CHAPTER 18 - CARDIOVASCULAR SYSTEM: BLOOD Flashcards
Describe the general functions of blood.
Transportation
- Oxygen and nutrients to the cells
- Co2 and waste away from the cells
Protection
- Protect against pathogens
- Protects against blood loss
Regulation
-Regulates temperature (absorbs heat from cells and releases at skin blood vessels)
-Regulates pH
-Regulates fluid balance
Name six characteristics that describe blood, and explain the significance of each to health and homeostasis.
1) Color
- oxygen-rich = bright red
- oxygen-poor = dark red
2) Volume
- about 5 liters in an adult
3) Viscosity
- 4 to 5 times thicker than water
- resistance to flow
4) Plasma concentration
- determines direction of osmosis
5) Temperature
- 1 degree Celsius higher than body temperature
6) Blood pH
- crucial for normal plasma protein shape
List the three components of a centrifuged blood sample.
Erythrocytes, Buffy Coat, Plasma
Define hematocrit, and explain how the medical definition differs from the clinical usage
Percentage of volume of all formed elements in the blood
Clinical Definition: percentage of only erythrocytes (red blood cells)
Name the three formed elements of the blood, and compare their relative abundance.
Erythrocytes
- transport oxygen and carbon dioxide
- 120 days
Leukocytes
- initiates immune response
- varies from 12 hours to years
Platelets
- 8 to 10 days
Define colloid osmotic pressure.
Definition
- Osmotic pressure exerted by plasma proteins
Functions
- prevents loss of fluid from blood as it moves through capillaries
- helps maintain blood volume and blood pressure
Identify the various types of plasma proteins, and explain the general function of each.
Albumins
- smallest and most abundant
- exert greatest colloid osmotic pressure by making less water
- act as a transport protein for some lipids, hormones, and ions
Globulins
- alpha globulins and beta globulins transport some water-insoluble molecules, hormones, metals, ions
- gamma globulins act as part of the body’s defenses
Fibrinogen
- contributes to blood clot formation
Regulatory proteins
- includes enzymes and hormones
List dissolved substances in plasma by category.
Organic and Inorganic molecules, and Ions
- Include electrolytes, nutrients, gases, waste products
- Polar or charged substances dissolving easily
- Nonpolar molecules requiring transporter protein
Define hemopoiesis, and explain the role of colony-stimulating factors.
Definition
- Continual production of formed elements
- Occurs in red bone marrow of certain bones
Colony-stimulating factors
- Leukopoietic growth factors (except erythropoietin)
Multi-colony-stimulating factor (multi-CSF)
• increases formation of erythrocytes, all granulocytes • increases formation of all monocytes, platelets - Granulocyte-macrophage colony-stimulating factor (GM-CSF)
• accelerates formation of all granulocytes and monocytes - Granulocytes colony-stimulating factor (G-CSF)
• stimulates formation of granulocytes - Macrophage colony-stimulating factor (M-CSF)
• stimulates production of monocytes
Colony-stimulating factors (continued)
- Thrombopoietin
• stimulates production of platelets (thrombocytes)
- Erythropoietin (EPO)
• hormone produced primarily by kidneys (small amount by liver) • Stimulates erythropoiesis
Describe the four cellular stages of erythropoiesis.
The process of erythropoiesis begins with a myeloid stem cell, which under the influence of multi-CSF forms a progenitor cell.
The progenitor cell forms a proerythroblast, which is a large, nucleated cell.
It then becomes an erythroblast, which is a slightly smaller cell that is producing hemoglobin in its cytosol.
The next stage, called a normoblast, is a still smaller cell with more hemoglobin in the cytosol; its nucleus has been ejected. A cell called a reticulocyte eventually is formed.
The reticulocyte has lost all organelles except some ribosomes, so it can continue to produce hemoglobin (through protein synthesis).
The transformation from myeloid stem cell to reticulocyte takes about 5 days
Compare the production of granulocytes, monocytes, and lymphocytes in leukopoiesis.
Granulocytes
• neutrophils, basophils, eosinophils
- Monocytes
• Monocytes in circulation
• Some become macrophages in tissues - Lymphocytes
• B lymphocytes (B cells)
• T lymphocytes (T cells)
Summarize the process by which platelets are formed in thrombopoiesis.
Megakaryoblast produced from myeloid stem cell
- Forms megakaryocyte under influence of thrombopoietin
• large size and multilobed nucleus
• produces thousands of platelets per second
• Platelets circulate in blood vessels and play a role in clotting
Describe the structure of erythrocytes.
Small, flexible formed elements
- Commonly referred to as red blood cells
- Lack nucleus and cellular organelles
- Have biconcave disc structure (like inverted Frisbies)
- Plasma membrane with enclosed hemoglobin molecules (about 33% of volume)
List the events by which erythrocyte production is stimulated.
