Blood and lymph

Question 1

2,3-diphosphoglycerate (DPG) levels are increased in?

A Chronic hypoxia
B Acidosis
C Hypocarbia
D Decreased temperature

Answer 1

A

Explanation
Thyroid hormone, growth hormone and androgens all increase the concentration. Acidosis inhibits red cell glycolysis and causes the levels to fall. Red cell 2,3 DPG concentration is increased in anaemia and in a variety of diseases where there is chronic hypoxia. Ascent to high altitudes also triggers a rise. Exercise has been reported to increase the levels within 60 min. Stored blood has lower levesl of 2,3,DPG and the ability of this blood to release oxygen is reduced.

Question 2

2,3-diphosphoglycerate (DPG) is decreased in all of the following except?

A Polycythaemia
B Stored blood
C Acidosis
D The presence of testosterone

Answer 2

D

Explanation
Thyroid hormone, growth hormone and androgens all increase the concentration. Acidosis inhibits red cell glycolysis and causes the levels to fall. Red cell 2,3 DPG concentration is increased in anaemia (due to the ensuing hypoxia) and in a variety of diseases where there is chronic hypoxia. However, if the hypoxia is severe enough to cause acidosis, the 2,3 DPG levels will fall. Ascent to high altitudes also triggers a rise. Exercise has been reported to increase the levels within 60 min. Stored blood has lower levels of 2,3,DPG and the ability of this blood to release oxygen is reduced.

Question 3

Which of the following causes a reduction in Hb-O2 affinity?

A Acidosis
B All of the options listed
C Increased temperature
D Increased 2,3- diphosphoglycerate (DPG)

Answer 3

B

Explanation
When any of the above occurs, a higher pO2 is required for Hb to bind to a given amount of O2.

The purpose of this effect is to allow the offloading of O2 form Hb. During exercise, your muscles become hot, hypercarbic and acidotic, the result is a right shift of the Hb-O2 curve to the right. A rightward shift means more unloading of O2 at a given P02 in a tissue capillary. Now for the same Pa02, there is less 02 bound to Hb, i.e. more is offloaded to the muscles where you need it. (There is a reduction in the Hb-02 affinity)

Note: the stem options are poor. I do not think they would say- “all of the options listed”. I have left the question as is. It is an important concept.

Question 4

Regarding Hb, which of the following statements is correct?

A Fe3+ binds O2
B It has an oxygen binding capacity of 1.7-1.8ml O2 per gram of Hb
C Globin is synthesized from porphyrin
D HbF has no beta chain

Answer 4

D

Explanation
HbF is foetal Hb and the beta chain is replaced by gamma chains

Haemoglobin synthesis requires the coordinated production of haem and globin. Haem is the prosthetic group that mediates reversible binding of oxygen by haemoglobin. Globin is the protein that surrounds and protects the haem molecule. Globin is a protein synthesised from amino acids.

Within haem, each of the four iron atoms in haemoglobin can reversibly bind one O2 molecule. The iron stays in the ferrous

(Fe 2+) state, so the reaction is OXYGENATION and NOT OXIDATION.

The atom Fe2+ reversibly binds O2 1.36-1.37ml O2 per gm Hb.

Extra: source Wikipedia

The iron ion may be either in the ferrous (Fe2+) or in the Ferric (Fe3+) state, but ferrihemoglobin (methaemaglobin) (Fe3+) cannot bind oxygen. In binding, oxygen temporarily and reversibly oxidizes (Fe2+) to (Fe3+) while oxygen temporarily turns into the superoxide on, thus iron must exist in the +2 oxidation state to bind oxygen. If superoxide ion associated to Fe3+ is protonated, the haemoglobin iron will remain oxidized and incapable of binding oxygen. In such cases, the enzyme methaemoglobin reductase will be able to eventually reactivate methemoglobin by reducing the iron centre.

Question 5

2,3 diphosphoglycerate (DPG) levels increase in all of the following circumstances except?

A Chronic hypoxia
B Congestive heart failure
C Acidosis
D Androgens

Answer 5

C

Explanation
Thyroid hormone, growth hormone and androgens all increase the concentration. Acidosis inhibits red cell glycolysis and causes the levels to fall. In an acidotic medium, the enzyme DPG mutase is inhibited and thus reduces levels of 2,3 DPG.

Red cell 2,3 DPG concentration is increased in anaemia and in a variety of diseases where there is chronic hypoxia. Ascent to high altitudes also triggers a rise. Exercise has been reported to increase the levels within 60 min. Stored blood has lower levesl of 2,3,DPG and the ability of this blood to release oxygen is reduced.

Question 6

Regarding granulocytes, which of the following statements is correct?

