CARDIAC UNIT: CONSTITUENTS OF BLOOD Flashcards
What is the average blood volume?
5 litres
Name the major constituents of blood and give their approximate % of total blood volume
major constituents:
Plasma/serum: ~60% of blood
RBC (erhtrocytes): ~40%
WBC (leukocytes): <5%
Platelets: <1%
Describe what composes plasma and give the approximate concentrations of the major plasma constituents
- Water - 92% weight per volume
- Electrolytes: sodium, potassium, calcium, magnesium, hydrogen, bicarbonate
- Nutrients: glucose, lipids, cholesterol, vitamins, free fatty acids
- Proteins 7% w/v: albumin, globulin, fibrinogen
- Albumin - osmotic force - helps to retain water in blood vessels and helps to transport hydrophobic molecules (fatty acids)
- Fibrinogen - clotting factor
- Waste: urea, creatine, uric acid, bilirubin
- Gases: carbon dioxide, oxygen, nitrogen
State what a hematocrit measures, normal hematocrit levels, and describe briefly how it works
- Hematocrit: the volume percentage of red blood cells in blood
- 40-45% is standard
- Height of red blood cells divded by total height of blood x100%
- Blood sample is centrifuged which allows RBC’s to become packed at the bottom of a test tube
- Buffy coat: white blood cells and platelets. lies between the packed RBCs and cell free plasma
How many red blood cells, white blood cells, and platelets are in 1 μL ? How many red blood cells do we make per second? Why do we have more platelets than WBCs or RBCs?
- RBC: 5 million / μL
We make 2 million per second - WBC: 7000 / μL
- Platelets: 250 000 / μL
Because they are much smaller
Define hematopoiesis and what is synthesized
- Hematopoiesis – the synthesis of blood cellular components at bone marrow (specifically red bone marrow as you become an adult)
Pluripotent hematopoietic stem cells → uncommitted stem cells → committed progenitor cells → more specialization
- 75% of what is produced is leukocytes
- 25% of what is produced is erythrocytes
State the lifespan of leukocytes and erythrocytes
- Leukocytes: hours to days
- Erythrocytes: 90 to 120 days
What regulates hematopoiesis?
Cytokines!
- Colony stimulating factors regulate leukocytes
- EPO (erythropoeitin) regulate erythrocytes (stimulates RBC formation); Hypoxia induces it
- TPO (thrombopoeitin) regulate platelets
Describe the function of red blood cells
transport oxygen
Describe the structure of red blood cells
Has antigens on surface (example: A, B, Rh)
which have implications in transfusion and rejection
Requires hemoglobin
Describe the synthesis of red blood cells
See figure from lecture. EPO synthesis occurs in the kidney. EPO is transported to bone marrow to increase red blood cell production. Red blood cell production occurs in the bone marrow
Describe the major function of hemoglobin and how this function can be regulated by different physiological factors
- Hemoglobin production requires iron, B12, and folic acid
- Hemoglobin has 4 globin subunits that contain a heme group
- Each heme group contains iron to which oxygen binds
- Hence, hemoglobin can bind 4 oxygen molecules
- Binding is cooperative - the binding of one oxygen molecule facilitates the binding of another
Describe the oxygen dissociation curve of hemoglobin
See picture from lecture.Sigmoidal curve
What is the pressure of oxygen in alveoli of lungs
100 mmhg pO2 in alveoli of lungs (hemoglobin is almost 100% saturated)
Cooperative binding allows for almost 100% saturation
What is the pressure of oxygen in capillaries of active muscle
20 mmHg pO2 in capillaries of active muscle
Hemoglobin doesn’t bind to oxygen very well (important because we want oxygen to be delivered to the tissues)
How does altitude affect the oxygen dissociation curve of hemoglobin?
Right shift in altitude
Where are old blood cells destroyed? What are the byproducts of old blood cells and where do they go?
Old blood cells are destroyed in the spleen and a byproduct is bilirubin and metabolites. Metabolites are excreted in urine. Bilirubin metabolites enter the liver and can be part of bile
What affects hematocrit?
- Sex: lower in women than in men
- Altitude: higher in high altitudes
- Activity levels: higher in athletes
What regulates hematocrit
- Oxygen (via EPO)
- Nutritional status
- Menstruation / hemorrhage
- Hormones
- Vitamin B12 complex
- Folic acid
Define anemia and describe the 4 different types.
Anemia: → insufficient Hb or RBC
- Hypochromic (low Hb in RBCs, Fe deficiency)
- Megaloblastic (pernicious and non-pernicious): a condition in which the bone marrow produces unusually large, structurally abnormal, immature red blood cells
Pernicious: due to lack of B12; insufficient absorption
Non-pernicious: not due to lack of B12 - Hemolytic (fragile RBCs - more prone to lysis)
- Aplastic (low RBC production)
Describe: hyperbilirubinemia, what it causes, and how it is reversed?
Hyperbilirubinemia: condition in which there is a build up of bilirubin in the blood, causing jaundice (yellow discoloration of the eyes and skin)
- Bilirubin also causes the yellow of the liver
- Reversed by urinary excretion
What is the function of platelets? Describe the process
Function: assist with blood clotting → important when wounded
When endothelial cells (that make up the blood vessel walls) are damaged:
Prostacyclin production is reduced, which reduces the solubility of platelets and them allowing them to aggregate at wound site (clotting)
Platelet aggregation causes release of Serotonin (5-HT), ADP, thromboxane A2 factors that help recruit more platelets and vasoconstruction (positive feedback?)
Clotting cascade
Factors 1 - XIII → prothrombin → thrombin → fibrinogen → fibrin
Exposed collagen binds platelets to wound cite
Describe platelet structure
Soluble (due to prostacyclin)
Small
Describe platelet synthesis
puripotent hematopoietic stem cell –> uncommitted stem cells –> committed progenitor cells –> megakaryocyte –> platelets
Inappropriate platelet clotting leads to ?
stroke/heart attack
What are the different classifications of white blood cells?
- Polymorphonuclear (PMNs) granulocytes - lots of different shaped nucleus
- Monocytes
- Lymphocytes
Describe 3 different types of polymorphonuclear (PMNs) granulocytes. What do they do?
Neutrophils:
Make up 50-70% of WBC
Neutralize foreign substances
Eosinophils:
Destroy invading parasites and cells (foreign cells)
Release granular deposits to attack cells
Basophils:
Form Mast cells, which release histamine, mediate allergic response, and mediate inflammation
Describe the function of monocytes
Differentiate into macrophages (big eaters - ingest invaders)
Antigen presentation
List 4 types of lymphocytes
Immune cells
B cells
T cells
Natural killer cells
