Blood (p1) Flashcards
What are distribution (transport) functions of the blood?
a) oxygen and nutrients - dleivery of O2 to tissues or nutrients
b) metabolic wastes - conveying metabolic wastes to the liver or lungs (CO2 as a waste product)
c) hormones - many are transported through the blood
What are blood components? Cellular and physical components?
Blood - Only FLUID tissue in the body (formed elements are suspended in plasma)
Cellular;
- erthrocytes (RBCs) -> transportation of oxygen
- leucocytes (WBCs) -> protection against microorganisms
- platelets -> for forming blood clots
Physical;
- O2 rich colour is scarlet, O2 poor colour is dark red
- more dense, viscous than water
- pH = 7.35-7.45, this is monitored al the time and if pH is not within this range, there are mechanisms that kick in to bring it back (acidosis vs alkalosis)
- ~8% of our body weight (lower in females than in males)
What are regulation functions of the blood?
a) body temperature (circulatory system) - distribution, onservation, dissipation
- core body (brain, visceral organs) temp = most important
- blood flow is controlled through the body
- blood can also carry heart -> the ridding of extra heat
b) pH in body tisses (plasma proteins, bicarbonate reserve)
- can soak up extra H+ ions so the blood doesn’t become too acidic
- CO2 + H2O <-> H2CO3 <-> HCO3- + H+
c) adequate fluid volume - enough fluid volume for good blood pressure
What are protection functions of the blood?
a) platelets, plasma proteins - protection against blood loss (formation of blood clots)
b) antibodies, complement, WBCs - protection against infection (components of the immune system)
what consists blood plasma?
- 90% water + many solutes
- plasma proteins
- albumin
what are plasma proteins?
functional proteins which remain in blood
- produced in the liver
what is albumin?
carrier of various molecules (ex. steroids), an important blood buffer and a major osmotic protein
- 60% of all plasma proteins
- blood buffer -> can soak up extra H+ ions to prevent acidic blood
- holds a bunch of water to maintain adequate blood pressure
What is the major osmotic ion?
Na+, sodium = most prevalent ion in bloodstream
- responsible for making sure there are enough fluids in the body
- monitors blood osmolarity (acidity)
If you were to spin a blood sample in a centrifuge, what would be the result of the different layers?
Plasma = top layer
- least dense component
- fluid compartment
- ~55% of whole blood
Buffy coat = middle layer
- leukocytes and platelets
- <1% of whole blood
Erthrocytes = bottom layer
- RBCs
- ~45% of whole blood (hematocrit)
- most dense component
Formed elements = erthrocytes and buffy coat (leukocytes and platelets)
Why do we say that leukocytes only are complete cells?
Leukocytes have nuclei whereas RBCs once they are in the blood no longer have a nuclei
Platelets also dont have a nuclei, only have vesicles for clotting
Most formed elements are short-lived/disposable and are constantly replaced by bone marrow, this is why we call them formed elements rather than cells
What is the function of the spectrin protein?
Responsible for allowing RBCs to slightly change their change, found in the plasma membrane
What is the functional anatomy of an erthrocyte?
Biconcave discs (no nucleus) = “bags of hemoglobin”
- other proteins maintain PM and regulate cell shape (spectrin)
- RBC transport O2 from lungs to tissues, transports ~20% of CO2 back to lungs
- depression in the centre to indicate where the nucleus was before it was ejected
What are some specialized characteristics of erthrocytes that optimize function?
1) Small size and biconcave shape gives a large SA to V ratio
2) >97% non-water composition is hemoglobin
3) No mitochondria, generates ATP anaerobically ∴ they dont use any of the O2 they transport
- RBCs are the major factor contribution to blood viscosity, rate of blood flow is inversely affectd by RBC count
- if RBCs increase, blood flow decreases (slower because its much thicker)
What is hemoglobin?
Hemoglobin (Hb) = protein globin bound to red heme pigment
What is globin?
globin = 4 polypeptide chains (2 α and 2 β)
- 4 Fe-containing central heme groups
- each Fe can reversibly bind to one molecule of oxygen
Why is Hb contained in erthrocytes rather than being a plasma protein?
- keeps it from fragmenting and being lost
- keeps it from contributing directly to osmotic pressure and blood viscosity
What do O2 and CO2 combine with in regard to a Hb?
O2 combines with heme group
CO2 combines with globin part
This causes formation of carbaminohemoglobin
Differences in where O2 and CO2 combine allows for no competition but they do still influence each other
What is the process of erthropoiesis?
Specifically the production of RBCs
The hematopoietic stem cells turns into a commited cell as a proerthroblast, once it has become a commited cell, it can only make the intended pathway
- proethrocytes = can only form erthrocytes
What is hematopoiesis?
Production of formed elements, in general occurs in red bone marrow
What is a hemoatopoietic stem cell?
AKA a hemocytoblast = starting gpoint for production of RBCs, all WBCs and platelets
What is the difference between a reticulocyte and an erthrocyte?
reticulocyte = residual protein synthetic material
erthrocyte = once a reticulocyte is gone - released into the blood, it becomes an erthrocyte
What can a reticulocyte count tell you?
- provides info on the bone marrows ability to produce new RBCs
- helps distinguish between various causes of anemia
- helps monitor bone marrow response and the return of normal marrow function following chemotherapy or other treatments
Describe the regulation of erthropoiesis
A balance between RBC production and destruction
- too few = anemia
- too many = polycythemia (blood is more viscous and harder to circulate)
- production rate >2 million/sec if healthy with sufficient iron and B vitamines
What is the importance of B vitamins?