Your answer was not correct

A All have cytoplasmic granules
B Neutrophils have a half life of 4 days
C Eosinophils phagocytose viruses
D Basophils are identical to mast cells

Answer 6

A

Explanation
Basophiles only resemble mast cells and are not identical. Eosinphiles phagocytose parasites. The half life of neutrophiles is 6 hours in circulation

Question 7

The principle mechanism for transporting CO2 in the blood is which of the following?

A Carboamino groups
B Bicarbonate
C Haemoglobin
D Dissolved in blood by Henry’s law

Answer 7

B

Explanation
Of approximately 49ml of CO2 in each decilitre of arterial blood, 2.6ml is dissolved, 2.6ml is in carbamino compounds and 43.8ml is in HCO3

Question 8

The haemoglobin dissociation curve moves to the left under which of the following circumstances?

A Increased H+ concentration
B Hypercarbia
C Increased 2,3 diphosphoglycerate (DPG)
D Hypothermia

Answer 8

D

Explanation

A drop in temperature, an increase in the pH (alkalosis), a decrease in 2,3 DPG and a decreasing pCO2 all shift he haemoglobin dissociation curve to the left. Conversely, the opposite would shift it to the right

Question 9

Which organ has the highest percentage of blood flow per 100g?

A Kidney
B Skin
C Liver
D Heart muscle

Answer 9

Explanation
Kidneys= 420 ml/100g/min

Heart muscle= 84 ml/100g/min

Liver= 57.7 ml/100g/min

Brain= 54 ml/100g/min

Skin= 12.8 ml/100g/min

Whole body= 8.6 ml/100g/min

Skeletal muscle= 2.7 ml/100g/min

Question 10

Which organ has the greatest blood flow through it in ml/min?

A Liver
B Kidney
C Brain
D Skeletal muscle

Answer 10

A
Explanation
Whole body= 5400ml/min
Liver= 1500ml/min
Kidney= 1260ml/min
Skeletal muscle= 840ml/min
Brain= 750ml/min
Skin= 462ml/min
Heart muscle= 250ml/min

Question 11

The presence of haemoglobin in the blood increases the oxygen carrying capacity of the blood by

A 20 fold
B 100 fold
C 70 fold
D 50 fold

Answer 11

C

Explanation
Oxygen is transported as a dissolved entity in the blood. However, it is a very small and inadequate amount totalling 0.3mls 02 for every 100mls of blood (3mls/L)

Oxygen carried by Hb is a more effective way of transporting oxygen in the blood totalling 20.8mls 02 per 100mls of blood.

This is a 70-fold increase in the carrying of oxygen in the blood

0.3 X 70=21mls per 100mls of blood

Question 12

Erythropoietin is found in different tissues except?

A Salivary
B Brain
C Spleen
D Pancreas

Answer 12

D

Explanation
In adults, 85% of erythropoietin comes form the kidneys and 15% from the liver. Erythropoietin can also be extracted form the spleen and salivary glands. These two organs however, do not contain the mRNA for erythropoietin and consequently do not manufacture the hormone. Erythropoietin is also produced in the brain, uterus and oviducts.

Question 13

Regarding Haemoglobin, which is true?

A Has a molecular weight of 55000
B The alpha and beta chains contain the same amino acid residue numbers
C Fetal Hb has no beta chains
D There are two polypeptides in each Hb molecule

Answer 13

C

Explanation
Hb is a protein with a molecular weight of 64450. Hb is a globular molecule made up of 4 subunits. Each subunit contains a heme moiety conjugated to a polypeptide. There are TWO pairs of polypeptides in each Hb molecule. In normal adult human Hb (HbA), the two types of polypeptide are called alpha chains (each chain=141 amino acid residues) and beta chains (each chain=146 amino acid residues). Thus HbA is designated alpha2beta2. Not all the Hb in the blood is HbA. About 2.5% of the Hb is HbA2, in which the beta chains are replaced by delta chains. Each delta chains contains 146 amino acid residues. The blood of a human foetus contains fetal Hb where the beta chains are replaced by gamma chains (146 amino acid residues).

Question 14

When extra blood is transfused, where is it NOT distributed?

A Arteries
B Left ventricle
C Pulmonary veins
D Systemic veins

Answer 14

B

Explanation
At least 50% of the circulating blood volume is in the systemic veins. 12% is in the heart cavities, 18% in the low pressure pulmonary circulation, 2% in the aorta, 8% in the arteries, 1% in the arterioles and 5% in the capillaries. When extra blood is transfused, less than 1% of it is distributed in the arterial system (the high pressure system), and all the rest is found in the systemic veins, pulmonary circulation, and the heart chambers other and than left ventricle (low pressure system)- I KNOW WHAT A GREAT QUESTION!

Question 15

Which of the following does not increase 2,3 BPG (biphosphoglycerate)?

