Blood Flashcards
Blood
Composition
- Cells
- Erythrocytes (RBC) - most abundant
- Leukocytes (WBC) - most diverse
- Thrombocytes (platelets)
- All cells derived from a pluripotent hematopoietic stem cell in the bone marrow via hematopoiesis
- Cells suspended in a liquid extracellular matrix = plasma
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/815/693/a_image_thumb.jpg?1509413975)
Leukocyte
Cell Distribution
- Neutrophils most abundant WBC in adults
- Lymphocytes most abundant WBC in children
- -cytosis or -philia = too many cells
- -penia = too few cells
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/815/897/a_image_thumb.jpg?1509414295)
Causes of leukocytosis
- Neutrophilia - bacterial infection
- Lymphocytosis - infectious mononucleosis, chronic lymphocytic leukemia
- Eosinophila - parasitic infections, asthma, allergic reactions
- Monocytosis - tuberculosis, malaria, monocytic leukemia
Causes of Leukopenia
- Lymphocytopenia: aids
- Thrombocytopenia: drug toxicity
- Erythropenia: some anemias
- Pancytopenia: chemotherapy, radiation therapy, bone marrow failure
Hematocrit
The percentage of blood volume occupied by packed RBC’s after centrifugation under standard conditions.
RBC’s heaviest so settles to the bottom.
Factors Affecting Hematocrit
-
Sex
- F < M
-
Age
- Children < Adult < Infant
-
Exercise
- Increases with regular exercise
-
Altitude
- More RBC’s because air is thinner
-
Pregnancy
- Retained water in later stages of pregnancy = lower hematocrit
Polycythemia Vera
- Increased RBC’s
- Hematocrit up to 70-80%
- Blood is too viscous
- Treated with therapeutic phlebotomy
Buffy Coat
Thin layer containing leukocytes and platelets that lies just above the RBCs after centrifugation.
~ 1% of blood volume
Plasma
vs
Serum
Plasma = the liquid phase of unclotted blood
Serum = the liquid phase that remains after blood is allowed to clot
Serum = plasma minus clotting factors
Blood
Functions
- Transport
- Blood gases (O2 and CO2)
- Absorbed nutriends
- Metabolic wastes
- Hormones
- Protective functions
- Platelets to repair damaged vessels and mediate coagulation
- WBCs, antibodies, complement proteins, interleukins, etc for immune & inflammatory reactions
- Regulation of body temperature by distribution of heat
- Regulation of ion balance & acid-base balance
Romanovsky Stains
Mixtures of dyes used to stain blood smears.
- Methylene blue: stains nuclei, ribosomes, and basophil specific granules purple
- Azure dyes: stains aurophilic granules (lysosomes) of leukocytes reddish purple
- Eosin: stains RBCs salmon pink & specific granules of eosinophils red
Erythrocytes
Structure & Function
- Transports respiratory gases (O2 and CO2) bound to seperate parts of the hemoglobin molecule
- Biconcave disc = increased surface area to volume
- No nucleus or cytoplasmic organelles
Erythrocyte
Lifecycle
- Released into the blood as immature reticulocytes
- Anucleate but still contains a few residual polysomes
- Special stains causes polysomes to clump forming a dark-staining reticulum visible by LM
- Increased # indicates increased rate of RBC production
- Mature RBCs nonmotile & flexible
- When RBC loses flexibility they are destroyed
- Mainly in the spleen but also in bone marrow and liver
- Average lifespan = 120 days
Poikilocytosis
Abnormally shaped RBC.
Causes:
- Defects in the spectrin cytoskeleton or its anchoring to the plasma membrane
- Hereditary spherocytosis
- Hereditary elliptocytosis
- Defects in hemoglobin
- Sickle Cell Anemia
- HbS polymerizes into long rods under low oxygen tension
- Deforms the RBC which blocks capillaries
- Sickle Cell Anemia
Anisocytosis
Abnormalities in erythrocyte size.
- Macrocytes: abnormally large
- Vit B12 or folate deficiency
- Microcytes: abnormally small
- Iron deficiency
Hemoglobin Content
Abnormalities
- Hyperchromic = contains more Hb than normal
- Very rare
- Hypochromic = contains less Hb than normal
- Seen in some anemias
Anemia
A decrease in the oxygen carrying capacity of the blood.
Platelet
Functions
Limit bleeding after injury to a blood vessel.
Promote vessel repair.
Required for maintenance of an intact endothelium.
Thrombocytopenia
- Abnormally low platelet count
- < 150,000/microliter
- Characterized by:
- Easy bruising
- Nose bleeds
- Petechial rash
- Spontaneous bleeding
Idiopathic Thrombocytopenic Purpura
(ITP)
Autoimmune disease where anti-platelet antibodies destroy platelets.
