Dr Kola Gobir
BLOOD AND BODY FLUIDS (PART 1)
Topics
1. Similarities and differences between blood, plasma and serum, and the use
of serum in clinical diagnosis
2. Characteristics, composition and function of blood.
3. Types of cells in the blood, RBC, WBC and thrombocytes.
4. Blood electrolytes and plasma buffer system.
5. Regulation of PH, acid-base balance.
BLOOD:
What is blood?
Blood, which can also be referred to as fluid connective tissue, it is a
specialized body fluid that circulates in the heart, arteries, capillaries and veins, of
a vertebrate animal, carrying nourishment and oxygen to and bring away waste
product from all part of the body.
It is made up of liquid and solid part, the liquid part is called plasma, and is
made up of H2O, salts and protein. Over half of blood is plasma (55%). The solid
part is RBC (Red Blood Cells), White Blood Cells(WBC) and platelets.
PLASMA:
A light Amber-coloured liquid component of blood in which blood cells are
absent, but in which blood cells are absent, but which contain protein and other
constituents of whole blood.
Plasma constituents:
1. H2O content is 92%, PH7.4 and osmolality 290mosm/kg
2. Organic constituents comprise (a) plasma proteins such as albumin, globulins
and fibrinogen, and (B) food substance and waste product in transit, enzymes
and hormones.
3. Inorganic constituents, include electrolytes
4. Gases in solution include oxygen, carbondioxide and nitrogen.
5. The volume and composition of blood are maintained constant by various
homeostatic mechanism.
Functions of plasma
1.
2.
3.
4.
Redistributing H2O in the body
Delivery of hormones, nutrients and protein to part of the boyd.
Plasma support blood vessels form collapsing or clogging
Plasma also maintain blood pressure and circulation
Plasmapheresis:- a method of removing blood plasma from the body by
withdrawing blood, separating it into plasma and cells, and transfusing the cells
back into the blood stream. It is performed especially to remove antibodies in
treating autoimmune conditions.
SERUM
Blood plasma without clotting factors. If the blood is not centrifuged, but left to
stand without an anticoagulant, clotting takes place leaving a clear fluid free from
fibrinogen which is known as serum.
Serum includes all proteins not used in blood clotting, all electrolytes,
antibodies, hormones and exogenous substance e.g drugs or microorganisms.
Clinical use of Blood Serum
 Serum is used in determining the therapeutic index of a drug candidate in a
clinical trial.
 Serum is also used in protein electrophoresis because of absence of
fibrinogen
 Biopharmaceuticals: serum from covalescent patient from infectious
diseases, can be used for vaccine manufacturing
 Culture media: serum is rich in growth factors, hence use in a growth medium
in eukaryotic cells culture.
 It is used in treatment e.g snake bite (as anti-snake venom)
 In providing immunity
Serum separation
1. Centrifugation
2. Physical- left to stand without anti-coagulants
Similarities and differences between serum and plasma
Similarities
 Both serum and plasma comes from the liquid part of the blood once the
cells are removed.
Differences
1. Serum is the liquid that remain after blood has clot; WHILE plasma is the
liquid that remain when clotting is prevented with the addition of anticoagulants
2. Serum comprises electrolytes, hormones, antigens, antibodies and protein
like globulins and albumins; WHILE plasma include blood cells, glucose, salts,
protein, lipids, H2O and clotting factor
Characteristics, composition and function of blood
CHARACTERISTICS OF BLOOD
 The blood is an opaque red fluid, freely flowing but denser and more viscous
than water.
 The characteristics colour is imparted by haemoglobin, a unique ironcontainig protein. Haemoglobin brightens in colour when saturated with O2
(oxyhaemoglobin) and darkens when O2 is removed (deoxyhaemoglobin).
 PH: - 7.35-7.45, slightly alkaline
 Viscosity: - about 5 times of H2O
 Temperature – 380c
 Volume – approximately 5 litres (8% of body weight size of 6kg individual)
COMPOSITION
The blood is made up of liquid and solid part. The liquid part is called plasma, which
consist of H2O, salts and protein, and antibodies.
When a sample of blood is centrifuged, the red cells settle at the bottom,
giving a packed cell volume (PCV) of about 45% of total volume. A thin creamy layer
known as the buffy coat made up of white cells and platelets atops the red cells,
separating them from the clear straw-coloured (i.e. pale yellow) supernatant which
is called plasma, that constitutes about 55% of the blood volume. The blood cells
are often collectively referred to as the formed elements. If the blood is not
centrifuged, but left to stand without an anticoagulant, clotting takes place leaving
a clear fluid free from fibrinogen known as serum.