Controlled by hormone, erythropoietin (EPO)
• produced primarily in the kidney
• liver small producer
- EPO stimulation
• Testosterone in males stimulates (higher hemocrit)
• decreased blood O2 or increased O2 demand (altitude, exercise, blood loss, etc.)
• detected by chemoreceptors in kidney
• EPO released and travels to red bone marrow
• stimulates myeloid cells to increase erythrocyte production
Explain the process by which erythrocyte components are recycled.
Fe2+ component in hemoglobin
• transported to liver by blood protein: transferrin
• bound to storage proteins: ferritin, hemosiderin
• stored mainly in the liver and spleen
• Fe2+ transported to red bone marrow as needed for erythrocyte production Heme group (minus Fe2+)
• converted within macrophages into green pigment, biliverdin
• eventually converted into yellowish pigment, bilirubin
- Transported by albumin to liver
- Bilirubin is secreted as a component of bile into the small intestine
Compare and contrast the different blood types and their importance when transfusing blood.
Type A
- surface antigen A
- anti- B antibodies
Type B
- surface antigen b
- anti-A antibodies
Type AB
- surface antigens A and B
- neither antibodies
Type O
- neither surface antigen A nor B
- both antibodies
- if antigens that the body is not used to are introduced from a blood transfusion, the body will use antibodies to attack it
Explain the main function of leukocytes.
• Help defend body against pathogens
- Cell-to-cell attack (cell-mediated immunity) or produce antibodies (antibody-mediated immunity)
Distinguish between granulocytes and agranulocytes, and compare and contrast the various types.
granulocytes with visible granules seen with a light microscope
• agranulocytes with smaller granules not visible with light
microscope
- Granulocytes
• neutrophils, eosinophils, basophils - Agranulocytes
• Lymphocytes (T, B, NK), monocyte
Explain what is meant by a differential count and how it is clinically useful.
Performed when leukocytes elevated to diagnose disease
• Measures amount of each type of leukocyte
Explain the structure and function of platelets.
- Membrane-enclosed cellular fragments without a nucleus
- Formed by megakaryocytes pinching off part of the cytoplasm
- Serve an important role in blood clotting
- Normally 150,000 to 400,000 per cubic millimeter blood
- Circulate for 8 to 10 days -30% stored in spleen
Describe vascular spasm, the first phase of hemostasis.
- Sudden constriction of blood vessels
- Reduces blood loss from a broken vessel
- Lasts from few to many minutes
- Greater vasoconstriction with greater vessel damage
- Caused by serotonin and thromboxane A2 from platelets and chemicals from damaged tissues
Name conditions that bring about vascular spasm.
Blood vessel injury
Describe what happens when platelets encounter damage in a blood vessel.
Platelet plug
Formed from platelets arriving at the injury site
Endothelial wall is normally smooth and coated with prostacyclin
Damage vessel - collagen fibers in vessel wall exposed
platelets stick assisted by von Willebrand factor, plasma proteins start clogging up break
Compare and contrast the intrinsic pathway and the extrinsic pathway for activating blood clotting.
Initiation of the coagulation cascade
Two separate pathways initiate blood clotting
intrinsic and extrinsic pathways
Converge to the common pathway
Common pathway begins with Factor X
Intrinsic pathway
- initiated by damage to inside of vessel wall
- initiated by platelets contacting collagen
- takes 3 to 6 minutes
Extrinsic pathway
- initiated by damage outside of vessel
- usually takes about 15 seconds
Describe events in the common pathway.
the extrinsic or intrinsic pathway
Factor X is the first step
- Involves activation of thrombin and fibrin
Positive feedback regulation
- events continuing until clot is formed
- Size of clot limited
- Clotting ends as clotting agents run out
Discuss the survival response that occurs when blood loss exceeds 10%.
- sympathetic nervous system increases vasoconstriction, heart rate, the force of heart contraction
- blood redistributed to the heart and brain
- effective in maintaining blood pressure until 40% of blood is lost
Explain the processes of clot retraction and fibrinolysis.
Clot retraction
- occurs as clot is forming actinomyosin, contractile protein within platelets
- contracts and squeezes the serum out of developing a clot
makes clot smaller - Speeds healing process as damaged tissues are pulled closer together
Fibrinolysis
- LAST STEP IN CLOTTING
- degradation of fibrin strands by plasmin
- begins within 2 days after clot formation
- occurs slowly over a number of days as wound is repaired
Describe when and how blood is formed in the embryo, fetus, childhood, and adulthood.
Hemocytoblasts develop from primitive stem cells
Originate in yolk sac of embryo
colonize liver, spleen, thymus
later begin to colonize red bone marrow
by birth, all production in bone marrow
Hemopoiesis
- occurs in most bones in young children
- restricted to selected bones in axial skeleton in adulthood
- Heads of femur and humerus, flat bones of hip and head
List some conditions that occur with the bone marrow and blood in the elderly.
Older bone marrow replaced with fat as individuals age
older individuals are more likely to become anemic
may produce fewer and less active leukocytes
has more prevalent leukemias of certain types
