The Circulatory System: Blood Flashcards
How many liters of blood are in an average adult?
5 liters, but can range from 4-6
Common Functions of Blood
- Transport (O2, CO2, nutrients, waste, hormones, stem cells)
- Protection (prevent spread of infection, WBCs destroy microorganisms and cancer cells, produce antibodies, platelets secrete factors for clotting etc)
- Regulation (fluid distribution, pH, body temperature)
Blood Components
- Formed elements (cells, platelets)
- Fluid elements of the matrix (plasma)
Formed Element Classifications
- Erythrocytes
- Platelets
- Leukocytes
- Granulocytes:
- Neutrophils
- Eosinophils
- Basophils
- Agranulocytes
- Lymphocytes
- Monocytes
- Granulocytes:
Hematocrit
The percentage of total volume made up by the erythrocytes (usually 37-52%)
Components of Blood in a Centrifuge Sample (%)
Top to Bottom:
- Plasma (47-63%)
- WBCs and platelets (“Buffy coat,” 1% or less)
- Erythrocytes (37-52%)
Plasma Components
- Water
- Three Categories of Proteins:
1) Albumin
- transports solutes
- buffers pH of plasma
- viscosity and osmolarity
2) Globulins
- alpha, beta, gamma
- transport, clotting, immunity
3) Fibrinogen
- precursor of clotting fibrin - Nutrients
- Electrolytes
- Hormones
- Nitrogenous wastes
- Gases
5 Types of Leukocytes
Granulocytes
- Neutrophils
- Basophils
- Eosinophils
Agranulocytes
- Lympocytes
- MonocytesSerum
When the blood clots and solids are removed, remaining fluid is serum
Serum is essentially plasma without the clotting protein fibrinogen
Origin of Plasma Proteins
The liver produces all plasma proteins but gamma globulin which are generated by plasma cells (connective tissue cells that are descending from B lymphocytes)
Viscosity
The resistance of a fluid to flow based in the cohesion of its particles
- Blood viscosity is determined by the level of plasma proteins and formed elements
Osmolarity
The total molarity of dissolved particles that cannot pass through the blood vessel wall
- If blood molarity is too high (with respect to tissue molarity), the bloodstream will retain too much water which will increase blood volume and blood pressure
- If blood molarity is too low, the bloodstream will release too much water into the tissues, resulting in edema and low blood pressure
- Osmoreceptors in the brain detect changes in osmolarity to govern the release of ADH and stimulate thirst
pH of Blood
7.35-7.45
Hemopoiesis
- Tissues that produce blood cells are called hemopoietic tissues (mainly myeloid tissue aka red bone marrow, and lymphoid tissue such as the tonsils and thymus)
- Hemopoietic stem cells (HSCs, aka pluripotent stem cells or PPSCs) in the bone marrow give rise to all formed elements
- Most HSCs remain in the bone marrow but some go on to form colony-forming units (CFUs)
Internal Structure of Erythrocytes
- During maturation, erythrocytes lose their organelles and this contain no nucleus or mitochondria and rely on anaerobic respiration (they transport oxygen and therefore must not consume it)
- Cytoplasm contains hemoglobin
Lifespan of Erythrocytes
~120 days
- Are phagocytosed by macrophages in the spleen, liver, bone marrow
Structure of Hemoglobin
- Four protein chains called globins: 2 alpha and 2 beta chains
- Heme group containing ferrous ion (Fe++) that binds O2 to form oxyhemoglobin
- The globin portion binds CO2 to form carboaminohemoglobin
- Adult hemoglobin (HbA) and fetal hemoglobin (HbF) differ in structure; HbF had two gamma rather than best chains and binds oxygen with a higher affinity
Erythropoiesis
- Stimulated by hypoxia (low blood O2), the kidney and liver release erythropoietin (EPO)
Primary and Seconary Polycythemia (Polycthemia Vera)
- Excess RBCs
- Primary is cancer of the erythropoietic line of the red bone marrow
- Secondary is from all other causes
- Higher blood volume, BP, viscosity
Anemia
- Very low RBCs or hemoglobin
- Caused by inadequate erythropoiesis/hemoglobin, hemorrhagic anemia, hemolytic anemia
Iron-Deficiency Anemia
- small, pale RBCs
Pernicious Anemia
- deficiency of intrinsic factor to absorb B12
Aplastic Anemia
- destruction of bone marrow
Sickle-Cell Disease
- A recessive allele modifies hemoglobin so the cells are tapered and agglutinate, blocking blood vessels and causing pain to oxygen-deprived areas
- Heterozygous are trait carriers who exhibit limited symptoms and demonstrate resistance to malaria
Agglutination Terms for Blood Types
Agglutinogens – Antigens
Agglutinins – Antibodies
Universal Donor versus Recipient
