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1

Blood plasma

water + electrolytes (Na+, Cl-, K+, HCO3-, Ca2+), plasma proteins, glucose, urea, etc.

2

Formed Elements

erythrocytes (RBCs) - 5,000,000/uL
leukocytes (WBCs) - 5,000-10,000/uL
platelets

3

RBCs

are anucleated cells, filled with hemoglobin
blood cells are produced in red bone marrow from hematopoietic stem cells

4

hematocrit

= % by volume of RBCs (normally 45%)

5

erythropoietin

hormone produced by kidneys, stimulates production and differentiation of RBCs

6

polycythemia

high RBC count (high hematocrit)

7

anemia

low O2 carrying capacity of blood (low hemoglobin concentration)

8

Hemoglobin structure and function

protein composed of 4 polypeptide (globin) subunits (2 a, 2B)
each subunit contains a heme group with iron (Fe2+) at the center
each heme reversibly binds O2 (-> 4 O2 binding sites)

9

Oxygen transported by blood

1. O2 dissolved in plasma
2.O2 carried by hemoglobin
3. oxygen-hemoglobin dissociation curve
4.factors that affect O2 affinity of hemoglobin

10

O2 dissolved in Plasma

low solubility of O2 in plasma
at Po2 = 100 mm Hg, plasma: 3 mL O2 / L blood
whole blood: 200 mL O2 / L blood

11

O2 carried by hemoglobin

99% of O2 in blood is carried by hemoglobin
O2 carrying capacity of blood depends on hemoglobin concentration

12

Hemoglobin-O2 binding

deoxyhemoglobin (Hb) + O2 -><- oxyhemoglobin (Hb O2)

13

Binding and release of O2 depends on:

1. PO2 of the blood
2. affinity of hemoglobin for O2

14

Oxygen Hemoglobin Dissociation Curve

relationship between Po2 of blood and percent O2 saturation of hemoglobin
S-shaped curve results from interactions among hemoglobin subunits -> promotes loading of O2 in the lungs and unloading of O2 in the tissues

15

Normal Values (curve) (resting, sea level)

arterial Po2 = 100 mm Hg, 98% O2 saturation
venous Po2 = 40 mm Hg, 75% O2 saturation

16

In lungs

Po2 = 100 mmHg
flat part of curve -> nearly 100% saturated

17

In tissues

Po2 < 60 mm Hg -> rapid unloading of oxygen as Po2 decreases

18

During exercise

tissues Po2 decreases -> more O2 released from Hb -> O2 sat. of venous blood

19

Pulmonary disease

Pulmonary disease -> decrease arterial Po2 -> decrease O2 saturation (hypoxemia)

20

At high altitude

decrease in arterial Po2 -> decrease O2 saturation

21

Factors that affect O2 affinity of hemoglobin

1. increase temp -> decreases affinity (rightward shift of O2 dissociation curve)
2. decrease pH (increase [H+]) -> decreases affinity - (bohr shift)
3. increase PCO2 -> decrease affinity
4. increae 2, 3-DPG -> decreased affinity

22

rightward shift

means more O2 will be unloaded from Hb at a given Po2

23

in active tissues

increase temp, decrease pH and increase Pco2 promote unloading of O2

24

Carbon Dioxide transport by blood

1. dissolved Co2 plasma (10%)
2. bicarbonate (70%)
3. carbamino hemoglobin (20%)

25

Bicarbonate

Co2 + H20 -><- H+ + HCO3-
in tissues high PCO2 drives reaction forward to form HCO3-
in lungs, lower PCO2 pull reactions in reverse, HCO3- is converted back into CO2

26

carbonic anhydrase

in RBC catalyzes conversion of CO2 to carbonic acid
CO2 is a major source of H+ in the body
increase PCO2 -> decrease pH

27

Buffer

hemoglobin acts as a buffer of H+ formed by the reaction

28

HCO3-

is transported from RBC out to plasma in exchange for Cl-

29

carbamino hemoglobin

binding of Co2 to amino end of hemoglobin chains