BLOOD PHYSIOLOGY

PIO 201
MONDAY 2-4 PM
 OUTLINE
• Composition and Functions of Blood
• Haemopoiesis and Erythropoiesis
• Haemostasis and Coagulation
• Blood Groups and Blood Transfusion
 OBJECTIVES
At the end of this class, you should be able
to:
• Identify the properties of blood
• Discuss the composition of blood
• List the functions of blood
• Discuss the formation of blood cells
 BLOOD
• A specialized connective tissue
• Made up of cellular elements and an extracellular matrix
• The human body needs blood to deliver nutrients to and
removes wastes from the trillion cells.
• The heart pumps blood throughout the body in a
network of blood vessels.
• These 3 components: heart, blood and blood vessels
make up the cardiovascular system.
 PROPERTIES OF BLOOD
❑ Color: Red pigment- Hemoglobin

❑ Amount : 8% of TBW

❑ pH: 7.35- 7.45

❑ Viscosity: 3-5x than water.

❑ Temperature: 38oC
 FUNCTIONS
❑ Transportation

❑ Defence

❑ Maintenance of homeostasis
 COMPOSITION
❑ Cellular elements a.k.a Formed elements 45%
▪ Red blood cells (RBCs), 99%
▪ White blood cells (WBCs)
▪ Platelets - cell fragments

❑ Extracellular matrix – Plasma 55%

▪ This fluid, which is mostly water
▪ suspends the formed elements for circulation throughout
the body within the cardiovascular system.
COMPOSITION OF BLOOD
Blood Composition
 Haematocrit is a test which measures the percentage of RBCs in a blood
sample.
The volume of erythrocytes after centrifugation is also commonly referred
to as packed cell volume.
 FORMED ELEMENTS
• Erythrocytes= red blood
cells (RBC)

• Leukocytes= white blood

cells (WBC)

• Thrombocytes= platelets
 PLASMA
❑ Straw colored liquid consist of 91-92% H20 and
dissolved solutes
❑ Solvent ability enables transport of many substances
❑ The major solutes in term of concentration is Na+
❑ It consist of other ions, organic molecules: metabolites,
hormones, antibodies and other proteins.
❑ The proteins consist 7-9% of the plasma: Albumins,
globulins, Fibrinogen
 PLASMA PROTEINS
❑ Albumin
▪ Most abundant
▪ Accounts for 54% of total plasma protein
▪ Produced by the liver
▪ Serve as binding protein to transport fatty acids and
steroid hormones
▪ Significant contributor of osmotic pressure of blood
▪ Maintain blood volume and pressure
 PLASMA PROTEINS
❑ Globulin
▪ Second most common
▪ 38% of total plasma proteins
▪ 3 subgroups: alpha, beta and gamma
▪ α&β produced in the liver
▪ transports ions, lipids and fat-soluble vitamins: A, D, E,
K
▪ Contribute to osmotic pressure
▪ γ produced by specialized B lymphocytes (plasma
cells)
▪ involved in immunity
 PLASMA PROTEINS
❑ Fibrinogen
▪ Least abundant
▪ 7% of total plasma proteins
▪ Produced in the liver
▪ Essential for blood clotting

• Other proteins are regulatory – hormones and

enzymes
• Plasma is a straw-colored clear liquid part of blood
while Serum is the clear straw-colored fluid that
oozes from blood clot. Serum = Plasma – Fibrinogen
 Other substances contained in the
plasma
❑ Contribute ~ 1% of total volume of plasma

▪ Electrolytes: Na+, K+, Ca2+

▪ Dissolved gases: O2, Co2, nitrogen

▪ Organic nutrients: vitamins, lipids, glucose, amino

acids,

▪ Metabolic wastes
COMPOSITON OF PLASMA
 Production of the Formed Elements
❑ The process of the blood production is hemopoiesis or
hematopoiesis.
❑ Most formed elements normally live only a few hours to
a few weeks.
❑ Thus, the body must form new blood cells and platelets
quickly and continuously.
❑ The body typically replaces plasma within 24 hours, but
it takes 4-6 weeks to replace the blood cells.
❑ This restricts the frequency with which donors can
contribute their blood.
 Sites of Hemopoiesis
Stages Sites
Embryonic Yolk sac
development
Liver, spleen, lymphatic tissue,
Red bone marrow
Birth CT within the spaces of spongy bone tissue
Children Medullary cavity of long bones
Adults Cranial and pelvic bones, Vertebrae,
Sternum, Proximal epiphyses of femur and
humerus
Liver and Spleen (extramedullary
hemopoiesis)
 Hematopoiesis
❑ All formed elements arise from stem cells of the red
bone marrow.

❑ The stem cells undergo cellular division to give rise to

new daughter cells.

❑ One of these daughter cells remains a stem cell and the

other differentiates into one of any number of diverse
cell types.
 Hematopoiesis
❑ Hemopoietic stem cell (hemocytoblast), where are all the
formed elements originate from.

❑ One daughter cell remains a hemopoietic stem cell,

allowing hemopoiesis to continue.

❑ The other daughter cell becomes either of two types of

more specialized stem cells.
▪ Lymphoid stem cells or Myeloid stem cells
 Hematopoiesis
❑ Myeloid cells differentiate into progenitor cells which give
rise to more specific elements. colony forming units eg
CFU-E, CFU-Meg and CFU-GM.

❑ The next generation are the precursor cells, ‘’blasts”

which develop into actual formed elements eg
monoblasts- monocyte, proerythroblasts- erythrocyte.
 Hemopoietic Growth Factors
❑ Hemopoiesis begins when the hemopoietic stem cell is
exposed to appropriate chemical stimuli, hemopoietic
growth factors, which prompt it to divide and
differentiate.
▪ Erythropoietin (EPO)
▪ Thrombopoietin
▪ Cytokines
 Hemopoietic Growth Factors
❑ Erythropoietin (EPO)
▪ A glycoprotein hormone
▪ secreted by the kidneys in response to low oxygen
levels.
▪ prompts the production of erythrocytes.

❑ Thrombopoietin
▪ A glycoprotein hormone,
▪ produced by the liver and kidneys.
▪ triggers the development of megakaryocytes into
platelets.
 Cytokines
• glycoproteins
• secreted by a wide variety of cells, including red bone
marrow, leukocytes, macrophages etc.
• Act locally as autocrine or paracrine factors, stimulating
the proliferation of progenitor cells and helping to
stimulate both nonspecific and specific resistance to
disease.
• There are two major subtypes: colony-stimulating factors
and interleukins.
 References
• https://open.oregonstate.education/aandp/c
hapter/18-0-introduction/
• K Sembulingam- Essentials of Medical
Physiology