Important in nucleic acid production for new cells
What is erthropoietin?
EPO = glycoprotein hormone produced primarily by the kidney, liver production is a secondary source
- always some EPO in blood, additional release if hypoxia
- enhanced maturation rate of RBC precursors
When would there be an additional release of EPO in the blood?
If hypoxia due to hemorrhage/excess RBC destruction, high altitude of pneumonia, increased demand
- hypoxia = low oxygen delivery sensed at the level of the kidneys
- high altitude = oxygen is limiting in the environment
- pneumonia = not enough oxygen from lungs
- the body will try to make up for a loss/insufficient levels by increasing production of RBCs
What is monitored and acts as a signal, the number of RBCs or the level of oxygen transport?
Cannot measure [RBC], so levels of O2 is monitored and reacted to
what is the effect of testosterone on renal EPO production? what is the second reason why women have a lower hematocrit than men?
EPO is stimulatory, so males that have high circluation levels of testosterone compared to feamles tend to have increased levels of hematocrit
Women during reproductive years (puberty -> menopause) lose blood every month through menstruation ∴ need to make up for the blood loss allowing them to have a lower hematocrit than men
What is the fate/destruction of erthrocytes?
Mature erthrocytes become rigid, fragile with time and Hb begins to degenerate
- usual lifespan = 100-120 days
- spleen = “RBC graveyard”
- iron is stored and reused; rest of heme degraded to bilirubin which eventually becomes stercobilin or urobilinogen
- amino acids of globin part recycled
bilirubin = moved into bile to be removed through feces
stercobilin = removed via feces
urobilinogen = slightly more water soluble, moved out through urine rather than feces
What is anemia?
Reduced oxygen carrying capacity of blood bc;
- not enough normal RBCs produced
- episode of significant blood loss
- RBCs are being too quicly destroyed (sickle cell anemia)
Why does sickle cell anemia have a reduced oxygen delivery?
Can get stuck a lot easier leading to reduced oxygen delivery compared to a normal RBC
- stuck easier because of changed crescent shape rather than a round circular shape
What are the different types of polycythemia?
Polycythemia = elevated # of RBCs
1) Polycythemia vera = real polycythemia due to cancer cells
2) secondary polycythemia = higher altitude leading to limiting oxygen, can also be due to respiration issues
3) artifical polycythemia = taking EPO and articially boosting RBCs in circulatory system
What are platelets?
- cytoplasmic fragments of megakaryocytes
- contains purple staining granules that contain clotting factorrs and enzymes
- anucleate; lifespan is only ~10 days
- platelet formation regulated by the hormone thrombopoietin (mainly the liver, secondarily the kidney)
A single megakaryocyte can make many platelets
What are the 3 phases of hemostasis?
1) vascular spasms
2) formation of a platelet plug
3) coagulation
What are vascular spasms?
Brief vasoconstriction of vessel in response to damage
- triggers are damage to the wall of the vessel, chemicals from damaged endothelial cells and activated platelets, reflexes activated by local pain receptors
What is the purpose of vascular spasms?
Slowing of blood flow so its easier for platelets to start to group together to trap RBCs to form a platelet plug, then convert that plug to a more solid blood clot
Describe the formation of a platelet plug
- Usually platelets do not stick to each other or to endothelial linings due to production of NO (nitric oxide) and PGI2 (prostacyclin) by endothelial cells
- exposure to collagen in structure of basement membrane stimulated platelets to swell, becoming spiky and sticky to then adhere to exposed collagen via von Willebrand factor to then degranulate ad cause a lot of positive feedback
Degranulation = the release of clotting factors present in platelets
Why is it important that platelets do not usually stick to each other and only when a blood clot is formed/needed?
if a blood clot is made where there is no damage, this will halt any further blood flow
What are platelet products that promote clumping?
- ADP - enhances aggregation and degranulation
- Serotonin - a NT but also a platelet product
- Thromboxane A2 (prostaglandin) - enhances vascular spasm and aggregation
What is the product in phase 3 of the two pathways that converge on prothrombin activator?
Thrombin forms firbinogen (soluble) that can then form fibrin (insoluble polymer) to then create a cross-linked fibrin mesh
Fibrin = threads for blood clot linking
What is coagulation?
- When the platelet plug is converted to a much sturdier structure
- 3 phases; prothrombin activator formed, prothrombin converted to thrombin, fibrinogen molecules become fibrin mesh
- thrombin = enzymes catalyzing reaction of fibrinogen to fibrin
- many procoagulants and anticoagulants, the latter predominate in an intact vessel
What are the 2 pathways to prothrombin activator (PA) and coagulation?
1) intrinsic pathway - clotting of blood outside body (in a tube) or in a slightly damaged vessel
- slower pathway to factor X and PA, but longer capacity
- exposure to collagen is key
2) Extrinsic pathway - cloting of blood in response to damage -> release of tissue factor -> bypass many steps of intrinsic pathway
- faster pathway to factor X and PA but shorter capacity
What charges do collagen, activated platelets and glass tubes all have associated with them?
Negative charges
Describe clot retraction and repair
- Platelets contract (containing actin and myosin) exerting pull on surrounding fibrin strands
- Serum squeezed from clot and ruptured edge of blood vessels pulled closer
- PDGF (platelet-derived growth factor) released during degranulation stimulates smooth muscle cells and fibroblasts to divide and rebuild wall
- endothelial cells multiply to fill gap in lining (VEGF = vascular endothelial growth factor) and the clot covers the area of damage while healing begins
Serum = plasma without the clotting factors (all clotting factors have been used up)
