Blood Physiology-Lecture 4
Blood Physiology-Lecture 4
Blood Physiology-Lecture 4
Lecture 4: Blood
Contents:
1. Composition and Functions of Blood
2. Developmental Aspects of Blood
3. Hemostasis
4. Blood Groups and Transfusions
Blood
Blood Composition and Functions of Blood
Objectives:
•Describe the composition and volume of whole
blood.
•Describe the composition of plasma, and discuss its
importance in the body.
Blood Composition and Functions of Blood
• The only fluid tissue in the human body
• Classified as a connective tissue
• Components of blood
A. Living cells
• Formed elements
B. Non-living matrix
• Plasma
• If blood is centrifuged
– Erythrocytes sink to the bottom (45 percent of
blood, a percentage known as the hematocrit)
– Buffy coat contains leukocytes and platelets (less
than 1 percent of blood)
• Buffy coat is a thin, whitish layer between the
erythrocytes and plasma
– Plasma rises to the top (55 percent of blood)
Physical Characteristics of Blood:
• Color range
– Oxygen-rich blood is scarlet red
– Oxygen-poor blood is dull red
• pH must remain between 7.35–7.45
• Blood temperature is slightly higher than
body temperature at 38°C (100.4°F).
• In a healthy man, blood volume is about 5–6
liters or about 6 quarts
• Blood makes up 8 percent of body weight
Blood Plasma:
• Composed of approximately 90 percent water
• Includes many dissolved substances
– Nutrients
– Salts (electrolytes)
– Respiratory gases
– Hormones
– Plasma proteins
– Waste products
Blood Plasma:
• Plasma proteins:
– Most abundant solutes in plasma
– Most plasma proteins are made by liver
– Various plasma proteins include
• Albumin—regulates osmotic pressure
• Clotting proteins—help to stem blood loss when a
blood vessel is injured
• Antibodies—help protect the body from pathogens
Blood Plasma:
• Acidosis
– Blood becomes too acidic
• Alkalosis
– Blood becomes too basic
• In each scenario, the respiratory system and kidneys
help restore blood pH to normal
Formed Elements:
a. Erythrocytes
– Red blood cells (RBCs)
b. Leukocytes
– White blood cells (WBCs)
c. Platelets
– Cell fragments
Formed Elements:
a. Erythrocytes (red blood cells or RBCs):
– Main function is to carry oxygen
– Anatomy of circulating erythrocytes
• Biconcave disks
• Essentially bags of hemoglobin
• Anucleate (no nucleus)
• Contain very few organelles
Hematopoiesis
Objectives:
•Explain the role of the hemocytoblast.
Blood Hematopoiesis
Objectives:
•Describe the blood-clotting process.
• Name some factors that may inhibit or enhance the
blood-clotting process.
Blood
Hemostasis
Platelet plug formation
– Collagen fibers are exposed by a break in a blood
vessel
– Platelets become “sticky” and cling to fibers
– Anchored platelets release chemicals to attract
more platelets
– Platelets pile up to form a platelet plug
Objectives:
•Describe the ABO and Rh blood groups.
•Explain the basis for a transfusion reaction.
Blood
Blood Groups and Transfusions
B B Anti-A B, O
A A Anti-B A, O