This document provides an overview of blood physiology for midwifery students. It discusses the major functions of blood including distribution of oxygen, nutrients, waste removal, and temperature regulation. The key components of blood - plasma, red blood cells, white blood cells, and platelets - are described along with their production and roles in clotting and immunity. Hematopoiesis, the production of blood cells in the bone marrow, is regulated by various hormones and growth factors.

1. March 19, 2017 1
Blood physiology
For Bsc Midwifery students
Baye Dagnew (MSc)
GCMHS, 2016/17
Email-bayedagnew7@gmail.com

2. Objectives
At the end of this session, students should be able to:
• Mention major functions of blood
• Describe components of blood
• Discuss on how blood cells are produced and
developed
• Describe blood grouping and transfusion
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3. Brain storm
Question: Why blood is red?
Answer: because it contains hemoglobin which is iron rich
pigment.
Question: What does hemoglobin do?
Answer: Hemoglobin picks up the oxygen molecules and
drops off CO2
Question: What do platelets do?
Answer: Platelets clot the blood during injury of blood
vessels
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4. Introduction to blood
• Blood is the only fluid
circulating connective tissue.
• Hematology: study of blood
and blood related disorders
• Blood is sometimes referred to
as “the river of life,”
– Blood is pumped from heart
through blood vessels
collectively known as
circulatory system.
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5. Introduction to blood…
• Infants & children have comparably lower volumes of
blood, proportionate to their smaller size.
• Volume of blood in an individual fluctuates.
– During dehydration, for example while running a
marathon, blood volume decreases.
– Blood volume increases in circumstances such as
pregnancy, when the mother’s blood needs to carry
extra oxygen and nutrients to the baby.
March 19, 2017 5

6. Introduction to blood…
• Blood leaves heart via arteries that branch repeatedly until they
become capillaries.
– O2 & nutrients diffuse across capillary walls & enter tissues
– CO2 & wastes move from tissues into the blood
• O2 deficient blood leaves capillaries and flows via veins to heart.
• This blood flows to lungs where it releases CO2 & picks up O2
• The oxygen rich blood returns to heart.
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7. Physical Characteristics of blood
• Viscous fluid connective tissue
• Density- Heavier and thicker than water.
• Color varies from bright red[oxygen-rich] to dark red
[oxygen-poor]
• pH is 7.35–7.45 and its salt content is 0.9%.
• Temperature is 38C, slightly higher than “normal”
body temperature.
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8. How much blood is in the human body?
• In average person blood
accounts for approximately
8% of body weight
• So, average person of 70kg
will have
8×70
100
=5.4L of
blood volume
• Average volume of blood is
5–6 L for males, and 4–5 L
for females
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9. Why blood volume is higher in males than females ?
Possible reasons:
1. Androgen- it stimulates RBC production, and men have
higher androgen levels than women;
2. Menstruation- women of reproductive age have periodic
menstrual losses
3. Body fat- Hematocrit is inversely proportional to percent
body fat, which is higher in women than in men.
March 19, 2017 9

10. Functions of Blood
1. Distribution
Blood transports:
a) O2 from lungs and
nutrients from GIT
b) Metabolic wastes from
cells to lungs and kidneys
for elimination.
c) Hormones from endocrine
glands to target organs.
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11. Functions of Blood…
2. Regulation
Blood maintains:
– Body temperature by absorbing and distributing heat
– Normal pH in body tissues using buffer systems
– Adequate fluid volume in the circulatory system
3. Protection
• Blood prevents blood loss by:
– Activating plasma proteins and platelets
• Blood prevents infection by:
– Synthesizing and utilizing antibodies
– Activating WBCs to defend body against foreign
invaders
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12. Blood Components
Centrifugation is used to
separate blood cells and
plasma.
Three layers formed after
centrifugation
1. Upper suspension:
– Plasma (55%)
2. Middle layer
– Called Buffy coat
– WBC and Platelets
3. Lower portion :
– Reddish mass of RBC
settled at bottom of test
tube.
– ~45%
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Withdraw blood
and place in tube
1 2
Centrifuge
Plasma (55% of
whole blood)
For
med
ele
men
ts
Buffy coat:
leukocyctes
and platelets
(<1% of
whole
blood)
Erythrocytes
(45% of
whole
blood)

