Unit 3 - Blood PART D Flashcards
What are the 3 formed elements of blood?
- Erythrocytes (Red Blood Cells)
- Leukocytes (White Blood Cells, WBCs)
- Platelets
Erythrocytes (Red Blood Cells) KEY POINTS
a. Most numerous blood cell. Makes up >99% of blood cells
b. Flattened, biconcave disk-shaped cells that lack nucleus & organelles
c. Short-lived (~120 days) – rapidly produced in bone marrow (see notes on hematopoiesis).
d. Contain Hemoglobin (Hb)
e. Hematocrit (Hct)
f. Anemias
Which is the most numerous blood cell?
Erythrocytes (Red Blood Cells)!
Most numerous blood cell. Makes up >99% of blood cells
- ~5 billion RBC’s per ml of blood
What is the shape of Erythrocytes (Red Blood Cells)?
Flattened, bioconcave disk-shaped cells that lack nucleus & organelles
What can the shape of Erythrocytes (Red Blood Cells) allow? & what happens if it changes?
specialized for gas transport. (to facilitate O2 transport from the lungs to cells, & CO2 transport from cells to lungs)
Shape can change due to disease (e..g. crescent shaped in sickle-cell anemia; spherocytosis, cells now round spheres instead of flattened disk).
What is the life span of Erythrocytes (Red Blood Cells)?
Short-lived (~120 days) – rapidly produced in bone marrow (see notes on hematopoiesis).
What do Erythrocytes (Red Blood Cells) contain?
Contain Hemoglobin (Hb)
- main component of RBC’s
- role in O2 transport
What is Adult Hemoglobin (Hb) (HbA) composed of?
Adult Hb (HbA) is composed of two a-globin and two b-globin protein chains, each of which bound to an iron containing heme group.
Hemoglobin (Hb)
- Globin
- Heme
Globin =
protein chains; binds and transports CO2
Heme =
Red pigment molecule - porphyrin ring surrounding an iron (Fe2+) atom that reversibly binds to O2. There are 4 hemes per Hb molecule, so each Hb transports 4 O2. Gives blood its red colour which can be seen through skin as a pink colour especially in areas of thin skin like like the lips.
Porphyrin ring
the 4 heme groups in a hemoglobin molecule are identical
- each consists of a C-H-N polyphyrin ring with an iron atom (Fe) in the center
Iron metabolism and Hemoglobin Synthesis
- Iron from diet actively transported into blood (excess stored in liver as ferritin)
- Transported in plasma by transferrin
- Iron is taken up in the bone marrow and used
to synthesize heme –> hemoglobin –> RBCs - RBCs live 120 days and are then broken down
in spleen
Transferrin
carrier protein; binds iron & transports it in the blood
Iron metabolism and Hemoglobin Synthesis (9 steps as per figure)
- Iron (Fe) ingested from the diet
- Fe absorbed by active transport
- Transferrin protein transports Fe in plasma
- Bone marrow uses Fe to make hemoglobin (Hb) as part of RBC synthesis
- RBCs live about 120 days in the blood
- Spleen destroys old RBCs and converts Hb to bilirubin
- Bilirubin & metabolites are excreted in urine & feces
- Liver metabolizes bilirubin & excretes it in bile
- Liver stores excess Fe as ferritin
Ferritin
protein that binds & stores iron in the body
- spherical protein; core of the sphere is an iron-containing mineral that can be converted to soluble iron & released when needed for hemoglobin synthesis
Heme:
- IRON removed and stored in liver (as ferritin), muscle, & spleen to be recycled for future use.
- PORPHYRIN RING: converted to BILIRUBIN – excreted in bile (& therefore feces) as well as urine (metabolites of bilirubin give feces and urine their colour).
Jaundice =
EXCESS bilirubin in blood (due to excess RBC breakdown, liver dysfunction, or blockage of bile excretion).
Symptoms include yellow skin and sclera of eye.
Common in neonatal infants because their livers are not yet fully functional (phototherapy oxidizes bilirubin and allows for excretion).
Globin:
converted to amino acids and recycled.
Hematocrit (Hct)
the % of blood volume that is erythrocytes.
What is Hematocrit (Hct) on average for women & men?
On average ~42% (women) and 47% (men)
What is Hematocrit (Hct) determined by?
Determined by Complete Blood Count (CBC).
