Blood physiologyBasics

© katarina.babinska@fmed.uniba.sk

Institute of Physiology

Comenius University

Bratislava

2019

Blood

- plasma (liquid part) – water + dissolved substances

- blood elements (corpuscles):

1. erythrocytes - red blood cells

2. leukocytes - white blood corpuscles

3. thrombocytes - platelets

All blood components

have specific functions

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DefinitionRed, opaque liquid circulating in blood vessels.

What are the main blood components?

NORMAL BLOOD VOLUME

7-8 % of body weight

male 6 l

female 4,5 l

= normovolaemia

Hypovolaemiae.g. in

• bleeding

• dehydration

hypervolaemia

• e.g. in kidney

disease/anuria

- for normal body function constant blood volume is needed

- major blood loss is a life threatening event

1. blood circulates in blood vessels – ideal medium for transportation

(from one part of the body to another):

- O2 and CO2 (lungs tissues)

- nutrients (gut – liver/tissues)

- waste products to places of their elimination (tissues → kidney, liver)

- hormones

- cells and molecules involved in immune functions

- heat (produced mainly in liver, muscles → all over the body)

- medicaments, etc.

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General functions of blood

2. blood helps to maintain homeostasis in the body

- homeostasis = constant internal environment in the body

despite fluctuations in external environment

(e.g. varying external temperature/constant body temperature)

Homeostasis

- is vital for normal function/survival of the human body

- is regulated by different control mechanisms (feedback mechanisms)

- blood is a part of a wide range of homeostatic mechanisms (e.g. regulation of thevolume of body fluids, glycemia, body temperature, etc.)

3. Haemostatic function of blood

- haemostasis = bleeding arrest

- components of blood (platelets, clotting factors) are

activated in case of bleeding in order to stop the bleeding

4. Maintenance of blood pressure

- blood pressure – pressure of blood on the vessel wall

- normal blood volume is required for maintenance of normal blood pressure

- massive bleeding → decreased blood volume → a decline in blood pressure

- the proportion of blood volume occupied

by the red blood cells

haematocrit =

plasma

leukocytes and

platelets (buffy coat)

erythrocytes

erythrocyte volume________________blood volume

centrifugation

males

39 - 49% (0,39 – 0,49)

females

35 - 43% (0,35 – 0,43)

Normal values

Blood examination: HAEMATOCRIT (PCV-packed cell volume)

causes a change in

erythrocyte count

a change in blood volume

(plasma volume)

decreased

hematocrit

- count, size of RBCs

- bleeding - after infusion

- kidney failure (oliguria/anuria)

increased

hematocrit

- large RBCs

- living in high altitudes

- polycytemia

- dehydration

Abnormalities of haematocrit

normal

low highdecreased

increasedincreased

decreased

Blood examination: Erythrocyte sedimentation rate

-a common examination in clinical medicine

Blood is a suspension (type of solution containing solid particles)

- plasma (water, dissolved substances)

- blood elements - solid particles that are heavier than plasma

If blood sample is put into a tube

(with anticoagulant to prevent clotting)

- erythrocytes sink to the bottom (because they are heavier)

- leave behind transparent upper layer of plasma

= Er sedimentation

Determination of sedimentation rate

- in tubes (e.g. Westergren tubes, Sedivettes)

- size of the plasma layer in the sample is measured

1st hour

males 2 – 5 mm (up to 15 mm)

females 3 – 8 mm (up to 20 mm)

2nd hour

two times the value in 1st hour

or less (but not more !)

start 1st hour 2nd hour

Normal values (normal FW)

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Abnormalities of sedimentation rate

(higher sedimentation rate, lower sedimentation rate)

Causes

• disturbances of blood composition (less red blood cells, elevated plasma

proteins, dyslipidemia ....) - the sedimentation rate may become abnormal

• the most common cause of high sedimentation rate

is inflammation – due to increased concentration of

inflammatory proteins

• ESR can be slightly higher during periods or pregnancy

Why do the females have higher sedimantation rate ?

- lower erythrocyte count

- higher concentration of fibrinogen (plasma protein)

erythrocytes - charged

plasma proteins + charged

blood 4 – 5,3 (x higher than water)

plasma 1,5 – 2 (x higher than water)

- viscosity depends on:

erythrocytes – count, size, shape

plasma protein concentration

velocity of blood flow

diameter of the vessel

Hyperviscosity of blood (occurs in some conditions)

- excessive load for the heart

- aggregation of erythrocytes in small vessels - stops the blood flow – hypoxia

VISCOSITY

- resistance of blood (liquid) to flow (due to internal friction of blood

layers during blood flow + friction of blood and vessel walls)

- expressed in relation to distilled water (without units)

- viscosity of distilled water = 1

Erythrocytes – red blood elements (corpuscles)

Function transport of the respiratory gasses O2, CO2

• erythrocytes lack nucleus and some other organelles -not true cells• thus the capacity to transport oxygen is increased

Shape - biconcave disc

capillary

capillary

EryAdvantages of the biconcave shape:

1. larger surface for gas diffusion – a surface of

biconcave disc is by 30% larger in comparison with a ball

of the same diameter

2. erythrocyte can change its shape (deformability) –

allows to pass through capillaries with diameter lower than

diameter of erythrocyte

(abormal shapes: spherocytes, drepanocytes, anuloces, etc. –

results in abnormal function and faster destruction)