Separation of cells and plasma in centrifuged blood
FUNCTIONS OF BLOOD
1. Transport function: - blood is the medium for the transport of substances
throughout the body. H2O soluble substances are transported bound to
plasma protein, which make them water-soluble. The transport can be
categorized as follows:
a. Nutrients absorbed from intestine and transported to various tissue
for utilization and storage.
b. Waste products such as urea, uric acid and creatinine from the tissue
to the kidney for excretion
c. Respiratory gases: - O2 from the lungs to the tissue, and CO2 from the
tissue to the lungs for excretion. This is the main function of Red blood
cells
d. Hormones are transported from the secreting endocrine glands to
their targeted organs
2.
3.
4.
5.
e. Calories from actively metabolizing tissue such as liver and muscles to
cooler parts of the body, especially the skin and hypothalamus, which
assist in temperature regulation
f. Miscellaneous substances either produced in the body e.g. bile salts
(which are secreted into the bile and reabsorbed from the guts) or
substances introduced into the body such as drugs and toxins
Buffer role in maintaining the PH of body fluids
 The plasma contains 3 important buffer systems which (combine with
intracellular buffers) serve as the first line of defense for constant PH
maintenance in the body fluid. The buffers are: - bicarbonate, phosphate
and protein buffer
Defense of the body: the white blood cells protect against foreign bodies
such as bacteria, viruses and various particulate matter by destroying them
through phagocytosis or immunological attack.
Oncotic effect of plasma protein: the osmotic pressure of plasma protein
helps to regulate the exchange of fluids between capillaries and the tissues
(Starling’s Principle), and the viscosity due to the cells and protein which
offer some resistance to flow, the heart in the creation of a pressure head.
Maintenance of vascular integrity: when a blood vessel is ruptured, blood
coagulation sets in to seal the wound and enable healing to take place.
Types of cells in the blood.
The blood is made up of liquid and solid part, the liquid part is called Plasma
while the solid parts consists of
(a) Red blood cells (RBC)
(b) White blood cells (WBC)
(c) Platelets (Thrombocytes)
Red blood cells or Erythrocytes
These are the cellular components of blood that carries oxygen from the
lungs to the tissues, and carries CO2 from the tissues to the lungs.
RBC are far the most abundant type of blood cells; 99% of all blood cells are
erythrocytes.
Structures/Features






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

They are biconcave discs
They have no nucleus
The diameter is about 7µm
No intracellular organelles
Consist of Haemoglobin
Small and flexible
Flat disk or doughnut shape
The life span in the circulation is about 120days
Approximately 30 trillion (1014) in the body
Production and Development (Erythropoiesis)
Because RBC have no nucleus, erythrocyte cannot divide and so need to be
continually replaced by new cells from the red bone marrow. Red bone marrow
presents in the ends of long bones, flat and irregular bones. The process of
erythrocytes development from stem cells takes about 7days and its called
erythropoiesis. The immature cells are released as reticulocytes, and mature into
erythrocytes in the blood stream over a few days within the circulation, in which,
during this time, lose their nucleus and therefore become incapable of division.
Both vitamin B12 and folic acid are required for red blood cell synthesis. They
are absorbed in the small intestine.
Committed Stem Cells
Pronormoblast
Basophilic normoblast (nucleoli gone, nucleus condensing, cytoplasm blue)
Polychromatophilic normoblast (Hb begins to appear, makes cytoplasm blue and
red, nucleus condensing further)
Orthochromatic normoblast (mitosis stops, nucleus pyknotic, full Hb, cytoplasm
red)
Reticulocyte (Nucleus lost, reticulum due to RNA enter circulation after 1 or 2
days)
Mature erythrocyte (RNA and mitochondrion lost)
WHITE BLOOD CELLS: mobile units of the body’s protective system. Normal count
4,000-11,000/µl.
FUNCTIONS
1. By actually destroying invading bacteria or viruses by phagocytosis.
2. By forming antibodies and synthesis lymphocytes – destruction/inactivation
of the offender
Types of WBC
There are 6 types
 (multiple nuclei) – polymorphonuclear leukocytes/granulocytes
 Neutrophils (50-70%)
 Basophils (<1%)
 Eosinophils(1-4%)
 Monocytes (2-8%)
 Lymphocytes (20-40%)
ELECTROLYTES AND PLASMA BUFFERS, PH REGULATION, ACID-BASE BALANCE
The body is made up of fluids and solid. The principal component of the fluid
is water which makes up 45-75% of the total body weight depending on the age,
the amount of fat and adipose tissue present. The fluid component is divided briefly
into intracellular fluid, which makes up 2/3 of the total body fluid and also divided
into extracellular fluid which constitutes 1/3 of the total body fluid. The ECF
include: the interstitial, plasma, lymph, CSF, fluid in the GIT, the synovial fluid,
pleural, pericardial, peritoneal, glomerular filtration.
Fluid balance means that the various body compartments contains the
required amount of water and electrolytes.
