Lecture 20 - Blood function and composition 2 Flashcards
What are some characteristics of an erythrocyte?
-Biconcave shape for increased surface area
-Flexible (to pass through capillaries)
-No nucleus or mitochondria
-produced in bone marrow
-Primary cell content is hemoglobin
What do yogurt-making bacteria and RBC’s have in common?
Lactic acid fermentation
What is hemoglobin made up of?
- 2 alpha subunits
- 2 beta subunits
- heme group
How many hemoglobin molecules can one erythrocyte have?
300 million
How does iron bind with oxygen?
Reversibly
What colour is oxyhemoglobin and deoxyhemoglobin?
Oxyhemoglobin - bright red
Deoxyhemoglobin - dark red
Does hemoglobin release all of its oxygen at one time?
Not usually, amount of oxygen released depends on tissue need for oxygen
What does CO2 bind to in hemoglobin?
Amino acids. Forms carbaminohemoglobin
How does the binding of oxygen affect hemoglobin?
It reduces its affinity for CO2 and H+, allowing the CO2 to be displaced
If hemoglobin is in a deoxygenated state, what does it carry more of?
CO2
What is carbon monoxide poisoning?
Carbon monoxide binds competitively with oxygen and has a higher affinity. It binds to Hb irreversibly and therefore oxygen cannot bind
What characterizes anemia?
-Insufficient RBC’s
-Decreased Hb content
-Abnormal Hb
What is sickle cell anemia?
Hb is abnormal in shape, limiting its ability to carry oxygen and travel through capillaries
What is polycythemia?
An abnormal excess of RBC’s that increases the viscosity of the blood
What are 3 common causes of polycythemia?
-Bone marrow cancer
-A response to reduced availability of oxygen at high altitudes
-Kidney malfunction
How are old RBC’s removed from the system?
Phagocytosis by macrophages of the spleen
What can happen to an RBC as it ages?
It may acquire senescent antigens and lose its flexibility, which can cause it to become trapped in the spleen and destroyed by macrophages
What happens after an RBC is destroyed?
- Hb is converted to heme and globin
- Iron is released and stored in macrophage or released into circulation to go back to marrow
- Heme is converted to bilirubin
What are characteristics of leukocytes?
-Defend against bacteria, viruses, and other microbes
-Provide immunity
-about 1% of blood
-Has a nucleus
-Produced in bone marrow and lymphatic tissue
What are the 2 groups of leukocytes?
-Granulocytes
-Agranulocytes
What are granulocytes?
-Contain cytoplasmic membrane-bound granules
-neutrophils, eosinophils, basophils
What are agranulocytes?
-Lack obvious granules
-Lymphocytes and monocytes
What happens to the number of WBC’s during an infection?
It increases
What does pus consist of?
Dead WBC’s
What is the lifespan of an erythrocyte?
120 days
What is the lifespan of a WBC?
Depends on the cell:
-Several hours to days for most WBC’s
-Many years for a few memory cells
What are characteristics of neutrophils?
-40-70% of WBC’s
-Small granules that stain lilac
-Nucleus is multi-lobed
-6-9 days for development
-6 hours to a few days lifespan
What is the function of neutrophils?
Phagocytize bacteria
What are characteristics of eosinophils?
-1-4% of WBC’s
-Larger granules that stain orange
-Nucleus bi-lobed
-6-9 days for development
-8-12 days lifespan
What is the function of eosinophils?
-Kill parasitic worms
-Destroy antigen-antibody complexes
-Inactivate some inflammatory chemical of allergy
What are characteristics of basophils?
-0.5% of WBC’s
-Large granules that stain blue/purple
-3-7 days for development
-Few hours to days lifespan
What is the function of basophils?
-Release histamine and other mediators of inflammation
-Contain heparin (anticoagulent)
What are characteristics of lymphocytes?
-T and B cells
-20-45% WBC’s
-Large nuclei with little cytoplasm
-days to weeks for development
-hours to years lifespan
What is the function of lymphocytes?
Mount an immune response by direct cell attack (T cells) or via antibodies (B cells)
What are characteristics of monocytes?
-4-8% WBC’s
-U-shaped nucleus
-2-3 days development
-months lifespan
What is the function of monocytes?
-Phagocytosis
-Develop into macrophages in tissues
What is the smallest blood cell?
Platelet
What is the size of an erythrocyte?
6.5-8 um
What is the size range of leukocytes?
6 (lymphocyte) - 20 (monocyte) um
Why is leukopenia common in chemotherapy?
Because chemotherapy destroys fast growing cells, like leukocytes, hair, and intestinal epithelial cells
What is leukemia?
An abnormally high level of WBC’s in the bone marrow, which impairs normal marrow function
What are platelets?
Fragments from the cytoplasm of megakaryocytes without a nucleus
What do platelets usually look like?
Round, oval, or spiky
What is the lifespan of a platelet?
8-12 days
What is the primary function of platelets?
To limit blood loss
Where do platelets go after entering circulation?
A third go to the spleen for storage if a blood vessel ruptures, the rest remain in circulation
What is hematopoiesis?
The formation of new blood cells
How is hematopoiesis controlled?
Factors in the environment of the developing cell
How many blood cells are made on average per day?
100 billion
Where does hematopoiesis usually take place in adults?
Bone marrow of the axial skeleton
Where does hematopoiesis usually take place as a fetus?
Yolk sac, liver, and spleen
Where does hematopoiesis usually take place early in life?
Bone marrow of long bones
What are pluripotent stem cells?
The divide into committed stem cells, which then divide and differentiate into mature cells
What type of stem cell produces RBC’s and platelets?
Myeloid stem cell
What type(s) of stem cells produce WBC’s?
Myeloid stem cell -> myeloblast
Lymphoid stem cell -> lymphoblast
What is erythropoiesis and where does it take place?
-Formation of RBC’s
-Occurs in bone marrow from hematopoietic stem cells
What happens as an RBC matures?
Nuclei and most organelles are released from the cell and the cell becomes smaller
What is erythropoiesis regulated by?
Renal oxygen content
What is erythropoietin?
A hormone produced by renal cells (liver cells as a fetus) in response to decreased renal blood oxygen content
What does erythropoietin stimulate?
Erythrocyte production in the bone marrow
What can cause a drop in renal blood oxygen level?
-Reduced RBC’s (hemorrhage or excess RBC destruction)
-Reduced availability of oxygen to blood (high altitudes, pneumonia)
-Increased demand for oxygen
What are the 3 dietary requirements for erythropoiesis?
-Iron
-Vitamin B12
-Folic acid
