Gas Transport & Erythrocyte Physiology

Question 1

What are the functions of the blood?

Answer 1

1. Deliver nutrients and oxygen
2. Remove waste products
3. Maintain homeostasis
4. Circulation

Question 2

What is the Composition of Blood?

Answer 2

1. Hematocrit
   - 40% women, 45% men
   - 55% newborn
   - 35% 2 mo old
2. Plasma (55% of whole body)
   a. Water: 92% by weight
   b. Proteins: 7% by weight
   I. albumins
   ii. globulines
   iii. fibrinogen
   iv. regulatory proteins
   c. other solutes: electrolytes, nutrients, gases, waste
3. Erythrocytes : 4.2-6.2 million/cubic mm
4. Buffy Coat (<1% of whole body)
   a. platelets
   b. Immune cells: leukocytes: neutrophils, monocytes, lymphocytes, eosinophils, basophils

Question 3

What are the functions of erythrocytes?

Answer 3

1. carrying O2 from lungs to body
2. carrying CO2 from body to lungs
3. acid/base buffering

Question 4

Where do erythrocytes mature and why?

Answer 4

reticulocytes mature into erythrocytes entering circulation

In circulation erythrocytes mature based on oxygen demand

Question 5

What is erythropoietin (EPO)?

Where is it produced? and why?

Answer 5

Principle regulator of erythropoiesis

Produced by kidneys

In response to:

• anemia
• low Hb
• decreased RBF
• central hypoxia (pulmonary disease, altitude)

Question 6

What regulates erythropoietin (EPO)?

What does a genetic deletion of this result in?
What does impaired regulation lead to?

Answer 6

Hypoxia inducible factor (HIF)

• a transcription factor
• genetic deletion results in anemia, mutations in polycythemia
• impaired regulation leads to erythrocytosis

Question 7

What is the erythrocyte life cycle?

Answer 7

2x1011 RBCs produced daily
120 day life cycle

ruptures in the red pulp of the spleen

released hemoglobin is ingested by monocyte-macrophage cells immediately

Question 8

How are RBCs recycled or excreted after death and phagocytosis?

Answer 8

1. Globin –> Amino Acids –> Protein Synthesis
2. Heme –> Bilirubin –> Liver –> Small Intestines –> Urobilirubing –> Kidney –> urobilin –> Urine
3. Heme –> Fe-Transferin–> Liver –> Ferritin –> Bone –> Erythropoiesis in red bone marrow –> circulation for 120 days –> death/phagocytosis

Question 9

How does oxygen travel via blood?

Answer 9

1. Dissolved

2. Hemoglobin bound

Question 10

Is dissolved oxygen enough to sustain our needs?

Answer 10

No

Solubility is limited
95-100 mmHG
***3 ml O2/L Blood

CO is 30 L /min in exercise
= 90 ml O2/min

Tissue demand may be 3,000 ml O2/min

Question 11

What is normal blood hemoglobin?

Answer 11

14 g/dL in adult female

15.5 g/d: in adult male

Question 12

How many O2 molecules can reversibly bind to 1 hemoglobin?

How many alpha and beta chains?

Adult vs fetal form?

Answer 12

4

There are 4 heme sites

2 alpha, 2 beta chains

Adult form = hemoglobin A
fetal form = hemoglobin F

Question 13

What is the x-axis on the oxygen dissociation curve?

Answer 13

PO2 of blood (mm Hg)

Question 14

What is the left y-axis of the oxygen dissociation curve?

What is the normal value?

Answer 14

Oxygen saturation of % Hb saturation

% of available binding sites in Hb that have oxygen bound

Normal [Hb] = 15 g of Hb/ 100 ml blood

Question 15

What is the right y-axis on the oxygen dissociation curve?

Answer 15

Concentration of O2 in blood (ml/100ml)

Question 16

What is the Normal Oxygen concentration?

Answer 16

15 g Hb / 100 mL blood

1 g Hb can combine with 1.34 mL O2

15 x 1.34 = 20.1 ml O2 / 100ml blood
or
20.1 ml O2/dL blood

Question 17

What is the equation for oxygen saturation?

Answer 17

It’s the percent of available binding sites in Hb that have oxygen bound

= O2 combined with Hb / O2 capacity x 100

Question 18

What is O2 saturation if PaO2 > 60 mm Hg?

What about ml O2 / dl Blood?

Answer 18

O2 saturation is at least 85%

~17 ml O2/dl blood

Question 19

What is P50?

Answer 19

50% Hb saturation

Normally means 27 mm Hg PO2

This can shirt right or left