13. PLASMA
• Liquid portion, nonliving part of blood.
• It is intravascular component of ECF
• Blood plasma is composed of
1. Water: (~90%)
2. Organic constituents : (~9%) , mainly
plasma proteins
3. Inorganic constituents:
• electrolytes: (~1%)
4. Respiratory gases: o2 and C o2
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14. Principal plasma proteins
• Total principal plasma protein is about 6-8g/dl, aver=7 g/dl
• There are 3 principal plasma proteins
– Albumin=4 g/dl
– Globulin=2.7 g/dl
– Fibrinogen=0.3 g/dl
• Plasma proteins are synthesized by hepatocytes, lymphocytes,
platelets and endothelial cells
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15. Functions of plasma proteins
1. Maintaining colloid osmotic balance (albumins)
2. Transport of materials through blood (such as water,
blood cells ,products of digestion and hormones)
3. Antibodies (e.g. gamma globulins, immunoglobulin)
5. Clotting factors (e.g. fibrinogen)
6. Helps to regulate body temperature
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16. Hematopoiesis
• Production of blood cells is called Hematopoiesis or
Hemopoiesis.
• Blood cells begin their lives in bone marrow from single
type of cell called pluripotential hematopoietic stem cell
(PHSC)
• The intermediate stage cells become committed to a
particular line of cells called committed stem cells
• Different committed stem cells will produce colonies
of specific types of blood cells.
E.g. A committed stem cell that produces erythrocytes is
called a colony-forming unit–erythrocyte(CFU-E)
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17. Figure-- Formation of the multiple different blood cells from the
original pluripotent hematopoietic stem cell in the bone marrow.
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18. Haematopoiesis regulating factors
• Hemopoiesis is chemically regulated by
– Colony stimulating factors: GM-CSF,, M-CSF
– Interleukines (eg. IL-3)
– Platelet derived growth factor (PDGF)
– Thrombopoietic stimulating factor (TSF)
– Erythropoietin, GH, thyroid hormones (T3/T4),
androgen (Testosterone)
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19. Red blood cells (erythrocytes)
Shape and Size of RBC
• Greek erythros for "red" and kytos for "hollow
vessel", with -cyte translated as "cell" in
modern usage).
• Normal RBCs are annucleate, biconcave disks
• Have no mitochondria
• ATP is generated anaerobically , so erythrocytes do
not consume O2 they transport.
• Filled with hemoglobin (Hb), a protein
that functions in gas transport.
• Plasma membrane of RBCs is comprised of
flexible proteins
– Allow them to change shape as necessary
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20. RBC…
Concentration of RBC in Blood.
• In healthy person, the average number of RBCs per cubic
millimeter [(1 mm3 = 1 µl)]
• It is the most abundant human cell
• Major content of RBCs is Hb (97% )
20
Men= 5,200,000 ±300,000
Women= 4,700,000 ±300,000
March 19, 2017

21. RBC…H
• The percent (%) volume of packed RBC’s from whole blood is
called hematocrit (Hct)
– It accounts about;
• 42-48% (Males ), 38-43% (Females)
– Hct increases in dehydration
– Thus knowing Hct value is important in clinical practices
to diagnose diseases.
• Hemoglobin: Hb = 1/3 Hct
– Red protein containing iron, responsible for O2 transport
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22. Erythropoiesis
• Process of RBC production
• In early weeks of embryonic life primitive, nucleated
RBCs are produced in the yolk sac.
• During middle trimester of gestation
– The liver is the main organ for production of RBCs
– Spleen and lymph nodes are also involved.
• Starting from last month of gestation onwards and after
birth RBCs are produced exclusively in red bone marrow.
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23. 23March 19, 2017

24. Regulation of erythropoiesis
• Erythropoiesis is hormonally controlled.
• Hormones accelerating erythropoiesis:
– Erythropoietin from Juxta Glomerular( JG) -cells and
hepatocytes.
– GH, T3/T4, Androgens
– Intrinsic factor (IF) from parietal cells of stomach
• Liver plays a critical role in RBC formation as site of
globin synthesis, storage area of iron and vit-B12
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25. 25March 19, 2017