A Exercise
B Thyroid hormone
C Growth hormone
D Acidosis

Answer 15

D

Explanation
Acidosis inhibits red cell glycolysis. This leads to a decrease in 2,3 DPG. 2,3 DPG is a product of glycolysis via the Embden Meyerhof pathway. It is a highly charged anion that binds to the beta chains of deoxyhaemoglobin. In an acidotic medium, the enzyme DPG mutase is not inhibited and thus reduces levels of 2,3 DPG

Thyroid hormones, growth hormones, androgens and exercise (after 60min) increase the concentration of 2,3 DPG

Question 16

Which of the following substances does not casue vasodilation?

A Lactate
B Histamine
C A decrease in osmolality
D Hyperkalaemia

Answer 16

C

Explanation
The following substances are vasodilatory metabolites:

Increased osmolality, hyperkalaemia, lactate, histamine (from injured/inflamed tissues)

Other factors which lead to vasodilation: hypoxia, decreased oxygen tension, increased CO2 tension and an increase in temperature

Question 17

Which is true regarding blood as a circulatory fluid?

A The normal total circulating blood volume is 8% of the body weight
B Blood cells are produced in all bone marrow cavities of the long bones in adults
C It takes approximately three minutes for the total blood volume to circulate around the body at rest
D 60% of total blood volume is plasma

Answer 17

A

Explanation
Blood consists of a protein rich fluid called plasma, in which there are red cells, white cells and platelets. The normal total circulating blood volume is 8% of the body weight (5600ml in a 70kg man). About 55% of this volume is plasma. It takes approximately one minute for the total blood volume to circulate around the body at rest. WSC: 4000-11000/microlitre. RBS: 5.4million/microL (men) and 4.8million.micro/l (women). Platelets: 300000/microlitre. Blood cells are produced in all bone marrow cavities of the long bones in children. In adults only the cavities of the upper humerus and femur remain active.

Note: In the current textbook, total blood volume is said to be 8% of total body weight. In one part however, blood plasma is said to be 5% of total body weight. This means that 62.5% of total blood volume is plasma. In another section it reads that 55% of total blood volume is plasma, this would equate to 4.4% of total body weight

Question 18

In relation to type O blood group, which of the following statements is correct?

A The patient cannot receive 0+ blood
B Can donate to a person who is AB+
C The patient can receive A+ blood
D The patient can receive AB- blood

Answer 18

B

Explanation
Blood group O is the universal donor because it lacks anti A and anti B antigens. However, a full cross match should still be carried out where possible, due to the potential for reactions and sensitizations because of incompatibilities in systems other than ABO. Although such patients can receive O+ blood, if D - they will develop anti D antibodies and therefore risk suffering a transfusion reaction when given further D+ blood.

Note: Anti A and B antibodies would be produced by type O patients in response to being transfused A or B antigen containing blood.

Question 19

Which is not a compensatory mechanism during haemorrhage?

A Thirst
B Anxiety
C Venodilation
D Protein synthesis

Answer 19

C

Explanation
The rapidly acting compensatory mechanism (seconds–minutes) involves the autonomic nervous system. The increased activity of the sympathetic nerves produces the following effects:
(1) increased heart rate and cardiac contractility and
(2) increased arterial and venous contractions that cause increased TPR and venous return

The slow compensatory (days to weeks) mechanisms involve restoration of red blood cell and plasma protein concentrations

Decrease in the ECF volume also stimulates thirst by a pathway independent of that mediating thirst in response to increased plasma osmolality. Thus haemorrhage causes thirst even if there is no change in the plasma’s osmolality. Pain, anxiety, and haemorrhage combine to trigger systemic compensatory mechanisms designed to preserve perfusion of the most oxygen-sensitive organs: the brain and heart.

Question 20

With the loss of 1 litre of blood, which of the following will occur?

A Red cell mass normalises within 4-8 weeks
B Haematocrit falls immediately
C Baroreceptors increase parasympathetic output
D Iron resorption is not increased

Answer 20

A

Explanation
Once haemorrhage has ceased, the recovery of the red cell mass to normal is usually accomplished gradually by increased red cell production. Replacement of the red cell mass by increased red cell production is a gradual process. In response to erythropoietin stimulation, marrow progenitor cells must first proliferate and then mature over a period of 2 to 5 days prior to their delivery to the circulation as adult red cells. There is, therefore, a considerable time lag before red cell production can appreciably increase the red cell mass.

Iron resorption can increase several fold according to the body’s demand (e.g., during pregnancy, after an acute blood loss, or in menstruating women

In acute blood loss, baroreceptors will not discharge, thus preventing the vagal effect on blood pressure, and cardiac output

HCT does not drop immediately

Extra: a normal person can rapidly lose up to 20% of the blood volume without signs or symptoms of anaemia or cardiovascular collapse. If the haemorrhage exceeds 20%, signs of cardiovascular distress appear. At first, this is limited to tachycardia with exercise and postural hypotension. When the blood loss exceeds 30 to 40% of the blood volume, there is a fall in cardiac output and the gradual onset of shock

Question 21

Which concept explains why capillaries do not rupture?