Erythrocyte count

Abnormalities

males 4,3 – 5,3. 1012.l-1

females 3,8 – 4,8. 1012.l-1

hypererythrocytosis

(polycytemia,

polyglobulia)

- conditions associated with hypoxia

e.g. long term stay in high altitudes

- newborn babies (7-8. 1012.l-1 )

- abnormally high RBC production

erythrocytopenia - less RBCs - often in anemias

Size

diameter (mm)

microcytes < 6,7

normocytes 7,2 ± 0,5

macrocytes 7,7 – 9

megalocytes > 9

7,2 mm

2,1 mm

HAEMOLYSIS

destruction of the erythrocyte membrane, hemoglobin is released from erythrocyte (e.g. into plasma) (opaque suspension transparent solution)

osmotic- hypertonic solution

- hypotonic solutionminimal osmotic resistance: 0,44-0,40 g .l-1 NaCl

maximal osmotic resistance: 0,34-0,30 g .l-1 NaCl

chemical

- acids, bases, tensides

physical

- thermic energy, irradiation, mechanic energy

(e.g.artificial heart valves)

immune- transfusion of incompatible blood

toxic

- cell lysis caused by enzymes in poison of snakes,

wasps, spiders, plants

- daily approx 1% of Ery do hemolyse – old elements

- hemolytic anaemia – decereased Hb concentration due to excessive hemolysis

isotonic

hypotonic

hypertonic

Blood plasma

- tekutá zložka krvi svetložltá

priehľadná tekutina,

- 4-5 % telesnej hmotnosti

Body fluid compatments (as % of body weight)

Total body fluids 60%

1. intracellular (ICF) 40%

2. extracellular (ECF) 20%

- intravascular (plasma, lymph) 4 - 5%

- interstitial (among cells in tissues) 15%

- transcellular 1 %

(intraocular, synovial, pericardial, peritoneal, cerebrospinal fluid, etc.)

- ECF and ICF differ in ion composition

Main ions in - extracellular fluid: Na+, Cl-, HCO3

-

- intracellular fluid: K+, PO4-

sušina

15 %

1%

4 % 40 %

40 %

ICT

ECT ECF

ICF

dry matter

- liquid part of blood, component of the body fluids

- yellow transparent fluid

- components: water + an array of dissolved substances (physiological concentrations)

Blood plasma and its composition

Inorganic compounds

sodium, calcium, potassium,

iron, magnesium, copper, iodine

chlorides, bicarbonate,

phosphate

Plasma proteins

albumins

globulins

fibrinogen

Dissolved

substances(10 %)

Water(90 %)

Organic substances

Glucose Cholesterol Triacylglycerols

Creatine Creatinine Urea

Uric acid Bilirubin Hormones

Vitamins etc.

Thrombocytes – blood platelets

• cell fragments split from megakaryocytes

• do not contain nucleus

• shape of disc, diameter 2 – 4 mm

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Function

• haemostasis - formation of the platelet plug

– blocks the „hole“ in the injured vessel

Normal count

- life span 9 days

- Thrombocytopenia – lower than normal

count of platelets

150 – 350.109 . l-1

• cell membrane of platelets

- invaginations – channel

system communicating with

the surface of a platelet

- receptors – make the

platelets „sticky“ when

bleeding occurs

• cytoplasm of the platelets

- vesicles (granules: a, b, d) - contain substances necessary for blood clotting:

ADP, ATP, Ca++, platelet clotting factors, enzymes

- fibres = microfilaments – allow contractility of the platelets

- dense tubular system – a store of calcium

(without calcium the blood clotting does not proceed)

- real cells – contain nuclei and organelles

- largest formed elements in blood

- lack colour („white“), become visible after

staining (e.g. the Pappenheim method)

Function

– defence against foreign material - „seek out and destroy“

– main cells of the immune system - „mobile units“

transported by blood to all parts of the body

from blood move into tissues, where they

spend most of their lives

Normal count

Leukocytes – White blood cells

adults, children 4 - 10.109.l-1

newborns 18 - 20.109.l-1

- abnormal (production of new Le)

• infectious diseases

• intoxication

• cancer

Leukocytosis – increased Le count

- normal (Le released from stores)

• after meal (postprandial)

• heavy physical activity

• emotional stress

• hot environment

• pregnancy

Leukopenia – decreased Le count

• some diseases (e.g. influenza, tuberculosis)

• some medicaments

adults, children 4 - 10.109.l-1

Leukocyte count

- varies throughout the day

minimum in the morning

maximum in the afternoon

Types of leukocytes

• granulocytes

-specific granules (vesicles)

-lobulated nucleus - polymorphonuclears

1. neutrophilic 56 -64%

2. eosinophilic 1-3%

3. basophilic 0,5-1%

• agranulocytes

-do not contain specific granules

-mononuclear – simple shape nucleus

4. monocytes 3 - 8%

5. lymphocytes 24 - 40%

differential white blood cell count (leukogram)

- examination of the % of individual types of leukocytes in %

- helps to make diagnosis - individual types of Le are involved in different functions

!!! in children – the most prevalent type of Le are lymphocytes

1 2

3

4

5