26. Hemoglobin (Hb)
• Normal concentration; 15 g/dl in Males and 14 g/dl in Females
• Composed of proteins called heme and globin
• Hb reversibly binds with oxygen and most oxygen in blood is
transported in combination with Hb
• Oxyhemoglobin: – hemoglobin bound to oxygen
• Deoxyhemoglobin –Hb after oxygen diffuses into tissues
• Carbaminohemoglobin – Hb bound to CO2
• Carboxyhemoglobin or carbon monoxyhemoglobin is a
compound of Hb with CO.
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27. Anemia
• Deficiency of Hb in blood, which can be caused by either
too few RBCs or too little Hb in the cells.
Types of Anemia
1. Deficiency anemia: caused by deficiency of vit-B12 ,
folic acid, Iron, proteins
2. Aplastic anemia: depression of bone marrow due to
irradiation, drugs and leukemia
3. Hemolytic anemia: prematurely ruptured erythrocytes or
formation of fragile RBCs due to sickle cell, transfusion
reaction, snake venoms, malaria, erythroblastosis fetalis
4. Bleeding (blood loss anemia or hemorrhagic anemia):
result of acute or chronic loss of blood
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28. Polycythemia: ↑RBCs count > 6 million/mm3 Or a
hematocrit of >55%.
Causes
1. Chronic hypoxia: -High altitude
-Heart failure
-Respiratory failure
2. Primary over activity of bone marrow
• Physiologic polycythemia - A common type of 20
polycythemia, occurs in natives who live at high
altitudes, where the atmospheric O2 is very low.
Management- phlebotomy
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29. Leukocytes (white blood cells)
• Normal WBC count: 5,000 – 11,000/mm3
Average:7000/mm3
• Leukopenia: ↓in WBC count
• Leukocytosis: ↑in WBC count
Function: defense/protection against disease
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30. Types of WBCs
Granular leukocytes
• Has granules in staining
– Eosinophils
– Basophils
– Neutrophils
Agranular leukocytes
• Lacks granule in staining
– Monocytes
– Lymphocytes
30
NB: granular vs. agranular
“Every Boy Needs Mommies Love!”
March 19, 2017

31. WBC differential count
1. Neutrophils: 50-74 ( 62%, 3000-7000/mm3
2. Lymphocytes: 20-40% (30%), 1500-3500/mm3
3. Monocytes: 2-8% (5.3%), 100-700/mm3
4. Eosinophils: 1-4% (2.3%), 100-440/mm3
5. Basophils: 0.3-0.5% (0.4%), 20-50/mm3
Relative Quantities- mnemonics
–“Never Let Monkeys Eat Bananas!”(
descending order in abundance)
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32. WBCs…
Neutrophils
– The most abundant WBCs
– Have multi-lobed nuclei (PMN)
– Phagocytic cells (ingest bacteria)
Eosinophils
– Increase in number during parasitic infection
(eosinophilia)
– Produce hydrolytic enzymes to kill big parasites
Monocytes
– They are highly phagocytic cells
– They are the largest WBCs
– They leave the circulation, enter tissue, and differentiate
into macrophages
32March 19, 2017

33. The tissue macrophage system (reticulo-endothelial system)
Monocytes are formed in the bone marrow
Enter the circulation
Leave the circulation & enter the tissue,
↑size, ↑lysosomal activities
Become tissue macrophages
Lungs Skin Liver Brain Bone Spleen,
Alveolar Histocytic Kupffer Microglial Osteoclasts lymph nodes
Macrophages cells cells cells Reticular cells
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34. Lymphocytes
• They are major soldiers in immune system battles.
• Most lymphocytes continually move among lymphoid tissues,
lymph, & blood, spending only a few hours at a time in blood.
Thus, only a small proportion of the total lymphocytes are
present in the blood at any given time.
• Three main types of lymphocytes are B cells, T cells, &
natural killer (NK) cells.
• B cells are particularly effective in destroying bacteria &
inactivating their toxins.
34March 19, 2017

35. Lymphocytes…
• T cells attack viruses, fungi, transplanted cells, cancer
cells, & some bacteria, and are responsible for transfusion
reactions, allergies, & the rejection of transplanted organs.
• Immune responses carried out by both B cells & T cells
help combat infection & provide protection against some
diseases.
• Natural killer cells attack a wide variety of infectious
microbes & certain spontaneously arising tumor cells.
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36. Lymphocytes…
• B-cells that bind with an antigen will subsequently
differentiate into Plasma cells & Memory cells
Plasma cells - begin to produce antibodies (up to
2,000 per second)
Memory cells - remain dormant until a person is
again exposed to the same antigen
36March 19, 2017

37. Platelets (thrombocytes)
 Don’t have nuclei
 Have contractile proteins (actin
and myosin)
 Normal platelet count:
• 150,000 – 300,000/mm3
(Av= 250,000/mm3)
• Thrombocytopenia: low
number of platelets
• Thrombocytosis: an increase in
the number of platelets
• Thrombasthenia: a decrease in
function of platelets
Function of platelets
1. Synthesize prostaglandins,
fibrin stabilizing factor,
serotonin and other chemicals.
2. Clotting mechanism by
forming temporary plug that
helps seal breaks in blood
vessels
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38. Genesis of Platelets (thrombocytopoisis)
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39. Hemostasis
• A series of reactions designed for stoppage of bleeding
• During hemostasis, three phases occur in rapid sequence
1. Vascular spasm
2. Platelet plug formation
3. Coagulation (blood clotting)
• Blood usually clots within 3 to 6 minutes
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40. 1. Vascular spasm
• Local vasoconstriction of ruptured blood vessel that
is caused by:
 Reflex sympathetic discharge (pain nerve
impulses)
 Local myogenic contraction of vascular wall
Importance:- blood flow is reduced.
N.B- for smaller vessels, constriction is the result of
thromboxane A2 released from platelets.
40March 19, 2017