A Laplace law
B Bernoulli’s equation
C Reynolds number
D Poiseuille-Hagen formula

Answer 21

A

Explanation
Law of Laplace

Structures as thin walled and delicate as the capillaries are not more prone to rupture. The principal reason for their relative invulnerability is their small diameter. The protective effect of small size in this case is an example of the operation of the law of Laplace, an important physical principle with several other applications in physiology. This law states that tension in the wall of a cylinder (T) is equal to the product of the transmural pressure (P) and the radius (r)divided by the wall thickness (w):

T=Pr/w

The transmural pressure is the pressure inside the cylinder minus the pressure outside the cylinder, but because tissue pressure in the body is low, it can generally be ignored and P equated to the pressure inside the viscus. In a thin walled viscus, w is very small and it too can be ignored, but it becomes a significant factor in vessels such as arteries. Therefore, in a thin-walled viscus, P=T divided by the two principal radii of the curvature of the viscus:

P=T(1/r1 +1/r2)

In a sphere, r1=r2, so

P=2T/r

In a cylinder such as a blood vessel, one radius is infinite, so

P=T/r

Consequently, the smaller the radius of a blood vessel, the lower the tension in the wall necessary to balance the distending pressure.

Question 22

Which of the following naturally occurring substances is responsible for the increase in the formation of plasmin

A Factor X
B Activated Protein C
C Fibrinogen
D Factor VIII

Answer 22

B

Explanation
Endogenous anticoagulants protein C and protein S inactivates factors V and VIII, and inactivates an inhibitor of tissue plasminogen activator, increasing the formation of plasmin.

Question 23

22-year-old male receives a blood transfusion, increasing serum Hb from 60g/L to 110g/L. What is the increase in the amount of oxygen the patient can carry per litre?

A ~ 7ml
B ~ 420ml
C ~ 140ml
D ~ 70ml

Answer 23

D

Explanation
The oxygen carrying capacity of Hb is 1.34ml/g. Therefore, a Hb increase of 50g/L increases the oxygen carrying capacity by approximately of 50 x 1.34 = ~ 70ml/L.

Question 24

A patient is transfused from Hb = 60 to Hb = 110. What approximate increased oxygen carrying capacity does this patient’s blood now have?

A 50ml
B 70ml
C 150ml
D 100ml

Answer 24

B

Explanation
One gram of pure Hb can combine with 1.34 ml O2. Therefore there is an increase oxygen carrying capacity of (1.34 x 50) = 69.5

Note: if you calculate using the new total blood volume of 110. 110X1.39=152.9

I am unsure if this may be a more correct answer than just calculating the transfused volume?

Extra: provided by a member

Step 1: Understanding the formula for oxygen carrying capacity Oxygen-carrying capacity of the blood depends on haemoglobin (Hb) levels because oxygen binds to haemoglobin. The formula for calculating oxygen-carrying capacity is: Oxygen carrying capacity=Hb concentration (g/dL)×1.34 (mL O2/g Hb)×SaO2 1.34 mL O₂/g Hb is the oxygen-binding capacity of haemoglobin. SaO₂ (arterial oxygen saturation) is typically ~100% under normal conditions (0.98 to account for physiologic variance). For simplicity, plasma-dissolved oxygen is usually negligible in this context. Step 2: Calculate the change in capacity 1. Before transfusion (Hb = 60 g/L or 6 g/dL): Oxygen carrying capacity=6 g/dL×1.34 mL/g Hb×0.98=7.87 mL O2/dL of blood. 2. After transfusion (Hb = 110 g/L or 11 g/dL): Oxygen carrying capacity=11 g/dL×1.34 mL/g Hb×0.98=14.47 mL O2/dL of blood. 3. Change in oxygen-carrying capacity: Δ=14.47−7.87=6.6 mL O2/dL of blood. Step 3: Total increase in carrying capacity Assuming an average adult blood volume of ~5 L (50 dL): Total change=6.6 mL/dL×50 dL=330 mL of oxygen. The options provided might consider oxygen distribution to 1 liter of blood, and recalculating: Change per liter=6.6×10=66 mL O2 Thus, the closest approximation is 70 mL, making the answer B. References: 1. Barrett, Kim E., et al. Ganong’s Review of Medical Physiology, 26th Edition. 2. Hall, John E., et al. Guyton and Hall Textbook of Medical Physiology, 14th Edition. 3. UpToDate: Oxygen delivery and consumption during anaemia.

Question 25

Parents are both blood group B. What blood group type will their children be?

A B and O
B AB
C O only
D B only

Answer 25

A

Explanation
When both parents are blood type B, they could have children with genotype BB, BO and OO

Same would apply if both parents were blood group A