Chapter 17 Flashcards
(19 cards)
List of the components and functions of whole blood
- Plasma: 90% of water, proteins (8% of plasma weight) include albumin and globulin (alpha, beta, gamma).
- Albumin is the main contributor to osmotic pressure, made in the liver.
- Alpha and beta Globulins are transport proteins that binds to lipids, metal ions, and fat-soluble vitamins, are made in the liver.
- Gamma Globulins release antibodies during immune response.
Formed elements:
- Erythrocytes are the red blood cells that transports oxygen and constitutes for 45% of a blood sample, a percentage known as the hematocrit
- leukocytes are the white blood cells and platelets that act in various ways to protect the body and platelets are cell fragments that help stop bleeding, constitutes 1% of a blood sample
- platelets are cell fragments that help stop bleeding
Relate the structure of erythrocytes (RBC) to its functions
- have no nuclei or organelles
- have structural proteins on the surface to change shape of the RBC
- disc shape is ideally suited for gas exchange because no point within the cytoplasm is far from the surface
- an erythrocyte is over 97% hemoglobin, a molecule that binds to and is responsible for transporting respiratory gases
- because they lack mitochondria and generate atp by anaerobic mechanism, they do not consume any of the o2 they carry. Making them very efficient o2 transporters
RBC is made up of Hemoglobin: is the protein that makes red blood cells red, heme is red pigment that is bound to the protein globin. A hemoglobin molecule can bind to four molecules of o2.
Describe the life cycle of the erythrocyte: production of Erythrocyte
- hematopoiesis occurs in the red bone marrow which is found in the axial skeleton, girdles, and proximal epiphysis of humerus and femur
- different types of blood cells all arise from hematopoietic stem cell or hemocytoblast cells which reside in the red bone marrow, these stem cells give rise to all formed elements, hormones and growth factors push cell towards specific pathway of blood cell development, committed cells cannot change, these new blood cells then enter blood sinusoids
- erythrocyte production (erythropoiesis) begins when hemocytoblast undergoes a series of changes until it becomes a reticulocyte (a young erythrocyte) on day 15. These reticulocytes, still contain a network of clumped ribosomes, filled almost to bursting with hemoglobin. Within 2 days of release as their ribosomes are degraded by intracellular enzymes, they mature into erythrocytes
Describe the lifecycle of the erythrocyte: homeostatic Erythropoiesis
- regulated by a glycoproteins hormone called Erythropoietin (EPO) and dietary requirements
- EPO stimulates the production of erythrocytes, kidneys produce EPO
- adequate supplies of iron, aa, vitamin b is essential for maintaining homeostatic RBC number
the drop in normal blood oxygen levels triggers EPO formation can result from:
- reduced numbers of RBC due to hemorrhage (bleeding) or excessive RBC destruction
- insufficient hemoglobin per RBC (iron deficiency)
- reduced availability of oxygen that occurs during high altitude or during pneumonia
Too many erythrocytes or excessive oxygen levels in the bloodstream depresses EPO production, control of EPO production is based on the erythrocytes ability to transport enough oxygen to meet tissue demands.
Raw materials required for erythropoiesis includes nutrients, amino acids, lipids, and carbohydrates are essential for the synthesis of all cells
Vitamin B12 and folic acid are necessary for normal DNA synthesis, in this case development of erythrocytes
Iron is essential for hemoglobin synthesis
Free iron ions are toxic, so it is stored inside of cells as protein iron complexes such as ferritin. In blood iron is transported loosely bound to a transport protein called transferrin, developing erythrocytes take up iron as needed to form hemoglobin
Describe the lifecycle of an erythrocyte: destruction of erythrocytes
- RBC have a lifespan of 100-120 days
- erythrocytes become old, loses flexibility, hemoglobin begins to degenerate.
- they become trapped and fragment in smaller circulatory channels, such as the spleen
- macrophages engulf and destroy dying erythrocytes
State the components, functions and ultimate fate of a hemoglobin molecule
After the dying erythrocytes is engulfed by the macrophage, the heme of their hemoglobin is split off from the globin, meaning it’s core of iron is salvaged bound to protein as ferritin, and stored for later use. The balance of the heme group then is degraded into bilirubin, a yellow pigment that is released into the bloodstream and binds to albumin for transport. liver cells then pick up the bilirubin to make bile where it is degraded into urobilinogen, a degraded pigment that leaves the body in feces and becomes brown in pigment. The protein part of hemoglobin is metabolized or broken down into amino acids which are released to the circulation.