Complete Blood Count (CBC)
Blood is centrifuged (spun in a test tube at high speeds to separate formed elements from plasma); result is a blood column separated into 3 layers:
i. RBCs packed at the bottom of the tube.
ii. Middle layer of WBCs (also known as the buffy coat)
iii. Upper layer of plasma.
Percentage of the blood column that is packed RBCs = hematocrit.
Percentage of the blood column that is packed RBCs = ______.
HEMATOCRIT
Polycythemia vera
High hematocrit can indicate dehydration or a condition such as POLYCYTHEMIA VERA, which causes the body to produce too many blood cells (both RBCs and WBCs), in which case hematocrit may be elevated to 60—70%
(increased # of cells causes the blood to become more viscous & thus more resistant to flow though the circulatory system)
A complete blood count (CBC), provides info in figure 16.3. The numbers shown are the normal ranges of values. In addition, a CBC usually also includes the following info:
- MEAN CORPUSCULAR VOLUME (MCV): the average volume of one RBC. A corpuscle is a small unattached cell (diminutive of corpus, body)
- MEAN CORPUSCULAR HEMOGLOBIN (MCH): amount of hemoglobin per RBC
- MEAN CORPUSCULAR HEMOGLOBIN CONCENTRATION (MCHC): the amount of hemoglobin per volume of 1 RBC
Anemias
low hemoglobin content of blood, which decreases its ability to carry oxygen
How do Anemias occur?
Occur due to blood loss (hemorrhage); accelerated rate RBC loss, or decreased RBC production.
What are examples of Anemias?
i. Hemolytic anemias
ii. Sickle cell anemia
iii. Aplastic Anemia
iv. Iron Deficiency Anemia
v. Vitamin Deficiency Anemia
Hemolytic anemias
cells RUPTURE at abnormally high rate; can be hereditary (when the body makes fragile cells) or acquired.
- e.g. HEREDITARY SPHEROCYTOSIS – defective cytoskeletal elements change cell shape to a sphere that ruptures easily in response to osmotic changes.
- Parasitic infections (acquired) such as malaria – parasite infects RBCs, proliferates and ruptures cells.
Hereditary spherocytosis
DEFECTIVE cytoskeletal elements CHANGE cell SHAPE to a SPHERE that RUPTURES easily in response to osmotic changes.
Sickle cell anemia
genetic disorder affecting amino sequence hemoglobin beta chain
- abnormal hemoglobin (that crystallizes when it gives up its O2) causes crescent shaped cells that cause blockages and reduced blood flow to tissues.
- creates tissue damage & pain from hypoxia
Aplastic Anemia
bone marrow has few stem cells, so ALL blood CELL production is REDUCED (including RBCs).
Iron Deficiency Anemia
low iron levels due to dietary deficiencies, blood loss (e.g. menstruation), inability to absorb iron (e.g. Celiac’s disease which damages absorptive surface of intestine)
less iron –> less heme –> less hemoglobin
Vitamin Deficiency Anemia
Dietary deficiency or trouble absorbing Folic acid, Vitamin C, or Vitamin B12 leads to abnormal RBC production (fewer cells, & larger cells).
In hypertonic media, RBC’s…
shrink up & develop a spiky surface when the membrane
In hypertonic media, RBC’s:
shrink up & develop a spiky surface when the membrane pulls tight against the cytoskeleton
In hypotonic media, RBC’s:
swells & forms a sphere without disruption of its membrane integrity
The _____ of RBC’s can provide clues to the presence of diseases
morphology
In some disease states, the size of RBC’s - the mean red cell volume, AKA the _______ - may be abnormally large or abnormally small
MEAN CORPUSCULAR VOLUME (MCV)
ex:
- RBC’s can be abnormally small, or MICROCYTE, in iron-deficiency anemia
- if they are pale due to lack of red hemoglobin, they are described as HYPOCHROMIC
If iron loss by the body EXCEEDS iron intake, the marrow doesn’t have adequate iron to make heme groups, & hemoglobin synthesis slows. What is this?
Iron Deficiency Anemia
Anemias may also be caused by failure of the bone marrow to make adequate amounts of hemoglobin. 1 of the most common ex’s of an anemia that results from insufficient hemoglobin synthesis is what?
Iron Deficiency Anemia
Iron Deficiency Anemia have either a..
LOW RBC count (reflected in a low hemocrit) or LOW HEMOGLOBIN content in their blood
- their RBC’s are often smaller than usual (MICROCYTIC RBC’s), & their lower hemoglobin content may cause the cells to be paler than normal, in which case they’re described as being hypochromic