41. 2. Platelet Plug Formation
• Is very effective in preventing blood loss in small vessels.
– Can stop blood loss completely if hole is not too large.
• Their granules contain chemicals (clotting factors, ADP,
ATP, Ca2+ & serotonin) those promote blood clotting.
• Normally, platelets do not stick to each other or to
endothelial lining of blood vessels
• Platelets have a short life span, just 5 to 9 days.
• Aged & dead platelets are removed by fixed macrophages
in spleen & liver.
41March 19, 2017

42. Platelet Plug Formation…
• Upon damage to blood vessel
endothelium (which exposes
collagen) platelets:
– Stick to exposed collagen
fibers and form platelet plug
– Release serotonin and ADP,
which attract additional
platelets
• Platelet plug is limited to the
immediate area of injury
42March 19, 2017

43. 3. Coagulation
• Set of reactions whereby blood is transformed from
liquid to gel (clot).
• It is slow but has long lasting effect
• Formed primarily of fibrin threads but also blood cells ,
platelets.
• Coagulation follows intrinsic and extrinsic pathways
• Vitamin-K: used for synthesis of clotting factors
• Blood clotting factors are produced by
Liver, Platelets and endothelial cells
43March 19, 2017

44. Stages of Blood Coagulation
• Coagulation undergoes three steps of reactions:
1. Formation of Prothrombin activators through
– The intrinsic pathway
– The extrinsic pathways
2. Conversion of Prothrombin into thrombin by action
of Prothrombin activators (prothrombinase)
3. Conversion of fibrinogen into fibrin thread by action
of thrombin
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45. 45March 19, 2017

46. Human blood groups
• Grouping depends on presence of antigens, agglutinogens
on surface of RBCs
• RBCs contain glycoproteins on their surface with
antigenic effect
• Major blood groups are
ABO blood group and Rh system
Importance of Knowing Blood groups:
1. Very essential medically, socially & Judicially.
• Socially: being member of blood donor's club
• Judicially: to resolve medicolegal cases
2. Among the couple helps to prevent complications due to
Rh incompatibility & save child from hemolysis.
46March 19, 2017

47. ABO Blood Group
• Based on ± of two agglutinogen (A and B), ABO blood
grouping can be classified into 4 types
1. Type-A: antigen A is present on RBC.
2. Type–B: antigen B on RBCs.
3. Type–AB: both A & B exist
4. Type–O: neither agglutinogen A nor B are present.
• Most Ethiopians have group “o” blood
O= 47%, A= 28%, B= 20%, AB= 5%, Rh+= 97%
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48. 48March 19, 2017

49. 49March 19, 2017

50. Rh Factor
 First worked out on Rhesus monkey to hence Rh-system
 The presence of agglutinogen D on RBCs: Rh+
 Missing agglutinogen D on RBCs: Rh-
 Agglutinin (anti-D antibodies) are not normally present in
serum but produced 20 to exposure of Rh- blood to Rh+ blood
(antigen-D)
NB- Serum is blood plasma without fibrinogen (clotting proteins)
50March 19, 2017

51. Rh Factor…
Normally, blood plasma does not contain anti-Rh
antibodies.
If Rh- person receives Rh+ blood transfusion, immune
system starts to make anti-Rh antibodies that will remain in
blood.
If second transfusion of Rh+ blood is given later,
previously formed anti-Rh antibodies will cause
agglutination & hemolysis of RBCs in donated blood
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52. March 19, 2017 52

53. Erythroblastosis Fetalis
 The most common problem with Rh incompatibility, hemolytic
disease of newborn (HDNB), may arise during pregnancy.
 Occurs when Rh- mother marries Rh+ father and conceives Rh+
fetus
 During delivery, there could be leakage of Rh+ blood from fetus to
circulation of mother.
 Rh+ blood induces production of anti-D antibodies in the circulation
of mother.
 During 2nd conception of Rh+ fetus, anti-D antibodies cross the
placenta and attack RBCs of fetus
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54. 54March 19, 2017

55. March 19, 2017 55

56. Blood transfusion
 Transfusion is transfer of whole blood or blood components
(RBCs only or blood plasma only) into bloodstream or
directly into red bone marrow.
 Transfusion is most often given to alleviate anemia,  blood
volume (e.g., after severe hemorrhage).
 Whole blood transfusion is used:
– When blood loss is substantial
– In treating thrombocytopenia
• Packed red cells (cells with plasma removed) are used to treat
anemia
56March 19, 2017

57. Blood transfusion compatibility
57
AB is universal recipient
O is universal donor
March 19, 2017

58. 58March 19, 2017