Erythrocyte disorders
Anemia: is a condition in which the blood’s oxygen carrying capacity is too low to support normal metabolism. Can be split into three groups: blood loss, not enough RBC produced, too many RBC destroyed.
Polycythemia: is an abnormal excess of erythrocytes that increases blood viscosity causing it to flow sluggishly. Hemocrit (blood percentage) may be as high as 80% and blood volume may double causing the vascular system to be engorged with blood, severely impairing circulation.
Cure: therapeutic phlebotomy
What are leukocytes and what do they do?
- are the only formed elements that are complete cells with nuclei and usual organelles
- are crucial to the body’s defence mechanism, RBC are confined to the bloodstream, but WBC can slip out of the capillary through a process known as diapedesis to transport to an area in the body they mount inflammatory or immune responses.
- once out of the bloodstream, leukocytes undergo a process called “positive chemotaxis” to follow a chemical trail left by damaged cells or other leukocytes to find area of tissue damage to gather there in large number to destroy foreign substances and dead cells.
- white blood cells are mobilized for action, a rapid increase in WBC production occurs. a WBC count of over 11k cells/uL is called Leukocytosis
List and describe the major types of leukocytes (WBC), and classify them according to their structural characteristics
-two major categories: granulocytes (neutrophils, esinophils, basophils) and agranulocytes (lymphocytes, monocytes)
Granulocytes: contains obvious membrane bound cytoplasmic granules, contains lobed rather than circular nuclei, larger and short-lived compared to RBC, all are phagocytic to some degree
Neutrophils: are most numerous wbc account for 50-70%, their name indicates that their granules take up both basic and acidic dyes. Some of these granules contains hydrolytic enzyme properties or contain a potent brew of antimicrobial proteins called “defensins”. Are very phagocytic, nucleus is multilobed
Eosinophils: account for 2-4% of wbc, nucleus has two lobes connected by a broad band, red staining granules contain digestive enzymes that is released onto parasitic worms, they lack enzymes that specifically digest bacteria, plays a role in allergies and asthma, as well as immune response modulators
Basophils: 0.5 -1% rarest wbc, nucleus is deep purple with one or two constriction, base loving, granules contain histamine which is a chemical that acts as a vasodilator and attracts WBC to inflamed sites, similar to mast cells
Agranulocytes: lack visible cytoplasmic granules, have spherical or kidney shaped nuclei
Lymphocytes: second numberous WBC approx 25%, mostly found in lymphoid tissue, but a few circulate in blood, crucial to immunity. Two types of lymphocyte are T cells which act against virus infected cells and tumour cells ; B cells which give rise to plasma cells and produces antibodies
Monocytes: 3-8% of wbc and are the largest leukocytes, u or kidney shaped nuclei, leave circulation and differentiate into macrophages, crucial against viruses and intracellular parasites, and chronic infections. Activate lymphocytes to mount an immune response
Explain the production and lifespan of leukocytes (leukopoiesis) and how are they numbered
Leukopoiesis is stimulated by chemical messengers (paracrines or hormones)
These chemical messengers are glycoproteins that fall into two families of the hematopoietic factors (interleukins and colony-stimulating factors CSFs)
Hematopoietic factors are released by supporting cells of the bone marrow and mature WBC, which induces division and maturation of the precursors of WBC but also enhances protective potency of mature WBC
Interleukins are numbered e.g IL-3, IL-5
Most CSFs are named for the leukocyte population they stimulate e.g granulocyte production are stimulated by G-CSFs or granulocyte-CSFs
Describe the two leukocyte disorders
Leukopenia: abnormally low white blood cell count, can be drug induced (particularly by anti cancer drugs or glucocorticoids)
Leukemias: abnormal excessive production of white blood cell count, immature and non functional WBC flood the bloodstream) cancerous cells fill red bone marrow, crowding out other cell lines (leads to anemia or internal bleeding)
What are platelets and how do they help stop bleeding?
Platelets are fragments of large cells called megakaryocytes
Platelets have granules that contain chemicals involved in the clotting process e.g serotonin, calcium ions, enzymes, ADP, platelet derived growth factor (PDGF)
It helps stops bleeding by forming temporary platelet plug that help seal breaks in blood vessels by sticking to damage site
Describe the three phases of homeostasis to prevent blood loss
When blood vessel wall breaks, homeostasis is induced to stop the bleeding.
