Topic 6: Physiological role of the blood, definitions and changes in blood volumes Flashcards

1
Q

What should be mentioned in this topic?

A
  • Physiological Role of Blood
  • Hematocrit
  • Sedimentation Rate
  • pH of the Blood
  • Determination of Blood Volume
  • Changes of Blood Volume
  • Factors affecting Blood Volume
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2
Q

Physiological Role of Blood:

A
  • Important buffer
  • takes part in defence
  • Important in homeostasis (coagulation) = Reacts after vessel injuries.
  • Maintains homeostasis–> Isovolemia, Isotonia, Isoionia, Isohydria
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3
Q

Hematocrit

A

It shows the proportion of corpuscular elements relative to the whole volume. It is an important diagnostic parameter.
Average value is around 40% or 0.4.

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4
Q

Sedimentation Rate

A

The determination of the sedimentation rate is done using anticoagulated blood put in a standard size tube. The thickness of the plasma layer formed on the top of the tube is measured in certain time periods.

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5
Q

pH of the Blood

A
  • Blood pH is 7.35-7.45
  • Extremely stable
  • Can with stand fluctuations for short periods 7.1-7.6
  • pH arterial > pH venous due to transport of CO2
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6
Q

Calculation of Blood Volume:

A

Calculation of Blood Volume (V) on the basis of plasma volume (Vp) or blood cell volume (Vrbc) In case of Ht value being known:

  • V=Vp/(1-0.9xHt)
  • V=Vrbc/0.9xHt
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7
Q

Blood transports:

A

The primary function of blood is transportation. It is the main transport medium of:

  • Gases
  • Nutrients
  • Metabolites
  • Information
  • Heat
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8
Q

Blood as buffer:

A

As a buffer there are two types found in the blood:

  • Bicarbonate – 53%
  • Non bicarbonate – 47%
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9
Q

What does blood consist of?

A

Blood is a liquid connective tissue consisting of 90% water. It consists of blood plasma and suspended cellular elements. It can be separated into a liquid phase and corpuscular elements.
Plasma contains fibrinogen.

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10
Q

Stages of normovolaemia:

A

1: Normocythaemic normovolaemia – healthy stage
2: Polycythaemic normovolaemia
– haemoconcentration
– viscosity increases
– increased load on heart (turbulence)
3: Olygocythaemic normovolaemia
– haemodilution
– blood gets diluted with concurrent normal volume

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11
Q

Stages of hypovolaemia

A

1: Normocythaemic hypovolaemia (Oligaemia) – blood cells and plasma loss together
– blood loss
– plasma replaced quickly, cells return slowly

2: Polycythaemic hypovolaemia – anhydraemia: lack of water, thirst – end up with haemoconcentration
3: Olygocythaemic hypovolaemia

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12
Q

Stages of hypervolaemia:

A

1: Normocythaemic hypervolaemia – plethora
– excess transfusion
– permanent, exhausting physical work

2: Polycythaemic hypervolaemia

3: Olygocythaemic hypervolaemia – hydraemia
– intake of excess water
– infusion (followed by haemodilution)

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13
Q

What are the factors affecting blood volume?

A
  • amount of body fat
  • position of the body
  • muscle work
  • climate
  • nutrition
  • lack of oxygen
  • sympathetic activity
  • pregnancy
  • blood loss
  • age
  • changes in the total water supply
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