Electrolytes are those substances that when dissolved in water are capable
of carrying an electric current. Electrolytes in body fluids are inorganic substances
that dissociates into ions (electrically charged atoms and radicals). If it is
appositively charged ion, they are called cations, negatively charged ions are known
as anions.
Electrolytes plays a greater role in osmosis than non-electrolytes e.g. of
electrolytes in body fluid are Na+, K+, Ca++, Mg++, Cl-, HCO3-, phosphate, sulphate.
Na+ is the most abundant extracellular cation and it plays important role in impulse
transmission and fluid and electrolyte balance, it’s level is controlled by
aldosterone. Level of sodium: 145mEq/L.
Mg2+: is intracellular cation and they act as a co-factor in several enzymatic
reactions in the body.
Cl- is a major extracellular anion and it plays a major role in regulating muscle
contractions and formation of HCl acid. Their level is also under the control of
aldosterone
K+ is the most abundant intracellular cation. It plays a significant role in the
maintenance of fluid volume, impulse conduction, muscle contraction and
formation of HCl acid. Blood level is under the control of aldosterone.
HCO3-: most abundant anion in the ECF and most important buffer in plasma
Ca2+: one of the most abundant mineral in the body and it salts as structural
component of teeth and the bones. It is principally and ECF cation and plays highly
significant role in blood clotting, contraction of muscles and neurotransmitter
release. It’s blood level are under the control of parathyroid hormone and
calcitonin
Phosphate are principally intracellular anion and they are important component of
bones and teeth. They are important in the synthesis of nucleic acid ATP and buffer
mechanisms. They are also under the control of parathyroid hormone and
calcitonin
ACID – BASE BALANCE
Homeostasis is the process of maintenance of the internal body
environment. Metabolic processes in the body, leads to the production of H+ which
if left to accumulate would be injurious to the body e.g. of the metabolism is
anaerobic metabolism of carbohydrate and fatty acid. The body has a number of
ways to remove the H+ produced to provide a conducive environment for cellular
processes to continue.
The body enzymatic processes require a stable pH in order to carry out its
activities properly. The acid base balance is targeted at controlling the H+ of the
body fluids and maintaining it at 7.35-7.45 via
1. Exchange of CO2
2. Kidney excretion of H+
3. Absorption of HCO3Thus a form of buffer system is put in place to achieve this pupose.
BUFFERING: is a process by which a strong acid or base is replaced by a weaker one
with consequent reduction in the number of free hydrogen. The essence of a buffer
is to mop up H+ and produce a minimal change in pH. Buffers generally resist
changes in pH by either reacting with H+ to wade off it’s effect
H+Cl- + NaHCO3
H2CO3 + NaCl
Uses of buffer solution




Fermentation
Dyeing fabrics
Manufacturing
Personal hygiene and cosmetics product.
Buffer application
 Maintenance of life
 Biochemical Assays – enzyme activities depend on pH
 In the textile industry
 In laundry and detergent
Acid is a compound that dissociation in an aqueous solution to produce H+. e.g HCl
H+ + Cl
HCl
Base is a substance that is capable of accepting H+
Buffers: up to 5 buffers in the body
Buffer pairs
1.
2.
3.
4.
5.
HCO3-/H2CO3
Protein/Protein
Hb-/HHb
NH3-/NH4
NaHPO4-/NaH2PO4
pH: is a measure of hydrogen activity. It is a negative log of H+ concentration in
millimoles/litre
pH = -log[H] in mmol/l
pH of blood = 7.35-7.45, it is kept within this range by buffering mechanism,
but if pH is less than 7.35 is acidosis, pH>7.45=alkalosis
H+ conc in the blood
= 35 to 45 mMol/L
PCO2
= 35-45mmHg
HCO3
= 24-32mmol/L
HENDERSON-HASSELBACH EQUATION: this equation expresses the relationship
between the pH and buffer pair
pH = PKa + Log [conjugate base]
[Acid]
In a bicarbonate buffer
CO2 + H2O
H2CO3
H + HCO3-
H2CO3 is in equilibrium with dissolved CO2 and so can be inserted into the equation
in place of H2CO3 which cannot be measured directly. Carbonic acid is determined
by the partial pressure of CO2
Given by the H & H equation, the pH of the blood depends on
1. Partial pressure of carbondioxide i.e. PCO2; and PCO2 is determined by the
depth of respiration.
pH α 1/PCO2
Hypoventilation
Hyperventilation: PCO2
pH
PCO2 of the venous blood is higher than that of the arterial blood. Similarly, the pH
on the right side of the heart is lower than that of the left side
2.