Platelet
Lifecycle
- Derived from bone marrow cells called megakaryocytes
- Lifespan ~ 8-10 days
- Removed by sleen or via clotting process
Platelet
Morphology
Hyalomere
- Clear outer region
- Contains a bundle of microtubules
- Helps maintain discoid shape
- Contains actin & myosin
- Involved in shape change of activated platelets
Granulomere
- Central region with basophilic stippling
- Contains usual cytoplasmic organelles
- Contains at least 3 types of granules
- Alpha, Delta, and Lambda
2 systems of membrane bound channels:
-
Open canalicular system
- Invaginations of the plasma membrane
- Facilitates rapid exocytosis of granules
-
Dense tubular system
- Stores Ca2+ needed for exocytosis
- Not continuous with the plasma membrane
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/818/878/a_image_thumb.png?1509416922)
Platelet Granules
-
Alpha granules (α) :
- Platelet-derived growth factor (PDGF) : mitogen for vessel repair
- von Willebrand Factor (vWF) : mediates platelet adhesion to endothelium (collagen and laminin)
-
Delta granules (δ):
- Ca2+, ATP, ADP: all enhance platelet aggregation
-
Serotonin: vasoconstriction
- Picked up by platelets in circulation
-
Lambda granules (λ):
- Lysosomal enzymes: clot resorption
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/819/502/a_image_thumb.jpg?1512938245)
Vessel Repair Process
Adhesion
- vWF binds to components of the damaged basement membrane (collagen, laminin)
- vWF can be secreted by many cells including platelets
- vWF attracts platelets which have surface receptor for vWF causing a single layer to form
Aggregation
- Platelets secrete fibrinogen
- Other platelets attracted to the site via cell surface receptors for fibrinogen
- Forms a multilayered primary hemostatic plug which fills the defect in the vessel wall
- Fibrinogen links the platelets together
Activation
- Results in:
- Secretion of mediators stored in granules
- Synthesis and release of new mediators derived from membrane lipids (aracidonic acid)
- Thromboxane A2 (TXA2)
- Change of platelet shape
- Released mediators cause:
- Further platelet aggregation
- TXA2, serotonin, and Ca2+
- Vasoconstriction (limits bleeding)
- Serotonin and TXA2
- Blood coagulation
- Platelets release several coagulating factors from alpha granules
- Meshwork of fibrin formed which stabilizes the platelet plug forming the secondary hemostatic plug
- Further platelet aggregation
Clot Retraction
- After ~ 1 hr platelets contract due to actin-myosin interaction
- Platelet plug decreases in size & flattens against vessel wall
- Helps to re-establish smooth blood flow
Clot Resorption
- Mediated partially by lysosomal enzymes from λ-granules
Vessel Repair
- Mediated by platelet-derived growth factor (PDGF) from alpha granules
- PDGF is strongly mitogenic for cells needed to rebuild the vessel wall including:
- Endothelial cells
- Fibroblasts
- Smooth muscle
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/819/903/a_image_thumb.jpg?1509418936)
Platelet Activation
Regulation
- Platelets activated upon binding to collagen and laminin of damaged basement membrane
- These are not exposed in healthy vessels
- Healthy endothelial cells produce factors that inhibit platelet aggregation
- Ex. Prostacyclin (PGI2) from arachidonic acid
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/822/232/a_image_thumb.jpg?1509419741)
Aspirin
Inhibits cyclooxygenase activity.
- Decreases platelet function
- Prolongs bleeding times
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/822/557/a_image_thumb.jpg?1509419832)
Von Willebrand’s
Disease
- Most common bleeding disorder
- Caused by deficiency of von Willebrand’s factor
- Results in abnormal platelet adhesion
Bernard-Soulier
Syndrome
- Due to deficiency of platelet receptor for von Willebrand’s factor
- Results in abnormal platelet adhesion
Glanzmann’s Thrombasthenia
- Due to deficiency of platelet receptor for fibrinogen
- Results in decreased of platelet aggregation
Granulocytes
Neutrophils, eosinophils, and basophils.
Characterized by:
- Abundant cytoplasmic granules of 2 types:
-
Azurophilic granules (primary)
- small specialized lysosomes
-
Specific granules (secondary)
- non-lysosomal secretory granules
-
Azurophilic granules (primary)
- Lobulated heterochromatic nucleus
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/822/756/a_image_thumb.jpg?1509420522)
Agranulocytes
Lymphocytes and Monocytes
Characterized by:
- Few azurophilic granules
- No specific granules
- Non-lobulated nucleus
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/823/076/a_image_thumb.jpg?1509420506)
Diapedesis
- Process by which leukocytes leave the blood vessels by passing between endothelial cells
- Requires specific interactions between molecules on plasma membrane of leukocyte and endothelium
- Rate increases with inflammation
- Due to histamine and chemoattractant molecules
- Occurs most frequently in postcapillary venules
-
Tethering (weak adhesion) to the endothelium
- Mediated by L-selectins
- Located on leukocytes
- Receptors on endothelium
- Mediated by L-selectins
-
Rolling along the endothelium as weak interactions break and form again
- Mediated by
- Integrins on leukocytes and their receptors on endothelium
- P-selectins and E-selectins on inflamed endothelial cells and their receptors on leukocytes
- Mediated by
- Arrest as stronger interactions form
- Diapedesis
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/823/136/a_image_thumb.png?1509421304)
Leukocyte Adhesion Deficiencies
LAD 1: lack of integrin expression of leukocytes.
LAD 2: lack of leukocyte receptors for P & E selectins.
Both result in:
decreased diapedesis
leukocytosis
recurrent infections
Chemotaxis
- Migration along a concentration gradient of chemotactic factors
- Positive = migration towards a greater concentration
- Common
- Negative = migration towards a lower concentration
- Rare
- Positive = migration towards a greater concentration
- After diapedesis leukocytes are guided to specific locations via chemotactic factors
- WBCs can respond because they are motile