BIOL 2304
Blood
The Circulatory System
Cardiovascular System – an enclosed muscular system composed of the heart and
blood vessels that pump blood throughout the body
Blood
Heart
Blood vessels
Function:
Supply body tissues with oxygen and nutrients
Remove waste from body tissues
Deliver hormones to target organs
Regulate body temperature
Blood
Composed of liquid and cellular portions
Plasma:
Water
Proteins (ie: hormones)
Electrolytes (ions)
Formed elements – cellular portion of blood
Red blood cells (Erythrocytes)
White blood cells (Leukocytes)
Granulocytes
Agranulocytes
Platelets (Thrombocytes)
Blood
Plasma – 55% of blood
RBCs – 45% of blood (Hematocrit)
Hematocrit – The ratio of the volume of red
blood cells to the total volume of blood
WBC – <1% of blood
Platelets – <1% of blood
Plasma Composition
90% Water
Transport medium
Carries heat
7% Plasma proteins
54% Albumins – contribute to osmotic pressure
38% Globulins – clotting factors, antibodies
7% Fibrinogen – inactive precursor for fibrin
Electrolytes
Cations and anions
Nutrients, wastes, gases, hormones
Transported in blood
Erythrocytes (RBCs)
Erythrocytes – Red blood cells (RBCs)
Characteristics of RBCs:
Biconcave discs
Provides larger surface area for diffusion of O2 across the
membrane
Thinness of cell enables O2 to diffuse rapidly between the
exterior and innermost regions of the cell
Flexible membrane
Allows RBCs to travel through narrow capillaries without
rupturing in the process
Hemoglobin
Hemoglobin – Iron containing pigment found only in RBCs
Consists of 2 parts:
Globin portion
Protein composed of four highly folded polypeptide chains
Heme groups
Four iron-containing nonprotein groups
Each is bound to one of the polypeptides
Formation dependent upon Vitamin B12
Leukocytes (WBCs)
Leukocytes – White blood cells (WBCs)
Naturally colorless; nuclei and granules stain varying degrees of red, blue, or purple
Larger than RBCs
Provide immunity and defense-- protect body from microorganisms and disease
Two general classifications:
Granulocytes – contain granules within cytoplasm that absorb staining pigment
Agranulocytes – do not contain prominent granules
Five major circulating leukocytes
Neutrophils (granulocyte)
Eosinophils (granulocyte)
Basophils (granulocyte)
Monocytes (agranulocyte)
Lymphocytes (agranulocyte)
A mnemonic device for remembering the order of leukocytes (WBCs) from most common to least common
Neutrophils
Lymphocytes
Monocytes
Eosinophils
Basophils
Never
Let
Monkeys
Eat
Bananas
60-70%
20-25%
3-8%
2-4%
0.5-1%
Leukocytes – Granulocytes:
Neutrophils – 60-70%
Most numerous WBC
Phagocytize and destroy bacteria
Nucleus has two to six lobes
Granules pick up acidic and basic stains
Eosinophils – 2-4%
Play roles in ending allergic reactions, parasitic infections
Basophils – 0.5-1%
Nucleus is usually bi-lobed
Granules secrete histamines
Function in inflammation mediation
Similar in function to mast cells
Leukocytes – Agranulocytes:
Lymphocytes – 20-25%
The most important cells of the immune system
Large nucleus stains dark purple
Effective in fighting infectious organisms
Act against a specific foreign molecule (antigen)
Monocytes – 3-8%
The largest leukocytes
Nucleus is kidney-shaped
Transform into macrophages (phagocytic cells)
Leukocytes
Thrombocytes (Platelets)
Cell fragments from megakaryocytes
Lack nuclei
Have organelles and cytosolic enzymes for generating energy
and synthesizing secretory products
Involved in blood clotting (thrombosis)
Hematopoiesis (aka Hemopoiesis)
Hematopoiesis – the formation of blood cells
All blood cells originate in bone marrow
All originate from one cell type
Blood stem cell (pluripotent hematopoietic stem cell) which differentiate into either:
Lymphoid stem cells
Give rise to lymphocytes
OR Myeloid stem cells
Give rise to all other blood cells