Exercise 38
The Lymphatic System
and Immune Response
Lymphatic System




Lymphatic vessels
Lymphatic tissues
 Tonsils
Primary lymphatic organs
 Thymus and Bone marrow
Secondary lymphatic organs
 Lymph nodes, spleen
Lymphatic System
Lymphatic System


Lymph
 Fluid lost from the capillaries
 Edema
Functions of the lymphatic system:
 Transport lymph to the blood vessels
 Protects the body
Lymphatic vessels




Lymphatic capillaries
Lymphatic collecting vessels
Lymphatic trunk
Right lymphatic duct - drains lymph
from:
 Head right upper extremity
 Right thorax
 Drains into right subclavian vein
Lymphatic vessels



Thoracic duct – drains lymph from:
 Rest of the body
 Drains into left subclavian vein
Cisterna chyli
Characteristic of the lymphatic vessels
 Walls with 3 tunics
 Presence of valves
 Presence of abundant anastomoses
Lymphatic vessels
Primary lymphoid organs


Bone marrow
 Contain the stem cell that will give
rise to all lymphocytes
 Site of B cell differentiation or
immunocompetency
Thymus
 Site of T cell differentiation or
immunocompetency
Thymus
Secondary lymphatic organs

Lymph nodes
 Bean-shaped
 Numerous
 Regional lymph nodes:
• Cervical
• Axillary
• Inguinal, etc
 Hilus
 Afferent and efferent vessels
Secondary lymphatic organs

Microscopy
 Capsule and subcapsular sinus
 Trabecula
 Cortex
• Outer cortex (follicles)
• Germinal center containing
dividing B cells
• Deep cortex or paracortical area
• Contain T cells
Secondary lymphatic organs
 Medulla
• Medullary cords
• Medullary sinuses
• Contain macrophages and plasma
cells
Secondary lymphatic organs

Spleen
 Capsule
 White pulp
• Central artery
• Lymphocytes
 Red pulp
• Venous sinuses
• Reticular tissue
• Macrophages arranged I splenic
cords
Spleen
Lymphoid tissues

Tonsils
 One pharingeal
 Two palatines
 Two linguals
 Presence of germinal center
 Presence of crypts
Tonsils
The immune response



It is a systemic response
Destroys or neutralizes foreign substances
Characteristics of immune responses
 Memory
• Immunocompetent lymphocytes are
monospecific
 Specificity
 Ability to differentiate self from nonself
The immune response



Antigens
 Foreign proteins
 Polysaccharides
 Haptens
Lymphocytes
 Responsible for the immune
response
Autoimmunity
Organ, cells and cell interaction
of the immune response


Hemocytoblasts in the bone marrow
give rise to lymphocytes
Types of Lymphocytes:
 B - will stay in the bone marrow for
maturation (immunocompetence)
 T - will migrate to thymus for
maturation (immunocompetence)
 Natural Killers
Organ, cells and cell interaction
of the immune response

B and T cell will then leave bone
marrow and thymus, enter the blood
stream and travel to secondary
lymphatic organs
 Site for clonal selection
Organ, cells and cell interaction
of the immune response


B and T cell will bind to specific
antigens and then undergo clonal
multiplication
B cell may become
 Memory
 Plasma cell
 Humoral immunity
Organ, cells and cell interaction
of the immune response

T cell may become
 Memory
 Cytotoxic
 Helper
 Suppressor
 Cellular immunity
Antibodies and tests for their
presence

Characteristics of antibodies or
Immunoglobulins (Igs)
 Produced only by plasma cells
 They are plasma proteins
(gamaglobulins)
 Found in all body secretions
Antibodies and tests for their
presence


Classes of antibodies
 IgM, IgG, IgA, IgD, IgE
Structure of the immunoglobulins
 2 heavy chains
 2 light chains
Antibody