Homeostasis occurs in three stages:
- Vascular spasm: vasoconstriction occurs in damaged blood vessel where smooth muscle contracts causing vasoconstriction. This occurs to prevent excessive blood loss for 20-30 mins to allow platelet plug formation to occur
- Platelet plug formation: injury to endothelium lining blood vessel exposes underlying collagen fibres that enable platelets to adhere, platelets then release chemicals that make nearby platelets sticky, they also release chemical messengers called adenosine diphosphate (ADP), serotonin, and thromboxane A
ADP: a potent aggregating agent that enables platelets to stick to the area and release their contents
Serotonin and thromboxane A: messengers that enhance vascular spasm and platelet aggregation
- Coagulation: reinforces the platelet plug with fibrin threads that act as molecular glue for the formed platelets, resulting in blood clot.
Blood clots are effective in sealing larger blood vessel damages.
Blood is then transformed from liquid to gel, this process involves a series of substances called clotting factors or procoagulants.
Describe how homeostasis occurs after blood loss is prevented
A platelet induced process called clot retraction occurs to further stabilize the clot and then to be removed when damage has been repaired. This process occurs through: clot retraction, fibrinolysis, inhibition of clotting
Clot retraction: actin and myosin in platelets contract within 30-60 mins, causing surrounding fibrin strands to squeeze serum (plasma and not clotting protein) from the mass, which draws ruptured blood vessel edges together. Platelet derived growth factor is released by platelets to stimulate division of smooth muscle cells and fibroblasts to rebuild blood vessel wall.
Fibrinolysis: is the process where clots are removed after repair is completed, begins within 2 days and continues for several of days until clot is dissolved, the activation of plasminogen produces a fibrin digesting enzyme known as plasmin to bust the clots
Inhibition of clotting: occurs to prevent clots from becoming unnecessarily large. Swift removal of clot factors and inhibition of activated clotting factors. Heparin is a natural anticoagulant, it inhibits thrombin and the intrinsic pathway.
Differentiate between intrinsic and extrinsic pathways of blood coagulation and the final common pathway of blood coagulation
Coagulation occurs in three phases:
- prothrombin activator formed by intrinsic and extrinsic pathways, involves a series of procoagulants, each pathway leads towards the activation of factor x, factor x then complexes with calcium ions and platelet factor 3 and factor v to form prothrombin activator,
- Prothrombin activator catalyzes plasma protein called prothrombin into enzyme thrombin,
- thrombin catalyzes the soluble clotting factor fibrinogen to insoluble fibrin. Which is the molecular glue that holds the platelets together, fibrin makes the plasma liquid become gel-like
- Intrinsic pathway is needed for clotting within the blood, triggered by activated platelets, occurs more slowly.
- Extrinsic pathway is needed because tissue factor occurs outside of blood, triggered by blood being exposed to a factor (tissue factor) found on cells in tissues surrounding the blood vessel, this process occurs more faster
Describe the thromboembolic disorders
Thrombus: a clot that develops and persists in an unbroken blood vessel, if it is large enough it can block circulation of cells.
Embolus: when thrombus is able to break away from the vessel wall and floats freely in the bloodstream, it’s not a problem until it reaches a blood vessel that is too narrow to pass through, it then becomes an embolism
Thrombocytopenia: low number of circulating platelets, can arise from any condition that suppresses or destroys the red bone marrow
Hemophilia: includes several similar hereditary bleeding disorders. Deficiency in clotting factors e.g VIII, IX, XI
Hemophilia A: most common type due to factor VIII deficiency
Describe the procedures for determining blood groups
The usual blood bank procedure involves collecting blood from a donor and mixing it with an anticoagulant that prevents clotting by binding calcium ions.
The shelf life of collected blood is 35 days.
Blood is often separated into its component parts so that each component can be used when and where it is needed.
What are the causes of transfusion reactions
Transfusion reactions happen when mismatched blood is transfused. The recipients agglutinogens (plasma antibodies) clump the foreign RBCs.
The clumped RBCs may block blood vessels temporarily and then are lysed.
Released hemoglobin may cause kidney shut down.
Explain the cause of erythroblastosis fetalis
If a pregnant woman has RH- blood and her first child had RH+ blood, during birth the mother will form RH+ antigens in her blood stream (when bleeding occurs as placenta detaches from the uterus and RH+ antigens get into her bloodstream) and she needs to be treated before her next pregnancy with RhoGAM - A serum containing anti-Rh antibodies.
If her condition is not treated when she becomes pregnant again with another Rh+ baby her antibodies will cross through the placenta and destroy the babies RBCs.
