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)