3 - Blood Physiology Flashcards
(98 cards)
RBCs can concentrate hemoglobin in the cell fluid up to:
34g/100ml of CELLS
This is the metabolic limit of the cell’s hemoglobin-forming mechanism
In normal people, the percentage of hemoglobin is almost always:
the maximum percentage (34% of cells, which equates to 14-15g/dL)
How does hemoglobin circulate in humans?
INSIDE RBCs (not bound to the outside)
How much oxygen can be carried by hemoglobin in 100ml of blood?
Each g of Hgb can bind with 1.34ml O2, which means
19-20ml O2/100ml blood
Where are RBCs produced in utero? After birth?
Liver
Bone Marrow
When do long bones stop producing RBCs?
Around 20 years old
RBCs in adults are produced in which bones?
membranous bones: vertebrae, ribs, sternum, ilia
All cells in circulating blood are derived from which cell?
multipotential hematopoetic stem cell
How is the supply of multipotential hematopoetic stem cells maintained?
Every time one is triggered to reproduce, it produces another stem cell in addition to the other cells it multiplies into
Which growth inducer promotes growth and reproduction of virtually all the different types of committed stem cells?
Interleukin-3
What differentiates a reticulocyte from a full grown erythrocyte?
still contains a small amount of basophilic material (remnants of unnecessary organelles)
These organelles disappear over 1-2 days
The principal stimulus for RBC production in a low oxygen state is:
circulating erythropoietin
On a cellular level, how do the kidneys trigger RBC production in hypoxemic states?
Renal tissue hypoxia leads to high levels of Hypoxia-Inducible Factor 1 (HIF-1)
HIF-1 is a transcription factor, increasing transcription and production of erythropoietin
If erythropoietin is produced in the kidneys, why do RBC levels increase if other parts of the body are hypoxemic, even if the kidneys are not?
Somehow other tissues are able to send signals to the kidney
Circulating NE, Epi, and prostaglandins also stimulate erythropoietin
If someone’s kidneys are both removed or dead, how much erythropoietin can they make?
About 10% of normal, which is the percentage usually made by the liver
In hypoxic states, erythropoietin is produced within minutes. How long does it take for new RBCs to appear?
About 5 days
Erythropoietin stimulates growth, but it also increases the RATE of RBC production
Which two vitamins are essential to the final maturation of RBCs?
Why?
Vitamin B12 and Folic Acid
Required for formation of thymidine triphosphate, which is a building block of DNA
What are the characteristics of blood cells formed with deficient Vitamin B12 and/or Folic Acid?
Large RBCs (macrocytes)
flimsy membranes
Irregular shapes
they can carry oxygen, but have live about half or 1/3 as long d/t fragility
Vit B12/Folic Acid deficit anemia is called:
maturation failure anemia
Why is intrinsic factor necessary for B12 absorption?
Binds tightly with B12, and the binding protects from digestion by secretions
IF ferries it to the brush border and transports it into the blood via pinocytosis
Where is B12 stored?
Liver
Released in response to bone marrow levels
How long does abnormal B12 absorption have to take place to cause anemia?
Takes about 3-4 years to work through all the B12 stored in the liver
Besides deficient intrinsic factor, what else can cause B12/folic acid deficiency?
Any sort of malabsorption syndrome (sprue)
The most common form of hemoglobin in adults is:
Hemoglobin A