Carbonic acid: this is determined by the kidneys
H2CO3 retention
pH
H2CO3 excretion
pH
Anion gap: this is the difference between the measured cation (Na+ and K+) and
measured anion (Cl- and HCO3-); and is normally between 15-20mMol/L; 816mEq(12±mEq)
Anion gap increases when unmeasured anions such as phosphate and sulphate
increases in the blood and bicarbonate falls as in acidosis. The opposite occurs in
metabolic alkalosis
Anion gap: Na+ + K+
Cl- + HCO3-
Unmeasured anion: SO42-, PO32Unmeasured cation: Ca2+, Mg2+
Increased anion gap is seen in the following cases:
1.
2.
3.
4.
When excess methanol is ingested
Uraemia
Lactic acidosis
Paraldehyde
5.
6.
7.
8.
Ethanol
Aspirin
Starvation
Diabetic ketoacidosis (DKA)
Decreased anion gap
1.
2.
3.
4.
Increase K+
Increase Ca2+
Increase Mg2+
Decrease albumin
Abnormalities of Acid-Base balance: could either be respiratory or metabolic
Respiratory acidosis
Metabolic acidosis
Respiratory alkalosis
Metabolic alkalosis
In respiratory acidosis/alkalosis, the primary abnormality is with the respiration i.e
partial pressure of CO2 control.
In metabolic acidosis/alkalosis, the primary abnormality is not respiratory in origin
 Respiratory acidosis: this occurs when the blood pH falls as a result of
decrease respiration. This is seen in (1). Respiratory depression e.g. excessive
sedation, (2) Obstructive airway disease e.g include chronic bronchitis,
emphysema, severe asthma, pulmonary oedema; (3) chest infection e.g
bronchopneumonia; (4) CNS depression e.g anaesthetic medications or
opiates e.g morphine (5) CNS disease e.g stroke, cardiovascular accident,
trauma to the head.
Respiratory acidosis is characterized by increase in PCO2 due to CO2
retention, the pH will fall.
ABG picture
o Increase PCO2
o Decrease Ph
o HCO3- normal
Compensation: the kidney then preserve bicarbonate
 Metabolic acidosis: this occurs due to excessive amount of acidic substance
released into the blood. It is characterized by low level of bicarbonate in the
blood and excess production of H+ and organic acids during metabolism and
also occurs when excess intake of acids and they accumulate in the body
resulting in metabolic acidosis
Causes
1. Increase or excess H+ production e.g ketoacidosis in uncontrolled diabetes
mellitus, starvation, lactic acidosis, shock and salicyalate poisoning
2. Failure to excrete H+ e.g acute or chronic renal failure
3. Loss of bicarbonate from GIT in severe diarrhea, pancreatic fistula
4. Loss of bicarbonate in urine e.g uteroenterostomy or proximal renal tubular
acidosis
ABG picture
o Decrease in HCO3o Increase in H+
o Decrease in Ph
Compensation: Hyperventilation of RS. Increased breathing to reduce the
amount of dissolved CO2 in the blood
 Respiratory alkalosis: this occurs as a result of excessive breathing. It is a
condition in which there is low CO2 in the blood due to excess removal
through the lungs or through hyperventilation. Because there is low CO2 it is
not enough to react with water to form carbonic acid
Causes
1. Hysterical overbreathing i.e voluntary hyperventilation, excessive artificial
respiration, early phase of exercise, high altitude
2. Stimulation of the respiratory centers e.g. pain, fever, hypoxia
3. Increase intra-cranial pressure or brain stem lesion
ABG picture
o Increase pH
o Decrease PCO2
Compensation: kidney retains the H, increase excretion of HCO3, Cl- and
lactate shift from ICF to ECF
 Metabolic alkalosis: this occurs due to excessive amount of alkaine
substances. In this condition, there is excessive removal of H+ through the
kidney or excess intake of alkaline salt, hence the bicarbonate level is high
Causes
1. Ingestion of large amount of bicarbonate to treat indigestion
2. Loss of unbuffered H+ e.g Conn’s & Cushing’s syndrome
3. Loss of H+ from the GIT e.g prolonged vomiting, use NG tube, pyloric
stenosis
4. Loss of H+ in urine e.g Thiazide diuretic
ABG picture
o Increase in pH
o Increase in HCO3o Decrease in H+
Compensation: Hyperventilation; kidney excrete bicarbonate
 Mixed acid base disturbance: e.g metabolic acidosis + metabolic alkalosis +
respiratory alkalosis can occur in a patient presenting with vomiting
(metabolic alkalosis), dehydration (metabolic acidosis) and sepsis
(respiratory alkalosis)
Acid-base balance diagnosis: include
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To check the blood ph
Arterial blood gas
Urinalysis; glucose & ketone
Renal function test: electrolytes check, urea, creatinine
Treatment
1.
2.
3.
4.
Give a supplemental oxygen if the cause is respiratory
Volume replacement if hypovolemic
Dextrose infusion, if starving
Correction of electrolyte derangement especially K+ and Na+ e.g using
Ringer’s lactate
5. Dialysis may be necessary in hyperkalemia
6. Treat the primary cause