease, Some venoms (ex: rattlesnakes), some drugs (usually as part of an immune response)
How does Rh disease cause Hemolytic anemia? Abs from Rh- mom develop agains Rh factor in blood of Rh+ baby; these ABs cause agglutination and lysis of RBCs
What drugs can cause Hemolytic anemia? penicillin, L-dopa, quinine
Created by: hclark86