17 6-9 Flashcards
Formed elements of the blood?
Erythrocytes, leukocytes, platelets
- only leukocytes are true cells 3. do not divide
Structure of erythrocytes? 5
Lack nuclei and most organelles.
97% hemoglobin, 250mil each cell
Biconcave discs.
Spectrin maintains shape.
Two principal proteins: hemoglobin and carbonic anhydrase
Importance of biconcave structure? 4
- ↑ surface to volume ratio
- Enables RBCs to form stacks that smooth the flow of blood thru narrow vessels (rouleau)
- Enable RBCs to bend and flex through capillaries - spectrin is a fibrous protein that forms cytoskeleton/infrastructue to assist with this.
- Aids in diffusion
Function of erythrocytes?
Transport respiratory gases - O2/CO2
Length of life cycle of erythrocytes?
700 miles, 120 days
C + C RBC/WBC
Structure: biconcave disc/uniform varies
Function: Carry O2+Co2, identical varies
Number: Constant varies
Location: Blood tissues
Hemoglobin structure
Made of protein globin bound to red heme pigment.
4 polypeptide chains, each chain has a heme pigment, each heme has an iron atom in the middle.
2 alpha and 2 beta chains.
Hemoglobin function
It is an oxygen binding pigment that is responsible for the transport of most of the o2 in the blood and 20% of the carbon dioxide.
Where is extra iron stored?
Liver, some in red marrow
What do the alpha and beta chains in Hb do?
They bind to carbon dioxide via the action of carbonic anhydrase forming carbaminohemoglobin.
Occurs more readily when hemoglobin is disassociated from O2.
When oxygen binds to iron in hemoglobin it is called? When it detaches?
oxyhemoglobin, deoxyhemoglobin (or reduced hemoglobin)
Hematopoiesis
Blood cell formation (any type)
Hemocytoblasts?
mother of all blood cells, pluripotent stem cells
Erythropoiesis
Formation of erythrocytes
Reticulocyte count
Reticulocytes account for 1-2% of all erythrocytes.
A count can indicate abnormal rates of erythrocyte formation.
Mother of all cells?
Hemocytoblast/myeloid stem cell
- Describe the process of erythroPOIESIS (lifecycle)
Hemocytoblast/myeloid stem cell –> differentiates into committed proerythroblast which is stimulated is stimulated by EPO, several stages - loses the nucleus, is released into the blood as a reticulocyte. (about 15 day process)
Reticulocytes still contains a few ribosomes and are loaded with and producing as much hemoglobin as possible.
Reticulocytes become mature and functional in a couple days after entering blood.
Dietary requirements to make RBCs
Iron, B12, folic acid, macronutrients
Recycling process of RBCs
- Aged and damaged RBC are engulfed by macrophages of spleen/liver/bone marrow. (loss of flexibility or hemoglobin degeneration)
Hemoglobin is broken down.
Globin: goes back in the bloodstream as amino acids.
Heme: Iron is stored as ferritin or hemosisiderin then released from liver(bound to transferrin) as needed for erythropoesis.
Biliverdin –> Bilirubin is picked up by the liver, secreted in bile into intestine, metabolized to urobiligen, then stercobilin by bacteria, then excreted.
Steps in making RBCs (homeostatic response)
- hypoxia (due to: ↓ RBC count, ↓ amount of hemoglobin, ↓ availability of O2
- Kidney releases EPO (and to a lesser extent the liver)
- EPO stimulates red marrow
- Enhances erythropoiesis increases RBC count
- O2 carrying ability of blood increases
Iron needs to be transported and stored as/by?
transport transferrin and storage ferritin or hemosiderin proteins
Anemia?
conditions marked by a reduction in the hemocrit, the Hb or both
The bloods O2 carrying capacity is too low.
Sickle cell anemia
results from a mutation affecting the amino acid sequence of the beta chains of Hb
Pernicious anemia
Due to an inability to absorb enough B12 due to a deficiency of intrinsic factor (a protein that allows for the absorption of B12.)
Polycythemia
Making too many RBCs.
Primary polycythemia - tumor of bone marrow,
Secondary polycythemia - adaptive mechanism (living at high altitude.)
Thalassemia
Mediteranean ancestry, one of the globin chains is absent or faulty and erythrocytes are thin/delicate/hemoglobin deficient
Iron deficiency anemia
Secondary result of hemorrhagic anemia or lack of iron in diet
Renal anemia
Lack of EPO
Aplastic anemia
results from the destruction of inhibition of red bone marrow by drugs/chems