AB = recipient (contains neither anti-A or -B agglutinins)
O = donor (contains both anti-A and -B)
Rh Factor
Group of antigens: C, D, E (D is the most common)
- Blood type is + or - based on presence or absence of D antigen
- Blood does not contain anti-D antibodies but will develop them upon exposure to Rh+ blood
Rh Factor and Pregnancy
- Rh- mother may be exposed to baby’s Rh+ blood during birth and will produce anti-D antibodies
- During a second Rh+ pregnancy, these antibodies can cross the placenta resulting in hemolysis
- Known as erythroblastosis fetalis or hemolytic disease of newborn
- Can be combated by injecting mother beforehand with globulins that intercept Rh+ antigens before she produces antibodies
- ex RhoGAM, passive immunization
Leukocyte Order of Abundance
N > L > M > E > B
Neutrophils
- Bacterial infections
- Nucleus consists of 2-5 lobes
- Called polymorphonuclear Leukocytes (PMNs)
- Reddish to violet granules
Eosinophils
- Allergies, parasitic infections, collagen diseases, diseases of spleen and CNS
- Bilobed nucleus
- Rosy to orange granules
Basophils
- Secrete histamine and heparin
- Abundant dark violet granules
- Histamine widens blood vessels to accelerate the flow of blood to injured tissues and makes them more permeable to neutrophils and clotting proteins
- Heparin inhibits blood clotting and promotes mobility of other WBCs
Lymphocytes
- Large nucleus with thin strip of cytoplasm
- Large, medium, and small varieties
- Medium and large typically in fibrous connective tissue, not usually circulating in blood
Monocytes
- Inflammation and viral infections
- Largest WBC
- Kidney- or U-shaped nucleus
- Cytoplasm contains fine granules
- Transform into macrophages in the tissue that destroy dead or dying host cells as well as foreign cells, pathogenic chemicals, etc
- Macrophages are called Antigen-presenting cells (APCs) because they display antigen fragments to alert the immune system
Leukopenia versus Leukocytosis
Leukopenia = Low WBC
- Lead, arsenic, mercury poisoning, radiation sickness, certain infectious diseases, glucocorticoids and certain anti-cancer drugs
Leukocytosis = High WBC
- Dehydration or emotional responses
Leukopoiesis
HSCs differentiate into distinct CFUs:
- Myeloblasts ultimately form the granulocytes
- Monoblasts form monocytes
- Lymphoblasts form lymphocytes
Leukemia
Cancer of hemopoietic tissues - can be classified as myeloid or lymphoid, acute or chronic
- Myeloid leukemia is marked by overproduction of granulocytes
- Lymphoid leukemia overproduces monocytes and lymphocytes
- Acute appears and progresses rapidly while chronic appears and progresses slowly
Thrombopoiesis
- Some HSCs have receptors for thrombopoietin released by the kidneys and liver and become megakaryoblasts
- Megakaryoblasts become megakaryocytes with multilobed nuclei and multiple chromosome sets
- Platelets are fragments of the megakaryocytes
Hemostasis
= cessation of bleeding
- Three mechanisms:
1) Vascular spasm
- Constriction of blood vessel, lasts until other two mechanisms can take over
2) Platelet plug formation
- Platelets detect exposed collagen fibers and form a platelet plug and undergo degranulation of serotonin, thromboxane, ADP
3) Blood clotting
- One of the most complex processes in the body
- Fibrinogen is converted to fibrin to collect more fibrin, blood cells and platelets
Platelet Granules Released in Platelet Plug Formation
Serotonin + Thromboxane = vasoconstriction and spasm
ADP + Thromboxane = plug formation
Two Pathways for Conversion of Fibrinogen to Fibrin
1) Extrinsic Mechanism - clotting factors released from source(s) other than blood - the damaged tissue (ex Thromboplastin)
2) Intrinsic Mechanism - clotting factors found in the blood itself
Fibrinolysis
- Dissolution of a clot
- Plasmin dissolves fibrin through a positive feedback loop
Hemophilia
- A blood clotting disorder where blood fails to clot due to lack of clotting factors
- Pain and joint immobility can result from hematomas (masses of clotted blood in the tissues)
Thrombosis
- Abnormal clotting of blood in an unbroken blood vessel
- A thrombus (clot) may cause blockages/break off to form an embolus that enters the bloodstream
- If a vessel that supplies O2 to a vital tissue is blocked, infarction ( or tissue death) may result
- ex Deep vein thrombosis pulmonary embolism
Citrate or EDTA as Anticoagulants
Citrate and EDTA are salts that bind Ca++ so it cannot participate in blood clotting
