Hematology- erythrocytes

Question 1

blood composition

Answer 1

-55% plasma
-45% formed elements: WBCs (leukocytes), RBCs (erythrocytes), platelets (thrombocytes)

Question 2

hematocrit

Answer 2

% of blood volume that is RBCs
47 % - or + 5% for males
42% - or + 5% for females

Question 3

characteristics of blood

Answer 3

• pH: 7.4
• temp: 38 C (100.4 F)
• % of body weight: 8%
• volume: 5-6 L males, 4-5 L females

Question 4

functions of blood

Answer 4

1. distribution
2. regulation
3. protection

Question 5

functions of blood: distribution

Answer 5

distribution of…
- O2 and nutrients to body cells
- metabolic wastes to the lungs and kidneys for disposal
- hormones from endocrine organs to target organs

Question 6

functions of blood: regulation

Answer 6

regulation of…
- body temperature by absorbing and distributing heat
- maintain normal pH using buffers
- adequate fluid volume in the circulatory system

Question 7

functions of blood: protection

Answer 7

protection against…
- blood loss (proteins and platelets initiate clot formation)
- infection: antibodies and WBCs defend

Question 8

blood plasma composition

Answer 8

90% water
8% proteins
1%: nitrogenous by-products of metabolism (lactic acid, urea, creatinine. nutrients (main four macromolecules from food) O2 and CO2, electrolytes, hormones)

plasma is a suspension for WBCs and RBCs

Question 9

what’s special about WBCs?

Answer 9

they are the only type of complete cells

RBCs have no nucleii or organelles, and platelets are fragments of cells

Question 10

formed elements

Answer 10

most formed elements survive int eh bloodstream for only a few days

most blood cells come from stem cells in marrow and don’t divide.

Question 11

erythrocytes

Answer 11

• biconcave disks (allows flexibility and good SA:V), anucleate, no organelles
• filled with hemoglobin (Hb) for gas transport
• major factor contributing to blood viscocity

Question 12

erythrocyte function

Answer 12

• dedicated to gas transport
  this is because hemoglobin binds reversibly to O2, so the O2 can be released and exchanged
• hemoglobin structure: protein globin and heme pigment bonded to each other
• iron atom in each heme can bind to one O2 molecule
• each Hb molecule can transport four O2 molecules

Question 13

Hemoglobin (Hb)

Answer 13

• O2 loading in the lungs produces oxyhemoglobin (bright ruby red)
• unloading in the tissues because of reversible reaction produces deoxyhemoglobin (deep red)
  -CO2 loading in tissues produces carbaminohemoglobin which carries 20% of CO2 in blood

Question 14

how does blood “know when to release O2?

Answer 14

• binding of O2 to Hb is affected by CO2 concentration (high CO2 concentration, low pH concentration)
• the chemical rxn when tissues put out CO2 changes the shape of the Hb protein which then kicks off oxygen.

Question 15

hematopoiesis/hemopoiesis/ERYTHROPOIETIN (EPO)

Answer 15

blood cell formation
- occurs in red bone marrow
- hemocytoblasts (blood stem cells) give rise to all formed elements

Question 16

erythropoiesis

Answer 16

RED blood cell production

1. stem cell (hemocytoblast) comes in contact with EPO (chemical hormone)
   
   • when EPO is present, the stem cell differentiates into…
2. proerythroblas
3. turns into erythrobast
   
   • makes ribosomes and accumulates Hb
4. turns into nomoblast
   
   • kicks out nucleus and becomes…
5. reticulocyte differentiates into…
6. erythrocyte

Question 17

regulation of erythropoiesis

Answer 17

• too few RBCs lead to tissue hypoxia
• too many RBCs increases blood viscosity
• balance between RBC prodution and destruction depends on: hormonal controls and good supplies of iron, amino acids (used to make globin part of Hb)

Question 18

hormonal control of erythropoiesis

Answer 18

EPO (erythropoietin)
- direct stimulus for erythropoiesis
- released by kidneys in response to hypoxia

Question 19

causes of hypoxia

Answer 19

• hemorrhage or increased RBC destruction that reduces RBC #s
• insufficient Hb (iron deficiency)
• reduced availability of O2 (high altitude, vigorous exercise, lack of breathing)

Question 20

effects of EPO

Answer 20

• more rapid maturation of bone marrow cells
• increased circulating reticulocyte count in 1-2 days
• testosterone enhances EPO prodction

Question 21

if stimulus interrupts blood homeostasis…

Answer 21

1. kidney releases EPO
2. EPO stimulates red bone marrow
3. enhanced erythropoiesis increases # of RBCs
4. O2 carrying ability of blood increases

Question 22

erythrocyte life cycle

Answer 22

• life span: 100-120 days
• old RBCs become fragile and Hb begins to degenerate
• macrophages engulf dying RBCs in the spleen
• when the RBCs die, they get broken down into heme and globin
  
  • iron is saved for re-use
  • heme is degraded to yellow pigment, bilirubin
  • liver secretes bilirubin (in bile) into intestines
  • shit out bilirubin
  • globin is metabolized into amino acids

Question 23

erythrocyte disorders anemia

Answer 23

anemia: blood can’t carry enough O2
- category of diseases
- blood O2 levels can’t support normal metabolism
- accompanied by fatigue, paleness, shortness of breath, and chills

Question 24

causes of anemia

Answer 24

1. low # of RBCs
2. low hemoglobin count
3. pernicious anemia
4. abnormal hemoblogin

Question 25

causes of anemia: insufficient RBCs

Answer 25

- hemorrhagic (bleeding) anemia: acute or chronic loss of blood - hemolytic anemia: RBCs rupture - aplastic anemia: destruction or inhibition of red bone marrow, not making enough RBCs as should be

Question 26

causes of anemia: low hemoglobin count

Answer 26

- iron deficiency anemia: secondary result of hemorrhagic anemia or not eating enough iron or impaired iron absorption in digestion

Question 27

pernicious anemia

Answer 27

- not enough B12 - lack of intrinsic factor needed for absorption (in intestines) - treated by injection of B12

Question 28

abnormal hemoglobin

Answer 28

- thalassemia: globin made wrong, so RBCs are shaped differently (fragile, thinly shaped) - sickle cell anemia: 1 DNA base pair is changed for abnormal hemoglobin. causes RBCs to become sickle shaped (half moon) in low oxygen situations - polycythemia: excess of RBCs that increases blood viscosity. results from bone marrow cancer, less available O2, blood doping.